Abortion drug suppresses breast cancer gene-Study

A synthetic steroid compound used to induce abortion can also prevent breast cancer tumors, caused by a mutant gene, from growing, according to researchers at the University of California, Irvine.

In their research on mice that carried the mutated BRCA-1 gene, the researchers concluded that the compound, called RU-486 (common name for mifepristone) can block the hormone that helps certain cancer tumors grow.

The research published in the December 1 issue of journal Science revealed that by blocking the hormone progesterone in breast tissue cells, the drug can also prevent tumors from forming.

Cancer researcher Eva Lee and colleagues discovered that mice treated with mifepristone, an anti-progesterone compound, did not develop breast tumors by the time they reached one year of age, while all of 25 untreated mice developed tumors by eight months of age.

The third group of mice treated with a placebo had developed tumors by the age of 5.2 months, the study said.

“We found that progesterone plays a role in the development of breast cancer by encouraging the proliferation of mammary cells that carry a breast cancer gene,” said Eva Lee, who headed the study and is professor of developmental and cell biology and biological chemistry at UCI.

RU-486 is licensed as an oral drug that can terminate pregnancy by interfering with the action of progesterone and preventing the attachment of a fertilized ovum to the uterine wall. The drug blocks the receptors for progesterone, a hormone needed in the uterus to maintain a pregnancy.

Progesterone also increases the activities of milk-producing cells at the time of pregnancy. The same kind of rapid cell growth can be seen in non-pregnant women who have the BRCA1 mutation. More than 50 percent of women with the defective version of a tumor-suppressing BRCA-1 gene develop breast or ovarian cancer by the time they reach 70 years of age.

At present, some women diagnosed with the BRCA1 mutation opt to have their breasts or ovaries surgically removed to substantially reduce their risk.

This study, which was supported by the National Cancer Institute, the Breast Cancer Research Foundation and the Department of Defense, might lead to new alternatives for women with a high risk for developing breast cancer.

“We’re excited about this discovery and hope it leads to new options for women with a high risk for developing breast cancer,” said Eva Lee.

However, Lee does not suggest RU-486 as the best candidate for treating human as in addition to shutting down progesterone, it also binds with receptors involved in immunity and other important functions. A short term use of the drug to end a pregnancy is probably fine but the long term use can affect progesterone more precisely.

''All of us have to be cautious,'' said Lee. ''But I do think if there is a better anti-progesterone available, hopefully there will be other options in the future for these women.''