Preferential expression of novel MUC1 tumor antigen isoforms in human epithelial tumors and their tumor-potentiating function

The human MUC1 gene expresses at least 2 type 1 membrane proteins: MUC1/REP, a polymorphic high m.w. MUC1 glycoprotein often highly expressed in breast cancer tissues and containing a variable number of tandem 20 amino acid repeat units, and the MUC1/Y protein, which lacks this repeat array and, therefore, is not polymorphic. Despite their documented importance in signal transduction processes, the relative expression of the 2 isoforms in epithelial tumors is unknown. Using antibody reagents which recognize different MUC1 domains, the expression of these isoforms in malignant epithelial cells has been evaluated. A comparison of the amounts of the 2 isoforms revealed preferential expression of the novel MUC1/Y protein in breast cancer tissue samples. Furthermore, although the MUC1/REP protein is almost undetectable in HeLa cervical adenocarcinoma epithelial cells, the MUC1/Y isoform is extensively expressed in these cells. The presence of the MUC1/Y sequence as well as that of an additional tandem-repeat-array-lacking isoform, designated MUC1/X, were demonstrated by reverse transcriptase PCR amplification of RNA extracted from HeLa and ovarian carcinoma cells. It has been shown previously that the MUC1 cytoplasmic domain interacts with the SH2 domain containing GRB2 protein, which transduces signals to ras, a protein which in its activated form can lead to cell transformation. We present here data demonstrating that MUC1/Y isoform expression increases the tumorigenic potential of DA3 mouse mammary epithelial cells; in contrast, potentiation of tumorigenicity is not observed with MUC1/REP expression. Our studies thus demonstrate that expression of the MUC1 gene in epithelial tumors can give rise to substantial levels of MUC1 proteins devoid of the tandem repeat array, which are generated by alternative splicing mechanisms.

Cytotoxic T lymphocytes derived from bone marrow mononuclear cells of multiple myeloma patients recognize an underglycosylated form of MUC1 mucin

MUC1 is a highly immunogenic epithelial mucin and serves as a tumor-associated antigen in breast, pancreatic and ovarian carcinomas. We previously reported the expression of MUC1 on myeloma cells and the establishment of an HLA-unrestricted cytotoxic T lymphocyte (CTL) line TN that recognized MUC1 from peripheral blood mononuclear cells in a multiple myeloma patient. In this study, we attempted to induce such CTL from six other multiple myeloma patients consecutively in order to show that the induction of the CTL line TN had not resulted from some idiosyncrasy of the first patient. Bone marrow mononuclear cells were used to induce CTL, because they contain myeloma cells that might stimulate the autologous lymphocytes. Bulk CTL lines were induced from two out of six patients. The CTL line TS was CD8+ cell dominant and KY was CD4+ cell dominant. Both CTL lines lysed MUC1+ myeloma and breast carcinoma cell lines. The cytotoxicity of the CTL lines was inhibited by anti-CD3, anti-alpha beta TCR and anti-MUC1 mAb. It was also inhibited by a MUC1 transfectant, but not by a mock transfectant in cold target inhibition assays. MUC1 was transfected into a human colonic carcinoma cell line. The reactivity of anti-MUC1 core protein mAb and the cytotoxicity of the CTL against the transfectant was enhanced by the treatment of the cells with an O-glycosylation inhibitor. Thus it is generally accepted that the HLA-unrestricted CTL which directly recognize the underglycosylated from of MUC1 using their TCR could be induced from a certain proportion (approximately 30%) of untreated multiple myeloma patients.

Estrogenic effects of nonylphenol on pS2, ER and MUC1 gene expression in human breast cancer cells-MCF-7

Many chemicals have recently been discovered to have estrogenic activity, including the surfactant intermediate nonylphenol (NP). It has been well documented that estrogen is a facilitator of human breast cancer development under certain conditions, and environmental estrogens such as NP are currently under intense investigation. Using the expression of pS2 (a trefoil peptide expressed in breast cancer cells), MUC1 (a member of the mucin family) and ER (the human estrogen receptor) genes as estrogen-responsive reporter genes, the effects of estradiol and NP on human breast cancer cells-MCF-7 were studied. In the time course study, the mRNA expressions were detected after NP (10 microM) or estradiol (E2, 0.1 microM) treatments using the RT-PCR technique. The results indicated: (1) NP and E2 induced pS2 mRNA expression after a 2-h exposure and (2) NP induction produced the highest level of MUC1 mRNA after 2 h, which was reduced to only 42% of control at 48 h. E2 treatment resulted in a gradual increase in MUC1 expression over the course of the exposure. The highest level of MUC1 mRNA was at 48 h. This indicates that NP may stimulate MUC1 expression by a different mechanism than E2. (3) NP affected ER expression in the same manner as MUC1. In contrast, E2 stimulated ER expression in a similar manner as pS2; the highest level was at 2 h and expression remained elevated through the 48-h point. NP is an estrogenic compound that alters pS2, MUC1 and ER gene expression in MCF-7 cells. NP may affect MUC1 expression through a different mechanism than E2. The link between aberrant MUC1, PS2 and ER expression and the development of breast cancer also needs to be elucidated through further investigation.

Effect of multiple, repeated doses of radioimmunotherapy on target antigen expression (breast MUC-1 mucin) in breast carcinomas

The effect of radioimmunotherapy (RIT) on target antigen expression was studied in breast carcinomas transplanted in immunodeficient mice. In nine separate experiments, a single dose of 1500 microCi of 131I-labeled monoclonal antibody (MAb) Mc5 was given to groups of mice carrying well-established, vascularized, transplantable breast tumors (MX-1). Mc5 recognizes an epitope on the tandem repeat of the breast epithelial MUC-1 mucin. This dose suppressed tumor growth for at least 20 days, after which the tumors began to regrow. At various times thereafter, tumors were removed and analyzed for target antigen expression by flow cytometry and immunohistochemistry. In no case was there any significant decrease in antigen content/cell in the tumors of treated mice compared to tumors in control untreated mice. Similar results were obtained with four other breast carcinomas (MCF-7, MDA-MB-331, MDA-MB-435, and MX-2A). To assess the effect of repeated RIT doses on target antigen expression, groups of mice with MX-1 tumors were given 2, 3, and 4 consecutive doses of 1200 microCi of 131I-labeled Mc5. One mouse each at 2, 3, and 4 doses (3 of 18) was cured of its tumor. Control mice were sacrificed after 50 days due to the excessive size of their tumors. Tumors from four mice from each group (2, 3, and 4 doses), after they began to regrow, were excised and analyzed for mucin content and compared to tumors from untreated mice with similar-size tumors transplanted at later dates. In none of the treated groups was there any decrease in mucin content. These results demonstrate that RIT with an anti-breast mucin MAb does not result in the appearance of antigen-negative tumor cells, thus indicating that repeated fractionated doses, which will most likely be necessary for an eventual cure of breast cancer with MAb therapy, are possible.

