Oct. 12, 2010 -- Scientists have identified a gene that could help predict whether a breast cancer patient will respond to the drug tamoxifen.

A study published today in the British Journal of Cancer showed a potential link between the activity of a gene called BCAR4 and the likelihood that a breast cancer tumor will not respond to tamoxifen hormone therapy.

The study also found that the level of BCAR4 in a tumour was linked to a poor prognosis regardless of whether the patient received tamoxifen.

A Visual Guide to Breast Cancer
Breast Cancer and Hormone Therapy

Tamoxifen is a hormone treatment given after surgery. It was developed more than 30 years ago and is widely used to treat women with breast cancer.

Tamoxifen comes in tablet form and is given for about five years after surgery to help prevent the disease from returning.

Tamoxifen prevents estrogen from stimulating the growth of breast cancer cells, but some tumors can eventually develop resistance to the treatment, making the drug ineffective.
BCAR4 in Breast Cancer

The research looked into why this might happen by examining whether the BCAR4 gene is involved in tamoxifen resistance. Using samples from 280 breast cancer patients, the researchers found that tamoxifen had a weak, or limited effect, on tumors with a highly active BCAR4 gene.

Study researcher Ton van Agthoven, says in a news release: “We know that breast cancer cells have different ways to escape tamoxifen therapy. Now BCAR4 may be a promising target for development of new treatments.

“Preliminary results show that BCAR4 is only active in the cancer cells and not in normal adult tissues. Therefore, treatments which fight against BCAR4 may have limited side effects for the patient.”

Research into the genes that control how breast cancer responds to treatment will help doctors provide patients with the most effective treatment for their tumor as early as possible, increasing their chance of survival.

It could also lead to the development of new breast cancer drugs to target tumors with a specific genetic makeup.
Further Research

Julie Sharp, senior science information manager at Cancer Research UK, says in a news release, “These early results tell us more about why tamoxifen can stop working for some women. We need further research into the BCAR4 gene to decide if it could lead to better ways to treat patients.

“Understanding the makeup of a tumor can enable drugs to be tailored to individual patients, and this could potentially improve cancer survival in the long term. In the future, doctors may be able to use this type of information to match the best treatment to the patients most likely to benefit and avoid giving treatment that is less likely to be effective.”