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Metastasis is a multistep process that is critically dependent on the interaction of metastasizing tumor cells with cells in the local microenvironment. Within this tumor stroma, vessel-associated pericytes and myofibroblasts share a number of traits, including the upregulated expression of the transmembrane receptor endosialin (CD248). Comparative experiments in wild-type and endosialin-deficient mice revealed that stromal endosialin does not affect primary tumor growth but strongly promotes spontaneous metastasis. Mechanistically, endosialin-expressing pericytes in the primary tumor facilitate distant site metastasis by promoting tumor cell intravasation in a cell contact-dependent manner, resulting in elevated numbers of circulating tumor cells. Corresponding to these preclinical experiments, in independent cohorts of primary human breast cancers, upregulated endosialin expression significantly correlates with increased metastasis and poorer patient survival. Together, the data demonstrate a critical role for endosialin-expressing primary tumor pericytes in mediating metastatic dissemination and identify endosialin as a promising therapeutic target in breast cancer. Cancer Res; 76(18); 5313-25. ©2016 AACR..

Stromal fibroblast recruitment to tumours and activation to a cancer-associated fibroblast (CAF) phenotype has been implicated in promoting primary tumour growth and progression to metastatic disease. However, the mechanisms underlying the tumour:fibroblast crosstalk that drive the intertumoural stromal heterogeneity remain poorly understood. Using in vivo models we identify Wnt7a as a key factor secreted exclusively by aggressive breast tumour cells, which induces CAF conversion. Functionally, this results in extracellular matrix remodelling to create a permissive environment for tumour cell invasion and promotion of distant metastasis. Mechanistically, Wnt7a-mediated fibroblast activation is not dependent on classical Wnt signalling. Instead, we demonstrate that Wnt7a potentiates TGFβ receptor signalling both in 3D in vitro and in vivo models, thus highlighting the interaction between two of the key signalling pathways in development and disease. Importantly, in clinical breast cancer cohorts, tumour cell Wnt7a expression correlates with a desmoplastic, poor-prognosis stroma and poor patient outcome..

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To interrogate the complex mechanisms involved in the later stages of cancer metastasis, we designed a functional in vivo RNA interference (RNAi) screen combined with next-generation sequencing. Using this approach, we identified the sialyltransferase ST6GalNAc2 as a novel breast cancer metastasis suppressor. Mechanistically, ST6GalNAc2 silencing alters the profile of O-glycans on the tumor cell surface, facilitating binding of the soluble lectin galectin-3. This then enhances tumor cell retention and emboli formation at metastatic sites leading to increased metastatic burden, events that can be completely blocked by galectin-3 inhibition. Critically, elevated ST6GALNAC2, but not galectin-3, expression in estrogen receptor-negative breast cancers significantly correlates with reduced frequency of metastatic events and improved survival. These data demonstrate that the prometastatic role of galectin-3 is regulated by its ability to bind to the tumor cell surface and highlight the potential of monitoring ST6GalNAc2 expression to stratify patients with breast cancer for treatment with galectin-3 inhibitors. .

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RET (rearranged during transfection) is a receptor tyrosine kinase overexpressed in a subset of oestrogen receptor (ER)-positive breast cancers whose expression is regulated by ER signalling. The article from the Hynes group has reported for the first time that RET expression can also be regulated by the inflammatory cytokine IL-6. Importantly, RET and IL-6 interact at a functional level to control migration and the metastatic potential of ER-positive breast cancer cells, in a process that is mediated by FAK activation. Further, targeting RET with receptor tyrosine kinase inhibitors was reported to be more effective than endocrine therapies in impairing metastatic dissemination in vivo, thereby indicating a level of RET regulation that is independent of ER. .

AIM: Nipple aspiration (NA) and duct lavage (DL) are modalities for obtaining breast duct fluid for biomarker analyses. The aim of this study was to assess the feasibility of obtaining serial NA and DL samples at consecutive patient visits for cytology assessment and the creation of a biobank. METHODS: Seventy eligible subjects were enroled at a single institution in the United Kingdom as part of an international multicentre study. Entry criteria were based on a 5-year Gail model risk of ≥2% or Claus score lifetime risk of ≥26%. Women underwent NA and DL in an outpatient clinic under local anaesthesia. RESULTS: The mean patient age was 48 (range 41-69)years. Sixty seven out of 70 women (96%) attended three consecutive 6 monthly visits and follow-up for 2 years. Three women withdrew due to intolerance of the DL procedure. 56/67 (83%) women produced NA fluid from at least one duct. 204/264 (77%) of ducts declared by NA were cannulated for DL. 170/204 (83%) produced DL samples with adequate cellularity. By the final visit 52/67 (78%) women produced DL, 28/52 (54%) of whom were premenopausal and 24/52 (46%) were postmenopausal. 50/52 women (96%) underwent repeated DL of 81 ducts on 3 consecutive visits. CONCLUSION: NA and DL are well tolerated for repeated assessment to obtain material for cytology and to create a biobank for future biomarker studies in women at high breast cancer risk..

DNA methylation of tumor-suppressor genes occurs early in the molecular transformation of precursor events to breast cancer and is therefore of interest to screening in high-risk women. The aim of this study was to use tumor-suppressor genes that have previously been shown to be cancer predictive in tissue to evaluate the potential of DNA methylation assays in cells from duct lavage (DL) fluid. The frequency of target gene DNA methylation in tissue and DL of cancer and healthy control patients was assessed, and an association of DNA methylation between different duct systems in the same breast was explored. The cancer and control groups were identified in the outpatient clinic when surgical treatment was finalized. Tumor, adjacent tissue and bilateral DL samples for comparative DNA methylation studies were obtained during surgery from women with cancer. In the healthy control group, samples of tissue and DL were collected. Reverse transcriptase methylation-specific PCR was conducted on modified DNA purified from 42 cancer biopsies, 41 benign excision cavity biopsies (internal control), 29 benign biopsies (external control), and 119 DL specimens. A validated panel of cancer predictive genes was analyzed in the study bank of tissue and DL samples from cancer and healthy patients. The sensitivity of DNA methylation in DL samples compared with matched cancer tissue was highest for SCGB3A1 (90 %), CDH13 (91 %), and RARB (83 %). The genetic algorithm selected RASSF1A, RARB, and IGFBP7 as the optimum predictor set for detecting DNA methylation in cancer tissue. The optimum area under the ROC curve for DNA methylation in cancer compared with internal control healthy tissue from excision margins was 0.84. The area under the ROC curve for DNA methylation in cancer DL compared with contralateral benign DL was 0.76. DL cytology was not a helpful predictor of breast cancer. This study shows that relative patterns of tumor-suppressor gene hypermethylation in breast cancer tissue are significantly reflected in the DL from the cancer affected breast. Using DL, nonconcordant patterns of DNA methylation between different duct systems confer independent oncologic potential for distinct breast lobes. The approach of DNA methylation in DL may be substantiated by a larger trial of breast cancer biomarkers..

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It has been proposed that epithelial-mesenchymal transition (EMT) in mammary epithelial cells and breast cancer cells generates stem cell features, and that the presence of EMT characteristics in claudin-low breast tumors reveals their origin in basal stem cells. It remains to be determined, however, whether EMT is an inherent property of normal basal stem cells, and if the presence of a mesenchymal-like phenotype is required for the maintenance of all their stem cell properties. We used nontumorigenic basal cell lines as models of normal stem cells/progenitors and demonstrate that these cell lines contain an epithelial subpopulation ("EpCAM+," epithelial cell adhesion molecule positive [EpCAM(pos)]/CD49f(high)) that spontaneously generates mesenchymal-like cells ("Fibros," EpCAM(neg)/CD49f(med/low)) through EMT. Importantly, stem cell/progenitor properties such as regenerative potential, high aldehyde dehydrogenase 1 activity, and formation of three-dimensional acini-like structures predominantly reside within EpCAM+ cells, while Fibros exhibit invasive behavior and mammosphere-forming ability. A gene expression profiling meta-analysis established that EpCAM+ cells show a luminal progenitor-like expression pattern, while Fibros most closely resemble stromal fibroblasts but not stem cells. Moreover, Fibros exhibit partial myoepithelial traits and strong similarities with claudin-low breast cancer cells. Finally, we demonstrate that Slug and Zeb1 EMT-inducers control the progenitor and mesenchymal-like phenotype in EpCAM+ cells and Fibros, respectively, by inhibiting luminal differentiation. In conclusion, nontumorigenic basal cell lines have intrinsic capacity for EMT, but a mesenchymal-like phenotype does not correlate with the acquisition of global stem cell/progenitor features. Based on our findings, we propose that EMT in normal basal cells and claudin-low breast cancers reflects aberrant/incomplete myoepithelial differentiation..

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The concept of an intraductal approach to evaluate the breast microenvironment assumes direct access to the cancer-containing duct. Central duct access to the cancer-affected lobe is essential if cytology or cell markers are to be useful indicators of pre-malignant change. Access to the cancer-bearing lobe would be less important if field change effects of malignant change were predominantly supra-lobar. The aim of this study was to determine how often duct lavage fluid drains the breast cancer-affected segment. 58 patients undergoing mastectomy for breast cancer were recruited among which 47 had at least one fluid-yielding duct. Following duct lavage, fluid-yielding ducts were perfused ex vivo with Polyurethane Elastomer (PU4ii) resin. Specimens were sliced sagittally, and the extent of resin perfusion and anatomical relationship to the cancer-affected segment was recorded. Computed tomography (CT) scanning was performed on selected mastectomies before cut-up for a feasibility study of 3D duct reconstruction. The median number of fluid-yielding ducts cannulated per cancer-affected breast was 2 (range 1-4). 35/47 (74%) mastectomy specimens were successfully cannulated for resin perfusion. 29/35 (83%) showed tracing of the cancer-affected duct system, 6/35 resin perfusions traced duct systems unaffected by cancer and 12/35 perfusions extravasated. The proportion of sagittal breast slices perfused by resin was 13-68% (median 43%). Volume rendering CT showed it is feasible to produce a simulated image of the perfused ducts. Duct access to the cancer-containing segment is feasible in the majority of patients. Fluid-yielding ducts proportionately drain a significant volume of the breast. Large symptomatic cancers may cause obstruction with distal collapse. Further quantitative study of breast perfusion CT scans may be helpful for estimating the volume fraction of breast tissue perfused by fluid-yielding ducts. The intraductal approach is a valid concept for biomarker assessment of cancer-containing breast segments..

Cancer is caused by mutations in oncogenes and tumor suppressor genes, resulting in the deregulation of processes fundamental to the normal behavior of cells. The identification and characterization of oncogenes and tumor suppressors has led to new treatment strategies that have significantly improved cancer outcome. The advent of next generation sequencing has allowed the elucidation of the fine structure of cancer genomes, however, the identification of pathogenic changes is complicated by the inherent genomic instability of cancer cells. Therefore, functional approaches for the identification of novel genes involved in the initiation and development of tumors are critical. Here we report the first whole human genome in vivo RNA interference screen to identify functionally important tumor suppressor genes. Using our novel approach, we identify previously validated tumor suppressor genes including TP53 and MNT, as well as several novel candidate tumor suppressor genes including leukemia inhibitory factor receptor (LIFR). We show that LIFR is a key novel tumor suppressor, whose deregulation may drive the transformation of a significant proportion of human breast cancers. These results demonstrate the power of genome wide in vivo RNAi screens as a method for identifying novel genes regulating tumorigenesis..

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Blood vessel networks form in a 2-step process of sprouting angiogenesis followed by selective branch regression and stabilization of remaining vessels. Pericytes are known to function in stabilizing blood vessels, but their role in vascular sprouting and selective vessel regression is poorly understood. The endosialin (CD248) receptor is expressed by pericytes associated with newly forming but not stable quiescent vessels. In the present study, we used the Endosialin(-/-) mouse as a means to uncover novel roles for pericytes during the process of vascular network formation. We demonstrate in a postnatal retina model that Endosialin(-/-) mice have normal vascular sprouting but are defective in selective vessel regression, leading to increased vessel density. Examination of the Endosialin(-/-) mouse tumor vasculature revealed an equivalent phenotype, indicating that pericytes perform a hitherto unidentified function to promote vessel destabilization and regression in vivo in both physiologic and pathologic angiogenesis. Mechanistically, Endosialin(-/-) mice have no defect in pericyte recruitment. Rather, endosialin binding to an endothelial associated, but not a pericyte associated, basement membrane component induces endothelial cell apoptosis and detachment. The results of the present study advance our understanding of pericyte biology and pericyte/endothelial cell cooperation during vascular patterning and have implications for the design of both pro- and antiangiogenic therapies..

