Is episialin/MUC1 involved in breast cancer progression?

Regional Conjunctival Differences in Glycocalyx Mucin Expression in Dry Eye and Normal Subjects

Purpose

To compare regional conjunctival expression of membrane-associated mucins (MAMs) MUC1, MUC4, and MUC16 in normal and dry eye (DE) subjects.

Methods

Adults with and without signs and symptoms of DE were recruited. Impression cytology was performed to collect MAMs from four bulbar and upper eyelid palpebral conjunctival regions of both eyes. After protein extraction, samples from both eyes of a single subject were pooled by region, and expression was analyzed using a capillary electrophoresis nano-immunoassay system. The chemiluminescence intensity of each antigen binding signal was calculated after normalization to the total protein amount. Statistical analyses were conducted using GraphPad Prime 9.

Results

Samples from thirteen to sixteen DE and seven to eleven normal subjects were analyzed. In normal samples, MUC1 expression from the nasal bulbar conjunctiva was significantly greater than superior (P = 0.004) and inferior (P = 0.005). In DE samples, MUC1 expression was highest superiorly. Significant differences in MUC4 and MUC16 expression were not seen in normal samples. MUC4 and MUC16 expression was upregulated superiorly (P < 0.0001) and inferiorly (P < 0.0001) in DE compared with those regions in normal samples.

Conclusions

Although MAMs form a hydrophilic barrier called the glycocalyx, each mucin may have unique functions that are currently unexplored. All MAMs were expressed in the upper palpebral conjunctiva. Increased MUC1 expression nasally in healthy subjects suggests a functional need for increased protection. When comparing DE with normal eyes, upregulation of MUC1 superiorly, and in both MUC4 and MUC16 both superiorly and inferiorly, may indicate a need to decrease eyelid friction during blinking, especially in DE.

Molecular Pathology of Micropapillary Carcinomas: Is Characteristic Morphology Related to Molecular Mechanisms?

Micropapillary carcinoma is an entity defined histologically in many organs. It is associated with lymph node metastasis and poor prognosis. The main mechanism for its histopathologic appearance is reverse polarization. Although the studies on this subject are limited, carcinomas with micropapillary morphology observed in different organs are examined by immunohistochemical and molecular methods. Differences are shown in these tumors compared with conventional carcinomas regarding the rate of somatic mutations, mRNA and miRNA expressions, and protein expression levels. TP53 , PIK3CA , TERT , KRAS , EGFR , MYC , FGFR1 , BRAF , AKT1 , HER2/ERBB2 , CCND1 , and APC mutations, which genes frequently detected in solid tumors, have also been detected in invasive micropapillary carcinoma (IMPC) in various organs. 6q chromosome loss, DNAH9 , FOXO3 , SEC. 63 , and FMN2 gene mutations associated with cell polarity or cell structure and skeleton have also been detected in IMPCs. Among the proteins that affect cell polarity, RAC1, placoglobin, as well as CLDNs, LIN7A, ZEB1, CLDN1, DLG1, CDH1 (E-cadherin), OCLN, AFDN/AF6, ZEB1, SNAI2, ITGA1 (integrin alpha 1), ITGB1 (integrin beta 1), RHOA, Jagged-1 (JAG1) mRNAs differentially express between IMPC and conventional carcinomas. Prediction of prognosis and targeted therapy may benefit from the understanding of molecular mechanisms of micropapillary morphology. This review describes the molecular pathologic mechanisms underlying the micropapillary changes of cancers in various organs in a cell polarity-related dimension.

Effect of an alkyl spacer on the morphology and internalization of MUC1 aptamer-naphthalimide amphiphiles for targeting and imaging triple negative breast cancer cells

Despite decades of research, there are few targeted treatment options available for triple negative breast cancer (TNBC), leaving chemotherapy, and radiation treatment regimes with poor response and high toxicity. Herein aptamer-amphiphiles were synthesized which selectively bind to the mucin-1 (MUC1) glycoprotein that is overexpressed in TNBC cells. These amphiphiles have a fluorescent tail (1,8-naphthalimide or 4-nitro-1,8-naphthalimide) which enables self-assembly of the amphiphiles and allows for easy visualization without the requirement for further conjugation of a fluorophore. Interestingly, the length of the alkyl spacer (C4 or C12) between the aptamer and tail was shown to influence the morphology of the self-assembled structure, and thus its ability to internalize into the TNBC cells. While both the MUC1 aptamer-C4-napthalimide spherical micelles and the MUC1 aptamer-C12-napthalimide long cylindrical micelles showed internalization into MDA-MB-468 TNBC cells but not the noncancerous MCF-10A breast cells, the cylindrical micelles showed greatly enhanced internalization into the MDA-MB-468 cells. Similar patterns of enhanced binding and internalization were observed between the MUC1 aptamer-C12-napthalimide cylindrical micelles and SUM159 and MDA-MB-231 TNBC cells. The MUC1 aptamer cylindrical micelles were not toxic to the cells, and when used to deliver doxorubicin to the TNBC cells, were shown to be as cytotoxic as free doxorubicin. Moreover, a pharmacokinetic study in mice showed a prolonged systemic circulation time of the MUC1 aptamer cylindrical micelles. There was a 4.6-fold increase in the elimination half-life of the aptamer cylindrical micelles, and their clearance decreased 10-fold compared to the MUC1 aptamer spherical micelles. Thus, the MUC1 aptamer-C12-napthalimide nanofibers represent a promising vehicle that could be used for easy visualization and targeted delivery of therapeutic loads to TNBC cells.

Breast cancer cutaneous metastases are associated to uMUC1 and sialyl Lewis x and to highly malignant primary tumors

Breast cancer spreading to different organs have been related to different molecules and mechanisms, but cutaneous metastasis remains unexplored. Increasing evidence showed that MUC1 and some of its carbohydrate associated antigens may be implicated in breast cancer metastasis. In this study we analyzed these tumor markers in order to identify breast cancer cutaneous metastatic profiles. A cohort of 26 primary tumors from breast cancer patients with cutaneous metastases were included; also, cutaneous and lymphatic node metastatic samples and primary tumors from breast cancer patients without metastases were analysed. Immunohistochemical (IHC) studies demonstrated that both underglycosylated MUC1 (uMUC1) and sialyl Lewis x (sLex) to be positively associated with cutaneous metastatic primary tumors (p < 0.05). Notably, a high percentage of tumors with cutaneous metastases were characterized as triple negative and Her2+ tumors (37.5 % and 29 %, respectively). Some discordant results were found between primary tumors and their matched cutaneous metastases. To determine if MUC1 variants may be carriers of carbohydrate antigens, subcellular fractions from a cutaneous metastatic lesion were obtained, immunoprecipitated and analyzed by Western blot. We found that the isolated uMUC1 with a molecular weight of>200 kDa was also the site for binding of anti-sLex MAb; in coincidence, a high correlation of positive IHC expression of both markers was observed. Our findings confirm that breast cancer cutaneous metastases were associated to highly malignant primary tumors and sustain the hypothesis that u-MUC1 and sLe x may drive breast cancer cutaneous metastases.

MUC1 Story: Great Expectations, Disappointments and the Renaissance

In the course of studying human mucin MUC1, the attitude towards this molecule has been changing time and again. Initially, the list of presumable functions of MUC1 was restricted to protecting and lubricating epithelium. To date, it is assumed to play an important role in cell signaling as well as in all stages of oncogenesis, from malignant cell transformation to tumor dissemination. The story of MUC1 is full of hopes and disappointments. However, the scientific interest to MUC1 has never waned, and the more profoundly it has been investigated, the clearer its hidden potential turned to be disclosed. The therapeutic potential of mucin MUC1 has already been noted by various scientific groups at the early stages of research. Over forty years ago, the first insights into MUC1 functions became a strong ground for considering this molecule as potential target for anticancer therapy. Therefore, this direction of research has always been of particular interest and practical importance. More than 200 papers on MUC1 were published in 2016; the majority of them are dedicated to MUC1-related anticancer diagnostics and therapeutics. Here we review the history of MUC1 studies from the very first attempts to reveal its functions to the ongoing renaissance.

The Ocular Surface Glycocalyx and its Alteration in Dry Eye Disease: A Review

Many studies have revealed that transmembrane mucins, large glycoproteins with heavily glycosylated glycans, are essential for maintaining ocular surface epithelium lubrication and wettability. Recent reports indicate that transmembrane mucins and galectin-3, a chimera type of galectin that binds β-galactoside in the glycan, play a crucial role in maintaining the epithelial glycocalyx barrier. This review summarizes current evidence regarding the role of galectin-3, the role of the three major transmembrane mucins (i.e., MUC1, MUC4, and MUC16), in the maintenance of ocular surface wettability and transcellular barrier. Pathological mechanisms of glycocalyx barrier disruption and epithelial surface wettability decreases in dry eye disease are also summarized. Lastly, new ophthalmic drugs that target transmembrane mucin are described.

