Evaluating immunotherapy response in bladder cancer patients by spatially interrogating PD-1/PD-L1 interaction 2258170

Abstract Introduction Protein-protein interaction is one of the many mechanisms where individual cells communicate with nearby cells or extracellular matrix to modulate the environment. Visualizing these interactions using a spatial platform can validate known interactions implicated in disease pathology, especially cancer. We developed the ProximityScope™ assay that can be used with the RNAscopeTM Multiomic LS assay to visualize protein interactions, proteins, and mRNA on a single tissue section. Methods Antibodies were conjugated to oligonucleotides designed to bind RNAscope signal amplification complexes. The entire workflow was performed using the fully automated Leica BOND RX system. The assay detects 1 interaction with 5 RNA/protein targets and was deployed on samples from patients with localized, muscle-invasive bladder cancer who received neoadjuvant anti-PD-L1 checkpoint inhibitor therapy prior to surgery on a clinical trial (NCT02451423). To characterize tumor-immune microenvironment of these patients, PD-1/PD-L1 interactions were assessed with protein markers for immune and tumor cells (CD3, CD4, CD8, FoxP3, and PanCK) and activation markers (IFNG, GZMB, GZMK). Results We visualized PD-1/PD-L1 interactions, proteins and RNA targets within the tumor before and after immunotherapy treatment. The PD-1/PD-L1 interaction between CD4+ or CD8+ T cells and CK+ tumor cells, showed significant reduction in responder samples than non-responder samples. Additionally, responder samples showed a decrease in percent of tumor-infiltrating regulatory and cytotoxic T cells. These results demonstrate that while anti-PD-L1 may not induce an increase in CD8+ T cell recruitment overall, this treatment modulates PD-1/PD-L1 interaction between specific cell populations. Conclusion Our findings underscore the importance of spatial evaluation of PD-1/PD-L1 interaction alongside cell phenotyping protein and effector molecule encoding RNA in assessing anti-PD-L1 treatment responses. Funding Source n/a Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)