Expression of MUC1 and MUC2 mucins in epithelial ovarian tumours

Deciphering cellular and molecular mechanism of MUC13 mucin involved in cancer cell plasticity and drug resistance

There has been a surge of interest in recent years in understanding the intricate mechanisms underlying cancer progression and treatment resistance. One molecule that has recently emerged in these mechanisms is MUC13 mucin, a transmembrane glycoprotein. Researchers have begun to unravel the molecular complexity of MUC13 and its impact on cancer biology. Studies have shown that MUC13 overexpression can disrupt normal cellular polarity, leading to the acquisition of malignant traits. Furthermore, MUC13 has been associated with increased cancer plasticity, allowing cells to undergo epithelial-mesenchymal transition (EMT) and metastasize. Notably, MUC13 has also been implicated in the development of chemoresistance, rendering cancer cells less responsive to traditional treatment options. Understanding the precise role of MUC13 in cellular plasticity, and chemoresistance could pave the way for the development of targeted therapies to combat cancer progression and enhance treatment efficacy.

Emerging role of mucins in antibody drug conjugates for ovarian cancer therapy

Ovarian cancer stands as the deadliest gynecologic malignancy, responsible for nearly 65% of all gynecologic cancer-related deaths. The challenges in early detection and diagnosis, coupled with the widespread intraperitoneal spread of cancer cells and resistance to chemotherapy, contribute significantly to the high mortality rate of this disease. Due to the absence of specific symptoms and the lack of effective screening methods, most ovarian cancer cases are diagnosed at advanced stages. While chemotherapy is a common treatment, it often leads to tumor recurrence, necessitating further interventions. In recent years, antibody-drug conjugates (ADCs) have emerged as a valuable tool in targeted cancer therapy. These complex biotherapeutics combine an antibody that specifically targets tumor specific/associated antigen(s) with a high potency anti-cancer drug through a linker, offering a promising approach for ovarian cancer treatment. The identification of molecular targets in various human tumors has paved the way for the development of targeted therapies, with ADCs being at the forefront of this innovation. By delivering cytotoxic agents directly to tumors and metastatic lesions, ADCs show potential in managing chemo-resistant ovarian cancers. Mucins such as MUC16, MUC13, and MUC1 have shown significantly higher expression in ovarian tumors as compared to normal and/or benign samples, thus have become promising targets for ADC generation. While traditional markers are limited by their elevated levels in non-cancerous conditions, mucins offer a new possibility for targeted treatment in ovarian cancer. This review comprehensively described the potential of mucins for the generation of ADC therapy, highlighting their importance in the quest to improve the outcome of ovarian cancer patients.

Diagnostic accuracy of flow cytometry in detecting malignant epithelial cells in serous effusions

INTRODUCTION

This study aims to evaluate diagnostic accuracy of flow cytometry (FCM) in detecting malignant epithelial cells in serous effusions.

MATERIALS AND METHODS

Flow cytometric assessment of 96 serous fluids (86 ascitic, 10 pleural) was performed by using epithelial cell adhesion molecule (EpCAM) (in all 96 fluids) and MUC-1 (in a subgroup of 40 fluids) as epithelial markers and CD45 and CD14 as leucocyte markers. The percentage of EpCAM positivity and MUC-1 positivity was calculated in the CD14 and CD45 dual negative population by selective gating. The findings were then correlated with the defined gold standard criteria.

RESULTS

The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy for EpCAM was found to be 92.06%, 96.96%, 98.31%, 86.48%, and 93.75%, respectively, while that for MUC-1 was 79.16%, 93.75%, 95%, 71.4%, and 85%, respectively. The sensitivity, specificity, PPV, NPV, and diagnostic accuracy for dual positivity for EpCAM and MUC-1 was found to be 83.3%, 100%, 100%, 80%, and 90% respectively. On combining FCM with cytomorphology the sensitivity, specificity, PPV, NPV, and diagnostic accuracy all increased greatly to 95.3%, 100%, 100%, 91.4%, and 96.8%, respectively.

CONCLUSIONS

This study highlights the importance of multicolored flow cytometric analysis in detecting epithelial malignancies in effusions specially in cases belonging to the atypia of undetermined significance and suspicious for malignancy categories and in cases with strong clinical suspicion of malignancy with negative fluid cytology. We recommend the combined use of FCM and cytology for this specific subgroup of patients in routine clinical practice for fast and accurate reporting.

Measuring the multifaceted roles of mucin-domain glycoproteins in cancer

Mucin-domain glycoproteins are highly O-glycosylated cell surface and secreted proteins that serve as both biochemical and biophysical modulators. Aberrant expression and glycosylation of mucins are known hallmarks in numerous malignancies, yet mucin-domain glycoproteins remain enigmatic in the broad landscape of cancer glycobiology. Here we review the multifaceted roles of mucins in cancer through the lens of the analytical and biochemical methods used to study them. We also describe a collection of emerging tools that are specifically equipped to characterize mucin-domain glycoproteins in complex biological backgrounds. These approaches are poised to further elucidate how mucin biology can be understood and subsequently targeted for the next generation of cancer therapeutics.