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Tumor growth factor-β (TGF-β) signaling in cancer has been implicated in growth suppression of early lesions and enhancing tumor cell invasion and metastasis. However, the cellular mechanisms that determine this signaling output in individual tumors are still largely unknown. In endothelial cells, TGF-β signaling is modulated by the TGF-β co-receptor endoglin (CD105). Here we demonstrate that endoglin is expressed in a subset of invasive breast cancers and cell lines and is subject to epigenetic silencing by gene methylation. Endoglin downregulation in non-tumorigenic MCF10A breast cells leads to the formation of abnormal acini in 3D culture, but does not promote cell migration or transformation. In contrast, in the presence of activated ErbB2, endoglin downregulation in MCF10A cells leads to enhanced invasion into a 3D matrix. Consistent with these data, ectopic expression of endoglin in MDA-MB-231 cells blocks TGF-β-enhanced cell motility and invasion and reduces lung colonization in an in vivo metastasis model. Unlike endothelial cells, endoglin does not modulate Smad-mediated TGF-β signaling in breast cells but attenuates the cytoskeletal remodeling to impair cell migration and invasion. Importantly, in a large cohort of invasive breast cancers, lack of endoglin expression in the tumor cell compartment correlates with ENG gene methylation and poor clinical outcome..

Recent studies demonstrate that the receptor tyrosine kinase RET is overexpressed in a subset of ER-positive breast cancers and that crosstalk between RET and ER is important in responses to endocrine therapy. The development of small molecular inhibitors that target RET allows the opportunity to consider combination therapies as a strategy to improve response to treatment and to prevent and combat endocrine resistance. This review discusses: (i) the current knowledge about RET, its co-receptors and ligands in breast cancer; (ii) the breast cancer clinical trials involving agents that target RET; and (iii) the challenges that remain in terms of specificity of available inhibitors and in understanding the complex molecular mechanisms that underlie the resistance to endocrine therapy..

BACKGROUND: The majority of benign and malignant lesions of the breast are thought to arise from the epithelium of the terminal duct-lobular unit (TDLU). Although modern mammography, ultrasound, and MRI have improved diagnosis, a final pathological diagnosis currently relies on percutaneous methods of sampling breast lesions. The advantage of mammary ductoscopy (MD) is that it is possible to gain direct access to the ductal system via the nipple. Direct visualization of the duct epithelium allows the operator to precisely locate intraductal lesions, enabling accurate tissue sampling and providing guidance to the surgeon during excision. The intraductal approach may also have a role in screening individuals who are at high risk of breast cancer. Finally, in spontaneous nipple discharge (SND), as biopsy instruments improve and intraductal therapeutics, such as intraductal excision and laser ablation, become a possibility, normal or benign ductoscopic findings may help minimize surgery in selected patients. As MD technology is rapidly advancing, a comprehensive review of current practice will be a valuable guide for clinicians involved in the management of breast disease. METHODS: This is a review of current ductoscopic practice based on an exhaustive literature search of Pubmed, Google Scholar, and conference proceedings. The search terms "ductoscopy", "duct endoscopy", "mammary", "breast," and "intraductal" were used. RESULTS/CONCLUSIONS: Duct endoscopes have become smaller in diameter with working channels and improved optical definition. Currently, the role of MD is best defined in the management of SND facilitating targeted surgical excision, potentially avoiding unnecessary surgery, and limiting the extent of surgical resection for benign disease. The role of MD in breast-cancer screening and breast conservation surgery has yet to be fully defined. Few prospective randomized trials exist in the literature, and these would be crucial to validate current opinion, not only in the benign setting but also in breast oncologic surgery..

CD248 (endosialin) is a transmembrane glycoprotein that is dynamically expressed on pericytes and fibroblasts during tissue development, tumour neovascularization and inflammation. Its role in tissue remodelling is associated with increased stromal cell proliferation and migration. We show that CD248 is also uniquely expressed by human, but not mouse (C57BL/6), CD8(+) naive T cells. CD248 is found only on CD8(+) CCR7(+) CD11a(low) naive T cells and on CD8 single-positive T cells in the thymus. Transfection of the CD248 negative T-cell line MOLT-4 with CD248 cDNA surprisingly reduced cell proliferation. Knock-down of CD248 on naive CD8 T cells increased cell proliferation. These data demonstrate opposing functions for CD248 on haematopoietic (CD8(+)) versus stromal cells and suggests that CD248 helps to maintain naive CD8(+) human T cells in a quiescent state..

Stromal fibroblasts are the primary cells of the kidney that produce fibrotic matrix. CD248 is a stromal marker expressed on fibroblasts and pericytes within the human kidney. Here, we tested whether CD248 expression in the kidney colocalizes with fibrosis and if it is associated with known determinants of chronic kidney disease (CKD). CD248 expression was located and quantified in situ by immunohistochemistry in kidney biopsies from 93 patients with IgA nephropathy and compared with 22 archived biopsies encompassing normal kidney tissue as control. In normal kidney tissue, CD248 was expressed by resident pericytes, stromal fibroblasts, and was upregulated in human CKD. The expression was linked to known determinants of renal progression. This relationship was maintained in a multivariate analysis with CD248 expression linked to renal survival. CD248 was expressed by a population of α-smooth muscle actin (SMA)(+) myofibroblasts and α-SMA(-) stromal cells but not expressed on CD45(+) leukocytes. Thus, CD248 defines a subset of stromal cells, including but not limited to some myofibroblasts, linked to albuminuria and tubulointerstitial damage during tissue remodeling in CKD..

Whether RET is able to directly phosphorylate and activate downstream targets independently of the binding of proteins that contain Src homology 2 or phosphotyrosine binding domains and whether mechanisms in trans by cytoplasmic kinases can modulate RET function and signaling remain largely unexplored. In this study, oligopeptide arrays were used to screen substrates directly phosphorylated by purified recombinant wild-type and oncogenic RET kinase domain in the presence or absence of small molecule inhibitors. The results of the peptide array were validated by enzyme kinetics, in vitro kinase, and cell-based experiments. The identification of focal adhesion kinase (FAK) as a direct substrate for RET kinase revealed (i) a RET-FAK transactivation mechanism consisting of direct phosphorylation of FAK Tyr-576/577 by RET and a reciprocal phosphorylation of RET by FAK, which crucially is able to rescue the kinase-impaired RET K758M mutant and (ii) that FAK binds RET via its FERM domain. Interestingly, this interaction is abolished upon RET phosphorylation, indicating that RET binding to the FERM domain of FAK is a priming step for RET-FAK transactivation. Finally, our data indicate that FAK inhibitors could be used as potential therapeutic agents for patients with multiple endocrine neoplasia type 2 tumors because both, treatment with the FAK kinase inhibitor NVP-TAE226 and FAK down-regulation by siRNA reduced RET phosphorylation and signaling as well as the proliferation and survival of tumor and transfected cell lines expressing oncogenic RET..

Epithelial to mesenchymal transition (EMT) is an essential process in embryonic development and is aberrantly induced in many disease settings. Work carried out by Chonghui Cheng's laboratory addressed the involvement of alternative RNA splicing in EMT and its link to tumour progression. They describe a switch in CD44 expression from variant isoform(s) to the standard isoform and showed, for the first time, that this is required for normal epithelial cells to undergo EMT. In addition, they link expression of the CD44 standard isoform with high-grade breast cancer and to activation of the phosphoinositide 3-kinase/Akt pathway and apoptosis resistance in a mouse model of recurrent disease..

RNA interference (RNAi) screening is a state-of-the-art technology that enables the dissection of biological processes and disease-related phenotypes. The commercial availability of genome-wide, short hairpin RNA (shRNA) libraries has fueled interest in this area but the generation and analysis of these complex data remain a challenge. Here, we describe complete experimental protocols and novel open source computational methodologies, shALIGN and shRNAseq, that allow RNAi screens to be rapidly deconvoluted using next generation sequencing. Our computational pipeline offers efficient screen analysis and the flexibility and scalability to quickly incorporate future developments in shRNA library technology..

BACKGROUND: Gene expression profiling of the transcriptional response of human dermal fibroblasts to in vitro radiation has shown promise as a predictive test of radiosensitivity. This study tested if treatment with the radiomimetic drug bleomycin sulphate could be used to differentiate radiation sensitive patients and controls in patients who had previously received radiotherapy for early breast cancer. FINDINGS: Eight patients who developed marked late radiation change assessed by photographic breast appearance and 8 matched patients without any change were selected from women entered in a prospective randomised trial of breast radiotherapy fractionation. Gene expression profiling of primary skin fibroblasts exposed in vitro to bleomycin sulphate and mock treated fibroblast controls was performed. 973 genes were up-regulated and 923 down-regulated in bleomycin sulphate treated compared to mock treated control fibroblasts. Gene ontology analysis revealed enriched groups were cellular localisation, apoptosis, cell cycle and DNA damage response for the deregulated genes. No transcriptional differences were identified between fibroblasts from radiation sensitive cases and control patients; subgroup analysis using cases exhibiting severe radiation sensitivity or with high risk alleles present in TGF β1 also showed no difference. CONCLUSIONS: The transcriptional response of human dermal fibroblasts to bleomycin sulphate has been characterised. No differences between clinically radiation sensitive and control patients were detected using this approach..

Multiple immunofluorescent labeling of formalin-fixed paraffin-embedded (FFPE) tissue is not a routinely used method. At least in part, this is due to the perception that the innate autofluorescence of the FFPE material forbids the use of immunofluorescent labeling. As a result, immunohistochemical (immunoperoxidase) staining of FFPE material or cryosectioning methods is used instead. In this chapter, we describe a robust optimized method for high-resolution immunofluorescence labeling of FFPE tissue that involves the combination of antigen retrieval, indirect immunofluorescence, and confocal laser scanning microscopy. Once such samples have been prepared and imaged by confocal microscopy, they can be stored at -20°C for extensive periods (>250 days) and reexamined with minimal loss of quality. As a consequence, this method has the potential to open up the large archival sample collections to multiple immunofluorescent investigations..

Overexpression and alternative splicing of CD44 have been implicated in tumour progression. Here we describe the identification of a high level amplification of human 11p13, encompassing the CD44 gene, in primary breast cancers and cell lines and test whether CD44 acts as the driver of this amplicon. aCGH analysis revealed 11p13 amplification in 3% (3/100) of primary breast carcinomas and in two cell lines. The minimal region of amplification was 34.38-37.62 Mb. Amplification was confirmed by dual-colour FISH in these cell lines and further validated by CISH in an independent tumour cohort. CD44 expression in primary breast cancers was significantly associated with features of basal-like breast cancer. Detection of CD44 expression in breast cancer cell lines confirmed moderate to high expression in basal-like cell lines and minimal expression in luminal cell lines. In both, primary breast cancers and cell lines, 11p13 amplification was associated with high levels of CD44 mRNA expression. CD44 alternative splicing was detected in four of nine cell lines and in tumour samples, irrespective of the amplification status. RNAi mediated knock down of CD44 failed to reveal an increased dependence on CD44 expression for proliferation or survival in amplified cell lines. Given that expression of CD44 is not an absolute requirement for the survival of cells harbouring CD44 gene amplification, CD44 is unlikely to be a driver of the 11p13 amplicon..

CD248 is a cell surface receptor that specifically identifies fibroblasts and pericytes during development and in association with cancer and inflammation. However, its function is poorly defined and its role in lymphoid organs not studied. Here, we used (4-hydroxy-3-nitrophenyl)acetyl chicken gamma-globulin immunisation and mice lacking CD248 to study whether CD248 modulates popliteal LN (pLN) expansion and subsequent immune responses. We have found that CD248 is required for complete pLN expansion but not for co-ordination of B and T cell compartmentalisation or antibody production following (4-hydroxy-3-nitrophenyl)acetyl chicken gamma-globulin immunisation. In vitro, we show that CD248 expression in human MG63 stromal cells and mouse embryonic fibroblasts leads to a pro-proliferative and pro-migratory phenotype. This correlates with a proliferating CD248(+) population observed in vivo during pLN expansion. Taken together, these data highlight a role for CD248 in secondary lymphoid organ remodelling during adaptive immune responses..

Endocrine therapy is the main therapeutic option for patients with estrogen receptor (ERalpha)-positive breast cancer. Resistance to this treatment is often associated with estrogen-independent activation of ERalpha. In this study, we show that in ERalpha-positive breast cancer cells, activation of the receptor tyrosine kinase RET (REarranged during Transfection) by its ligand GDNF results in increased ERalpha phosphorylation on Ser118 and Ser167 and estrogen-independent activation of ERalpha transcriptional activity. Further, we identify mTOR as a key component in this downstream signaling pathway. In tamoxifen response experiments, RET downregulation resulted in 6.2-fold increase in sensitivity of MCF7 cells to antiproliferative effects of tamoxifen, whereas GDNF stimulation had a protective effect against the drug. In tamoxifen-resistant (TAM(R)-1) MCF7 cells, targeting RET restored tamoxifen sensitivity. Finally, examination of two independent tissue microarrays of primary human breast cancers revealed that expression of RET protein was significantly associated with ERalpha-positive tumors and that in primary tumors from patients who subsequently developed invasive recurrence after adjuvant tamoxifen treatment, there was a twofold increase in the number of RET-positive tumors. Together these findings identify RET as a potentially important therapeutic target in ERalpha-positive breast cancers and in particular in tamoxifen-resistant tumors..

