DNA methylation patterns of SOCS1 gene in peripheral blood identifies risk loci associated with Bladder cancer based on principal component analysis.

Bladder cancer (BCa) is a common carcinoma of the urinary tract which occurs in the bladder mucosa. In recent years, people have recognized that epigenetic changes such as DNA methylation play important roles in the development of BCa, but the specific mechanism is unclear. In this study we detected the methylation rates in SOCS1 gene of 490 subjects (including 247 patients with BCa, and 243 healthy controls) using the MassARRAY EpiTYPER system. Principal component analysis (PCA) was conducted with the aim of identifying common underlying patterns that could explain the largest part of common variance in methylation across units. Logistic regression model was used to assess the relation of SOCS1 methylation patterns with factors related to BCa risk. The methylation rates varied for different CpG units and were significantly difference in cases compared to controls. Six principal component factors were extracted by combining initial eigenvalue, explanatory power and Scree Plot. After adjusting for age, gender, family history of bladder cancer, smoking, and drinking, we observed that Factor 1 (OR=0.051, 95%CI: 0.015-0.178, p<0.001), Factor 2 (OR=0.146, 95%CI: 0.073-0.295, p<0.001), Factor 3 (OR=0.346, 95%CI: 0.198-0.606, p<0.001), and Factor 4 (OR=0.270, 95%CI: 0.135-0.537, p<0.001) were associated with BCa. Based on follow-up results, we found that the 1-, 3-, 5-year survival rates in hypermethylated group were lower than then in hypomethylated group. We found that several CpG units in methylation patterns were associated with the incidence of BCa, revealed the important DNA methylation patterns for BCa pathogenesis. Our findings provided new insights into understanding this disease and new potential targets for therapeutic intervention for BCa patients in the future.