A Possible Inhibitory Role of Sialic Acid on MUC1 in Peritoneal Dissemination of Clear Cell-Type Ovarian Cancer Cells

The role of sialic acids on MUC1 in peritoneal dissemination of ovarian cancer cells was investigated. A human ovarian carcinoma cell line, ES-2, was transfected with full-length MUC1 containing 22 or 42 tandem repeats. These transfectants were less adherent to monolayers of patient-derived mesothelial cells than ES-2/mock transfectants. When these cells were inoculated into the abdominal cavity of female nude mice, mice that had received the transfectants showed better survival. When the transfectants were mixed with sialidase and injected, the survival was poorer, whereas when they were mixed with N-acetyl-2,3-dehydro-2-deoxyneuraminic acid, a sialidase inhibitor, the survival was significantly prolonged. These behaviors, concerned with peritoneal implantation and dissemination observed in vitro and in vivo, were dependent on the expression of MUC1. Therefore, sialic acid linked to MUC1 in the form, at least in part, of sialyl-T, as shown to be recognized by monoclonal antibody MY.1E12, is responsible for the suppression of adhesion of these cells to mesothelial cells and the suppression of peritoneal implantation and dissemination.

Association of MUC1 5640G>A and PSCA 5057C>T polymorphisms with the risk of gastric cancer in Northern Iran

BACKGROUND

Gastric cancer is one of the four most common cancer that causing death worldwide. Genome-Wide Association Studies (GWAS) have shown that genetic diversities MUC1 (Mucin 1) and PSCA (Prostate Stem Cell Antigen) genes are involved in gastric cancer. The aim of this study was avaluating the association of rs4072037G > A polymorphism in MUC1 and rs2294008 C > T in PSCA gene with risk of gastric cancer in northern Iran.

METHODS

DNA was extracted from 99 formalin fixed paraffin-embedded (FFPE) tissue samples of gastric cancer and 96 peripheral blood samples from healthy individuals (sex matched) as controls. Two desired polymorphisms, 5640G > A and 5057C > T for MUC1 and PSCA genes were genotyped using PCR-RFLP method.

RESULTS

The G allele at rs4072037 of MUC1 gene was associated with a significant decreased gastric cancer risk (OR = 0.507, 95% CI: 0.322-0.799, p = 0.003). A significant decreased risk of gastric cancer was observed in people with either AG vs. AA, AG + AA vs. GG and AA+GG vs. AG genotypes of MUC1 polymorphism (OR = 4.296, 95% CI: 1.190-15.517, p = 0.026), (OR = 3.726, 95% CI: 2.033-6.830, p = 0.0001) and (OR = 0.223, 95% CI: 0.120-0.413, p = 0.0001) respectively. Finally, there was no significant association between the PSCA 5057C > T polymorphism and risk of gastric cancer in all genetic models.

CONCLUSION

Results indicated that the MUC1 5640G > A polymorphism may have protective effect for gastric cancer in the Northern Iran population and could be considered as a potential molecular marker in gastric cancer.

89Zr-Labeled AR20.5: A MUC1-Targeting ImmunoPET Probe

High expression levels of the tumor-associated antigen MUC1 have been correlated with tumor aggressiveness, poor response to therapy, and poor survival in several tumor types, including breast, pancreatic, and epithelial ovarian cancer. Herein, we report the synthesis, characterization, and in vivo evaluation of a novel radioimmunoconjugate for the immuno-positron emission tomography (immunoPET) imaging of MUC1 expression based on the AR20.5 antibody. To this end, we modified AR20.5 with the chelator desferrioxamine (DFO) and labeled it with the positron-emitting radiometal zirconium-89 (t_1/2 ~3.3 d) to produce [⁸⁹Zr]Zr-DFO-AR20.5. In subsequent in vivo experiments in athymic nude mice bearing subcutaneous MUC1-expressing ovarian cancer xenografts, [⁸⁹Zr]Zr-DFO-AR20.5 clearly delineated tumor tissue, producing a tumoral activity concentration of 19.1 ± 6.4 percent injected dose per gram (%ID/g) at 120 h post-injection and a tumor-to-muscle activity concentration ratio of 42.4 ± 10.6 at the same time point. Additional PET imaging experiments in mice bearing orthotopic MUC1-expressing ovarian cancer xenografts likewise demonstrated that [⁸⁹Zr]Zr-DFO-AR20.5 enables the visualization of tumor tissue-including metastatic lesions-with promising tumor-to-background contrast.

Hormonal Regulation of MUC1 Expression

Several circulating mucinous markers, including CA 15.3, MCA, CA 459, CASA, and Truquant BR, are secreted products of the polymorphic MUC1 gene, and are used as diagnostic tools in patients with breast cancer. In clinical practice the measurement of the levels of these markers in the blood can give important information on the tumor's response to treatment and its biological behavior during disease monitoring. Since the marker levels reflect the activity of the tumor, it is important to know all factors influencing the production/secretion and the blood concentrations of MUC1 mucin. Recent findings suggest that MUC1 gene expression is regulated by steroid hormones and other substances present in the serum. Such observations are very important not only because of their biological significance but also for their clinical implications, as one approach to breast cancer therapy is based on chemical hormone manipulation. Nevertheless, we have preliminarily demonstrated that endocrine treatment in breast cancer patients does not influence the circulating CA 15.3 serum levels, so changes in marker levels are related only to the clinical evolution of the tumor.

Serum Tumor Markers may Precede Instrumental Response to Chemotherapy in Patients with Metastatic Cancer

Purpose

Although serum tumor markers (STMs) are widely used in clinical practice, their predictive role for the response to anticancer treatment is still controversial. The correlation of CEA, CA 15.3, CA 19.9, CA 125 (only with peritoneal involvement) and NSE levels with imaging response and clinical benefit was investigated in 60 non-selected patients with metastatic epithelial cancers treated by single-agent docetaxel chemotherapy.

