Publications

Optimization of the imidazo[4,5-b]pyridine-based series of Aurora kinase inhibitors led to the identification of 6-chloro-7-(4-(4-chlorobenzyl)piperazin-1-yl)-2-(1,3-dimethyl-1H-pyrazol-4-yl)-3H-imidazo[4,5-b]pyridine (27e), a potent inhibitor of Aurora kinases (Aurora-A K(d) = 7.5 nM, Aurora-B K(d) = 48 nM), FLT3 kinase (K(d) = 6.2 nM), and FLT3 mutants including FLT3-ITD (K(d) = 38 nM) and FLT3(D835Y) (K(d) = 14 nM). FLT3-ITD causes constitutive FLT3 kinase activation and is detected in 20-35% of adults and 15% of children with acute myeloid leukemia (AML), conferring a poor prognosis in both age groups. In an in vivo setting, 27e strongly inhibited the growth of a FLT3-ITD-positive AML human tumor xenograft (MV4-11) following oral administration, with in vivo biomarker modulation and plasma free drug exposures consistent with dual FLT3 and Aurora kinase inhibition. Compound 27e, an orally bioavailable dual FLT3 and Aurora kinase inhibitor, was selected as a preclinical development candidate for the treatment of human malignancies, in particular AML, in adults and children.

The objective of the ONCODEATH consortium [EU Research Consortium "ONCODEATH" (2006-2010)] was to achieve sensitization of solid tumor cells to death receptor related therapies using rational mechanism-based drug combinations of targeted therapies. In this collaborative effort, during a period of 42 mo, cell and animal model systems of defined oncogenes were generated. Exploitation of generated knowledge and tools enabled the consortium to achieve the following research objectives: (1) elucidation of tumor components which confer sensitivity or resistance to TRAIL-induced cell death; (2) providing detailed knowledge on how small molecule Hsp90, Aurora, Choline kinase, BRAF inhibitors, DNA damaging agents, HDAC and DNMT inhibitors affect the intrinsic apoptotic amplification and execution machineries; (3) optimization of combined action of TRAIL with these therapeutics for optimum effects with minimum concentrations and toxicity in vivo. These findings provide mechanistic basis for a pharmacogenomic approach, which could be exploited further therapeutically, in order to reach novel personalized therapies for cancer patients.

Acquired resistance to selective FLT3 inhibitors, is an emerging clinical problem in the treatment of FLT3-ITD+ acute myeloid leukaemia (AML). The paucity of valid pre-clinical models has limited investigations to determine the mechanism of acquired therapeutic resistance, thereby limiting the development of effective treatments. We generated selective FLT3 inhibitor-resistant cells by treating the FLT3-ITD+ human AML cell line MOLM-13 in vitro with the FLT3-selective inhibitor MLN518, and validated the resistant phenotype in vivo and in vitro. The resistant cells, MOLM-13-RES, harboured a new D835Y tyrosine kinase domain (TKD) mutation on the FLT3-ITD+ allele. Acquired TKD mutations, including D835Y, have recently been identified in FLT3-ITD+ patients relapsing after treatment with the novel FLT3 inhibitor, AC220. Consistent with this clinical pattern of resistance, MOLM-13-RES cells displayed high relative resistance to AC220 and Sorafenib. Furthermore, treatment of MOLM-13-RES cells with AC220 lead to loss of the FLT3 wild type allele and duplication of the FLT3-ITD-D835Y allele. Our FLT3-Aurora kinase inhibitor, CCT137690, successfully inhibited growth of FLT3-ITD-D835Y cells in vitro and in vivo, suggesting that dual FLT3-Aurora inhibition may overcome selective FLT3 inhibitor resistance, in part due to inhibition of Aurora kinase, and may benefit patients with FLT3-mutated AML.

Aurora kinases regulate key stages of mitosis including centrosome maturation, spindle assembly, chromosome segregation, and cytokinesis. Aurora A and B kinase overexpression has also been associated with various human cancers, and as such, they have been extensively studied as novel antimitotic drug targets. Here, we characterize the Aurora kinase inhibitor CCT137690, a highly selective, orally bioavailable imidazo[4,5-b]pyridine derivative that inhibits Aurora A and B kinases with low nanomolar IC(50) values in both biochemical and cellular assays and exhibits antiproliferative activity against a wide range of human solid tumor cell lines. CCT137690 efficiently inhibits histone H3 and transforming acidic coiled-coil 3 phosphorylation (Aurora B and Aurora A substrates, respectively) in HCT116 and HeLa cells. Continuous exposure of tumor cells to the inhibitor causes multipolar spindle formation, chromosome misalignment, polyploidy, and apoptosis. This is accompanied by p53/p21/BAX induction, thymidine kinase 1 downregulation, and PARP cleavage. Furthermore, CCT137690 treatment of MYCN-amplified neuroblastoma cell lines inhibits cell proliferation and decreases MYCN protein expression. Importantly, in a transgenic mouse model of neuroblastoma that overexpresses MYCN protein and is predisposed to spontaneous neuroblastoma formation, this compound significantly inhibits tumor growth. The potent preclinical activity of CCT137690 suggests that this inhibitor may benefit patients with MYCN-amplified neuroblastoma.