BACKGROUND: Glioblastoma multiforme (GBM, WHO grade IV) is the most common and most malignant of astrocytic brain tumors, and is associated with rapid invasion into neighboring tissue. In other tumor types it is well established that such invasion involves a complex interaction between tumor cells and locally produced extracellular matrix. In GBMs, surprisingly little is known about the associated matrix components, in particular the fibrillar proteins such as collagens that are known to play a key role in the invasion of other tumor types. METHODOLOGY/PRINCIPAL FINDINGS: In this study we have used both the Masson's trichrome staining and a high resolution multiple immunofluorescence labeling method to demonstrate that intratumoral fibrillar collagens are an integral part of the extracellular matrix in a subset of GBMs. Correlated with this collagen deposition we observed high level expression of the collagen-binding receptor Endo180 (CD280) in the tumor cells. Further, interrogation of multiple expression array datasets identified Endo180 as one of the most highly upregulated transcripts in grade IV GBMs compared to grade III gliomas. Using promoter analysis studies we show that this increased expression is, in part, mediated via TGF-beta signaling. Functionally, we demonstrate that Endo180 serves as the major collagen internalization receptor in GBM cell lines and provide the first evidence that this activity is critical for the invasion of GBM cells through fibrillar collagen matrices. CONCLUSIONS/SIGNIFICANCE: This study demonstrates, for the first time, that fibrillar collagens are extensively deposited in GBMs and that the collagen internalization receptor Endo180 is both highly expressed in these tumors and that it serves to mediate the invasion of tumor cells through collagen-containing matrices. Together these data provide important insights into the mechanism of GBM invasion and identify Endo180 as a potential target to limit matrix turnover by glioma cells and thereby restrict tumor progression..

Hematopoiesis is a carefully controlled process that is regulated by complex networks of transcription factors that are, in part, controlled by signals resulting from ligand binding to cell-surface receptors. To further understand hematopoiesis, we have compared gene expression profiles of human erythroblasts, megakaryocytes, B cells, cytotoxic and helper T cells, natural killer cells, granulocytes, and monocytes using whole genome microarrays. A bioinformatics analysis of these data was performed focusing on transcription factors, immunoglobulin superfamily members, and lineage-specific transcripts. We observed that the numbers of lineage-specific genes varies by 2 orders of magnitude, ranging from 5 for cytotoxic T cells to 878 for granulocytes. In addition, we have identified novel coexpression patterns for key transcription factors involved in hematopoiesis (eg, GATA3-GFI1 and GATA2-KLF1). This study represents the most comprehensive analysis of gene expression in hematopoietic cells to date and has identified genes that play key roles in lineage commitment and cell function. The data, which are freely accessible, will be invaluable for future studies on hematopoiesis and the role of specific genes and will also aid the understanding of the recent genome-wide association studies..

The pathogenesis of late normal tissue fibrosis after high-dose ionizing radiation involves multiple cell types and signalling pathways but is not well understood. To identify the molecular changes occurring after radiotherapy, paired normal tissue samples were collected from the non-irradiated breast and from the treated breast of women who had undergone curative radiotherapy for early breast cancer months or years previously. As radiation may induce distinct transcriptional changes in the different components of the breast, laser capture microdissection and gene expression microarray profiling were performed separately for epithelial and stromal components and selected genes were validated using immunohistochemistry. In the epithelial compartment, a reduction of KIT (c-Kit; CD117) and a reciprocal increase in ESR1 (oestrogen receptor-alpha, ERalpha) mRNA and protein levels were seen in irradiated compared to non-irradiated samples. In the stromal compartment, extracellular matrix genes including FN1 (fibronectin 1) and CTGF (connective tissue growth factor; CCN2) were increased. Further investigation revealed that c-Kit and ERalpha were expressed in distinct subpopulations of luminal epithelial cells. Interlobular c-Kit-positive mast cells were also increased in irradiated cases not showing features of post-radiation atrophy. Pathway analysis revealed 'cancer, reproductive system disease and tumour morphology' as the most significantly enriched network in the epithelial compartment, whereas in the stromal component, a significant enrichment for 'connective tissue disorders, dermatological diseases and conditions, genetic disorder' and 'cancer, tumour morphology, infection mechanism' networks was observed. These data identify previously unreported changes in the epithelial compartment and show altered expression of genes implicated in late normal tissue injury in the stromal compartment of normal breast tissue. The findings are relevant to both fibrosis and atrophy occurring after radiotherapy for early breast cancer..

We herein describe the positional identification of a 2-bp deletion in the open reading frame of the MRC2 receptor causing the recessive Crooked Tail Syndrome in cattle. The resulting frame-shift reveals a premature stop codon that causes nonsense-mediated decay of the mutant messenger RNA, and the virtual absence of functional Endo180 protein in affected animals. Cases exhibit skeletal anomalies thought to result from impaired extracellular matrix remodeling during ossification, and as of yet unexplained muscular symptoms. We demonstrate that carrier status is very significantly associated with desired characteristics in the general population, including enhanced muscular development, and that the resulting heterozygote advantage caused a selective sweep which explains the unexpectedly high frequency (25%) of carriers in the Belgian Blue Cattle Breed..

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The molecular interactions leading to organised, controlled extracellular matrix degradation are of central importance during growth, development and tissue repair, and when deregulated contribute to disease processes including cancer cell invasion. There are two major pathways for collagen degradation: one dependent on secreted and membrane-bound collagenases, the other on receptor-mediated collagen internalisation and intracellular processing. Despite the established importance of both pathways, the functional interaction between them is largely unknown. We demonstrate here, that the collagen internalisation receptor Endo180 (also known as CD280, uPARAP, MRC2) is a novel regulator of membrane-bound matrix metalloproteinase (MT1-MMP) activity, MT1-MMP-dependent MMP-2 activation and urokinase plasminogen activator (uPA) activity. We show close correlation between Endo180 expression, collagen accumulation and regulation of MT1-MMP cell-surface localisation and activity. We directly demonstrate, using collagen inhibition studies and non-collagen-binding mutants of Endo180, that the molecular mechanism underlying this regulation is the ability of Endo180 to bind and/or internalise collagens, rather than by acting as an interaction partner for pro-uPA and its receptor uPAR. These studies strongly support a functional interaction between two distinct collagen degradation pathways, define a novel mechanism regulating MT1-MMP activity and might have important implications for organised collagen clearance in the pericellular environment..

Gliomas are the most frequent primary tumors of the central nervous system in adults. The most prevalent and aggressive subclass of these is glioblastoma multiforme, which is characterized by massive neovascularization. Endosialin (CD248) has generated interest as a target for antiangiogenic therapy following reports that its expression is upregulated on angiogenic endothelial cells. We demonstrate here that endosialin is not expressed in normal human adult brain but is strongly upregulated in the angiogenic vasculature of all high-grade glioma specimens examined. However, by taking advantage of a technique which allows for multiple fluorescent labeling of formalin-fixed paraffin-embedded archival sections, we demonstrate unambiguously that endosialin is not expressed by the glioma endothelial cells but on closely associated perivascular cells. With increasing awareness that targeting pericytes is an attractive adjunct in antiangiogenic therapy, this finding has important implications for understanding the molecular mechanisms regulating angiogenesis in these highly vascularized tumors..

BACKGROUND: Investigating the expression of candidate genes in tissue samples usually involves either immunohistochemical labelling of formalin-fixed paraffin-embedded (FFPE) sections or immunofluorescence labelling of cryosections. Although both of these methods provide essential data, both have important limitations as research tools. Consequently, there is a demand in the research community to be able to perform routine, high quality immunofluorescence labelling of FFPE tissues. RESULTS: We present here a robust optimised method for high resolution immunofluorescence labelling of FFPE tissues, which involves the combination of antigen retrieval, indirect immunofluorescence and confocal laser scanning microscopy. We demonstrate the utility of this method with examples of immunofluorescence labelling of human kidney, human breast and a tissue microarray of invasive human breast cancers. Finally, we demonstrate that stained slides can be stored in the short term at 4 degrees C or in the longer term at -20 degrees C prior to images being collected. This approach has the potential to unlock a large in vivo database for immunofluorescence investigations and has the major advantages over immunohistochemistry in that it provides higher resolution imaging of antigen localization and the ability to label multiple antigens simultaneously. CONCLUSION: This method provides a link between the cell biology and pathology communities. For the cell biologist, it will enable them to utilise the vast archive of pathology specimens to advance their in vitro data into in vivo samples, in particular archival material and tissue microarrays. For the pathologist, it will enable them to utilise multiple antibodies on a single section to characterise particular cell populations or to test multiple biomarkers in limited samples and define with greater accuracy cellular heterogeneity in tissue samples..

Endosialin has been assigned the alternate name of tumour endothelial marker 1 (TEM1) due to its identification as a highly upregulated gene transcript in tumour endothelium compared to normal endothelium. As a consequence there is interest in endosialin as a potential therapeutic target in cancer treatment. However, there are conflicting reports over the nature of vascular expression in tumours with some evidence that endosialin is expressed on perivascular pericytes rather than the endothelial cells themselves. To address this, we have analysed the expression of endosialin in mouse embryos, newborn pups and adults. In the embryo endosialin is predominantly expressed on stromal fibroblasts throughout the mesenchyme but expression is also observed on the developing vasculature. When analysed by confocal microscopy endosialin on vessels does not colocalise with endothelial cells expressing CD31. Rather, endosialin is restricted to closely associated perivascular cells that also express the pericyte marker NG2. Finally, the fibroblast and pericyte expression of endosialin changes dynamically during development and becomes highly restricted in adult mouse tissues. This evolving picture of endosialin expression in sites of active tissue remodelling and neovascularisation has implications in tumour growth, angiogenesis and metastasis..

The role of estrogen in promoting mammary stem cell proliferation remains controversial. It is unclear if estrogen receptor (ER)-expressing cells have stem/progenitor activity themselves or if they act in a paracrine fashion to stimulate stem cell proliferation. We have used flow cytometry to prospectively isolate mouse mammary ER-expressing epithelial cells and shown, using analysis of gene expression patterns and cell type-specific markers, that they form a distinct luminal epithelial cell subpopulation that expresses not only the ER but also the progesterone and prolactin receptors. Furthermore, we have used an in vivo functional transplantation assay to directly demonstrate that the ER-expressing luminal epithelial subpopulation contains little in vivo stem cell activity. Rather, the mammary stem cell activity is found within the basal mammary epithelial cell population. Therefore, ER-expressing cells of the mammary epithelium are distinct from the mammary stem cell population, and the effects of estrogen on mammary stem cells are likely to be mediated indirectly. These results are important for our understanding of cellular responses to hormonal stimulation in the normal breast and in breast cancer..

PURPOSE: In a previous screen using a signal-trap library, we identified a number of secreted proteins up-regulated in primary tumor cells isolated from invasive breast cancers. The purpose of this study was to assess the expression of these genes in human invasive breast tumors and to determine the significance of their expression for prognosis in breast cancer. EXPERIMENTAL DESIGN: A tissue microarray containing 245 invasive breast tumors from women treated with curative surgery followed by anthracycline-based chemotherapy and hormone therapy for the estrogen receptor (ER)-positive tumors was screened by in situ hybridization with probes against thrombospondin 3 (TSP3), insulin-like growth factor binding protein 7 (IGFBP7), tumor rejection antigen 1 (TRA1), stanniocalcin 2 (STC2), and netrin 4 (NTN4). Correlations between categorical variables were done using the chi(2) test and Fisher's exact test. Cumulative survival probabilities were calculated using the Kaplan-Meier method and multivariate survival analysis was done with Cox hazard model. A series of breast cancers were also stained with NTN4 antibodies. RESULTS: All five genes examined were expressed in invasive breast tumor cells. NTN4 protein expression was also confirmed by immunohistochemistry. Together, these data validate the design and screening of the signal-trap library. Univariate survival analysis revealed that expressions of TRA1, STC2, and NTN4 are correlated with longer disease-free survival and that TRA1 and NTN4 are associated with longer overall survival. Multivariate analysis showed that NTN4 is an independent prognostic factor of overall survival. CONCLUSIONS: This article describes the identification of three secreted proteins, NTN4, TRA1, and STC2, as potential novel prognostic markers in breast cancer..