Methods

STM measurement was performed at baseline and subsequently every three to four weeks. We applied the WHO criteria to evaluate both STM and instrumental responses. Concordance analysis was performed by the Cohen Kw index, and the significance of the results was established using the Fleiss, Cohen & Everitt test. Qualitative interpretation of data was obtained with the Landis & Koch scale. Correlations of STM response with clinical benefit (PS or pain improvement) were evaluated by the chi-square test.

Results

The primary tumors included breast cancers (38 patients), gastrointestinal non-colorectal cancers (12 patients), and lung cancers (10 patients). An overall significant good degree of agreement was observed between STM and instrumental response (p<0.0005). The degree of agreement for each marker was as follows: excellent for CEA (p<0.0005) and CA 125 (p=0.006), good for CA 15.3 (p<0.0005) and CA 19.9 (p=0.011). Restricted analysis for the correlation of each marker with primary tumor origin showed good prediction of radiological response for CA 15.3 and CEA in breast cancer patients (p<0.0005 for both), for CEA and CA 19.9 in gastrointestinal cancer patients (p=0.01 and 0.04, respectively), and for CEA+NSE in lung cancer patients (p=0.01). Conversely, STM response did not correlate significantly with the clinical benefit for the patients, both in terms of PS and pain improvement (p=0.24 and p=0.42, respectively).

Conclusion

This study showed STMs to be good predictors of tumor response. Although STMs cannot replace diagnostic imaging, in metastatic cancer they might be useful to optimize the timing of radiological re-evaluation in the palliative setting.

Glycosylation Changes in Brain Cancer

Protein glycosylation is a posttranslational modification that affects more than half of all known proteins. Glycans covalently bound to biomolecules modulate their functions by both direct interactions, such as the recognition of glycan structures by binding partners, and indirect mechanisms that contribute to the control of protein conformation, stability, and turnover. The focus of this Review is the discussion of aberrant glycosylation related to brain cancer. Altered sialylation and fucosylation of N- and O-glycans play a role in the development and progression of brain cancer. Additionally, aberrant O-glycan expression has been implicated in brain cancer. This Review also addresses the clinical potential and applications of aberrant glycosylation for the detection and treatment of brain cancer. The viable roles glycans may play in the development of brain cancer therapeutics are addressed as well as cancer-glycoproteomics and personalized medicine. Glycoprotein alterations are considered as a hallmark of cancer while high expression in body fluids represents an opportunity for cancer assessment.

Dual Role of the Extracellular Domain of Human Mucin MUC1 in Metastasis

Human mucin MUC1 plays an important role in cancer development. The increased level of this molecule expression during cancer cell progression induces metastasis and is associated with poor prognosis for patients. There is a large body of experimental data on the role of various functional domains of human mucin MUC1 in metastasis. While, the cytoplasmic domain determined to play a definitive role, the influence of extracellular domain on cancer cell invasiveness still remains unclear. The present paper reveals that the extracellular domain of MUC1 molecule consists of two functional subdomains-the region of tandem repeats (TR) and the region of irregular repeats (IR). We demonstrate the ability of each of these subdomains to alter the invasiveness of cancer cells. The presence of the MUC1 molecules containing TR subdomain (MUC1-TR) on the surface of low-invasive cancer cells leads to the increase in their transendothelial migration potency, while the addition of the IR subdomain to the MUC1-TR molecule (MUC1-IR-TR) restores their natural low invasiveness. J. Cell. Biochem. 118: 4002-4011, 2017. © 2017 Wiley Periodicals, Inc.

A novel electrochemical biosensor based on polyadenine modified aptamer for label-free and ultrasensitive detection of human breast cancer cells

Simple, rapid, sensitive, and specific detection of cancer cells plays a pivotal role in the diagnosis and prognosis of cancer. A sandwich electrochemical biosensor was developed based on polyadenine (polydA)-aptamer modified gold electrode (GE) and polydA-aptamer functionalized gold nanoparticles/graphene oxide (AuNPs/GO) hybrid for the label-free and selective detection of breast cancer cells (MCF-7) via a differential pulse voltammetry (DPV) technique. Due to the intrinsic affinity between multiple consecutive adenines of polydA sequences and gold, polydA modified aptamer instead of thiol terminated aptamer was immobilized on the surface of GE and AuNPs/GO. The label-free MCF-7 cells could be recognized by polydA-aptamer and self-assembled onto the surface of GE. The polydA-aptamer functionalized AuNPs/GO hybrid could further bind to MCF-7 cells to form a sandwich sensing system. Characterization of the surface modified GE was carried out by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using Fe(CN)₆^3-/4- as a redox probe. Under the optimized experimental conditions, a detection limit of 8 cellsmL^-1 (3σ/slope) was obtained for MCF-7 cells by the present electrochemical biosensor, along with a linear range of 10-10⁵ cellsmL^-1. By virtue of excellent sensitivity, specificity and repeatability, the present electrochemical biosensor provides a potential application in point-of-care cancer diagnosis.

