A Small Molecule Inhibitor of Deubiquitinase OTUD3 Promotes DR5-Induced Apoptosis in Lung Cancer Through ER Stress Modulation

Abstract Background: Lung cancer is cancer with the highest morbidity and mortality in the world and poses a serious threat to human health. Therefore, discovering new treatments is urgently needed to improve lung cancer prognosis. The ubiquitin-proteasome system is an important target for the research of antineoplastic drugs, in which deubiquitinase inhibitors have broad clinical applications. In this study, we show that Rolapitant, an inhibitor of deubiquitinase OTUD3, can inhibit the proliferation and induce apoptosis of lung cancer cells through OTUD3. Methods: Cell viability was measured by CCK8 assays. Apoptosis, cell cycle and surface DR5 expression on lung cancer cells were analyzed by flow cytometry. The expression of transcription level was measured by real time RT-PCR methods. Protein expression was examined in Rolapitant-treated lung cancer cells using Western blotting. Proteomics sequencing was used to detect the molecules which Rolapitant regulate. A549 xenograft nude mice were used to assess the efficacy of Rolapitant in vivo.Result: We showed that Rolapitant enhanced the ubiquitination levels of substrate GRP78 and reduced its protein level. Proteomics sequencing indicated that Rolapitant significantly upregulated the expression of death receptor 5 (DR5). Rolapitant also promoted lung cancer cell apoptosis through upregulating cell surface expression of DR5 and enhanced TRAIL-induced apoptosis. Mechanistically, Rolapitant directly targeted the OTUD3-GRP78 axis to trigger endoplasmic reticulum (ER) stress-C/EBP homologous protein (CHOP)-DR5 signaling, sensitizing lung cancer cells to TRAIL-induced apoptosis. In the vivo assays, Rolapitant suppressed the growth of lung cancer xenografts in immunocompromised mice at suitable dosages without apparent toxicity.Conclusions: Therefore, the present study identifies Rolapitant as a novel inhibitor of deubiquitinase OTUD3 and establishes that the OTUD3-GRP78 axis is a potential therapeutic target for lung cancer.