TFOS DEWS II pathophysiology report

The TFOS DEWS II Pathophysiology Subcommittee reviewed the mechanisms involved in the initiation and perpetuation of dry eye disease. Its central mechanism is evaporative water loss leading to hyperosmolar tissue damage. Research in human disease and in animal models has shown that this, either directly or by inducing inflammation, causes a loss of both epithelial and goblet cells. The consequent decrease in surface wettability leads to early tear film breakup and amplifies hyperosmolarity via a Vicious Circle. Pain in dry eye is caused by tear hyperosmolarity, loss of lubrication, inflammatory mediators and neurosensory factors, while visual symptoms arise from tear and ocular surface irregularity. Increased friction targets damage to the lids and ocular surface, resulting in characteristic punctate epithelial keratitis, superior limbic keratoconjunctivitis, filamentary keratitis, lid parallel conjunctival folds, and lid wiper epitheliopathy. Hybrid dry eye disease, with features of both aqueous deficiency and increased evaporation, is common and efforts should be made to determine the relative contribution of each form to the total picture. To this end, practical methods are needed to measure tear evaporation in the clinic, and similarly, methods are needed to measure osmolarity at the tissue level across the ocular surface, to better determine the severity of dry eye. Areas for future research include the role of genetic mechanisms in non-Sjögren syndrome dry eye, the targeting of the terminal duct in meibomian gland disease and the influence of gaze dynamics and the closed eye state on tear stability and ocular surface inflammation.

Tecemotide: an antigen-specific cancer immunotherapy

The identification of tumor-associated antigens (TAA) has made possible the development of antigen-specific cancer immunotherapies such as tecemotide. One of those is mucin 1 (MUC1), a cell membrane glycoprotein expressed on some epithelial tissues such as breast and lung. In cancer, MUC1 becomes overexpressed and aberrantly glycosylated, exposing the immunogenic tandem repeat units in the extracellular domain of MUC1. Designed to target tumor associated MUC1, tecemotide is being evaluated in Phase III clinical trials for treatment of unresectable stage IIIA/IIIB non-small cell lung cancer (NSCLC) as maintenance therapy following chemoradiotherapy. Additional Phase II studies in other indications are ongoing. This review discusses the preclinical and clinical development of tecemotide, ongoing preclinical studies of tecemotide in human MUC1 transgenic mouse models of breast and lung cancer, and the potential application of these models for optimizing the timing of chemoradiotherapy and tecemotide immunotherapy to achieve the best treatment outcome for patients.

Altered Mucins (MUC) trafficking in benign and malignant conditions

Mucins are high molecular weight O-glycoproteins that are predominantly expressed at the apical surface of epithelial cells and have wide range of functions. The functional diversity is attributed to their structure that comprises of a peptide chain with unique domains and multiple carbohydrate moieties added during posttranslational modifications. Tumor cells aberrantly overexpress mucins, and thereby promote proliferation, differentiation, motility, invasion and metastasis. Along with their aberrant expression, accumulating evidence suggest the critical role of altered subcellular localization of mucins under pathological conditions due to altered endocytic processes. The mislocalization of mucins and their interactions result in change in the density and activity of important cell membrane proteins (like, receptor tyrosine kinases) to facilitate various signaling, which help cancer cells to proliferate, survive and progress to more aggressive phenotype. In this review article, we summarize studies on mucins trafficking and provide a perspective on its importance to pathological conditions and to answer critical questions including its use for therapeutic interventions.

Micropapillary pattern and poorly differentiated clusters represent the same biological phenomenon in colorectal cancer: a proposal for a change in terminology

OBJECTIVES

Colorectal carcinomas (CRCs) with a micropapillary pattern and those showing high counts of poorly differentiated clusters (PDCs) are characterized by a higher probability to develop nodal metastases and have a worse prognosis. In light of the morphologic similarity to the micropapillary component, we aimed to verify whether PDCs also display an inverted secretory pattern.

METHODS

The immunohistochemical expression of MUC1 and E-cadherin was assessed in a cohort of CRCs with PDCs and compared with that observed in CRCs without PDCs.

RESULTS

PDCs in our cases always displayed an inverted MUC1 pattern. In addition, we found abnormal (lost or cytoplasmic) expression of E-cadherin in PDCs.

CONCLUSIONS

The altered expression of MUC1 and E-cadherin may account for the aggressive behavior and higher metastatic potential of CRCs with high PDC counts and indicate an epithelial-mesenchymal transition. Our findings suggest that regardless of the morphologic aspect, PDCs and the micropapillary component may reflect the same biological phenomenon in CRCs. Thus, we wonder whether the micropapillary areas should be considered a variant of CRCs or more objectively counted as PDCs to predict prognosis. We also believe that the term PDC better describes the biological phenomena underlying this peculiar morphologic aspect in comparison with the misnomer micropapillary.

Invasive micropapillary carcinoma: A distinct type of adenocarcinomas in the gastrointestinal tract

Invasive micropapillary carcinoma (IMPC) is a rare histological type of tumor, first described in invasive ductal breast cancer, than in malignancies in other organs such as lungs, urinary bladder, ovaries or salivary glands. Recent literature data shows that this histological lesion has also been found in cancers of the gastrointestinal system. The micropapillary components are clusters of neoplastic cells that closely adhere to each other and are located in distinct empty spaces. Moreover, clusters of neoplastic cells do not have a fibrous-vascular core. The IMPC cells show reverse polarity resulting in typical ‘’inside-out’’ structures that determines secretary properties, disturbs adhesion and conditions grade of malignancy in gastrointestinal (GI) tract. Invasive micropapillary carcinoma in this location is associated with metastases to local lymph nodes and lymphovascular invasion. IMPC can be a prognostic factor for patients with cancers of the stomach, pancreas and with colorectal cancer since it is related with disease-free and overall survival. The purpose of this review is to present the characterization of invasive micropapillary carcinoma in colon, rectum, stomach and others site of GI tract, and to determine the immunohistological indentification of IMPC in those localization.

Regulation of human corneal epithelial mucins by rebamipide

PURPOSE

Membrane-associated mucins (MAMs) play important roles in barrier function and tear stability, and their expression on the ocular surface is altered in dry eye disease. Rebamipide is a mucin secretagogue that promotes the production of mucin-like glycoproteins in human corneal epithelial (HCE) cells. However, the expression of MAMs on the corneal epithelia (MUC1, MUC4, MUC16), which is induced by rebamipide, is poorly understood. In this study, we investigated the effect of rebamipide on the regulation of MAM expression in HCE cells.

MATERIALS AND METHODS

MUC16, Ki67 and PCNA expression levels in HCE cells isolated at confluence and at 24 hours after confluence were examined by Western blotting to assess cell proliferation. HCE cells isolated at 24 hours after confluence were cultured in medium supplemented with 1-10 µM rebamipide or 0.3-30 nM of epidermal growth factor (EGF). Real-time PCR (RT-PCR) and Western blot analysis of MAMs were performed to evaluate the effect of rebamipide. Western blot analysis of cells treated with an EGF receptor inhibitor (AG1478) or MEK1/2 inhibitor (U0126) was performed to reveal the relationship between EGF receptor activation and rebamipide-induced MAM expression.

RESULTS

HCE cells isolated at 24 hours after confluence had lower cell proliferation activity and increased MUC16 expression compared with cells isolated at confluence. RT-PCR and Western blot analysis revealed that rebamipide increased MAM gene expression for 2 hours and protein expression for 24 hours in HCE cells. EGF inhibitor treatment led to reduced levels of all three MAMs that are normally induced by rebamipide, whereas EGF induced the expression of all three MAMs.

CONCLUSIONS

We suggested that rebamipide increased MUC1, MUC4 and MUC16 expression levels through signals involved in EGF receptor activation in the human corneal epithelia. These data suggest that rebamipide may improve subjective symptoms of dry eye disease by upregulating MAM expression.

The MUC1 Ectodomain: A Novel and Efficient Target for Gold Nanoparticle Clustering and Vapor Nanobubble Generation

MUC1 is a large, heavily glycosylated transmembrane glycoprotein that is proposed to create a protective microenvironment in many adenocarcinomas. Here we compare MUC1 and the well studied cell surface receptor target, EGFR, as gold nanoparticle (AuNP) targets and their subsequent vapor nanobubble generation efficacy in the human epithelial cell line, HES. Although EGFR and MUC1 were both highly expressed in these cells, TEM and confocal images revealed MUC1 as a superior target for nanoparticle intracellular accumulation and clustering. The MUC1-targeted AuNP intracellular clusters also generated significantly larger vapor nanobubbles. Our results demonstrate the promising opportunities MUC1 offers to improve the efficacy of targeted nanoparticle based approaches.