Tumor cell invasion into the surrounding stroma requires increased cell motility and extensive remodeling of the extracellular matrix. Endo180 (CD280, MRC2, urokinase-type plasminogen activator receptor-associated protein) is a recycling endocytic receptor that functions in both these cellular activities by promoting cell migration and uptake of collagens for intracellular degradation. In the normal breast, Endo180 is predominantly expressed by stromal fibroblasts. The contrary observation that Endo180 is expressed on epithelial tumor cell lines that display a high invasive capacity suggested that up-regulation of this receptor may be an associated and functional component in the acquisition of a more aggressive phenotype by tumor cells in vivo. Here, we show that high levels of Endo180 are found in a subset of basal-like breast cancers and that this expression is an independent prognostic marker for shorter disease-free survival. Two potential mechanisms for Endo180 up-regulation were uncovered. First, it was shown that Endo180 can be transcriptionally up-regulated in vitro following transforming growth factor-beta treatment of breast cancer cells. Second, a proportion of Endo180(+) tumors were shown to have Endo180 gene copy number gains and amplifications. To investigate the functional consequence of Endo180 up-regulation, MCF7 cells transfected with Endo180 were inoculated into immunocompromised mice. Expression of wild-type Endo180, but not an internalization-defective Endo180 mutant, resulted in enhanced tumor growth together with a reduction in tumor collagen content. Together, these data argue that elevated expression of this receptor in tumor cells could have important consequences in subsets of basal-like carcinomas for which there is a current lack of effective treatment..

The precise role of STAT3 Ser(727) phosphorylation in RET-mediated cell transformation and oncogenesis is not well understood. In this study, we have shown that familial medullary thyroid carcinoma (FMTC) mutants RET(Y791F) and RET(S891A) induced, in addition to Tyr(705) phosphorylation, constitutive STAT3 Ser(727) phosphorylation. Using inhibitors and dominant negative constructs, we have demonstrated that RET(Y791F) and RET(S891A) induce STAT3 Ser(727) phosphorylation via a canonical Ras/ERK1/2 pathway and that integration of the Ras/ERK1/2/ELK-1 and STAT3 pathways was required for up-regulation of the c-fos promoter by FMTC-RET. Moreover, inhibition of ERK1/2 had a more severe effect on cell proliferation and cell phenotype in HEK293 cells expressing RET(S891A) compared with control and RET(WT)-transfected cells. The transforming activity of RET(Y791F) and RET(S891A) in NIH-3T3 cells was also inhibited by U0126, indicating a role of the ERK1/2 pathway in RET-mediated transformation. To investigate the biological significance of Ras/ERK1/2-induced STAT3 Ser(727) phosphorylation for cell proliferation and transformation, N-Ras-transformed NIH-3T3 cells were employed. These cells displayed elevated levels of activated ERK1/2 and Ser(727)-phosphorylated STAT3, which were inhibited by treatment with U0126. Importantly, overexpression of STAT3, in which the Ser(727) was mutated into Ala (STAT3(S727A)), rescued the transformed phenotype of N-Ras-transformed cells. Immunohistochemistry in tumor samples from FMTC patients showed strong nuclear staining of phosphorylated ERK1/2 and Ser(727) STAT3. These data show that FMTC-RET mutants activate a Ras/ERK1/2/STAT3 Ser(727) pathway, which plays an important role in cell mitogenicity and transformation..

Germ line missense mutations in the RET (rearranged during transfection) oncogene are the cause of multiple endocrine neoplasia, type 2 (MEN2), but at present surgery is the only treatment available for MEN2 patients. In this study, the ability of Sorafenib (BAY 43-9006) to act as a RET inhibitor was investigated. Sorafenib inhibited the activity of purified recombinant kinase domain of wild type RET and RET(V804M) with IC(50) values of 5.9 and 7.9 nm, respectively. Interestingly, these values were 6-7-fold lower than the IC(50) for the inhibition of B-RAF(V600E). In cell-based assays, Sorafenib inhibited the kinase activity and signaling of wild type and oncogenic RET in MEN2 tumor and established cell lines at a concentration between 15 and 150 nm. In contrast, inhibition of oncogenic B-RAF- or epidermal growth factor-induced ERK1/2 phosphorylation required micromolar concentrations of Sorafenib demonstrating the high specificity of this drug in targeting RET. Moreover, prolonged exposure to Sorafenib resulted in inhibition of cell proliferation and RET protein degradation. Using lysosomal and proteasomal inhibitors, we demonstrate that Sorafenib induces RET lysosomal degradation independent of proteasomal targeting. Furthermore, we provide a structural model of the Sorafenib.RET complex in which Sorafenib binds to and induces the DFG(out) conformation of the RET kinase domain. These results strengthen the argument that Sorafenib may be effective in the treatment of MEN2 patients. In addition, because inhibition of RET is not impaired by mutation of the Val(804) gatekeeper residue, MEN2 tumors may be less susceptible to acquired Sorafenib resistance..

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A proteomic approach to nipple aspiration fluid (NAF) has been used in a number of studies comparing women with breast cancer and healthy women. However, to make useful comparisons between women with breast cancer and healthy women it is necessary to establish whether there is physiological variation in the proteomic profiles of NAF. The purpose of this study was, for the first time, to examine how the proteomic profile of NAF using surface-enhanced laser desorption ionisation time-of-flight mass spectrometry varies across the menstrual cycle in healthy pre-menopausal women. Twelve women were recruited and nipple aspiration was carried out weekly from both breasts of each subject for two menstrual cycles. Matching serum samples for luteinising hormone, follicle stimulating hormone and oestradiol were obtained at each aspiration attempt. Statistically significant peaks were found for three healthy volunteers (p < 0.05). However, the peaks that varied across the menstrual cycle were different from one healthy volunteer to another and the differences were small compared with the large variation in proteomic profiles between healthy volunteers. This study provides proof of concept that the NAF proteomic profile does not vary substantially during the menstrual cycle and that therefore it is valid to compare NAF profiles from pre-menopausal women that have been taken at different stages in the menstrual cycle..

The migration of macrophages through peripheral tissues is an essential step in the host response to infection, inflammation, and ischemia as well as in tumor progression and tissue repair. The mannose receptor (MR; CD206, previously known as the macrophage MR) is a 175-kDa type I transmembrane glycoprotein and is a member of a family of four recycling endocytic receptors, which share a common extracellular domain structure but distinct ligand-binding properties and cell type expression patterns. MR has been shown to bind and internalize carbohydrate and collagen ligands and more recently, to have a role in myoblast motility and muscle growth. Given that the related Endo180 (CD280) receptor has also been shown to have a promigratory role, we hypothesized that MR may be involved in regulating macrophage migration and/or chemotaxis. Contrary to expectation, bone marrow-derived macrophages (BMM) from MR-deficient mice showed an increase in random cell migration and no impairment in chemotactic response to a gradient of CSF-1. To investigate whether the related promigratory Endo180 receptor might compensate for lack of MR, mice with homozygous deletions in MR and Endo180 were generated. These animals showed no obvious phenotypic abnormality, and their BMM, like those from MR-deficient mice, retained an enhanced migratory behavior. As MR is down-regulated during macrophage activation, these findings have implications for the regulation of macrophage migration during different stages of pathogenesis..

This pilot study examines the feasibility of nipple aspiration to distinguish women with breast cancer from healthy women using surface-enhanced laser desorption ionisation time-of-flight mass spectrometry (SELDI-TOF/MS). Nipple aspiration fluid (NAF) was collected from each breast in 21 women newly diagnosed with unilateral breast cancer and 44 healthy women. No differences were found when proteomic profiles of NAF from the cancer-bearing breast and the contralateral non-cancerous breast were compared. In contrast, 9 protein peaks were significantly different between the cancer-bearing breast compared with healthy women and 10 peaks were significantly different between the contralateral healthy breast and healthy women (P<0.05). These data suggest that invasive breast cancer may result in a field change across both breasts and that proteomic profiling of NAF may have more value in breast cancer risk assessment than as a diagnostic or screening tool..

By screening a tissue microarray of invasive breast tumors, we have shown that the receptor tyrosine kinase RET (REarranged during Transfection) and its coreceptor GFR alpha 1 (GDNF receptor family alpha-1) are overexpressed in a subset of estrogen receptor-positive tumors. Germ line-activating oncogenic mutations in RET allow this receptor to signal independently of GFR alpha 1 and its ligand glial cell-derived neurotrophic factor (GDNF) to promote a spectrum of endocrine neoplasias. However, it is not known whether tumor progression can also be driven by receptor overexpression and whether expression of GDNF, as has been suggested for other neurotrophic factors, is regulated in response to the inflammatory microenvironment surrounding many epithelial cancers. Here, we show that GDNF stimulation of RET(+)/GFR alpha 1(+) MCF7 breast cancer cells in vitro enhanced cell proliferation and survival, and promoted cell scattering. Moreover, in tumor xenografts, GDNF expression was found to be up-regulated on the infiltrating endogenous fibroblasts and to a lesser extent by the tumor cells themselves. Finally, the inflammatory cytokines tumor necrosis factor-alpha and interleukin-1 beta, which are involved in tumor promotion and development, were found to act synergistically to up-regulate GDNF expression in both fibroblasts and tumor cells. These data indicate that GDNF can act as an important component of the inflammatory response in breast cancers and that its effects are mediated by both paracrine and autocrine stimulation of tumor cells via signaling through the RET and GFR alpha 1 receptors..

Studies of stromal cell populations in lymphoid tissue (LT) have been hampered by a lack of selective markers. Here, we show that CD248 (Endosialin/TEM1) is a stromal marker that is differentially expressed on fibroblasts and pericytes in the thymus, lymph node and spleen. Expression is high during LT development but largely disappears in the adult. CD248 is re-expressed in a Salmonella-induced model of splenic enlargement; peak expression corresponding to the peak of splenic enlargement. These results suggest that CD248 expression helps define a subset of LT stromal cells which play a role in remodelling during tissue development, infection and repair..

Established methods of breast cancer detection have well-described limitations, and new diagnostic techniques are evolving continually to improve diagnostic accuracy. The intraductal approach encompasses the modalities of nipple aspiration, ductal lavage, and duct endoscopy, and is a means of directly accessing the microenvironment of the breast and either sampling or visualizing this intraductal milieu. The aim of sampling this mammary microenvironment is to obtain samples from the physical surroundings of cells that are undergoing malignant transformation, thereby providing a new method of detection before the development of a clinically or radiologically discernible mass. A literature review was conducted to investigate the evolution of the intraductal approach and its particular application in the field of biomarker discovery, primarily using the intraductal technique of nipple aspiration, in combination with emerging protein profiling techniques..

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Mannose receptor (MR) is the best characterised member of a family of four endocytic molecules that share a common domain structure; a cysteine-rich (CR) domain, a fibronectin-type II (FNII) domain and tandemly arranged C-type lectin-like domains (CTLD, eight in the case of MR). Two distinct lectin activities have been described for MR. The CR domain recognises sulphated carbohydrates while the CTLD mediate binding to mannose, fucose or N-acetylglucosamine. FNII domains are known to be important for collagen binding and this has been studied in the context of two members of the MR family, Endo180 and the phospholipase A2 receptor. Here, we have investigated whether the broad and effective lectin activity mediated by the CR domain and CTLD of MR is favoured to the detriment of FNII-mediated interaction(s). We show that MR is able to bind and internalise collagen in a carbohydrate-independent manner and that MR deficient macrophages have a marked defect in collagen IV and gelatin internalisation. These data have major implications at the molecular level as there are now three distinct ligand-binding sites described for MR. Furthermore our findings extend the range of endogenous ligands recognised by MR, a molecule firmly placed at the interface between homeostasis and immunity..

This study demonstrates, through a combination of stringent screening methods and thorough validation, that it is possible to identify transmembrane proteins preferentially expressed in primary breast tumour cells. mRNA was extracted from tumour cells isolated from invasive breast cancers and it was then subtracted against normal breast tissue mRNA prior to the generation of a signal sequence-trap library. Screening of the library identified 31 positive clones encoding 12 cell-surface and 12 secreted proteins. The expression of a subset of transmembrane genes was then interrogated using a high-throughput method (tissue microarray) coupled with cutting-edge in situ techniques in a large cohort of patients who had undergone uniform adjuvant chemotherapy. Expression of CD98 heavy chain (CD98HC) and low-level expression of the insulin-like growth factor 2 receptor/mannose-6-phosphate receptor (IGF2R/M6PR) correlated with poor patient prognosis in the whole cohort. Expression of bradykinin receptor B1 (BDKRB1) and testis enhanced gene transcript (TEGT) correlated with good prognosis in woman with oestrogen receptor (ER)-negative breast tumours. These results indicate that this combined approach of isolating primary tumour cells, generating a library to specifically isolate signal-sequence-containing transcripts, and in situ hybridization on tissue microarrays successfully identified novel prognostic markers (BDKRB1, CD98hc, and TEGT) and potential transmembrane therapeutic targets (CD98hc) in breast cancer..