Differential glycosylation of MUC1 in tumors and transfected epithelial and lymphoblastoid cell lines

The membrane-bound mucin-like protein MUC1 with a specified number of tandem repeats has been expressed by transfection of the cDNAs in both the epithelial cell lines MDCK and LLC-PK1, and human lymphoblastoid cell lines T2 and C1R. The structure and glycosylation states of the MUC1 in these four lines were compared with that of the endogenous MUC1 found in the human pancreatic (HPAF) and breast (BT-20) tumor cell lines using flow cytometry and Western blot analysis with anti-MUC1 antibodies, which are either sensitive or insensitive to the glycosylation state of the tandem repeat, and pretreatment of cells with phenyl-alpha-galactosaminide, an inhibitor of mucin sialylation. A similar analysis of MUC1 expression in transfected normal and O-glycosylation defective CHO cells reveals that the addition of galactose to the core oligosaccharide structure is apparently responsible for the anomalous difference in M(r), between the mature and propeptide forms of the MUC1. Both the tumor cells and the transfected lymphoblastoid cells consistently express significant steady state levels of both the heavily glycosylated mature forms and the poorly glycosylated propeptide forms of the MUC1, whereas MUC1 is found predominantly as the mature extensively glycosylated species in the transfected epithelial cells. Immunofluoresence microscopy of cross sections of the polarized epithelial cells grown on culture filter inserts reveals that the MUC1 is clearly present at the apical surface of the cells, consistent with its expression in normal tissues. Thus, the successful expression of the MUC1 by transfection of either lymphoblastoid cells or epithelial cells yields model systems both for studying the natural structure/function relationships of the protein domains within the MUC1 molecule and for further elucidating the previously reported MHC-independent T-cell recognition of the MUC1.

MUC1 gene polymorphism and gastric cancer--an epidemiological study

Gastric carcinoma is a major cause of cancer death worldwide and, like most human cancers, probably develops after environmental insults acting on normal individuals and/or individuals with increased genetic susceptibility. Mucins are attractive molecules to study the relationship between genetics and environment because they play an important role in the protection of gastric mucosa against environmental insults and exhibit a highly polymorphic genetic variation. We performed a case-control study using Southern blot analysis to evaluate the MUC1 gene polymorphism in a series of blood donors (n = 324) and in patients with gastric carcinoma (n = 159). We found that the distribution of MUC1 alleles is significantly different in the two populations and that small MUC1 alleles and small MUC1 genotypes are significantly more frequent in patients with gastric carcinoma than in controls. Individuals with small MUC1 genotypes are at increased risk for gastric carcinoma development.

Effects of steroid-free fetal serum and steroid supplementation on MUC1 gene expression in human breast cancer cell line MCF7

MUC1 is a gene expressed by many normal epithelial tissues and aberrantly expressed by carcinomas. Studies regarding the expression of MUC1 in endometrial tissues and the constitution of its promoter region suggest a possible role for hormonal regulation of this gene. The aim of the present work was to evaluate the regulation of MUC 1 expression by 17 beta-estradiol (E2), progesterone (Pg) and by steroid-free fetal calf serum (FCS) in the hormone-sensitive cell line MCF7. MUC1 mRNA proved to be detectable by means of Northern-blot analysis in MCF7 cells, and its levels were strongly increased in cells grown with 10% steroid-free FCS. By contrast, the steady-state MUC1 mRNA levels of steroid-supplemented cells did not change compared to those of unsupplemented cells (controls). In conclusion, MUC1 expression is regulated by substances present in the steroid-stripped FCS (growth factors, e.g. Insulin-like Growth Factor). The lack of any observed MUC1 modulation by steroids could be due to: a) a low FCS concentration preventing the manifestation (permissive action) of possible gene regulation; b) an immediate stimulatory effect occuring in the first phases of the treatment, which could subsequently be lost.

Phenotypic heterogeneity of nodular hidradenoma. Immunohistochemical analysis with emphasis on cytokeratin expression

We studied the immunohistochemical phenotype in 13 cases of the nodular hidradenoma (NH), with special emphasis on the expression of different types of keratins (cytokeratins, 7, 10, 6/18, 8/18, and 10/17/18 and their distribution in normal sweat glands. Variable reactions with keratins, alpha-smooth muscle actin, and epithelial membrane antigen (EMA) were found, as these markers were present in different cellular components of the tumors. The most constant finding was almost complete absence of cytokeratins (all but keratin 10/17/18, which was positive in two of 13 cases) in clear cells, which yet were positive for EMA. The tumors expressed mostly cytokeratin 6/18, 7, 8/18, and 10/17/18, which were found in 11, 13, 11, and 12 cases, respectively. The cellular distribution and quantity of stained cells differed, as keratins 6/18, 8/18, and 7 produced the most abundant staining and were predominantly localized in small squamoid cells and the cells lining the tubular and cystic spaces. Cytokeratin 10/17/18 was expressed in smaller or larger clusters of squamoid cells and rarely in clear cells. Cytokeratins 10, 19, and 20 were found sporadically in single cells or small cellular clusters. alpha-Smooth muscle actin was expressed in four cases, whereas we did not find reactivity of S-100 protein. Comparing these results with the pattern of keratin distribution and antigenic reactivity in eccrine sweat glands, we conclude that NH presents cellular heterogeneity of its elements and differentiation toward different parts of the sweat gland.

