Inhibition of mTOR suppresses human gallbladder carcinoma cell proliferation and enhances the cytotoxicity of 5-fluorouracil by downregulating MDR1 expression


Although 5-fluorouracil (5-FU) is widely used in the treatment of various cancers, drug resistance remains a limitation for its anti-cancer activity. Mammalian target of rapamycin (mTOR) is deregulated in diverse human cancers, including gallbladder carcinoma and mTOR inhibitors show promising anti-cancer activities with proliferation inhibitory effects. This study aims to clarify the benefit of the combination of 5-FU and the mTOR inhibitor, OSI-027, on gallbladder carcinoma cell proliferation.


Two gallbladder carcinoma cell lines and two agents (5-FU and OSI-027) were used in the present study. Cell counting kit-8 assays and EdU staining were performed to examine the proliferation of cancer cells. The expression of MDR1 protein was determined by western blot analysis.


The combination of OSI-027 with 5-FU showed a synergistic anti-proliferative effect on the gallbladder cancer cells, RBE and GBC-SD cells. Upon 5-FU treatment, MDR1 expression was upregulated and OSI-027 could reverse 5-FU-induced MDR1 upregulation. Moreover, MDR1 depletion sensitized gallbladder carcinoma cells to 5-FU stimulation and attenuated the synergistic effect of OSI-027 and 5-FU. Finally, we determined that OSI-027 downregulated MDR1 expression by suppressing its synthesis rather than by promoting its degradation.


Dual mTORC1/mTORC2 inhibitors such as OSI-027 are promising therapeutic agents in combination with 5-FU for the treatment of human gallbladder cancer.

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Cat.No. Product Name Information
S2624 OSI-027 OSI-027 (ASP4786, CERC 006, AEVI-006) is a selective and potent dual inhibitor of mTORC1 and mTORC2 with IC50 of 22 nM and 65 nM in cell-free assays, and more than 100-fold selectivity observed for mTOR than PI3Kα, PI3Kβ, PI3Kγ or DNA-PK. OSI-027 induces autophagy in cancer cells. Phase 1.

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