OP53INHIBITION OF LACTATE DEHYDROGENASE A (LDHA) USING SODIUM OXAMATE LEADS TO METABOLIC CHANGES, DECREASED GROWTH AND MIGRATION IN MEDULLOBLASTOMA CELL LINES

Abstract

Integrated genomic data has identified four distinct Medulloblastoma (MB) sub-groups differing in clinical outcomes, of which group 3 is the most frequently metastatic and characteristically over-expresses cMyc. Lactate dehydrogenase A (LDHA), known for its key role in metabolic functions, is a downstream target of cMyc and HIF1α. We hypothesised LDHA inhibition would influence a change from a glycolytic to an oxidative phosphorylation phenotype, thus leading to decreased MB viability and migration. LDHA protein was examined in MB cell lines (Res256 and UW402) using IHC, Flow cytometry and Western blot. Lactate and pyruvate concentrations, viability, and proliferation were evaluated in the presence or absence of sodium oxamate under normoxic and hypoxic conditions. MB migration (gap-closure) and distance travelled (cell-tracking) was measured using live cell imaging. LDHA expression was elevated under hypoxic conditions in MB cells. LDHA activity was inhibited by sodium oxamate causing a concentration and time dependent decrease in lactate concentration. Significance varied depending on normoxic versus hypoxic conditions (p < 0.05-p < 0.001). Under hypoxic conditions, pyruvate levels also decreased with LDHA inhibition (p < 0.05). Sodium oxamate significantly reduced proliferation and increased the percentage of MB cells in G2/M cell cycle phase. Sodium oxamate treatment also caused a significant decrease in MB migration in a concentration/time dependent manner that was not dependent on reduced proliferation. Inhibition of LDHA activity by sodium oxamate significantly decreased lactate concentrations and significantly inhibited MB migration and proliferation. Targeting MB metabolism through LDHA is a promising approach, which could prevent the use of harsh therapy regimens, and warrants further investigation.