Spatial and temporal analyses of integrin and Muc-1 expression in porcine uterine epithelium and trophectoderm in vivo

The spatial and temporal expressions of Muc-1, selected integrin subunits, and extracellular matrix components in porcine uterine epithelium from estrous (Days 0, 4, 8, 10-15) and early pregnant (Days 10-15 of pregnancy) gilts and from steroid-treated ovariectomized gilts were analyzed using indirect immunofluorescence analyses on cryosectioned tissues to identify potential components of uterine receptivity. Integrin subunit and extracellular matrix expressions were also examined in Day 11-15 conceptuses. Intense Muc-1 staining was detected on apical uterine epithelium on Day 0 but was absent by Day 10 in both cyclic and pregnant gilts. The result of estrogen treatment (E2; 100 micrograms/day for 10 days) was similar to that of the corn oil vehicle control, while treatment with progesterone (P4; 200 mg/day for 10 days) or E2 + P4 decreased Muc-1 staining in ovariectomized gilts. Immunostaining performed with antibodies directed against integrin subunits (alpha 1, alpha 3, alpha 4, alpha 5, alpha v, beta 1, and beta 3) in uterine epithelium revealed low (integrin subunits alpha 1 alpha 3), high (integrin subunits alpha v and beta 3), or modulated (integrin subunits alpha 4, alpha 5, and beta 1) expression, with the lowest expression on Day 0 and maximum expression by Days 10-15. Additionally, no differences due to pregnancy status were detected in staining of uterine epithelium on Days 10-15. Uterine epithelium from steroid-treated ovariectomized gilts had low expression of alpha 4, alpha 5, and beta 1 subunits in the presence of E2 that increased in response to P4 and E2 + P4 treatments. The expression of integrin subunits alpha 3, alpha v and beta 3 was not affected by sex steroids. Trophectoderm also expressed alpha 1, alpha 4, alpha 5, alpha v, beta 1, and beta 3, integrin subunits. Extracellular matrix constituents (fibronectin, vitronectin, laminin, and collagen type IV) were also examined. Fibronectin and vitronectin were present on trophectoderm, but only vitronectin was detected on uterine epithelium. The alpha 4, alpha 5, alpha v, beta 1, and beta 3 integrin subunits, vitronectin, and fibronectin were detected at sites of attachment between uterine epithelial cells and trophectoderm on Days 12-15 of pregnancy. These studies indicate that down-regulation of Muc-1 coincides with the transition of the prereceptive uterus to the receptive uterus. Additionally, the expression of alpha 4, alpha 5, alpha v, beta 1, and beta 3 integrin subunits along with the extracellular matrix components of fibronectin and vitronectin correlates with the time of implantation in swine.

Differential expression of MUC1 on transfected cell lines influences its recognition by MUC1 specific T cells

In adenocarcinomas of the breast and pancreas, underglycosylation of the glycoprotein MUC1, also expressed by normal breast and pancreatic ductal epithelial cells, results in new protein epitopes to which the immune system mounts a cytotoxic T cell response. This cytotoxic immune response is directed primarily against epitopes on the tandem repeat domain of MUC1, and is unconventional in that it is major histocompatibility complex (MHC)-unrestricted. It is therefore necessary to investigate the molecular basis of this immune response in order to enhance and optimize it for immune therapy purposes. In the present study, we characterize new MUC1 transfected human lymphoblastoid cell lines C1R and T2, and a pig kidney epithelial line LLC-PKI, that express MUC1 with either two repeats (MUC1-2R) or 22 repeats (MUC1-22R), and use them as stimulators and targets for cytotoxic T cells (CTL) in vitro. We show that MUC1-2R is processed and glycosylated similarly to MUC1-22R. In contrast to MUC1-22R, MUC1-2R is not recognized by CTL on T2 and C1R cells known for no or low MHC class I expression. It is however recognized when expressed at high density on xenogeneic LLC-PKI cells. We propose that in MHC-unrestricted recognition, a large number of MUC1 epitopes is necessary to effectively engage the T cell receptor, and that in the presence of a low number of epitopes, engagement of the CD8 co-receptor by MHC class I molecules may be required for completing the signal through the T cell receptor.

Proline-rich tandem repeats of antibody complementarity-determining regions bind and neutralize human immunodeficiency virus type 1 particles

The proline-rich tandem repeat domain of human mucin MUC1 forms an extended structure containing large repeating loops that are crested by a turn. We show that the repeating-loop structure of MUC1 can be replaced by an antibody complementarity-determining region loop of a human immunodeficiency virus type 1 (HIV-1)-specific neutralizing antibody to create a chimeric, multivalent, mucin-like, anti-HIV-1 compound. We used 8 residues of an antibody molecule to replace 8 of 20 residues of the MUC1 tandem-repeat sequence. The antiviral peptide discussed here contains three copies of a 20-residue tandem repeat, (IYYDYEEDPAPGSTAPPAHG)3, for a total of 60 residues. We demonstrate that the mucin-antibody chimera retains the binding specificity of the parent antibody (monoclonal antibody F58), GPGR of the HIV-1 gp120 V3 neutralizing epitope, and the ability to neutralize virus particles. In inhibition enzyme-linked immunosorbent assay, the mucin-antibody chimeric peptide could inhibit 71 to 84% of binding to a V3 loop peptide by monoclonal antibodies known to be specific for GPGR in the V3 loop. The mucin-antibody chimeric peptide could also inhibit monoclonal antibody binding to native gp120 captured from virus particles. In addition, the chimeric peptide neutralized the homologous HIV-IIIB virus in a standard neutralization assay. The methods of antiviral peptide design and construction presented here are general and theoretically limited only by the size of the antibody repertoire. This approach could be used to synthesize peptides for a variety of therapeutic applications.

