Prostate cancer immunobiology may explain aggressive phenotype in black men

February 14, 2008

NEW YORK (Reuters Health) - Racial differences in the incidence and mortality rates of prostate cancer appear to be driven by distinct patterns of gene expression in the tumor microenvironment, scientists report in the February 1 issue of Cancer Research.

"The gene expression profiles of prostate tumors indicate prominent differences in tumor immunobiology between African-American and European-American men," state Dr. Stefan Ambs, from the National Cancer Institute in Bethesda, Maryland, and his colleagues.

Using microarray technology, the research team performed genome-wide gene expression profiling in prostate tumors from 33 black men and 36 white men with localized disease. The two groups were similar in age, pathologic stage, and Gleason score.

Previously identified diagnostic and prognostic marker genes for prostate cancer did not differ significantly between groups. However, the investigators identified 162 transcripts that were differently expressed. Most of the involved genes were more highly expressed in tumors from African-American patients.

Further analysis showed that differently expressed genes clustered in biological processes "associated with immune response, defense response, antigen presentation, B-cell/T-cell function, cytokine signaling, chemotaxis, and inflammatory response."

Furthermore, several known metastasis-promoting genes were more highly expressed in tumors from black men than in those from white men.

The differences in gene expression profiles "are not likely to be limited to prostate cancer, or to the contrast between African-Americans and European-Americans," Dr. Ambs told Reuters Health.

"We are currently studying those differences in breast cancer and are finding differences reminiscent of those in prostate cancer," he said. "Again, there seem to be differences in tumor immunobiology."

"I also believe there could be differences in tumor biology across the various race/ethnic groups in the U.S., and some of those may be causatively linked to survival health disparities," the researcher added.

Although their findings are preliminary and need follow-up, Dr. Ambs advises clinicians to be alert to the possibility that "the response to certain therapies could be different between race/ethnic groups."