The design of targeted therapeutic strategies for cancer has largely been driven by the identification of tumor-specific genetic changes. However, the large number of genetic alterations present in tumor cells means that it is difficult to discriminate between genes that are critical for maintaining the disease state and those that are merely coincidental. Even when critical genes can be identified, directly targeting these is often challenging, meaning that alternative strategies such as exploiting synthetic lethality may be beneficial. To address these issues, we have carried out a functional genetic screen in >30 commonly used models of breast cancer to identify genes critical to the growth of specific breast cancer subtypes. In particular, we describe potential new therapeutic targets for PTEN-mutated cancers and for estrogen receptor-positive breast cancers. We also show that large-scale functional profiling allows the classification of breast cancers into subgroups distinct from established subtypes. SIGNIFICANCE: Despite the wealth of molecular profiling data that describe breast tumors and breast tumor cell models, our understanding of the fundamental genetic dependencies in this disease is relatively poor. Using high-throughput RNA interference screening of a series of pharmacologically tractable genes, we have generated comprehensive functional viability profiles for a wide panel of commonly used breast tumor cell models. Analysis of these profiles identifies a series of novel genetic dependencies, including that of PTEN-null breast tumor cells upon mitotic checkpoint kinases, and provides a framework upon which additional dependencies and candidate therapeutic targets may be identified.

Non-invasive assessment of biomarker modulation is important for evaluating targeted therapeutics, particularly in pediatrics. The plasma inhibitory activity (PIA) assay is used clinically to assess FLT3 inhibition ex vivo and guide dosing. AT9283 is a novel Aurora kinase inhibitor with secondary activity against FLT3 and ABL. We adapted the PIA assay to simultaneously detect inhibition of Aurora and FLT3 in AML, and Aurora and ABL in CML by AT9283. Furthermore, we optimized the assay for children, where limited blood volumes are available for pharmacodynamic studies. Simultaneously detecting multiple kinase inhibition may identify important mechanisms of action for novel anti-leukemic drugs.

Lead optimization studies using 7 as the starting point led to a new class of imidazo[4,5-b]pyridine-based inhibitors of Aurora kinases that possessed the 1-benzylpiperazinyl motif at the 7-position, and displayed favorable in vitro properties. Cocrystallization of Aurora-A with 40c (CCT137444) provided a clear understanding into the interactions of this novel class of inhibitors with the Aurora kinases. Subsequent physicochemical property refinement by the incorporation of solubilizing groups led to the identification of 3-((4-(6-bromo-2-(4-(4-methylpiperazin-1-yl)phenyl)-3H-imidazo[4,5-b]pyridin-7-yl)piperazin-1-yl)methyl)-5-methylisoxazole (51, CCT137690) which is a potent inhibitor of Aurora kinases (Aurora-A IC(50) = 0.015 +/- 0.003 muM, Aurora-B IC(50) = 0.025 muM, Aurora-C IC(50) = 0.019 muM). Compound 51 is highly orally bioavailable, and in in vivo efficacy studies it inhibited the growth of SW620 colon carcinoma xenografts following oral administration with no observed toxicities as defined by body weight loss.

Aurora kinases are a family of protein kinases that have a key role in multiple stages of mitosis. Over-expression of Aurora kinases, particularly Aurora A, has been demonstrated in a number of solid tumors and hematological malignancies. Not surprisingly, these serine/threonine kinases have become attractive small molecule targets for cancer therapeutics, with several inhibitors currently in early-phase clinical trials. A small number of compounds developed to date are highly selective for either Aurora A or Aurora B, while the majority inhibit both Aurora A and Aurora B; many of these compounds exhibit 'off-target' inhibition of kinases such as ABL, JAK2 and FLT3. It is currently unclear whether the therapeutic activity of these compounds in leukemia is primarily due to selective Aurora or multi-kinase inhibition. The most promising application for Aurora kinase inhibitors to date appears to be in FLT3-mutated acute myeloid leukemia (AML) and imatinib-resistant chronic myeloid leukemia/Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia, particularly when caused by the T315I mutation. Here we review the growing body of evidence supporting the use of Aurora kinase inhibitors as effective agents for AML and Ph+ leukemias. Leukemia (2010) 24, 671-678; doi: 10.1038/leu.2010.15; published online 11 February 2010

The protein kinase Aurora-A is a major regulator of the cell cycle that orchestrates mitotic entry and is required for the assembly of a functional mitotic spindle. Overexpression of Aurora-A has been strongly linked with oncogenesis and this has led to considerable efforts at therapeutic targeting of the kinase activity of this protein. However, the exact mechanism by which Aurora-A promotes oncogenesis remains unclear. Here, we show that Aurora-A modulates the repair of DNA double-strand breaks (DSBs). Aurora-A expression inhibits RAD51 recruitment to DNA DSBs, decreases DSB repair by homologous recombination and sensitizes cancer cells to PARP inhibition. This impairment of RAD51 function requires inhibition of CHK1 by Polo-like kinase 1 (PLK1). These results identify a novel function of Aurora-A in modulating the response to DNA DSB that likely contributes to carcinogenesis and suggest a novel therapeutic approach to the treatment of cancers overexpressing this protein.

