Predicting PD-1/PD-L1 status in bladder cancer with 18F-FDG PET?

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.

Immuno-PET imaging of 68Ga-labeled nanobody Nb109 for dynamic monitoring the PD-L1 expression in cancers

The checkpoint blockade immunotherapy has become a potent treatment strategy for cancers, and programmed death ligand-1 (PD-L1) is a prominent checkpoint ligand that is highly expressed in some cancers. The identification of immune checkpoint marker PD-L1 is critical for improving the success of immunotherapy. Accordingly, the binding specificity and dynamic monitoring property of a non-blocking nanobody tracer ⁶⁸Ga-NOTA-Nb109 to PD-L1 were assessed in this study. The endogenous expression level of PD-L1 in several cancer cells was measured by flow cytometry, Western blot, and cellular uptake assay. Sensitivity and specificity of ⁶⁸Ga-NOTA-Nb109 in monitoring the expression of PD-L1 in vivo were evaluated by PET imaging of different tumor-bearing models (U87, high PD-L1 expression; HCT 116, medium PD-L1 expression; and NCI-H1299, low PD-L1 expression). In vivo PET imaging results agreed well with those detected in vitro. In addition, PET imaging of PD-L1 expression in U87 and NCI-H1299 xenografts using ¹⁸F-FDG was also performed for comparison. The maximum tumor-to-muscle uptake ratio of ⁶⁸Ga-NOTA-Nb109 was more than twofold that of ¹⁸F-FDG in U87 xenograft. The change of PD-L1 expression in NCI-H1299 cells and xenografts induced by cisplatin (CDDP) was sensitively monitored by ⁶⁸Ga-NOTA-Nb109. This study demonstrated the feasibility of tracer ⁶⁸Ga-NOTA-Nb109 for specifically targeting endogenous PD-L1 and dynamic monitoring the change of PD-L1 expression, and could guide the immunotherapy and immunochemotherapy for refractory cancers.