1,2,3,4,6-Penta-O-galloylglucose within Galla Chinensis inhibits human LDH-A and attenuates cell proliferation in MDA-MB-231 breast cancer cells

Abstract

A characteristic feature of aggressive malignancy is the overexpression of lactic acid dehydrogenase-(LDH-) A, concomitant to pericellular accumulation of lactate. In a recent high-throughput screening, we identified Rhus chinensis (Mill.) gallnut (RCG) (also known as Galla Chinensis) extract as a potent (IC 50 < 1 μg/mL) inhibitor of human LDH-A (hLDH-A). In this study, through bioactivity guided fractionation of the crude extract, the data demonstrate that penta-1,2,3,4,6-O-galloyl-β-D-glucose (PGG) was a primary constituent responsible for hLDH-A inhibition, present at 9.95 ± 0.34% dry weight. Theoretical molecular docking studies of hLDH-A indicate that PGG acts through competitive binding at the NADH cofactor site, effects confirmed by functional enzyme studies where the IC 50 = 27.32 nM was reversed with increasing concentration of NADH. Moreover, we confirm protein expression of hLDH-A in MDA-231 human breast carcinoma cells and show that PGG was toxic (LC 50 = 94.18 μM), parallel to attenuated lactic acid production (IC 50 = 97.81 μM). In a 72-hour cell proliferation assay, PGG was found to be a potent cytostatic agent with ability to halt cell division (IC 50 = 1.2 μM) relative to paclitaxel (IC 50 < 100 nM). In summary, these findings demonstrate that PGG is a potent hLDH-A inhibitor with significant capacity to halt proliferation of human breast cancer cells.