PPM1D (protein phosphatase magnesium-dependent 1δ) maps to the 17q23.2 amplicon and is amplified in ∼8% of breast cancers. The PPM1D gene encodes a serine threonine phosphatase, which is involved in the regulation of several tumour suppressor pathways, including the p53 pathway. Along with others, we have recently shown that PPM1D is one of the drivers of the 17q23.2 amplicon and a promising therapeutic target. Here we investigate whether PPM1D is overexpressed when amplified in breast cancers and the correlations between PPM1D overexpression and amplification with clinicopathological features and survival of breast cancer patients from a cohort of 245 patients with invasive breast cancer treated with therapeutic surgery followed by adjuvant anthracycline-based chemotherapy. mRNA was extracted from representative sections of tumours containing >50% of tumour cells and subjected to TaqMan quantitative real-time PCR using primers for PPM1D and for two housekeeping genes. PPM1D overexpression was defined as the top quartile of expression levels. Chromogenic in situ hybridization with in-house-generated probes for PPM1D was performed. Amplification was defined as >50% of cancer cells with >5 signals per nucleus/large gene clusters. PPM1D overexpression and amplification were found in 25 and 6% of breast cancers, respectively. All cases harbouring PPM1D amplification displayed PPM1D overexpression. PPM1D overexpression was inversely correlated with expression of TOP2A, EGFR and cytokeratins 5/6 and 17. PPM1D amplification was significantly associated with HER2 overexpression, and HER2, TOP2A and CCND1 amplification. No association between PPM1D gene amplification and PPM1D mRNA overexpression with survival was observed. In conclusion, PPM1D is consistently overexpressed when amplified; however, PPM1D overexpression is more pervasive than gene amplification. PPM1D overexpression and amplification are associated with tumours displaying luminal or HER2 phenotypes. Co-amplification of PPM1D and HER2/TOP2A and CCND1 are not random events and may suggest the presence of a 'firestorm' genetic profile.

Co-crystallisation of the imidazo[1,2-a]pyrazine derivative 15 (3-chloro-N-(4-morpholinophenyl)-6-(pyridin-3-yl)imidazo[1,2-a]pyrazin-8-amine) with Aurora-A provided an insight into the interactions of this class of compound with Aurora kinases. This led to the design and synthesis of potent Aurora-A inhibitors demonstrating up to 70-fold selectivity in cell-based Aurora kinase pharmacodynamic biomarker assays.

Mutations in protein kinases can drive cancer through alterations of the kinase activity or by uncoupling kinase activity from regulation. Changes to protein expression in Aurora A, a mitotic Ser/Thr kinase, are associated with the development of several human cancers, but the effects of somatic cancer-associated mutations have not been determined. In this study we show that Aurora A kinase activity is altered in different ways in three somatic cancer-associated mutations located within the catalytic domain; Aurora A(V174M) shows constitutively increased kinase activity, Aurora A(S155R) activity is decreased primarily due to misregulation, and Aurora A(S361*) activity is ablated due to loss of structural integrity. These alterations suggest vastly different mechanisms for the role of these three mutations in human cancer. We have further characterized the Aurora A(S155R) mutant protein, found that its reduced cellular activity and mislocalization are due to loss of interaction with TPX2, and deciphered the structural basis of the disruption at 2.5 A resolution. Previous studies have shown that disruption of the Aurora A/TPX2 interaction results in defective spindles that generate chromosomal abnormalities. In a panel of 40 samples from microsatellite instability-positive colon cancer patients, we found one example in which the tumor contained only Aurora A(S155R), whereas the normal tissue contained only wild-type Aurora A. We propose that the S155R mutation is an example of a somatic mutation associated with this tumor type, albeit at modest frequency, that could promote aneuploidy through the loss of regulated interactions between Aurora A and its protein partners.

The PPM1D gene is aberrantly amplified in a range of common cancers and encodes a protein phosphatase that is a potential therapeutic target. However, the issue of whether inhibition of PPM1D in human tumour cells that overexpress this protein compromises their viability has not yet been fully addressed. We show here, using an RNA interference (RNAi) approach, that inhibition of PPM1D can indeed reduce the viability of human tumour cells and that this effect is selective; tumour cell lines that overexpress PPM1D are sensitive to PPM1D inhibition whereas cell lines with normal levels are not. Loss of viability associated with PPM1D RNAi in human tumour cells occurs via the activation of the kinase P38. To identify chemical inhibitors of PPM1D, a high-throughput screening of a library of small molecules was performed. This strategy successfully identified a compound that selectively reduces viability of human tumour cell lines that overexpress PPM1D. As expected of a specific inhibitor, the toxicity to PPM1D overexpressing cell lines after inhibitor treatment is P38 dependent. These results further validate PPM1D as a therapeutic target and identify a proof-of-principle small molecule inhibitor.

We have identified that Aurora-A activates NF-kappaB via IkappaBalpha phosphorylation. Here, we analysed different human tumour cell types for their NF-kappaB activity. We found that there is an association between cell resistance to chemotherapeutic agents and NF-kappaB activation. A549 human lung adenocarcinoma cells and SKOV3 human ovarian cancer cells have high levels of NF-kappaB and are resistant to cytotoxic agents such as adriamycin and VP-16 (etoposide). We also found that in A549 and SKOV3 cells treated with a small molecule inhibitor towards Aurora kinases, the NF-kappaB activity was downregulated and the efficacy of cytotoxic drugs was enhanced. In addition, the transcriptional targets Bcl-XL and Bcl-2 were downregulated. This study provides evidence for a potential mechanism of chemoresistance and may be useful for the enhancement of certain chemotherapeutics regimens.

