LUBAC accelerates B-cell lymphomagenesis through protection of DNA damage-induced apoptosis, thereby promoting AID-mediated mutations.
Inhibition of LUBAC by small molecules is a promising therapeutic strategy for B-cell lymphomas with NF-kB activation.
Linear ubiquitin chain assembly complex (LUBAC) is a key regulator of NF-kB signaling. Activating single-nucleotide polymorphisms of HOIP, the catalytic subunit of LUBAC, are enriched in patients with activated B cell-like diffuse large B-cell lymphoma (ABC-DLBCL), and expression of HOIP which parallels LUBAC activity is elevated in ABC-DLBCL samples. Thus, to clarify the precise roles of LUBAC in lymphomagenesis, we generated a mouse model with augmented expression of HOIP in B cells. Interestingly, augmented HOIP expression facilitated DLBCL-like B-cell lymphomagenesis driven by MYD88-activating mutation. The developed lymphoma cells partly shared somatic gene mutations with human DLBCLs, with increased frequency of a typical AID mutation pattern. In vitro analysis revealed that HOIP overexpression protected B cells from DNA damage-induced cell death through NF-kB activation, and the analysis of human DLBCL database showed that expression of HOIP positively correlated with gene signatures representing regulation of apoptosis signaling, as well as NF-kB signaling. These results indicate that HOIP facilitates lymphomagenesis by preventing cell death and augmenting NF-kB signaling, leading to accumulation of AID-mediated mutations. Furthermore, a natural compound that specifically inhibits LUBAC was shown to suppress the tumor growth in a mouse transplantation model. Collectively, our data indicates that LUBAC is crucially involved in B-cell lymphomagenesis through protection against DNA damage-induced cell death, and is a suitable therapeutic target for B-cell lymphomas.