PGP and glioblastoma: For example, GS sensitized hepatocellular carcinoma (HCC) cells to doxorubicin (DOX) by modulation of COX-2/P-gp dependent pathway [137], MCF-7/DOX cells to DOX by reducing the levels of Bcl-2 and P-gp [138], gall bladder cancer cells to gemcitabine through suppression of NF-κB [139], and glioblastoma cells to sonic hedgehog inhibitor SANT-1 via inflection of Ras/NF-κB pathway [140].