Abstract 86: O-GlcNAc transferase regulates glioblastoma acetate metabolism via regulation of CDK5-dependent ACSS2 phosphorylation

Cancer cells alter their metabolism to increase cell growth. A subset of the glucose taken up is shunted into the hexosamine biosynthetic pathway where it is used to synthesize UDP-GlcNAc, a substrate of O-GlcNAc transferase (OGT), which modifies cytoplasmic and nuclear proteins with O-linked sugar moieties. Here, we show that OGT and O-GlcNAcylation are elevated in glioblastoma (GBM) cancer cells and in GBM patient samples that correlates with disease progression. Reduction of OGT expression in GBM cells led to significant reduction in anchorage-independent growth, acetyl-CoA levels, and decrease in free fatty acids. Conversely, overexpressing OGT in GBM cells had the opposite effect. Reducing OGT expression in GBMcells transplanted in an orthotopic intracranial mouse model reduced tumor growth and extended survival. Mechanistically, we show that OGT overexpression increases carbon-flux of acetate to acetyl-CoA, a reaction carried by the enzyme acetyl-CoA synthetase 2 (ACSS2). Indeed, OGT regulates ACSS2 protein levels and O-GlcNAcylation increases ACSS2phosphorylation on Ser-267 in a cyclin dependent kinase 5 (CDK5)-dependent manner, which regulates its stability by reducing polyubiquitination and degradation. ACSS2 Ser-267 is critical for OGT-mediated GBM growth as overexpression of ACSS2 Ser-267 phospho-mimetic rescues growth in vitro and in vivo. Using an ex vivo GBM brain slice model we show that treatment of GBM-transplanted slices with OGT inhibitor Ac-GlcNAc-5S or pan-cdk inhibitor dinaciclib reduced growth of pre-formed tumors in cultured brain slices. These results suggest a crucial role for O-GlcNAc signaling in transducing nutritional state to regulate acetate metabolism and identify OGT and CDK5 as novel therapeutic targets for treatment of glioblastoma. Citation Format: Lorela Ciraku, Zachary Bacigalupa, Rebecca Moeller, Jing Ju, Rusia H. Lee, Christina Ferrer, Sophie Trefely, Nathaniel W. Snyder, Luca D'Agostino, Christos D. Katsetos, Wenyin Shi, Mauricio J. Reginato. O-GlcNAc transferase regulates glioblastoma acetate metabolism via regulation of CDK5-dependent ACSS2 phosphorylation [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 86.