Abstract
It is becoming increasingly apparent that the majority of tumours display defects in the MHC class I antigen processing pathway, particularly low levels of the transporters-associated with antigen processing (TAP) and tapasin. Thus, immunotherapy approaches targeting such tumours with CD8+ cytotoxic T lymphocytes (CTL) requires strategies to overcome these defects. Previously we had identified an antigen processing pathway by which cytosolically derived hydrophobic peptides could be presented in the absence of TAP. Here we show in the tapasin-negative cell line 721.220 that a number of these hydrophobic TAP-independent peptides can also be presented in a tapasin-independent manner. Yet when these experiments were extended to tumour cell lines derived from small cell lung cancer (SCLC), which we show to be tapasin deficient in addition to TAP-negative, the TAP-, tapasin-independent peptides were not presented. This lack of presentation could be rectified by pre-treatment of SCLC cells with IFNgamma. Alternatively, by directing the TAP-, tapasin-independent peptides into the endoplasmic reticulum (ER) via an ER signal sequence, these peptides were presented efficiently by SCLC cells. We infer from this data that the TAP-independent pathway for presentation of hydrophobic peptides generates a low concentration of peptide in the ER and, for tumour cells which also lack tapasin, this concentration of antigenic peptide is insufficient to load onto MHC class I molecules. Thus, for immunotherapeutic approaches to target SCLC and other tumours with defects in the MHC class I antigen processing pathway it will be important to consider strategies that address tapasin-defects.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ATP Binding Cassette Transporter, Subfamily B, Member 2
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ATP Binding Cassette Transporter, Subfamily B, Member 3
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ATP-Binding Cassette Transporters / genetics
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ATP-Binding Cassette Transporters / physiology*
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Antigen Presentation*
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Antigens, Viral / immunology*
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Antigens, Viral / metabolism
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CD8-Positive T-Lymphocytes / immunology*
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Carcinoma, Small Cell / pathology
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Cell Line, Transformed
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Cell Line, Tumor
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Cytosol / metabolism
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Endoplasmic Reticulum / metabolism*
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HLA-A Antigens / immunology
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HLA-A2 Antigen / immunology
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HLA-A24 Antigen
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Herpesvirus 4, Human / immunology
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Histocompatibility Antigens Class I / immunology*
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Humans
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Hydrophobic and Hydrophilic Interactions
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Immediate-Early Proteins / immunology
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Immediate-Early Proteins / metabolism
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Intracellular Membranes / metabolism
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Lung Neoplasms / pathology
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Membrane Transport Proteins / deficiency
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Membrane Transport Proteins / physiology*
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Peptide Fragments / chemistry
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Peptide Fragments / immunology*
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Peptide Fragments / metabolism
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Phosphoproteins / immunology
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Phosphoproteins / metabolism
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Protein Sorting Signals / physiology
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Protein Transport
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T-Cell Antigen Receptor Specificity
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Trans-Activators / immunology
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Trans-Activators / metabolism
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Transfection
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Viral Matrix Proteins / immunology
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Viral Matrix Proteins / metabolism
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Viral Proteins / immunology
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Viral Proteins / metabolism
Substances
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ATP Binding Cassette Transporter, Subfamily B, Member 2
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ATP Binding Cassette Transporter, Subfamily B, Member 3
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ATP-Binding Cassette Transporters
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Antigens, Viral
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BRLF1 protein, Human herpesvirus 4
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EBV-associated membrane antigen, Epstein-Barr virus
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Epstein-Barr virus early antigen diffuse component
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HLA-A Antigens
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HLA-A2 Antigen
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HLA-A24 Antigen
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Histocompatibility Antigens Class I
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Immediate-Early Proteins
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Membrane Transport Proteins
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Peptide Fragments
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Phosphoproteins
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Protein Sorting Signals
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SM protein, Human herpesvirus 4
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TAP1 protein, human
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Trans-Activators
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Viral Matrix Proteins
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Viral Proteins
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tapasin
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TAP2 protein, human