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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.

SUBMITTER: Chornoguz O

PROVIDER: S-EPMC3494186 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

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Major histocompatibility complex class II+ invariant chain negative breast cancer cells present unique peptides that activate tumor-specific T cells from breast cancer patients.

Chornoguz Olesya O Gapeev Alexei A O'Neill Michael C MC Ostrand-Rosenberg Suzanne S

Molecular & cellular proteomics : MCP 20120831 11

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 I ...[more]

PMID: 22942358

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Project description:We have investigated the effects of phospholipids on activation and proliferation of ovarian and breast cancer cells. Lysophosphatidic acid (LPA), lysophosphatidylserine (LPS) and sphingosylphosphorylcholine (SPC) all induce transient increases in cytosolic free Ca2+ ([Ca2+]i) in both ovarian and breast cancer cell lines. The ability of LPA, LPS and SPC to induce increases in [Ca2+]i in ovarian and breast cancer cells is likely to be due to an interaction with cell-surface receptors as the increases in [Ca2+]i were: (1) due to release of calcium from intracellular stores and not from transmembrane uptake due to changes in permeability; (2) blocked by lanthanum and suramin which do not enter cells; (3) blocked by phorbol esters which interrupt increases in [Ca2+]i induced through a number of different receptors; and (4) not detected in freshly isolated peripheral blood mononuclear cells, indicating cell type specificity. In addition, increases in [Ca2+]i induced by LPA, LPS and SPC in ovarian and breast cancer cells completely self-desensitized and cross-desensitized each other, but did not block increases in [Ca2+]i induced by thrombin. Lysophosphatidylglycerol (LPG), but not other lysophospholipids, inhibited LPA- but not LPS- or SPC-induced increases in [Ca2+]i, suggesting that LPA may interact with a different receptor(s) to LPS or SPC and that their downstream signalling pathways converge or interact. LPA, SPC and LPS also induced rapid increases in tyrosine phosphorylation of specific cellular proteins, including p125FAK. Strikingly, LPA, but not LPS or SPC, induced activation of mitogen-activated protein (MAP) kinases. Despite an ability to activate similar intracellular signaling events, LPA, LPS and SPC exhibited markedly different effects on cell proliferation. Whereas LPA induced a significant increase in cell proliferation, LPS did not substantially alter cell proliferation and SPC inhibited cell proliferation. Surprisingly, phosphatidic acid (PA), which did not induce increases in [Ca2+]i, p125FAK activation or activation of MAP kinases, did induce proliferation of ovarian cancer cells, albeit at higher concentrations that LPA. The discordance between sensitivity to LPG, early biochemical events stimulated, and the eventual proliferation response combine to suggest that LPA probably utilizes a different receptor from LPS, SPC and PA. Therefore ovarian and breast cancer cells are sensitive to the effects of a number of different phospholipids which may play a role in the growth of these tumour cells in the cancer patient and are thus potential targets for therapy.

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Major histocompatibility complex class II+ invariant chain negative breast cancer cells present unique peptides that activate tumor-specific T cells from breast cancer patients.

Publications

Major histocompatibility complex class II+ invariant chain negative breast cancer cells present unique peptides that activate tumor-specific T cells from breast cancer patients.

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