The Aurora-A/STK15 gene encodes a kinase that is frequently amplified in cancer. Overexpression of Aurora-A in mammalian cells leads to centrosome amplification, genetic instability, and transformation. In this study, we show that Aurora-A activates nuclear factor-kappaB (NF-kappaB) via IkappaBalpha phosphorylation. Inhibition of endogenous Aurora-A reduces tumor necrosis factor alpha (TNFalpha)-induced IkappaBalpha degradation. We analyzed primary human breast cancers, and 13.6% of samples showed Aurora-A gene amplification, all of which exhibited nuclear localization of NF-kappaB. We propose that this subgroup of patients with breast cancer might benefit from inhibiting Aurora-A. We also show that down-regulation of NF-kappaB via Aurora-A depletion can enhance cisplatin-dependent apoptosis. These data define a new role for Aurora-A in regulating IkappaBalpha that is critical for the activation of NF-kappaB-directed gene expression and may be partially responsible for the oncogenic effect of Aurora-A when the gene is amplified and overexpressed in human tumors.

A hit generation and exploration approach led to the discovery of 31 (2-(4-(6-chloro-2-(4-(dimethylamino)phenyl)-3H-imidazo[4,5-b]pyridin-7-yl)piperazin-1-yl)-N-(thiazol-2-yl)acetamide), a potent, novel inhibitor of Aurora-A, Aurora-B and Aurora-C kinases with IC(50) values of 0.042, 0.198 and 0.227microM, respectively. Compound 31 inhibits cell proliferation and has good microsomal stability.

The Aurora-A/STK15 gene encodes a kinase that is frequently amplified in cancer. However, it is not clear what role this plays in the development of cancer since little is known about its biochemical targets. We have showed that Aurora-A induces phosphorylation of IkappaBa, thereby mediating its degradation. Loss of IkappaBa leads to activation of NF-kappaB target gene transcription. We analysed primary human breast cancers and 13.6% of samples showed Aurora-A gene amplification all of which exhibited nuclear localisation of NF-kappaB. We propose that this subgroup of breast cancer patients might benefit from inhibiting Aurora-A. Further analysis of different human tumour cell types for their NF-kappaB activity have showed that there is an association between cell resistance to chemotherapeutic agents and NF-kappaB activation. A549 human lung adenocarcinoma cells and SKOV3 human ovarian cancer cells have high levels of NF-kappaB and are resistant to cytotoxic agents such as adriamycin and VP-16 (etoposide). We also found that in A549 and SKOV3 cells treated with a small molecule inhibitor towards Aurora kinases, the NF-kappaB activity was downregulated and the efficacy of cytotoxic drugs was enhanced. In addition, the transcriptional targets Bcl-XL and Bcl-2 were downregulated. These findings have important implications for cancer chemotherapy. Aurora-A-inhibition enhances the efficacy of chemotherapeutic agents and reverses acquired resistance resulting from the activation of NF-kappaB. Consequently, preventing NF-kappaB activation by inhibition of Aurora-A, may provide a valuable enhancement to specific chemotherapeutic regimens.

The cyclin-dependent kinase (CDK) inhibitor seliciclib (R-roscovitine, CYC202) shows promising antitumor activity in preclinical models and is currently undergoing phase II clinical trials. Inhibition of the CDKs by seliciclib could contribute to cell cycle arrest and apoptosis seen with the drug. However, it is common for drugs to exert multiple effects on gene expression and biochemical pathways. To further our understanding of the molecular pharmacology of seliciclib, we employed cDNA microarrays to determine changes in gene expression profiles induced by the drug in HT29 human colon cancer cells. Concentrations of seliciclib were used that inhibited RB phosphorylation and cell proliferation. An increase in the mRNA expression for CJUN and EGR1 was confirmed by Western blotting, consistent with activation of the ERK1/2 MAPK pathway by seliciclib. Transcripts of key genes required for the progression through mitosis showed markedly reduced expression, including Aurora-A/B (AURK-A/B), Polo-like kinase (PLK), cyclin B2 (CCNB2), WEE1 and CDC25C. Reduced expression of these mitotic genes was also seen at the protein level. siRNA-mediated depletion of Aurora-A protein led to an arrest of cells in the G(2)/M phase, consistent with the effects of seliciclib treatment. Inhibition of mitotic entry following seliciclib treatment was indicated by a reduction of histone H3 phosphorylation, which is catalyzed by Aurora-B, and by decreased expression of mitotic markers, including phospho-protein phosphatase 1 alpha. The results indicate a potential mechanism through which seliciclib prevents entry into mitosis. Gene expression profiling has generated hypotheses that led to an increase in our knowledge of the cellular effects of seliciclib and could provide potential pharmacodynamic or response biomarkers for use in animal models and clinical trials.

The Aurora family of serine/threonine kinases is important for the regulation of centrosome maturation, chromosome segregation, and cytokinesis during mitosis. Overexpression of Aurora kinases in mammalian cells leads to genetic instability and transformation. Increased levels of Aurora kinases have also been linked to a broad range of human tumors. Here, we describe the properties of CCT129202, a representative of a structurally novel series of imidazopyridine small-molecule inhibitors of Aurora kinase activity. This compound showed high selectivity for the Aurora kinases over a panel of other kinases tested and inhibits proliferation in multiple cultured human tumor cell lines. CCT129202 causes the accumulation of human tumor cells with >or=4N DNA content, leading to apoptosis. CCT120202-treated human tumor cells showed a delay in mitosis, abrogation of nocodazole-induced mitotic arrest, and spindle defects. Growth of HCT116 xenografts in nude mice was inhibited after i.p. administration of CCT129202. We show that p21, the cyclin-dependent kinase inhibitor, is induced by CCT129202. Up-regulation of p21 by CCT129202 in HCT116 cells led to Rb hypophosphorylation and E2F inhibition, contributing to a decrease in thymidine kinase 1 transcription. This has facilitated the use of 3'-deoxy-3'[(18)F]fluorothymidine-positron emission tomography to measure noninvasively the biological activity of the Aurora kinase inhibitor CCT129202 in vivo.

