Genome Wide Remodeling Of Dna Methylation And Cpg Hypermethylation Is Tightly Linked To Acquired Resistance In Testicular Cancer.

Abstract Acquired resistance to chemotherapy is perhaps the major barrier to cure of advanced cancers. Testicular germ cell tumors (TGCTs) are the most common cancers of young males. TGCTs are one of the few solid tumors that are cured at a high rate with standard cisplatin-based chemotherapy. However, TGCTs become resistance to cisplatin resulting in poor outcomes. While the mechanisms accounting for cisplatin hypersensitivity in TGCT remain elusive, it has been suggested that DNA hypermethylation may play a role. However, there is little direct experimental evidence to support this claim. In the present study, we have leveraged unique isogenic cell models to provide strong evidence for net DNA hypermethylation as a key mechanism leading to acquired cisplatin resistance in TGCT cells. Genome-wide DNA methylation analysis revealed that hypomethylated CpG loci were enriched for SUZ12 and EZH2 binding and H3K27me3 sites. In contrast hypermethylated CpG loci were significantly enriched for CTCF and RAD21 domains as well as repressive DNA segments indicating the global remodeling of nuclear chromatin structure in resistant cells. Integrative computational analysis of RNA-seq and EPIC DNA methylation array data revealed a strong inverse correlation between gene expression and CpG gene promoter methylation. This analysis also revealed a strong bidirectional shift between gene promoter and gene body DNA methylation that correlated closely with upregulated expression of PRC2 target genes and down regulation of tumor suppression genes in resistant cells. Hence the data further suggests a functional interplay between DNA methylation and the PRC2 pathway that modulates cisplatin sensitivity of TGCTs. Further studies including H3K27me3 ChIP-seq are ongoing to further elucidate this relationship. In conclusion, our finding supports the hypothesis that genome wide remodeling of DNA methylation is associated with cisplatin hypersensitivity and resistance of TGCTs and further supports the use of hypomethylation therapy for relapsed TGCT patients. Citation Format: Zeeshan Fazal, Ratnakar Singh, Megan Tomlin, Doha Shokry, Aleyah Hattab, Sarah Spinella, Michael Spinella. Genome wide remodeling of DNA methylation and CpG hypermethylation is tightly linked to acquired resistance in testicular cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2096.