SAN DIEGO—Genetic analyses suggest that prostate cancer in African-American men is distinctly different as compared with European-American men, according to researchers at the National Cancer Institute (NCI) in Bethesda, Md. 


They found significant differences in the expression of numerous genes in tumor samples taken from the two groups. Many genes are related to inflammation and immune system regulation, suggesting that pathogens could be involved in racial differences that lead to tumor development. Some genes also are linked to cancer spread.

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Although further study is needed to confirm their hypothesis of possible viral involvement in prostate cancer, the researchers believe these novel findings may help explain why prostate cancer incidence and mortality are increased among African-American men.


“We don’t think the worse outcomes we see in African-American prostate cancer patients are due to issues of socioeconomic and sociodemographic difference alone,” said lead author Tiffany Wallace, PhD, a postdoctoral fellow in the Laboratory of Human Carcinogenesis at the NCI. “So we are trying to understand if differences in genetics and biology play a discernible role, and this study suggests they do.” She presented study findings here at the 2008 annual meeting of the American Association of Cancer Research.


Using microarray technology, she and her colleagues obtained gene expression profiles of primary prostate tumors taken from 33 African-American men and 36 European-American men. They also obtained samples of surrounding non-tumor prostate tissue from seven of the African-American men and 11 of the European-American men. The investigators then compared the combined tumor profiles with profiles from non-cancerous tissue.


Genes known to contribute to immunologic tolerance in tumors such as indoleamine 2,3-dioxygenase, HLA-E, and HLA-G were more highly expressed in the tumors of African-American men than European-American men. In addition, the re-searchers found a distinctive interferon signature in the prostate tumors of African-American men that suggest the possibility of viral involvement.


“Something is different in the tumor microenvironment between the groups of patients we studied and it has to do with tumor immunobiology,” Dr. Wallace said.


She said that these findings are important because they could help lead to improved therapies for African-American men with prostate cancer. She said that it may be that medical therapies could be tailored to a patient’s individual gene expression pattern.


“Understanding the differences in the immune response between these two patient groups really could help identify how these patients will respond to therapy and it may lead to the identification of targets that could be singled out for immunotherapy,” Dr. Wallace told Renal & Urology News.


“We really want to eliminate the health disparities that exist in prostate cancer. Therefore we need to better understand the predisposing factors that could be contributing to the immune responses we see in these men.”