delGA (rs67491583) variant and colorectal cancer risk in an indigenous African population

A recent study showed a higher frequency of GA deletion at rs67491583 in African American colorectal cancer (CRC) patients compared to controls, suggesting a likely contribution of this allele to racial disparity in CRC risk predisposition. We conducted a pilot study in an indigenous African population to evaluate this potential CRC risk variant.

We collected epidemiological data and biological specimen from consenting consecutive CRC cases and controls presenting at the Oncology Clinic of University College Hospital, Ibadan from 2001 to 2007. We examined germline DNA for delGA by PCR-amplification of two overlapping fragments using standard primers. The products were directly sequenced using Applied Biosystems BigDye v3.1 sequencing chemistry and AB 13730 automatic DNA sequencer.

There were 45 cases and 45 controls of which genotyping was successful in 39 cases and 38 controls. There were 5 heterozygous and 2 homozygous GA deletions with frequency of 11.54% (9/78) among cases whereas there were 8 heterozygous and 1 homozygous GA deletions among controls with frequency of 13.15% (10/76). (p= 0.79, OR 0.88, 95% CI 0.34-2.28).

This study suggests that there is no association between the delGA (rs67491583) variant and CRC risk in this indigenous African population. However our sample size was small and the participants were not ethnically homogenous. Further studies are required to evaluate this marker in African CRC.