Cancer-associated fibroblast subtypes in the tumor microenvironment of prostate cancer and associations to patient outcomes.

Prostate cancer (PC) is a prevalent malignancy, and outcomes range from indolent disease to terminal illness. Prostate-specific antigen-based diagnostics lack specificity and correlation with tumor aggressiveness, leading to overdiagnosis and undertreatment. Recent studies on cancer-associated fibroblasts (CAFs) have identified antigen presenting CAFs (apCAF), inflammatory CAFs (iCAF), and myofibrillar CAFs (myCAF) in pancreatic ductal adenocarcinoma, non-small-cell lung cancer, and breast cancer. However, their significance in PC is not yet understood. This study employs publicly available single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics (ST) data combined with multiplex immunofluorescence (mIF) and digital pathology analyses of radical prostatectomy (RP) specimens from two cohorts (cohort 1, n = 235; cohort 2, n = 240) to identify CAF subtypes in localized PC and their association with biochemical recurrence (BCR) by uni- and multivariable [adjusted for Cancer of the Prostate Risk Assessment postsurgical (CAPRA-S) score] Cox regression analyses. We identified myCAFs, iCAFs, and apCAFs in PC by analyzing scRNA-seq and ST data. We also identified the three CAF subtypes by mIF staining of RP specimens from cohorts 1 and 2. In prostate tumors, higher numbers of apCAFs and myCAFs were present close to malignant versus adjacent nonmalignant (AN) glands (p < 0.001, Wilcoxon test), whereas we saw no significant difference for iCAFs. In univariable Cox regression analyses, high levels of apCAFs and iCAFs were associated with increased risk of BCR in cohort 1 [apCAF: hazard ratio (HR): 1,78, p < 0.05, iCAF: HR: 1,76, p < 0.05] and confirmed in cohort 2 (apCAF: HR: 1.85, p < 0.05, iCAF: HR: 2.06, p < 0.05). In multivariable Cox regression analyses, both apCAF and iCAF levels remained independently associated with BCR after adjustment for CAPRA-S score. Our findings imply the potential of CAF subtypes as biomarkers for risk stratification in PC. © 2026 The Pathological Society of Great Britain and Ireland.