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 identifiedRhus chinensis(Mill.) gallnut (RCG) (also known as Galla Chinensis) extract as a potent (IC50< 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 forhLDH-A inhibition, present at ~9.95 ± 0.34% dry weight. Theoretical molecular docking studies ofhLDH-A indicate that PGG acts through competitive binding at the NADH cofactor site, effects confirmed by functional enzyme studies where the IC50= 27.32 nM was reversed with increasing concentration of NADH. Moreover, we confirm protein expression ofhLDH-A in MDA-231 human breast carcinoma cells and show that PGG was toxic (LC50= 94.18 µM), parallel to attenuated lactic acid production (IC50= 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 (IC50= 1.2 µM) relative to paclitaxel (IC50< 100 nM). In summary, these findings demonstrate that PGG is a potenthLDH-A inhibitor with significant capacity to halt proliferation of human breast cancer cells.