ABSTRACT
Physical activity reduces risk of colon cancer by 20-30%. Aberrant methylation patterns are common epigenetic alterations in colorectal adenomas, and cancers and play a role in cancer initiation and progression. Alterations identified in normal colon tissue represent apotential 'field cancerization' process, where normal colon is primed for carcinogenesis. Here, we investigate methylation patterns in three genes -Ena/VASP-like (EVL), (CDKN2A (p14, ARF)), and Oestrogen Receptor-1 (ESR1)- in normal colon tissue collected at baseline and 12 months from 202 sedentary men and women, 40-75 years, enrolled in a randomized controlled trial testing an exercise intervention vs. control (http://clinicaltrials.gov/show/NCT00668161). Participants were randomized to moderate-to-vigorous intensity exercise, 60 minutes/day, 6 days/week for 12 months, or usual lifestyle. Sigmoid colon biopsies were obtained at baseline and 12-months, DNA extracted, and bisulphite converted. Droplet digital methylation-specific PCR was performed for EVL, p14ARF, and ESR1. Generalized estimating equations modification of linear regression was used to model relationships between intervention effects and gene methylation levels, adjusting for possible confounders.There were no statistically significant differences between methylation patterns at 12-months between exercisers and controls. ESR1 methylation patterns differed by sex: women -10.58% (exercisers) +11.10% (controls); men +5.54% (exercisers), -8.16% (controls) (P=0.05), adjusting for BMI and age. There were no statistically significant changes in methylation patterns in any gene stratified by change in VO2max or minutes/week of exercise.While no statistically significant differences were found in gene methylation patterns comparing exercises vs. controls, 12-month exercise effects on ESR1 methylation differed by sex, warranting further study.
Subject(s)
Cell Adhesion Molecules , Colon , Cyclin-Dependent Kinase Inhibitor p16 , DNA Methylation , Estrogen Receptor alpha , Exercise , Cell Adhesion Molecules/genetics , Colon/metabolism , Colorectal Neoplasms/genetics , Cyclin-Dependent Kinase Inhibitor p16/genetics , Estrogen Receptor alpha/genetics , Female , Humans , Male , Tumor Suppressor Protein p14ARF/geneticsABSTRACT
BACKGROUND: Chronological age is a prominent risk factor for many types of cancers including colorectal cancer (CRC). Yet, the risk of CRC varies substantially between individuals, even within the same age group, which may reflect heterogeneity in biological tissue aging between people. Epigenetic clocks based on DNA methylation are a useful measure of the biological aging process with the potential to serve as a biomarker of an individual's susceptibility to age-related diseases such as CRC. METHODS: We conducted a genome-wide DNA methylation study on samples of normal colon mucosa (N = 334). Subjects were assigned to three cancer risk groups (low, medium, and high) based on their personal adenoma or cancer history. Using previously established epigenetic clocks (Hannum, Horvath, PhenoAge, and EpiTOC), we estimated the biological age of each sample and assessed for epigenetic age acceleration in the samples by regressing the estimated biological age on the individual's chronological age. We compared the epigenetic age acceleration between different risk groups using a multivariate linear regression model with the adjustment for gender and cell-type fractions for each epigenetic clock. An epigenome-wide association study (EWAS) was performed to identify differential methylation changes associated with CRC risk. RESULTS: Each epigenetic clock was significantly correlated with the chronological age of the subjects, and the Horvath clock exhibited the strongest correlation in all risk groups (r > 0.8, p < 1 × 10-30). The PhenoAge clock (p = 0.0012) revealed epigenetic age deceleration in the high-risk group compared to the low-risk group. CONCLUSIONS: Among the four DNA methylation-based measures of biological age, the Horvath clock is the most accurate for estimating the chronological age of individuals. Individuals with a high risk for CRC have epigenetic age deceleration in their normal colons measured by the PhenoAge clock, which may reflect a dysfunctional epigenetic aging process.