Episialin (MUC1) overexpression inhibits integrin-mediated cell adhesion to extracellular matrix components

MUC-1 mucin in normal human salivary glands detected by HMFG-1 and HMFG-2 monoclonal antibodies

The aim of this study was to determine the immunoexpression of normal salivary gland cells using two human milk fat globule membrane protein antibodies (HMFG-1 and HMFG-2). Paraffin-embedded, 5 microm-thick slides from parotid and submandibular gland tissues were cut and immunostained with monoclonal antibodies HMFG-1 and HMFG-2 against MUC1 protein. HMFG antigens were found in secretory epithelial cells and ductal cells lining the striated and intercalated ducts in the intraductal secretion material, and sometimes in the myoepithelial cells. Our results suggest that HMFG-1 and HMFG-2 proteins may play a role in normal salivary gland function, mainly in the manufacturing and secretion of saliva.

Mucin-type O-glycosylation and its potential use in drug and vaccine development

Mucin-type O-glycans are found on mucins as well as many other glycoproteins. The initiation step in synthesis is catalyzed by a large family of polypeptide GalNAc-transferases attaching the first carbohydrate residue, GalNAc, to selected serine and threonine residues in proteins. During the last decade an increasing number of GalNAc-transferase isoforms have been cloned and their substrate-specificities partly characterized. These differences in substrate specificities have been exploited for in vitro site-directed O-glycosylation. In GlycoPEGylation, polyehylene glycol (PEG) is transferred to recombinant therapeutics to specific acceptor sites directed by GalNAc-transferases. GalNAc-transferases have also been used to control density of glycosylation in the development of glycopeptide-based cancer vaccines. The membrane-associated mucin-1 (MUC1) has long been considered a target for immunotherapeutic and immunodiagnostic measures, since it is highly overexpressed and aberrantly O-glycosylated in most adenocarcinomas, including breast, ovarian, and pancreatic cancers. By using vaccines mimicking the glycosylation pattern of cancer-cells, it is possible to overcome tolerance in transgenic animals expressing the human MUC1 protein as a self-antigen providing important clues for an improved MUC1 vaccine design. The present review will highlight some of the potential applications of site-directed O-glycosylation.

Structure and Function of the Cell Surface (Tethered) Mucins

Cell surface mucins are large transmembrane glycoproteins involved in diverse functions ranging from shielding the airway epithelium against pathogenic infection to regulating cellular signaling and transcription. Although hampered by the relatively recent characterization of cell surface mucins and the difficulties inherent in working with molecules of their size, numerous studies have placed the tethered mucins in the thick of normal and diseased lung physiology. This review focuses on the three best-characterized cell surface mucins expressed in the respiratory tract: MUC1, MUC4, and MUC16.

MUC1 is a counter-receptor for myelin-associated glycoprotein (Siglec-4a) and their interaction contributes to adhesion in pancreatic cancer perineural invasion

Perineural invasion in pancreatic adenocarcinoma, a common pathologic phenomenon whereby cancer cells invade and intimately contact the endoneurium of pancreatic nerves, is thought to contribute to both pain and local disease recurrence. MUC1, a type I transmembrane mucin that can affect the adhesive properties of cells, contains a large extracellular tandem repeat domain, which is heavily glycosylated in normal epithelia, but is overexpressed and differentially glycosylated in pancreatic cancer. This altered glycosylation includes the shortened core I O-glycans for monosialyl and disialyl T antigens. Myelin-associated glycoprotein (MAG), a membrane-bound protein expressed on oligodendrocytes and Schwann cells, binds myelin to neurons. MAG's preferred ligands are derivatives of the monosialyl and disialyl T antigen. We investigated whether MUC1 is a counter-receptor for MAG and if their interaction contributed to pancreatic perineural invasion. Results showed that MAG binds pancreatic cells expressing MUC1, that this binding is sialidase-sensitive, and that MAG physically associates with MUC1. Heterotypic adhesion assays between pancreatic cancer cells and Schwann cells revealed that increased expression of MUC1 or MAG enhanced adhesion. Conversely, specific inhibition of MAG or sialyl-T MUC1 partially blocked adhesion. Immunohistochemical analysis of pancreatic perineural invasion showed the expression of both MUC1 and MAG. These results support the hypothesis that the adhesive interactions between MUC1 and MAG are of biological significance in pancreatic cancer perineural invasion.

Structure, evolution, and biology of the MUC4 mucin

Mucins are high-molecular-weight glycoproteins and are implicated in diverse biological functions. MUC4, a member of transmembrane mucin family, is expressed in airway epithelial cells and body fluids like saliva, tear film, ear fluid, and breast milk. In addition to its normal expression, an aberrant expression of MUC4 has been reported in a variety of carcinomas. Among various potential domains of MUC4, epidermal growth factor (EGF) -like domains are hypothesized to interact with and activate the ErbB2 receptors, suggesting an intramembrane-growth factor function for MUC4. The heavily glycosylated tandem repeat domain provides the structural rigidity to the extended extracellular region. MUC4, by virtue of its extended structure, serves as a barrier for some cell-cell and cell-extracellular matrix interactions and as a potential reservoir for certain growth factors. An intricate relationship between MUC4 and growth factor signaling is also reflected in the transcriptional regulation of MUC4. The MUC4 promoter has binding sites for different transcription factors, which are responsible for the regulation of its expression in different tissues. The interferon-gamma, retinoic acid, and transforming growth factor-beta signaling pathways regulate MUC4 expression in a partially interdependent manner. Taken together, all of these features of MUC4 strongly support its role as a potential candidate for diagnostic and therapeutic applications in cancer and other diseases.

The MUC1 HMFG1 glycoform is a precursor to the 214D4 glycoform in the human uterine epithelial cell line, HES

MUC1, a type I transmembrane glycoprotein expressed on most epithelia and many cancer cells, is involved in embryo implantation and tumor progression. A series of antibodies directed against the MUC1 ectodomain have been used to study MUC1 expression in the female reproductive tract, sometimes with apparently contradictory results. In the current study, we used two monoclonal MUC1 antibodies, 214D4 and HMFG1, to study the relationship between these MUC1 glycoforms in the human uterine epithelial cell line, HES, and human endometrial extracts. In response to tumor necrosis factor stimulation, accumulation of the HMFG1-reactive forms preceded that of the 214D4-reactive forms. Following inhibition of protein synthesis by cycloheximide, HMFG1-reactive species were lost rapidly (metabolic half-life [T(1/2)] = 20 min), while there was no change in the level of the 214D4-reactive forms even after 80 min. HMFG1-reactive forms had smaller oligosaccharide chains than the 214D4-reactive forms, and could not be detected on the cell surface of intact cells or in the shed (media) fraction, although they were readily detected in permeabilized cells. Both 214D4- and HMFG1-reactive species were detected in human endometrial extracts throughout the cycle; however, consistent with the HES cell studies, the HMFG1-reactive species were both smaller and less abundant than the 214D4-reactive species. Consistent with this observation, we found that HMFG1-reactive species were difficult to detect in tissue sections unless predigested with neuraminidase, indicating that these structures are rapidly sialylated during synthesis. In contrast, 214D4-reactive species were robustly detected in both proliferative and secretory stages. Collectively, these studies indicate that the HMFG1-reactive glycoform is a precursor of the 214D4-reactive glycoform in HES cells and normal uterine epithelia. Therefore, discrepancies in patterns of MUC1 expression in other studies may be due to failure to account for these glycoform relationships.

MUC16 is lost from the uterodome (pinopode) surface of the receptive human endometrium: in vitro evidence that MUC16 is a barrier to trophoblast adherence

In order for the preimplantation embryo to implant into the uterus, the trophoblast cells must initially adhere to the uterine epithelial surface. In preparation, the luminal secretory cells of the epithelium lose their nonadhesive character and their surface microvilli and bulge into the lumen, forming uterodomes (pinopodes; uterodome is used instead of pinopode, since in humans the surface membrane exocytoses rather than endocytoses (Murphy, Hum Reprod 2000; 15:2451-2454). Previous research has led to the hypothesis that loss of the nonadhesive membrane-spanning mucin MUC1 from the uterodome surface allows trophoblast adherence. Immunofluorescence microscopic assay of luminal epithelia on human uterine biopsies taken from LH+0 to LH+13 show that another membrane-spanning mucin, MUC16, was lost from uterodome surfaces in all samples taken during the receptive phase, LH+6 to LH+8 (n = 12), and that MUC1 was present on uterodomes in 4 of 12 samples and on all ciliated cells of the epithelium in the receptive phase. Short interfering RNA (siRNA) knockdown of MUC16 in a uterine epithelial cell line ECC-1 that, like uterine epithelium, expresses MUC16 and MUC1 allowed increased adherence of cells of a trophoblast cell line. In parallel experiments, siRNA knockdown of MUC1 did not affect trophoblast cell adherence. These data indicate that MUC16 is a membrane component of the nonreceptive luminal uterine surface, which prevents cell adhesion, and that its removal during uterodome formation facilitates adhesion of the trophoblast.

