Monday, June 16, 2008

New gene shows promise in resistant breast cancer

Researchers have identified a new group of compounds that might one day be added to the armamentarium of therapies designed to fight estrogen-fueled breast cancer. The molecule, called TPBM, and related drugs may have a role in treating patients who have become resistant to other hormone-based therapies, such as tamoxifen.

There are a large number of people who have estrogen receptor-positive breast cancer who respond well to hormone therapy. Sometimes, after a number of years, the hormone therapy stops working. Then they are switched to something else. That works for a time before the cancer progresses.

Exactly what is happening in those cancer cells that they become resistant? Perhaps there is another mechanism that can be overcome and this could be one of them.

Some two-thirds of all breast cancers are estrogen receptor-positive and therefore respond to hormonal treatments such as tamoxifen or the newer aromatase inhibitors, letrozole and anastrozole. Tamoxifen works by blocking estrogen receptors on breast cancer cells, while aromatase inhibitors interfere with the body's ability to produce estrogen.

Many of the cancers in this category eventually become resistant to tamoxifen and, in some cases, tamoxifen may even turn the tables and start acting like estrogen, thereby fueling tumour growth and proliferation.

A new study was presented by researchers from the University of North Carolina, Chapel Hill, the University of Colorado Health Sciences Center, Denver, and the University of Illinois, Urbana-Champaign at the annual meeting of the Endocrine Society, in San Francisco.

Through extensive laboratory testing, they identified a group of compounds related to TPBM that interfered with estrogen's effect on breast cancer cells via a different pathway. The molecules work by affecting the way estrogen receptors interact with a woman's DNA.

TPBM has the advantage of being "highly specific" and therefore potentially much less likely to have any unwanted effects on other cells. It also works against tamoxifen when tamoxifen starts fueling tumour growth. The research is promising, but still preliminary at this stage.

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