AIMS: Interactions of cells with the extracellular matrix are important for normal wound healing and may play a role in scar formation. Remarkably, wound healing in human gingiva does not result in scar formation and serves as a model for wound regeneration. Endo180 (CD280) is a cell surface receptor that has novel functions to regulate cell migration and bind and internalize collagens that are key processes in wound healing. The aim of this study was to examine the expression of Endo180 during gingival wound regeneration. METHODS AND RESULTS: Biopsies were collected from normal human gingiva and 1-60 days after wounding and expression of Endo180 was analysed by immunostaining. Expression of Endo180 by cultured fibroblasts and keratinocytes was studied by immunoblotting and semiquantitative reverse transcriptase-polymerase chain reaction. In normal gingiva, Endo180 was expressed by basal epithelial cells, fibroblasts, myofibroblasts, pericytes, macrophages and endothelial cells. In wounds, Endo180 expression was spatiotemporally increased in the migrating and differentiating wound epithelium, in subsets of myofibroblasts, pericytes, macrophages and endothelial cells. Growth factors involved in wound healing up-regulated the expression of Endo180 in keratinocytes and fibroblasts. CONCLUSIONS: The findings suggest that Endo180 plays a role in re-epithelialization and connective tissue remodelling during wound regeneration..

The regulated assembly and disassembly of focal adhesions and adherens junctions contributes to cell motility and tumor invasion. Pivotal in this process is phosphorylation of myosin light chain-2 (MLC2) by Rho kinase (ROCK) downstream of Rho activation, which generates the contractile force necessary to drive disassembly of epithelial cell-cell junctions and cell-matrix adhesions at the rear of migrating cells. How Rho-ROCK-MLC2 activation occurs at these distinct cellular locations is not known, but the emerging concept that endocytic dynamics can coordinate key intracellular signaling events provides vital clues. We report that endosomes containing the promigratory receptor Endo180 (CD280) can generate Rho-ROCK-MLC2-based contractile signals. Moreover, we provide evidence for a cellular mechanism in which Endo180-containing endosomes are spatially localized to facilitate their contractile signals directly at sites of adhesion turnover. We propose migration driven by Endo180 as a model for the spatial regulation of contractility and adhesion dynamics by endosomes..

Cancer progression is associated with enhanced directional cell migration, both of the tumour cells invading into the stroma and stromal cells infiltrating the tumour site. In cell-based assays to study directional cell migration, phorbol esters are frequently used as a chemotactic agent. However, the molecular mechanism by which these activators of protein kinase C (PKC) result in the establishment of a polarized migratory phenotype is not known. Here we show that CD44 expression is essential for chemotaxis towards a phorbol ester gradient. In an investigation of CD44 phosphorylation kinetics in resting and stimulated cells, Ser316 was identified as a novel site of phosphorylation following activation of PKC. PKC does not phosphorylate Ser316 directly, but rather mediates the activation of downstream Ser316 kinase(s). In transfection studies, a phosphorylation-deficient Ser316 mutant was shown to act in a dominant-negative fashion to impair chemotaxis mediated by endogenous CD44 in response to a phorbol ester gradient. Importantly, this mutation had no effect on random cell motility or the ability of cells to migrate directionally towards a cocktail of chemoattractants. These studies demonstrate that CD44 functions to provide directional cues to migrating cells without affecting the motility apparatus..

The mannose receptor family comprises four members in mammals, Endo180 (CD280), DEC-205 (CD205), phospholipase A(2) receptor (PLA(2)R) and the mannose receptor (MR, CD206), whose extracellular portion contains a similar domain arrangement: an N-terminal cysteine-rich domain (CysR) followed by a single fibronectin type II domain (FNII) and 8-10 C-type lectin-like domains (CTLDs). These proteins mediate diverse functions ranging from extracellular matrix turnover through collagen uptake to homeostasis and immunity based on sugar recognition. Endo180 and the MR are multivalent transmembrane receptors capable of interacting with multiple ligands; in both receptors FNII recognizes collagens, and a single CTLD retains lectin activity (CTLD2 in Endo180 and CTLD4 in MR). It is expected that the overall conformation of these multivalent molecules would deeply influence their function as the availability of their binding sites could be altered under different conditions. However, conflicting reports have been published on the three-dimensional arrangement of these receptors. Here, we have used single particle electron microscopy to elucidate the three-dimensional organization of the MR and Endo180. Strikingly, we have found that both receptors display distinct three-dimensional structures, which are, however, conceptually very similar: a bent and compact conformation built upon interactions of the CysR domain and the lone functional CTLD. Biochemical and electron microscopy experiments indicate that, under a low pH mimicking the endosomal environment, both MR and Endo180 experience large conformational changes. We propose a structural model for the mannose receptor family where at least two conformations exist that may serve to regulate differences in ligand selectivity..

INTRODUCTION: Breast cancer is thought to arise in mammary epithelial stem cells. There is, therefore, a large amount of interest in identifying these cells. The breast is a complex tissue consisting of two epithelial layers (an outer myoepithelial/basal layer and an inner luminal epithelial layer) as well as a large non-epithelial component (fibroblasts, endothelial cells, lymphocytes, adipocytes, neurons and myocytes). The definitive identification of a mammary epithelial stem cell population is critically dependent on its purity. To date, this has been hampered by the lack of suitable markers to separate out the two epithelial layers, and to remove contaminating non-epithelial cells. METHODS: Mouse mammary glands were dissociated and stained with CD24. Cells were sorted into separate populations based on CD24 expression and assessed for luminal epithelial and myoepithelial/basal markers by direct fluorescent microscopy and real time PCR. The stem/progenitor potential of these cell populations was assessed in vivo by cleared mammary fat pad transplantation. RESULTS: Three populations of CD24 expressing cells were identified: CD24Negative, CD24Low and CD24High. Staining of these cells with cytokeratin markers revealed that these populations correspond to non-epithelial, myoepithelial/basal and luminal epithelial cells, respectively. Cell identities were confirmed by quantitative PCR. Cleared mammary fat pad transplantation of these cell populations revealed that extensive mammary fat pad repopulation capacity segregates with the CD24Low cells, whilst CD24High cells have limited repopulation capacity. CONCLUSION: Differential staining of mammary epithelial cells for CD24 can be used to simultaneously isolate pure populations of non-epithelial, myoepithelial/basal and luminal epithelial cells. Furthermore, mammary fat pad repopulation capacity is enriched in the CD24Low population. As separation is achieved using a single marker, it will be possible to incorporate additional markers to further subdivide these populations. This will considerably facilitate the further analysis of mammary epithelial subpopulations, whilst ensuring high purity, which is key for understanding mammary epithelial stem cells in normal tissue biology and carcinogenesis..

The accumulation of the extracellular matrix glycosaminoglycan hyaluronan by tumours and tumour-associated stroma promotes cancer cell invasion and metastasis. Using the Dunn chamber chemotaxis assay, we demonstrate for the first time that high molecular mass hyaluronan acts as a soluble chemoattractant promoting the directional migration of MDA-MB-468 and MDA-MB-231 breast cancer cells. Moreover, chemotaxis towards hyaluronan, but not foetal bovine serum, can be abrogated following treatment of the cells with siRNA oligonucleotides to downregulate CD44 expression. These data indicate that CD44 is the principal receptor mediating this response and that CD44 expression is not a general requirement for cell migration and gradient sensing, rather it elicits a ligand-specific response. However, expression of CD44 alone is not sufficient to drive chemotaxis towards hyaluronan, as NIH-3T3 fibroblasts were unable to respond to a hyaluronan gradient even when transfected with high levels of human CD44. For NIH-3T3 cells to bind exogenous hyaluronan, it was necessary to both increase the level of receptor expression and remove a hyaluronan pericellular matrix. Together, these studies reveal a direct mechanism for promoting cell invasion into the hyaluronan-rich matrix and predict that in the complex multicellular environment in vivo, multiple mechanisms exist to regulate the ability of a cell to respond to a chemotactic hyaluronan gradient..

The immune system works through leukocytes interacting with each other, with other cells, with tissue matrices, with infectious agents, and with other antigens. These interactions are mediated by cell-surface glycoproteins and glycolipids. Antibodies against these leukocyte molecules have provided powerful tools for analysis of their structure, function, and distribution. Antibodies have been used widely in hematology, immunology, and pathology, and in research, diagnosis, and therapy. The associated CD nomenclature is commonly used when referring to leukocyte surface molecules and antibodies against them. It provides an essential classification for diagnostic and therapeutic purposes. The most recent (8th) Workshop and Conference on Human Leukocyte Differentiation Antigens (HLDA), held in Adelaide, Australia, in December 2004, allocated 95 new CD designations and made radical changes to its aims and future operational strategy in order to maintain its relevance to modern human biology and clinical practice..

The paradigm for tissue specific homing of leukocytes is the "area code" hypothesis, which predicts that a specific combination of adhesive interactions and chemokine signals from the endothelium directs leukocyte migration into specific tissue sites. This area code hypothesis has been supported by studies from previous HLDA workshops where endothelial specific cell antigens have been studied. Similarly, a clear haematopoietic "stem cell code" comprising the chemokine SDF-1 (CXCL12) and the adhesion receptor VCAM-1 (CD106) has been shown to contribute to the stem cell niche within bone marrow [K. Tokoyoda, T. Egawa, T. Sugiyama, B.I. Chai, T. Nagasawa, Cellular niches controlling B lymphocyte behaviour within bone marrow during development, Immunity 20 (2004) 707-718]. HLDA 7 included a section devoted to stem cell antigens, which began to define additional antigens important in these processes. During the course of HLDA 8 we have extended these observations to determine whether a more global stromal address code defined by fibroblasts, exists in variety of different tissues [G. Parsonage, A.D. Filer, O. Haworth, G.B. Nash, G.E. Rainger, M. Salmon, C.D. Buckley, A stromal area postcode defined by fibroblasts, Trends Immunol. 26 (2005) 150-156]. The stromal cell section in HLDA 8 was designed to complement the malignant cell, endothelial cell, and stem cell/progenitor cell sections. Seven new CD numbers were assigned to antibodies included in this section at the HLDA 8 Workshop meeting held during December 2004..

Fibroblasts are a diverse cell type and display clear topographic differentiation and positional memory. In a screen for fibroblast specific markers we have characterized four monoclonal antibodies to endosialin (TEM1/CD248). Previous studies have reported that endosialin is a tumour endothelium marker and is localized intracellularly. We demonstrate conclusively that endosialin is a cell surface glycoprotein and is predominantly expressed by fibroblasts and a subset of pericytes associated with tumour vessels but not by tumour endothelium. These novel antibodies will facilitate the isolation and classification of fibroblast and pericyte lineages as well as the further functional analysis of endosialin..

AIMS: It is well recognised that intravasation of tumour cells into the vasculature and/or lymphatics is a key stage in the metastatic process. It is also clear that very little is known about the mechanisms underlying this event. In this review, we will focus on cell surface molecules that may be instrumental in mediating the attachment of tumour cells, and in particular breast carcinoma cells, to the lymphatic and microvascular endothelia and discuss the therapeutic and prognostic value in targeting these receptors in metastatic disease. METHODS: A literature search was carried out from PubMed for indexed articles and reviews. Websites containing information on gene expression profiles were located using standard web browser search functions. For articles containing gene expression data, relevant information was frequently located in supplementary tables or in associated websites. FINDINGS: The search yielded a very large number of indexed published articles and websites. Important major reports and studies were reviewed, screened and tracked for other relevant publications. The most important articles were analysed and discussed. CONCLUSIONS: The lack of knowledge as to the mechanism by which tumour cells intra-vasate into the vasculature and/or lymphatics is perhaps not surprising given the lack of suitable models with which to investigate tumour cell intravasation. However, recent advances in the identification of molecular markers of angiogenic and lymphangiogenic endothelium, the development of techniques to image tumour cells in vivo and a better understanding of the architecture of these vessels is beginning to offer hope that this least well understood event in the metastatic process is becoming more amenable to study..

Type I collagen is a fibril-forming heterotrimer composed of two alpha1 and one alpha2 chains and plays a crucial role in cell-matrix adhesion and cell differentiation. Through a comprehensive differential display screening of oncogenic ras target genes, we have shown that the alpha1 chain of type I collagen (col1a1) is markedly down-regulated by the ras oncogene through the mitogen-activated protein kinase pathway. Although ras-transformed cells are no longer able to produce and secrete endogenous collagen, they can still adhere to exogenous collagen, suggesting that the cells express a collagen binding factor(s) on the cell surface. When the region of col1a1 encompassing the C-terminal glycine repeat and C-prodomain (amino acids 1000-1453) was affinity-labeled with human placental alkaline phosphatase, the secreted trimeric fusion protein could bind to the surface of Ras-transformed cells. Using biochemical purification followed by matrix-assisted laser desorption/ionization mass spectrometry analysis, we identified this collagen binding factor as Endo180 (uPARAP, CD280), a member of the mannose receptor family. Ectopic expression of Endo180 in CosE5 cells followed by in situ staining and quantitative binding assays confirmed that Endo180 indeed recognizes and binds to placental alkaline phosphatase. The interaction between Endo180 and the C-terminal region of type I collagen appears to play an important role in cell-matrix adhesion..