Identification of cellular isoform of oviduct-specific glycoprotein: role in oviduct tissue remodeling?

The oviduct is known to secrete mucins (MUC1 and MUC9) under the influence of ovarian steroids. The secreted form of MUC1 binds gametes in the oviduct, whereas the cellular form seen in breast cancers has been implicated in cell adhesion and morphogenesis. The secreted MUC9 or oviduct-specific glycoprotein (OGP), in addition to being a mucin, belongs to family 18 glycosylhydrolases and is known to bind gametes and embryos in the oviduct. Studies in our laboratory have identified non-muscle myosin IIA (involved in cell shape, polarity, and morphogenesis) as the protein partner to OGP in gametes. In view of the crucial role of the cortical cytoskeleton in the selective internalization of tight junctions (TJs) /adherent junctions (AJs) or apical junctional complex (AJC) in simple epithelial cells during tissue remodeling, the present study has been undertaken to evaluate the existence of a cellular form of OGP in oviductal tissue, which itself undergoes cyclic tissue remodeling. In silico analysis of the deduced amino-acid sequence of OGP has revealed the presence of several conserved motifs; these imply that OGP is a component of multi-protein complexes such as TJs. Corroborative immunoelectron-microscopic analysis in peri-ovulatory oviduct epithelia in the bonnet monkey has revealed the presence of OGP at the TJ. Co-localization studies of OGP and cadherin demonstrate that, whereas OGP is localized at the tonofilaments of the TJs, cadherin is localized at the intercellular space of the AJ. The possible role of OGP in oviductal tissue remodeling is discussed in light of the present findings and those reported in the literature.

Biological and therapeutic significance of MUC1 with sialoglycans in clear cell adenocarcinoma of the ovary

A monoclonal antibody (mAb) MY.1E12 was applied to detect MUC1 with sialylated glycans in a total of 55 formalin-fixed, paraffin-embedded surgical specimens of ovarian clear cell adenocarcinomas. A reverse correlation between the binding levels of this mAb and patient survival was demonstrated. To examine the role of MUC1 in ovarian clear cell carcinomas, two cDNA encoding MUC1 were transfected into ES-2 ovarian clear cell carcinoma cells. By comparing these cells, the role of MUC1 in tumorigenicity, chemosensitivity and survival under anoikis conditions were assessed. The results indicate that MUC1 expressed on ovarian clear cell carcinoma cells is causally involved in the malignant behavior.

The expression pattern of MUC1 (EMA) is related to tumour characteristics and clinical outcome in 'pure' ductal carcinoma in situ of the breast

AIMS

To classify MUC1 according to five predefined expression patterns in ductal carcinoma in situ (DCIS) and related clinicopathological parameters, coexpression of other biological markers and prognosis.

METHODS AND RESULTS

With a manual tissue arrayer, 92% (n = 80) of the 87 DCIS samples were successfully targeted. Immunohistochemistry was carried out for MUC1, oestrogen receptor (ER), progesterone receptor (PR), Her2/Neu, p53 and cyclin D1. Entire membrane expression was related to Her2/neu negativity (P =0.042). Apical membrane expression was associated with low grade (P = 0.027), Her2/neu negativity (P = 0.014) and PR positivity (P = 0.005). Focal cytoplasmic expression was related to high grade (P = 0.006). Diffuse cytoplasmic expression was associated with high grade (P = 0.004), large tumour size (P = 0.046), Her2/neu positivity (P =0.042) and cyclin D1 positivity (P = 0.002). On the basis of these analyses the four patterns were reclassified as membranous or cytoplasmic expression. On multivariate analysis, cytoplasmic MUC1 expression (hazard ratio 8.5, 95% confidence interval 1.0, 73.0; P = 0.04) was the only independent predictor of local recurrence.

CONCLUSIONS

Four patterns of MUC1 expression are recognized in DCIS that suggest a relationship to functional differentiation and can be simplified into two types that are clinically relevant and could therefore be helpful in the distinction between different subgroups of DCIS.

Adherence of nontypeable Streptococcus pneumoniae to human conjunctival epithelial cells

Conjunctivitis outbreaks have occurred in the US in which nontypeable (NT) Streptococcus pneumoniae (Pnc) strains have been identified as the etiologic agent; however, the pathogenesis of Pnc conjunctivitis has not been extensively evaluated. Here we assessed the adhesive and invasive properties of 13 NT US conjunctivitis outbreak strains (cPnc) using an immortalized human conjunctival epithelial cell (HCjE) line expressing high or low levels of mucin as a surrogate for in vivo ocular surface events. Studies reveal differential binding efficiencies (up to 18-fold) among cPnc strains to HCjE cells and reduced or little adherence efficiency to high mucin-expressing (HME-HCjE). Additionally, in the presence of exogenous mucin there is considerable inhibition (20% to approximately 100%) of bacterial binding to the HCjE cells. Invasion assays suggest that the cPnc are internalized in HCjE, and less in HME-HCjE cells. Microarray analysis of cPnc isolates revealed an up-regulation of Pnc neuraminidases, and treatment of HME-HCjE cells with exogenous neuraminidase resulted in a 2-13-fold enhancement in cPnc binding. The results indicate that mucin acts as a protective barrier in vitro and that neuraminidases, which can degrade mucin, may be contributing factors leading to bacterial adherence, a first step in the pathogenesis of this transmissible infection.

The expression pattern of MUC1 (EMA) is related to tumour characteristics and clinical outcome of invasive ductal breast carcinoma

AIMS

To clarify MUC1 patterns in invasive ductal breast carcinoma and to relate them to clinicopathological parameters, coexpression of other biological markers and prognosis.

METHODS AND RESULTS

Samples from 243 consecutive patients with primary ductal carcinoma were incorporated into tissue microarrays (TMAs). Slides were stained for MUC1, oestrogen receptor (ER), progesterone receptor (PR), Her2/neu, p53 and cyclin D1. Apical membrane MUC1 expression was associated with smaller tumours (P = 0.001), lower tumour grades (P < 0.001), PR positivity (P = 0.003) and increased overall survival (OS; P = 0.030). Diffuse cytoplasmic MUC1 expression was associated with cyclin D1 positivity (P = 0.009) and increased relapse-free survival (RFS; P = 0.034). Negativity for MUC1 was associated with ER negativity (P = 0.004), PR negativity (P = 0.001) and cyclin D1 negativity (P = 0.009). In stepwise multivariate analysis MUC1 negativity was an independent predictor of both RFS [hazard ratio (HR) 3.5, 95% confidence interval (CI) 1.5, 8.5; P = 0.005] and OS (HR 14.7, 95% CI 4.9, 44.1; P < 0.001).

CONCLUSIONS

The expression pattern of MUC1 in invasive ductal breast carcinoma is related to tumour characteristics and clinical outcome. In addition, negative MUC1 expression is an independent risk factor for poor RFS and OS, besides 'classical' prognostic indicators.

Cell autonomous sorting and surface positioning in the formation of primitive endoderm in embryoid bodies

The differentiation and formation of the primitive endoderm in early embryos can be mimicked in vitro by the aggregation of embryonic stem cells to form embryoid bodies. We present morphological evidence that primitive endoderm cells often first locate in the interior of embryoid bodies and subsequently migrate to the surface. Cell mixing experiments indicate that surface positioning is an intrinsic property of endoderm epithelial cells. Moreover, Disabled-2 (Dab2) is required for surface sorting and positioning of the endoderm cells: when Dab2 expression was eliminated, the differentiated endoderm epithelial cells distributed throughout the interior of the embryoid bodies. Surprisingly, E-cadherin is dispensable for primitive endoderm differentiation and surface sorting in embryoid bodies. These results support the model that primitive endoderm cells first emerge in the interior of the inner cell mass and are subsequently sorted to the surface to form the primitive endoderm.

