Noncanonical regulation of HOIL-1 on cancer stemness and sorafenib resistance identifies pixantrone as a novel therapeutic agent for hepatocellular carcinoma.

BACKGROUND AIMS: Cancer stem cells (CSCs) contribute to therapy resistance in hepatocellular carcinoma (HCC). Linear ubiquitin chain assembly complex (LUBAC) has been reported to accelerate the progression of cancers, yet its role in the sorafenib response of HCC is poorly defined. Herein, we investigated the impact of LUBAC on sorafenib resistance and the CSC properties of HCC, and explored the potential targeted drugs.

METHODS: The effect of LUBAC on sorafenib response was evaluated. The role of HOIL-1 in promoting sorafenib resistance and the CSCs properties of HCC were investigated in vitro and in vivo. The mechanism of HOIL-1 in regulating Numb/Notch1 axis was explored using mass spectrometry, co-immunoprecipitation, and western blot. HOIL-1 inhibitors were screened using Autodock Vina, and the anti-tumor effects of pixantrone were evaluated.

RESULTS: HOIL-1 contributed to LUBAC-mediated HCC sorafenib resistance independent of its ubiquitin ligase activity. Upregulated HOIL-1 expression enhanced the CSC properties of HCC. Mechanistically, HOIL-1 promoted sorafenib resistance and the CSC properties of HCC via Notch1 signaling. The A64/Q65 residues of HOIL-1 bound with the K78 residue of Numb to impair Numb-mediated Notch1 lysosomal degradation. Notably, pixantrone interrupted HOIL-1/Numb interaction to inhibit Notch1 signaling and CSC properties by targeting the Q65 residue of HOIL-1. Moreover, pixantrone exerted synergistic effects with sorafenib for HCC therapeutic.

CONCLUSION: HOIL-1 is critical in promoting sorafenib resistance and CSC properties of HCC through Notch1 signaling. Pixantrone targeting HOIL-1 restrains the sorafenib resistance and provides a potential therapeutic intervention for HCC.