Aim: We examined methylation patterns with aggressive tumor phenotypes and investigated demographic, socioeconomic and reproductive predictors of gene methylation.
Materials & methods: Pyrosequencing quantified methylation of BRCA1, EGFR, GSTM2, RASSF1, TFF1 and Sat 2. We used quantile regression models to calculate adjusted median methylation values by estrogen and progesterone receptor (ER/PR) status. Bivariate associations between participant characteristics and methylation were examined.
Results: Higher percent methylation of GSTM2 was observed in ER/PR-negative compared with ER/PR-positive tumors in ductal carcinoma in situ (14 vs 2%) and invasive (35 vs 3%) tissue components. Trends in aberrant GSTM2 methylation across tissue components were stronger among ER/PR-negative tumors (p-interaction <0.001). Black women were more likely to have ER/PR-negative tumors (p = 0.01) and show hypermethylation of GSTM2 compared with other women (p = 0.05).
Conclusion: GSTM2 promoter hypermethylation may serve as a potential biomarker of aggressive tumor development and a mechanism for ER/PR-negative tumor progression.
Keywords: DNA methylation; GSTM2; breast cancer; breast cancer disparities; estrogen/progesterone receptor; tumor progression.