Chromosomal instability is one of the most common features of prostate cancer (PC), especially in advanced stages. Recent studies suggest that defects in mitotic checkpoints play a role in carcinogenesis. Lack of mitotic regulation induces aneuploidy in cancer cells acting thereafter as a driving force for malignant progression. Serine/threonine protein kinases of the Aurora genes family play an important throughout the entire cell cycle. In that Aurora B regulates chromosome segregation by ensuring the orientation of sister chromatids. As a consequence, the overexpression of Aurora B in diploid human cells NHDF induces the appearance of multinucleate cells.

Aurora-A is an important regulator of mitosis and is frequently amplified in human cancer. Ectopic expression of Aurora-A in mammalian cells induces centrosome amplification, genomic instability and transformation. A common genetic variant in Aurora-A (F31I) is preferentially amplified and is associated with the occurrence and the status of colon, oesophageal and breast cancers. Here we demonstrate that the N-terminal domain of Aurora-A Phe-31 variant exhibits an intrinsic ubiquitin ligase activity. Mutation of cysteines 8, 33 and 49 of Aurora-A abolishes the ubiquitin ligase activity of the protein. Aurora-A in a complex with UBE2N/MMS2 catalyses polyubiquitination of IkappaBalpha in vitro and in vivo.

Alterations in chromosome number (aneuploidy) are common in human neoplasias. Loss of mitotic regulation is believed to induce aneuploidy in cancer cells and act as a driving force during the malignant progression. The serine/theronine protein kinases of aurora family genes play a critical role in the regulation of key cell cycle processes. Aurora B mediates chromosome segregation by ensuring orientation of sister chromatids and overexpression of Aurora B in diploid human cells NHDF (normal human diploid fibroblast) induces multinuclearity. We analyzed Aurora B expression in human thyroid carcinomas. Cell lines originating from different histotypes showed an increase in Aurora B expression. Immunohistochemical analysis of archive samples showed a high expression of Aurora B in anaplastic thyroid carcinomas; conversely, Aurora B expression was not detectable in normal thyroid tissue. Real-time PCR analysis confirmed a strong expression of Aurora B in anaplastic thyroid carcinomas. The block of Aurora B expression induced by RNA interference or by using an inhibitor of Aurora kinase activity significantly reduced the growth of thyroid anaplastic carcinoma cells.

Aurora/Ipl1-related kinases are a conserved family of proteins that have multiple functions during mitotic progression. High levels of Aurora kinases are characteristic of rapidly dividing cells and tumours. Aurora B encodes a protein that associates with condensing chromatin, concentrates at centromeres, and then relocates onto the central spindle at anaphase. In this study the expression and the localisation of Aurora B throughout germinal epithelial progression in normal testis and its neoplastic counterpart were analysed. Immunocytochemistry and RT-PCR analysis of mouse germinal epithelium cells showed the presence of Aurora B in spermatogonia and occasionally in spermatocytes. Western blot analysis revealed the typical Aurora B isoform ( approximately 41 kDa) in the same cellular types. A similar distribution was observed in human testis by immunohistochemistry. Moreover, the distribution and the expression of Aurora B were investigated in neoplasms derived from germ cells. Surgical samples of seminomas were analysed, and a high percentage of Aurora B positive cells (51%) was detected; the expression of Aurora B was significantly related to the MIB-1 proliferation marker (R=0.816). The data presented here demonstrate that Aurora B expression occurs in spermatogonial division. Furthermore, our results indicate that the expression of Aurora B is a consistent feature of human seminomas.

STK15/Aurora2 is a centrosome-associated serine/threonine kinase, the protein levels and kinase activity of which rise during G2 and mitosis. STK15 overexpression induces tumorigenesis and is amplified in various human cancers and tumor cell lines. Thus, STK15 represents an important therapeutic target for small molecule inhibitors that would disrupt its activity and block cell proliferation. The availability of a robust and selective small molecule inhibitor would also provide a useful tool for identification of the potential role of STK15 in cell cycle regulation and tumor development. The authors report the development of a novel, fast, simple microplate assay for STK15 activity suitable for high-throughput screening. In the assay, gamma-(33)P-ATP and STK15 were incubated in a myelin basic protein (MBP)-coated FlashPlate(R) to generate a scintillation signal. The assay was reproducible, the signal-to-noise ratio was high (11) and the Z' factor was 0.69. The assay was easily adapted to a robotic system for drug discovery programs targeting STK15. The authors also demonstrate that STK15 is regulated by phosphorylation and the N-amino terminal domain of the protein. Treatment with phosphatase inhibitors (okadaic acid) or deletion of the N-amino terminal domain results in a significant increase in the enzymatic activity.

