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Abstract 1182: The NEDD8 inhibitor pevonedistat blocks the repair of topoisomerase I (TOP1)-induced replication damage and synergizes with TOP1 inhibitors

Genomic DNA is constantly challenged by various genotoxic substances, resulting in an array of DNA lesions including DNA-protein crosslinks (DPCs), one of the most detrimental forms of DNA damage. Topoisomerase I (TOP1) is the molecular target of anti-cancer agents camptothecin derivatives and indenoisoquinolines, which act by trapping TOP1 on genomic DNA. The resulting TOP1-DPCs interfere with DNA replication and transcription and trigger cell death if left unrepaired. In this work, we found that the ubiquitin-like protein NEDD8 plays a pivotal role in the repair of TOP1-DPCs by activating the cullin 4 (CUL4)-RING ubiquitin ligases (CRL4) for K48-linked polyubiquitylation of TOP1-DPCs and their subsequent proteasomal degradation. We identified DCAF13, an understudied family member of DDB1- and CUL4-asscoiated factors, as the receptor of TOP1-DPCs for CRL4. DCAF13 colocalizes with TOP1-DPCs at nascent replication forks and binds the TOP1 core domain with its WD40 domains, linking TOP1 to DDB1-CRL4 for ubiquitylation upon TOP1-induced replication damage. Prompted by these findings, we hypothesized that targeting this NEDD8-activated repair pathway can be developed as a strategy to overcome resistance to TOP1 inhibitors. To test this hypothesis, we performed pharmacological analyses using CellMiner (http://discover.nci.nih.gov/cellminercdb) and found that the activities of TOP1 inhibitors and pevonedistat, a first-in-class NEDD8-activating enzyme inhibitor in clinical trial, are highly correlated across cancer cell lines and with the expression of SLFN11. We also assessed the sensitivity of cultured cancer cells to combination of clinical TOP1 inhibitors and pevonedistat. The combination exhibited synergy in multiple cell lines particularly in human colon cancer cells HCT116 independently of SLFN11. We next investigated the efficacy of combination with TOP1 inhibitor topotecan and pevonedistat in HCT116 xenografts and observed supra-additive effect on tumor growth inhibition. Taken together, our work not only identifies a novel pathway for the repair of TOP1-DPCs but also provides translational evidence to support pevonedistat in combination with TOP1 inhibitors as a rationale therapeutic combination for cancer treatments. Citation Format: Yilun Sun, Andrea Baechler, Valentina Factor, Kanako Okamoto, Yves Pommier. The NEDD8 inhibitor pevonedistat blocks the repair of topoisomerase I (TOP1)-induced replication damage and synergizes with TOP1 inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1182.