Silenced gene suggests greater risk, possible marker for African-Americans with prostate cancer

Steve Tokar:

Among African-Americans with prostate cancer, a tumor-suppressing gene called GSTP1 is inactivated at a rate 3.5 times higher than among Caucasians, according to a study conducted at the San Francisco VA Medical Center (SFVAMC).

"This could be one of the mechanisms for the higher incidence of prostate cancer in African-Americans compared to Caucasians," said Rajvir Dahiya, PhD, Director of the Urology Research Center at SFVAMC and the principle investigator of the study. "When tumor suppression activity goes down, the tumor progresses much faster."

In the United States, African-Americans have almost 1.7 times the incidence and mortality of prostate cancer compared to Caucasians (272 per 100,000 vs. 164 per 100,000, respectively).

Researchers found that the GSTP1 gene is temporarily inactivated, or "silenced," through the process of hypermethylation, in which methyl groups (CH3) replace hydrogen atoms (H) in cytosine, one of the four protein bases of the gene's DNA.

The study is the first to investigate and discover ethnic differences in GSTP1 hypermethylation between African-Americans, Caucasians, and Asians. It is being published in the August 20, 2005 issue of the International Journal of Cancer, currently available online.

The researchers noted that "in the African-American population, GSTP1 methylation is a particularly good biomarker" for prostate cancer, since it is more likely to indicate the presence of the disease than in other ethnic groups. Thus, for African-Americans, it is both a potential cause of disease and a tool for diagnosing it, according to Dahiya, who is also a professor of urology at the University of California, San Francisco (UCSF).

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