Deubiquitylase OTUD3 regulates integrated stress response to suppress progression and sorafenib resistance of liver cancer.

The integrated stress response (ISR) is activated in response to intrinsic and extrinsic stimuli, playing a role in tumor progression and drug resistance. The regulatory role and mechanism of ISR in liver cancer, however, remain largely unexplored. Here, we demonstrate that OTU domain-containing protein 3 (OTUD3) is a deubiquitylase of eukaryotic initiation factor 2α (eIF2α), antagonizing ISR and suppressing liver cancer. OTUD3 decreases interactions between eIF2α and the kinase EIF2ΑK3 by removing K27-linked polyubiquitylation on eIF2α. OTUD3 deficiency in mice leads to enhanced ISR and accelerated progression of N-nitrosodiethylamine-induced hepatocellular carcinoma. Additionally, decreased OTUD3 expression associated with elevated eIF2α phosphorylation correlates with the progression of human liver cancer. Moreover, ISR activation due to decreased OTUD3 expression renders liver cancer cells resistant to sorafenib, while the combined use of the ISR inhibitor ISRIB significantly improves their sensitivity to sorafenib. Collectively, these findings illuminate the regulatory mechanism of ISR in liver cancer and provide a potential strategy to counteract sorafenib resistance.