BAP1-mediated ubiquitination inhibition and CAS6/AXL signaling activation in bladder cancer progression

This study investigates the role of BRCA1-associated protein 1 (BAP1) in regulating the ubiquitination of SP1, YAP, and PD-L1, as well as its impact on the CAS6/AXL signaling pathway in bladder cancer progression. Transcriptomic analysis was performed using the GSE3167 dataset to identify key gene expression patterns and regulatory mechanisms. A bladder cancer mouse model was established with control (NC), OE-BAP1, and KD-BAP1 groups to assess the effects of BAP1 overexpression and knockdown. Western blot analysis evaluated the expression levels of BAP1, SP1, YAP, PD-L1, CAS6, AXL, and related signaling proteins. Functional assays, including scratch, Transwell, and colony formation, were conducted to assess cell migratory, invasive, and proliferative capacities. Additional groups included BAP1, SP1 inhibitor, BAP1 + SP1 inhibitor, SP1 + anti-PD-L1 monoclonal antibody, and BAP1 + SP1 + anti-PD-L1 combination to evaluate the interplay of these regulatory mechanisms. BAP1 overexpression significantly increased the expression of SP1, YAP, PD-L1, CAS6, AXL, and downstream signaling proteins (PI3K, STAT3, ERK½, MMP-2, and MMP-9), while BAP1 knockdown reduced their levels. Functional assays showed that the BAP1 group exhibited significantly enhanced migratory, invasive, and proliferative abilities compared to controls. Inhibiting SP1 or combining SP1 inhibition with anti-PD-L1 treatment effectively reduced migration, invasion, and proliferation, particularly after 48 h. BAP1 promotes bladder cancer progression by inhibiting the ubiquitination of SP1, YAP, and PD-L1 and activating the CAS6/AXL signaling pathway. These findings highlight BAP1 as a potential therapeutic target for bladder cancer treatment.