Growth inhibitory and cell death actions of PGG in MCF-7 and MDA-MB231 cells. (a) Overall inhibitory effects of PGG on MCF-7 and MDA-MB231 cell growth after 3 days of daily treatment with PGG in fresh medium. Values are mean ± standard error of the mean (n = 3 wells of 12-well plate). Statistical significance: ***P < 0.001; ****,####P < 0.0001 versus untreated control. Results are representative of two independent experiments. (b) Immunoblot detection of apoptotic cPARP (cleaved poly-ADP-ribose polymerase), P53-Ser15 phosphorylation induced by PGG in MCF-7 or MDA-MB231 cells, and autophagy responses (pAMPK and LC3-II) in MDA-MB231 cells. Phase-contrast photomicrograph shows vaculolation typical of autophagy. The medium was not changed for PGG exposure of longer than 24 hours. DMSO, dimethyl sulfoxide; LC3, microtubule-associated protein 1 light chain 3; pAMPK, phospho-AMP kinase; PGG, penta-O-galloyl-β-D-glucose.