PIF1 Affects the Proliferation and Apoptosis of Cervical Cancer Cells by Influencing TERT.

Cervical cancer is a common malignancy in female and it is a serious disease threatening women's lives. We aimed to explore whether PIF1 helicase expression could affect cell proliferation and apoptosis, and whether its mechanisms were related to the expression and activity of TERT. Western blot analysis was used to detect the expressions of PIF1 and TERT in End1/E6E7, Hela, SiHa, Ca-Ski and C-33A cells and apoptosis-related proteins (Bax, Bcl-2 and Caspase-3). RT-qPCR and Western blot analysis determined the expressions of PIF1 and TERT after transfection. After transfection or cycloastragenol (CAG) treatment, the proliferation, apoptosis, cell cycle and telomerase TERT activity were analyzed by CCK-8 assay, flow cytometry analysis and ELISA assay. Co-immunoprecipitation assay was used to verify the interactions between PIF1 and TERT. The expressions of PIF1 and TERT in End1/E6E7, Hela, SiHa, Ca-Ski and C-33A cells were increased. As PIF1 and TERT expressions in C-33A cells showed the minimum increase, C-33A cells were chosen for the next study. PIF1 interference inhibited the proliferation, decreased the ratio of G2/M phase and promoted apoptosis of transfected cells, and PIF1 interference promoted the expressions of Bax and Caspase-3 and suppressed the Bcl-2 expression. Furthermore, PIF1 interference down-regulated the telomerase activity. The effect of PIF1 overexpression was opposite to that of PIF1 interference. Co-immunoprecipitation assay demonstrated that PIF1 could combine with TERT. CAG treatment effectively reversed the effect of PIF1 interference on proliferation, cycle and apoptosis of C-33A cells transfected with shRNA-PIF1. Moreover, CAG treatment increased the expressions of PIF1 and TERT. PIF1 helicase could promote the proliferation and suppress the apoptosis of cervical cancer cells by down-regulating the activity of telomerase TERT.