TMET-06. METABOLIC FATE OF OXALOACETATE IN GLIOBLASTOMA

Abstract

Abstract Oxaloacetate (OAA) inhibits the Warburg effect by reducing the glucose-derived lactate levels in human cancer cell lines. In dose ranging IC50 experiments with human hepatocellular carcinoma (HCC) cell lines, OAA inhibited cell growth in the concentration range 1.7 - 2.4 mM. Previously, we showed that in the presence of OAA, [U-13C]glucose derived lactate was reduced by 48.8% in GBM cells. OAA also increased survival in mouse models of GBM. Here, we are showing an evidence for the direct utilization of OAA by Glioblastoma (GBM) cells, using uniformly 13C-labeled oxaloacetate ([U-13C]OAA) as a metabolic tracer. Patient-derived GBM cells were grown in DMEM medium containing 11.0 mM glucose and 2.0 mM glutamine. When cells reached confluency, were treated with 4.0 mM [U-13C]OAA in the above DMEM medium. GC-MS based 13C isotopomer analysis showed that [U-13C]OAA entered the cells and get metabolized to generate distinct 13C-labeled isotopomers of aspartate, citrate, glutamate, malate and fumarate. Upon entering TCA cycle, [U-13C]OAA generated M+4 aspartate (3.0%) and citrate (3.2%), and M+3 glutamate (4.1%). During the first turn of the TCA cycle, it produced M+2 aspartate (13.9%), malate (10.5%), and fumarate (8.8%), and after multiple turns, [U-13C]OAA led to the production of the following 13C-labeled isotopomers: M+2 citrate (21.5%), M+2 glutamate (17.2%), M+1 glutamate (5.6%) and M+4 glutamate (2.2%). In addition, [U-13C]OAA also produced [U-13C]pyruvate (17.0%) through PEPCK/PK/ or malic enzyme which further generated similar amount of [U-13C]lactate (17.0%) and [U-13C]alanine (12%). These data demonstrate that GBM cells utilize [U-13C]OAA to perturb TCA cycle and glycolytic pathways, and support our previous observation that OAA-derived pyruvate lead to an increase in the total pyruvate pool and associated decrease in glycolytic flux including the glucose-derived lactate. OAA may metabolically reduce tumor growth in difficult to treat cancers.