Research Opens Door to New Drugs Countering Tamoxifen Resistance
30 August 2010 - Scientists in London have found a potential new way of boosting the effectiveness of the anti-breast cancer drug, tamoxifen.
The discovery, by Professor Clare Isacke and her team at the Breakthrough Breast Cancer Research Centre at the ICR, could open the door to new treatments for those who have developed a resistance to tamoxifen.
Tamoxifen is a hormone treatment and is given to most women for five years after they are first diagnosed with breast cancer to help prevent the disease recurring. Many breast cancers require oestrogen and progesterone to grow, and can be treated with drugs that block the effects of these female sex hormones, such as tamoxifen. Usually, Tamoxifen is prescribed to women who are ER positive, meaning that oestrogen receptors (ER) have been found on their breast cancer cells.
However, some breast cancers are resistant to the drug or can develop resistance over time, allowing the cancer to recur or continue growing. Professor Isacke’s study found that when a protein called RET is switched on, it can activate the oestrogen receptor in the absence of any oestrogen.
To confirm their findings from the laboratory, they took tissue samples from oestrogen positive breast cancer patients and found that they had increased levels of RET. They went on to show that reducing the levels of RET actually makes the breast cancer cells more sensitive to tamoxifen and more likely to die.
Professor Isacke’s discovery could lead to new drugs that counteract this resistance.
“We are very excited by these findings. Our challenge now is to work out how RET activates the oestrogen receptor so that we can develop new treatments for tamoxifen-resistant breast cancers,” Professor Isacke said.