Linkage analysis and haplotype mapping in interspecific mouse crosses (Mus musculus x Mus spretus) identified the gene encoding Aurora2 (Stk6 in mouse and STK15 in human) as a candidate skin tumor susceptibility gene. The Stk6 allele inherited from the susceptible M. musculus parent was overexpressed in normal cells and preferentially amplified in tumor cells from F(1) hybrid mice. We identified a common genetic variant in STK15 (resulting in the amino acid substitution F31I) that is preferentially amplified and associated with the degree of aneuploidy in human colon tumors. The Ile31 variant transforms rat1 cells more potently than the more common Phe31 variant. The E2 ubiquitin-conjugating enzyme UBE2N was a preferential binding partner of the 'weak' STK15 Phe31 variant form in yeast two-hybrid screens and in human cells. This interaction results in colocalization of UBE2N with STK15 at the centrosomes during mitosis. These results are consistent with an important role for the Ile31 variant of STK15 in human cancer susceptibility.

Analysis of the functions of AP-1 transcription factor in cellular systems has shown its key role as a mediator of oncogenic signals. The employment of suitable animal model systems greatly facilitates the study of changes in the composition and activity of the AP-1 complex. Here, we have analysed the quantitative and qualitative changes of AP-1 at different stages of carcinogenesis in mouse skin cell lines, derived from tumours induced by chemical mutagens. The findings of this study suggest that elevated AP-1 DNA binding and transactivation activity characterize the carcinoma cell lines, most notably the highly malignant spindle carcinomas. In addition, increased amounts and post-translational modifications of c-Jun, Fra-1, Fra-2 and ATF-2 proteins account for a high percentage of the increased AP-1 activity. Remarkably, high levels of phosphorylated ATF-2 protein were detected in malignant cell lines, indicating a novel role of ATF-2 in tumour progression. c-Jun and ATF-2 proteins are phosphorylated by highly active JNK kinases present in tumour cells. Finally, our results indicate distinct functions for different AP-1 components in the promotion and progression of mouse skin tumours. Oncogene (2000) 19, 4011 - 4021.

Mice carrying an immunoglobulin enhancer (Emu-) linked c- or N-myc transgene develop fatal monoclonal or oligoclonal pre-B or B-cell lymphomas. This indicates that, beside the Emu-activated myc gene, additional genetic changes are required for tumor development. To trace these additional changes, we carried out a genome-wide search for loss of heterozygosity (LOH) and allelic imbalance (AI). This was done at 53 microsatellite markers in a panel of 34 lymphomas and four plasmacytomas from c- or N-myc transgene carrying (BALB/c x Mus spretus)F1 hybrids. An additional 43 lymphomas and three plasmacytomas from non-transgenic F1 mice were also investigated. Losses of one or more spretus-derived chromosome 9 markers were detected in 19 of 23 (83%) of the lymphomas, but in none of the four plasmacytomas that developed in N-myc F1 mice. No LOH-9 was found in any of the 11 lymphomas from Emu-c-myc F1 mice and only in 1 of 46 (2%) tumors derived from non-transgenic (BALB/c x spretus)F1 hybrid controls. These results suggest that a gene on spretus chromosome 9 confers resistance to the development of N-myc but not c-myc-induced lymphomas. AI of chromosome 15 markers (AI-15) was detected in 57 of 77 (74%) lymphomas and in 5 of 7 (72%) plasmacytomas, independently of the transgenic status and the mode of induction. All of the lymphomas and plasmacytomas with AI-15 revealed a relative gain of the spretus-derived D15Mit6 allele (located at 13.7 cM from the centromere), together with a gain of the BALB/c allele of the more distal (29.6 cM) D15Mit64 marker, suggesting somatic recombination. LOH in the region close to c-myc was detected in a proportion of tumors with AI-15. The observation of complex genetic alterations includes somatic recombination, AI and LOH involving chromosome 15 in tumors induced by a myc transgene. This indicates that at least two genes in addition to c-myc on this chromosome can be involved in lymphoma development.

Tumour formation relies on a complex combination of genetic and environmental factors. In particular, the contributions from inherited predisposition genes as well as carcinogens, for example from cigarettes or in the diet, are amongst the major contributors to tumorigenesis. Since the study of such processes in particularly difficult in human cancers, the availability of a well-defined model system is of obvious benefit. The mouse skin model of multistage carcinogenesis offers an excellent tool for the study of the target cells, the target genes and the biological events associated with neoplasia. In this system, tumorigenesis occurs in a series of defined stages, each of which is characterized by specific and reproducible alterations in genes such as H-ras, cyclin D1, p53 and p16INK4A. Additional changes occur in the production of, or response to, factors such as transforming growth factor beta (TGF beta). These genetic and biological alterations are mirrored in human tumours of epithelial origin. Hence, research into the general principles of tumour initiation, promotion and progression in the context of the mouse skin model is likely to prove valuable in the continual search for new methods for the diagnosis, prevention, and therapeutic treatment of human cancers.

A reverse transcription (RT)-polymerase chain reaction (PCR) method was used for detection of the RNA of hepatitis C virus (HCV) in 120 samples of sera from Crete, which were positive for HCV-specific antibodies, by ELISA and Western blot analyses. A segment of 255 bp, located in the most conserved region of the HCV genome (the 5' untranslated region, 5' UTR), was amplified. For the identification of sequence variation from the HCV-1 strain, twenty of these samples were sequenced and compared to prototype strain (HCV-1) according to current genotypic classification. We were able to identify fourteen of the twenty as type 1a (i.e. similar to the prototype), two as type 1b, two as type 3a and two as type 4a. These findings generally agree with the geographic distribution of the already identified genotypes, though 3a type has not been reported previously in Crete (Greece).

