YAP1 Inhibition Induces Phenotype Switching of Cancer-Associated Fibroblasts to Tumor Suppressive in Prostate Cancer

Prostate Cancer (PCa) rarely responds to immune-checkpoint blockade (ICB) therapies. Cancer-associated fibroblasts (CAFs) are critical components of the immunologically "cold" tumor microenvironment and are considered a promising target to enhance the immunotherapy response. In this study, we aimed to reveal the mechanisms regulating CAF plasticity to identify potential strategies to switch CAFs from pro-tumorigenic to anti-tumor phenotypes and enhance ICB efficacy in PCa. Integration of four PCa single-cell RNA-sequencing datasets defined pro-tumorigenic and anti-tumor CAFs, and RNA-seq, flow cytometry, and a PCa Organoid model demonstrated the functions of two CAF subtypes. Extracellular matrix-associated CAFs (ECM-CAF) promoted Collagen deposition and Cancer cell progression, and lymphocyte-associated CAFs (Lym-CAF) exhibited an anti-tumor phenotype and induced the infiltration and activation of CD8+ T cells. YAP1 activity regulated the ECM-CAF phenotype, and YAP1 silencing promoted switching to Lym-CAFs. NF-κB p65 was the core transcription factor in the Lym-CAF subset, and YAP1 inhibited nuclear translocation of p65. Selective depletion of YAP1 in ECM-CAFs in vivo promoted CD8+ T-cell infiltration and activation and enhanced the therapeutic effects of anti- PD-1 treatment in PCa. Overall, this study revealed a mechanism regulating CAF identity in PCa and highlighted a therapeutic strategy for altering the CAF subtype to suppress tumor growth and increase sensitivity to ICB.