Tall cell variant of papillary thyroid carcinoma without extrathyroid extension: biologic behavior and clinical implications

BACKGROUND

The tall cell variant (TCV) is a histologic subtype of papillary thyroid carcinoma (PTC) that is more aggressive than "classical" PTC. Most authors believe that TCV's worse prognosis is related to older age at presentation, larger tumor size, and high frequency of extrathyroid tumor extension (ETE). To assess the biologic and clinical behavior of TCV without ETE, we performed a detailed comparative clinicopathologic analysis of classical PTC and TCV without ETE.

METHODS

TCV was defined as a PTC harboring >50% tall cells, while classical PTC was restricted to those tumors containing >1% papillae and <30% tall cells. Microscopic analysis and chart review identified 62 cases of TCV and 83 classical PTC without ETE. These patients were analyzed for various pathologic, imaging, and clinical parameters including outcome.

RESULTS

There was no statistical difference between TCV and classical PTC in relation to age, gender, tumor size, risk stratification, type of therapy, and length of follow-up. TCV displayed more invasion of the tumor capsule and more often infiltrated into the thyroid capsule (p = 0.047 and 0.0004, respectively). Among patients with microscopically assessable regional lymph node (LN), 33 of 49 (67.3%) patients with TCV had LN metastasis at presentation, while only 24 of 60 (40%) classical PTC had positive nodes (p = 0.004). In multivariate analysis, histologic subtype (TCV vs. classical PTC) was the only independent factor associated with LN metastases (p = 0.007). In patients with adequate follow-up, 4 of 62 (6.5%) classical PTC and 7 of the 47 (14.9%) TCV had thyroid cancer recurrence (p = 0.202). TCV recurred at a distant site (3 of 47, 6.4%) while none of the 62 classical PTC developed distant metastases (p = 0.077).

CONCLUSION

TCV without ETE is biologically a more aggressive tumor than classical PTC without ETE independent of age, gender, and tumor size.

TTYH2, a human homologue of the Drosophila melanogaster gene tweety, is up-regulated in colon carcinoma and involved in cell proliferation and cell aggregation

AIM: To investigate the expression patterns of TTYH2 in the human colon cancer and colon cancer cell lines and to evaluate the inhibitory effect of small interfering RNA (siRNA) on the expression of TTYH2 in colon cancer cell lines.

METHODS: We investigated the expression patterns of TTYH2 in colon cancer, adjacent non-tumorous colon mucosa, and cancer cell lines (DLD-1, caco-2, and Lovo) by RT-PCR. Furthermore, a siRNA plasmid expression vector against TTYH2 was constructed and transfected into DLD-1 and Caco-2 with Lipofectamine^TM 2000. The down regulation of TTYH2 expression was detected by RT-PCR and the role of siRNA in inducing cell proliferation and cell aggregation was evaluated by MTT and aggregation assay.

RESULTS: TTYH2 gene expression in colon cancer tissue was significantly up-regulated compared with normal colonic mucosa (1.23 ± 0.404 vs 0.655 ± 0.373, P = 0.0103). Colon cancer derived cell lines including DLD-1, Caco-2, and Lovo also expressed high levels of TTYH2. In contrast, transfection with siRNA-TTYH2 significantly inhibited both proliferation and scattering of these cancer cell lines.

CONCLUSION: The present work demonstrates, for the first time, that the TTYH2 gene expression is significantly up-regulated in colon cancer. The TTYH2 gene may play an important role in regulating both proliferating and metastatic potentials of colorectal cancer.

Prognostic significance of mucins in colorectal cancer with different DNA mismatch-repair status

BACKGROUND

Expression of mucin antigen MUC1 and down regulation of MUC2 are associated with adverse prognosis in colorectal cancer (CRC), but their prognostic significance with respect to differing DNA mis- match repair (MMR) status is poorly understood.

OBJECTIVE

To determine the prognostic significance of MUC1 and MUC2 in CRC with different MMR statuses.

METHODS

Using the tissue microarray (TMA) technique, a series of 1420 unselected, non-consecutive CRC resections was subdivided into three groups: (1) MMR-proficient; (2) MLH1-negative; and (3) presumed hereditary non-polyposis colon cancer (HNPCC). Immunohistochemical analysis of MUC1 and MUC2 expression (>0%) and loss (0%) was performed, and the results were correlated with clinicopathological parameters.

RESULTS

In MMR-proficient CRC, MUC1 expression was more frequently found in tumours with higher tumour stage (p=0.004) and higher tumour grade (p=0.041) and loss of MUC2 was associated with higher tumour stage (p=0.028), node stage (p=0.001), presence of vascular invasion (p=0.028) and worse survival (p=0.034). In MLH1-negative CRC, MUC2 loss was associated with the presence of lymph node metastasis (p=0.028) and worse survival (p=0.015), but there was no association between MUC1 expression and clinicopathological features. In presumed HNPCC, MUC1 expression and MUC2 loss were not associated with clinicopathological parameters.

CONCLUSIONS

Mucins have a prognostic significance in sporadic CRC, but not in hereditary CRC. Loss of MUC2 is an adverse prognostic factor in MMR-proficient and MLH1-negative CRC, whereas MUC1 expression is associated with tumour progression in MMR-proficient CRC only.

Prognostic Significance of the MUC1 and MUC4 Expressions in Thyroid Papillary Carcinoma

OBJECTIVES

The aim of the present study was to examine the expressions of mucin genes MUC1 and MUC4 and to evaluate the difference of their expressions in normal thyroid tissue, follicular adenoma, and papillary carcinoma. Furthermore, we aimed to estimate their prognostic significance in papillary carcinoma.

METHODS

We performed semiquantitative reverse-transcription polymerase chain reaction for determining the MUC1 and MUC4 mRNA expressions, and immunohistochemical staining was performed to determine the MUC1 and MUC4 protein expressions in 22 normal thyroid tissues, 22 follicular adenomas, and 15 papillary carcinomas. The semiquantitative scoring of the immunohistochemical staining was compared with the prognostic factors for thyroid carcinoma to evaluate the prognostic significance in 87 papillary carcinoma patients.

RESULTS

The MUC1 mRNA of the papillary carcinoma tissue showed an increased expression level compared with the other tissues. However, the expression level of MUC4 mRNA was weak in all the specimens, and this was not significantly different among the three groups. MUC1 immunoreactivity was more intense in papillary carcinoma but not in the other tissues. MUC4 was not expressed in all thyroid tissues. The expression of MUC1 was significantly associated with tumor size, extrathyroidal spread, and TNM stage (P < .05).

CONCLUSIONS

Up-regulation of MUC1 may play a more important role than that of MUC4 in the development of thyroid papillary carcinoma, and it may have some significance as a prognostic factor.

MUC1 inhibits cell proliferation by a beta-catenin-dependent mechanism

beta-Catenin binds to the cytoplasmic region of the type 1 membrane glycoprotein MUC1. In the current study, we utilized HEK293T cells expressing the full-length MUC1 protein, or a CD8/MUC1 fusion protein containing only the MUC1 cytoplasmic tail, to investigate the effects of beta-catenin binding to MUC1 on downstream beta-catenin-dependent events. Compared with HEK293T cells transfected with empty vector or CD8 alone, expression of the MUC1 cytoplasmic tail inhibited beta-catenin binding to E-cadherin, decreased translocation of beta-catenin into the nucleus, reduced activation of the LEF-1 transcription factor, and blocked expression of the cyclin D1 and c-Myc proteins. Furthermore, expression of MUC1 was associated with decreased cell proliferation, either in the context of the transfected HEK293T cells, or when comparing wild type (Muc1(+/+)) vs. knockout (Muc1(-/-)) mouse primary tracheal epithelial cells. We conclude that MUC1 inhibits cell proliferation through a beta-catenin/LEF-1/cyclin D1/c-Myc pathway.

