OTUB1 knockdown promotes apoptosis in melanoma cells by upregulating TRAIL expression

Abstract

Melanoma, the most serious type of skin cancer, exhibits a high risk of metastasis. Although chemotherapeutic treatmentfor metastatic melanoma improves disease outcome and patientsurvival, some patients exhibit resistance or toxicity to the drugtreatment regime. OTUB1 is a deubiquitinating enzyme overexpressedin several cancers. In this study, we investigated theeffects of inhibiting OTUB1 expression on melanoma-cell proliferationand viability and identified the underlying molecularmechanism of action of OTUB1. We did endogenous OTUB1knockdown in melanoma cells using short interfering RNA,and assessed the resulting phenotypes via MTT assays, Westernblotting, and cell-cycle analysis. We identified differentiallyexpressed genes between OTUB1-knockdown cells and controlcells using RNA sequencing and confirmed them via Westernblotting and reverse transcription polymerase chain reaction.Furthermore, we investigated the involvement of apoptotic andcell survival signaling pathways upon OTUB1 depletion. OTUB1depletion in melanoma cells decreased cell viability and causedsimultaneous accumulation of cells in the sub-G1 phase, indicatingan increase in the apoptotic-cell population. RNA sequencingof OTUB1-knockdown cells revealed an increase in thelevels of the apoptosis-inducing protein TRAIL. Additionally,OTUB1-knockdown cells exhibited increased sensitivity toPLX4032, a BRAF inhibitor, implying that OTUB1 and BRAFact collectively in regulating apoptosis. Taken together, ourfindings show that OTUB1 induces apoptosis of melanomacells in vitro, likely by upregulating TRAIL, and suggest thatapproaches targeting OTUB1 can be developed to provide noveltherapeutic strategies for treating melanoma.