VCP Promotes Cholangiocarcinoma Development by Mediating BAP1 Ubiquitination-Dependent Degradation.

Cholangiocarcinoma (CCA), recognized for its high malignancy, has been an enormous challenge due to lacking effective treatment therapy over the past decades. Recently, the targeted therapies, such as Pemigatinib and Ivosidenib, have provided new treatment options for patients carrying fibroblast growth factor receptor (FGFR) and isocitrate dehydrogenase 1/2 (IDH1/2) mutations, but only ~30% of patients harbor these mutants; it is urgent to explore novel targets and therapeutic therapies. The frequent downregulation of BAP1 has been observed in CCA, and the low expression of BAP1 is closely related to the poor prognosis of CCA. However, there are no effective interventions to re-activate BAP1 protein; blocking its degradation may provide a feasible strategy for BAP1-downregulation CCA treatment. In this study, we demonstrated the tumor-suppressive roles of BAP1 in CCA and identified VCP functions as the key upstream regulator mediated by BAP1 protein homeostasis. Mechanistically, VCP binds to BAP1 and promotes the latter's ubiquitination degradation via the ubiquitin-proteasome pathway, thus promoting cell proliferation and inhibiting cell apoptosis. Moreover, we found that VCP inhibitors inhibited CCA cell growth and promoted cell apoptosis by blocking BAP1 ubiquitination degradation. Collectively, our findings not only provided a novel mechanism underlying the aberrant low expression of BAP1 in CCA but also verified the anti-tumor effect of VCP inhibitors in CCA, offering a novel therapeutic target for CCA treatment.