Journal Article•
Tolerance and immunity to MUC1 in a human MUC1 transgenic murine model
TL;DR: Data suggest that endogenous expression of MUC1 protein by M UC1 transgenic mice induces T-cell tolerance to stimulation by MUC2, and will facilitate the investigation of anti-MUC1 immunotherapy formulations.
Abstract: The human epithelial mucin, MUC1, is a large transmembrane glycoprotein that is expressed on most simple epithelia. It is overexpressed and aberrantly glycosylated on many human epithelial tumors, including more than 90% of human breast cancers. MUC1 is of interest as an immunotherapy target because patients with breast, ovarian, and pancreatic cancers have T lymphocytes in their tumor-draining lymph nodes that can be induced to recognize and lyse MUC1-expressing tumor cells. We have produced a transgenic mouse model that expresses the human MUC1 molecule on an inbred C57Bl/6 background to investigate the effect of endogenous expression of MUC1 on the ability of mice to generate antitumor immunity to MUC1-expressing tumors. Transgenic mice expressed the human transgene in a pattern and level consistent with that observed in humans. Transgenic mice were tolerant to stimulation by MUC1 as evidenced by the ability of MUC1-expressing tumor cells to grow in these mice, whereas MUC1-expressing cells were eliminated from wild-type mice. Moreover, transgenic mice immunized with MUC1 peptides failed to exhibit immunoglobulin class switching to the IgG subtypes. These data suggest that endogenous expression of MUC1 protein by MUC1 transgenic mice induces T-cell tolerance to stimulation by MUC1. The transgenic mice will provide a useful model to investigate the mechanisms that regulate immunological tolerance to tumor antigens and will facilitate the investigation of anti-MUC1 immunotherapy formulations.
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TL;DR: Recent discoveries that suggest that MUC1 may be a multifunctional protein, located on the surfaces of cells as a sensor of the environment, poised to signal to the interior when things go awry are highlighted.
Abstract: MUC1 is a large, heavily glycosylated mucin expressed on the apical surfaces of most simple, secretory epithelia including the mammary gland, gastrointestinal, respiratory, urinary and reproductive tracts. Although MUC1 was thought to be an epithelial-specific protein, it is now known to be expressed on a variety of hematopoietic cells as well. Mucins function in protection and lubrication of epithelial surfaces. Transmembrane mucins, which contain cytoplasmic tail domains, appear to have additional functions through their abilities to interact with many proteins involved in signal transduction and cell adhesion. The goal of this review is to highlight recent discoveries that suggest that MUC1 may be a multifunctional protein, located on the surfaces of cells as a sensor of the environment, poised to signal to the interior when things go awry.
550 citations
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TL;DR: The MUC1 membrane mucin was first identified as the molecule recognised by mouse monoclonal antibodies directed to epithelial cells, and the cancers which develop from them, and its role in the immune response and in other interactions with the effector cells of the immune system is of particular interest.
466 citations
TL;DR: The minimum requirements to consistently induce CTLs and ADCC-mediating antibodies specific for the tumor form of MUC1 are identified resulting in a therapeutic response in a mouse model of mammary cancer.
Abstract: The mucin MUC1 is typically aberrantly glycosylated by epithelial cancer cells manifested by truncated O-linked saccharides. The resultant glycopeptide epitopes can bind cell surface major histocompatibility complex (MHC) molecules and are susceptible to recognition by cytotoxic T lymphocytes (CTLs), whereas aberrantly glycosylated MUC1 protein on the tumor cell surface can be bound by antibodies to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). Efforts to elicit CTLs and IgG antibodies against cancer-expressed MUC1 have not been successful when nonglycosylated MUC1 sequences were used for vaccination, probably due to conformational dissimilarities. Immunizations with densely glycosylated MUC1 peptides have also been ineffective due to impaired susceptibility to antigen processing. Given the challenges to immuno-target tumor-associated MUC1, we have identified the minimum requirements to consistently induce CTLs and ADCC-mediating antibodies specific for the tumor form of MUC1 resulting in a therapeutic response in a mouse model of mammary cancer. The vaccine is composed of the immunoadjuvant Pam3CysSK4, a peptide Thelper epitope and an aberrantly glycosylated MUC1 peptide. Covalent linkage of the three components was essential for maximum efficacy. The vaccine produced CTLs, which recognized both glycosylated and nonglycosylated peptides, whereas a similar nonglycosylated vaccine gave CTLs which recognized only nonglycosylated peptide. Antibodies elicited by the glycosylated tripartite vaccine were significantly more lytic compared with the unglycosylated control. As a result, immunization with the glycosylated tripartite vaccine was superior in tumor prevention. Besides its own aptness as a clinical target, these studies of MUC1 are likely predictive of a covalent linking strategy applicable to many additional tumor-associated antigens.
