Racial and ethnic factors in the genetic pathogenesis of colorectal cancer.

Colorectal cancer can develop by two distinct pathogenic mechanisms: one involving chromosomal breakage and aneuploidy (called chromosomal instability) and one involving mutations at DNA micro-satellite sequences (termed micro-satellite instability). Relatively few reports consider these mechanisms of colorectal cancer development across racial or ethnic groups. Available data indicate a moderate increase in colorectal cancer risk among Ashkenazi Jews who have a mutational polymorphism at codon 1307 in the APC gene. In American blacks, there is evidence for a higher prevalence of right-sided colonic tumors and an earlier age of onset of colorectal cancer. In addition, blacks have the highest colon cancer incidence in the United States among ethnic groups and have poorer 5-year survival rates compared with whites. While some differences may be attributed to health care access and socioeconomic differences, these do not completely explain all the variances. In the chromosomal instability pathway, there are polymorphisms within the P53 gene that are more prevalent in blacks, but the significance of these polymorphisms is not fully known. Blacks are more likely to demonstrate micro-satellite instability in their tumors; however, the mechanism for this phenomenon in blacks is unexplored. Differences in diet among racial and ethnic groups and polymorphic variations in drug metabolizing or acetylation genes have not been adequately cataloged. Identification of genetic and environmental factors among racial and ethnic groups should offer some insights into the observed epidemiologic data and advance opportunities to better understand the control and development of colorectal cancer.