Despite active research and the development of target-specific therapies, resistance to standard cytotoxic drugs still represents a challenge in cancer treatment. Many conventional anticancer drugs such as alkylating agents, antimetabolites and topoisomerase inhibitors induce DNA lesions as part of their cytotoxic effect. An important factor that affects the cytotoxic effect of these drugs is the ability of tumour cells to sense a variety of DNA lesions and elicit a coordinated response including DNA repair processes. This global DNA damage response may lead to tolerance to the drug-induced DNA lesions or to enhanced repair preventing an ideal outcome for patients after chemotherapy. Because DNA Damage Response (DDR) and DNA repair mechanisms constitute a dynamic network of finely tuned pathways with coordinated back-up and redundancy, comprehensive functional assays that enable DNA repair activities to be measured are promising.

In the present study, we used a specific multiplexed enzymatic DNA repair assay on biochip to simultaneously investigate several repair pathways: Base and Nucleotide Excision Repair, Inter-Strand Link Repair. We assessed the DNA repair signatures of a panel of 7 cancer cell lines, treated by 5 cytotoxic anticancer drugs. A rigorous strategy allowed us to present a new effective way of classifying the model cancer cell responses to the chemotherapeutic drugs: 3 specific classes of responses were identified according to up and down regulation of specific repair sub-pathways. It provided new indications on the mechanism of action of cytotoxic drugs and on the ability of cell lines to respond. A common hypothesis is that a poor DNA repair capacity is associated with higher cytotoxic effect of DNA-damaging drugs and that defective damage-related signalling pathways may lead to cell death. To determine the possible link between chemosensitivity and DNA repair, we investigated the association between the IC20 obtained for each drug and specific repair sub-pathways independently for each cell line. We identified associations between up-regulations of certain repair pathways and high IC20, as well as the inverted feature (low repair/low IC20). This information gives clues on the possible involvement of specific repair activities in chemoresistance. Our original approach is an interesting functional complement to molecular pharmacology strategies to understand the DDR and might prove highly effective as part of choosing the right treatment for optimized care of cancer patients. Finally, our functional and multiplexed approach could be integrated into systems biology approaches for more effective identification of cancer biomarkers.

We thank the CEA's transversal program Technologies for Health for support.

Citation Format: Sylvie Sauvaigo, Anne Forestier, Fanny Sarrazy, Sylvain Caillat, Yves Vandenbrouck. A multiplexed enzymatic repair assay on biochip reveals a functional DNA repair signature in cancer cell lines exposed to cytotoxic anticancer drugs. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3419. doi:10.1158/1538-7445.AM2013-3419

Millau et al, Lab Chip, 2008; Prunier et al, Mutat Res, 2012; Forestier et al, Plos One, accepted