Determining the Potential of DNA Damage Response (DDR) Inhibitors in Cervical Cancer Therapy

SIMPLE SUMMARY: Cervical cancer (CC) is the fourth most common cause of cancer deaths in women. For patients where surgery is not an option, they are treated with cisplatin and radiotherapy (RT) that acts by damaging DNA. However, response is poor, and cisplatin causes kidney injury. The DNA damage response (DDR) consists of coordinated action of proteins that signal DNA damage to stop cell proliferation and promote repair. In this study, we show four different DDR inhibitors targeting PARP, ATR, CHK1 and WEE1 that kill CC cells. These inhibitors also increase the ability of RT and cisplatin to kill CC cells to varying degrees. Additionally, we show that cisplatin-induced kidney injury is due to over-activation of PARP and can be reduced by co-administration of a PARP inhibitor. DDR inhibition is therefore a promising strategy to both increase the effectiveness of current treatment and to protect kidneys from cisplatin-induced toxicity. ABSTRACT: Cisplatin-based chemo-radiotherapy (CRT) is the standard treatment for advanced cervical cancer (CC) but the response rate is poor (46–72%) and cisplatin is nephrotoxic. Therefore, better treatment of CC is urgently needed. We have directly compared, for the first time, the cytotoxicity of four DDR inhibitors (rucaparib/PARPi, VE-821/ATRi, PF-477736/CHK1i and MK-1775/WEE1i) as single agents, and in combination with cisplatin and radiotherapy (RT) in a panel of CC cells. All inhibitors alone caused concentration-dependent cytotoxicity. Low ATM and DNA-PKcs levels were associated with greater VE-821 cytotoxicity. Cisplatin induced ATR, CHK1 and WEE1 activity in all of the cell lines. Cisplatin only activated PARP in S-phase cells, but RT activated PARP in the entire population. Rucaparib was the most potent radiosensitiser and VE-821 was the most potent chemosensitiser. VE-821, PF-47736 and MK-1775 attenuated cisplatin-induced S-phase arrest but tended to increase G2 phase accumulation. In mice, cisplatin-induced acute kidney injury was associated with oxidative stress and PARP activation and was prevented by rucaparib. Therefore, while all inhibitors investigated may increase the efficacy of CRT, the greatest clinical potential of rucaparib may be in limiting kidney damage, which is dose-limiting.