Dataset Information

Mapping the soluble human leukocyte antigen peptidome of pleural effusions reveals lung and tumor-associated antigens

ABSTRACT: Soluble HLA (sHLA) molecules released to the plasma, carry their original peptide cargo and provide insight into the protein synthesis and degradation schemes of their source cells and tissues. Other body fluids, such as pleural effusions, may also contain sHLA-peptide complexes, and can potentially serve as a source of tumor antigens since these fluids are drained from the tumor microenvironment. Thus, we developed a methodology for purifying and analysing large pleural effusion sHLA class I peptidomes of patients inflicted with malignancies or benign diseases. The cleared pleural fluids, the cell pellets present in the pleural effusions, and the primary tumor cells cultured from cancer patients’ effusions, were used for immunoaffinity purification of the HLA molecules. The recovered HLA peptides were analyzed by capillary chromatography coupled to tandem mass spectrometry and the resulting LC-MS/MS data was analyzed with the MaxQuant software tool. Large HLA peptidomes were obtained by the analysis of the pleural effusions. The majority of peptides identified from the pleural effusions were defined as HLA ligands that fit the patients’ HLA consensus sequence motifs. The membranal and soluble HLA peptidomes of each individual patient were somewhat similar to each other. Many of the HLA peptides were derived from known tumor-associated antigens, lung-related proteins, and VEGF pathway proteins. Thus, the pleural effusion HLA peptidome of patients with malignant tumors can serve as a rich source of biomarkers for tumor diagnosis and personalized immunotherapy.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Pleural Fluid, Cell Line Cell

DISEASE(S): Non-small Cell Lung Carcinoma

SUBMITTER: Dganit Melamed Kadosh

LAB HEAD: Arie Admon

PROVIDER: PXD027766 | Pride | 2022-05-25

REPOSITORIES: Pride

ACCESS DATA

Dataset's files

Source:

			Action	DRS
	Human_proteome_June_2019_74416_entries.fasta	Fasta
	MaxQuant_1.6.10.43.zip	Other
	Mutations_P12.fasta	Fasta
	Mutations_P13.fasta	Fasta
	Mutations_P14.fasta	Fasta

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Publications

Soluble HLA peptidome of pleural effusions is a valuable source for tumor antigens.

Khazan-Kost Sofia S Cafri Gal G Melamed Kadosh Dganit D Mooshayef Navit N Chatterji Sumit S Dominissini Dan D Manor Sigal S Zisser Bracha B Broday Limor L Talalai Efrosiniia E Shemer Anat A Zadok Oranit O Ofek Efrat E Onn Amir A Admon Arie A Peled Michael M

Journal for immunotherapy of cancer 20220501 5

<h4>Background</h4>Soluble human leucocyte antigen (sHLA) molecules, released into the plasma, carry their original peptide cargo and provide insight into the protein synthesis and degradation schemes of their source cells and tissues. Other body fluids, such as pleural effusions, may also contain sHLA-peptide complexes, and can potentially serve as a source of tumor antigens since these fluids are drained from the tumor microenvironment. We explored this possibility by developing a methodology ...[more]

PMID: 35580925

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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.