Effect of PGG on cyclin D1, P21Cip1, and P27Kip1 and other select cell cycle proteins in MCF-7 and MDA-MB231 cells detected by Western blot analyses. (a) Cyclin D1, CDK4, P21Cip1, and P27Kip1 expression and P53-Ser15P in MCF-7 cells. β-Actin was re-probed as loading control. (b) P21Cip1 and P27Kip1 expression in MDA-MB231 cells. (c) Time course of cyclin D1 expression in MCF-7 and MDA-MB231 cells treated with PGG from 12 to 48 hours. Patterns are representative of two experiments. The medium was not changed for PGG exposure of longer than 24 hours. P21Cip1, cyclin-dependent kinase inhibitor 1A; P27Kip1, cyclin-dependent kinase inhibitor 1B; PGG, penta-O-galloyl-β-D-glucose.