270 citations
TL;DR: Chemoenzymatic synthesis of extended MUC1 TR glycopeptides with cancer-associated O-glycosylation using a panel of recombinant human glycosyltransferases is developed and a MAb with similar specificity as the elicited immune response was generated and shown to have the same remarkable cancer specificity.
Abstract: The MUC1 mucin represents a prime target antigen for cancer immunotherapy because it is abundantly expressed and aberrantly glycosylated in carcinomas. Attempts to generate strong humoral immunity to MUC1 by immunization with peptides have generally failed partly because of tolerance. In this study, we have developed chemoenzymatic synthesis of extended MUC1 TR glycopeptides with cancer-associated O-glycosylation using a panel of recombinant human glycosyltransferases. MUC1 glycopeptides with different densities of Tn and STn glycoforms conjugated to KLH were used as immunogens to evaluate an optimal vaccine design. Glycopeptides with complete 0-glycan occupancy (five sites per repeat) elicited the strongest antibody response reacting with MUC1 expressed in breast cancer cell lines in both Balb/c and MUC1.Tg mice. The elicited humoral immune response showed remarkable specificity for cancer cells suggesting that the glycopeptide design holds promise as a cancer vaccine. The elicited immune responses were directed to combined glycopeptide epitopes, and both peptide sequence and carbohydrate structures were important for the antigen. A MAb (5E5) with similar specificity as the elicited immune response was generated and shown to have the same remarkable cancer specificity. This antibody may hold promise in diagnostic and immuno-preventive measures.
255 citations
Cites background from "Tolerance and immunity to MUC1 in a..."
...…generally been ineffective in inducing humoral responses to the cancer-associated MUC1, when the mucin is expressed as a self-antigen, presumably because of tolerance (Goydos et al., 1996; Karanikas et al., 1997; Rowse et al., 1998; Adluri et al., 1999; Acres et al., 2000; Soares et al., 2001)....
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...These strategies have generally failed to produce effective immune responses to MUC1 expressed by cancer cells in hosts where the mucin is expressed as a self-antigen (Goydos et al., 1996; Karanikas et al., 1997; Rowse et al., 1998; Adluri et al., 1999; Acres et al., 2000; Gilewski et al., 2000; von Mensdorff-Pouilly et al., 2000a; Soares et al., 2001)....
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...MUC1 TR peptide vaccines have generally been ineffective in inducing humoral responses to the cancer-associated MUC1, when the mucin is expressed as a self-antigen, presumably because of tolerance (Goydos et al., 1996; Karanikas et al., 1997; Rowse et al., 1998; Adluri et al., 1999; Acres et al., 2000; Soares et al., 2001)....
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...…immune responses to MUC1 expressed by cancer cells in hosts where the mucin is expressed as a self-antigen (Goydos et al., 1996; Karanikas et al., 1997; Rowse et al., 1998; Adluri et al., 1999; Acres et al., 2000; Gilewski et al., 2000; von Mensdorff-Pouilly et al., 2000a; Soares et al., 2001)....
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TL;DR: It is demonstrated that unresponsiveness to the M UC1 tumor-associated antigen is reversible by immunization with heterokaryons of dendritic cells and MUC1-positive carcinoma cells.
