Investigations of humoral and cellular immune responses directed against MUC1 epithelial mucin in ovarian and breast carcinoma

Tran, Mai Hue (2004). Investigations of humoral and cellular immune responses directed against MUC1 epithelial mucin in ovarian and breast carcinoma PhD Thesis, School of Medicine, The University of Queensland.

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Author Tran, Mai Hue
Thesis Title Investigations of humoral and cellular immune responses directed against MUC1 epithelial mucin in ovarian and breast carcinoma
School, Centre or Institute School of Medicine
Institution The University of Queensland
Publication date 2004
Thesis type PhD Thesis
Supervisor Michael McGuckin
Total pages 283
Collection year 2004
Language eng
Subjects 320000 Medical and Health Sciences
Formatted abstract

The MUC1 epithelial mucin, encoded by the MUC1 gene is a selfantigen present on normal epithelial cells. It is a transmembrane protein with numerous carbohydrates attached to the variable number of tandem repeats of the extracellular domain. In breast, ovarian and many other carcinomas, MUC1 is overexpressed and aberrantly glycosylated exposing new carbohydrate and peptide epitopes on the cell surface that are absent in normal tissues. Whilst the function(s) of MUC1 in normal epithelial tissues remains uncertain, its extracellular domain serves major roles in lubrication and mucosal defense, cell-cell interactions and cell extracellular matrix interactions, and its cytoplasmic tail is involved in signal transduction and interacts with the cytoskeleton. Soluble or secreted MUC1 is immunosuppressive and inhibits T cell proliferation. Cancer associated MUC1 is an antigenically distinct molecule that can be recognised by the immune system and serves as a target antigen for immunotherapy.

The aim of this thesis is to investigate antibody and T-cell immune responses to MUC1 in breast and ovarian cancer, immunosuppressive factors or signalling molecules affecting T cell unresponsiveness in cancer and the expression of MUC1 in haemopoietic cells.

The humoral immune response against MUC1 in breast cancer patients was studied by measuring serum antibodies reactive with MUC1 by ELISA. Natural circulating IgM and IgG antibodies reactive with MUC1 were present in the serum of healthy women (31% and 15%, respectively), breast cancer patients prior to surgery (47% and 20%, respectively), and during primary treatment (variable). Serum concentrations of IgM antibody decreased with age while both IgG antibody and MUC1 antigen was higher in older women than young women. Very high levels of anti-MUC1 IgM and IgG antibodies were detected in serum samples from adenocarcinoma patients vaccinated with MUC1 mannan fusion protein (100% in both cases). The cellular immune response against MUC1 was investigated by studying the proliferative and cytotoxic activity of tumour associated lymphocytes (TALs) derived from ovarian cancer patients in response to MUC1. TALs isolated from ovarian malignant ascites were expanded in vitro with IL2 and irradiated autologous tumour cells (ATC) or MUC1 fusion protein (MFP) pulsed autologous lymphocytes for a minimum of three weeks. The immunophenotype pattern of these TALs varied, consisting of a combination of CD4+ and CD8+ T cells, CD3+ T cells and CD16+ NK cells or predominantly CD4+ T cells. In vitro ATC stimulated TALs showed proliferative responses to ATC but were inhibited by soluble MUC1 including MFP, MUC1 synthetic peptides and MUC1 affinity purified from tissue culture supernatant. The cultured TALs were capable of killing autologous tumour cells and allogeneic MUC1 transfected PE04 ovarian cancer cells and in some cases lysis was inhibited by anti-MUC1 BC2 antibody, indicating recognition of MUC1 in a MHC-unrestricted manner.

Cytotoxic T lymphocytes of cancer patients are often suppressed and the immune system does not respond to tumour cells. TALs from peritoneal fluid of ovarian cancer patients demonstrated decreased expression of T cell signalling proteins, CD3-ζ, and CD3-ε chains, as well as reduced tyrosine phosphorylation of the CD3-ζ, subunit. In vitro culture of these lymphocytes with IL2 restored the expression of CD3-ζand CD3-ε signalling molecules. The peritoneal fluid contained significantly elevated concentrations of MUC1 mucin (p<0.001) and immunosuppressive cytokines, IL6 and IL10 (both p<0.001).

The expression of MUC1 is not restricted to epithelial cells. Flow cytometric analysis with anti-MUC1 BC2 antibody demonstrated MUC1 expression on the surface of naive peripheral blood CD3+, CD4+ and CD8+ T lymphocytes. Following in vitro stimulation with PHA and IL2, the expression of MUC1 was upregulated in more than 90% of these cells. MUC1 expression was also detected in 90% of LPS activated monocyte-derived dendritic cells (Mo-DCs) but was present in less than 20% of immature Mo-DCs. Both activated T lymphocytes and mature Mo-DCs demonstrated phosphorylation of tyrosine residues of the MUC1 cytoplasmic tail indicating MUC1 serves a role in signal transduction in immune cells.

The expression of MUC1 in activated T cells and APCs, brings into question the use of MUC1 as an antigen in cancer vaccines.

Keyword Cellular immunity
Ovaries -- Cancer -- Immunological aspects
Breast -- Cancer

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
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Created: Tue, 06 Dec 2011, 09:56:46 EST by Bekti Mulatiningsih on behalf of The University of Queensland Library