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: Olesya Chornoguz, Alexei Gapeev, Michael C O'Neill, Suzanne Ostrand-Rosenberg
• Journal: Molecular & cellular proteomics : MCP (Mol Cell Proteomics) Vol. 11 Issue 11 Pg. 1457-67 (Nov 2012) ISSN: 1535-9484 [Electronic] United States
• PMID: 22942358 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Antigens, Differentiation, B-Lymphocyte
• Cancer Vaccines
• HLA-DR Antigens
• Histocompatibility Antigens Class II
• Peptides
• invariant chain

Topics

• Amino Acid Motifs
• Amino Acid Sequence
• Antigen Presentation (immunology)
• Antigen-Presenting Cells (immunology)
• Antigens, Differentiation, B-Lymphocyte (chemistry, immunology)
• Breast Neoplasms (immunology, prevention & control)
• Cancer Vaccines (immunology)
• Cell Line, Tumor
• Female
• HLA-DR Antigens (immunology)
• Histocompatibility Antigens Class II (chemistry, immunology)
• Humans
• Lymphocyte Activation (immunology)
• Mass Spectrometry
• Molecular Sequence Data
• Peptides (chemistry, immunology)
• Phenotype
• Protein Binding
• T-Lymphocytes (immunology)
• Tissue Donors
• Transduction, Genetic