OBJECTIVE: To investigate the expression of a novel member of the mannose receptor family, Endo180 (also known as uPARAP), and the distribution of Endo180 ligand(s) in the articular cartilage and growth plate of normal CBA mice and STR/ort mice, a well characterized model of spontaneous osteoarthritis. DESIGN: A polyclonal anti-Endo180 antibody was used to determine receptor expression. The Endo180 extracellular domain fused to a human immunoglobulin Fc tail was used to detect ligand. RESULTS: Endo180 receptor was strongly expressed in chondrocytes both in vitro and throughout the articular cartilage of young CBA and STR/ort mice. Expression decreased in older animals. In STR/ort mice with osteoarthritic lesions, no upregulation of Endo180 was detected. In the developing growth plate, Endo180 was expressed strongly by the proliferating chondrocytes. In contrast, Endo180 ligand was detected most strongly in hypertrophic zone of the growth plate and only at low levels in articular cartilage. In cultured chondrocytes, Endo180 was localized on the cell surface and in intracellular vesicles. CONCLUSION: Constitutively recycling endocytic receptors function to internalize ligand from the extracellular milieu and the ability of Endo180 to bind both glycosylated ligands and collagens suggests a role in extracellular matrix remodeling. Expression of Endo180 in articular cartilage chondrocytes of young, but not old, mice and the reciprocal expression of Endo180 and its ligands in the growth plate suggest that this receptor is involved in cartilage development but not in cartilage homeostasis. In addition, our data indicates that Endo180 does not appear to play a role in the development or progression of murine osteoarthritis..

BACKGROUND: A useful application of flow cytometry is the investigation of cell receptor-ligand interactions. However such analyses are often compromised due to problems interpreting changes in ligand binding where the receptor expression is not constant. Commonly, problems are encountered due to cell treatments resulting in altered receptor expression levels, or when cell lines expressing a transfected receptor with variable expression are being compared. To overcome this limitation we have developed a Microsoft Excel spreadsheet that aims to automatically and effectively simplify flow cytometric data and perform statistical tests in order to provide a clearer graphical representation of results. RESULTS: To demonstrate the use and advantages of this new spreadsheet method we have investigated the binding of the transmembrane adhesion receptor CD44 to its ligand hyaluronan. In the first example, phorbol ester treatment of cells results in both increased CD44 expression and increased hyaluronan binding. By applying the spreadsheet method we effectively demonstrate that this increased ligand binding results from receptor activation. In the second example we have compared AKR1 cells transfected either with wild type CD44 (WT CD44) or a mutant with a truncated cytoplasmic domain (CD44-T). These two populations do not have equivalent receptor expression levels but by using the spreadsheet method hyaluronan binding could be compared without the need to generate single cell clones or FACS sorting the cells for matching CD44 expression. By this method it was demonstrated that hyaluronan binding requires a threshold expression of CD44 and that this threshold is higher for CD44-T. However, at high CD44-T expression, binding was equivalent to WT CD44 indicating that the cytoplasmic domain has a role in presenting the receptor at the cell surface in a form required for efficient hyaluronan binding rather than modulating receptor activity. CONCLUSION: Using the attached spreadsheets and instructions, a simple post-acquisition method for analysing bivariate flow cytometry data is provided. This method constitutes a straightforward improvement over the standard graphical output of flow cytometric data and has the significant advantage that ligand binding can be compared between cell populations irrespective of receptor expression levels..

CD44 is a widely distributed type I transmembrane glycoprotein and functions as the major hyaluronan receptor on most cell types. Although alternative splicing can produce a large number of different isoforms, they all retain the hyaluronan-binding Link-homology region and a common transmembrane and cytoplasmic domain, which are highly conserved between species. The past decade has seen an extensive investigation of this receptor owing to its importance in mediating cell-cell and cell-matrix interactions in both normal and disease states. Although roles for alternative splicing and variable glycosylation in determining ligand-binding interactions are now well established, the mechanisms by which CD44 integrates structural and signalling events to elicit cellular responses have been less well understood. However, there is now increasing evidence that CD44 is assembled in a regulated manner into membrane-cytoskeletal junctional complexes and, through both direct and indirect interactions, serves to focus downstream signal transduction events..

The ERM proteins (ezrin, radixin, moesin) together with merlin comprise a subgroup of the band 4.1 superfamily. These proteins act as membrane cytoskeletal linker proteins mediating interactions between the cytoplasmic domains of transmembrane proteins and actin. To better understand how the ERM proteins function to regulate these junctional complexes, a yeast 2-hybrid screen was undertaken using ezrin as a bait. We describe here the identification and cloning of a novel protein, PACE-1, which binds to the C-terminal domain of ezrin. Characterization of PACE-1 in human breast cancer cell lines demonstrates it to have two distinct intracellular localizations. A proportion of the protein is associated with the cytoplasmic face of the Golgi apparatus. This distribution is dependent upon the presence of the PACE-1 N-terminal myristoylation consensus sequence but is not dependent on an association with ezrin. In contrast, PACE-1 colocalises with ezrin in the lamellipodia, where ezrin has a role in cell spreading and motility. A notable feature of PACE-1 is the presence of a putative N-terminal kinase domain; however, in biochemical assays PACE-1 was shown to have associated rather than intrinsic kinase activity. Together these data suggest that PACE-1 may play a role in regulating cell adhesion/migration complexes in migrating cells..

Urokinase-type plasminogen activator (uPA) and its receptor (uPAR) play an important role in cell guidance and chemotaxis during normal and pathological events. uPAR is GPI-anchored and the mechanism by which it transmits intracellular polarity cues across the plasma membrane during directional sensing has not been elucidated. The constitutively recycling endocytic receptor Endo180 forms a trimolecular complex with uPAR in the presence of uPA, hence its alternate name uPAR-associated protein. Here, we demonstrate that Endo180 is a general promoter of random cell migration and has a more specific function in cell chemotaxis up a uPA gradient. Endo180 expression was demonstrated to enhance uPA-mediated filopodia production and promote rapid activation of Cdc42 and Rac. Expression of a noninternalizing Endo180 mutant revealed that promotion of random cell migration requires receptor endocytosis, whereas the chemotactic response to uPA does not. From these studies, we conclude that Endo180 is a crucial link between uPA-uPAR and setting of the internal cellular compass..

The four members of the mannose receptor family (the mannose receptor, the M-type phospholipase A(2) receptor, DEC-205 and Endo180) share a common extracellular arrangement of an amino-terminal cysteine-rich domain followed by a fibronectin type II (FNII) domain and multiple C-type lectin-like domains (CTLDs). In addition, all have a short cytoplasmic domain, which mediates their constitutive recycling between the plasma membrane and the endosomal apparatus, suggesting that these receptors function to internalize ligands for intracellular delivery. We have generated mice with a targeted deletion of Endo180 exons 2-6 and show that this mutation results in the efficient expression of a truncated Endo180 protein that lacks the cysteine-rich domain, the FNII domain and CTLD1. Analysis of embryonic fibroblasts reveals that this mutation does not disrupt the C-type lectin activity that is mediated by CTLD2, but results in cells that have a defect in collagen binding and internalization and an impaired migratory phenotype..

Endo180, also known as the urokinase plasminogen activator receptor (uPAR)-associated protein (uPARAP), is one of the four members of the mannose receptor family, and is implicated in extracellular-matrix remodelling through its interactions with collagens, sugars and uPAR. The extracellular portion of Endo180 contains an amino-terminal cysteine-rich domain, a single fibronectin type II domain and eight C-type lectin-like domains. We have purified a soluble version of Endo180 and analysed it by single-particle electron microscopy to obtain a three-dimensional structure of the N-terminal part of the protein at a resolution of 17 A and reveal, for the first time, the interactions between non-adjacent domains in the mannose receptor family. We show that for Endo180, the cysteine-rich domain contacts the second C-type lectin-like domain, thus providing structural insight into how modulation of its several ligand interactions may regulate Endo180 receptor function..

Endo180, a member of the mannose receptor family, is constitutively recycled between clathrin-coated pits on the cell surface and intracellular endosomes. Its large extracellular domain contains an N-terminal cysteine-rich domain, a single fibronectin type II domain and eight C-type lectin-like domains. The second of these lectin-like domains has been shown to mediate Ca2+-dependent mannose binding. In addition, cross-linking studies have identified Endo180 as a urokinase plasminogen activator receptor-associated protein and this interaction can be blocked by collagen V. Here we demonstrate directly using in vitro assays, cell-based studies and tissue immunohistochemistry that Endo180 binds both to native and denatured collagens and provide evidence that this is mediated by the fibronectin type II domain. In cell culture systems, expression of Endo180 results in the rapid uptake of soluble collagens for delivery to lysosomal degradative compartments. Together with the observed restricted expression of Endo180 in both embryonic and adult tissue, we propose that Endo180 plays a physiological role in mediating collagen matrix remodelling during tissue development and homeostasis and that the observed receptor upregulation in pathological conditions may contribute to disease progression..

Procollagenase 3 can be activated by interaction with and cleavage by the cell-associated membrane type 1 metalloproteinase (MT1 MMP; MMP 14). It has also been shown to bind to a specific receptor, and is subsequently internalized via the low-density lipoprotein-related receptor by osteoblast cell lines. The receptor was identified as a recycling glycoprotein of the macrophage mannose receptor family, Endo180. In order to ascertain whether there is a relationship between Endo180 binding and procollagenase 3 activation, we have compared procollagenase 3 activation by an HT1080 fibrosarcoma cell line overexpressing MT1 MMP, without and with overexpression of Endo180. No difference in procollagenase 3 activation was observed, and neither was the enzyme bound to the cells or internalized. In contrast, the osteoblast cell lines, MG63 and UMR-106, both bound and internalized procollagenase 3. However, immunolocalization studies showed that the Endo180 abundantly expressed by these cells did not co-localize with the procollagenase 3. In further biochemical studies we confirmed that procollagenase 3 did not bind to Endo180, using both ligand- blotting and immunoprecipitation techniques. We conclude that Endo180 is unlikely to be a receptor for collagenase 3 in relation to either its activation or cell binding and internalization, and that other interaction partners must be sought..

The dynamic assembly and disassembly of membrane cytoskeleton junctional complexes is critical in cell migration. Here we describe a novel phosphorylation mechanism that regulates the hyaluronan receptor CD44. In resting cells, CD44 is constitutively phosphorylated at a single serine residue, Ser325. After protein kinase C is activated, a switch in phosphorylation results in CD44 being phosphorylated solely at an alternative residue, Ser291. Using fluorescence resonance energy transfer (FRET) monitored by fluorescence lifetime imaging microscopy (FLIM) and chemotaxis assays we show that phosphorylation of Ser291 modulates the interaction between CD44 and the cytoskeletal linker protein ezrin in vivo, and that this phosphorylation is critical for CD44-dependent directional cell motility..

CD44 is a widely expressed cell surface hyaluronan receptor which plays a key role in mediating cell migration. A number of recent papers demonstrating an interplay between CD44 and matrix metalloproteinases (MMPs) have shed important insights into the molecular mechanisms underlying these events. This has important implication for understanding how mis-regulation of CD44 can contribute to disease pathologies..

The mannose receptor family comprises four glycoproteins each of which is a type I transmembrane receptor with an N-terminal cysteine-rich domain, a single fibronectin type II (FNII) domain and eight to ten C-type lectin-like domains (CTLDs). Characteristically, these proteins are able to recycle between the plasma membrane and the endosomal apparatus due to discrete motifs present within their cytoplasmic domains. This review discusses the structure and function of these four proteins-the mannose receptor (MR), the M-type receptor for secretory phospholipases A(2) (PLA(2)R), DEC-205/gp200-MR6 and Endo180/uPARAP. Despite their overall structural similarity, these four receptors have evolved to use different domains to interact with discrete ligands. In addition, they differ in their ability to mediate endocytic and phagocytic events and in their intracellular destinations. Together, they represent a unique group of multidomain, multifunctional receptors..