Membrane-tethered mucins have multiple functions on the ocular surface

Membrane-tethered mucins are large glycoproteins present in the glycocalyx along the apical surface of all wet-surfaced epithelia of the body, including that of the ocular surface. Originally thought to function only in epithelial surface lubrication and hydration, data now indicate that the mucins are multifunctional molecules, each having unique as well as common functions. This review summarizes current knowledge regarding the three major membrane mucins of the ocular surface, MUC1, MUC4, and MUC16. The mucins vary in their ocular surface distribution, size, structural motifs, and functions. The ectodomains of each are released into the tear film and are, thus, a component of the soluble mucins of the tear film. Both animal and in vitro models for their study are herein described, as are alterations of the mucins in ocular surface disease.

Intracellular MUC1 peptides inhibit cancer progression

PURPOSE

During cancer progression, the oncoprotein MUC1 binds beta-catenin while simultaneously inhibiting the degradation of the epidermal growth factor receptor (EGFR), resulting in enhanced transformation and metastasis. The purpose of this study was to design a peptide-based therapy that would block these intracellular protein-protein interactions as a treatment for metastatic breast cancer.

EXPERIMENTAL DESIGN

The amino acid residues responsible for these interactions lie in tandem in the cytoplasmic domain of MUC1, and we have targeted this sequence to produce a MUC1 peptide that blocks the protumorigenic functions of MUC1. We designed the MUC1 inhibitory peptide (MIP) to block the intracellular interactions between MUC1/beta-catenin and MUC1/EGFR. To allow for cellular uptake we synthesized MIP adjacent to the protein transduction domain, PTD4 (PMIP).

RESULTS

We have found that PMIP acts in a dominant-negative fashion, blocking both MUC1/beta-catenin and MUC1/EGFR interactions. In addition, PMIP induces ligand-dependent reduction of EGFR levels. These effects correspond to a significant reduction in proliferation, migration, and invasion of metastatic breast cancer cells in vitro, and inhibition of tumor growth and recurrence in an established MDA-MB-231 immunocompromised (SCID) mouse model. Importantly, PMIP also inhibits genetically driven breast cancer progression, as injection of tumor-bearing MMTV-pyV mT transgenic mice with PMIP results in tumor regression and a significant inhibition of tumor growth rate.

CONCLUSIONS

These data show that intracellular MUC1 peptides possess significant antitumor activity and have important clinical applications in the treatment of cancer.

A potent, imaging adenoviral vector driven by the cancer-selective mucin-1 promoter that targets breast cancer metastasis

PURPOSE

With breast cancer, early detection and proper staging are critical, and will often influence both the treatment regimen and the therapeutic outcome for those affected with this disease. Improvements in these areas will play a profound role in reducing mortality from breast cancer.

EXPERIMENTAL DESIGN

In this work we developed a breast cancer-targeted serotype 5 adenoviral vector, utilizing the tumor-specific mucin-1 promoter in combination with the two-step transcriptional amplification system, a system used to augment the activity of weak tissue-specific promoters.

RESULTS

We showed the strong specificity of this tumor-selective adenovirus to express the luciferase optical imaging gene, leading to diagnostic signals that enabled detection of sentinel lymph node metastasis of breast cancer. Furthermore, we were able to target hepatic metastases following systemic administration of this mucin-1 selective virus.

CONCLUSIONS

Collectively, we showed that the amplified mucin-1 promoter-driven vector is able to deliver to and selectively express a desirable transgene in metastatic lesions of breast tumors. This work has strong clinical relevance to current diagnostic staging approaches, and could add to targeted therapeutic strategies to advance the fight against breast cancer.

Antibody-cytokine fusion proteins: applications in cancer therapy

BACKGROUND

Antibody-cytokine fusion proteins consist of cytokines fused to an antibody to improve antibody-targeted cancer immunotherapy. These molecules have the capacity to enhance the tumoricidal activity of the antibodies and/or activate a secondary antitumor immune response.

OBJECTIVE

To review the strategies used to develop antibody-cytokine fusion proteins and their in vitro and in vivo properties, including preclinical and clinical studies focusing on IL-2, IL-12 and GM-CSF.

METHODS

Articles were found by searching databases such as PubMed and Clinical Trials of the US National Institutes of Health.

RESULTS/CONCLUSION

Multiple antibody-cytokine fusion proteins have demonstrated significant antitumor activity as direct therapeutics or as adjuvants of cancer vaccines in preclinical studies, paving the way for their clinical evaluation.

MUC-1 gene is associated with prostate cancer death: a 20-year follow-up of a population-based study in Sweden

Anti-adhesion mucins have proven to play an important part in the biology of several types of cancer. Therefore, we test the hypothesis that altered expression of MUC-1 is associated with prostate cancer progression. We retrieved archival tumour tissue from a population-based cohort of 195 men with localised prostate cancer (T1a-b, Nx, M0) that has been followed for up to 20 years with watchful waiting. Semi-automated, quantitative immunohistochemistry was undertaken to evaluate MUC-1 expression. We modelled prostate cancer-specific death as a function of MUC-1 levels accounting for age, Gleason grade and tumour extent, and calculated age-adjusted and multivariate adjusted hazard ratios (HR). Men that had tumours with an MUC-intensity lower or higher than normal tissue had a higher risk of dying in prostate cancer, independent of tumour extent and Gleason score (HR 5.1 and 4.5, respectively). Adjustment for Gleason grade and tumour stage did not alter the results. Men with a Gleason score ⩾7 and MUC-1 deviating from the normal had a 17 (RR=17.1 95% confidence interval=2.3–128) times higher risk to die in prostate cancer compared with men with Gleason score <7 and normal MUC-1 intensity. In summary, our data show that MUC-1 is an independent prognostic marker for prostate cancer death.

MUC1 gene overexpressed in breast cancer: structure and transcriptional activity of the MUC1 promoter and role of estrogen receptor alpha (ERalpha) in regulation of the MUC1 gene expression

BACKGROUND

The MUC1 gene encodes a mucin glycoprotein(s) which is basally expressed in most epithelial cells. In breast adenocarcinoma and a variety of epithelial tumors its transcription is dramatically upregulated. Of particular relevance to breast cancer, steroid hormones also stimulate the expression of the MUC1 gene. The MUC1 gene directs expression of several protein isoforms, which participate in many crucial cell processes. Although the MUC1 gene plays a critical role in cell physiology and pathology, little is known about its promoter organization and transcriptional regulation. The goal of this study was to provide insight into the structure and transcriptional activity of the MUC1 promoter.

RESULTS

Using TRANSFAC and TSSG soft-ware programs the transcription factor binding sites of the MUC1 promoter were analyzed and a map of transcription cis-elements was constructed. The effect of different MUC1 promoter regions on MUC1 gene expression was monitored. Different regions of the MUC1 promoter were analyzed for their ability to control expression of specific MUC1 isoforms. Differences in the expression of human MUC1 gene transfected into mouse cells (heterologous artificial system) compared to human cells (homologous natural system) were observed. The role of estrogen on MUC1 isoform expression in human breast cancer cells, MCF-7 and T47D, was also analyzed. It was shown for the first time that synthesis of MUC1/SEC is dependent on estrogen whereas expression of MUC1/TM did not demonstrate such dependence. Moreover, the estrogen receptor alpha, ERalpha, could bind in vitro estrogen responsive cis-elements, EREs, that are present in the MUC1 promoter. The potential roles of different regions of the MUC1 promoter and ER in regulation of MUC1 gene expression are discussed.

CONCLUSION

Analysis of the structure and transcriptional activity of the MUC1 promoter performed in this study helps to better understand the mechanisms controlling transcription of the MUC1 gene. The role of different regions of the MUC1 promoter in expression of the MUC1 isoforms and possible function of ERalpha in this process has been established. The data obtained in this study may help in development of molecular modalities for controlled regulation of the MUC1 gene thus contributing to progress in breast cancer gene therapy.

