The Synergistic Effect Of PARP Inhibitor And PTEN Inhibitor On Ovarian Cancer

Objective: Ovarian cancer is the deadliest gynecological cancer,with a five-year survival rate of about 30%.Due to the high heterogeneity and the complicated pathological mechanisms of ovarian cancer,conventional chemotherapeutic agents are less then optimal because of their insufficient efficacy,high relapse rate after drug withdrawal,as well as emergence of drug resistance after long-term chemotherapy.Thus,there exists a significant unmet need to develop new therapeutic strategies for ovarian cancer.PARP inhibitors,a novel class of targeted drugs,have been demonstrated to play anti-cancer roles by inhibiting the repair of DNA damage in ovarian cancer cells,and the combination of PARP inhibitors with other chemotherapeutic drugs achieve better therapeutic effects.Previous studies have shown that some tumors lacking PTEN are more sensitive to PARP inhibitors,however,their roles in ovarian cancer are still unclear.This study aimed to investigate whether PTEN inhibitors had cell-killing effects on ovarian cancer,and whether PTEN inhibitors enhanced the tumor cell-killing effects of PARP inhibitors on ovarian cancer.Methods: First,the effects of PTEN inhibitor VO-OHpic and PARP inhibitor Olaparib on the proliferation of several common ovarian cancer cell lines were evaluated by MTT assay and colony formation assay,the effect of VO-OHpic on the apoptosis and cell cycle of ovarian cancer cells were detected using flow cytometry and Western blot,the impact of VO-OHpic on DNA damage in ovarian cancer cells were studied using immunofluorescence,immunohistochemistry and Western blot.Then,the combination effects of different concentrations of VO-OHpic and Olaparib on ovarian cancer cell lines were detected by MTT assay.Finally,the effects of two inhibitors on the growth of subcutaneous xenografts in nude mice,as well as the expression of DNA damage-related proteins ?H2AX and 53BP1 in tumors,were evaluated using a mouse model of ovarian cancer.Results: In vitro experiments showed that VO-OHpic and Olaparib inhibited the proliferation of several common ovarian cancer cell lines A2780,SKOV3,HO8910,OVCAR5,OVCAR8 and ES2 cells to some extent.Among them,SKOV3 and ES2 cell lines were the most sensitive and least sensitive to VO-OHpic,Functional studies showed that VO-OHpic promoted the apoptosis and cell cycle G2/M phase arrest of both cell lines.Mechanism studies revealed that in both cell lines,VO-OHpic induced significant DNA damage,and up-regulated the expressional of several DNA damagerelated proteins,including ?H2AX,53BP1,ATM and ATR,while inhibited the activity of PTEN protein.ES2 cells,which were the least sensitive to the two drugs,were treated with different concentrations of VO-OHpic and Olaparib.Results showed that the combination of VO-OHpic and Olaparib resulted in improved cell-killing effects,and demonstrated synergistic cell-killing effect.In vivo experiments confirmed that the combination of VO-OHpic and Olaparib significantly inhibited the tumor growth,and up-regulated the protein levels of ?H2AX and 53BP1 in tumor tissues.Conclusion: In vitro and in vivo results showed that PTEN inhibitor VO-OHpic exerted cell-killing effect on ovarian cancer cells by promoting the apoptosis and cell cycle arrest via inducing DNA damage in ovarian cancer cells.PARP inhibitor Olaparib also had cell-killing effect on ovarian cancer cells.The combination of the two inhibitors had a synergistic effect on ovarian cancer cells.This study not only induces new ideas for the treatment of ovarian cancer,provides new drug candidates for the clinical use of ovarian cancer treatment,but also provides considerable theoretical and technical supports for the development of combination therapies with small molecule inhibitor drugs.