MUC1 is involved in trophoblast transendothelial migration

The factors that regulate trophoblast invasion of the uterine vasculature are incompletely understood. In this paper we show that macaque trophoblasts express the mucin, MUC1, and that it is involved in trophoblast-endothelial interaction. Immunocytochemistry, Western blotting and RT-PCR analyses confirmed that MUC1 was expressed by isolated early gestation macaque trophoblasts. MUC1 was also detected in endovascular trophoblasts in sections of placental-decidual tissue during early gestation. A blocking antibody against MUC1 reduced trophoblast adhesion to uterine endothelial cells and also blocked trophoblast transendothelial migration. MUC1 is known to bind to Intercellular Adhesion Molecule-1 (ICAM-1) in other systems. Incubation in the presence of a blocking antibody against Intercellular Adhesion Molecule-1 (ICAM-1) or recombinant ICAM-1 modestly, but significantly, reduced transendothelial trophoblast migration. These results are consistent with the idea that MUC1 is involved in trophoblast adhesion to uterine endothelial cells and in trophoblast transendothelial migration.

Expression of Tumor-Associated Differentiation Antigens, MUC1 Glycoforms and CEA, in Human Thymic Epithelial Cells: Implications for Self-Tolerance and Tumor Therapy

Expression of tissue-restricted self-antigens in the thymus, termed promiscuous gene expression, imposes T cell tolerance and protects from autoimmune diseases. This antigen pool also includes various types of tumor-associated antigens (TAA) previously thought to be secluded from the immune system. The scope of promiscuous gene expression has been defined by mRNA analysis at the global level of isolated medullary thymic epithelial cells (mTECs). Information at the protein level on the frequency of mTECs expressing a given antigen, on coexpression patterns, and post-translational modifications is largely missing. We report here promiscuous expression at the protein level of two TAA, MUC1 and CEA, in situ and in purified human mTECs. Both antigens are expressed in 1% to 3% of mTECs, either individually or coexpressed in the same cell. Using a panel of anti-MUC1 monoclonal antibodies recognizing different post-translational modifications, i.e., glycoforms of MUC1, we show that only fully glycosylated forms of MUC1 and the differentiation-dependent glycoforms were detected on mTECs, but not the cancer-associated glycoforms. Our findings imply that MUC1 and CEA are amenable to central tolerance induction, which might, however, be incomplete in case of tumor cell-restricted MUC1 glycoforms. Knowledge of these subtleties in promiscuous gene expression may, in the future, assist the selection of T cell tumor vaccines for clinical trials.

MUC4 Mucin Potentiates Pancreatic Tumor Cell Proliferation, Survival, and Invasive Properties and Interferes with Its Interaction to Extracellular Matrix Proteins

MUC4, a transmembrane mucin, is aberrantly expressed in pancreatic adenocarcinomas while remaining undetectable in the normal pancreas. Recent studies have shown that the expression of MUC4 is associated with the progression of pancreatic cancer and is inversely correlated with the prognosis of pancreatic cancer patients. In the present study, we have examined the phenotypic and molecular consequences of MUC4 silencing with an aim of establishing the mechanistic basis for its observed role in the pathogenesis of pancreatic cancer. The silencing of MUC4 expression was achieved by stable expression of a MUC4-specific short hairpin RNA in CD18/HPAF, a highly metastatic pancreatic adenocarcinoma cell line. A significant decrease in MUC4 expression was detected in MUC4-knockdown (CD18/HPAF-siMUC4) cells compared with the parental and scrambled short interfering RNA-transfected (CD18/HPAF-Scr) control cells by immunoblot analysis and immunofluorescence confocal microscopy. Consistent with our previous observation, inhibition of MUC4 expression restrained the pancreatic tumor cell growth and metastasis as shown in an orthotopic mouse model. Our in vitro studies revealed that MUC4-associated increase in tumor cell growth resulted from both the enhanced proliferation and reduced cell death. Furthermore, MUC4 expression was also associated with significantly increased invasiveness (P < or = 0.05) and changes in actin organization. The presence of MUC4 on the cell surface was shown to interfere with the tumor cell-extracellular matrix interactions, in part, by inhibiting the integrin-mediated cell adhesion. An altered expression of growth- and metastasis-associated genes (LI-cadherin, CEACAM6, RAC1, AnnexinA1, thrombomodulin, epiregulin, S100A4, TP53, TP53BP, caspase-2, caspase-3, caspase-7, plakoglobin, and neuregulin-2) was also observed as a consequence of the silencing of MUC4. In conclusion, our study provides experimental evidence that supports the functional significance of MUC4 in pancreatic cancer progression and indicates a novel role for MUC4 in cancer cell signaling.

Expression of MUC1 in primary and metastatic human epithelial ovarian cancer and its therapeutic significance

BACKGROUND

MUC1 is associated with cellular transformation and tumorigenicity and is considered as an important tumor-associated antigen (TAA) for cancer therapy. The objective of this study was to evaluate the patterns of MUC1 expression in primary tumors and metastatic lesions in the advanced stages of epithelial ovarian cancers (EOCs) and correlate the expression with clinicopathological features.

METHODS

The expression of MUC1 was examined on frozen tissue sections from primary EOC (n=42), the matched metastatic lesions (n=30) and paraffin-embedded tissue sections from primary EOC (n=60), normal ovarian tissues (n=20) using immunohistochemistry (IHC) by monoclonal antibody (MAb) C595.

RESULTS

The expression of MUC1 was found in 92% (39/42) of EOC and 90% (27/30) of the matched metastatic lesions in frozen tissue sections respectively while the expression of MUC1 was found in 95% (57/60) of EOC and 5% (1/20) of normal ovarian tissues in paraffin-embedded sections respectively. Most of the tumors showed moderate to strong intensity staining while normal ovarian tissues only showed weak intensity staining. The overexpression of MUC1 was significantly associated with various progression parameters such as tumor stage, grade, residual disease status and presence of ascites (P<0.05).

CONCLUSIONS

MUC1 is overexpressed in above 90% of late stage of EOC and of metastatic lesions but not in normal ovarian tissues, and the high expression of MUC1 is correlated with EOC progression. MUC1 antigen may be a useful therapeutic target to prevent the development of incurable, recurrent metastatic EOC.

The MUC13 cell surface mucin is highly expressed by human colorectal carcinomas

Mucins are complex mucosal glycoproteins that can be highly expressed by adenocarcinomas, having diagnostic, therapeutic, and biological significance. MUC13 encodes a cell surface membrane-anchored mucin expressed in the normal gastrointestinal tract, trachea, and kidney as well as colorectal, esophageal, gastric, pancreatic, and lung cancers. MUC13 protein expression was determined immunohistochemically in 99 sporadic colorectal cancers, assessing proportion of tumor cells stained, stain intensity, and localization. In normal colon, intense apical membrane and variable cytoplasmic MUC13 staining was present in both goblet and columnar cells, with strongest reactivity in the upper crypts and surface epithelium. All cancers showed staining of most tumor cells, being most conspicuous in the apical membranes of gland spaces. Left-sided tumors had a higher overall proportion of MUC13-positive tumor cells than right-sided tumors (P < .05), and high staining intensity was more frequent in adenocarcinomas (81%) than mucinous tumors (50%) (P < .05). Poorly differentiated and late-stage tumors were more likely to have high-intensity cytoplasmic staining (P < or = .025). Basolateral cell membranes were stained in 24% of cases, being more common in poorly differentiated tumors (55%) than well or moderately differentiated tumors (16%) (P < or = .001). Partial or full circumferential MUC13 staining was frequently observed in areas of tumor budding. Although MUC13 immunoreactivity was not predictive of patient outcome, there was a trend toward poorer outcome in patients with tumors showing basolateral MUC13. In summary, MUC13 was expressed abundantly by all colorectal cancers, with the highest expression in more poorly differentiated tumors.

The role of MUC1 and MUC3 in the biology and prognosis of colorectal cancer

Background

MUC1 and MUC3 are from a large family of glycoproteins with an aberrant expression profile in various malignancies. Much interest has been focused on the role of these proteins in the development and progression of colorectal cancer; however, no previous studies have included the highly confounding variable of vascular invasion in their survival analysis. Using high throughput tissue microarray technology we assessed the prognostic value of MUC1 and MUC3 expression in the largest cohort of colorectal cancer patients to date. We propose that tumours lacking expression of MUC1 and MUC3 will be more likely to metastasise, due to previously observed loss of cell-cell adhesion, and this will therefore lead to more aggressive cancers with poorer prognosis.

Methods

A tissue micro-array was prepared from tumour samples of 462 consecutive patients undergoing resection of a primary colorectal cancer. A comprehensive prospectively recorded data base with mean follow up of 75 months was collected and included common clinicopathological variables and disease specific survival. Immunohistochemical analysis of MUC1 and MUC3 expression was performed using antibodies NCL-MUC1 and 1143/B7 respectively, results were correlated with the variables within the database.

