Saturday, December 02, 2006

The Many Uses of Mifepristone (RU-486)

Reuters gets a mifepristone story right [almost]:

WASHINGTON (Reuters) - The chemical compound in the abortion pill RU-486 blocked formation in mice of breast tumors caused by a mutant gene blamed in many women's breast and ovarian cancers, researchers found.

The study, published on Thursday in the journal Science, suggests a potential new path to protect women genetically predisposed to these cancers by using drugs to interfere with a hormone called progesterone, the researchers said.

A team led by University of California at Irvine scientist Eva Lee found that the compound, mifepristone, prevented breast tumors by blocking progesterone in mouse breast tissue cells.

They said they found that progesterone, which is involved in the female reproductive cycle, stimulates the proliferation of breast cells carrying a gene linked to breast cancer, possibly feeding tumor growth.

Women with a mutated version of the gene, known as BRCA-1, face a much higher risk of breast and ovarian cancers. By age 70, more than half of them end up with one of the two types of cancer.

Some of these women opt to have their breasts or ovaries surgically removed to lower the risk. This study raises hope that they might have another option -- using drugs rather than surgery to guard against cancers linked to the mutated gene.

In its normal form, BRCA-1 protects against cancer, suppressing tumor formation by assisting cells to repair DNA damage that could lead to cancer-causing mutations.

In this study, the researchers focused on how mifepristone influences the way the mutated gene functions in tissue, using mice with the rodent version of the mutated gene.


Mice given mifepristone were tumor-free by the time they were a year old, while the mice that did not get it all developed tumors by the time they were 8 months old, the researchers found.

Progesterone stimulates the development of tumors when the mutated gene is present because it accelerates cell division, but mifepristone interfered with a process needed for progesterone to spur the division of cells, the study found.

"By targeting the progesterone receptor, it's very possible that we can prevent the breast cancer, especially in the high risk BRCA-1 area," Lee said in a telephone interview.

The good news is that the article manages to (a) point out the difference between mifepristone (RU-486) and Plan B, and (b) correctly identifies Plan B as "emergency contraception" (not the "morning after pill").

The bad news is that Reuters misses a perfectly good opportunity to educate the public about mifepristone's many other uses. Identifying mifepristone as the "abortion pill" is detrimental because it masks one key fact about this drug. Mifepristone's mechanism of action differs--it can terminate a pregnancy, or it can prevent one; it can act on uterine cells, or on brain cells--based on dosage/regimen.

Some of mifepristone's uses you might be familiar with are abortion, birth control, emergency contraception, and the treatment of endometriosis and uterine myoma (fibroids). Also neuroprotection. And here are some more.

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