It may seem odd to call RU 486--the prescription-only abortion pill--pro-life, but it may be just that when it comes to cancer. Researchers at the University of California at Irvine reported last week that mifepristone, the active chemical in RU 486, can help thwart the growth of mammary tumors in mice caused by the mutant gene BRCA-1. More than half of women with this gene will develop breast or ovarian cancer by age 70.
In women with BRCA-1, the naturally occurring female hormone progesterone speeds the proliferation of mammary cells. "If we block the progesterone pathway using an antiprogesterone, it could prevent breast cancer," says Eva Lee, lead author of the study. That's exactly what mifepristone did for the experiment's mice, all of which had the BRCA-1 gene. At age 1, none of those treated with mifepristone had developed tumors. But all the untreated mice had tumors by the time they were 8 months old.
If reproducible in humans, the results of the study could pave the way toward preventing these cancers in women who have genetic predispositions. "Today women are advised to have frequent breast examinations and mammograms," Lee says. "But I hope that one day, if we have a more specific antiprogesterone, that we can use drugs for prevention.