Abstract: Immunological unresponsiveness established by the elimination or anergy of self-reactive lymphocyte clones is of importance to immunization against tumor-associated antigens. In this study, we have investigated induction of immunity against the human MUC1 carcinoma-associated antigen in MUC1 transgenic mice unresponsive to MUC1 antigen. Immunization of adult MUC1 transgenic mice with irradiated MUC1-positive tumor cells was unsuccessful in reversing unresponsiveness to MUC1. By contrast, fusions of dendritic cells with MUC1-positive tumor cells induced cellular and humoral immunity against MUC1. Immunization with the dendritic cell fusions that express MUC1 resulted in the rejection of established metastases and no apparent autoimmunity against normal tissues. These findings demonstrate that unresponsiveness to the MUC1 tumor-associated antigen is reversible by immunization with heterokaryons of dendritic cells and MUC1-positive carcinoma cells.
248 citations
References
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TL;DR: B-cell tolerance in transgenic mice using genes for IgM anti-H–2k MHC class I antibody is studied and it is suggested that very large numbers of autospecific B cells can be controlled by clonal deletion.
Abstract: B lymphocytes can be rendered specifically unresponsive to antigen by experimental manipulation in vivo and in vitro1–6, but it remains unclear whether or not natural tolerance involves B-cell tolerance because B cells are controlled by T lymphocytes, and in their absence respond poorly to antigen (reviewed in ref. 7). In addition, autoantibody-producing cells can be found in normal mice and their formation is enhanced by B-cell mitogens such as lipopolysaccharides8–12. We have studied B-cell tolerance in transgenic mice using genes for IgM anti-H–2k MHC class I antibody. In H–2d transgenic mice about 25–50% of the splenic B cells bear membrane immunoglobulin of this specificity, and abundant serum IgM encoded by the transgenes is produced. In contrast, H–2k x H–2d (H–2-d/k) transgenic mice lack B cells bearing the anti-H–2k idiotype and contain no detectable serum anti-H–2k antibody, suggesting that very large numbers of autospecific B cells can be controlled by clonal deletion.
1,010 citations
TL;DR: The full sequence for PEM, as deduced from cDNA sequences, is reported, with length variations in the tandem repeat result in PEM being an expressed variable number tandem repeat locus.
1,007 citations
"Tolerance and immunity to MUC1 in a..." refers background in this paper
...Tumor length (1) and width (2r) were determined at the indicated days postinjection....
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TL;DR: Functional studies are in progress both in vitro using cDNAs and cell lines and in vivo utilizing mutant mice in which a particular mucin gene has been inactivated or overexpressed to help determine whether the functions of mucins are restricted to protection and lubrication, or if they are involved in the adhesion of tumor cells to other cells or tissue components or in modulation of the immune system.
Abstract: The last seven years have been exciting in the world of mucin biology. Molecular analyses of mucin genes and deduced protein structures have provided insight into structural features of mucins and tools with which to examine expression, secretion, and glycosylation, thereby enabling a better understanding of the role of mucins in normal physiological processes and in disease. Functional studies are in progress both in vitro using cDNAs and cell lines and in vivo utilizing mutant mice in which a particular mucin gene has been inactivated or overexpressed. These studies should help determine whether the functions of mucins are restricted to protection and lubrication, or if they are involved in the adhesion of tumor cells to other cells or tissue components or in modulation of the immune system.
970 citations
TL;DR: It is shown here that all three antibodies react with a synthetic peptide with an amino acid sequence corresponding to that predicted by the tandem repeat, allowing a directed approach to the development of tumor-specific antibodies using synthetic peptides as immunogens.
598 citations
TL;DR: Recent discoveries that suggest that MUC1 may be a multifunctional protein, located on the surfaces of cells as a sensor of the environment, poised to signal to the interior when things go awry are highlighted.
Abstract: MUC1 is a large, heavily glycosylated mucin expressed on the apical surfaces of most simple, secretory epithelia including the mammary gland, gastrointestinal, respiratory, urinary and reproductive tracts. Although MUC1 was thought to be an epithelial-specific protein, it is now known to be expressed on a variety of hematopoietic cells as well. Mucins function in protection and lubrication of epithelial surfaces. Transmembrane mucins, which contain cytoplasmic tail domains, appear to have additional functions through their abilities to interact with many proteins involved in signal transduction and cell adhesion. The goal of this review is to highlight recent discoveries that suggest that MUC1 may be a multifunctional protein, located on the surfaces of cells as a sensor of the environment, poised to signal to the interior when things go awry.
550 citations