DNA methylation is affected by age and environmental exposures. Abnormal DNA methylation is a sign of colorectal cancer.
In a comparison between black and white individuals, the right colon seems to age quicker in black people. According to results from a biopsy study, this could explain the higher frequency of right-side colon cancer among African Americans.
Read the original publication of this study here: [Racial Disparities in Epigenetic Aging of the Right vs. Left Colon]
This colon cancer study aimed to make comparative studies of racial differences in site-specific colonic tissue epigenetic aging, which are lacking.
Racial Disparities in Epigenetic Aging of the Right vs. Left Colon
The colon biopsy examples from 128 participants who underwent routine colorectal screening were examined.
DNA methylation levels in the right and left colon biopsy samples from the same patient were compared.
The Hovarth clock was used to assign epigenetic ages to the tissue samples. This estimates the age of tissue based on DNA methylation.
The epigenetic ages were as follows:
88 black participants, the right colon 1.51 years older than the left colon or 60.2% epigenetically older.
44 white participants, the right colon 1.93 years younger than the left colon or 70% epigenetically younger.
A distinctive pattern of DNA hypermethylation was discovered in the right colon of Black patients.
“Our results provide biological plausibility for the observed relative preponderance of right colon cancer and younger age of onset in African Americans as compared to European Americans,” comment the investigators.
“Side-specific colonic epigenetic aging may be a promising marker to guide interventions to reduce CRC [colorectal cancer] burden,” the authors said.
Further corroborating studies could clarify racial differences in the site predilection of colorectal cancers. It is still unclear if the higher epigenetic aging means a higher risk of colorectal cancer.
Other factors could be influencing the data. Such as 38% of black participants smoked vs. 15% of white participants. Also, the average age of black subjects was 56 years, vs. 62 years of white subjects. There were more black female patients than white female patients (67% vs. 58%), and the BMIs were higher in black participants (31kg/m2 vs. 28 kg/m2).
- Among the Black participants, almost 70% of differentially methylated positions in the right colon were hypermethylated, compared to less than half in the left colon.
- As the figures were so high genetic variation is a likely contributing factor of the DNA methylation differences in the black right colon.
- Further studies would be needed to rule out any variants to compare right and left colon methylation in black and white people.
You can read the original publication of this study here: [Racial Disparities in Epigenetic Aging of the Right vs. Left Colon]