ECOA-4. Hypoxia alters the DNA methylation profile of glioblastoma tumor cells

Abstract

Abstract Glioblastoma (GBM) is the deadliest and most vascularized brain tumor in adults; however, blood circulation is highly inefficient in these tumors, contributing to areas of cell death (necrosis) within the tumor, which is likely due to oxygen deprivation (hypoxia). Hypoxia plays a major role in tumor growth, invasion, and resistance to therapy. Hypoxic stress has been linked to several changes that are fundamental to the malignant progression of GBM and other tumor types. Pimonidazole (PIMO) is an exogenous marker of hypoxia that is used to delineate hypoxic regions in several tumor types. To date, a clear hypoxia gene signature has not been specifically described for GBM. We hypothesize that specific cellular pathways are differentially regulated in hypoxic tumor niches and can serve as novel actionable targets for treatment-resistant tumor cells in GBM. Over the past 3 years, we have administered PIMO to 35 patients with primary IDH1/2 wild-type GBM and isolated PIMO-positive and PIMO-negative tumor cells by laser capture microdissection using a PIMO-specific antibody on frozen tumor specimens. Total genomic DNA was isolated and subjected to DNA methylation profiling using the Illumina Infinium Methylation EPIC array. Our preliminary results suggest that PIMO-positive (hypoxic) tumor cells display a distinct DNA methylation profile that corresponds to changes in expression of a set of genes associated with immune regulation, angiogenesis, and proliferation. Furthermore, multiple CpG sites within the promoter of some genes are differentially methylated in hypoxic cells, suggesting these genes may be epigenetically regulated under hypoxia. In conclusion, our results indicate that hypoxia is associated with distinct epigenetic alterations in tumor cells which may alter how these cells respond to low oxygen levels and can further be utilized to uncover the epigenomic vulnerabilities of hypoxic tumor cells in GBM.