Dataset Information

Microbial Peptides Activate Tumor-Infiltrating Lymphocytes in Glioblastoma

ABSTRACT: Microbial organisms play key roles in numerous physiological processes in the human body and have recently been shown to modify the response to cancer radiotherapy and immune checkpoint inhibitors. Here, we demonstrate that HLA molecules of both glioblastoma tissues as well as tumor cell lines present bacteria-specific peptides. This finding prompted us to examine whether tumor-infiltrating lymphocytes (TILs) recognize intratumoral microbiota. Indeed, bacterial peptides eluted from HLA-DR II molecules are recognized by both TILs, albeit weakly, and peripheral blood-derived memory CD4+ T cells, which, upon stimulation with bacterial peptides, also recognize several tumor antigens. Furthermore, using an unbiased antigen discovery approach for a TIL CD4+ T cell clone (TCC) we show that it recognizes a broad spectrum of peptides from pathogenic bacteria, commensal gut microbiota and also glioblastoma-related tumor antigens. These peptides were strongly stimulatory for bulk TILs and peripheral blood memory cells. Our data hint at how bacterial pathogens and bacterial gut microbiota can be involved in specific immune recognition of tumor antigens.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Brain

DISEASE(S): Brain Glioblastoma Multiforme

SUBMITTER: Reza Naghavian

LAB HEAD: Professor Dr.Roland Martin

PROVIDER: PXD036811 | Pride | 2023-02-20

REPOSITORIES: Pride

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			Action	DRS
	160316_DK_AUT01-DN02_Brain_Tue39L243_8_DDA_1_400-1000mz_msms7_standard.raw	Raw
	160316_DK_AUT01-DN02_Brain_Tue39L243_8_DDA_2_400-1000mz_msms8_standard.raw	Raw
	160316_DK_AUT01-DN02_Brain_Tue39L243_8_DDA_3_400-1000mz_msms9_standard.raw	Raw
	160927_AM_AUT01-DN06_Brain_Tue39L243_10_DDA_1_400-1000mz_msms43_standard.raw	Raw
	160927_AM_AUT01-DN06_Brain_Tue39L243_10_DDA_2_400-1000mz_msms44_standard.raw	Raw

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Project description:Tumor antigens are central to antitumor immunity. Recent evidence suggests that peptides from non-canonical (nonC) aberrantly translated proteins can be presented on HLA-I by tumor cells. Here, we investigated the presentation and immunogenicity of nonC antigens across different cancer types to better understand their contribution to cancer immunosurveillance and to address whether they could be exploited therapeutically. To this end, we employed a proteogenomics pipeline to identify nonC HLA-I ligands derived from off-frame translation of coding sequences and non-coding regions (UTR, ncRNA, intronic and intergenic) in patient-derived tumor cell lines (TCL) of different histological types (4 gynecological cancer, 3 melanoma and 2 head and neck cancer patients). First, peptides bound to HLA-I were isolated and analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) using state-of-the-art procedures. Amino acid (Aa) sequences were identified through the previously described pipeline Peptide-PRISM, with some modifications. Briefly, for each MS spectrum, the top 10 candidates were first identified by de novo sequencing and later mapped to a database including the 3-frame transcriptome and 6-frame genome. Additionally, whole-exome sequencing (WES) information of each TCL was included to interrogate the presentation of mutated peptides derived cancer-specific NSM. The false-discovery rate (FDR) was calculated independently for each category considering the search space and peptide length in a stratified mixture model as previously described. Next, in order to select nonC peptides preferentially presented by tumor cells, immunopeptidomics data from several healthy tissues and samples available from the HLA ligand atlas was used to filter out peptides presented in healthy tissues. To overcome a potential bias toward frequent alleles, the peptides were excluded at the ORF level rather than the Aa sequence. As a result, we found that from a total of 839 unique nonC peptides detected in our tumor samples, 38.5% were predicted to derive from ORFs also present in healthy tissue (nonC-HL). Hence, 61.6% (n=517) were considered preferentially presented on tumor HLA-I, referred to as non-canonical tumor ligands (nonC-TL). Out results showed that, although nonC-TL constitued the most abundant source of candidate tumor antigens, as compared to neoantigens, cancer-germline or melanoma-associated antigens, pre-existing antitumor T cells in cancer patients preferentially recognized neoantigens rather than nonC-TL. Nonetehless, nonC-TL elicited de novo T-cell responses via in vitro sensitization of donor lymphocytes. We identified TCRs specific to three nonC-TL, two of which mapped to the 5’ UTR regions of HOXC13 and ZKSCAN1, and one mapping to a non-coding spliced variant of the C5orf22C. These immunogenic nonC-TL were expressed across tumor types but were barely or not detected in healthy cells. Our findings predict a limited contribution of nonC-TL to cancer immunosurveillance but demonstrate they are attractive novel targets for widely applicable immunotherapies.

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Microbial Peptides Activate Tumor-Infiltrating Lymphocytes in Glioblastoma

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