UBL3 governs VEGFR inhibitor resistance by activating NOTCH signaling in renal cell carcinoma.

BACKGROUND: Targeted therapy is the first-line treatment for patients with metastatic renal cell carcinoma (RCC), with vascular endothelial growth factor receptor inhibitors (VEGFRis) constituting the bulk of regimens used. Although the repertoire of VEGFRis for RCC now spans from sunitinib to cabozantinib, resistance to treatments has emerged as a common and prominent challenge. Thus, identifying novel therapeutic targets has become essential for enhancing the antitumor efficacy of current treatments and inhibiting RCC progression.

METHOD: To investigate the potential mechanisms underlying VEGFRi resistance in RCC, we performed a genome-wide CRISPR/Cas9 library screen under sunitinib and cabozantinib treatment and identified UBL3 as a key driver of VEGFRi resistance in RCC cells. The critical role of UBL3 in promoting VEGFRi resistance was validated using CCK8 assays, flow cytometry, TUNEL assays, and bioinformatics analyses. To elucidate the molecular mechanisms underlying UBL3, we utilized western blotting, RNA sequencing, chromatin immunoprecipitation, small extracellular vesicles (sEVs) isolation, and Astral-DIA proteomics. The contribution of UBL3 to VEGFRi resistance was further confirmed through comprehensive in vitro and in vivo experiments.

RESULTS: UBL3 was confirmed to suppress apoptosis and promote VEGFRi resistance through NOTCH signaling activation. Further investigations highlighted the importance of NOTCH signaling in VEGFRi resistance in RCC via the NOTCH-PTEN-AKT and NOTCH-FOS pathways and revealed the mechanisms by which UBL3 activated NOTCH signaling. On the one hand, UBL3 formed complex with NOTCH2 and ADAM17 simultaneously, accelerating ADAM17-mediated cleavage of NOTCH2. On the other hand, UBL3-modified NOTCH2 was sorted into sEVs, which were taken up by recipient cells, activating NOTCH signaling and thereby transmitting VEGFRi resistance. Finally, lipid nanoparticle-mediated delivery of the CRISPR/Cas9 knockout system targeting UBL3 effectively restored the sensitivity of RCC tumors to VEGFRis.

CONCLUSION: This study emphasized the importance of UBL3 in VEGFRi resistance in RCC and proposed that UBL3 activated NOTCH signaling through two distinct pathways, thereby suppressing cancer apoptosis and promoting resistance to VEGFRis. These findings provided a solid scientific foundation and paved the way for the development of novel therapeutic strategies for patients with advanced RCC.