GSE201460
­The proteasome regulator PSME4 reduces the response to immunotherapy by abrogating tumor immunogenicity in NSCLC
Disruption in proteostasis is a hallmark of cancer, with aberrations in proteasome-mediated degradation highly implicated in this malignancy. Proteasomes further bear critical importance in tumor immunogenicity by regulating inflammatory signaling, promoting immune cell activation and playing a crucial role in antigen processing and presentation. Indeed, response to immunotherapy in melanoma patients has been recently linked to increased expression of immunoproteasomes, a specialized form of proteasomes that are upregulated under inflammatory conditions. Yet, the percentage of patients that respond to therapy remains low, and the underlying mechanisms driving resistance remain poorly understood. Further, comprehensive analysis of the role proteasomes play in the pathophysiology of cancer and as a modulator of anti-tumor immunity is remains lacking. Here, we show that proteasome complex composition varies across cancer types and can be used to stratify patient response to immunotherapy. Specifically, we found that the proteasome regulator PSME4 is upregulated in NSCLC and associated with poor prognosis. We show that PSME4 alters proteasome activity and antigen processing attenuating the antigenic diversity and presentation. Through exacting biochemical assays, proteasome profiling of patient-derived NSCLC samples, combined with scRNA-seq, immunopeptidomics and in vivo analyses we uncovered a novel mechanism of immune evasion mediated by PSME4, which promotes an immunosuppressive tumor microenvironment and abrogates anti-tumor immunity. Collectively, our approach may be adapted to other cancer types and pathological settings and affords a novel paradigm by which proteasome composition heterogeneity should be examined and targeted in the context of precision oncology. Overall design: RNA-seq was performed to measure changes in mRNA expression in PSME4-depleted A549 cells their control