The deubiquitinase USP44 enhances cisplatin chemosensitivity through stabilizing STUB1 to promote LRPPRC degradation in neuroblastoma.

Background: Dysregulated deubiquitinating enzymes (DUBs) execute as intrinsic oncogenes or tumor suppressors and are involved in chemoresistance in cancers. However, the functions and exact molecular mechanisms remain largely unclear in neuroblastoma.

Methods: Here, a R2 screening strategy based on the standard deviation values was used to identify the most important DUB, USP44, in neuroblastoma with stage 4. We validated the role of USP44 regulation upon cisplatin treatment in vitro and in vivo experiments, revealing the molecular mechanisms associated with USP44 regulation and cisplatin sensitivity in neuroblastoma.

Results: We found that low USP44 expression was associated with an inferior prognosis in neuroblastoma patients. Overexpression of USP44 enhanced neuroblastoma cell sensitivity to cisplatin in vitro and in vivo. Mechanistically, USP44 recruited and stabilized the E3 ubiquitin ligase STUB1 by removing its K48-linked polyubiquitin chains at Lys30, and STUB1 further reinforced the K48-linked polyubiquitination of LRPPRC at Lys453 and promoted its protein degradation, thus enhancing the accumulation of mitochondrial reactive oxygen species (mROS), in turn facilitating neuroblastoma cell apoptosis and cisplatin sensitivity. Additionally, overexpression of LRPPRC reversed the promoting effect of USP44 on cell apoptosis in cisplatin-treated neuroblastoma cells.

Conclusions: Our findings demonstrate that the USP44-STUB1-LRPPRC axis plays a pivotal role in neuroblastoma chemoresistance and provides potential targets for neuroblastoma therapy and prognostication.