MUC1 is a novel regulator of ErbB1 receptor trafficking

ErbB receptors are key regulators of cell survival and growth in normal and transformed tissues. The oncogenic glycoprotein MUC1 is a binding partner and substrate for erbB1 and MUC1 expression can potentiate erbB-dependent signal transduction. After receptor activation, erbB1 is typically downregulated via an endocytic pathway that results in receptor degradation or recycling. We report here that MUC1 expression inhibits the degradation of ligand-activated erbB1. Through the use of both RNAi-mediated knock down and overexpression constructs of MUC1, we show that MUC1 expression inhibits erbB1 degradation after ligand treatment in breast epithelial cells. This MUC1-mediated protection against erbB1 degradation can increase total cellular pools of erbB1 over time. Biotinylation of surface proteins demonstrates that cell-surface associated erbB1 receptor is protected by MUC1 against ligand-induced degradation, although this is accompanied by an increase in erbB1 internalization. The MUC1-mediated protection against degradation occurs with a decrease in EGF-stimulated ubiquitination of erbB1, and an increase in erbB1 recycling. These data indicate that MUC1 expression is a potent regulator of erbB1 receptor stability upon activation and may promote transformation through the inhibition of erbB1 degradation.

MUC1 as a target antigen for cancer immunotherapy

The cancer-associated antigen MUC1 is overexpressed and modified by tumor cells in over half of all cancer cases. Despite various complexities associated with this antigen, it is well worth pursuing as a vaccine for the immunotherapy of cancer. In this review, the authors describe the discovery of MUC1 and its association with cancer, recent observations showing that the immunology of MUC1 is complicated, animal data showing that it can be a target for immune-mediated tumor rejection, and finally, preliminary clinical results to show that vaccine-based immunotherapy with MUC1 does have an impact on the therapy of cancer.

The reversed apical pattern of MUC1 expression is characteristics of invasive micropapillary carcinoma of the breast

BACKGROUND

Invasive micropapillary carcinoma (IMPC) of the breast is a special subtype of invasive ductal carcinoma (IDC), which is known to have a high potential to metastasize to the axillary lymph node. However, it is sometimes difficult to differentiate IMPC from conventional IDC showing an IMPC-like pattern due to artifact (pseudo-IMPC). In the present study, we investigated the usefulness of immunohistochemical expression of MUC1 for distinguishing IMPC from pseudo-IMPC, and analyzed several clinicopathological parameters of IMPC and pseudo-IMPC cases.

METHODS

Eighty cases showing IMPC or IMPC-like pattern were selected from our surgical files of 1,240 cases of IDC. We examined the expression of MUC1, D2-40 and CD34 by immunohistochemistry.

RESULTS

Eighty cases were classified into 9 cases (0.7%) of pure-IMPC, 31 cases (2.5%) of mixed-IMPC, and 40 cases of pseudo-IMPC, according to the expression pattern of MUC1. In pure-IMPC cases, MUC1 expression was found at the reversed apical membrane of neoplastic cell clusters, while in pseudo-IMPC, MUC1 expression was present in the whole cytoplasmic membrane and/or cytoplasm. There were no significant differences among the three groups in patient age, tumor size and nuclear grade of neoplastic cells. However, lymphatic invasion and lymph node metastasis in the pure-IMPC or mixed-IMPC cases were higher than those in pseudo-IMPC cases with statistically significant values. Pure-IMPC has a higher recurrence rate and lower overall survival compared to pseudo-IMPC [P = 0.0165(DFS) P = 0.025(OS)].

CONCLUSIONS

This study demonstrated that immunohistochemistry of MUC1 is useful for the diagnosis of IMPC. The pure-IMPC cases had higher incidences of lymphatic invasion and lymph node metastasis, and also showed a poorer prognosis.

Muc1 affects c-Src signaling in PyV MT-induced mammary tumorigenesis

MUC1 is an integral membrane mucin glycoprotein that is normally expressed on the apical surface of most simple, secretory epithelia and hematopoietic cells. Overexpression of aberrantly glycosylated MUC1 is a hallmark of many carcinomas including 90% of breast carcinomas. MUC1 has been shown to bind to c-Src tyrosine kinase in vitro, whereby c-Src phosphorylates the MUC1 cytoplasmic domain at a YEKV motif. c-Src is an extensively studied nonreceptor tyrosine kinase implicated in mammary tumorigenesis. Previously, mouse mammary tumor virus-driven polyoma middle T-antigen (MMTV-PyV MT) transgenic mice crossed onto a Muc1 null background exhibited a significant delay in tumor progression. c-Src has been shown to interact with PyV MT, and to play an integral and indispensable role in MMTV-PyV MT-induced mammary tumorigenesis. Here, we determine the effect of Muc1 expression on c-Src activation and signaling. Examination of MMTV-PyV MT glands on a wild-type or Muc1 null background demonstrates that Muc1 expression promotes c-Src signaling by influencing its association with known substrates such as the p85 subunit of phosphatidylinositol 3-kinase and beta-catenin. These findings may provide a mechanism for the delay in tumor progression that is observed in the absence of Muc1.

High-throughput protein expression analysis using tissue microarray technology of a large well-characterised series identifies biologically distinct classes of breast cancer confirming recent cDNA expression analyses

Recent studies on gene molecular profiling using cDNA microarray in a relatively small series of breast cancer have identified biologically distinct groups with apparent clinical and prognostic relevance. The validation of such new taxonomies should be confirmed on larger series of cases prior to acceptance in clinical practice. The development of tissue microarray (TMA) technology provides methodology for high-throughput concomitant analyses of multiple proteins on large numbers of archival tumour samples. In our study, we have used immunohistochemistry techniques applied to TMA preparations of 1,076 cases of invasive breast cancer to study the combined protein expression profiles of a large panel of well-characterized commercially available biomarkers related to epithelial cell lineage, differentiation, hormone and growth factor receptors and gene products known to be altered in some forms of breast cancer. Using hierarchical clustering methodology, 5 groups with distinct patterns of protein expression were identified. A sixth group of only 4 cases was also identified but deemed too small for further detailed assessment. Further analysis of these clusters was performed using multiple layer perceptron (MLP)-artificial neural network (ANN) with a back propagation algorithm to identify key biomarkers driving the membership of each group. We have identified 2 large groups by their expression of luminal epithelial cell phenotypic characteristics, hormone receptors positivity, absence of basal epithelial phenotype characteristics and lack of c-erbB-2 protein overexpression. Two additional groups were characterized by high c-erbB-2 positivity and negative or weak hormone receptors expression but showed differences in MUC1 and E-cadherin expression. The final group was characterized by strong basal epithelial characteristics, p53 positivity, absent hormone receptors and weak to low luminal epithelial cytokeratin expression. In addition, we have identified significant differences between clusters identified in this series with respect to established prognostic factors including tumour grade, size and histologic tumour type as well as differences in patient outcomes. The different protein expression profiles identified in our study confirm the biologic heterogeneity of breast cancer and demonstrate the clinical relevance of classification in this manner. These observations could form the basis of revision of existing traditional classification systems for breast cancer.

Diagnosis, treatment and prognosis of internal mammary lymph node recurrence in breast cancer patients

Recurrences in the internal mammary lymph nodes (IMLN) are very rare, despite the fact that these nodes remain untreated in most patients. The aim of this study was to assess the chance for IMLN recurrence in a large patient series and to get insight into diagnostics, treatment and prognosis of this type of recurrence. Follow-up of nearly 6000 breast cancer patients resulted in the tracing of only six patients with IMLN recurrence. IMLN recurrence was defined as breast cancer recurrence in an internal mammary lymph node without a distant metastasis before the recurrence and confirmed by cytology and/or CT-scan. The time interval between diagnosis of the primary tumor and the recurrence varied between 5 months and 8 years and 6 months. One patient showed no symptoms, the other five all had a swelling and one of them also had pain. The size of the parasternal swelling varied from 30 to 90 mm; in one patient the size was unknown. Treatment resulted in a complete remission in four patients. In five of the six patients distant metastases occurred. The time interval between IMLN recurrence and the diagnosis of distant metastasis varied between 0 and 37 months. One patient was still free of distant metastasis in the time of this study. This large population-based study confirms the almost negligible risk of clinically apparent IMLN recurrence. Considering the high percentage of positive lymph nodes in studies evaluating sentinel node biopsy of the internal mammary chain, it becomes clear that just a fraction of these becomes clinically apparent as a recurrence. In almost all patients with IMLN it is a forerunner of metastatic disease.

