OP53: INHIBITION OF LACTATE DEHYDROGENASE A (LDHA) USING SODIUM OXAMATE LEADS TO METABOLIC CHANGES, DECREASED GROWTH AND MIGRATION IN MEDULLOBLASTOMA CELL LINES

INTRODUCTION: Medulloblastomas (MBs) are the most common solid malignant childhood brain tumour. Based on integrated genomic data there are currently four distinct MB sub-groups, representing different clinical outcomes. Lactate dehydrogenase A (LDHA), known for its metabolic functions, is a downstream target of cMyc and HIF1α both implicated in MB. We hypothesised LDHA inhibition would result in a decrease in lactate and a change from glycolysis to oxidative phosphorylation, leading to decreased viability and migration and increased apoptosis. METHOD: LDHA protein was examined in MB cell lines (Res256 and UW402) using Immunocytochemistry and Western blot (WB). Metabolism and viability was evaluated in the presence or absence of sodium oxamate under normoxic and hypoxic conditions. Live cell imaging was used to measure migration (gap-closure) and distance travelled (cell tracking). Apoptosis was examined by cleaved PARP using WB. RESULTS: LDHA expression was elevated under hypoxic conditions in MB cells. Nuclear and cytoplasmic LDHA immunoreactivity was observed. LDHA inhibition by sodium oxamate caused a concentration and time dependent decrease in lactate levels. Significance varied depending on normoxic versus hypoxic conditions (p < 0.05-p < 0.001). Under hypoxic conditions, pyruvate levels decreased with inhibition (p < 0.05). Sodium oxamate treatment also caused a significant decrease in MB migration in a concentration, time dependent manner. Apoptosis was most noted in Res256 following LDHA inhibition as indicated by PARP cleavage. CONCLUSION: Targeting medulloblastoma metabolism is a promising approach that warrants further investigation to determine, if by doing so, lead to less toxic side effects for children.