Abstract 3632: Differential DNA methylation in the benign and cancerous prostate tissue of African American and European American men
Authors: Chernoff Meytal B. , Gillard Marc , Demanelis Kathryn , Delgado Dayana , Williams Anthony , Griend Donald Vander , Pierce Brandon L. 
Published: June 2022

Abstract
In this study, we compare patterns of differential DNA methylation (DNAm) distinguishing tumor and benign prostate tissue in European American (EA) and African American (AA) men to improve our understanding of biological mechanisms that may underlie prostate cancer (PCa) disparities. In the United States, AA men are more likely to be diagnosed with and to die of PCa compared with EA men. Changes in DNAm accompany tumor development and progression, and differences in DNAm across ancestry groups may be an important lens through which to study PCa disparities. We collected paired tumor and histologically benign formalin-fixed paraffin-embedded tissue blocks from 151 (76 AA, 75 EA) PCa patients undergoing prostatectomy at the University of Chicago. DNA was extracted and genome-wide DNAm was measured at ~850,000 CpG sites using the Illumina MethylationEpic Array. After quality control, 682,694 CpGs remained for analysis. We conducted differential methylation analyses, adjusting for batch, age, and individual and identified 29,236 and 38,035 tumor-associated CpGs in AA and EA respectively (p&lt;5x10-8 and Δβ&gt;0.3) with 25,263 CpGs common to both sets. There was a depletion of differentially methylated CpGs in CpG islands and promoters in both groups, but depletion was stronger in AA. Tumor-associated CpGs within islands and in promoters were more likely to be hypermethylated for both groups, though this was stronger in EA. We identified 2,392 genes with differentially methylated promoters common to both ancestry groups; 223 and 1,045 were unique to AA and EA respectively. Shared gene regions included GSTP1, APC, RARB, and GRASP, which have been previously reported. We assigned CpG sites to genes and used Gene Set Enrichment Analysis to identify differentially methylated pathways. The identified pathways include several previously associated with cancer development including the epithelial mesenchymal transition. We also identified ancestry-specific pathways including the early and late estrogen response pathways in AA. Examining the predictive ability of our differentially methylated CpGs, we found that relatively few CpGs (~10) were sufficient to distinguish tumor and benign tissue in AA and EA men (AUC&gt;0.9). Scores constructed from differentially methylated CpGs in EA were able to predict tumor vs benign in AA (and vice versa) with high accuracy. Finally, we examined the association between ancestry and DNAm in both tumor and benign tissue. Here, 89 and 423 ancestry-associated CpGs were identified in tumor and benign respectively. Overall, we find that differential methylation patterns distinguishing tumor and benign tissue are generally similar for EA and AA men. However, differenced in tumor-associated DNAm as well as the presence of ancestry-associated CpGs provide a rich area for future studies exploring the impact of these differences on cancer development in AA and EA men.
Citation Format: Meytal B. Chernoff, Marc Gillard, Kathryn Demanelis, Dayana Delgado, Anthony Williams, Donald Vander Griend, Brandon L. Pierce. Differential DNA methylation in the benign and cancerous prostate tissue of African American and European American men [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3632.