Objective To assess the sensitisation effects of DDR inhibitors combined with conventional chemotherapeutics agents (cisplatin et al) in a drug-resistant ovarian cancer cell line(OVCAR-8). Methods Inhibitors of DDR regulators with cisplatin were applied to challenge OVCAR-8, and evaluated the DNA damage response (DDR) and cytotoxic effects of different combination of chemicals. Inhibition of proliferation to OVCAR-8 of different drugs was evaluated by MTT assay. The activation of phosphorylation of histone family 2A variant(γH2AX) and p53 binding protein 1 (53BP1) in OVCAR-8 were evaluated by immunofluorescence to observe their ability of recruitment and forming foci at DNA damage site. Results We observed that combined treatment of ataxia-telangiectasia mutated(ATM)/ATM and Rad 3-related(ATR) inhibitor and cisplatin can suppress the activation of damage repair mechanisms and weakened the proliferative activity of OVCAR-8 cells (P<0.01); ATR pathway was suppressed and the signal of γH2AX weakened and cell survival rate significantly reduced when combination therapy of HU and Wortmannin (P<0.05); poly ADP-ribose polymerase (PARP) inhibitor could not enhance chemosensitivity in OVCAR-8 cells when combined with cisplatin (P>0.05). Conclusion We substantiated that appropriate inhibitors of DNA damage response may have a potential to improve the anti-tumor effect of conventional chemotherapy drugs and prevent drug resistances.
