title: Major histocompatibility complex class II+ invariant chain negative breast cancer cells present unique peptides that activate tumor-specific T cells from breast cancer patients.
abstract: The major histocompatibility complex (MHC) class II-associated Invariant chain (Ii) is present in professional antigen presenting cells where it regulates peptide loading onto MHC class II molecules and the peptidome presented to CD4+ T lymphocytes. Because Ii prevents peptide loading in neutral subcellular compartments, we reasoned that Ii- cells may present peptides not presented by Ii+ cells. Based on the hypothesis that patients are tolerant to MHC II-restricted tumor peptides presented by Ii+ cells, but will not be tolerant to novel peptides presented by Ii- cells, we generated MHC II vaccines to activate cancer patients' T cells. The vaccines are Ii- tumor cells expressing syngeneic HLA-DR and the costimulatory molecule CD80. We used liquid chromatography coupled with mass spectrometry to sequence MHC II-restricted peptides from Ii+ and Ii- MCF10 human breast cancer cells transfected with HLA-DR7 or the MHC Class II transactivator CIITA to determine if Ii- cells present novel peptides. Ii expression was induced in the HLA-DR7 transfectants by transfection of Ii, and inhibited in the CIITA transfectants by RNA interference. Peptides were analyzed and binding affinity predicted by artificial neural net analysis. HLA-DR7-restricted peptides from Ii- and Ii+ cells do not differ in size or in subcellular location of their source proteins; however, a subset of HLA-DR7-restricted peptides of Ii- cells are not presented by Ii+ cells, and are derived from source proteins not used by Ii+ cells. Peptides from Ii- cells with the highest predicted HLA-DR7 binding affinity were synthesized, and activated tumor-specific HLA-DR7+ human T cells from healthy donors and breast cancer patients, demonstrating that the MS-identified peptides are bonafide tumor antigens. These results demonstrate that Ii regulates the repertoire of tumor peptides presented by MHC class II+ breast cancer cells and identify novel immunogenic MHC II-restricted peptides that are potential therapeutic reagents for cancer patients.
authors.affiliation: Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland, USA.
authors.forename: Olesya
authors.initials: O
authors.lastname: Chornoguz
authors.forename: Alexei
authors.initials: A
authors.lastname: Gapeev
authors.forename: Michael C
authors.initials: MC
authors.lastname: O'Neill
authors.forename: Suzanne
authors.initials: S
authors.lastname: Ostrand-Rosenberg
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017951:Antigen Presentation / Q000276:immunology*; D000938:Antigen-Presenting Cells / Q000276:immunology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000737:chemistry / Q000276:immunology*; D001943:Breast Neoplasms / Q000276:immunology* / Q000517:prevention & control; D019496:Cancer Vaccines / Q000276:immunology; D045744:Cell Line, Tumor; D005260:Female; D006684:HLA-DR Antigens / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000737:chemistry / Q000276:immunology*; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology*; D010641:Phenotype; D011485:Protein Binding; D013601:T-Lymphocytes / Q000276:immunology*; D014019:Tissue Donors; D014161:Transduction, Genetic
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D019496:Cancer Vaccines; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D010455:Peptides; C045084:invariant chain