Pathogenesis of invasive micropapillary carcinoma: role of MUC1 glycoprotein

Invasive micropapillary carcinoma, a tumor with highly infiltrative characteristics is defined by a distinctive cleft formation around the neoplastic cell clusters which is presumably a result of the detachment of the cells from the stroma due to as yet undetermined factors. Ultrastructural examination performed on a handful of cases demonstrated an unexpected secretory activity in the stroma-facing surface of the cells. MUC1 is a glycoprotein typically expressed in the apical surface of normal epithelial cells, responsible for maintaining lumen formation. In conventional adenocarcinomas, MUC1 expression is largely intracytoplasmic, intercellular, or apical (in glandular areas). The MUC1 expression pattern was investigated by immunohistochemical staining in invasive micropapillary carcinoma of breast (n=11), pancreas (n=5), gynecologic tract (n=11) and urinary bladder (n=10). The results were contrasted with the staining pattern in conventional carcinomas of the same organs (n=202). In all invasive micropapillary carcinoma, MUC1 expression was predominantly in the stroma-facing surface of the cell clusters (basal), accentuating the outlines of the micropapillary units by forming a distinct band on this surface. In conventional carcinoma the labeling was mostly apical in areas with lumen formation and intracytoplasmic and intercellular in the poorly differentiated areas. In conclusion, in the micropapillary pattern of invasive carcinoma, the expression of MUC1, is largely limited to the basal surface of the cells in contrast to conventional carcinomas in which MUC1 is largely apical, intracytoplasmic or intercellular. This provides support for the reversal of cell orientation as an important factor of the morphogenesis and possibly the pathogenesis of invasive micropapillary carcinoma. Since MUC1 is known to have a role in lumen formation, and has an inhibitory role in the cell to stroma interaction, it is conceivable that it is a key factor in the detachment of cells from stroma allowing for the dissection of the connective tissue and easing the spread of cells.

Modulation of anti-adhesion molecule MUC-1 is associated with arctiin-induced growth inhibition in PC-3 cells

BACKGROUND

Lignans have been reported to possess anti-tumor activity in various cancer cells. However, their anticancer effects in human prostate cancer have not been well established. Here, we examine the effect of arctiin, a lignan compound, on growth regulation in prostate cancer PC-3 cells. We postulated that arctiin modulates the attachment/detachment of PC-3 cells and we investigated the role of arctiin on MUC-1 expression.

METHODS

The effect of arctiin on PC-3 cell growth was examined using an MTT assay method and cell number was calculated by means of a standard regression line. The expressions of MUC-1 and integrins alpha2, alpha5, and beta1 were detected using FACScan flow cytometric analysis. Levels of MUC-1 mRNA were determined using reverse transcriptase PCR (RT-PCR).

RESULTS

Treatment of PC-3 cells with arctiin decreased the cell number in a concentration- and time-dependent manner in serum-containing condition. Arctiin preferentially induced cell detachment, but did not have anti-proliferation or cytotoxic effects in PC-3 cells. The arctiin-induced effect was inhibited by cycloheximide, indicating that protein synthesis was required. FACScan flow cytometric analysis demonstrated that arctiin increased the expression of the anti-adhesion mucin MUC-1, but did not affect integrin expression in PC-3 cells. The arctiin-induced increase in MUC-1 protein expression was due to up-regulation of mRNA, as revealed by RT-PCR analysis.

CONCLUSIONS

Arctiin significantly induces cell detachment and decreases the cell numbers via the up-regulation of MUC-1 mRNA and protein in PC-3 cells.

Patterns of MUC1 tissue expression defined by an anti-MUC1 cytoplasmic tail monoclonal antibody in breast cancer

Our aim was to determine the pattern of expression of MUC1 mucin cytoplasmic tail (MUC1 CT) in breast carcinoma. A total of 98 invasive breast adenocarcinoma tumor samples were assayed by immunohistochemical (IHC) analysis. The pattern of reaction was classified as membrane, cytoplasmic, or mixed. Subcellular fractions were prepared after SDS-PAGE and Western blotting. The antibodies employed were anti-MUC1 CT (CT2 monoclonal antibody, MAb) and C595 MAb against the extracellular MUC1 core protein. With the CT2 MAb, IHC showed a high percentage of positive staining in 93% of specimens, with membrane staining the most common pattern observed. C595 MAb was reactive in 73% of specimens. Similar percentages of membrane and cytoplasmic staining were found, mainly in a mixed pattern. Western blotting showed different bands. With the CT2 MAb, the membrane fraction showed the most intense reaction; a strong band of reaction was detected at approximately <30 kD. With the C595 MAb, in most cases a double band at 200 kD was found. In breast epithelium, the pattern of MUC1 CT expression may constitute an indicator of MUC1 production because it does not depend on glycosylation. The pattern and extension of MUC1 CT positivity do not vary according to the histopathological subtype of the tumor.

MUC1 alters beta-catenin-dependent tumor formation and promotes cellular invasion

MUC1 is aberrantly expressed in greater than 90% of all breast carcinomas, yet its function as a tumor antigen is not fully understood. Recently, studies have shown that MUC1 interacts with beta-catenin, erbB receptors, src, GSK-3beta and protein kinase Cdelta, possibly in a complex that promotes the disassembly of adherens junctions and the invasion of cells. Here we show that the deletion of Muc1 expression from MMTV-Wnt-1 transgenic mice results in a significant increase in the time to mammary gland tumor onset. Analysis of MMTV-Wnt-1 tumors on a wild-type Muc1 background shows a tumor-specific complex formation between Muc1 and beta-catenin that can be observed in both the membrane and the cytoplasm of transformed epithelium. Analysis of primary human adenocarcinomas revealed that this MUC1/beta-catenin interaction occurs in both primary and metastatic tumors, but is dramatically increased in metastatic lesions. Addition of MUC1-cytoplasmic domain peptides to the invasive MDA-MB-468 and MDA-MB-231 cell lines increases their invasive capability, and these peptides colocalize with both beta-catenin and the focal adhesion protein vinculin, primarily at sites of membrane invasion into a collagen matrix. These data indicate a potential mechanism for MUC1 promotion of invasive tumorigenesis in the breast through the modulation of beta-catenin localization and subsequent cytoskeletal dynamics.

Androgen modulation of adhesion and antiadhesion molecules in PC-3 prostate cancer cells expressing androgen receptor

The metastatic spread of cancer cells involves a complex process of detachment via antiadhesion molecules and attachment and migration through adhesion. In the prostate, androgens are generally thought to contribute to the development and progression of prostate cancer by promoting cell proliferation and survival through poorly defined mechanisms. We have reported previously that PC-3 prostate cancer cells, which are unresponsive to androgens, show androgen-dependent detachment and ultimately apoptosis when stably transfected with a full-length human androgen receptor (AR) cDNA. We now demonstrate that treatment of these cells with 5alpha-dihydrotestosterone (DHT) for 24 or 48 h increased the expression of antiadhesion mucin MUC-1 at the cell surface as detected by flow cytometry with two independent antibodies. This increase in protein was concordant with up-regulation of MUC-1 mRNA in the AR-transfected PC-3 sublines, as determined by quantitative RT-PCR. Treatment with DHT for 48 h also down-regulated the cell surface expression of alpha2beta1-integrin but having little effect on the levels of alpha3beta1- and alpha5beta1-integrins. Androgen also decreased, in a dose-dependent manner, the adhesion of AR-transfected PC-3 cells to collagen type I, which was shown to be specifically inhibited by blocking antibody to alpha2beta1-integrin. The present data demonstrate that DHT can modulate expression of adhesion and antiadhesion molecules and suggest that this effect of androgen might contribute to prostate cancer progression.

Non-glycosylated tandem repeats of MUC1 facilitate attachment of breast tumor cells to normal human lung tissue and immobilized extracellular matrix proteins (ECM) in vitro: potential role in metastasis

MUC1 is a transmembrane glycoprotein abundantly expressed on the apical surface of human ductal epithelial cells and over entire cell surface of tumors originating from those cells. It is 300 to 500 nm long and has a rigid, rod-like structure protruding from the cell surface. MUC1 expressed by normal cells has heavily O-glycosylated tandem repeat domain while MUC1 on malignant cells is aberrantly O-glycosylated. Substantially reduced (aberrant) glycosylation of the tandem repeat region of tumor MUC1 results in uncovering of the polypeptide core. This new structural feature may play an important role in the attachment of metastasizing tumor cells to tissues at distant sites. We show that MDA-MB-231 cells attaching to the immobilized extracellular matrix proteins (ECM) are higher MUC1 expressers than those non-attaching and that the attachment is inhibited by the addition of non-glycosylated, MUC1 peptide. This 100 a.a. peptide composed of 5 tandem repeats from the tandem repeat domain mimics the forms of MUC1 found in ascites fluid of cancer patients. We also show that this synthetic form of MUC1 inhibited attachment of breast tumor cells to sections of normal human lung tissue and immobilized ECM. We did not find correlation between the expression of Tn (GalNAc-Ser/Thr) epitope and the ability of tumor cells to adhere to the immobilized ECM. These results indicate that the non-glycosylated form of MUC1 plays a role in the initial attachment of carcinoma cells to tissues at distant sites, which may facilitate establishment of metastatic foci.

