SFRP4+ cancer-associated fibroblasts drive IL-6/STAT3-mediated EMT and immunosuppressive tumor microenvironment in hepatocellular carcinoma

Background: Secreted frizzled-related protein 4 (SFRP4) is a Wnt modulator, and SFRP4⁺ fibroblast subsets have recently been identified across various cancer types. However, evidence that SFRP4⁺ cancer-associated fibroblasts (CAFs) directly mediate immunosuppression and therapeutic resistance in hepatocellular carcinoma (HCC) remains limited. This study aimed to elucidate how SFRP4⁺ CAFs reprogram the tumor microenvironment (TME) to drive immune suppression and treatment resistance in HCC. Methods: Whole-transcriptome sequencing (WTS) was performed on eight matched CAF and paracancer fibroblast (PAF) pairs from HCC patients, and five publicly available HCC datasets were integrated to identify candidate genes. Cell-cell interactions in the TME were analyzed using CellChat analysis in the GepLiver database. Functional validation was conducted through in vitro coculture assays using primary CAFs and HCC cell lines, as well as in vivo xenograft and humanized mouse models. Transcriptomic profiling of tumors from atezolizumab-bevacizumab (Atezo/Beva) responder and non-responder groups was further performed to assess clinical relevance. Results: SFRP4⁺ CAFs exhibited an inflammatory phenotype characterized by marked induction of IL6 and NECTIN2 expression. Coculture of HCC cells with SFRP4⁺ CAFs increased phosphorylated STAT3 and CD44 expression, enhancing proliferation, invasion, and stemness, while these effects were abrogated by SFRP4 knockdown. In the immune compartment, SFRP4⁺ CAFs promoted regulatory T-cell (Treg) infiltration via NECTIN-TIGIT interactions and induced M2 macrophage polarization, establishing an immunosuppressive milieu. In the humanized mouse model, tumors co-implanted with SFRP4⁺ CAFs showed increased Treg infiltration and M2 polarization based on enrichment score analysis. Clinically, Atezo/Beva non-responder tumors exhibited upregulation of SFRP4, IL6-STAT3/CD44, and NECTIN-TIGIT pathways, accompanied by reduced CD8A and GZMA expression. Conclusions: SFRP4⁺ CAFs orchestrate a multifaceted pro-tumor program through IL6-STAT3/CD44 signaling, NECTIN-TIGIT-mediated Treg recruitment, and M2 macrophage polarization. High SFRP4 expression correlates with impaired cytotoxic immunity and poor response to Atezo/Beva therapy in HCC. Targeting SFRP4⁺ CAFs may represent a promising therapeutic strategy to overcome stromal-mediated immune resistance in liver cancer.