Cloning and expression of cDNA for O-acetylation of GD3 ganglioside

O-acetylated sialic acids of glycoproteins and gangliosides show cell type-specific and developmentally regulated expression in various systems and sometimes reappear as oncofetal antigens. O-acetylation of sialic acids may influence cell-cell interactions mediated by the sialic acid-binding lectins. Here we describe the molecular cloning and sequencing of a gene that produces O-acetyl disialoganglioside (O-acetyl GD3). Expression analysis showed that this gene product participates the O-acetylation of GD3 ganglioside sialic acid. The deduced amino acid sequence of the product was found to be similar to the milk fat globule membrane glycoprotein.

Muc1, a mucin-like protein that is regulated by Mss10, is critical for pseudohyphal differentiation in yeast

Pseudohyphal differentiation in Saccharomyces cerevisiae was first described as a response of diploid cells to nitrogen limitation. Here we report that haploid and diploid starch-degrading S. cerevisiae strains were able to switch from a yeast form to a filamentous pseudohyphal form in response to carbon limitation in the presence of an ample supply of nitrogen. Two genes, MSS10 and MUC1, were cloned and shown to be involved in pseudohyphal differentiation and invasive growth. The deletion of MSS10 resulted in extremely reduced amounts of pseudohyphal differentiation and invasive growth, whereas the deletion of MUC1 abolished pseudohyphal differentiation and invasive growth completely. Mss10 appears to be a transcriptional activator that responds to nutrient limitation and coregulates the expression of MUC1 and the STA1-3 glucoamylase genes, which are involved in starch degradation. MUC1 encodes a 1367-amino acid protein, containing several serine/threonine-rich repeats. Muc1 is a putative integral membrane-bound protein, similar to mammalian mucin-like membrane proteins that have been implicated to play a role in the ability of cancer cells to invade other tissues.

Expression of MUC1 mucin gene by hamster tracheal surface epithelial cells in primary culture

Primary hamster tracheal surface epithelial (HTSE) cells carry mucin-like glycoproteins on the apical surface which are releasable by neutrophil elastase. In some cancer cells, mucins are localized on the cell surface and have been shown to be encoded by the MUC1 mucin gene. The objectives of the present experiments were: (I) to determine if HTSE cells express MUC1 mucin gene; (2) if they do, to isolate and characterize the hamster MUC1 complementary DNA (cDNA); and (3) to examine the pattern of MUC1 mRNA expression at different stages of culture. Reverse transcriptase-polymerase chain reaction amplification of HTSE cell RNAs using degenerate primers based on homologous sequences between the human and mouse MUC1 genes revealed the presence of a cDNA (0.5 kb) which has an 88% similarity in sequence with the mouse MUC1 cDNA. Using this 0.5 kb cDNA as a probe, an HTSE cell cDNA library was screened to isolate a hamster MUC1 cDNA clone. Sequence analysis of the cDNA revealed that it encodes an integral membrane protein of 676 amino acids which consists of (1) an N-terminal signal sequence, (2) the tandem repeat domain encoding 12 repeats of 20 amino acids, and (3) the C-terminal region consisting of degenerate tandem repeats and a unique sequence containing both the transmembrane and cytoplasmic domains. The presence of seven tyrosine residues in the cytoplasmic domain suggests a potential role as a receptor. Finally, expression of MUC1 mucin gene in HTSE cells appears to be associated with differentiation of secretory cells.

Potential for H-DNA in the human MUC1 mucin gene promoter

Similar imperfect purine/pyrimidine mirror repeat (PMR) elements have previously been identified upstream of the human MUC1 mucin and CFTR genes. These elements confer S1 nuclease sensitivity on isolated plasmid DNA at low pH. We now present a detailed characterization of the non-B DNA structure responsible for S1 nuclease sensitivity upstream of the MUC1 gene. A approximately 90-base pair (bp) DNA fragment containing a 32-bp PMR element termed M-PMR3 was subcloned into a recombinant vector. This fragment conferred S1 nuclease sensitivity on the resulting supercoiled plasmid. High resolution mapping of sites reactive to S1 and P1 nucleases demonstrates that cleavage occurs within the M-PMR3 element. High resolution mapping with chemical agents selective for non-B DNA provides evidence that M-PMR3 adopts an H-DNA structure (intramolecular triple helix) in the less common H-y5 isomer at low pH. This result is observed in the presence or absence of Mg2+. Mutation of the native M-PMR3 element to create perfect homopurine/homopyrimidine mirror symmetry alters the preferred folding to the more common H-y3 triplex DNA isomer. These results demonstrate that imperfections in mirror symmetry can alter the relative stabilities of different H-DNA isomers.

Two GC boxes (Sp1 sites) are involved in regulation of the activity of the epithelium-specific MUC1 promoter

In this report, we have analyzed the function of two Sp1 sites present in the epithelium-specific MUC1 promoter. Using promoter-reporter gene (CAT) constructs, we found that mutagenesis of either of the Sp1 binding motifs at -576/-568 and -99/-90, reduced transcription in MUC1-expressing epithelial cell lines. However, abolition of the binding site at -99/-91 by mutagenesis also resulted in increased transcriptional activity in non-epithelial cell lines, suggesting involvement of the site in tissue-specific expression. In vitro binding assays revealed a novel binding motif at -101/-89 (AGGGGGCGGGGTT), which overlaps but differs from the Sp1 consensus motif by having an adenine residue in the 5'-flanking sequence. The 5'-flanking sequence appeared to be important for binding of an Sp1-unrelated factor (SpA) but not for binding of Sp1. Site-directed mutagenesis of the motif into a site able to bind Sp1, but unable to bind SpA, resulted in an increased level of transcription of the CAT reporter gene in all cell lines tested, suggesting a repressive effect of the novel factor on transcription. The ratio between the Sp1 and SpA binding activity in nuclear extracts correlated with both promoter activity and the levels of endogenous transcription in different breast cancer cell lines. Our results are consistent with the idea that the relative activities of the two factors may be involved in the up-regulation of expression of the MUC1 gene seen in breast and other carcinomas.