Effects of Kras activation and Pten deletion alone or in combination on MUC1 biology and epithelial-to-mesenchymal transition in ovarian cancer

Mucin1 (MUC1) is an epithelial glycoprotein overexpressed in ovarian cancer and actively involved in tumor cell migration and metastasis. Using novel in vitro and in vivo MUC1-expressing conditional (Cre-loxP) ovarian tumor models, we focus here on MUC1 biology and the roles of Kras activation and Pten deletion during cell transformation and epithelial-to-mesenchymal transition (EMT). We generated several novel murine ovarian cancer cell lines derived from the ovarian surface epithelia (OSE) of mice with conditional mutations in Kras, Pten or both. In addition, we also generated several tumor-derived new cell lines that reproduce the original tumor phenotype in vivo and mirror late stage metastatic disease.

Our results demonstrate that de novo activation of oncogenic Kras does not trigger increased proliferation, cellular transformation or EMT and prevents MUC1 upregulation. In contrast, Pten deletion accelerates cell proliferation, triggers cellular transformation in vitro and in vivo and stimulates MUC1 expression. Ovarian tumor-derived cell lines MKP-Liver and MKP-Lung cells reproduce in vivo EMT and represent the first immune competent mouse model for distant hematogenous spread. Whole genome microarray expression analysis using tumor and OSE-derived cell lines reveals a 121 gene signature associated with EMT and metastasis. When applied to n=542 cases from the ovarian cancer TCGA dataset, the gene signature identifies a patient subset with decreased survival (p=0.04). Using an extensive collection of novel murine cell lines we have identified distinct roles for Kras and Pten on MUC1 and EMT in vivo and in vitro. The data has implications for future design of combination therapies targeting Kras mutations, Pten deletions and MUC1 vaccines.

Oxygen-Related Differences in Cellular and Vesicular Phenotypes Observed for Ovarian Cell Cancer Lines

Extracellular vesicles (EVs) are one of several tools that cells use to communicate with each other. This communication is facilitated by a number of surface-associated proteins and the cargo of the vesicles. For several cancer types, the amount of EVs is observed to be up-regulated in patients compared to healthy individuals, possibly signifying the presence of an aberrant process. The hypoxia-induced release of EVs from cancer cells has been hypothesized to cause the malignant transformation of healthy recipient cells. In this study, the phenotype of cells and EVs from the ovarian cancer cell lines, COV504, SKOV3, and Pt4, were quantified and analysed under normoxic and hypoxic conditions. It was shown that both cells and EVs express common markers and that the EV phenotype varies more than the cellular phenotype. Additionally, cells subjected to 24 hours of hypoxia compared to normoxia produced more EVs. The phenotyping of EVs from cancer cell lines provides information about their molecular composition. This information may be translated to knowledge regarding the functionality of EVs and lead to a better understanding of their role in cancer.

Exploring the role and diversity of mucins in health and disease with special insight into non-communicable diseases

Mucins are major glycoprotein components of the mucus that coats the surfaces of cells lining the respiratory, digestive, gastrointestinal and urogenital tracts. They function to protect epithelial cells from infection, dehydration and physical or chemical injury, as well as to aid the passage of materials through a tract i.e., lubrication. They are also implicated in the pathogenesis of benign and malignant diseases of secretory epithelial cells. In Human there are two types of mucins, membrane-bound and secreted that are originated from mucous producing goblet cells localized in the epithelial cell layer or in mucous producing glands and encoded by MUC gene. Mucins belong to a heterogeneous family of high molecular weight proteins composed of a long peptidic chain with a large number of tandem repeats that form the so-called mucin domain. The molecular weight is generally high, ranging between 0.2 and 10 million Dalton and all mucins contain one or more domains which are highly glycosylated. The size and number of repeats vary between mucins and the genetic polymorphism represents number of repeats (VNTR polymorphisms), which means the size of individual mucins can differ substantially between individuals which can be used as markers. In human it is only MUC1 and MUC7 that have mucin domains with less than 40% serine and threonine which in turn could reduce number of PTS domains. Mucins can be considered as powerful two-edged sword, as its normal function protects from unwanted substances and organisms at an arm's length while, malfunction of mucus may be an important factor in human diseases. In this review we have unearthed the current status of different mucin proteins in understanding its role and function in various non-communicable diseases in human with special reference to its organ specific locations. The findings described in this review may be of direct relevance to the major research area in biomedicine with reference to mucin and mucin associated diseases.

Glycosylation alterations in lung and brain cancer

Alterations in glycosylation are common in cancer and are thought to contribute to disease. Lung cancer and primary malignant brain cancer, most commonly glioblastoma, are genetically heterogeneous diseases with extremely poor prognoses. In this review, we summarize the data demonstrating that glycosylation is altered in lung and brain cancer. We then use specific examples to highlight the diverse roles of glycosylation in these two deadly diseases and illustrate shared mechanisms of oncogenesis. In addition to alterations in glycoconjugate biosynthesis, we also discuss mechanisms of postsynthetic glycan modification in cancer. We suggest that alterations in glycosylation in lung and brain cancer provide novel tumor biomarkers and therapeutic targets.

Overexpression of mucin 13 due to promoter methylation promotes aggressive behavior in ovarian cancer cells

PURPOSE

Recent discoveries suggest that aberrant DNA methylation provides cancer cells with advanced metastatic properties. However, the precise regulatory mechanisms controlling metastasis genes and their role in metastatic transformation are largely unknown. To address epigenetically-regulated gene products involved in ovarian cancer metastasis, we examined the mechanisms regulating mucin 13 (MUC13) expression and its influence on aggressive behaviors of ovarian malignancies.