Altered expression and allelic association of the hypervariable membrane mucin MUC1 in Helicobacter pylori gastritis

BACKGROUND & AIMS

Infection with Helicobacter pylori causes chronic gastritis, and this confers a risk of gastric cancer. Short alleles of the membrane-bound mucin MUC1, which has a large extracellular highly glycosylated domain and is highly polymorphic due to variation in the number of tandemly repeated (TR) 20-amino acid units, have been shown to be associated with gastric cancer. Our aim was to investigate the involvement of MUC1 in chronic gastritis and, by implication, gastric cancer.

METHODS

Immunohistochemical analysis was performed on endoscopic biopsy specimens from 95 patients. Gastritis was classified using the Sydney System, and H. pylori status was determined. MUC1 was detected with antibodies against different epitopes of the TR region and the cytoplasmic tail. Southern blot analysis of the MUC1 gene was performed on 57 Northern European patients to determine TR allele lengths.

RESULTS

With the TR antibodies, apical staining and some perinuclear staining was seen in 34 of 41 biopsy specimens classified as histologically normal and H. pylori negative. None of the 36 biopsy specimens with gastritis and current H. pylori infection showed apical staining. In contrast, the cytoplasmic tail antibody detected apical staining in both groups. Comparison of the MUC1 allele length distributions between Northern European patients with H. pylori infection and those without H. pylori gastritis showed a statistically significant difference in distribution, with shorter alleles associated with H. pylori gastritis.

CONCLUSIONS

Our results suggest that H. pylori interacts with MUC1 and that there are functional allelic differences that affect susceptibility to gastritis.

Patterns of episialin/MUC1 expression in endometrial carcinomas and prognostic relevance

AIMS

To investigate episialin/MUC1 expression in the normal, hyperplastic and neoplastic endometrium, and relate patterns of tumour MUC1 reactivity with histopathological characteristics, oestrogen and progesterone receptor (ER and PR) status, bcl-2 and p53 oncoproteins and with clinical behaviour.

METHODS AND RESULTS

We studied 42 normally cycling endometria, 45 endometrial hyperplasias of various forms, and 111 endometrial carcinomas of endometrioid and non-endometrioid cell types with specific monoclonal antibodies employing standard immunohistochemical techniques. The follow-up period ranged from 34 to 182 months with a median of 86 months. Epithelial mucin episialin/MUC1 was consistently expressed in the normal endometrium, following a cyclical pattern: "apical membrane staining" in early and mid-proliferative endometrium; "purely cytoplasmic staining" in late proliferative endometrium; and "cytoplasmic staining with intraluminal secretions" in secretory endometrium. Immunostaining patterns in simple and complex hyperplasia were similar to late proliferative endometrium, while atypical hyperplasias and endometrial carcinomas either simulated patterns of proliferative endometrium or lacked MUC1 reactivity. Membranous MUC1 positivity was statistically more frequent in endometrioid carcinomas compared with carcinomas of non-endometrioid type (P = 0.006). Cytoplasmic MUC1 positivity was significantly associated with poor prognosis, while MUC1-negative carcinomas were associated with PR expression and an improved survival (P=0.04). There was no association of MUC1 patterns with bcl-2 and p53 immunoreactivity or with other histopathological variables.

CONCLUSIONS

Episialin/MUC1 is an integral component of the normal premenopausal endometrium and is probably hormonally regulated. It is frequently expressed in endometrial hyperplasias and carcinomas. The loss of MUC1 expression from endometrial carcinomas is associated with a favourable prognosis.

Surfactant protein A expression in human normal and neoplastic breast epithelium

We studied the presence of surfactant protein A (Sp-A) immunoreactivity and messenger RNA in 62 normal and abnormal breast samples. Sections were immunostained with polyclonal anti-Sp-A antibody. The association between Sp-A immunoreactivity and histologic grade of 32 invasive ductal carcinomas was assessed by 3 pathologists who scored the intensity of Sp-A immunoreactivity times the percentage of tumor immunostained; individual scores were averaged, and the final scores were correlated with tumor grade, proliferative index, and expression of estrogen and progesterone receptors. Strong Sp-A immunoreactivity was present at the luminal surface of ductal epithelial cells in normal breast samples and in benign lesions; carcinomas displayed variable immunoreactivity, inversely proportional to the degree of differentiation. Sp-A messenger RNA was detected by reverse transcriptase-polymerase chain reaction in 3 of 3 normal breast samples and 9 of 9 carcinomas. The significance of Sp-A expression in breast epithelium requires further study; possibly it has a role in native host defense or epithelial differentiation.

Human MUC1 mucin: a potent glandular morphogen

Human MUC1 mucin is a high-molecular-weight transmembrane glycoprotein, which is apically expressed in the majority of glandular epithelia. During embryonic development, changes in the pattern of MUC1 mucin expression coincide with the onset of glandular differentiation. This mucin is also frequently overexpressed and aberrantly glycosylated in carcinomas. To investigate the potential role of MUC1 mucin in morphogenesis, a full length MUC1 cDNA was transfected into murine mammary adenocarcinoma (410.4) and Madin-Darby canine kidney (MDCK) cells. This generated four clonal cell lines. Western blotting, FACS analysis, and immunohistochemistry confirmed expression of MUC1. All four MUC1-expressing clones demonstrated altered morphogenesis when cultured in three-dimensional type I collagen gels. While parental and vector control 410.4 cells formed compact spherical structures, the MUC1-expressing clones formed complex branching structures. Similarly, while parental and vector control MDCK cells formed small circumscribed colonies with a central lumen, the MUC1-expressing clones formed elongated tubules. MUC1 expression was also associated with reduced cellular cohesion and enhanced migration on type I collagen-coated surfaces for all except one of the clones, which expressed only low levels of MUC1 on the cell surface. These results show that MUC1 expression stimulates morphogenetic changes in two distinct epithelial cell lines. Taken together with previous observations on MUC1 expression in embryonic development and carcinomas, this finding suggests that MUC1 may induce changes in tissue architecture in both normal development and cancer.

MUC1 expression in primary breast cancer: the effect of tamoxifen treatment

This was a non-randomised single institution retrospective study. Forty-six banked frozen tumour specimens were obtained from a group of patients who had undergone 3 weeks of neoadjuvant treatment with tamoxifen between biopsy and surgery. Fifty-one comparison specimens were randomly selected from a group of concomitantly treated primary breast cancer patients who did not receive neoadjuvant tamoxifen. Specimen selection was not based on prognostic factors: hormone receptor status, patient age, or menopausal status. MUC1 expression and cell cycle distribution were assessed by flow cytometry. S-phase fraction of MUC1 positive and MUC1 negative cells were compared. A lower percentage of cells expressed MUC1 following 3-week tamoxifen treatment 18.2% versus 28.5% (p = 0.03, Mann-Whitney) and lower levels of MUC1 expression were seen following tamoxifen treatment 31,519 molecules/cell versus 39,387 (p = 0.04, Mann-Whitney). MUC1 positive cells, irrespective of treatment group, had a greater proportion of cells in S-phase of the cell cycle 27.9% versus 16.8% (p = 0.0004, Mann-Whitney) and demonstrated more cases of aneuploidy 80.65% versus 42.6% (p < 0.0001). MUC1 levels in primary tumours treated neoadjunctively with 3 weeks of tamoxifen were lower than a comparison group which did not receive tamoxifen. MUC1 should be explored further as an intermediate biomarker for assessment of treatment and prognosis.

Alkyl-lysophospholipid 1-O-octadecyl-2-O-methyl- glycerophosphocholine induces invasion through episialin-mediated neutralization of E-cadherin in human mammary MCF-7 cells in vitro

1-O-octadecyl-2-O-methyl-glycerophosphocholine (ET-18-OMe) is an analogue of the naturally occurring 2-lysophosphatidylcholine belonging to the class of antitumor lipids. Previously, we demonstrated that ET-18-OMe modulates cell-cell adhesion of human breast cancer MCF-7 cells. In the present study, we tested the effect of ET-18-OMe on adhesion, invasion and localisation of episialin and E-cadherin in MCF-7/AZ cells expressing a functional E-cadherin/catenin complex. The MCF-7/6 human breast cancer cells were used as negative control since their E-cadherin/catenin complex is functional in cells grown on solid substrate but not in suspension. The function of E-cadherin, a calcium-dependent transmembrane cell-cell adhesion and signal-transducing molecule, is disturbed in invasive cancers by mutation, loss of mRNA stability, proteolytic degradation, tyrosine phosphorylation of associated proteins and large cell-associated proteoglycans or mucin-like molecules such as episialin. Episialin, also called MUC1, is an anti-adhesion molecule that by its large number of glycosylated tandem repeats can sterically hinder the adhesive properties of other glycoproteins. ET-18-OMe inhibited the E-cadherin functions of MCF-7/AZ cells as measured by inhibition of fast and slow aggregation and by the induction of collagen invasion. These effects were enhanced by MB2, an antibody against E-cadherin and blocked by monoclonal antibodies (MAbs) 214D4 or M8 against episialin. ET-18-OMe had no influence on tyrosine phosphorylation of beta-catenin and the E-cadherin/catenin complex remained intact. Transcription, translation, protein turnover and cell surface localisation of episialin were not altered. ET-18-OMe induced finger-like extensions with clustering of episialin together with E-cadherin and carcinoembryonic antigen but not with occludin. In cells in suspension, ET-18-OMe caused a shift in the flow-cytometric profile of episialin toward a lower intensity for MCF-7/AZ cells. In contrast with MCF-7/AZ cells, the adhesion-deficient and noninvasive MCF-7/6 cells showed neither morphotypic changes nor induction of aggregation nor invasion in collagen I upon treatment with ET-18-OMe. Co-localisation of episialin with E-cadherin was rarely observed. We conclude that in the human breast cancer cells MCF-7/AZ, E-cadherin and episialin are key molecular players in the regulation of promotion and suppression of cell-cell adhesion and invasion.

