USP28 promotes multiple myeloma progression by regulating NF-κB signaling through KIF20B

Abstract Myeloma, as the second most common hematologic malignancy in the world, has seen significant improvements in prognosis due to the emergence of many novel therapeutic approaches, such as proteasome inhibitors (PIs), immunomodulators, and CD38-targeted therapies. The success of the PIs in MM treatment strikingly implies the crucial role of the ubiquitin-proteasome system (UPS) in the disease. Many deubiquitinases (DUBs), a part of UPS, had been found to regulate typical oncogene protein stability in various cancers, including MM. Here, we identified USP28 as a critical factor in promoting MM proliferation by DUBs screening libraries. USP28 is highly expressed in MM patients, and its high expression correlates negatively with patient prognosis. Targeting USP28 by shRNA or an unique inhibitor of USP28, Otilonium bromide, induced cell cycle arrest at G0/G1 and apoptosis in vitro. Additionally, knocking down or inhibition of USP28 significantly reduced tumor burden in a xenograft mouse model with subcutaneous H929 MM cell. Mechanistic studies revealed that USP28 directly deubiquitylates KIF20B (a kinesin member), thereby stabilizing its protein levels. Further studies revealed that stabilized KIF20B interacts with IKKβ, leading to activation of the NF-κB signaling pathway—a known regulator of MM progression and bortezomib (BTZ, a first-line PI) resistance. our findings confirm that USP28 modulates the NF-κB pathway. Consistent with this, USP28 knockdown or inhibition can effectively enhance the sensitivity of MM cells to BTZ. Moreover, Otilonium bromide exhibited a synergetic effect with BTZ both in cell and xenograft model of H929 MM cell. Collectively, our study has identified a critical role of the USP28 in promoting MM progression by deubiquitylating KIF20B to activate NF-κB pathway suggesting that the USP28/KIF20B/ NF-κB axis could serve as a potential diagnostic and therapeutic target in MM.