Most breast cancers are hormone-receptor-positive. The hormone estrogen binds to hormone receptors and in so doing can promote the growth of hormone-receptor-positive breast cancers. Hormonal therapies used to treat breast cancer work by limiting this effect of estrogen on breast cancer cells. Tamoxifen and Faslodex (chemical name: fulvestrant) block the binding of estrogen to the receptor. The aromatase inhibitors, which include Arimidex (chemical name: anastrozole), Aromasin (chemical name: exemestane), and Femara (chemical name: letrozole), interfere with the body's ability to make estrogen. Some hormone-receptor-positive cancers will come back or grow during treatment with hormonal therapy. When this happens, doctors say that the cancer has become resistant to hormonal therapy.
The research reviewed in this story discovered a substance called TPBM, which blocks the gene signals that tell a breast cancer cell to grow when estrogen binds to estrogen hormone receptors. The researchers found that TPBM blocks those signals even in breast cancer cells that became resistant to treatment with the hormonal therapy tamoxifen. TPBM doesn't appear to have any effect on cells that don't have estrogen hormone receptors.
This is a potentially important discovery, since TPBM and substances like it could some day prove to be useful as a form of targeted therapy for hormone-receptor-positive breast cancers, especially those that have stopped responding to hormonal therapy. Much more research will need to be done before this possibility could become a reality. Still, research news like this offers hope that tomorrow will bring more and better treatment options for those affected by breast cancer.
Stay tuned to Breastcancer.org for the latest news on research that may lead to better ways to prevent, diagnose, and treat breast cancer.
NEW YORK (Reuters Health) - A team of U.S. scientists has identified a new family of compounds that block the ability of estrogen to stimulate the growth of breast cancer cells.
"The lead inhibitor is quite effective in breast cancer cells that are resistant to tamoxifen," Dr. David J. Shapiro noted at the Endocrine Society's annual meeting underway in San Francisco.
"We are hopeful that as we proceed with further development that these compounds may ultimately lead to therapeutics that are clinically useful against some breast cancers that are resistant to current therapies," added Shapiro, a biochemist at the University of Illinois at Urbana-Champaign.
Currently available treatment for breast cancer driven by estrogen either interfere with estrogen production (e.g., aromatase inhibitors such as letrozole) or block estrogen's ability to bind to estrogen receptors on breast cancer cells (e.g., tamoxifen).
"We targeted a different step in the pathway of estrogen action," Shapiro said, "one that is not targeted by current therapeutics" -- namely, the expression of genes within cell that are controlled by estrogen receptor activity and that contribute to cancer growth.
The researchers found that a compound called TPBM blocked the estrogen-dependent growth of human breast cancer cells that carried estrogen receptors -- even cells resistant to tamoxifen treatment. If cells did not carry estrogen receptors (i.e., ER negative), they were not affected.
"Even at very high concentrations, TPBM has no effect on ER-negative cells, so it is not toxic to these cells at all," Shapiro said. "This gives us a lot of confidence as we go to animal studies that TPBM will not damage human cells."
He noted that while tamoxifen therapy is effective initially, "in essentially all patients, the tumors eventually become resistant to tamoxifen and resume their growth." This fact "underscores the importance of identifying new classes of therapeutic agents that will act outside of the hormone-binding pocket on the estrogen receptor."
Breastcancer.org 7 East Lancaster Avenue, 3rd Floor Ardmore, PA 19003
Learn more about our commitment to your privacy
© 2009 Breastcancer.org - All rights reserved.
Breastcancer.org is a non-profit organization dedicated to providing information and community to those touched by this disease. Learn more about our commitment to providing complete, accurate, and private breast cancer information.
_tcm8-332386.jpg "wellness_dvd_promo")