High neighborhood deprivation impacts DNA methylation and gene expression in cancer-related genes (RNA-Seq)
Background: Low socioeconomic status (SES) has been linked to chronic stress and poorer health outcomes for marginalized communities in the U.S. The biological processes mediating the impact of SES on health to promote chronic diseases, such as cancer, remain poorly understood. Here, we aim to determine how changes in DNA methylation are linked to neighborhood-level socioeconomic deprivation, thereby promoting cancer initiation and progression through cancer- and immune-related pathways.     Methods: We extracted DNA from 402 fresh frozen tissues from 289 women in the NCI-Maryland Breast Cancer Cohort, including 185 tumor samples, 113 additional paired adjacent normal samples, and 104  normal tissues from reduction mammoplasty. Census-tract level socioeconomic deprivation was measured via a Neighborhood Deprivation Index (NDI) using the geocoded addresses from our study participants. DNA methylation values were acquired using the Illumina Infinium MethylationEPIC 850K Beadchip. We conducted a differentially methylated probe (DMP) analysis between tumor and adjacent normal tissue to characterize methylation profiles by NDI status. We also used methylCIBERSORT to estimate immune cell subpopulation differences by tissue type and NDI status.     Results: NDI was significantly associated with self-reported race in our cohort in both normal (p<0.0001, 95% CI -4.32, -2.58) and tumor (p<0.0001, 95% CI -4.22, -2.79) tissue. Our DMP analysis showed more significant methylation events (hypo- or hyper- methylation of the tumor tissue compared to adjacent normal tissue) in the NDI high group compared to the NDI low group. We also identified five CpG sites that were significantly hypomethylated in the tumors of the NDI high group, including two tumor suppressor genes, LRIG1 (p=1.99 x10-10) and WWOX (p=6.47 x 10-9). These methylation changes translated to an inverse relationship between gene expression for these tumor suppressor genes and NDI. We also identified significantly lower neutrophils in the NDI high tumors compared to NDI low tumors (p=0.001, 95% CI -0.112, -0.028).     Conclusions: Overall, our analysis provides evidence that high neighborhood deprivation can lead to pro-tumorigenic changes in DNA methylation and gene expression that may impact the immune microenvironment, breast cancer progression, and overall survival. Overall design: RNA was isolated from frozen breast tumors using TRIzol method. The mRNA profiles of the above breast tumors were generated by deep sequencing using Illumina NovaSeq S2.