Transgenic MUC1 interacts with epidermal growth factor receptor and correlates with mitogen-activated protein kinase activation in the mouse mammary gland

MUC1 is a large (>400 kDa), heavily glycosylated transmembrane protein that is aberrantly expressed on greater than 90% of human breast carcinomas and subsequent metastases. The precise function of MUC1 overexpression in tumorigenesis is unknown, although various domains of MUC1 have been implicated in cell adhesion, cell signaling, and immunoregulation. Stimulation of the MDA-MB-468 breast cancer line as well as mouse mammary glands with epidermal growth factor results in the co-immunoprecipitation of MUC1 with a tyrosine-phosphorylated protein of approximately 180 kDa. We have generated transgenic lines overexpressing full-length (MMF), cytoplasmic tail deleted (DeltaCT), or tandem repeat deleted (DeltaTR)-human MUC1 under the control of the mouse mammary tumor virus promoter to further examine the role of MUC1 in signaling and tumorigenesis. Immunoprecipitation experiments revealed that full-length transgenic MUC1 physically associates with all four erbB receptors, and co-localizes with erbB1 in the lactating gland. Furthermore, we detected a sharp increase in ERK1/2 activation in MUC1 transgenic mammary glands compared with Muc1 null and wild-type animals. These results point to a novel function of increased MUC1 expression, potentiation of erbB signaling through the activation of mitogenic MAP kinase pathways.

Expression of MUC1 and MUC2 glycoproteins in laryngeal cancer

The aim of this study was to examine the expression of MUC1 and MUC2 glycoproteins in laryngeal cancer and to determine if mucin expression is related to prognosis. The study included laryngeal specimens from 57 patients comprising of 36 laryngeal carcinomas and 21 normal controls. High MUC1 expression was found in both carcinomas and normal control groups (P = 0.689, Fisher's exact test). High levels of MUC2 expression were only detected in carcinomas versus controls (P = 0.009, Fisher's exact test). Using multivariate analysis neither MUC1 nor MUC2 expression significantly related to survival. MUC1 expression however, did correlate with T stage. Advanced T stage was associated with prognosis (P = 0.001).

Altered MUC1 and MUC2 glycoprotein expression in laryngeal cancer

The purpose of this study was to determine whether mucin expression is altered in laryngeal cancer. MUC1 and MUC2 mucin expression was examined in biopsy specimens from 80 patients that comprised 23 laryngeal dysplasias, 36 laryngeal carcinomas, and 21 normal larynx control specimens. High MUC1 expression was found in all 3 groups (P = 0.689, Fisher exact test). However, significantly higher levels of MUC2 expression were detected in carcinomas compared with dysplasias and control specimens (P = 0.009, Fisher exact test). Altered MUC2 expression may be an important step in carcinogenesis in laryngeal cancer.

Establishment and characterization of a new cell line derived from a human primary breast carcinoma

A new cell line, designated HDQ-P1, was successfully established from a primary ductal infiltrating mammary carcinoma by using a 3T3 feeder layer lethally irradiated to 60 Gy. The HDQ-P1 cells have been grown in culture for over 115 passages and have a doubling time of 60 hours. Characterization of the cell line was performed. This included morphology by light and transmission electron microscopy, karyotype, growth rate, telomerase expression, tumor antigen expression, xenograft implantation into nude mice, colony formation in soft agar, TP53 sequencing, and gene copy number of C-MYC, C-ERBB-2, and C-H-RAS oncogenes. The epithelial nature of this cell line was confirmed by ultrastructural analysis, expression of cytokeratins, and epithelial membrane antigen. The HDQ-P1 cells possess an extensively rearranged and polyploid karyotype, with an average of 20 recurrent marker chromosomes. Scatchard analysis demonstrated that both primary tumor and HDQ-P1 cells were estrogen- and progesterone-receptor negative. The HDQ-P1 cells had the same expression of human telomerase reverse transcriptase as other established breast cancer cell lines such as MDA-MB-231, SK-BR-3, and MCF-7. Direct DNA sequencing showed a point mutation which yielded to a stop codon at the amino acid 213 in exon 6 of the TP53 gene. A five-fold amplification of C-MYC was observed in HDQ-P1 cells. No amplification of C-ERBB-2 and C-H-RAS genes were observed. This cell line presents unique characteristics and may prove to be a good experimental model for investigating breast cancer biology.

Immunohistochemical study of MUC1 mucin in premalignant oral lesions and oral squamous cell carcinoma: association with disease progression, mode of invasion, and lymph node metastasis

BACKGROUND

MUC1 mucin is a transmembrane, mucin-like glycoprotein encoded by the MUC1 gene. Although MUC1 expression has been identified in a variety of neoplastic tissues, to the authors' knowledge, few studies have examined MUC1 expression in premalignant and malignant oral lesions.

METHODS

A total of 36 specimens of oral epithelial dysplasia, 12 carcinoma in situ (CIS) specimens and 77 specimens of oral squamous cell carcinoma (OSCC), were examined by both light and electron microscopy using immunohistochemical staining of MUC1 mucin. Relations between staining patterns and clinicopathologic findings also were examined.

RESULTS

Distinct membrane MUC1 mucin staining patterns were identified in epithelial dysplasia (33.0%), CIS (50.0%), and OSCC (59.7%) cases. A predominantly cytoplasmic staining pattern was detected in epithelial dysplasia (5.6%), CIS (41.7%), and OSCC (32.5%) cases. Significant positive correlations were found between MUC1 mucin membranous immunoreactivity and disease progression from epithelial dysplasia to OSCC (P < 0.01), mode of tumor invasion (P < 0.02), and lymph node metastasis (P < 0.01). Furthermore, the malignant transformation of oral epithelium, tumor invasion, and tumor metastasis were associated with higher MUC1 mucin expression in the cytoplasm (P < 0.01). In addition to the usual cell surface expression, cytoplasmic expression of MUC1 mucin was confirmed by colloidal gold labeling with transmission electron microscopy.

CONCLUSIONS

The results of the current study suggest that determination of MUC1 mucin expression may be a parameter in the diagnosis of premalignant and malignant lesions arising in the oral cavity and that this expression may affect the malignant behavior of OSCC. MUC1 mucin expression may be a useful diagnostic marker for prediction of the invasive/metastatic potential of OSCC.

Heterogeneity of MUC1 expression by human breast carcinoma cell lines in vivo and in vitro

Increased expression of the epithelial mucin MUC1 has been linked to tumor aggressiveness in human breast carcinoma. Recent studies have demonstrated that overexpression of MUC1 interferes with cell-substrate and cell-cell adhesion by masking cell surface integrins and E-cadherin. Additionally, the cytoplasmic tail of MUC1 is involved in signal transduction and interactions with catenins. In the present study, we have examined the in vitro expression of MUC1 mRNA and protein in a panel of 14 human breast cancer cell lines using northern blotting, western blotting, immunocytochemistry, and flow cytometry. Considerable variability of expression was noted not only between cell lines but also within several individual lines. Many cell lines such as BT 20, KPL-1, and T47D expressed abundant MUC1 whilst others such as MDA-MB-231 and MCF-7 showed intermediate expression, and MDA-MB-435 and MDA-MB-453 expressed very low levels. Low levels of MUC1 expression were associated with decreased expression of cytokeratin and increased expression of vimentin. Additionally, 12 of the cell lines were established as xenografts in immunocompromised (SCID) mice, and MUC1 expression in both the primary tumors as well as metastases was assessed immunohistochemically. In general, in vivo expression mirrored in vitro expression, although there was reduced in vivo expression in T47D and ZR-75-1 xenografts. Although we showed no correlation between tumorigenicity or metastasis and MUC1 expression, this study will assist development of experimental models to assess the influence of MUC1 of on breast cancer progression.