Results

Positive expression of MUC1 and MUC3 was seen in 32% and 74% of tumours respectively. On univariate analysis no correlation was seen with either MUC1 or MUC3 and any of the clinicopathological variables including tumour grade and stage, vascular invasion and tumour type. Kaplan-Meier analysis demonstrated a significant reduction in disease specific survival with MUC1 positive tumours (p = 0.038), this was not seen with MUC3 (p = 0.552). On multivariate analysis, using Cox proportional hazards model, MUC1 expression was shown to be an independent marker of prognosis (HR 1.339, 95%CI 1.002–1.790, p = 0.048).

Conclusion

MUC1 expression in colorectal cancer is an independent marker of poor prognosis, even when vascular invasion is included in the analysis. These results support previous studies suggesting a role for MUC1 in colorectal cancer development possibly through its effects on cell adhesion.

Disabled-2 is an epithelial surface positioning gene

The formation of the primitive endoderm layer on the surface of the inner cell mass is one of the earliest epithelial morphogenesis in mammalian embryos. In mouse embryos deficient of Disabled-2 (Dab2), the primitive endoderm cells lose the ability to position on the surface, resulting in defective morphogenesis. Embryonic stem cells lacking Dab2 are also unable to position on the surface of cell aggregates and fail to form a primitive endoderm outer layer in the embryoid bodies. The cellular function of Dab2, a cargo-selective adaptor, in mediating endocytic trafficking of clathrin-coated vesicles is well established. We show here that Dab2 mediates directional trafficking and polarized distribution of cell surface proteins such as megalin and E-cadherin and propose that loss of polarity is the underlying mechanism for the loss of epithelial cell surface positioning in Dab2-deficient embryos and embryoid bodies. Thus, the findings indicate that Dab2 is a surface positioning gene and suggest a novel mechanism of epithelial cell surface targeting.

Assay of mucins in human tear fluid

Mucin genes, both secreted (MUC2, MUC5AC, MUC5B, MUC7) and membrane associated (MUC1, MUC4, MUC16), have been reported to be expressed by ocular surface epithelia. The purpose of this study was to comprehensively assay the mucin content of human tear fluid using multiple antibodies for each mucin and to develop a sensitive, semi-quantitative method for the assay of mucins in tears. Tear washes were obtained by instillation of saline onto the ocular surface, followed by collection from the inferior fornix. Tear proteins were separated in 1% agarose gels, transferred to nitrocellulose membrane by vacuum blotting and probed with multiple antibodies recognizing MUC1, MUC2, MUC4, MUC5AC, MUC5B, MUC7 and MUC16. Binding was detected using chemiluminescence, and quantity was determined by densitometry. Serial dilutions of pooled tears from normal individuals were assayed to determine the linear range of detectability. MUC1, MUC4, MUC16, MUC5AC and low levels of MUC2 were consistently detected in human tear fluid, while MUC5B and MUC7 were not. Use of several antibodies recognizing different epitopes on the same mucin confirmed these findings. The antibodies to mucins bound to serial dilutions of tears in a linear fashion (r2 > 0.9), indicating the feasibility of semi-quantitation. MUC5AC in tear fluid had an increased electrophoretic mobility compared to MUC5AC isolated from conjunctival tissue. This study provides clear evidence that the mucin component of tears is a mixture of secreted and shed membrane-associated mucins, and for the first time demonstrates MUC16 in tear fluid. Immunoblots of tears using agarose gel electrophoresis and chemiluminescence detection provide a semi-quantitative assay for mucin protein that will be useful for comparisons with tears from diseased eyes or after pharmacological intervention.

MUC1 induced by Epstein-Barr virus latent membrane protein 1 causes dissociation of the cell-matrix interaction and cellular invasiveness via STAT signaling

Disruption of cellular adhesion is an essential pathobiologic step leading to tumor dissemination. Mucin 1 (MUC1) is a mucinous glycoprotein expressed at the surfaces of epithelial cells in many tissues and their carcinomas. MUC1 plays crucial roles in tumor invasion and metastasis, especially in opposing cell adhesion. We have shown that virus infection, specifically by the human tumor virus Epstein-Barr virus (EBV) induces a spectrum of cellular invasiveness and metastasis factors. Here we show that expression of MUC1 is increased in diverse latently EBV-infected cell lines that express latent membrane protein 1 (LMP1), the main viral oncoprotein, and that the level of MUC1 was suppressed by expression of a dominant-negative mutant of LMP1. Expression of LMP1 in EBV-negative nasopharyngeal cell lines induces expression of MUC1 through activation of the MUC1 promoter via binding of STAT1 and STAT3. Finally, LMP1 reduces cell adhesion ability, which is restored by inhibition of MUC1 expression with MUC1 small interfering RNA (siRNA). In addition, LMP1 increases cell invasiveness, which is suppressed by MUC1 siRNA. Thus, LMP1 induces MUC1, a factor important in an early step of detachment and release of tumor cells, which along with induction of other invasiveness and angiogenic factors may combine to act in a complex sequential process that culminates in metastasis of EBV-infected tumor cells.

The cytoplasmic expression of MUC1 in papillary thyroid carcinoma of different histological variants and its correlation with cyclin D1 overexpression

This study addressed the immunohistochemical expression of MUC1 in papillary thyroid carcinoma (PTC) of different histotypes, sizes, and morphological features of aggressiveness, and its correlation with the overexpression of cyclin D1, a target molecule of the Wnt pathway. MUC1 expression was examined in a total of 209 PTCs. Cytoplasmic MUC1 expression was elevated in the tall, columnar cell and oncocytic variants (100%), Warthin-like (78%), and conventional PTCs (61%), and in papillary microcarcinoma (PMC) with the conventional growth pattern (52%). On the contrary, it was low in the follicular variant (27%) of PTC and PMCs with follicular architecture (13%). Cytoplasmic MUC1 accumulation did not associate with any clinicopathological features except peritumoral lymphoid infiltration in PTCs and in PMCs with the conventional growth pattern. MUC1 staining correlated with cyclin D1 overexpression in conventional PTCs and PMCs and PMCs with follicular architecture. The results demonstrate that MUC1 expression varies broadly in different histological variants of PTC, being the lowest in tumors with follicular structure. In general, it does not prove to be a prognosticator of PTC aggressiveness. A high correlation between MUC1 and cyclin D1 implies MUC1 involvement in the Wnt cascade functioning in a large subset of human PTCs and PMCs.

Circulating KL-6/MUC1 mucin carrying sialyl Lewisa oligosaccharide is an independent prognostic factor in patients with lung adenocarcinoma

MUC1 mucin is frequently observed in adenocarcinomas, and its association with metastasis has been postulated through the interaction between sialyl Lewis oligosaccharides present on this glycoprotein and selectins. Levels of soluble MUC1 recognized by anti-KL-6 monoclonal antibody were also frequently elevated in the sera of lung adenocarcinoma patients. The aim of this study was to demonstrate the presence of KL-6/MUC1 carrying sialyl Lewis(a) oligosaccharide, designated as SLAK, and subsequently evaluate the clinical significance of circulating SLAK in patients with lung adenocarcinoma. We developed a sandwich ELISA system using anti-sialyl Lewis(a) and anti-KL-6 antibodies to detect SLAK, and also measured circulating SLAK levels in 97 healthy controls and 103 patients with lung adenocarcinoma. Circulating SLAK levels were measured in the sera taken before treatment and then were evaluated to clarify whether such levels were related to the clinical outcomes. Levels of circulating SLAK were significantly higher in lung adenocarcinoma patients than in healthy subjects, and a higher serum SLAK level was correlated with the presence of distant metastasis. The overall survival rate for patients with high serum SLAK levels was significantly poorer than that of patients with low serum SLAK levels. The survival analysis restricted to the patients with distant metastasis also showed the same trend. In a multivariate survival analysis in lung adenocarcinoma patients, a high serum SLAK level was indicated as an independent prognostic factor. In conclusion, the circulating SLAK level at diagnosis is useful for predicting a poor prognosis in patients with lung adenocarcinoma.

Clinicopathological implications of immunohistochemically demonstrated mucin core protein expression in hepatocellular carcinoma

METHODS

We examined the expression of mucin core protein 1 (MUC1) immunohistochemically in 186 surgical specimens of histopathologically nonmucinous hepatocellular carcinoma (HCC) and compared the clinicopathological features in patients with MUC1-positive HCC (MUC1-positive group) with those in patients with MUC1-negative HCC (MUC1-negative group).

