Any one of four DNA variants in a gene involved in mediating inflammation may significantly increase the risk of colon cancer in African Americans, according to the results of an ongoing study presented at the AACR annual meeting. The risk is even further heightened in African American men who have two copies of all four variants, the research team found.

The finding may provide some insight into the higher colon cancer incidence and mortality in African Americans seen over the past three decades when compared with Caucasians, according to Dr. Krista A. Zanetti, a Cancer Prevention Fellow, and Dr. Curtis C. Harris, chief of the Laboratory of Human Carcinogenesis in NCI's Center for Cancer Research (CCR).

Despite the small sample size of African American cases and controls, "These results are particularly robust," Dr. Zanetti said. The variants are single nucleotide polymorphisms (SNPs), which are places in the genome where a single unit of DNA may vary from one person to the next.

The team conducted a case-control study that included 261 individuals with colon cancer and 537 healthy individuals, all from the greater Baltimore area. Of these, African Americans represented 103 cases and 201 controls. In African Americans, four SNPs in the MBL2 gene increased the risk of colon cancer at least three- to fourfold compared with African Americans without the genetic variants. In African Americans with two copies of all four MBL2 variants, there was a nearly sixfold increased risk. These associations were not seen in Caucasians.

Additional studies are needed to clarify and validate these findings, Dr. Zanetti explained.