Abstract 4422: Metabolic adaptations of glioblastoma in hypoxia is mediated by acox-1
Authors: Bhattacharya Ayon , Caflisch Laura , Balinda Henriette , Lodi Alessia , Zhou Mei , Li Mengxing , Chiou Jennifer , Pandey Renu , Sareddy Gangadhara R. , Tiziani Stefano , Chen Yidong , Vadlamudi Ratna K. , Brenner Andrew J. 
Published: March 2024

Abstract
Background: Glioblastoma (GBM) is a recurrent, chemoresistant, malignant brain tumor. Hypoxia is a major factor contributing to resistance in GBM which develops due to aggressive tumor growth and chronic anti-angiogenic therapy. Thus, under limited oxygen supply it is unlikely that the high energy consuming pathways are solely able to provide the energy requirement of GBM cells. Thus, based on our metabolomics data stated below we hypothesize that GBM cells adapt to chronic hypoxia utilizing alternate metabolic pathways such as peroxisomal fatty acid oxidation (FAO). Here we have explored the role of Acyl coenzyme A oxidase (ACOX-1), a rate limiting enzyme for peroxisomal FAO in the metabolic adaptations to hypoxia and as a potential drug target.
Methods: U251 CRISPR dox inducible ACOX1 (KO) cells and patient derived primary GBM were grown under normoxic and hypoxic conditions (2%O2, 5%CO2, 70% humidity). Metabolic analysis was done using UHPLC-MS and LCMS analysis. RNAseq was done using TopHat2 (genome alignment), HTSeq, and DEseq to study the differential gene expression at cut-off of 2-fold change, and p&lt;0.05. GSEA was used to interpret biological pathways. NCr/SCID (Severe Combined Immunodeficiency) mice (n=5) inoculated with U251 ACOX1 knockout cells expressing luciferase were used and treated with anti-angiogenic agent pazopanib at 30 mg/kg, 5 days a week. The U251 luciferase-labeled tumors were imaged starting weekly for tumor volumes using the IVIS (In Vivo Imaging System) Lumina.
Results: In patient derived primary GBM cell lines alterations in metabolites in chronic hypoxia compared to normoxia, such as decrease in citric acid cycle metabolites, increase in glycolytic metabolites, and dysfunctional mitochondrial metabolites. In RNA seq downregulation of genes PCK1, SCD, SREBF1, and PIPOX (p&lt;1x108) involved in PPAR and lipid metabolism pathways in hypoxia versus normoxia were noted. Inhibition of ACOX-1 displayed increased survival in mice administered (p=6.7E-04) with pazopanib compared to the U251 parental control group.
Conclusion: There is metabolomic reprogramming in ACOX-1 KO cells channeled predominantly through FAO as seen through the downregulation of genes downstream of the PPAR signaling pathway, mediated through SREBF1 the master regulator of lipid metabolism. Thus, these genes could be future targets for therapy in combination with anti-angiogenic therapies that aggravate hypoxia in GBM.
Citation Format: Ayon Bhattacharya, Laura Caflisch, Henriette Balinda, Alessia Lodi, Mei Zhou, Mengxing Li, Jennifer Chiou, Renu Pandey, Gangadhara R. Sareddy, Stefano Tiziani, Yidong Chen, Ratna K. Vadlamudi, Andrew J. Brenner. Metabolic adaptations of glioblastoma in hypoxia is mediated by acox-1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4422.