RESULTS

MUC1 immunoreactively was present in 85 of the 186 HCCs. Of the clinicopathological variables examined, the serum concentration of alpha-fetoprotein, tumor differentiation, bile duct invasion, lymph node metastasis, and cytokeratin 19 expression exhibited significant associations with MUC1 expression. Although cumulative and tumor-free survival rates were not different between the two groups, the percentage of patients with first recurrence of HCC in distant organs (distant metastasis) within 2 years after surgery was significantly higher in the MUC1-positive group than in the MUC1-negative group (P = 0.0104). The risk ratio of MUC1 positivity for this type of distant metastasis was 3.156 (95% confidence interval, 1.064-9.358).

CONCLUSIONS

In patients with MUC1-positive HCC, careful follow-up is necessary, not only for intrahepatic recurrence but also for distant metastasis, after the resection of primary HCC.

Galectin-3 interaction with Thomsen-Friedenreich disaccharide on cancer-associated MUC1 causes increased cancer cell endothelial adhesion

Patients with metastatic cancer commonly have increased serum galectin-3 concentrations, but it is not known whether this has any functional implications for cancer progression. We report that MUC1, a large transmembrane mucin protein that is overexpressed and aberrantly glycosylated in epithelial cancer, is a natural ligand for galectin-3. Recombinant galectin-3 at concentrations (0.2-1.0 microg/ml) similar to those found in the sera of patients with metastatic cancer increased adhesion of MUC1-expressing human breast (ZR-75-1) and colon (HT29-5F7) cancer cells to human umbilical vein endothelial cells (HUVEC) by 111% (111 +/- 21%, mean +/- S.D.) and 93% (93 +/- 17%), respectively. Recombinant galectin-3 also increased adhesion to HUVEC of MUC1 transfected HCA1.7+ human breast epithelial cells that express MUC1 bearing the oncofetal Thomsen-Friedenreich antigen (Galbeta1,3 GalNAc-alpha (TF)) but did not affect adhesion of MUC1-negative HCA1.7-cells. MUC1-transfected, Ras-transformed, canine kidney epithelial-like (MDE9.2+) cells, bearing MUC1 that predominantly carries sialyl-TF, only demonstrated an adhesive response to galectin-3 after sialidase pretreatment. Furthermore, galectin-3-mediated adhesion of HCA1.7+ to HUVEC was reduced by O-glycanase pretreatment of the cells to remove TF. Recombinant galectin-3 caused focal disappearance of cell surface MUC1 in HCA1.7+ cells, suggesting clustering of MUC1. Co-incubation with antibodies against E-Selectin or CD44H, but not integrin-beta1, ICAM-1 or VCAM-1, largely abolished the epithelial cell adhesion to HUVEC induced by galectin-3. Thus, galectin-3, by interacting with cancer-associated MUC1 via TF, promotes cancer cell adhesion to endothelium by revealing epithelial adhesion molecules that are otherwise concealed by MUC1. This suggests a critical role for circulating galectin-3 in cancer metastasis and highlights the functional importance of altered cell surface glycosylation in cancer progression.

Mucin gene expression in human male urogenital tract epithelia

BACKGROUND

Mucins are large, hydrophilic glycoproteins that protect wet-surfaced epithelia from pathogen invasion as well as provide lubrication. At least 17 mucin genes have been cloned to date. This study sought to determine the mucin gene expression profile of the human male urogenital tract epithelia, to determine if mucins are present in seminal fluid and to assess the effect of androgens on mucin expression.

METHODS AND RESULTS

Testis, epididymis, vas deferens, seminal vesicle, prostate, bladder, urethra and foreskin were assessed for mucin expression by RT-PCR (for 14 mucin genes) and immunohistochemistry (nine antibodies for five mucins). Epithelia of the vas deferens, prostate and urethra expressed the greatest number of mucins, each with mRNA for between 5 and 8 mucins. Except for MUC20 in epididymis, mRNA for MUC1 and MUC20, both membrane-associated mucins, was detected in all tissues analysed. By comparison, MUC6 was more restricted in expression, being primarily detected in seminal vesicle. MUC1, MUC5B and MUC6 were detected in seminal fluid samples by immunoblot analysis. Androgens had no effect on mucin expression in cultured human prostatic epithelial cells.

CONCLUSIONS

Each region of urogenital tract epithelium expressed a unique mucin gene repertoire. Secretory mucins are present in seminal fluid, and androgens do not appear to regulate mucin gene expression in prostatic epithelial cells in culture.

Rôles physiologiques des mucines dans la barrière colique

Colonic mucus is a key element of colonic barrier as it is located at the frontier between luminal microflora and colonic mucosa itself. Colonic mucus is mainly composed of high molecular weight glycoproteins called mucins that can be either secreted or membrane-linked. The expression of various colonic mucins is altered in colorectal cancers or inflammations. The aim of this review is to highlight the crucial role played by colonic mucins in the maintenance of colonic barrier integrity, both because they are part of the protective mucus layer, and because they individually exert specific functions involved in epithelial barrier, like cell growth and differentiation, immunomodulation, signal transduction or cell adhesion.

A pilot study of the liposomal MUC1 vaccine BLP25 in prostate specific antigen failures after radical prostatectomy

PURPOSE

Men with biochemical failure after radical prostatectomy have few therapeutic options other than androgen deprivation therapy. Targeted therapies in this group are appropriate because the optimal timing of the initiation of hormonal therapy in this patient population is unknown. A single institution pilot trial was performed using BLP25 liposome vaccine in hormone naïve patients with prostate specific antigen failure after radical prostatectomy to determine if prostate specific antigen progression could be halted.

MATERIALS AND METHODS

Men with biochemical failure after radical prostatectomy were enrolled. Primary end points were efficacy and safety of the MUC1 BLP25 liposomal vaccine. Changes in prostate specific antigen doubling time were also evaluated. Patients received a single intravenous dose of cyclophosphamide, followed by vaccinations with BLP25 liposome vaccine for up to 1 year. Prostate specific antigen was measured at baseline and during treatment, and prostate specific antigen doubling time was calculated for these intervals.

RESULTS

A total of 16 patients with a median age of 60 years were enrolled. All patients received cyclophosphamide and 15 of 16 completed the primary treatment period. Ten patients completed the maintenance period. After the 8-week primary treatment period 8 of 16 patients had stable or decreased prostate specific antigen. At the last on-study prostate specific antigen measurement 1 patient maintained stable prostate specific antigen but all others had progression. However, 6 of the 16 patients had greater than 50% prolongation of prostate specific antigen doubling time compared to pre-study prostate specific antigen doubling time.

CONCLUSIONS

BLP25 liposome vaccine shows promise for prolonging prostate specific antigen doubling time in hormone naïve men with biochemical failure after prostatectomy and little morbidity. This could potentially translate into the deferral of hormonal therapy. Further testing in this population of patients is warranted.

Mucin profiles in signet-ring cell carcinoma

CONTEXT

Signet-ring cell carcinoma (SRCC) is a poorly differentiated mucin-producing adenocarcinoma that may arise from many different organs, but all SRCCs share identical morphology. It is not possible to differentiate sites of origin for metastatic SRCC based on morphology alone. Mucins are high-molecular-weight glycoproteins differentially expressed in glandular epithelia and in adenocarcinomas.

OBJECTIVE

To identify mucin profiles of primary and metastatic SRCCs using immunohistochemistry to determine whether mucin staining could help distinguish sites of origin.

DESIGN

Forty-seven SRCCs, including 38 primary (21 stomach, 11 colorectum, and 6 breast) and 9 metastases from these primary sites were retrieved from archival files. Consecutive tissue sections were immunostained with monoclonal antibodies against MUC1, MUC2, MUC4, MUC5AC (MUC5), and MUC6 on separate slides. Cytoplasmic staining was scored based on proportion of positive tumor cells as follows: 0+ (<5%), 1+ (5%-25%), 2+ (26%-50%), and 3+ (>50%). Mucin profiles were recorded as MUC+, MUCv, and MUC- for consistent, variable, and negative expression, respectively.

