People from African descent get colorectal cancer more often and at a younger than people with genetically a European background. The cause of this was not really understood. Now, an American study seems to have found an answer: biological aging.
De left and right half of the colon (respectively distal and proximal of the left colic flexure) seem to age at different speeds. This appears to be the case in healthy individuals of both African and European descent. However, there is a remarkable difference: In Africans the right side of the colon ages significantly faster, whereas in Europeans this happen at the left side.
The investigators made this determination by looking at epigenetic changes of the DNA in the colon. A unique pattern of hypermethylation was found in the colon tissue of most people with an African background. The right side of the colon of 88 African American people showed an epigenetic aging that corresponded with the right side being 1,51 years (95%CI 0.62-2.40; p=0.001) older. In European Americans the effect was opposite. Their right colon showed remarkable age deceleration compared to the left colon (19,3 years; 95%CI 0.65-3.21; p=0.004).
According to the investigators these findings could explain the relative preponderance of right-side colon neoplasia in African Americans. At the same time it offers an explanation why younger people of European descent develop lesions on the left side – the side that tends to age faster in that group.
These finding are supported by previously shown differences between the left and the right colon. Colic tumour proximal and distal of the splenic flexure should be considered as different clinical and biological entities. The different colon biology of people of African and European ancestry should be taken into account with the prognosis of the individual. Currently the results of the study are validated in independent patient cohorts.
Devall M, Sun X, Yuan F, et al. Racial Disparities in Epigenetic Aging of the Right vs Left Colon. J Natl Cancer Inst 2020; doi: 10.1093/jnci/djaa206.