Expression of MUC1 and MUC2 mucin gene products in Barrett's metaplasia, dysplasia and adenocarcinoma: an immunopathological study with clinical correlation

AIMS

Changes in the histochemical characteristics of the surface epithelial mucins is the hallmark of Barrett's metaplasia. The study investigated the pattern of expression of MUC1 and MUC2 mucin gene products in Barrett's metaplasia, dysplasia and adenocarcinoma as possible indicators of increased malignant potential.

METHODS AND RESULTS

Tissue sections from 51 patients with Barrett's intestinal metaplasia, nine with dysplasia (three indefinite) and 28 resected adenocarcinomas were stained with monoclonal antibodies to MUC1 and MUC2. The majority of the patients were men (70/88, 80%) who were treated over a period of 3 years. None of the patients with dysplasia or carcinoma were under surveillance at the time of presentation. All 51 biopsies with Barrett's metaplasia expressed MUC2 and MUC1 was consistently absent. Neither MUC1 or MUC2 were expressed in the dysplastic epithelium whether in its pure form (6/6) or when associated with carcinoma (26/28) (P < 0.005). Three biopsies which were initially classified as high-grade dysplasia expressed MUC1 and these turned out to be carcinomas on further investigations. MUC1 was also expressed in 12/28 (43%) of the adenocarcinomas and majority of these were poorly differentiated stage 3 tumours (P < 0.05). MUC2 was only positive in mucin-secreting carcinomas (4/28; 14%) irrespective of the tumour stage.

CONCLUSION

Despite the large number of patients with Barrett's metaplasia and carcinoma, very few patients presented with dysplasia, implying that Barrett's oesophagus is a silent disease in the community presenting late as carcinoma. The study has demonstrated aberrant expression of MUC2 (an intestinal mucin) in Barrett's metaplasia and this expression is lost when the cells become dysplastic. The lack of MUC1 in dysplastic epithelium and its expression in carcinoma could be utilized as a marker which could differentiate dysplasia from carcinoma in mucosal biopsies. Furthermore, expression of MUC1 in advanced stage oesophageal cancers (as in breast cancer) suggests an unfavourable prognosis.

Aberrant expression of MUC1 mucin in ductal hyperplasia and ductal carcinoma In situ of the breast

MUC1 mucin is a high molecular weight transmembrane glycoprotein expressed on the apical cell surface of normal glandular epithelia. In many human adenocarcinomas, this protein is up-regulated and/or underglycosylated, and its expression changes from apical to the entire cell membrane. It is thought that entire cell membrane expression of MUC1 reduces cell-cell and cell-extracellular matrix interactions and therefore may facilitate invasive growth and development of metastases. In this study, we determined immunohistochemically the expression of normal and underglycosylated MUC1 in normal breast tissue (n = 8) and in a spectrum of breast lesions, including usual ductal hyperplasia (n = 23), atypical ductal hyperplasia (n = 7), and ductal carcinoma in situ (DCIS) (n = 22). We used 4 monoclonal antibodies; 115D8 is directed to a glycopeptide, the other 3 to the peptide core of the molecule, of which 139H2 is not affected by the degree of glycosylation of MUC1, whereas SM3 and VU-4-H5 stain only underglycosylated forms. All cases showed apical positivity for 115D8 and 139H2. Entire cell membrane expression of fully (normal) glycosylated MUC1 was mainly found in DCIS lesions. Apical staining of SM3 was found in 38% of normal cases and 60% of the ductal lesions with no difference between the different subgroups. Apical staining of VU-4-H5 was found more often in DCIS (27%) than in normal tissue or ductal hyperplasia (3%). Membrane expression of underglycosylated MUC1 was found only in poorly differentiated DCIS. In conclusion, aberrant expression of MUC1, i.e., on the entire cell membrane and/or underglycosylated forms, can be found in ductal hyperplasia with atypia and especially in DCIS of the breast. This finding implies that these lesions with aberrant expression are at higher risk for developing subsequent invasive breast carcinoma.

Mucin expression in mucinous carcinoma and other invasive carcinomas of the breast

To investigate mucin expression in breast cancer, immunohistochemical staining was performed on 30 mucinous carcinomas and 95 non-mucinous invasive carcinomas. MUC2 expression was detected in all mucinous carcinomas, but only in 11.1% of invasive ductal carcinomas, and in none of the invasive lobular carcinomas and medullary carcinomas. MUC1 is often expressed in invasive breast carcinoma, but not in medullary carcinoma. Strong cytoplasmic staining was seen in invasive ductal carcinoma, in contrast to surface membrane staining in mucinous carcinoma and intracytoplasmic vacuole staining in invasive lobular carcinoma. CA19-9 and CA50 expression in more than 25% of tumor cells was seen in 17.2 and 16.0% of invasive ductal carcinomas, respectively, but not in mucinous carcinomas. CA125 and human gastric mucin were rarely expressed in breast cancer, irrespective of histologic type.

A cell surface mucin specifically expressed in the midgut of the malaria mosquito Anopheles gambiae

An invertebrate intestinal mucin gene, AgMuc1, was isolated from the malaria vector mosquito Anopheles gambiae. The predicted 122-residue protein consists of a central core of seven repeating TTTTVAP motifs flanked by hydrophobic N- and C-terminal domains. This structure is similar to that of mucins that coat the protozoan parasite Trypanosoma cruzi. Northern blot analysis indicated that the gene is expressed exclusively in the midgut of adult mosquitoes. A length polymorphism and in situ hybridization were used to genetically and cytogenetically map AgMuc1 to division 7A of the right arm of the second chromosome. The subcellular localization of the encoded protein in tissue culture cells was examined by using a baculovirus vector to express AgMuc1 protein tagged with the green fluorescent protein (GFP). The results indicated that this protein is found at the cell surface and that both hydrophobic domains are required for cell surface targeting. We propose that AgMuc1 is an abundant mucin-like protein that lines the surface of the midgut microvilli, potentially protecting the intestinal epithelium from the proteinase-rich environment of the gut lumen. An intriguing possibility is that, as an abundant surface protein, AgMuc1 may also interact with the malaria parasite during its invasion of the mosquito midgut.

The biological role of mucins in cellular interactions and immune regulation: prospects for cancer immunotherapy

Among the human mucins, MUC1 is unique in its cell-surface transmembrane expression and its apparent signal-transduction functions. The high expression of MUC1 on many human cancers makes it an attractive target for immunotherapy. Immunization of human cancer patients with MUC1 peptides has resulted in the generation of both anti-MUC1 antibody and cytotoxic T lymphocyte responses. Recently, a novel immunoregulatory role for MUC1 has been suggested by experiments demonstrating that soluble MUC1 induces T-cell unresponsiveness, and that T cells appear to express and secrete MUC1 following their activation. MUC1 is an apparent paradox, having both adhesive and antiadhesive functions, and immunostimulatory and immunosuppressive activities.

Expression of fully and under-glycosylated forms of MUC1 mucin in gastric carcinoma

The membrane-bound MUC1 mucin is expressed in normal mucosas and the aberrant expression of its under-glycosylated forms has been reported in carcinomas from different sites. Several studies have provided conflicting evidence regarding the relationship between MUC1 expression and outcome in cancer patients. In this study, we investigated the immunohistochemical expression of MUC1 epitopes, using 2 monoclonal antibodies (MAbs): HMFG1, which reacts with the fully glycosylated MUC1, was studied in 73 gastric carcinomas; and SM3, which recognises an under-glycosylated form of MUC1, was studied in 180 cases. HMFG1 stained the antrum foveolar cells and the body glands of normal gastric mucosa, whereas SM3 reactivity was restricted to the perinuclear region of some foveolar cells. Type I intestinal metaplasia exhibited down-regulation of MUC1 expression using both MAbs. Every gastric carcinoma was stained with HMFG1 and 80% with SM3. High levels of expression of HMFG1 were associated with lymphatic invasion, nodal metastatization, and advanced pTNM staging. The expression of SM3 was associated with the histologic (solid) type of carcinoma, expanding growth pattern, wall penetration, lymphatic invasion and age of the patients. Despite a trend for a poor outcome in patients with tumours (over)expressing MUC1 mucin, the survival of the patients evaluated by univariate and multivariate analysis was not significantly associated with the levels of expression of HMFG1 or with the expression of the SM3 epitope. We conclude that (a) MUC1 expression, namely of the SM3 cancer-associated epitope, is significantly associated with several aspects of gastric cancer development and progression; and (b) MUC1 expression should not be used as a prognostic marker in patients with gastric carcinoma.