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

ABSTRACT: 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. It is currently unknown 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. Here we show that human colorectal cancer (CRC)-derived CAFs display an enhanced capacity to cross-present neoantigen-derived synthetic long peptides (SLPs) when compared to normal colonic fibroblasts. Importantly, cross-presentation of antigens required 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 (CD25, CD137) and increased exhaustion (TIM3) marker expression. Our data indicate that CAFs may directly suppress tumor-specific T cell function in an antigen-dependent fashion in human CRC.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: G Janssen

LAB HEAD: P.A. van Veelen

PROVIDER: PXD029507 | Pride | 2022-03-03

REPOSITORIES: Pride

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Project description:Immune evasion is an important hallmark of cancer ensured by diverse strategies, including immunosuppression and downregulation of antigen presentation. Here, to restore immunogenicity of cancer cells, we employed the minimal gene regulatory network of highly immunogenic type 1 conventional dendritic cells (cDC1) to reprogram cancer cells into professional antigen presenting cells (APCs). We showed that enforced expression of PU.1, IRF8 and BATF3 (PIB) was sufficient to induce cDC1 phenotype in 33 cell lines derived from human and mouse hematological and solid tumors. PIB gradually modified the cancer cell transcriptional and epigenetic program imposing global antigen presentation and cDC1 gene signatures within 9 days. cDC1 reprogramming restored the expression of antigen presentation complexes as well as co-stimulatory molecules at the cell surface, leading to the presentation of endogenous antigens on MHC-I, and to CD8+ T cell mediated killing. Functionally, tumor- APCs acquired the ability to uptake and process exogenous proteins and dead cells, secreted inflammatory cytokines and cross-presented antigens to naïve CD8+ T cells. Importantly, tumor-APCs were efficiently generated at the single cell level from primary cancer cells of 7 solid tumors that presented antigens to memory and naïve T-cells, as well as to activated patient-specific intra-tumoral lymphocytes. Alongside antigen presentation, tumor-APCs harboring TP53, KRAS and PTEN mutations showed impaired tumorigenicity in vitro and in vivo. Finally, using in vivo mouse models of melanoma, we showed that intra-tumoral injection of tumor-APCs promoted lymphoid infiltration, delayed tumor growth and increased survival. The anti-tumor immunity elicited by tumor-APCs was synergistic with immune checkpoint inhibitors enabling tumor eradication. Our approach combines cDC1’s antigen processing and presenting abilities with endogenous generation of tumor antigens and serves as a platform for the development of novel immunotherapies based on endowed antigen presentation in cancer cells.

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

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