MATERIALS AND METHODS

We injected SK-OV-3 ovarian cancer cells peritoneally into nude mice to mimic human ovarian tumor metastasis. Overexpression of MUC13 mRNA was detected in metastatic implants from the xenografts by expression microarray analysis and quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The DNA methylation status within the MUC13 promoter region was determined using bisulfite sequencing PCR and quantitative methylation-specific PCR. We evaluated the effects of exogenous MUC13 on cell invasion and migration using in vitro transwell assays.

RESULTS

MUC13 mRNA expression was up-regulated, and methylation of specific CpG sites within the promoter was reduced in the metastatic implants relative to those in wild-type SK-OV-3 cells. Addition of a DNA methyltransferase inhibitor to SK-OV-3 cells induced MUC13 expression, thereby implying epigenetic regulation of MUC13 by promoter methylation. MUC13 overexpression increased migration and invasiveness, compared to control cells, suggesting aberrant up-regulation of MUC13 is strongly associated with progression of aggressive behaviors in ovarian cancer.

CONCLUSION

We provide novel evidence for epigenetic regulation of MUC13 in ovarian cancer. We suggest that the DNA methylation status within the MUC13 promoter region may be a potential biomarker of aggressive behavior in ovarian cancer.

Superparamagnetic iron oxide-C595: Potential MR imaging contrast agents for ovarian cancer detection

Superparamagnetic iron oxide nanoparticles (SPIONs), have played an important role in the promotion of image contrast in magnetic resonance imaging modality. The objective of present study is describing SPIONs conjugated with C595 monoclonal antibody (mAb) against MUC1-expressing ovarian cancer (OVCAR3) cell. Magnetic resonance imaging parameters of the prepared nanoconjugate was investigated in vitro: characterization, cell toxicity, flow cytometry, Prussian blue staining, and cellular uptake as well as biodistribution and magnetic resonance signal intensities under in vivo conditions were also investigated. Magnetic resonance imaging and biodistribution results showed good tumor accumulation and detection, no cytotoxicity, and potential selective as anti-ovarian cancer. In conclusion, based on the findings SPIONs-C595 nanosized-probe is potentially, a selective ovarian molecular imaging tool. Further subsequent in vivo studies and clinical trials are warranted.

Antitumor effects of cisplatin combined with tecemotide immunotherapy in a human MUC1 transgenic lung cancer mouse model

The goals of the present study were to define the effects of simultaneous cisplatin/tecemotide therapy on tumor development in a human mucin 1 (MUC1) transgenic lung cancer mouse model and to examine the effects of radiotherapy (RTX) on splenocytes, serum cytokines, and immune response to tecemotide. Two hundred twenty-six human MUC1 transgenic C57BL/6 mice were used in five studies designed to assess (i) serum cytokine and immune responses following four weekly 10-μg doses of tecemotide; (ii) the effects of simultaneous administration of cisplatin (2.5 mg/kg × 2 doses/cycle × 4 cycles) and tecemotide (2 cycles × 8 weekly 10-μg doses/cycle) therapy on tumor development, serum cytokines, and immune response; (iii) the dose-response effects of RTX on lymphocyte counts 16 hours following doses of 2 to 8 Gy; (iv) the time course of lymphocyte recovery from 16 hours to 20 days following 8-Gy RTX; and (v) the effects of simultaneous administration of RTX (8 Gy) and tecemotide on the immune response to tecemotide (four weekly 10-μg doses). Serum cytokines were analyzed by multiplex immunoassay, IFNγ immune responses by enzyme-linked immunosorbent spot (ELISpot), and lung tumor foci by lung whole mounts. Simultaneous cisplatin/tecemotide therapy resulted in significant and additive reduction in lung tumor foci compared with control mice, with significantly elevated serum IFNγ levels and specific IFNγ immune responses observed in both tecemotide and tecemotide + cisplatin-treated mice. Finally, neither cisplatin nor radiation interfered with the immune response to tecemotide.

A high M1/M2 ratio of tumor-associated macrophages is associated with extended survival in ovarian cancer patients

BACKGROUND

Tumor-associated macrophages (TAMs) are classified into two major phenotypes, M1 and M2. M1 TAMs suppress cancer progression, while M2 TAMs promote it. However, little is known regarding the role of TAMs in the development of ovarian cancer. Here, we investigated the relationship between TAM distribution patterns (density, microlocalization, and differentiation) and ovarian cancer histotypes, and we explored whether altered TAM distribution patterns influence long-term outcomes in ovarian cancer patients.

METHODS

A total of 112 ovarian cancer patients were enrolled in this study, and the subjects were divided into two groups according to their survival (< 5 years vs. ≥ 5 years). Immunohistochemistry and immunofluorescence were used to determine the density, microlocalization, and differentiation status of TAMs in ovarian cancer tissues for each histotype. Kaplan-Meier survival and multivariate Cox regression analyses were used to evaluate the prognostic significance of TAM-related parameters in ovarian cancer.

RESULTS

TAMs most frequently infiltrated into the cancer tissue of the serous histotype, followed by mucinous, undifferentiated, endometrioid, and clear cell histotypes (p = 0.049). The islet/stroma ratio of total TAMs varied among the cancer histotypes, with mucinous and undifferentiated cancers displaying the lowest and highest ratios, respectively (p = 0.005). The intratumoral TAM density significantly increased with increasing cancer stage and grade (p = 0.023 and 0.006, respectively). However, the overall M1/M2 TAM ratio decreased as the cancer stage increased (p = 0.012). In addition, the intra-islet M1/M2 ratio inversely correlated with the residual site size (p = 0.004). Among the TAM-related parameters, only the increased overall and intra-islet M1/M2 TAM ratios displayed prognostic significance in both the Kaplan-Meier survival and multivariate Cox regression analyses; however, the values of these two parameters did not differ significantly among the cancer histotypes.

