β-escin reverses multidrug resistance through inhibition of the GSK3β/β-catenin pathway in cholangiocarcinoma

AIM: To develop a safe and effective agent for cholangiocarcinoma(CCA) chemotherapy. METHODS: A drug combination experiment was conducted to determine the effects of β-escin in c o m b i n a t i o n w i t h c h e m o t h e ra p y o n C C A c e l l s. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay was performed to determine the effects of β-escin and common chemotherapeutics on the proliferation of human CCA cells(QBC939, Sk-Ch A-1, and MZ-Ch A-1). Immunocytochemistry was used to detect the expression of P-glycoprotein(P-gp) protein. Luciferase reporter assay was used to detect the activation of the Wnt/β-catenin pathway. The protein levels of P-gp, p S9-GSK3β, p T216-GSK3β, GSK3β, β-catenin, and p-β-catenin were further confirmed by western blotting.RESULTS: The drug sensitivity of QBC939 and QBC939/5-fluorouracil(5-FU) cells to 5-FU, vincristine sulfate(VCR), or mitomycin C was significantly enhanced by β-escin compared with either agent alone(P < 0.05). In addition, the combination of β-escin(20 μmol/L) with 5-FU and VCR was synergic with a combination index < 1. Further investigation found that the m RNA and protein expression of P-gp was downregulated by β-escin. Moreover, β-escin induced GSK3β phosphorylation at Tyr-216 and dephosphorylation at Ser-9, resulting in phosphorylation and degradation of β-catenin. Interestingly, activation of the GSK3β/β-catenin pathway induced by Wnt3 a resulted in upregulation of P-gp, which was effectively abolished by β-escin, indicating that β-escin down-regulated P-gp expression in a GSK3β-dependent manner.CONCLUSION: β-escin was a potent reverser of P-gpdependent multidrug resistance, with said effect likely being achieved via inhibition of the GSK3β/β-catenin pathway and thus suggesting a promising strategy of developing combination drugs for CCA.

Apoptosis of human cholangiocarcinoma cells induced by ESC-3 from Crocodylus siamensis bile

AIM:To investigate the effects of ESC-3 isolated from crocodile bile on the growth and apoptosis induction of human cholangiocarcinoma cells.METHODS:ESC-3 was isolated from crocodile bile by Sephadex LH-20 and RP-18 reversed-phase column.3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay was conducted to determine the effects of ESC-3 on the proliferation of human cholangiocarcinoma cell lines (QBC939,Sk-ChA-1 and MZ-ChA-1).Giemsa staining,Hoechst 33258 and acridine orange/ethidium bromide staining showed the morphological changes of Mz-ChA-1 cells exposed to ESC-3 at different concentrations.Flow cytometry with regular propidium iodide (PI) staining was performed to analyze the cell cycle distribution of Mz-ChA-1 cells and to assess apoptosis by annexin v-fluorescein isothiocyanate (VFITC)/PI staining.Rh123 staining was used to detect the alteration of mitochondrial membrane potential (ΔΨm).The protein levels of Bax,Bcl-2,Cdk2,cytochrome c and caspase-3 were further confirmed by Western blotting.RESULTS:ESC-3 significantly inhibited the growth of three human cholangiocarcinoma cell lines and arrested Mz-ChA-1 cell cycle at G0/G1 phase.Mz-ChA-1 cells showed typical apoptotic morphological changes after treated with ESC-3 (10 μg/mL) for 48 h.Cell death assay indicated that Mz-ChA-1 cells underwent apoptosis in a dose-dependent manner induced by ESC-3.In addition,ESC-3 treatment could downregulate the protein level of Bcl-2 and upregulate the Bax,leading to the increase in the ratio of Bax to Bcl-2 in Mz-ChA-1 cells.Meanwhile,cytochrome c was released from the mitochondria into the cytosol,which subsequently initiated the activation of caspase-3.All these events were associated with the collapse of the mitochondrial membrane potential.CONCLUSION:ESC-3,the active ingredient of crocodile bile,induced apoptosis in Mz-ChA-1 cells through the mitochondria-dependent pathway and may be a potential chemotherapeutic drug for the treatment of cholangiocarcinoma.