Can men inherit risk for a uniquely male disease from their moms? New research raises that odd possibility. Scientists think they have found a gene that predisposes men to prostate cancer (search) in parts of a cell that come exclusively from mothers, who obviously don't have prostates.

The find gives scientists a different place to look for cancer genes, and it could help biologists better understand what causes prostate cancer, the most common type of tumor in America.

The work was reported at an American Association for Cancer Research meeting in Anaheim this week.

More than 99 percent of our genes are contained in the nucleus, but a very small number are in tiny structures called mitochondria, little energy factories in cells. Mitochondria (search) are inherited from mothers.

Dr. John Petros and others at Emory University in Atlanta analyzed tissue samples from about 260 prostate cancer patients and found abnormalities in a mitochondrial gene called CO1. The gene helps regulate whether harmful substances that can set the stage for cancer are produced in a cell. Researchers then examined the gene in around 50 healthy men.

They found the gene was abnormal in 12 percent of those with prostate cancer but in only one man without the disease.

"This is a significant difference," said Dr. William Sellers, a cancer genetics expert at Dana-Farber Cancer Institute in Boston who had no role in the study.

The Atlanta group also found a pattern of inheritance of mitochondrial genes that seems to predispose men to prostate and kidney cancer. These may someday give a way to screen for these diseases, Petros said.

Dr. Cornelia Polyak, another Dana-Farber scientist who was among the first to discover cancer-related mutations in mitochondria — a colon cancer gene in 1998 — said the Atlanta findings need to be verified by other studies.

But if true, "it would be very exciting," not just because of the oddity of the location of the gene but also because it may help biologists unravel what processes lead to prostate cancer and how to treat it, she said.

It also might help determine whether men with borderline-high PSA scores need treatment, Sellers said.

"The big thing we're trying to do now in prostate cancer is really focus on people at higher risk," and having a gene signature would allow development of a more accurate index of worry, he said.