CONCLUSIONS

The patients with increased overall or intra-islet M1/M2 TAM ratios presented with an improved 5-year prognosis. Nevertheless, the TAM distribution patterns did not influence the overall outcomes of different ovarian cancer histotypes.

MUC1 cytoplasmic tail: a potential therapeutic target for ovarian carcinoma

Ovarian cancer is often a lethal disease, since the occult progression of the tumor within the peritoneal cavity results in late diagnosis and treatment failure. The identification of molecular events specific to metastasis is critical for the development of effective therapies. MUC1 is aberrantly overexpressed by most ovarian cancer and regarded as a molecular target for ovarian cancer. This review focuses on the latest advances regarding a signaling region in the MUC1 C-terminal subunit-mediated c-Src signaling pathways in malignant transformation, invasion and metastasis. Disruption of MUC1-C-terminal subunit-associated c-Src signaling by targeting the specific sites might represent a novel immunotherapeutic approach for the treatment of ovarian cancer.

Interactions between MUC1 and p120 catenin regulate dynamic features of cell adhesion, motility, and metastasis

The mechanisms by which MUC1 and p120 catenin contribute to progression of cancers from early transformation to metastasis are poorly understood. Here we show that p120 catenin ARM domains 1, 3-5, and 8 mediate interactions between p120 catenin and MUC1, and that these interactions modulate dynamic properties of cell adhesion, motility, and metastasis of pancreatic cancer cells. We also show that different isoforms of p120 catenin, when coexpressed with MUC1, create cells that exhibit distinct patterns of motility in culture (motility independent of cell adhesion, motility within a monolayer while exchanging contacts with other cells, and unified motility while maintaining static epithelial contacts) and patterns of metastasis. The results provide new insight into the dynamic interplay between cell adhesion and motility and the relationship of these to the metastatic process.

High MUC2 expression in ovarian cancer is inversely associated with the M1/M2 ratio of tumor-associated macrophages and patient survival time

Mucin 2 (MUC2) is a mucin molecule aberrantly expressed by ovarian cancer cells. Previous in vitro studies have indicated that MUC2 promotes cancer growth and metastasis through a tumor-associated macrophage (TAM)-dependent mechanism. However, this mechanism has never been linked to clinical oncology, and its prognostic significance needed to be clarified. Here, we collected 102 consecutive ovarian cancer specimens and used the multiple immuno-histo-chemical/-fluorescent technique to determine the correlations between the MUC2 expression status, the ratio of M1/M2 TAMs and the densities of cyclooxygenase-2 (COX-2)⁺ TAMs and COX-2⁺ cancer cells. The Kaplan-Meier survival analysis and multivariate Cox regression analysis were used to evaluate the prognostic influences of these parameters. As a result, we found that the MUC2 overexpression (immunostaining ++/+++) was significantly correlated with a reduced ratio of M1/M2 TAMs (p<0.001), an increased density of COX-2⁺ TAMs (p<0.001) and an increased density of COX-2⁺ cancer cells (p=0.017). Moreover, most of the M2 TAMs (93%-100%) and COX-2⁺ TAMs (63%-89%) overlapped; and the COX-2⁺ cancer cells were frequently observed near the COX-2⁺ TAMs. In the Cox regression analysis, MUC2 overexpression was found to be an independent prognostic factor for ovarian cancer patients, of which the hazard ratio (HR) was 2.354 (95% confidence interval (CI): 1.031-10.707, p=0.005). Also, the reduced ratio of M1/M2 TAMs and the increased densities of COX-2⁺ TAMs and COX-2⁺ cancer cells were demonstrated to be the predictors of poor prognosis, among which the reduced M1/M2 ratio possessed the highest HR (1.767, 95% CI: 1.061-6.957, p=0.019). All these findings revealed that MUC2 can concurrently exert M2-polarizing and COX-2-inducing effects on TAMs, by which it causes an imbalanced TAM M1-/M2-polarization pattern and induces local PGE₂ synthesis (in both TAMs and cancer cells). The positive feedback between local PGE₂ synthesis and TAM M2-polarization accelerates ovarian cancer progression.

MUC4 as a diagnostic marker in cancer

BACKGROUND

Mucins are high molecular mass glycoproteins whose role in diagnosis, prognosis and therapy is being increasingly recognized owing to their altered expression in a variety of carcinomas. MUC4, a membrane-bound mucin encoded by a gene located on chromosome locus 3q29, is aberrantly expressed in several cancers including those of the bile duct, breast, colon, esophagus, ovary, lung, prostate, stomach and pancreas.

OBJECTIVE

This review considers the potential use of the MUC4 expression pattern in the diagnosis and prognosis of various cancers.

RESULTS/CONCLUSION

MUC4 expression is a specific marker of epithelial tumors and its expression correlates positively with the degree of differentiation in several cancers. Importantly, MUC4 has emerged as a specific marker of dysplasia, being expressed in the earliest dysplastic lesions preceding several malignancies, including lethal pancreatic cancer. The presence of MUC4-specific antibodies in the serum and of the transcript in peripheral blood mononuclear cells of cancer patients raises the possibility of it emerging as a new diagnostic biomarker for bedside application in high-risk individuals and those with established cancer.

