ovarian cancer : Stem cells help ovarian tumors persist

WASHINGTON (Reuters) - Primitive cells that resemble stem cells may help some ovarian cancer tumors linger and recur in the body, but it may be possible to subdue them, U.S. researchers reported on Tuesday.

The findings build on other studies that show leukemia, breast, brain and other tumors have so-called side population cells that resemble the healthy stem cells found elsewhere in the body.

"Cancer stem cells, like somatic stem cells, are thought to be capable of unlimited self-renewal and proliferation," Dr. Patricia Donahoe of Massachusetts General Hospital and Harvard Medical School and colleagues wrote in their report, published in the Proceedings of the National Academy of Sciences.

They found these stem cells, which act as a kind of master cell, first in batches of ovarian tumor cells taken from mice. They then identified similar cells in human cancer cells.

When injected into mice these side-population cells formed tumors -- but their growth was slowed by a naturally produced compound called Mullerian Inhibiting Substance.

If the cells could be identified in human ovarian cancer patients, they might be used to assess a woman's chances of recovery, and, eventually, to find ways to better treat her cancer, Donahoe's team said.

Ovarian cancer is deadly, and is diagnosed in 22,000 women in North America per year, killing 16,000. More than 70 percent of women die of ovarian cancer within five years.

Usually treatment appears to be successful but the tumors come back. "The majority of patients who respond to primary chemotherapy ultimately develop recurrent, usually drug-resistant, disease that is conceivably due to the ability of ovarian cancer stem cells to escape these drugs," the researchers wrote.

Donahoe's team said their study suggests there may be a way to find these latent tumor cells and test new drugs to kill them -- maybe even Mullerian Inhibiting Substance.


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