STUB1 dampens IFNγ response in tumors by destabilizing the IFNγ receptor complex

Despite its success, immune checkpoint blockade (ICB) cannot induce durable responses in most patients. This is partially attributed to reduced sensitivity to interferon gamma (IFNγ). Thus, elevating tumor IFNγ-receptor 1 (IFNγ-R1) expression to enhance IFNγ-mediated cytotoxicity is of clinical interest. Here, we demonstrate higher IFNγ-R1 expression to sensitize tumors to IFNγ-mediated killing. To unveil the largely undefined mechanisms of IFNγ-R1 expression, we performed a genome-wide CRISPR/Cas9 knockout screen for suppressors of IFNγ-R1 tumor cell surface abundance. We uncovered STUB1 as key mediator for proteasomally degrading IFNγ-R1/JAK1 complex. Conversely, STUB1 inactivation in tumor cells amplified IFNγ signaling and sensitized to cytotoxic T cells, but permitted IFNγ-induced PD-L1 expression. Rationally combining STUB1 inactivation with anti-PD-1 treatment effectively eliminated tumors in vivo. Clinically corroborating this is a STUB1 transcriptomic signature that associates with response to anti-PD-1 treatment in two patient cohorts. Thus, uncovering STUB1 as a pivotal regulator of IFNγ signaling and a synergistic target for anti-PD-1 treatment. Human melanoma cell lines (Control or with STUB1 knock-out) were grown in the presence of Tcell, IFNgamma or control. Three timepoints were taken, 0 hours, 4 hours and 8 hours.