Curcumin synergistically enhances the efficacy of gemcitabine against gemcitabine-resistant cholangiocarcinoma via the targeting LAT2/glutamine pathway.

Cholangiocarcinoma (CCA) is often diagnosed late, leading to incomplete tumor removal, drug resistance and reduced chemotherapy efficacy. Curcumin has the potential for anti-cancer activity through various therapeutic properties and can improve the efficacy of chemotherapy. We aimed to investigate the synergistic effect of a combination of curcumin and gemcitabine against CCA, targeting the LAT2/glutamine pathway. This combination synergistically suppressed proliferation in gemcitabine-resistant CCA cells (KKU-213BGemR). It also resulted in a remarkable degree of CCA cell apoptosis and cell cycle arrest, characterized by a high proportion of cells in the S and G2/M phases. Knockdown of SLC7A8 decreased the expressions of glutaminase and glutamine synthetase, resulting in inhibited cell proliferation and sensitized CCA cells to gemcitabine treatment. Moreover, in vivo experiments showed that a combination curcumin and gemcitabine significantly reduced tumor size, tumor growth rate and LAT2 expression in a gemcitabine-resistant CCA xenograft mouse model. Suppression of tumor progression in an orthotopic CCA hamster model provided strong support for clinical application. In conclusion, curcumin synergistically enhances gemcitabine efficacy against gemcitabine-resistant CCA by induction of apoptosis, partly via inhibiting LAT2/glutamine pathway. This approach may be an alternative strategy for the treatment of gemcitabine-resistant in CCA patients.

Expression of FOXO4 Inhibits Cholangiocarcinoma Cell Proliferation In Vitro via Induction of G0/G1 Arrest.

BACKGROUND/AIM: Forkhead box O4 (FOXO4) has been demonstrated to be a tumor suppressor and proposed as target for treatment of a variety of cancer types. However, the role of FOXO4 in cholangiocarcinoma (CCA), a dangerous cancer of bile-duct epithelium, has rarely been explored. MATERIALS AND METHODS: The proliferative rate of CCA cell lines KKU-213B, KKU-055 and KKK-D068 was investigated using the sulforhodamine B (SRB) assay. Levels of FOXO4, cyclin E1 (CCNE1), CCNE2, cyclin-dependent kinase 2 (CDK2) and cell division cycle 25A (CDC25A) expression were measured using reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR). The cell-cycle profile was explored using flow cytometry. RESULTS: The SRB assay demonstrated that KKU-213B expressed low levels of FOXO4 but its proliferative rate was highest of all cell lines tested. Interestingly, ectopic expression of FOXO4 significantly suppressed proliferation of KKU-213B cells. Cell-cycle analysis revealed that the cell population in the G0/G1 phase was significantly higher in FOXO4-transfected KKU-213B cells than in controls. RT-qPCR analysis demonstrated that the levels of expression of genes that play a role in the G1/S transition, namely CCNE1, CCNE2, CDK2 and CDC25A, were significantly lower in FOXO4-transfected KKU-213B cells compared to controls. CONCLUSION: FOXO4 suppressed CCA cell proliferation partly via down-regulating the expression of genes involved in the G1/S transition, leading to G0/G1 arrest. Our findings suggest that induction of FOXO4 expression might be an alternative approach for the treatment of CCA.