Pattern of mucin gene expression in normal and neoplastic lung tissues

This work evaluates the expression in lung cancer of the most well characterized mucin genes (MUC1, MUC2, MUC3) and of the recently described MUC4 in lung tissues, to check a correlation between the expression of any particular gene and this tumor. Hybridization with synthetic oligonucleotides obtained from a part of the sequences of MUC1, MUC2, MUC3 and MUC4, was performed on blotted RNA from 18 lung cancer tissue specimens and from 10 normal tissues samples taken, when possible, from the normal lung counterpart. By means of Northern blot analysis MUC1 revealed to be the most expressed mucin gene in lung cancer, followed by MUC4; by contrast, the expression of MUC2 and MUC3 was almost undetectable in all cancer specimens. The intensity of expression of MUC1 and MUC4 was always superior in cancer tissue than in the normal counterpart. As expected, the highest reactivity for MUC1 and MUC4 expression was observed mainly in the adenocarcinoma histotype which is mucin secreting. These findings represent a contribution to the study of mucin gene pattern in lung cancer, and, in particular, indicate that MUC4, in association with the MUC1 gene, seems to be strongly expressed in this neoplastic disease.

Expression of mucin carbohydrates and core proteins in carcinomas of the ampulla of Vater: their relationship to prognosis

We examined the expression of carbohydrate antigens which are associated with the earliest steps in mucin glycosylation (Tn and sialosyl-Tn) and the expression of the mucin core protein antigens associated with MUC1 gene product (DF3 antigen) as well as MUC2 gene product (intestinal-MRP antigen) in tissues from 38 patients with carcinoma of the ampulla of Vater, in order to determine whether these mucin antigens are available as tumor markers or not, and to evaluate whether their expression is correlated with the biological behavior of the carcinomas or not. DF3 antigen showed a relatively high expression rate (61%) in the carcinoma tissues, but was rarely expressed in the non-neoplastic epithelium around the carcinomas in the region of the ampulla of Vater. Tn and sialosyl-Tn antigens showed high expression rates in the carcinoma tissues (86% and 84% each), whereas they showed rare or no expression in the non-neoplastic epithelium around the carcinomas, except for highly restricted expression in the duodenal villous epithelium. The patients with positive DF3 expression in the carcinoma showed significantly poorer survival than those with negative DF3 expression (P < 0.05), whereas the patients with positive intestinal-MRP expression in the carcinoma showed significantly more favorable survival than those with negative intestinal-MRP expression (P < 0.05). The expression rate of DF3 antigen was significantly higher in the cases with deep invasion into the pancreas (89%) than in those with no or minimal invasion (52%) (P < 0.05). In contrast, the expression rate of intestinal-MRP antigen was significantly higher in the cases with no or minimal invasion into the pancreas (38%) than in those with deep invasion (0%) (P<0.05). In conclusion, the expression of DF3, To and sialosyl-Tn antigens is an effective histopathological indicator for carcinomas in the area of the ampulla of Vater, and the expression of DF3 and intestinal-MRP antigens is a useful indicator of the prognosis of the patients.

Expression of a glycoprotein of the carcinoembryonic antigen family in normal and neoplastic sebaceous glands. Limited role of carcinoembryonic antigen as a sweat gland marker

BACKGROUND

Carcinoembryonic antigen (CEA) is a well-known marker for sweat gland differentiation in adnexal neoplasms.

OBJECTIVE

The aim of this study was to examine the expression of glycoproteins of the CEA family, that is, CEA-180, nonspecific cross-reacting antigens (NCAs), and biliary glycoprotein (BGP), in sebaceous glands and in neoplasms with sebaceous differentiation.

METHODS

Normal adult and fetal skin, hyperplasias, hamartomas, and neoplasms with sebaceous or follicular differentiation were stained immunohistochemically with a panel of polyclonal and monoclonal antibodies highly specific for CEA-180, NCAs, and BGP. Double immunostaining was performed to correlate the CEA expression with that of epithelial membrane antigen (EMA), a glycoprotein consistently found in differentiating sebocytes.

RESULTS

Whereas sweat glands coexpressed CEA, NCAs, BGP, and EMA, sebaceous glands were exclusively labeled with the antibodies recognizing BGP or EMA. Staining of the sebaceous glands was restricted to mature sebocytes, sparing immature cells. At the ultrastructural level immunoreactivity for BGP and EMA was demonstrable in the golgi area, in small vesicles, and along the cell membranes. During fetal development BGP was not found until the sebaceous glands matured. The expression of BGP and EMA was highly conserved in reactive, hamartomatous, and neoplastic proliferations of adnexal structures with sebaceous differentiation.

CONCLUSION

The expression of BGP, a CEA glycoprotein, in differentiating sebocytes accounts for the reactivity of many anti-CEA antibodies with sebaceous glands and thus disqualifies the CEA family as a monospecific marker for sweat gland differentiation.

Regulation of MUC5 and MUC1 gene expression: correlation with airway mucous differentiation

The purpose of this paper was to obtain probes to study the structure and function of mucins in rat models of airway cell differentiation and disease. We report the isolation and characterization of the rat cDNA homologue of the human airway secretory mucin, MUC5. Furthermore, we demonstrate the coordinate regulation of the expression of MUC5 and MUC1 (a membrane-bound mucin) and mucous differentiation. The rat MUC5 was cloned by the RT-PCR using motifs conserved in the secretory mucins, MUC2 and MUC5. The rat cDNA revealed a high degree of sequence similarity to human MUC5 (73% at the amino acid level). Alignments with three other secretory mucins (human MUC5, human MUC2, rat MUC2), indicated a conservation of the cysteines and of the octapeptide motifs, but a lack of conservation of a short tandem repeat sequence that is found only in the human MUC5. Northern analysis of MUC1 and MUC5 indicated a specific tissue-restricted pattern of expression. Surprisingly, rat MUC5 exhibited a monodisperse signal, a characteristic that is unusual for most secretory mucins, including the human MUC5. Expression of MUC1 and MUC5 correlated with mucous differentiation. Both genes were expressed at undetectable or very low levels in undifferentiated cultures, but both mucins became strongly expressed during mucous differentiation. Furthermore, neither mucin gene was expressed in retinoid-deficient cultures that undergo squamous instead of mucous differentiation. These studies demonstrate that expression of MUC1 and MUC5 is coordinately regulated with airway mucous cell differentiation. These cDNAs should provide useful tools to study mucin synthesis during differentiation and disease.

