CNSC-18. HYPOXIA-INDUCED METABOLIC ADAPTATIONS THROUGH ACOX-1 IN GLIOBLASTOMA

Abstract

Abstract BACKGROUND Hypoxia is a major driver of invasiveness and resistance in glioblastoma (GBM). We hypothesize that GBM adapts to chronic hypoxic conditions through utilization of peroxisomal fatty acid oxidation (FAO). We explored the contribution of acyl coenzyme A oxidase 1 (ACOX-1), a rate-limiting enzyme for peroxisomal FAO, in metabolic adaptation to hypoxia and as a potential therapeutic target. METHODS A primary cell line from a bevacizumab-resistant tumor (012015) was cultured under chronic hypoxia (2%O2) or normoxia (21% O2). We used UPLC-MS/MS and GC-MS to determine lipid and polar metabolites. RNA seq was performed on U251 ACOX-1 (KO) cells under normoxic and hypoxic conditions. Differential gene expression was obtained using TopHat2 (genome alignment), HTSeq, and DEseq. Gene set enrichment analysis was used to compare biological pathways between conditions. ACOX-1 was deleted using CRISPR-Cas9 and orthotopically implanted in NCr/SCID nude mice. Animals were treated with 30 mg/kg of pazopanib or vehicle daily through oral gavage. RESULTS In 012015 cells we observed altered carnitine metabolites, increase in specific triglycerides, and S-lactoylglutathione indicating dysfunctional mitochondrial FAO, and increase in oxidative stress between hypoxic and normoxic conditions. Also, decrease in citric acid cycle metabolites, increase in glycolytic metabolites were seen in hypoxia. Further RNA seq on U251 ACOX-1 (KO) cells showed downregulated genes such as PCK1, SCD, SREBF1, PIPOX (p< 1E-8) and significant KEGG pathways such as unsaturated fatty acid (p= 0.009), peroxisome (p= 0.025) and PPAR (p= 0.016) between hypoxia and normoxia suggesting increased dependence of these cells on peroxisomal FAO. ACOX-1 (KO) mice showed increased survival when treated (p= 6.7E-04) with pazopanib. CONCLUSION In ACOX-1 (KO) model, we observed metabolomic reprogramming with downregulated genes, dysregulated metabolites, and pathways in peroxisomal FAO in hypoxia. These identified genes could be potential targets for therapy in combination with anti-angiogenic therapies that increase hypoxia in GBM.