Antitumor effects of L-BLP25 antigen-specific tumor immunotherapy in a novel human MUC1 transgenic lung cancer mouse model

BACKGROUND

L-BLP25 antigen-specific cancer immunotherapeutic agent is currently in phase III clinical trials for non-small cell lung cancer. Using a novel human MUC1 transgenic (hMUC1.Tg) lung cancer mouse model, we evaluated effects of L-BLP25 combined with low-dose cyclophosphamide (CPA) pretreatment on Th1/Th2 cytokine production and antitumor activity.

METHODS

A chemically-induced lung tumor model was developed in hMUC1.Tg C57BL/6 mice by administering 10 weekly 0.75-mg/g doses of the chemical carcinogen urethane by intraperitoneal injection. Serum cytokines associated with Th1/Th2 polarization and inflammation were measured by multiplex cytokine assay during tumorigenesis. Antitumor activity of L-BLP25 (10 μg) with CPA (100 mg/kg) pretreatment was evaluated following either one or two eight-week cycles of treatment by preparing lung whole mounts and counting tumor foci, and assessing IFN-γ production by ELISpot assay.

RESULTS

During the carcinogenesis phase, no detectable Th1- or Th2-associated cytokine responses were observed, but levels of pro-inflammatory cytokines were increased with distinctive kinetics. A single cycle of L-BLP25 consisting of eight weekly doses was ineffective, whereas adding a second cycle given during tumor progression showed a significant reduction in the incidence of tumor foci. Administering two cycles of L-BLP25 induced Th1 cytokines IL-12, IL-2 and IFNγ at 24 h after the last dose, while Th2 and inflammatory cytokines were elevated to a lesser extent.

CONCLUSIONS

Urethane-induced lung tumors in hMUC1.Tg mice can be used as a model to assess the efficacy of the MUC1 antigen-specific cancer immunotherapeutic agent L-BLP25. The results indicate that the antitumor response to L-BLP25 requires at least two cycles and pre-treatment with CPA. In addition, monitoring pro-inflammatory serum cytokines may be useful as a biomarker of L-BLP25 response. Taken together, the preclinical lung tumor model can be utilized for determining effective combinations of L-BLP25 with chemotherapy and/or other immunotherapies.

MUC1 and metastatic cancer: expression, function and therapeutic targeting

MUC1 is a transmembrane mucin that is often overexpressed in metastatic cancers and often used as a diagnostic marker for metastatic progression. The extracellular domain of MUC1 can serve as a ligand for stromal and endothelial cell adhesion receptors, and the cytoplasmic domain engages in several interactions that can result in increased migration and invasion, as well as survival. In this review, we address the role of MUC1 in metastatic progression by assessing clinical studies reporting MUC1 levels at various disease stages, reviewing mouse models utilized to study the role of MUC1 in metastatic progression, discuss mechanisms of MUC1 upregulation, and detail MUC1 protein interactions and signaling events. We review interactions between MUC1 and the extracellular environment, with proteins colocalized in the plasma membrane and/or cytoplasmic proteins, and summarize the role of MUC1 in the nucleus as a transcriptional cofactor. Finally, we review recent publications describing current therapies targeting MUC1 in patients with advanced disease and the stage of these therapies in preclinical development or clinical trials.

Loss of MUC2 expression predicts disease recurrence and poor outcome in colorectal carcinoma

Clinical staging and histological grading after surgery have been the "gold standard" for predicting prognosis and planning for adjuvant therapy of colorectal cancer (CRC). With the recent development of molecular markers, it has become possible to characterize tumors at the molecular level. This is important for stage II and III CRCs, in which clinicopathological features do not accurately predict heterogeneity, e.g., in their tumor response to adjuvant therapy. In the present study, archival samples from 141 patients with stage I, II, III, or IV CRC treated during 1981-1990 at Turku University Hospital (Finland) were used (as microarray blocks) to analyze MUC2 expression by immunohistochemistry. Altogether, 49.7 % of all tumors were positive for MUC2. There was no significant correlation between MUC2 expression and age (P < 0.499), tumor invasion (P < 0.127), tumor staging (P < 0.470), histological grade (P < 0.706), lymph node involvement (P < 0.854), or tumor metastasis (P < 0.586). However, loss of MUC2 expression was significantly associated with disease recurrence (P < 0.031), tumor localization (P < 0.048), and with borderline significance with gender (P < 0.085). In univariate (Kaplan-Meier) survival analysis, positive MUC2 significantly predicted longer disease-free survival (DFS) and disease-specific survival (DSS) as well. However, in multivariate (Cox) survival analysis, MUC2 lost its power as an independent predictor of DFS and DSS. Our results implicate the value of MUC2 expression in predicting disease recurrence and long-term survival in CRC.

