Abstract 5352: Targeting DNA methylation in T cells to improve the efficacy of immunotherapy

Abstract

Abstract T-cells are critical mediators of immunity and immunologic memory. Their cell fates are regulated in part through epigenetic mechanisms, including DNA methylation. Recent genome-wide methylation analyses have revealed dynamic alterations in the methylome at various stages of development and differentiation of T cells. At single cell level, it is not easy to simultaneously collect RNA-seq and RBBS methylation profiling. An important task is to understand the expression change of which genes and pathways are regulated by DNA methylations, especially for the ones that are associated with functional variations in the T cells from tumor microenvironment.In this study, we developed a computational approach based on our recently developed metabolic flux estimation to estimate cell-wise global DNA methylation activity level by using scRNA-seq data. We also hypothesize that the global DNA methylation activity level in one cell determines most of the DNA methylation level in gene-specific DNA methylations. Hence, the dependency between gene-specific DNA methylation and expression could be imputed by the dependency between predicted global DNA methylation input level and the gene expression. We validated our method to impute cell-wise global DNA methylation level by using four independent sets of paired gene expression and DNA methylation data. Noted, our prediction of global DNA methylation activity is from a pure metabolic perspective. We found that two metabolic reaction rates, named metabolic flux from methionine to SAM and SAM to SAH, purely predicted by using gene expression data can accurately impute DNA methylation activity in all validating data sets. Our method enables further identification of the disease/cell context specific contributor of DNA methylation, i.e., the genes high contribution to DNA methylations in each individual cell or cell groups. We applied our method on scRNA-seq data of different T cell types extracted from TME of lung, liver, and colon cancer. We have seen that exhausted T cells, especially the ones with decreased Granzymes and PRF1 are associated with increased global DNA methylation level and related genes, suggesting the potential clinical implications in targeting DNA methylation to improve the efficacy of immunotherapies. Citation Format: Pengtao Dang, Xiao Wang, Haiqi Zhu, Jia Wang, Tingbo Guo, Xinyu Zhou, Paveethran Swaminathan, Chi Zhang, Sha Cao. Targeting DNA methylation in T cells to improve the efficacy of immunotherapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5352.