Abstract 6475: Characterizing peri-tumoral tertiary lymphoid structures in non-muscle invasive bladder cancer using a spatial whole transcriptomics approach

Abstract Background: Intravesical Bacillus Calmette-Guérin (BCG) immunotherapy is the gold standard for high-risk NMIBC, however over half of patients experience early recurrence or disease progression, highlighting the need for reliable predictive biomarkers. Our previous research identified that B cell dominant peri-tumoral tertiary lymphoid structures (TLSs) evolve during chronic carcinogenesis in a subset of patients who experience early recurrence or progression. TLSs generally correlate with favorable outcomes following treatment with immune checkpoint inhibitors, chemotherapy or oncolytic viruses. In contrast, their abundance in peri-tumoral regions in BCG-naïve NMIBC tumors associates with poor prognosis. This highlights the importance of their in-depth characterization and further exploring their biomarker potential in NMIBC. Methods: Peri-tumoral TLSs and tumor epithelial regions were profiled using the NanoString GeoMx Digital Spatial Profiler based whole transcriptome analysis. Multiplex Immunofluorescence was performed to infer spatial profiles of B, T and myeloid cell functional states as well as immune checkpoint proteins. Results: Spatial whole transcriptome analysis displayed increased expression of genes associated with antigen presentation, complement activation, B cell recruiting chemokines, and immunoglobulins in the TLSs regions. Tumor epithelial regions located adjacent to TLSs showed elevated expression of genes reflective of a luminal subtype. Increased PD-1+ cells in the peri-tumoral regions and enrichment of luminal subtype genes in the epithelial compartment indicated cancer cell intrinsic aggressive features associated with immune exclusion. Conclusion: The novel findings from this study will help establish peri-tumoral TLSs as biomarkers for predicting BCG therapy response, enabling early identification of patients who may benefit from alternative immunomodulatory treatments like oncolytic viruses, gemcitabine-docetaxel chemotherapy, or immune checkpoint inhibitors. Citation Format: Kartik Sachdeva. Characterizing peri-tumoral tertiary lymphoid structures in non-muscle invasive bladder cancer using a spatial whole transcriptomics approach [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6475.