p16INK4a and p15INK4b are cell cycle regulators that specifically bind to and inhibit the cyclin D-dependent kinases, cdk4 and cdk6. Because these genes undergo frequent deletions and/or mutations in various human cancers, we examined the status and expression of the cognate mouse cdk inhibitors in a panel of 29 cell lines, as well as in 12 primary tumors, representing different stages of mouse skin carcinogenesis. Deletion of p16INK4a and/or p15INK4b was seen in 8 of 10 cell lines derived from spindle carcinomas, the most advanced stage of skin carcinogenesis. Five showed deletion of both genes, and three had independent deletions of p16INK4a or p15INK4b, but in those retaining p16INK4a, expression of the protein was not detected. By contrast, none of 19 more differentiated squamous cell lines exhibited such deletions. In several cases, primary tumor DNA was available, and two spindle tumors showed the same deletion pattern as observed in the corresponding cell lines. In apparent contrast, comparison of two clonally related squamous and spindle cell lines derived from a single carcinoma showed unusually high levels of p16INK4a and p15INK4b only in the invasive spindle cells. Therefore, deletion or altered regulation of p16INK4a and p15INK4b occur concomitantly with the loss of differentiation associated with the late spindle stage of tumor progression in mouse skin.

A combined reverse transcription-polymerase chain reaction (RT-PCR) method was employed for the detection of hepatitis C virus (HCV) RNA in serum from patients with chronic active hepatitis, with primers corresponding to the 5' non-coding region. The diagnosis was based on serological and biochemical methods and on liver biopsy. HCV-RNA was detected in 27 (90%) of 30 sera examined. The nucleotide sequence of PCR-amplified HCV cDNAs (256 bp) was determined from five specimens and heterogeneity varying between 0.58% and 2.89% among the clinical samples and the prototype HCV-1 was found.

Complete inactivation of the human retinoblastoma gene is believed to be an essential step in tumorigenesis of several different cancers. Using the plasmid pRbCAT2 that contains the Rb promoter region was tested for its ability to promote transcription of the bacterial chloramphenicol acetyltransferase (CAT) gene in a transient expression assay. This plasmid was co-transfected in a short term transfections with the plasmids pHO6T1 and pHO6N1 that contains the mutant and normal H-ras gene respectively, into the human cell line HeLa, by the calcium phosphate technique. It was found that the mutant H-ras gene enhances the activity of the Rb gene promoter in contrast to the normal H-ras gene that inhibits it. The expression of the CAT gene in stable clones of HeLa cells carrying the promoter of Rb gene after treatment with TPA and EGF respectively, was also investigated, whereas TPA enhanced, EGF had no effect on the activity of the Rb gene promoter.

The retinoblastoma (Rb) gene is associated with the pathogenesis of several types of human cancer, including retinoblastoma, osteosarcoma, soft tissue sarcomas, and lung, breast and bladder carcinomas. Loss of heterozygosity is a common mode in allelic inactivation of Rb and other tumor-suppressor genes. We investigated DNA from 15 human lung tumors for loss of heterozygosity of the Rb locus using a polymerase chain reaction (PCR) based restriction fragment length polymorphism assay. Of informative cases we found loss of heterozygosity in 2 out of 3 squamous cell carcinomas and 1 out of 2 adenocarcinomas of the lung. We also found structural rearrangements in two out of fourteen Hind III digested lung tumors examined at the 5' region of the human Rb gene using Southern blot hybridization analysis. Since these two tumors were classified as stage III it is possible that the alteration of Rb gene is involved in the progression of this type of cancer. Using specific primers for exons 15, 16, 21 and 22 of the Rb gene, we carried out amplification of these exons by polymerase chain reaction. None of these tumors showed a deletion of exons 15, 16, 21 and 22.

Examination of the nucleotide sequence of the retinoblastoma (Rb) promoter revealed the presence of a DNA region highly homologous to the recognition site for the cellular transcription factor AP-1. A pair of complementary oligonucleotides containing the AP-1 site was synthesized and used in gel retardation assays to determine the role of the AP-1 protein in the regulation of the Rb gene expression. Using nuclear extracts from Hela cells as well as from lung and bladder tumors, we found specific binding of the AP-1 protein to this oligonucleotide. This binding is elevated in Hela cells, in 10/13 lung and 3/8 bladder tumors as compared to adjacent normal tissue. These results suggest that AP-1 could be implicated in Rb gene transcriptional regulation through its interaction with the AP-1 binding site of the Rb gene promoter.

Only a minority of T cells at cell-mediated immune lesions are antigen specific. In the lesions of human autoimmune disease, such as the synovial membrane in rheumatoid arthritis, the T cells are activated as shown by a variety of phenotypic and functional changes including the expression of HLA-DR and the production of interleukin-6 (IL-6). The stimulatory pathway involved is unknown but does not seem to involve the T-cell receptor. Alternative pathways of activation which may be involved include the CD2 molecule. It is shown that the formation of sheep red blood cell (SRBC) rosettes with resting T cells from human peripheral blood, which is equivalent to CD2/LFA-3 binding, leads to the de novo transcription of the HLA-DR and IL-6 genes and the expression of HLA-DR on the surface of the T cells. There was no transcription of the interleukin-2 (IL-2) or the interleukin-2 receptor (IL-2R) genes and Tac expression was not seen. The rosetted T cells did not proliferate. These are all characteristics of T cells at chronic inflammatory sites. It is concluded that receptor-ligand interactions between CD2/LFA-3, which are expressed in increased amounts in the rheumatoid joint, may be one pathway by which antigen non-specific T cells are recruited as effector cells in lesions of human autoimmune disease.