Mucin (Muc-1) expression is differentially regulated in uterine luminal and glandular epithelia of the baboon (Papio anubis)

Changes in the organization and composition of apical cell surface glycoconjugates accompany the transition of luminal epithelial cells from the prereceptive state of the uterus in many species. In spite of the biological and clinical significance of this process, few molecular markers have arisen as useful predictors of uterine receptivity. Recent studies in mice demonstrate that the transmembrane mucin glycoprotein, Muc-1, is abundantly expressed at the apical surface of luminal epithelia under most conditions and is invariably reduced in receptive uteri. These and other observations have led to the suggestion that mucins serve an antiadhesive role and function to maintain a nonreceptive uterine state. A pan-species Muc-1 specific antibody recognizing a peptide motif conserved in the cytoplasmic domain of Muc-1 was used to examine the temporal and spatial expression of cell-associated Muc-1 in baboon uteri under a variety of conditions, including the pre- and perimplantation periods. Muc-1 expression was not driven by estrogen influences alone, but required progesterone action. In animals exposed to both steroids, Muc-1 was expressed at low moderate levels in epithelia of the basalis and functionalis regions. The highest expression of Muc-1 was detected in surface epithelium of the preimplantation phase, i.e., up to Day 8 (Day 0 = day of ovulation), or in ovariectomized animals receiving a steroid hormone regime that mimicked this phase (14 days of estrogen priming followed by 7 days of estrogen plus progesterone). Continued exposure to both hormones, i.e., as seen at Days 10-12 or in ovariectomized baboons given 14 days of estrogen plus progesterone treatment after estrogen priming, resulted in marked reduction of Muc-1 expression in the surface epithelium; however, staining patterns in the glandular epithelium were unchanged by this treatment. The expression of Muc-1 on the surface epithelium during the prereceptive phase was associated with the presence of both estrogen and progestin receptors in these epithelia. Muc-1 expression was reduced by neither antiestrogen treatment during the prereceptive stage nor antiprogestin treatment through to the receptive phase. Furthermore, persistent Muc-1 expression in the functionalis and basalis epithelium correlated with expression of progestin receptors. Thus, Muc-1 expression appeared to be progesterone-dependent rather than estrogen-dependent. It is concluded that Muc-1 expression in surface epithelium serves as a marker of the prereceptive phase in the baboon and that loss of Muc-1 from surface epithelium correlates with generation of a receptive uterine state.

A mechanism for inhibition of E-cadherin-mediated cell-cell adhesion by the membrane-associated mucin episialin/MUC1

Episialin (MUC1, PEM, EMA, CA15-3 antigen) is a sialylated, membrane-associated glycoprotein with an extended mucin-like ectodomain. This domain mainly consists of 30-90 homologous 20-amino acid repeats that are rich in O-glycosylation sites (serines and threonines). It is likely that this part forms a polyproline beta-turn helix. As a result, the ectodomain can protrude more than 200 nm above the cell surface, whereas most cell surface molecules do not exceed a length of 35 nm. Normally, episialin is present at the apical side of glandular epithelial cells. On carcinoma cells, however, it can be strongly overexpressed and it is often present over the entire cell surface. We have previously shown that episialin, if it is interspersed between adhesion molecules, nonspecifically reduces cell-cell and cell-extracellular matrix interactions in vitro and in vivo, presumably by steric hindrance caused by the extreme length and high density of the episialin molecules at the cell surface. To analyze the molecular mechanism for this anti-adhesion effect in more detail, we have now deleted an increasing number of repeats in the episialin cDNA and transfected the resulting mutants into murine L929 cells expressing the homophilic adhesion molecule E-cadherin. Here we show that the length of episialin is the dominant factor that determines the inhibition of E-cadherin-mediated cell-cell interactions. For the anti-adhesive effect mediated by the full length episialin, charge repulsion by negatively charged sialylated O-linked glycans is far less important.

Preoperative diagnosis of thyroid papillary carcinoma by reverse transcriptase polymerase chain reaction of the MUC1 gene

As thyroid nodules are common, it is imperative to recommend operation only to those with a high risk of malignancy. Fine-needle aspiration (FNA) biopsy, which is widely used for this purpose, is limited by the considerable rate of non-diagnostic or non-interpretable conclusions. Therefore, it is highly desirable to acquire a new diagnostic means for thyroid cancer. We have recently described a marked over-expression of the MUC1 gene in thyroid papillary-carcinoma tissue, as compared with various benign thyroid pathologies. As the amount of mRNA obtainable by FNA is not amenable to hybridization analysis, we amplified the mRNA sequence of the MUC1-gene upstream of the variable number tandem repeat array using the reverse-transcription polymerase chain reaction (RT-PCR). Seven out of 8 FNA samples obtained from thyroid papillary carcinoma resulted in 336 and 309 base-pair products. In contrast, in all 13 FNA samples obtained from various benign pathologies, only the smaller RT-PCR product was observed. Sequence analysis of the RT-PCR products indicates that alternative splicing of the exon 2 acceptor site accounts for the difference between the 2 amplification products. It is suggested that RT-PCR of the MUC1-gene transcript may add a biomolecular diagnostic dimension to the routine cytological preoperative FNA diagnosis.

Intramuscular immunisation with MUC1 cDNA can protect C57 mice challenged with MUC1-expressing syngeneic mouse tumour cells

Much interest is currently being shown in immunotherapy as a treatment for cancer since several tumour-associated antigens have been identified and the genes encoding them cloned. One such molecule is the tumour-associated human MUC1 gene product. In this report we describe tumour rejection studies in a C57B1 murine model system with syngeneic MUC1-expressing tumour cells designed to examine the efficacy of MUC1 cDNA as an immunogen. Intra-muscular immunisation with 100 microgram MUC1 cDNA 3 times at 3-weekly intervals resulted in tumour protection in approximately 80% of mice. Tumour protection was dose-dependent, with 50-100 microgram being the most effective dose. Both humoral and cell-mediated MUC1-specific immune responses were detected. Anti-MUC1 antibodies were detected after immunisation with DNA alone, indicating that the injected DNA was expressed. Humoral immune responses did not correlate with tumour rejection. Tumour challenge with syngeneic tumour cells expressing MUC1 appeared to be a pre-requisite for the generation of MUC1-specific cytotoxic T lymphocytes.

