TMET-10. Role of malic enzyme 2(ME2) in high-grade glioma and related metabolic reprogramming

INTRODUCTION Glioblastoma poses a persistent challenge in oncology. IDH mutations were found in 73 % of clinical cases in some series. How IDH status affect the prognosis of the disease remained controversial. Some studies reported IDH interfered with tumor metabolism in which mutated IDH prefers NADPH and α-KG, instead of NADP+ and isocitrate, as its substrates. High affinity of NADPH and α-KG leads to consumption of NADPH, and in turn affects cellular redox homeostasis and reactive oxygen species (ROS) accumulation and oxidative damage. In addition, mutated IDH converted α-KG to the oncometabolite D-2-hydroxyglutarate (2-HG). The accumulation of 2-HG leads to epigenetic dysregulation via inhibition of αKG-dependent histone and DNA demethylases, and a block in cellular differentiation. Malic enzyme (ME) is a key enzyme in maintaining cellular redox homeostasis. This enzyme catalyzes an oxidative decarboxylation of L-malate (MAL) to pyruvate (PYR) concomitant with the reduction of NAD(P)+ to NAD(P)H. ME2 was also found to increase 2-HG production by adjusting glutaminolysis. This study aimed to determine the role of ME2 in Glioblastoma. METHODS We use glioma cell lines (T98G) to perform in vitro tumor metabolic studies. Silencing of ME2 was achieved by transfection with the 4D-Nucleofector (Lonza) using 2 μg of plasmid targeting ME2. The ATP production was measured using a CellTiter-Glo® 2.0 Cell Viability Assay and ROS was determined using a ROS Detection Assay Kit. RESULTS We observed that silencing ME2 in T98G cells resulted in noticeable alterations in cell metabolite patterns including ATP production and ROS level (decreased ATP level and increased ROS level). In addition, knockdown of ME2 in T98 cells increased the NAD/NADH ratio. CONCLUSION These findings suggest a potential role of ME2 in rewiring metabolic pathways in glioblastoma cells under different environmental conditions and also the importance of ME2 in fueling tumorigenesis via energy production and maintaining redox homeostasis.