An epigenome-wide analysis of socioeconomic position and tumor DNA methylation in breast cancer patients

BackgroundDisadvantaged socioeconomic position (SEP), including lower educational attainment and household income, may influence cancer risk and outcomes. We hypothesized that DNA methylation could function as an intermediary epigenetic mechanism that internalizes and reflects the biological impact of SEP.MethodsBased on tumor DNA methylation data from the Illumina 450 K array from 694 breast cancer patients in the Women's Circle of Health Study, we conducted an epigenome-wide analysis in relation to educational attainment and household income. Functional impact of the identified CpG sites was explored in silico using data from publicly available databases.ResultsWe identified 25 CpG sites associated with household income at an array-wide significance level, but none with educational attainment. Two of the top CpG sites, cg00452016 and cg01667837, were in promoter regions of NNT and GPR37, respectively, with multiple epigenetic regulatory features identified in each region. NNT is involved in beta-adrenergic stress signaling and inflammatory responses, whereas GPR37 is involved in neurological and immune responses. For both loci, gene expression was inversely correlated to the levels of DNA methylation. The associations were consistent between Black and White women and did not differ by tumor estrogen receptor (ER) status.ConclusionsIn a large breast cancer patient population, we discovered evidence of the significant biological impact of household income on the tumor DNA methylome, including genes in the beta-adrenergic stress and immune response pathways. Our findings support biological effects of socioeconomic status on tumor tissues, which might be relevant to cancer development and progression.

Automated summary

In this study, the researchers analyzed the tumor DNA methylation data of 694 breast cancer patients and found that household income was associated with tumor DNA methylation, while educational attainment was not. The methylation levels of NNT and GPR37 genes were negatively correlated with household income, and these genes are involved in stress response and immune response. This correlation was consistent in both black and white patients. These findings suggest that socioeconomic status has a significant biological impact on tumor tissues and may be relevant to cancer development and progression.