Gambogic Acid Inhibits Wnt/β-catenin Signaling and Induces ER Stress-Mediated Apoptosis in Human Cholangiocarcinoma

Objective: Gambogic acid (GA) has been reported to induce apoptosis in cholangiocarcinoma (CCA) cell lines. However, the molecular mechanisms underlying its anti-cancer activity remain poorly understood. This study was aimed to investigate GA's effect on human CCA cell lines, KKU-M213 and HuCCA-1, and its associated mechanisms on Wnt/p-catenin signaling pathway. Methods: Cell viability, apoptosis, and cell cycle analysis were conducted by MTT and flow cytometry. The effect of GA mediated Wnt/p-catenin and ER stress were determined by luciferase-reporter assay, qRT-PCR, and western blot analysis. Results: GA exhibited potent cytotoxicity in CCA cells which was associated with significantly inhibited cell proliferation, promoted G1 arrest, and activated caspase 3 mediated-apoptosis. GA attenuated p-catenin transcriptional levels, decreased p-catenin protein, and suppressed the expression of c-Myc, a downstream target gene of Wnt/p-catenin signaling. GA activated genes involved in ER stress mechanism in KKU-M213 and enhanced CCA's sensitivity to gemcitabine. Conclusion: Our findings reveal that the molecular mechanism underpinning anti-cancer effect of GA is partially mediated through the inhibition of Wnt/p-catenin signaling pathway and induction of ER stress induced-apoptosis. GA may serve as a promising therapeutic modality for amelioration of gemcitabine-induced toxicity in CCA.