A study that appears in the December issue of Science reports that a chemical compound called mifepristone present in the abortion pill may prevent breast tumors from developing. The compound has been found to prevent the growth of breast tumors caused by the mutant gene responsible for breast and ovarian cancers.

Mifepristone showed to prohibit progesterone, a hormone involved with the female reproductive cycle. Women who are diagnosed with BRCA 1 mutation often have their breasts or ovaries removed to reduce the risk of developing cancer.

Eva Lee, lead author of the study and professor of developmental cell biology and biological chemistry, says "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. Mifepristone can block that response. We're excited about this discovery and hope it leads to new options for women with a high risk for developing breast cancer".

BRCA 1 is widely studied by cancer geneticists because a mutated version of this gene significantly raises the possibility of breast or ovarian cancers. By age 70, more than 50 percent of women with the mutated gene with develop breast or ovarian cancer. The researchers studied mice with the BRCA 1 mutation. The mice that were treated with mifepristone, an anti-progesterone compound did not develop breast cancer by the time they reached one year of age. All of the untreated mice developed tumors by eight months of age.

The researchers found that progesterone encourages the development of cancer when the mutated BRCA 1 gene is present because it speeds up the division of cancer cells. Mifepristone was found to block a binding process that is necessary for progesterone to cause the cell division. The researchers feel that anti-progesterone therapy could provide women with an increased risk for breast cancer with more treatment options in the future.