Abstract 2417: Predictive and therapeutic impact of DNA damage response activation in locally advanced cervical cancer patients (2014)

Abstract Recent advances in improving outcome of locally advanced cervical cancer (LACC) were made by addition of cisplatin to radiotherapy. However, total 5-year survival rates are still ∼66%, underscoring the need for new therapy strategies. Current therapeutic strategies in cervical cancer consist of cisplatin and radiotherapy, which exert their anti-cancer effects by inducing high levels of DNA lesions including DNA double strand breaks (DSBs), with the aim to induce cell death in tumor cells. However, tumor cells can respond to these therapy-induced DNA lesions by activation of the DNA damage response (DDR). The DDR is a complex signalling network, consisting of multiple kinases and transcriptional programs that function in parallel to arrest ongoing cell cycle progression, which allows time for DNA repair. Effective DNA repair may thus counteracts therapy-induced cancer cell death. Cervical cancers already have a partial dysfunction of the DDR due to frequent, human papilloma virus (HPV) infection. As a result, HPV-infected cervical tumors are thought to rely heavily on remaining DDR activity for their survival. We therefore hypothesize that the residual DDR activity may provide an ‘Achilles heel’ which could be exploited therapeutically using specific DDR inhibitors, to increase tumor cell sensitivity to cisplatin and ionizing radiation. Firstly, we examined the expression and activation status of the key DDR components ATM, Chk2, ATR, Chk1, DNA-PK and MK2 in 375 cervical cancer patients using immunohistochemistry. We found that these DDR components were all abundantly expressed in cervical cancer tissues, underscoring the availability of these components for targeting by DDR inhibitors. Subsequently, we tested chemo- or radiosensitization of specific chemical inhibitors against ATM (KU-55933), ATR (NU-6027), DNA-PK (KU-0060648), Chk1/2 (AZD7762) and MK2 (MK2-inhibitor III) using HPV-positive cervical cancer cell lines HeLa and SiHa. MTT-assay analyses showed that ATR, Chk1/2 and DNA-PK inhibition, sensitized cervical cancer cells to cisplatin. In contrast, clonogenic survival assays revealed that inhibition of ATM, DNA-PK and Chk1/2 caused radiosensitization. In order to uncover how DDR inactivation is most effective in a combined chemo-radiotherapy setting, we therefore optimised an in vitro ‘combination therapy survival assay’ reflecting the different DNA lesions given in clinical LACC therapy. We showed that targeting of ATM, ATR and Chk1/2 caused effective chemo-radiosensitization of cervical cancer cells. Our data show that DDR components are abundantly expressed in cervical cancer. Furthermore, we show that targeting of individual DDR kinases has differential effects on chemo- or radiotherapy sensitivity. Finally, we show that ATM, ATR and Chk1/2 inhibition are promising strategies to further improve the efficacy of platinum-based chemoradiation. Citation Format: Hylke W. Wieringa, Marieke Everts, G.Bea A. Wisman, Ate G.J. van der Zee, Elisabeth G.E. de Vries, Marcel A.T.M. van Vugt. Predictive and therapeutic impact of DNA damage response activation in locally advanced cervical cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2417. doi:10.1158/1538-7445.AM2014-2417