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New Prostate Cancer Gene Mutation Found

Identification of second mutation could someday lead to better screening and prevention

MONDAY, Jan. 21(HealthDayNews) -- An international study has identified a gene mutation found in men at high risk of prostate cancer.

Although the mutation was discovered in only a small number of cases, researchers suspect that it may play a role in the early stages of the disease. They also say that although this gene mutation doesn't answer all of the questions about prostate cancer, it provides another piece of the puzzle about how the disease develops.

It is the second time in a year that researchers have connected a gene mutation to prostate cancer.

An expert familiar with the findings says the discovery could someday give doctors the tools to screen for men at increased risk of the disease, and may point to new avenues in drug development.

The research appears in the February issue of the journal Nature Genetics.

The prostate is a small organ in the male reproductive tract, which produces a large percentage of the fluid that makes up semen. Prostate cancer, the early warning signs of which include difficult or painful urination or ejaculation, tends to occur in men over the age of 55 with a family history of the disease and a diet high in animal fats.

There is some evidence that black men are at greater risk of prostate cancer than other ethnic groups. Almost 189,000 American men develop prostate cancer every year, and 30,200 will die of the disease.

Previous studies had directed researchers toward the region of the first human chromosome as a possible location for a specific gene mutation related to prostate cancer.

After ruling out several other genes in the region, researchers in the United States, Finland and Sweden identified mutations in the ribonuclease L (RNASEL) gene. Normally, RNASEL regulates the growth, division and natural death of cells.

The researchers, led by John Carpten at the National Human Genome Research Institute in Bethesda, Md., studied DNA samples from 26 families affected by hereditary prostate cancer. Hereditary prostate cancer accounts for approximately 10 percent of all cases of the disease.

"We've identified mutations in two families that seem to inactivate the [RNASEL] protein," says Carpten. "This protein plays a very important role in programmed cell death."

The study also reports that the men who carry the RNASEL mutation seem to have more aggressive prostate cancer.

Carpten and his colleagues suspect that when the RNASEL gene is mutated, prostate cells lose their ability to die off, and cells start to accumulate.

"Every piece of that puzzle is an important piece," Carpten says. And, he adds, although other genetic factors, dietary influences and environmental conditions are also critical, "if you're born with this mutation, it makes you more likely to develop the disease, because the cells are already at a disadvantage."

Carpten says researchers could develop a diagnostic test for the mutated gene.

"The identification of this gene will ultimately allow us to prevent prostate cancer in families that have this particular gene," says Dr. Isaac Powell, an associate professor of urology at Wayne State University's Karmanos Cancer Institute, who is familiar with the study.

If a man tests positive for the mutation, he says, a doctor could recommend more frequent screening for prostate cancer.

But the findings could also lead to new drugs targeted against prostate cancer, Powell adds. "Hopefully, we will be able to devise biological ways to block the expression of the gene."

Carpten says the team now hopes to look for the RNASEL mutation and study its effects in a larger group of patients with hereditary prostate cancer.

Last year, Utah researchers, also reporting in Nature Genetics, said they had discovered another gene mutation tied to prostate cancer. That, too, was implicated in only a tiny number of cases, the researchers said, but at the time they suspected there could be as many as five or six genes responsible for the disease.

What to Do: To find out more about prostate cancer, visit the National Cancer Institute, the American Cancer Society or the CaPCure Web site.

SOURCES: Interviews with John Carpten, Ph.D., principal investigator, Cancer Genetics Branch, National Human Genome Research Institute, Bethesda, Md.; Isaac Powell, M.D., associate professor of urology, Karmanos Cancer Institute, Wayne State University, Detroit; February 2002 Nature Genetics
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