Induction of cellular immunity in chimpanzees to human tumor-associated antigen mucin by vaccination with MUC-1 cDNA-transfected Epstein-Barr virus-immortalized autologous B cells

Aberrant glycosylation of the mucin molecule (encoded by the gene MUC-1) on human epithelial cell tumors leads to the exposure of tumor-associated epitopes recognized by patients' antibodies and cytotoxic T cells. Consequently, these epitopes could be considered targets for immunotherapy. We designed a cellular vaccine, employing, instead of tumor cells, autologous Epstein-Barr virus (EBV)-immortalized B cells as carriers of tumor-associated mucin, to take advantage of their costimulatory molecules for T-cell activation. The vaccine was tested in chimpanzees because of the identity of the human and chimpanzee MUC-1 tandem repeat sequence. EBV-immortalized B cells derived from two chimpanzees were transfected with MUC-1 cDNA, treated with glycosylation inhibitor phenyl-N-acetyl-alpha-D-galactosaminide to expose tumor-associated epitopes, irradiated, and injected subcutaneously four times at 3-week intervals. One vaccine preparation also contained cells transduced with the interleukin 2 (IL-2) cDNA and producing low levels of IL-2. Already after the first injection we found in the peripheral blood measurable frequency of cytotoxic T-cell precursors specific for underglycosylated mucin. The highest frequency observed was after the last boost, in the lymph node draining the vaccination site. Delayed-type hypersensitivity reaction to the injected immunogens was also induced, whereas no appearance of mucin-specific antibodies was seen. Long-term observation of the animals yielded no signs of adverse effects of this immunization. Autologous antigen-presenting cells, like EBV-immortalized B cells, expressing tumor-associated antigens are potentially useful immunogens for induction of cellular anti-tumor responses in vivo.

The polymorphic epithelial mucin: potential as an immunogen for a cancer vaccine

The identification and cloning of several tumour antigens together with an improvement in the understanding of the mechanisms involved in antigen presentation and immune recognition has opened up the possibility of using active specific immunotherapy as a treatment for certain cancers. This review discusses the tumour-associated MUC1 gene product of the polymorphic epithelial mucin (PEM), as a potential target molecule for cancer treatment. PEM is both over-expressed and aberrantly glycosylated in many carcinomas resulting in an antigenically distinct molecule. Furthermore, immune responses specific for PEM have been detected in cancer patients. Both syngeneic and transgenic murine model systems have been developed in order to compare the efficacy and toxicity of various PEM-based immunogens in tumour rejection studies, and to further improve the understanding of antigen presentation and the mechanisms underlying tumour rejection. Such models also allow the examination of MUC1-based immunogens as a treatment for existing tumours. Clinical trials in progress using immunogens based on the MUC1 gene product are briefly discussed.

Detection of breast cancer micrometastases in axillary lymph nodes by means of reverse transcriptase-polymerase chain reaction. Comparison between MUC1 mRNA and keratin 19 mRNA amplification

Usefulness of MUC1 mRNA and keratin 19 mRNA as a target of reverse-transcriptase polymerase chain reaction (RT-PCR) was compared in the detection of breast cancer micrometastases in axillary lymph nodes. RT-PCR amplification of MUC1 mRNA and keratin 19 mRNA was conducted using total RNA samples. RT-PCR products were stained with ethidium bromide and analyzed by agarose gel electrophoresis. Expression of both MUC1 mRNA and keratin 19 mRNA was detected by RT-PCR in a breast cancer cell line (MRK) and in all the 23 primary breast cancers but not in the control lymph nodes obtained from patients with benign diseases. A serial dilution study of MRK cells against normal lymph node cells has shown that detection sensitivity of MUC1 RT-PCR and keratin 19 RT-PCR were 1/10(5) and 1/10(6) (cancer/lymph node cells), respectively. Sixty-three axillary lymph nodes were obtained from 23 patients with primary breast cancer, and metastases in each lymph node were investigated by histological examination (hematoxylin and eosin sections) and RT-PCR method. In all 10 lymph nodes, which were histologically metastasis-positive, both MUC1 mRNA and keratin mRNA were detected by RT-PCR. Of the 53 histologically negative lymph nodes, 3 (6%) and 5 (9%) lymph nodes were found to express MUC1 mRNA and keratin 19 mRNA, respectively, indicating the presence of micrometastases which could be detected by RT-PCR but not by histological examination. These results demonstrate the usefulness of both MUC1 RT-PCR and keratin 19 RT-PCR in the detection of breast cancer micrometastases in lymph nodes, and also indicate the superiority of keratin 19 RT-PCR over MUC1 RT-PCR because of its higher detection sensitivity.

Two additional polymorphisms within the hypervariable MUC1 gene: association of alleles either side of the VNTR region

The gene MUC1 codes for a mucin-type glycoprotein and like most of the other mucin genes shows variable number tandem repeat (VNTR) polymorphism within the coding region. A polymorphism due to a G/A substitution in exon 2, responsible for a genetically determined variation in splicing of the MUC1 transcript, has also been reported (Ligtenberg et al. 1990, 1991). Here we describe the detection of this nucleotide substitution polymorphism by single stranded conformational analysis of genomic DNA and we also report a CA repeat polymorphism within intron 6 of the gene. Haplotypes were determined in a series of families and the common alleles of these two polymorphisms were found to be associated. These results support the notion that the VNTR polymorphism in the coding sequence of MUC1 is not caused by unequal reciprocal recombination at meiosis.

