Global DNA Methylation Profile of Head and Neck Squamous Carcinoma Patients at the University College Hospital, Ibadan, Nigeria

Background: Head and neck squamous cell carcinoma (HNSCC) is commonly associated with tobacco and alcohol exposures among other risk factors, which are linked with epigenetics. Epigenetic alterations such as DNA methylation are increasingly implicated in the initiation and progression of cancer. This study quantitated global DNA methylation in peripheral blood of HNSCC patients and controls. The influence of environmental risk factors, age and gender on DNA methylation were also evaluated.

Methods: Venous blood samples were obtained from participants. DNA extraction was carried out using Qiagen kit according to the manufacturer’s instructions. Level of global DNA methylation was obtained with an enzyme-linked immune sorbent assay (ELISA)-based technique (Cell Biolab, CA). Methylated DNA concentrations were obtained by interpolation of the standard curve. Select samples done in duplicates served as intra-assay controls. Data was analysed using IBM SPSS 20. Quantitative variables were summarised as means or medians as appropriate. An independent t-test was used to compare methylation values across cases and control groups and for various independent variable response categories. A multiple linear regression was fitted to explore the influence of study assignment, gender and age on DNA methylation values. All significance testing was conducted at α - 0.05.

Results: Global DNA methylation was higher in cases (10.24 ± 3.85) relative to controls (9.35 ± 3.34). This was however not statistically significant. Females (11.12 ± 4.49) were significantly hypermethylated relative to the males (9.03 ± 2.74). A linear regression analysis showed female gender as the only significant predictor of methylation. Females had values on average 0.28 units higher than males after correcting for age and study assignment. Tobacco and alcohol users among cases did not have significantly higher methylation values than non-users.

Conclusion: Relative hyper methylation was recorded among cases. However, only gender had a significant relationship with DNA methylation in HNSCC in this study.