Abstract
OBJECTIVE: To investigate the mechanism by which SIRT1 silencing reduces 5-fluorouracil (5-FU) resistance of cholangiocarcinoma cells and the role of FOXO1/Rab7 autophagy pathway in mediating this effect. METHODS: Human cholangiocarcinoma HCCC-9810 cells were treated with 50, 100, 150, and 200 μg/mL 5-FU to construct a 5-FU-resistant cell model, whose expressions of SIRT1, FOXO1 and Rab7 were detected with immunofluorescence assay, Western blotting and RTqPCR, and the expression levels of autophagy related proteins (Beclin1, LC3, and p62) were detected with Western blotting. The 5-FU resistant cells were transfected with a SIRT1 siRNA, and the changes in 5-Fu resistance and migration ability of the cells were evaluated using CCK-8 assay and wound healing assay; The changes in FOXO1 and Rab7 mRNA levels and protein expressions of SIRT1, FOXO1, Rab7, Beclin1, LC3 and P62 were detected with RT-qPCR and Western blotting. RESULTS: Treatments with 5-FU at 50, 100, 150, and 200 μg/mL all inhibited the proliferation of HCCC-9810 cells. Immunofluorescence assay revealed significantly enhanced SIRT1 expression in 5-FU-resistant HCC-9810 cells, and Western blotting also showed significantly up-regulated protein expressions of SIRT1, Rab7, P62, FOXO1 and Beclin 1 (P < 0.001) and an increased LC3II/LC3I ratio in the cells (P < 0.001). The mRNA levels of SIRT1, Rab7 and FOXO1 were also up-regulated in 5-Fu-resistant cells (P < 0.05). SIRT1 silencing significantly attenuated 5-FU resistance and migration ability of HCCC-9810 cells, and obviously decreased the protein expressions of SIRT1, Rab7, P62, FOXO1 and Beclin1 and the LC3II/LC3I ratio as well (P < 0.001). FOXO1 and Rab7 mRNA levels were significantly decreased in 5-FU-resistant HCC-9810 cells after SIRT1 silencing (P < 0.05). CONCLUSION: Silencing SIRT1 attenuates 5-FU resistance in HCC-9810 cells by inhibiting the activation of the FOXO1/Rab7 autophagy pathway.