Abstract:
Cancer-associated fibroblasts (CAFs) are core regulators in the tumor microenvironment. Their high heterogeneity and plasticity remarkably influence the infiltration and function of CD8+ T cells, thereby determining the response to immunotherapy. However, the mechanisms by which CAFs impede CD8+ T cell infiltration exhibit substantial heterogeneity across different cancer types. This review proposes a dichotomous model of CAFs-mediated immune exclusion: Type Ⅰ active exclusion (exemplified by pancreatic ductal adenocarcinoma, where CAFs create physical and chemical barriers through excessive extracellular matrix deposition and secretion of TGF-β/CXCL12) and Type Ⅱ immune ignorance (exemplified by a subset of microsatellite-stable colorectal cancers, where loss of CAFs function results in insufficient chemokine production). Under this framework, we systematically review the specific regulatory mechanisms of CAFs subsets, specifically myofibroblastic CAFs and inflammatory CAFs, in pancreatic cancer, triple-negative breast cancer, non-small cell lung cancer, and colorectal cancer, highlighting their multidimensional roles in extracellular matrix remodeling, metabolic reprogramming, and construction of immunosuppressive networks. Furthermore, by integrating single-cell and spatial multi-omics perspectives, we propose immune phenotype-based CAFs-targeting strategies, namely, "barrier-breaking" strategies (TGF-β inhibition and FAP targeting) for Type Ⅰ tumors and "activating" strategies (reprogramming CAFs toward an immune-supportive phenotype) for Type Ⅱ tumors, and discuss their temporally sequenced combination with immune checkpoint inhibitors.