(dailyRx)
Most breast cancers are fueled by the female hormone estrogen. In an interesting twist, scientists have discovered that a male hormone ignites breast tumor growth in some women.
Androgen, a hormone found in males, gives the marching orders for some breast cancer cells to kick into high growth gear. That’s what scientists at Dana-Farber Cancer Institute have discovered in a new study.
These findings will provide new targets for drug therapies in patients who don’t respond to other hormone-blocking medications including tamoxifen.
The study’s senior author, Myles Brown, M.D., says that not only has his team identified a new type of breast cancer that is driven by androgen and not estrogen, but they’ve found ways to block this mechanism or pathway.
Dr. Brown says these findings open the doors for women who don’t respond to standard therapies.
Estrogen receptor-positive or ER+ is the most common type of breast cancer, found in 70-75 percent of cases. Estrogen makes cancer cells grow and spread. Tamoxifen and other estrogen-blocking drugs known as aromatase inhibitors, such as Femara (letrozole), keep the hormone from doing its deadly work.
The rest of breast cancers are called ER-negative because they don’t have the estrogen receptors and don’t respond to these medications.
Scientists know that even ER+ breast tumors have androgen receptors, though it’s not understood how this hormone behaves in these cancers. Researchers think the androgen may boost the growth of cells that have the receptors for androgen but lack receptors for estrogen.
In this study, researchers found that five to 10 percent of breast cancers have receptors for androgen, but not estrogen. These patients also have too much of a protein called HER2 that divides rapidly when exposed to the male hormone, androgen.
Researchers uncovered the pathways, or how growth signals are transmitted. They found two proteins – WNT and HER2 – play key roles in this process.
Dr. Brown says that combination therapies that shut down these proteins or block the androgen receptor can be “effective anti-tumor agents” for women with this type of breast cancer.
The study was published the journal Cancer Cell.
Breast Cancer
In the United States, one out of every eight women will be diagnosed with breast cancer sometime in her life. In 2010, there were over 250,000 new cases of breast cancer in women, and the number is rising. While treatment is improving, almost 40,000 women still died from breast cancer during 2009. However, there are still 2.5 million women in the US who are survivors.
Breast cancer, like any other cancer, is malignant, uncontrolled growth of breast tissue, usually from the tissue that lines the milk ducts (ductal carcinoma) or the tissue that makes the milk (lobular carcinoma). When cancer has not invaded other parts of the breast, it is referred to as in situ. (ex. Ductal carcinoma in situ). Breast cancers are also defined by their genes and hormone sensitivity. Some grow in response to the presence of estrogen, and area called ER+. Others have specific genes that make the cancer more aggressive, such as the gene HER2. These are important distinctions that direct treatment and prognosis.