The epithelial mucin, MUC1, of milk, mammary gland and other tissues

MUC1 is a mucin-type glycoprotein that is integrally disposed in the apical plasma membrane of the lactating epithelial cell and protrudes from the cell surface into the alveolar lumen where milk is stored. Envelopment of milk fat globules by this membrane accomplishes their secretion and conveys MUC1 into milk. The human form of this mucin has been detected in many other organs, tissues and body fluids. It projects from the cell surface as long filaments. In the human and a number of other species, MUC1 is polymorphic due to variable numbers of a tandemly repeated segment 20 amino acids in length. The individual codominantly expresses two alleles for the mucin so that differences in its size among individuals and between the two forms of an individual are observed. The tandem repeats are rich in serines and threonines which serve as O-glycosylation sites. Carbohydrate content of MUC1, as isolated from milk of human, bovine and guinea pig, is approximately 50%. The oligosaccharides carry substantial sialic acid at their termini and this accounts for two putative functions of this mucin, i.e., to keep ducts and lumens open by creating a strong negative charge on the surface of epithelial cells which would repel opposite sides of a vessel, and to bind certain pathogenic microorganisms. MUC1 is protease resistant (trypsin, chymotrypsin and pepsin) and large fragments of it can be found in the feces of some but not all breast-fed infants. MUC1 has a highly varied structure because of its polymorphism, qualitative and quantitative variations in its glycosylation between tissues, individuals and species, and differences due to divergence in the nucleotide sequences among species. Sequencing of the MUC1 gene for various species is showing promise of revealing unique evolutionary relationships and has already indicated conserved aspects of the molecule that may be functionally important. Among these are positions of serine, threonine and proline in the tandem repeats and a high degree of homology in the transmembrane and cytoplasmic segments of the molecule.

Delayed mammary tumor progression in Muc-1 null mice

The mucin gene, Muc-1, encodes a high molecular weight integral membrane glycoprotein that is present on the apical surface of most simple secretory epithelial cells. Muc-1 is highly expressed and aberrantly glycosylated by most carcinomas and metastatic lesions. Numerous functions have been proposed for this molecule, including protection of the epithelial cell surface, an involvement in epithelial organogenesis, and a role in tumor progression. Mice deficient in Muc-1 were generated using homologous recombination in embryonic stem cells. These mice appeared to develop normally and were healthy and fertile. However, the growth rate of primary breast tumors induced by polyoma middle T antigen was found to be significantly slower in Muc-1 deficient mice. This suggests that Muc-1 plays an important role in the progression of mammary carcinoma.

Breast cancer selective gene expression and therapy mediated by recombinant adenoviruses containing the DF3/MUC1 promoter

The high molecular weight mucin-like glycoprotein, DF3 (MUC1), is overexpressed in the majority of human breast cancers. Here we demonstrate that replication defective recombinant adenoviral vectors, containing the DF3 promoter (bp -725 to +31), can be used to express beta-galactosidase (Ad.DF3-betagal) and the herpes simplex virus thymidine kinase (HSV-tk) gene (Ad.Df3-tk) in DF3 positive breast carcinoma cell lines. In vivo experiments using breast tumor implants in nude mice injected with Ad.DF3-betagal demonstrated that expression of the beta-galactosidase gene is limited to DF3-positive breast cancer xenografts. Moreover, in an intraperitoneal breast cancer metastases model, we show that i.p. injection of Ad.DF3-tk followed by GCV treatment results in inhibition of tumor growth. These results demonstrate that utilization of the DF3 promoter in an adenoviral vector can confer selective expression of heterologous genes in breast cancer cells in vitro and in vivo.

CTL in mice immunized with human mucin 1 are MHC-restricted

CTLs that recognize tumor Ags have been described in mice and humans, particularly for melanoma. These CTLs are CD8+, which is MHC-restricted. In contrast, in human carcinomas of the breast, pancreas, or ovary, and in multiple myeloma, CD8+ CTLs have been described that lyse targets expressing human MUC1 in a non-MHC-restricted manner. On the basis of these observations, we immunized mice with conjugates of mannan-human fusion protein, human mucin 1 (MUC1), which produced CD8+ CTLs. In contrast to the human anti-MUC1 CTLs found in cancer patients, the murine anti-MUC1 CTLs were clearly MHC-restricted, e.g., in inbred mice of the H-2-b, d, k, s, or z haplotypes; the H-2 restriction was also confirmed in H-2 congenic strains. Tests of H-2 recombinant strains demonstrated that MUC1 peptides were able to associate with D or K class I molecules of the b, d, or k haplotypes. Mice lacking MHC-class I molecules made weak CTL responses that were H-2Db-restricted, and in the class I H-2Kbm1 mutant strain, CTL restriction was also shown. Finally, cold target inhibition studies demonstrated that Kb and Db are recognized similarly, but Kk is less well recognized. Thus, anti-MUC1 CTLs induced by immunization of mice are different from those obtained from patients. The immunization of cancer patients with MUC1 peptides is now undergoing clinical trials and it will be of interest to observe whether the CTLs induced are HLA-restricted, not restricted, or whether both types of CTLs are produced.

Polymorphic forms of the epithelial mucin, PAS-I (MUC1), in milk of Holstein cows (Bos taurus)

The polymorphic epithelial mucin, PAS-I (also known as MUC1), in individual milk samples from 119 Holstein cows was resolved into bands on SDS-gels. Mobility indices established for these bands provided evidence of four and possibly five polymorphic forms. Sialic acid, a major component of the oligosaccharide portion of PAS-I, was removed from the mucin by treatment of milk samples with neurominidase. This reduced the mobility of the mucin bands but did not alter their mobility relationships within a sample or among samples. Consideration of evidence from this and other studies indicates that the four or five polymorphic forms correspond to alleles, which are inherited, one each from sire and dam, and co-dominantly expressed. It appears that the Holstein population may carry several more alleles for PAS-I than do Ayrshire, Jersey or Brown Swiss cattle. In addition to these breed differences, some remarkable molecular differences have been noted between MUC1 (PAS-I) of human and mouse suggesting that research regarding molecular evolution of this mucin could provide another approach to understanding relationships among species.