Abstract 1408: Intrahepatic IgA complex induces polarization of cancer-associated fibroblasts to matrix phenotypes in the tumor microenvironment of HCC

Abstract Background and Aims: Cancer-associated fibroblasts (CAFs) are activated fibroblasts that play key roles in the tumor microenvironment (TME). Immunoglobulin A (IgA) contributes to inflammation and anti-tumor immunity dismantling in the human liver. We investigated the effects of the IgA complex on CAFs in the TME of hepatocellular carcinoma (HCC). Approach and Results: CAF dynamics in HCC TME were analyzed via single-cell RNA sequencing of HCC samples. CAFs were isolated from 40 HCC samples. The isolated CAFs were treated with mock or serum-derived IgA dimers. Following treatment with the mock or serum IgA dimers in vitro, co-culture experiments were performed using CAF and CD8+ T cells. Single-cell analysis showed that sub-cluster proportions in the CAF-fibroblast activation protein-α (FAP) matrix were significantly increased in patients with high serum IgA levels. We were performed flow cytometry on fresh surgical tissues and observed a significant increase in the mean fluorescence intensity (MFI) of FAP in the CD68+ cells from patients with high serum IgA levels compared to those with low serum IgA levels (p<0.001). We validated that the transferrin receptor (CD71) is expressed in CAFs (p<0.01). IgA-treated CAFs exhibited higher programmed death-ligand 1 (PD-L1) expression levels than mock-treated CAFs (p<0.05). Co-culture with CAFs induced the attenuation of the cytotoxic function of activated CD8+ T cell, and these cells co-cultured with IgA-treated CAFs exhibited increased expression levels of programmed death-1 (PD-1) compared to those co-cultured with mock-treated CAFs (p<0.05). Conclusions: Intrahepatic IgA induces polarization of HCC CAFs into more malignant matrix phenotype and attenuates cytotoxic T cell function. Our study uncovers five dynamic CAF subpopulations within HCC tissues and highlights their potential roles in tumor progression and immune suppression. Citation Format: Pil Soo Sung. Intrahepatic IgA complex induces polarization of cancer-associated fibroblasts to matrix phenotypes in the tumor microenvironment of HCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1408.