Even when consideration is given to diet, lifestyle, or socioeconomic factors, the differences in the behavior of prostate cancer between the races remains unexplained. But collaborative research done at UC Davis School of Medicine and Medical Center, Howard University in Washington, D.C., and the Northern California Cancer Center in Union City, Calif., suggests that the difference in prostate cancer pathophysiology in African Americans may lie in altered expression of bcl-2, a gene that plays a central role in preventing cells from dying. In all cells, a series of genes plays an integrated role in allowing the cell to progress through the cell cycle, DNA replication, and cell division. At the same time, a separate set of genes, interrelated with those that govern the cell cycle, work to allow the cell to enter programmed cell death, or apoptosis, at the appropriate time. This can occur as a natural part of cell aging, or in response to DNA damage.
Cancers can grow either by an increase in proliferation, a decrease in apoptosis, or both.
In prostate cancer, the gene bcl-2 acts as a major block to cell death. In the Journal of Urology study, the researchers evaluated four markers of tumor aggressiveness in cancerous prostates removed from 43 black and 74 Caucasian men to determine which factors were related to racial differences. With the bcl-2 gene overexpressed, it causes prostate cancer cells to flourish when they would normally perish. And because the chances that a prostate cancer tumor will metastasize increases with tumor size, it makes sense that if programmed cell death is blocked, metastasis could occur earlier in the course of the disease. Yet, since this study helps to explain why cancers occur earlier and more aggressively in African American men, it also underscores the importance of screening measures in this ethnic group, says Jackson.