PGP and cancer: In vitro studies have shown that berberine can up-regulate P-gp expression in gastric (SC-M1 and NUGC-3) and colon (COLO205 and CT26) cancer cell lines after 24 h exposure [32] as well as increase the intracellular accumulation of rhodamine 123, another P-gp substrate, in bovine brain capillary endothelial cells [33].