c-Rel-dependent Chk2 signaling regulates the DNA damage response limiting hepatocarcinogenesis

Background and Aims Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death. The NF-kappa B transcription factor family subunit c-Rel is typically protumorigenic; however, it has recently been reported as a tumor suppressor. Here, we investigated the role of c-Rel in HCC. Approach and Results Histological and transcriptional studies confirmed expression of c-Rel in human patients with HCC, but low c-Rel expression correlated with increased tumor cell proliferation and mutational burden and was associated with advanced disease. In vivo, global (Rel(-/-)) and epithelial specific (Rel(Alb)) c-Rel knockout mice develop more tumors, with a higher proliferative rate and increased DNA damage, than wild-type (WT) controls 30 weeks after N-diethylnitrosamine injury. However, tumor burden was comparable when c-Rel was deleted in hepatocytes once tumors were established, suggesting c-Rel signaling is important for preventing HCC initiation after genotoxic injury, rather than for HCC progression. In vitro, Rel(-/-) hepatocytes were more susceptible to genotoxic injury than WT controls. ATM-CHK2 DNA damage response pathway proteins were suppressed in Rel(-/-) hepatocytes following genotoxic injury, suggesting that c-Rel is required for effective DNA repair. To determine if c-Rel inhibition sensitizes cancer cells to chemotherapy, by preventing repair of chemotherapy-induced DNA damage, thus increasing tumor cell death, we administered single or combination doxorubicin and IT-603 (c-Rel inhibitor) therapy in an orthotopic HCC model. Indeed, combination therapy was more efficacious than doxorubicin alone. Conclusion Hepatocyte c-Rel signaling limits genotoxic injury and subsequent HCC burden. Inhibiting c-Rel as an adjuvant therapy increased the effectiveness of DNA damaging agents and reduced HCC growth.

Automated summary

c-Rel plays an important role in hepatocellular carcinoma by limiting genotoxic injury and subsequent tumor burden. Inhibiting c-Rel can enhance the effectiveness of DNA damaging agents and reduce HCC growth.