55 patients suffering from stage III or IV carcinoma of cervix were treated with two pulses of neo-adjuvant chemotherapy prior to radical radiotherapy. 51% (26/51) had a partial response. The initial response to chemotherapy is associated with significantly better long-term survival. The 3-year survival of chemotherapy responders is 62% against 21% for non-responders (P = 0.009 log-rank test). To detect possible differences in oncogene expression in biopsy specimens taken from responding and non-responding patients, paraffin-fixed material was immunocytochemically stained for the expression of the protein products of ras, c-myc and c-jun proto-oncogenes. The frequency of oncogene expression was ras 80.4%, c-myc 45.1% and c-jun 39.2%. There was no statistically significant association between oncogene expression, time to local recurrence or development of metastases or survival.

The ras, Rb and p53 genes have been implicated in the development of human breast cancer. Qualitative or quantitative changes in the expression of the ras p21 may lead to cell transformation, and this has been previously demonstrated in breast cancer. Both the retinoblastoma protein (Rb1) and the p53 gene product appear to function as negative regulators of cell division. We have investigated the expression of ras p21, Rb1 and p53 proteins in human breast cancer patients immunohistochemically, and correlated the results with a range of clinical and pathological parameters. Ras p21 expression was elevated in 65 per cent and p53 in 23 per cent of cases. Rb1 was expressed in 58 per cent of breast cancer tissues and in 75 per cent of normal tissue. Only four patients were found to have loss of Rb1 expression and also overexpression of both p53 and ras gene products. No correlations were found between the expression of these three genes and menopausal status, histological types or tumour grade. However, a correlation was found between Rb1 loss of expression and tumour diameter (greater than 2 cms), and no lymph node metastasis. Also, a significantly higher number of p53 staining specimens were found to be overexpressing the ras gene. These results suggest that all three oncogenes are most likely involved in the development of breast cancer but that their role is complex.

Expression of the tumor suppressor gene p53 and the ras oncogene were examined in 46 tumor and nodal specimens of non-small cell lung cancer (NSCLC) using the antibodies p53 pAb 240 and ras Y13-259 respectively. p53 expression was elevated in 46% and ras p21 was over-expressed in 85% of the tumor specimens analyzed. Fifteen cases of benign lessions were also assessed for both ras p21 and p53 expression; all were found to have negative staining. p53 over-expression was found to correlate with a poor prognosis in both the tumor specimens (p<0.05) and in the nodal tissues (p<0.005). Ras p21 over-expression was found to be associated with survival (p<0.1) in both the tumor and the nodal specimens. Stage of the disease correlated with survival; similarly both p53 and ras p21 over-expression correlated with stage. No correlations were found with the pathological grade of the tumors nor with a history of smoking or duration of smoking. No K-ras mutations at codon 12 were observed in a further 15 NSCLC specimens analyzed. These results indicate that the p53 gene in particular plays a role in the stages of NSCLC.

We have employed an immunohistochemical analysis to study the ras p21 oncoprotein in a total of 41 brain tumors and 1 reactive gliosis. The tumors included 33 astrocytomas, 1 oligodendroglioma, 2 ependymomas, 1 neurilemmoma, 1 malignant meningioma, 1 neuroblastoma and 2 medulloblastomas. Our results indicate that elevated ras p21 expression is a common feature in a range of brain tumors. In particular, elevated ras p21 expression has been found in 18 out of 24 high grade astrocytomas (malignant astrocytomas and glioblastomas multiforme) compared to 3 out of 9 low grade (well differentiated astrocytomas) (P less than 0.05). These results suggest that ras p21 expression may be an important molecular marker of the malignant astrocytomas and glioblastomas multiforme.

In the present work, we studied the expression of the c-myc oncoprotein p-62 and the ras oncoprotein p-21 in the dermal cellular infiltrate of paraffin embedded skin specimens, obtained from patients suffering from Mycosis Fungoides and Sezary syndrome. Nineteen specimens from early stage Mycosis Fungoides, nineteen from advanced stage Mycosis Fungoides and four from Sezary syndrome were included in the study. The oncoprotein detection was achieved immunohistochemically, using the mouse monoclonal antibody myc 1-9E10 and the rat monoclonal antibody Y13-259 for p-62 and p-21 respectively. Increased detection of both p-62 and p-21 in atypic lymphoid cells was shown in advanced stages of Mycosis Fungoides (third stage plaques and tumors) as compared to early stages (premycotic erythema, second stage plaques). In advanced stages, however, the percentage of P-62+ atypic cells proved to be higher than that of p-21+ atypic lymphoid cells. The implication of increased p-62 and p-21 oncoprotein expression in the process of lymphomagenesis in cutaneous T-cell lymphomas is discussed.

The levels of AP-1 activity in human breast lesions and in adjacent normal tissue were studied by a gel retardation assay. A thirty nucleotide long consensus oligonucleotide to the adenovirus E3 gene AP-1 sequence (E3AP-1) was end labelled and reacted with nuclear extracts from breast lesions and adjacent normal tissue. A total of 20 tissue extracts (8 pairs of tumor and normal tissue from the same patient and 4 tumors) were examined. All 12 tumor tissues showed elevated levels of AP-1 as compared to the 8 normal tissues. These results suggest that the AP-1 transcription factor may play a role in breast neoplasia.