Journal Article

Enhanced antigen cross-presentation in human colorectal cancer-associated fibroblasts through upregulation of the lysosomal protease cathepsin S

de Bruin, Linda, Griffioen, Lisa, Mulder, Arend, van der Heden van Noort, Gerbrand J, Wiertz, Emmanuel JHJ, Neefjes, Jacques, Hawinkels, Lukas JAC, Hardwick, James CH, van Veelen, Peter A, Plug, Léonie, Harryvan, Tom J, Van der Burg, Sjoerd H, Verdegaal, Els ME, Jongsma, Marlieke LM, Visser, Marten, Van Hall, Thorbald, Meeuwsen, Miranda H, Santegoets, Saskia J

2022

Overview

BackgroundCross-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.MethodsIn 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.ResultsHere, 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.ConclusionThese data indicate that CAFs may directly suppress tumor-specific T cell function in an antigen-dependent fashion in human CRC.

• Publisher: BMJ Publishing Group Ltd,BMJ Publishing Group LTD,BMJ Publishing Group
• Subject: Antigen presentation / Basic Tumor Immunology / Cancer / Colorectal cancer / Cytotoxicity / Fibroblasts / gastrointestinal neoplasms / Gene expression / Immunotherapy / Lymphocytes / Melanoma / Peptides / Proteins