RESULTS

The mucin profiles for gastric, colorectum, and breast SRCCs are MUC1.2.4.5.6v, MUC2.4+/MUC5v/ MUC1.6-, and MUC1+/MUC2.5.6v/MUC4-, respectively. Mucin profiles of metastatic cases shared profiles with their respective primaries.

CONCLUSIONS

Signet-ring cell carcinomas of the stomach, colorectum, and breast have distinct mucin expression patterns that are maintained in metastases. Mucin profiling may be useful to identify the origin of a metastatic SRCC of unknown primary.

Vaccination with BLP25 liposome vaccine to treat non-small cell lung and prostate cancers

The identification of tumor-associated/-specific antigens and an increased understanding of the ways in which antigens are processed and presented has led to a revived interest in cancer vaccines as a therapeutic strategy. BLP25 liposome (L-BLP25) vaccine is a cancer vaccine that targets the exposed core peptide of the MUC1 tumor-associated antigen. Studies in advanced-stage non-small cell lung cancer demonstrate that L-BLP25 vaccine has the potential to extend the survival of patients with Stage IIIB locoregional non-small cell lung cancer and maintain quality of life for longer. L-BLP25 vaccine also shows promise for prostate cancer patients, having the potential to prolong prostate-specific antigen doubling time in men with biochemical failure post prostatectomy. These clinically meaningful results with a relatively nontoxic therapeutic vaccine are very encouraging and suggest potential for L-BLP25 to fulfill an unmet medical need.

Progesterone receptor isoforms A and B differentially regulate MUC1 expression in uterine epithelial cells

MUC1 expression responds differently to changes in progesterone (P) levels in mouse vs. human uterine epithelium. Two isoforms of progesterone receptor, PRA and PRB, mediate the physiological effects of P. Using transient transfection of a human uterine epithelial cell line, HEC-1A, we showed that liganded PRB stimulated MUC1 gene activity. PRA alone had little effect on MUC1 promoter activity, but antagonized the PRB-mediated stimulation. The region from 523 to 570 bp upstream of the transcriptional start site was shown to be required for the P response. Mutation of two potential P-responsive element (PRE) half-sites in this region partially inhibited the PRB-mediated response, and one PRE half-site disrupted binding of both PRB and PRA to a consensus PRE in an EMSA. These along with other studies indicated that multiple cis elements in the -523- to -570-bp region cooperate to mediate P responsiveness, and that PR interaction with other transcription factors in this region is likely. Using ovariectomized wild-type, PR knockout (PRKO), PRAKO, and PRBKO mice, P antagonism of estrogen-stimulated Muc1 protein and mRNA expression was shown to be dependent on PRA. In summary, these data show that liganded PRB stimulates MUC1 expression in human uterine epithelial cells, whereas liganded PRA antagonizes MUC1 expression in both human and mouse uterine epithelial cells. The differential MUC1 response to P in these two species may be due to dissimilar expression of the two PR isoforms in the uterine epithelium.

Expression of aberrantly glycosylated tumor mucin-1 on human DC after transduction with a fiber-modified adenoviral vector

BACKGROUND

DC-presenting tumor Ag are currently being developed to be used as a vaccine in human cancer immunotherapy. To increase chances for successful therapy it is important to deliver full-length tumor Ag instead of loading single peptides.

METHODS

In this study we used a fiber-modified adenoviral vector (rAd5F35) containing full-length tumor Ag cDNA to transduce human monocyte (Mo)-derived DC in vitro. Cells were efficiently transduced and survived for at least 3 days after adenoviral transduction. Phenotype and function after maturation of Mo-DC were not impaired by infection with adenovirus particles. Expression of the tumor-associated Ag mucin-1 (MUC1) was detected using MAb defining different MUC1 glycoforms.

RESULTS

Non-transduced mature Mo-DC express endogenous MUC1 with normal glycosylation. After transduction with the rAd5F35-MUC1 adenoviral vector, Mo-DC also expressed MUC1 with tumor-associated glycosylation (Tn and T glycoforms), although no changes in mRNA levels of relevant glycosyltransferases could be demonstrated.

DISCUSSION

The presence of aberrantly glycosylated MUC1 may influence Ag presentation of the tumor glycoforms of MUC1 to immune cells, affecting tumor cell killing. These findings could be highly relevant to developing strategies for cancer immunotherapy based on DC vaccines using MUC1 as tumor Ag.

Transduction with a fiber-modified adenoviral vector is superior to non-viral nucleofection for expressing tumor-associated Ag mucin-1 in human DC

BACKGROUND

DC-presenting tumor Ag are currently being developed to be used as a vaccine in human cancer immunotherapy. To increase the chances for successful therapy it is important to deliver full-length tumor Ag instead of loading single peptides. Methodologically, several recombinant DNA delivery techniques have been used.

METHODS

In this study we compared nucleofection, an optimized form of electroporation, and adenoviral transduction regarding their efficiency to transduce human monocyte-derived (Mo-) DC in vitro. Expression of the tumor-associated Ag mucin-1 (MUC1) after adenoviral transduction (rAd5Fib35-MUC1) was determined using two MAb.

RESULTS

We showed that the viability of cells and percentage of green fluorescent protein (GFP)-positive cells after transduction with a fiber-modified adenoviral vector (rAd5F35-GFP) was much higher than after nucleofection. Furthermore, phenotype and function of DC were not impaired by infection with adenovirus particles. Cells matured normally; up-regulation of CD40, CD80, CD83, CD86 and HLA-DR was not affected by adenoviral transduction. The capacity to stimulate naive T-cell proliferation was preserved and no change in IL-10 production was observed. Production of IL-12 increased up to 500-fold upon adenoviral transduction, considered to contribute positively to an anti-tumor immune response. Non-transduced mature DC expressed low levels of endogenous MUC1. After transduction with the rAd5F35-MUC1 adenoviral vector, a 100-fold increase in MUC1 expression by DC was observed.

DISCUSSION

The use of the fiber-modified adenoviral vector presented here may therefore be favorable compared with non-viral gene delivery systems for DC that will be used in cancer immunotherapy.

Low podoplanin expression in pretreatment biopsy material predicts poor prognosis in advanced-stage squamous cell carcinoma of the uterine cervix treated by primary radiation

Lymphatic invasion and nodal metastasis are predictors of poor outcome in cervix carcinoma. We have recently found that low podoplanin immunoreactivity in cervix carcinoma correlated with the presence of lymphatic invasion and nodal metastasis. In the current study, we examined whether podoplanin expression in pretreatment cervical biopsies can predict the presence lymphatic invasion, nodal metastasis, and outcome in advanced-stage tumors treated by nonsurgical means. Podoplanin expression was analyzed by immunohistochemistry in 48 cervical biopsies and corresponding hysterectomy specimens of early-stage invasive squamous cell carcinoma and in 74 pretreatment biopsies from advanced-stage tumors treated with primary radiation. We found a highly significant correlation between podoplanin expression obtained in biopsy and corresponding hysterectomy materials (r = 0.8962, P < 0.0001). Low podoplanin expression showed a significant correlation with lymphatic invasion (P < 0.0001) and nodal metastasis (P = 0.0058). Low podoplanin expression in pretreatment biopsy material showed a significant correlation with poor disease-free (P = 0.0009) and overall (P = 0.0002) survival in advanced-stage tumors. Our results suggest that in advanced-stage cervix carcinomas treated by radiation, when traditional prognostic indicators are not available and treatment decisions are based on biopsy material and clinical staging parameters, examination of podoplanin expression in pretreatment biopsy material may be a useful marker to predict lymphatic metastasis and patient outcome. Prospective studies involving larger numbers of patients are needed to further evaluate the clinical utility of examination of podoplanin expression in patients with cervix carcinoma.

Anti-tumor effect of the anti-KL-6/MUC1 monoclonal antibody through exposure of surface molecules by MUC1 capping

Human polymorphic epithelial mucin (MUC1) is a heavily glycosylated large protein that is frequently overexpressed on the surface of many human adenocarcinomas. Studies using monoclonal antibodies (mAb) identified MUC1 as a tumor-associated antigen that has been intensely studied as a target for cancer immunotherapy. We previously identified a mouse IgG(1) mAb that recognizes a sialylated sugar chain, designated as KL-6, classified in 'Cluster 9 (MUC1)'. Using the anti-KL-6 mAb, we investigated antitumor effects of anti-MUC1 mAb on breast cancer cell lines expressing MUC1 abundantly. We showed that anti-KL-6 mAb induced capping of MUC1 and facilitated E-cadherin-mediated cell-cell interaction in the breast cancer cell lines YMB-S and ZR-75-1S, which proliferate in suspension culture without aggregation. Moreover, anti-KL-6 mAb enhanced the cytotoxic activity of lymphokine-activated killer cells. These results indicate that the capping of MUC1 restores cell surface proteins, such as adhesion molecules and tumor antigens, to work in cell-cell interactions, leading to inhibition of tumor proliferation due to cell-cell adhesion and increased accessibility to effector cells that are needed to kill tumor cells.