Members of the mannose receptor family, the mannose receptor, the phospholipase A(2) receptor, DEC-205, and Endo180, contain multiple C-type lectin-like domains (CTLDs) within a single polypeptide. In addition, at their N termini, all four family members contain a cysteine-rich domain similar to the R-type carbohydrate recognition domains of ricin. However, despite the common presence of multiple lectin-like domains, these four endocytic receptors have divergent ligand binding activities, and it is clear that the majority of these domains do not bind sugars. Here the functions of the lectin-like domains of the most recently discovered family member, Endo180, have been investigated. Endo180 is shown to bind in a Ca(2+)-dependent manner to mannose, fucose, and N-acetylglucosamine but not to galactose. This activity is mediated by one of the eight CTLDs, CTLD2. Competition assays indicate that the monosaccharide binding specificity of Endo180 CTLD2 is similar to that of mannose receptor CTLD4. However, additional experiments indicate that, unlike the cysteine-rich domain of the mannose receptor, the cysteine-rich domain of Endo180 does not bind sulfated sugars. Thus, although Endo180 and the mannose receptor are now both known to be mannose binding lectins, each receptor is likely to have a distinct set of glycoprotein ligands in vivo..

Endo180/urokinase plasminogen activator receptor-associated protein together with the mannose receptor, the phospholipase A(2) receptor, and DEC-205/MR6-gp200 comprise the four members of the mannose receptor family. These receptors have a unique structural composition due to the presence of multiple C-type lectin-like domains within a single polypeptide backbone. In addition, they are all constitutively internalized from the plasma membrane via clathrin-mediated endocytosis and recycled back to the cell surface. Endo180 is a multifunctional receptor displaying Ca(2+)-dependent lectin activity, collagen binding, and association with the urokinase plasminogen activator receptor, and it has a proposed role in extracellular matrix degradation and remodeling. Within their short cytoplasmic domains, all four receptors contain both a conserved tyrosine-based and dihydrophobic-based putative endocytosis motif. Unexpectedly, Endo180 was found to be distinct within the family in that the tyrosine-based motif is not required for efficient delivery to and recycling from early endosomes. By contrast, receptor internalization is completely dependent on the dihydrophobic motif and modulated by a conserved upstream acidic residue. Furthermore, unlike the mannose receptor, Endo180 does not function as a phagocytic receptor in vitro. These findings demonstrate that despite an overall structural similarity, members of this receptor family employ distinct trafficking mechanisms that may reflect important differences in their physiological functions..

CD44 is the principal cell surface receptor for the extracellular matrix glycosaminoglycan hyaluronan, and binding to this ligand underlies CD44-mediated cell attachment and migration. As would be expected for a widely expressed adhesion receptor, CD44 is subject to complex regulatory events, and mis-regulation of the receptor has been associated with a number of disease pathologies, including chronic inflammatory conditions and the progression of metastatic tumours. In previous studies we have demonstrated that a key control point for this receptor is the phosphorylation of CD44 on a conserved cytoplasmic serine residue, Ser(325). This modification is not required for efficient ligand binding, but is an essential component of CD44-dependent cell migration on a hyaluronan substratum. To understand better the mechanism regulating CD44 phosphorylation on Ser(325), we have generated a monoclonal antibody that specifically recognizes CD44 phosphorylated on Ser(325), and have developed assays to identify the Ser(325) kinase. We demonstrate here that CD44 is phosphorylated to high stoichiometry in resting cells and that Ca(2+)/calmodulin-dependent protein kinase II is a CD44 Ser(325) kinase..

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Endo180 was previously characterized as a novel, cell type specific, recycling transmembrane glycoprotein. This manuscript describes the isolation of a full length human Endo180 cDNA clone which was shown to encode a fourth member of a family of proteins comprising the macrophage mannose receptor, the phospholipase A(2) receptor and the DEC-205/MR6 receptor. This receptor family is unusual in that they contain 8-10 C-type lectin carbohydrate recognition domains in a single polypeptide backbone, however, only the macrophage mannose receptor had been shown to function as a lectin. Sequence analysis of Endo180 reveals that the second carbohydrate recognition domain has retained key conserved amino acids found in other functional C-type lectins. Furthermore, it is demonstrated that this protein displays Ca(2+)-dependent binding to N-acetylglucosamine but not mannose affinity columns. In order to characterize the physiological function of Endo180, a series of biochemical and morphological studies were undertaken. Endo180 is found to be predominantly expressed in vivo and in vitro on fibroblasts, endothelial cells and macrophages, and the distribution and post-translational processing in these cells is consistent with Endo180 functioning to internalize glycosylated ligands from the extracellular milieu for release in an endosomal compartment..

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ERM (ezrin, radixin and moesin) proteins function as linkers between the actin cytoskeleton and the plasma membrane. In addition to this structural role, these proteins are highly regulatable making them ideal candidates to mediate important physiological events such as adhesion and membrane morphology and to control formation and breakdown of membrane-cytoskeletal junctions. Recently, a direct interaction in vitro has been demonstrated between ERM proteins and the hyaluronan receptor, CD44. We have mapped the ezrin-binding site to two clusters of basic amino acids in a membrane-proximal 9 amino-acid region within the CD44 cytoplasmic domain. To investigate the functional importance of this interaction in vivo, we created a number of mutations within full-length CD44 and expressed these mutants in human melanoma cells. We demonstrate here that mutations within the ezrin-binding site do not disrupt the plasma membrane localization of CD44 and, in addition, that this region is not required to mediate efficient hyaluronan binding. These studies suggest that ERM proteins mediate the outside-in, rather than inside-out, signalling of adhesion receptors..

CD44 is the principle transmembrane receptor for the extracellular matrix glycosaminoglycan hyaluronan. This receptor:ligand interaction plays an essential role in a number of physiological events including tumour progression, lymphocyte homing into inflammatory sites and tissue morphogenesis during development. In previous studies we have shown that serine phosphorylation is a critical control mechanism for CD44-dependent cell migration. Here we have investigated the target phosphorylation residues by mutating them individually or in combination. These studies demonstrate that Ser325 is the principle CD44 phosphorylation site and that mutation of this residue blocks CD44-mediated cell migration but not hyaluronan binding. In addition, we show that an upstream Ser323 residue is required as part of the kinase consensus site. To further characterize the role of CD44 phosphorylation, phosphorylated and non-phosphorylated peptides spanning the Ser325 region were synthesised and linked to a 16 amino acid Penetratin sequence to mediate efficient plasma membrane translocation. Peptides containing a phosphoserine at residue 325 are efficient blockers of CD44-mediated cell migration but do not reduce CD44 expression or its ability to bind hyaluronan. These data strongly argue that CD44 adhesion and migration are regulated by distinct mechanisms and that migration requires the specific interaction of intracellular component(s) with phosphorylated CD44 receptors..

BACKGROUND: CD44 is a transmembrane receptor for the extracellular matrix glycosaminoglycan, hyaluronan. This receptor-ligand interaction plays an essential role in tumour progression, in embryonic tissue morphogenesis and in leukocyte migration during inflammation. It is well documented that the interaction between CD44 and hyaluronan is strictly regulated, but little is known about the relationship between hyaluronan-dependent cell adhesion and cell migration. RESULTS: In these studies we have used a CD44-negative human melanoma cell line and a murine fibroblast line which expresses low levels of endogenous CD44. Both cell lines were transfected with plasmids encoding wild-type human CD44 or CD44 phosphorylation mutants, in which the target serines had been mutated to small neutral amino acids or large acidic residues. We show that expression of wild-type CD44 enhances the ability of both cell lines to bind to, and migrate on, a hyaluronan-coated substratum. In contrast, the two CD44 phosphorylation mutants were as efficient as wild-type CD44 in mediating cell adhesion but were unable to support hyaluronan-dependent migration. CONCLUSIONS: These studies demonstrate a control mechanism specific for CD44-mediated cell motility and have implications for the regulation of metastatic progression by cell-adhesion receptors..

Both in vivo and in vitro the distribution of the resident plasma membrane adhesion protein, CD44, is restricted to the basolateral domain of polarized epithelial cells, suggesting a role in interepithelial interactions. To determine how this localization might be regulated a range of CD44 cytoplasmic domain mutations were generated and a minimal 5 amino acid sequence, His330-Leu-Val-Asn-Lys334, was identified which when deleted results in expression of CD44 on the apical microvillal membrane. Further mutagenesis throughout this regions pinpointed a critical di-hydrophobic motif, Leu331/Val332. The ability of wild type but not mutant CD44 cytoplasmic domains to redirect an apically targeted protein, placental alkaline phosphatase, to the basolateral plasma membrane demonstrates that this sequence can function as a dominant localization signal. This His330-Lys334 sequence is spatially separate from other CD44 regulatory elements and as discussed here, a comparison with known basolateral sorting sequences identified in other transmembrane proteins suggests that a distinct mechanism operates to retain resident plasma membrane proteins in their correct plasma membrane subdomains..

CD44 is an adhesion receptor for which the major characterized ligand is the extracellular matrix glycosaminoglycan, hyaluronan. This interaction underlies CD44-mediated cell attachment, cell migration, and matrix remodelling during development and wound healing. Truncation of the CD44 cytoplasmic domain does not prevent cell surface expression of this hyaluronan receptor but it dramatically impairs ligand binding. In this study we have examined the role of phosphorylation in regulating this function by mutating the target serine residues to either neutral amino acids with the aim of creating a phosphorylation-incompetent molecule, or to acidic residues to mimic a fully phosphorylated CD44. In transfected AKR1 cells the behavior of both the neutral and acidic mutants was indistinguishable from wild-type CD44, indicating that there is a phosphorylation-independent mechanism involved in regulating hyaluronan binding..

This paper describes the expression profile of the CD44 glycoprotein during differentiation of embryonal carcinoma (EC) and embryonic stem (ES) cells. We have recently shown that CD44 is expressed in discrete embryonic structures and, in view of this, we sought an in vitro differentiation model of development in which we could study more readily the structure and function of the CD44 molecule. The P19 EC and CGR8 ES cells were chosen as they have the capacity to develop down the cardiac muscle pathway and we have previously demonstrated that CD44 is expressed abundantly in the embryonic myocardium. The differentiation process in both cell types is accompanied by an induction of CD44 mRNA and protein. However, in differentiated cultures CD44 is not expressed in contractile cells, indicating that these P19 cells do not represent CD44-positive embryonic cardiomyocytes. Expression of CD44 is observed on fibroblast-like cells which appear to migrate over and out from the plated aggregates. Hyaluronan, the major ligand for CD44, is also associated with these CD44-positive fibroblast-like cells. It is suggested that expression of both receptor and ligand by the fibroblast cells is required for cell:matrix adhesion and cell motility. As CD44 is up-regulated in these cultures, P19 cells are now established as a useful model system to study the factors regulating expression of the CD44 gene..

CD44 is an abundant, widely expressed transmembrane glycoprotein which can act as a receptor for the extracellular matrix glycosaminoglycan, hyaluronan. Biochemical and morphological studies have demonstrated that in fibroblasts a significant of the CD44 population is resistant to Triton X-100 extraction and that the detergent insoluble protein is co-localized with components of the cortical cytoskeleton. Surprisingly, this distribution is not abrogated upon deletion of the CD44 cytoplasmic tail indicating that mechanisms other than a direct interaction with the cytoskeleton can regulate CD44. In this manuscript, the mechanisms underlying this detergent-insoluble association are further investigated. There was no evidence that the Triton X-100 insolubility of CD44 resulted from homotypic aggregation, an association with hyaluronan or from a direct, or indirect, association with the cytoskeleton. Instead, evidence is presented that the detergent insolubility of fibroblast CD44 at 4 degrees C results from an association of the CD44 transmembrane domain with Triton X-100 resistant, lipid rich, plasma membrane domains. The proportion of the CD44 found in these Triton X-100 insoluble structures is dependent upon cell type and cannot be altered by changing cell motility or extracellular matrix associations. These studies provide evidence for a novel mechanism regulating this adhesion protein in the plasma membrane..

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A number of recent reports on the trafficking of receptor proteins in MDCK epithelial cells have provided evidence that delivery to the basolateral domain requires a specific targeting sequence and that deletion of this sequence results in constitutive expression on the apical surface. To date, these studies have concentrated on receptors which are competent for internalization via the clathrin coated pits. We have examined the localization of a resident plasma membrane protein by transfecting human CD44 into MDCK cells. Using human specific and cross-species reactive antibodies, we show that in MDCK cells both the endogenous and transfected wild-type CD44 are found on the basolateral surface where they are restricted to the lateral domain. Deletion of the CD44 cytoplasmic tail reduces the half life of this mutant protein and causes it to be expressed both on the apical surface and to a significant extent within the cell. We have also used biochemical and morphological analysis to investigate the interaction of CD44 with the cytoskeleton in detergent extracted cells. Strikingly different extraction results were obtained between epithelial and fibroblast cells. However, there is no difference in the Triton X-100 solubility of the transfected wild-type and tail-less CD44 in fibroblasts and both forms of the protein remain associated with the cortical cytoskeleton after Triton X-100 extraction. These results demonstrate that the sequence present in the cytoplasmic domain of CD44 responsible for its distribution in epithelial cells is functionally and spatially separate from the ability of this protein to associate with the cytoskeleton..

