The LUBAC subunit HOIL-1 promotes the progression of HBV-associated hepatocellular carcinoma independently of linear ubiquitination.

The linear ubiquitin chain assembly complex (LUBAC) has been implicated in both cancer progression and viral activity; however, its role in the progression of hepatitis B virus (HBV)-associated hepatocellular carcinoma (HBV-HCC) remains unclear. Here we found that the expression of LUBAC components and Met1-linked ubiquitination was significantly upregulated and associated with poor prognosis in HCC; however, blocking the LUBAC activity with HOIPIN-1 did not affect the malignancy of HCC cells or their sensitivity to sorafenib treatment. Targeting HOIL-1 inhibited the progression of HCC in vitro and in vivo. Interestingly, we found that HOIL-1, but not other LUBAC components, was exclusively upregulated in HBV-HCC. Functionally, HOIL-1 knockdown suppressed tumor growth, metastasis and stemness in HBV-infected HCC cells. Mechanistically, HOIL-1 interacted with HBx, but not other HBV proteins, and facilitated its stabilization by recruiting deubiquitinatinase USP15, thereby reducing HBx K48-linked ubiquitination. Notably, the clinical analysis indicated that the association between high HOIL-1 expression and poor prognosis was evident only in patients with HBV-HCC with high USP15 expression and not in those with low USP15 expression. Collectively, our results demonstrated that HOIL-1 acts as an oncogene to promote HBV-HCC progression independent of LUBAC activity and may serve as a potential therapeutic target for HBV-HCC.