Molecular correlates of social adversity in breast cancer.

48 Background: Neighborhood disadvantage (ND) is associated with shorter breast cancer (BCa) survival independent of individual, tumor, and treatment factors, suggesting more aggressive tumor biology in women from disadvantaged neighborhoods. This study evaluates how differential DNA methylation (DNAm), gene expression, and biologic pathways are wired with each other to delineate the regulatory landscape of ND on BCa. Methods: We leveraged 55 geocoded ER+/HER2- BCa samples from Hispanic White women enrolled in a prospective genomic-epidemiologic cohort study. Objective ND was evaluated using the Area Deprivation Index (ADI) and subjective ND was evaluated using the patient-reported Neighborhood Social Environment Adversity Survey and the Everyday Expanded Discrimination Survey. We analyzed the association between ND and (1) DNAm, (2) RNA transcription and miRNAs, and (3) blood concentration levels of DNAm co-factors (B12 and folate) from the same patient. To evaluate how the DNAm/expressed pathways are wired with each other to delineate the regulatory landscape of ND in these tumors, we performed correlation analyses among CpGs, genes, and miRNAs in the same topologically associated domain (TAD). We used Spearman correlation as our metric and adjusted the resulting p-values to FDR values. Results: The cohort was divided into low ND (ADI=5; 69%). There were no significant differences between groups by age, race/ethnicity, genetic ancestry, BMI, smoking/alcohol, subtype, stage, or OncotypeDX scores. We discovered that high ND exhibits epigenetic deregulation of immune pathways, consistent with our findings of lower circulating B12 in high ND, suggesting activation of immune pathways through reduced systemic availability of methyl donors. RNA-seq identified higher tumor infiltration of immune cells in patients from high ND (e.g., Interferon alpha and gamma responses and inflammatory responses) consistent with aggressive biology. Estrogen response genes were downregulated suggesting that patients from high ND may develop estrogen-resistant tumors. Higher subjective ND scores discovered epigenetic changes on cell adhesion and calcium signaling genes, along with gene expression of E2F targets and cell cycle’s G2M checkpoint, indicative of a more proliferative/stemness signature. TAD analysis discovered significant developmental, immune, and signaling pathways when correlating DNAm with gene expression (e.g., estrogen response and EMT). Conclusions: In this multi-omic matched cohort, we discovered differentially methylated/expressed pathways, consistent with aggressive biology, wired with each other to identify a novel regulatory landscape of ND on BCa. These findings can inform interventions such as improved access to healthy nutrition (B12) in ND/food deserts or targeted stress-reduction interventions based on our survey findings to ultimately reverse aggressive tumor biology and reduce BCa disparities by ND.