title: Inhibition of mTOR suppresses human gallbladder carcinoma cell proliferation and enhances the cytotoxicity of 5-fluorouracil by downregulating MDR1 expression.
abstract: 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.
authors.affiliation: Departmeng of General Surgery, The Afflicted Drum Tower Hospital of Nanjing University Medical School, Nanjing, China. liqnanjing@163.com.
authors.forename: Q
authors.initials: Q
authors.lastname: Li
authors.forename: L-J
authors.initials: LJ
authors.lastname: Mou
authors.forename: L
authors.initials: L
authors.lastname: Tao
authors.forename: W
authors.initials: W
authors.lastname: Chen
authors.forename: X-T
authors.initials: XT
authors.lastname: Sun
authors.forename: X-F
authors.initials: XF
authors.lastname: Xia
authors.forename: X-Y
authors.initials: XY
authors.lastname: Wu
authors.forename: X-L
authors.initials: XL
authors.lastname: Shi
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005472:Fluorouracil / Q000494:pharmacology*; D005706:Gallbladder Neoplasms / Q000188:drug therapy*; D006801:Humans; D058570:TOR Serine-Threonine Kinases
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D005472:Fluorouracil