CD44 is a multifunctional adhesion protein that acts as a major receptor for the hygroscopic extracellular matrix component, hyaluronan. This receptor-ligand binding directly mediates at least some of the cell-cell and cell-matrix interactions ascribed to CD44. Other interactions involving CD44 may be modulated indirectly by its ability to bind growth factors and thereby to promote cell attachment. During vertebrate development, multiple cases of hyaluronan involvement in cell proliferation, cell migration and histogenesis have been documented. In addition, there is evidence suggesting a central role for cell surface glycoproteins and proteoglycans in mediating the action of polypeptide growth factors involved in tissue patterning. In view of this, we undertook to investigate expression of the CD44 protein during postimplantation mouse embryogenesis. Between 9.5 and 12.5 days of embryonic development, the predominant form of CD44 protein corresponds to the hyaluronan-binding CD44H form. However, species with a higher M(r) were also detected, implying that CD44 isoforms generated by alternative splicing of CD44 RNA are employed in normal development. Further, we used mouse embryos to perform whole-mount immunohistochemistry and examine the temporal and spatial distribution of this glycoprotein. CD44 is expressed at high levels in the heart, somites and condensing limb-bud mesenchyme at critical stages of morphogenesis. These sites correlate with regions where hyaluronan has been demonstrated to regulate morphogenetic events. Of novel interest, however, is the high expression of CD44 in regions that do not correlate with sites of known hyaluronan-mediated developmental events. These include instructive epithelia participating in epithelial-mesenchymal cell interactions such as the apical ectodermal ridge of the developing limb bud and the odontogenic placodes of the presumptive upper and lower jaws..

CD44 has been implicated to play an important role in a diverse range of physiological processes, which involve cell-matrix recognition, cell-cell adhesion and cell motility. There is increasing evidence that the highly conserved intracellular domain of CD44 may be involved in influencing these activities. CD44 is phosphorylated in vivo on serine residue(s). In view of the importance that phosphorylation has been accorded in a multitude of cellular regulatory processes, we have investigated the role of phosphorylation in the control of CD44. In this report we identify the sites of human CD44 phosphorylation by mutating the three conserved cytoplasmic serine residues. We show that both Ser323 and Ser325, but not Ser316, are required for phosphorylation in vivo and demonstrate that this event is not stimulated by phorbol esters. Clonal MDCK cell lines expressing both the single and double CD44 phosphorylation mutants have been generated. These cell lines have been used to directly assess the role of phosphorylation on CD44 localization in polarized epithelial cells and its association with the cytoskeleton..

A 180-kilodalton (kDa) protein (p180) was identified among the antigens for a panel of monoclonal antibodies raised against human fibroblast cell surface proteins. Binding studies with 125I-Fab' fragments of an anti-p180 monoclonal antibody demonstrated that 10 to 30% of p180 was located on the plasma membrane and that the remaining 70 to 90% was on intracellular membranes. p180 was rapidly internalized from the cell surface at 37 degrees C, and kinetic analyses indicated that this was a constitutive process followed by the recycling of p180 back to the plasma membrane. Morphological studies demonstrated that on the cell surface p180 was concentrated in coated pits, whereas inside the cell it was found in endosomes as suggested by its colocalization with the transferrin receptor. Immunoblot analysis with a polyclonal antiserum raised against purified human protein showed that p180 has a restricted distribution with expression at high levels in fibroblast cultures and in tissues containing cells of mesodermal origin. A biochemical characterization of p180 showed it to be a transmembrane glycoprotein with an extracellular domain, which consists of approximately 30 kDa of complex oligosaccharides attached to at least 45 kDa of the protein core. The cytoplasmic domain of p180 was found to contain a serine residue(s) that was phosphorylated both in vivo and in vitro by activated protein kinase C. p180 was purified by subjecting solubilized membrane proteins from a human osteosarcoma cell line to immunoaffinity chromatography and gel filtration. The N-terminal sequence information obtained from the purified protein showed no homology to other known proteins. It was concluded that p180 may be a novel recycling receptor which is highly restricted in its expression to fibroblastlike cells..

p36 and p35 are distinct but related proteins that share many structural and biochemical features which were first identified as major substrates for protein-tyrosine kinases. Subsequently, both proteins have been shown to be Ca2+-, phospholipid-, and F-actin-binding proteins that underlie the plasma membrane and are associated with the cortical cytoskeleton. Recent reports have claimed that these proteins function as lipocortins, i.e., phospholipase A2 inhibitors that mediate the anti-inflammatory action of glucocorticoids. To investigate this possibility and to learn more about the functions of p36 and p35, we used human-specific anti-p36 and anti-p35 monoclonal antibodies to determine whether the expression or secretion of either protein was inducible by dexamethasone in the human U-937 myeloid cell line and in other human cell types. Additionally, we examined the levels of mRNA for both proteins. No effect of dexamethasone was observed on p36 or p35 expression at either the mRNA or protein level, nor were these proteins secreted under any of the culture conditions investigated. However, it was observed that in these cells the rate of synthesis and accumulation of both proteins was increased when the U-937 cells were induced to differentiate in culture to adherent macrophagelike cells. This offers a model system with which to study the control of p36 and p35 expression..

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p36, a major in vivo substrate of protein-tyrosine kinases, is shown to be phosphorylated at serine 25, a site very close to the major site of tyrosine phosphorylation by pp60v-src, tyrosine 23 (J. R. Glenney, Jr., and B. F. Tack, Proc. Natl. Acad. Sci. USA 82:7884-7888, 1985). We present evidence suggesting that protein kinase C mediates phosphorylation of serine 25..

We have characterized two monoclonal antibodies which recognize human p36. These have been used to examine the sites and extent of serine and tyrosine phosphorylation of p36 in human cells treated with epidermal growth factor and platelet-derived growth factor and in human cells transformed with viruses whose oncogenes encode protein-tyrosine kinases..

Bombesin and the related mammalian peptides, such as gastrin-releasing peptide (GRP), are potent mitogens for some fibroblast cell lines. Here we have examined the bombesin- and GRP-mediated changes in the phosphorylation of proteins in Swiss 3T3 cells and compared these to the events observed after platelet-derived growth factor (PDGF), epidermal growth factor (EGF) and tumor promoter treatment. In agreement with previous reports, bombesin, GRP and PDGF, but not EGF, increased the activity of protein kinase C. This was assayed by an inhibition of [125I]EGF binding, stimulation in phosphorylation of pp60c-src on serine 12 and stimulation in phosphorylation of a group of 80 kd proteins. The different phosphorylated forms of the 80 kd proteins were examined by tryptic peptide mapping and shown to contain multiple phosphorylation sites. An investigation of the tyrosine phosphorylation events following mitogen treatment revealed a significant difference between PDGF and the bombesin peptides. PDGF treatment caused a marked increase in total cellular phosphotyrosine levels, and tyrosine phosphorylation both of known substrates and its own receptor. In contrast, bombesin and GRP treatments resulted in only a weak or undetectable increase in tyrosine phosphorylation of total cellular protein or known substrates. In this respect bombesin and GRP were more similar to EGF. The fact that the bombesin peptides do not induce a phosphorylation response identical with either PDGF or EGF suggests that there is not a single common signal pathway which is activated by all these mitogens..

A role for proto-oncogenes in the regulation and modulation of cell proliferation has been suggested by the findings that the B-chain of platelet-derived growth factor (PDGF) is encoded by the proto-oncogene sis and that the erb-B oncogene product is a truncated form of the epidermal growth factor (EGF) receptor. Furthermore, the product of the proto-oncogene fms (c-fms) may be related or identical to the receptor for macrophage colony-stimulating factor (CSF-1). v-fms is the transforming gene of the McDonough strain of feline sarcoma virus (SM-FeSV) and belongs to the family of src-related oncogenes which have tyrosine-specific kinase activity. Furthermore, nucleotide sequence analysis of the v-fms gene product revealed topological properties of a cell-surface receptor protein. To elucidate the features involved in the conversion of a normal cell-surface receptor gene into an oncogenic one, we have now determined the complete nucleotide sequence of a human c-fms complementary DNA. The 972-amino-acid c-fms protein has an extracellular domain, a membrane-spanning region, and a cytoplasmic tyrosine protein kinase domain. Comparison of the feline v-fms and human c-fms sequences reveals that the proteins share extensive homology but have different carboxyl termini..

Two monoclonal antibodies have been raised against human Pgp-1 by the immunization of mice with human fibroblasts. The human molecule, like the previously identified mouse counterpart, is an abundant membrane protein (Mr approximately 95 000) with a broad tissue distribution. Pgp-1 is phosphorylated, and phosphoamino acid analysis demonstrates that this occurs exclusively on serine residues. A major difference between the mouse and the human is that 50-60% of human thymocytes are Pgp-1+ compared to 5-10% of mouse thymocytes at an equivalent stage in development. Immunofluorescence studies of cryostat sections showed that the majority of human medullary thymocytes are strongly stained with Pgp-1-specific antibody, whereas the expression of Pgp-1 on cortical thymocytes is much more heterogeneous..

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A potent growth factor, PC13 embryonal carcinoma-derived growth factor (ECDGF), has been isolated from serum-free medium conditioned by PC13 murine embryonal carcinoma cells. ECDGF is a single chain, cationic hydrophobic molecule of 17 500 daltons. ECDGF will induce DNA synthesis in established fibroblast cell lines and the immediate differentiated progeny of PC13 EC cells in vitro, and consequently appears to differ from other well characterised growth factors both in structure and action..

Malignant PC13 embryonal carcinoma (EC) cells differentiate in vitro in response to retinoic acid, giving rise to a population of benign endoderm-like cells (END), termed PC13 END. PC13 EC and PC13 END cells exhibit growth cooperativity in co-culture, whereby the EC cells stimulate END cell proliferation and the END cells can support EC cell multiplication. The EC cells' stimulatory effect operates via soluble, diffusible factors which are also active on a range of fibroblast cell lines. END cells support the multiplication of EC cells plated at low density, via a multifactorial mechanism. Contact-dependent effects can operate in the absence of END cell metabolic activity, while contact-independent effects require the continuous presence of live END cells. It was observed that there was a variation in the ability of fibroblast cell lines to act as EC cell feeders. Similar interactive events may be important during the in vivo proliferation and differentiation of teratocarcinoma cells and their embryonic counterparts..

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The dexamethasone binding capacity of embryonal carcinoma cells and their differentiated derivatives was investigated. Manipulation of the embryonal carcinoma cell-culture conditions resulted in an unstable reversible expression of the glucocorticoid receptors. Stable expression of the receptors is observed when these cells are induced to differentiate. Cells grown under identical conditions were assayed for their ability to bind epidermal growth factor..

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AbstractThe different stages of the metastatic cascade present distinct metabolic challenges to tumour cells and an altered tumour metabolism associated with successful metastatic colonisation provides a therapeutic vulnerability in disseminated disease. We identify the aldo-keto reductase AKR1B10 as a metastasis enhancer that has little impact on primary tumour growth or dissemination but promotes effective tumour growth in secondary sites and, in human disease, is associated with an increased risk of distant metastatic relapse. AKR1B10High tumour cells have reduced glycolytic capacity and dependency on glucose as fuel source but increased utilisation of fatty acid oxidation. Conversely, in both 3D tumour spheroid assays and in vivo metastasis assays, inhibition of fatty acid oxidation blocks AKR1B10High-enhanced metastatic colonisation with no impact on AKR1B10Low cells. Finally, mechanistic analysis supports a model in which AKR1B10 serves to limit the toxic side effects of oxidative stress thereby sustaining fatty acid oxidation in metabolically challenging metastatic environments..

AbstractProfiling studies have revealed considerable phenotypic heterogeneity in cancer-associated fibroblasts (CAFs) present within the tumour microenvironment, however, functional characterisation of different CAF subsets is hampered by the lack of specific markers defining these populations. Here we show that genetic deletion of the Endo180 (MRC2) receptor, predominantly expressed by a population of matrix-remodelling CAFs, profoundly limits tumour growth and metastasis; effects that can be recapitulated in 3D co-culture assays. This impairment results from a CAF-intrinsic contractility defect and reduced CAF viability which, coupled with the lack of phenotype in the normal mouse, demonstrates that upregulated Endo180 expression by a specific, potentially targetable CAF subset is required to generate a supportive tumour microenvironment. Further, characterisation of a tumour subline selected via serial in vivo passage for its ability to overcome these stromal defects provides important insight into how tumour cells adapt to a non-activated stroma in the early stages of metastatic colonisation..