Harryvan et al. demonstrated that CRC-derived CAFs can cross-present neoantigen-derived synthetic long peptide (SLPs), and investigated their effects on tumor-specific CD8+ T cell function. Compared with normal colonic fibroblasts, CRC-derived CAFs showed enhanced cross-presentation capacity and utilized a lysosomal protease cathepsin S-dependent vacuolar pathway. Cathepsin S is expressed by CAFs in human CRC tissue samples, and its expression was upregulated in ex vivo cultured CRC-derived CAFs. CAF-mediated antigen cross-presentation impaired CD8+ T cell effector functions, and induced upregulation of inhibitory molecules TIM3, LAG3, and CD39.
Contributed by Shishir Pant
Background: Cross-presentation of exogenous antigens in HLA-class I molecules by professional antigen presenting cells (APCs) is crucial for CD8+ T cell function. Recent murine studies show that several non-professional APCs, including cancer-associated fibroblasts (CAFs) also possess this capacity. Whether human CAFs are able to cross-present exogenous antigen, which molecular pathways are involved in this process and how this ultimately affects tumor-specific CD8+ T cell function is unknown.
Methods: In this study, we investigated the ability of human colorectal cancer (CRC)-derived CAFs to cross-present neoantigen-derived synthetic long peptides (SLPs), corresponding to tumor-derived mutant peptides, and how this affects tumor-specific T-cell function. Processing of the SLP was studied by targeting components of the cross-presentation machinery through CRISPR/Cas9 and siRNA-mediated genetic ablation to identify the key molecules involved in fibroblast-mediated cross-presentation. Multispectral flow cytometry and killing assays were performed to study the effect of fibroblast cross-presentation on T cell function.
Results: Here, we show that human CRC-derived CAFs display an enhanced capacity to cross-present neoantigen-derived SLPs when compared with normal colonic fibroblasts. Cross-presentation of antigens by fibroblasts involved the lysosomal protease cathepsin S. Cathepsin S expression by CAFs was detected in situ in human CRC tissue, was upregulated in ex vivo cultured CRC-derived CAFs and showed increased expression in normal fibroblasts after exposure to CRC-conditioned medium. Cognate interaction between CD8+ T cells and cross-presenting CAFs suppressed T cell function, reflected by decreased cytotoxicity, reduced activation (CD137) and increased exhaustion (TIM3, LAG3 and CD39) marker expression.
Author Info: (1) Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, The Netherlands. (2) Department of Medical Oncology, Oncode Institute, Leiden Universit
Author Info: (1) Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, The Netherlands. (2) Department of Medical Oncology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands. (3) Department of Medical Oncology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands. (4) Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, The Netherlands. (5) Department of Medical Oncology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands. (6) Department of Immunology, Leiden University Medical Center, Leiden, The Netherlands. (7) Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands. (8) Department of Cell & Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands. (9) Department of Cell & Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands. (10) Department of Hematology, Leiden University Medical Center, Leiden, The Netherlands. (11) Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands. (12) Department of Medical Oncology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands. (13) Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, The Netherlands. (14) Department of Medical Oncology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands. (15) Department of Cell & Chemical Biology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands. (16) Department of Medical Oncology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands. (17) Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, The Netherlands. (18) Department of Medical Oncology, Oncode Institute, Leiden University Medical Center, Leiden, The Netherlands e.m.e.verdegaal@lumc.nl.
