Deciphering the Role of Cancer-Associated Fibroblasts in Bladder Cancer Progression and Tumor Immune Microenvironment

About This Grant

PROJECT SUMMARY & ABSTRACT Bladder cancer is a prevalent and recurrent malignancy, with approximately 80,000 new cases and 17,000 deaths annually in the United States. For patients with high-risk non-muscle invasive bladder cancer (NMIBC), Bacillus Calmette-Guérin (BCG) immunotherapy remains the only FDA-approved frontline treatment. However, up to 40% of patients recur, and 15–20% progress to muscle-invasive disease. While immune checkpoint inhibitors (ICIs) are approved for BCG-unresponsive NMIBC, response rates remain modest, and reliable predictive biomarkers are lacking. Increasing evidence suggests that cancer-associated fibroblasts (CAFs) in the tumor microenvironment contribute to immune modulation and therapeutic resistance. Yet, in bladder cancer, CAF subtypes remain poorly defined and have not been consistently linked to treatment outcomes. The applicant’s research has identified three distinct and reproducible CAF subtypes in NMIBC using single- cell RNA sequencing across two independent datasets: one inflammatory (iCAF) and two myofibroblastic (myCAF) populations. The iCAF subtype is enriched for cytokine signaling and is associated with worse progression-free survival following BCG, but improved relapse-free survival following ICI therapy. To enable translational application, the applicant developed a Fibroblast Intrinsic Gene (FIG) signature that classifies CAF subtypes from bulk RNA-seq data by capturing fibroblast-specific transcriptional programs. Notably, iCAFs exhibit elevated expression of FGFR1, a receptor known to regulate fibroblast biology and extracellular matrix remodeling, though its functional role in CAF-mediated therapy response remains unknown. In Aim 1, the applicant will establish and characterize patient-derived CAF cultures, use fibroblast activation markers to assign subtype identity, and investigate the functional importance of FGFR1 signaling using pharmacologic inhibition and CRISPR-Cas9-mediated knockout. In Aim 2, the applicant will utilize a murine bladder cancer model with co-injection of murine CAFs and tumor cells to evaluate how iCAF and myCAF subtypes influence anti-PD-1 immunotherapy response and immune cell infiltration. This project will elucidate the role of CAF subtypes in modulating immunotherapy response in bladder cancer and establish a foundation for stromal-based biomarkers to guide treatment selection. The proposed training will provide the applicant with comprehensive experience in tumor immunology, bioinformatics, and preclinical modeling, key skills for a future physician-scientist leading research in cancer microenvironment and translational immunotherapy.