Targeting neddylation sensitizes colorectal cancer to topoisomerase I inhibitors by inactivating the DCAF13-CRL4 ubiquitin ligase complex

Colorectal cancers (CRCs) are prevalent worldwide, yet current treatments remain inadequate. Using chemical genetic screens, we identify that co-inhibition of topoisomerase I (TOP1) and NEDD8 is synergistically cytotoxic in human CRC cells. Combination of the TOP1 inhibitor irinotecan or its bioactive metabolite SN38 with the NEDD8-activating enzyme inhibitor pevonedistat exhibits synergy in CRC patient-derived organoids and xenografts. Mechanistically, we show that pevonedistat blocks the ubiquitin/proteasome-dependent repair of TOP1 DNA-protein crosslinks (TOP1-DPCs) induced by TOP1 inhibitors and that the CUL4-RBX1 complex (CRL4) is a prominent ubiquitin ligase acting on TOP1-DPCs for proteasomal degradation upon auto-NEDD8 modification during replication. We identify DCAF13, a DDB1 and Cullin Associated Factor, as the receptor of TOP1-DPCs for CRL4. Our study not only uncovers a replication-coupled ubiquitin-proteasome pathway for the repair of TOP1-DPCs but also provides molecular and translational rationale for combining TOP1 inhibitors and pevonedistat for CRC and other types of cancers. Repair of topoisomerase 1 (TOP1) DNA protein crosslinks (DPC) limits the efficacy of the TOP1 inhibitor irinotecan in cancer therapy. Here, the authors identify pevonedistat, NEDD8 inhibitor, as synergistic with irinotecan by blocking neddylation-activated ubiquitin/proteasomal degradation of TOP1-DPC.

Automated summary

Combining TOP1 inhibitors and NEDD8 inhibitors can synergistically kill human CRC cells by blocking the repair of TOP1-DPCs. The study identifies pevonedistat as an effective inhibitor of NEDD8, preventing the proteasomal degradation of TOP1-DPCs. This research provides molecular and translational rationale for the combination therapy of TOP1 inhibitors and pevonedistat in CRC and other types of cancers.