Microplitis demolitor bracovirus inhibits phagocytosis by hemocytes from Pseudoplusia includens

The braconid wasp Microplitis demolitor carries Microplitis demolitor bracovirus (MdBV) and parasitizes the larval stage of several noctuid moths. A key function of MdBV in parasitism is suppression of the host's cellular immune response. Prior studies in the host Pseudoplusia includens indicated that MdBV blocks encapsulation by preventing two types of hemocytes, plasmatocytes and granulocytes, from adhering to foreign targets. The other main immune response mediated by insect hemocytes is phagocytosis. The goal of this study was to determine which hemocyte types were phagocytic in P. includens and to assess whether MdBV infection affects this defense response. Using the bacterium Escherichia coli and inert polystyrene beads as targets, our results indicated that the professional phagocyte in P. includens is granulocytes. The phagocytic responses of granulocytes were very similar to those of High Five cells that prior studies have suggested are a granulocyte-like cell line. MdBV infection dose-dependently disrupted phagocytosis in both cell types by inhibiting adhesion of targets to the cell surface. The MdBV glc1.8 gene encodes a cell surface glycoprotein that had previously been implicated in disruption of adhesion and encapsulation responses by immune cells. Knockdown of glc1.8 expression by RNA interference (RNAi) during the current study rescued the ability of MdBV-infected High Five cells to phagocytize targets. Collectively, these results indicate that glc1.8 is a key virulence determinant in disruption of both adhesion and phagocytosis by insect immune cells.

Recycling of MUC1 is dependent on its palmitoylation

MUC1 is a mucin-like transmembrane protein expressed on the apical surface of epithelia, where it protects the cell surface. The cytoplasmic domain has numerous sites for phosphorylation and docking of proteins involved in signal transduction. In a previous study, we showed that the cytoplasmic YXXphi motif Y20HPM and the tyrosine-phosphorylated Y60TNP motif are required for MUC1 clathrin-mediated endocytosis through binding AP-2 and Grb2, respectively (Kinlough, C. L., Poland, P. A., Bruns, J. B., Harkleroad, K. L., and Hughey, R. P. (2004) J. Biol. Chem. 279, 53071-53077). Palmitoylation of transmembrane proteins can affect their membrane trafficking, and the MUC1 sequence CQC3RRK at the boundary of the transmembrane and cytoplasmic domains mimics reported site(s) of S-palmitoylation. [3H]Palmitate labeling of Chinese hamster ovary cells expressing MUC1 with mutations in CQC3RRK revealed that MUC1 is dually palmitoylated at the CQC motif independent of RRK. Lack of palmitoylation did not affect the cold detergent solubility profile of a chimera (Tac ectodomain and MUC1 transmembrane and cytoplasmic domains), the rate of chimera delivery to the cell surface, or its half-life. Calculation of rate constants for membrane trafficking of wild-type and mutant Tac-MUC1 indicated that the lack of palmitoylation blocked recycling, but not endocytosis, and caused the chimera to accumulate in a EGFP-Rab11-positive endosomal compartment. Mutations CQC/AQA and Y20N inhibited Tac-MUC1 co-immunoprecipitation with AP-1, although mutant Y20N had reduced rates of both endocytosis and recycling, but a normal subcellular distribution. The double mutant chimera AQA+Y20N had reduced endocytosis and recycling rates and accumulated in EGFP-Rab11-positive endosomes, indicating that palmitoylation is the dominant feature modulating MUC1 recycling from endosomes back to the plasma membrane.

MUC1 plays a role in tumor maintenance in aggressive thyroid carcinomas

BACKGROUND

We recently identified MUC1 as a target driving selection for 1q21 amplification and validated it as an independent marker of aggressive behavior in thyroid cancer (TC). The aims of this study were to determine whether TC cell lines retain MUC1 expression patterns that are seen in primary tumors, assess the role of MUC1 in tumor maintenance, and develop a virally delivered anti-MUC1 RNA interference (RNAi) that is effective in decreasing MUC1 expression in vitro.

METHODS

Fifteen TC cell lines were screened for MUC1 protein expression. Cell lines with varying MUC1 protein levels were treated with anti-MUC1 monoclonal antibody to assess cell viability. A recombinant retroviral short hairpin RNAi delivery system against MUC1 was developed. Efficacy and optimal dosing of short hairpin RNA against MUC1 was determined.

RESULTS

MUC1 expression patterns in TC cell lines were found to be similar to that seen in primary tumors. Treatment with anti-MUC1 antibody resulted in a significant decrease in cell viability in MUC1 over-expressing cell lines. MUC1-779 RNAi construct showed excellent infection efficiency and reproducible silencing.

CONCLUSION

These data offer functional evidence that implicates MUC1 over-expression as a key molecular event in the pathogenesis of aggressive TC. Retrovirally delivered anti-MUC1 RNAi is effective in silencing MUC1 and merits further investigation to establish therapeutic efficacy and safety in anticipation of potential clinical application.

MUC1, MUC2, MUC4, MUC5AC and MUC6 expression in the progression of prostate cancer

Molecular changes are vital for the development of prognostic markers and therapeutic modalities of prostate cancer (CaP). There is growing interest in mucins as treatment targets in human malignancies, including CaP. The role of their expression in the progression of CaP is however unclear. We examined the expressions MUC1, MUC2, MUC4, MUC5AC and MUC6 in CaP tissues using tissue microarrays (TMAs) to look for tumor-associated antigens (TAAs) for targeted therapy. In this study, 120 paraffin-embedded specimens were selected from patients who underwent radical retro-pubic prostatectomy (RRP) or trans-urethral-resection of the prostate (TURP) for primary, untreated CaP and 10 matched lymph node metastases. A series of MUC monoclonal antibodies (mAbs) was used on TMAs by standard immunohistochemistry. Our results indicate that the over-expression of MUC1 was detected in 58% of primary CaP tissues and 90% of lymph node metastases but not in normal prostate or benign tissues, while the expression of MUC2, MUC4, MUC5AC and MUC6 was found to be negative in both normal and cancer tissues. Of the MUC1 positive tumors 86% were Gleason grade 7 or higher. Over-expression of MUC1 was found in late stage CaP while MUC2, 4, 5AC and 6 were negative in CaP. MUC1 is a TAA that is highly related to tumor progression in CaP patients. This antigen is ideal for targeted therapy to control micrometastases and hormone refractory disease but additional studies are necessary to assess its usefulness in patient biopsies and CaP bone metastases before clinical trial.

Regulation of mucin expression: mechanistic aspects and implications for cancer and inflammatory diseases

Mucins are large multifunctional glycoproteins whose primary functions are to protect and lubricate the surfaces of epithelial tissues lining ducts and lumens within the human body. Several lines of evidence also support the involvement of mucins in more complex biological processes such as epithelial cell renewal and differentiation, cell signaling, and cell adhesion. Recent studies have uncovered the role of select mucins in the pathogenesis of cancer, underscoring the importance of a detailed knowledge about mucin biology. Under normal physiological conditions, the production of mucins is optimally maintained by a host of elaborate and coordinated regulatory mechanisms, thereby affording a well-defined pattern of tissue-, time-, and developmental state-specific distribution. However, mucin homeostasis may be disrupted by the action of environmental and/or intrinsic factors that affect cellular integrity. This results in an altered cell behavior that often culminates into a variety of pathological conditions. Deregulated mucin production has indeed been associated with numerous types of cancers and inflammatory disorders. It is, therefore, crucial to comprehend the underlying basis of molecular mechanisms controlling mucin production in order to design and implement adequate therapeutic strategies for combating these diseases. Herein, we discuss some physiologically relevant regulatory aspects of mucin production, with a particular emphasis on aberrations that pertain to pathological situations. Our views of the achievements, the conceptual and technical limitations, as well as the future challenges associated with studies of mucin regulation are exposed.