Mucin-producing tumors and tumor-like lesions involving the prostate: a comprehensive review

Mucin-producing tumors of the prostate include both primary and secondary tumors with mucinous differentiation or features involving the prostate gland. These tumors are relatively rare and have variable prognostic and therapeutic implications. Primary mucinous (colloid) adenocarcinoma of the prostate is defined as prostatic adenocarcinoma with mucinous differentiation involving 25% or more of the entire tumor. Another primary tumor of the prostate that may have mucinous features is primary mucin-producing urothelial-type adenocarcinoma of the prostate (mucinous prostatic urethral adenocarcinoma). Primary mucin-producing urothelial-type adenocarcinoma of the prostate is a distinct entity that typically arises from the prostatic urethra possibly from urethritis glandularis or glandular metaplasia with malignant transformation, and it is analogous to adenocarcinoma with mucinous differentiation arising from the urinary bladder. Signet ring cell tumors of the prostate, though rare, may also have mucinous features. Secondary tumors with mucinous differentiation that may involve the prostate include adenocarcinomas of the urinary bladder and colorectum. Pathologists should also be aware of mucin-producing tumor-like lesions involving the prostate, including mucinous metaplasia, and benign Cowper glands that may mimic malignancy. Herein we present an updated and comprehensive review of the clinicopathologic, immunohistochemical, molecular, and prognostic features of mucinous tumors and tumor-like lesions involving the prostate gland, with emphasis on mucinous prostatic adenocarcinoma and its mimickers, including potential diagnostic pitfalls.

Systematic analysis and validation of differential gene expression in ovarian serous adenocarcinomas and normal ovary

PURPOSE

Cancer of the ovary confers the worst prognosis among women with gynecological malignancies, primarily because most ovarian cancers are diagnosed at late stage. Hence, there is a substantial need to develop new diagnostic biomarkers to enable detection of ovarian cancer at earlier stages, which would confer better prognosis. In addition, the identification of druggable targets is of substantial interest to find new therapeutic strategies for ovarian cancer.

METHODS

The expression of 22,500 genes in a series of 67 serous papillary carcinomas was compared with 9 crudely enriched normal ovarian tissue samples by RNA hybridization on oligonucleotide microarrays. Multiple genes with near-uniformly expression were elevated in carcinomas of varying grade and malignant potential, including several previously described genes (e.g., MUC-1, CD9, CD24, claudin 3, and mesothelin). We performed immunohistochemical staining with antibodies against several of the proteins encoded by differentially expressed genes in an independent cohort of 71 cases of paraffin-embedded ovarian cancer samples.

RESULTS

We found striking differences in EpCAM (p < 0.005), CD9 (p < 0.001), MUC-1 (p < 0.001), and claudin 3 proteins (p < 0.001) but not for mesothelin (p > 0.05) using the Mann-Whitney U test.

CONCLUSIONS

Protein expression of a majority of the differentially expressed genes tested was found to be elevated in ovarian carcinomas and, as such, define potential new biomarkers or targets.

MUC2 polymorphisms are associated with endometriosis development and infertility: a case-control study

BACKGROUND

Mucins are highly glycosylated proteins protecting and lubricating epithelial surface of respiratory, gastrointestinal and reproductive tracts. Members of the mucin protein family have been suggested to play an important role in development of endometriosis and infertility. This study investigates genetic association of mucin2 (MUC2) with the risk of endometriosis and endometriosis-related infertility.

METHODS

This case-control study was conducted at China Medical University Hospital, with 195 endometriosis patients and 196 healthy controls enrolled. Genotyping of six SNPs (rs2856111, rs11245936, rs10794288, rs10902088, rs7103978 and rs11245954) within MUC2 gene were performed by using Taqman genotyping assay; individual SNP and haplotype associations with endometriosis and endometriosis-related infertility were assessed by χ² test.

RESULTS

Endometriosis patients exhibit significantly lower frequency of the rs10794288 C allele, the rs10902088 T allele and the rs7103978 G allele (P = 0.030, 0.013 and 0.040, respectively). In addition, the rs10794288 C allele and the rs10902088 T allele were also less abundant in patients with infertility versus fertile ones (P = 0.015 and 0.024, respectively). Haplotype analysis of the endometriosis associated SNPs in MUC2 also showed significantly association between the most common haplotypes and endometriosis or endometriosis-related infertility.

CONCLUSIONS

MUC2 polymorphisms, especially rs10794288 and rs10902088, are associated with endometriosis as well as endometriosis-related infertility. Our data present MUC2 as a new candidate involved in development of endometriosis and related infertility in Taiwanese Han women.

Characterization of cancer associated mucin type O-glycans using the exchange sialylation properties of mammalian sialyltransferase ST3Gal-II

Our previous studies suggest that the α2,3sialylated T-antigen (NeuAcα2,3Galβ1,3GalNac-) and associated glycan structures are likely to be elevated during cancer. An easy and reliable strategy to label mucinous glycans that contain such carbohydrates can enable the identification of novel glycoproteins that are cancer associated. To this end, the present study demonstrates that the exchange sialylation property of mammalian ST3Gal-II can facilitate the labeling of mucin glycoproteins in cancer cells, tumor specimens, and glycoproteins in cancer sera. Results show that (i) the radiolabeled mucin glycoproteins of each of the cancer cell lines studied (T47D, MCF7, LS180, LNCaP, SKOV3, HL60, DU4475, and HepG2) is distinct either in terms of the specific glycans presented or their relative distribution. While some cell lines like T47D had only one single sialylated O-glycan, others like LS180 and DU4475 contained a complex mixture of mucinous carbohydrates. (ii) [14C]sialyl labeling of primary tumor cells identified a 25-35 kDa mucin glycoprotein unique to pancreatic tumor. Labeled glycoproteins for other cancers had higher molecular weight. (iii) Studies of [14C] sialylated human sera showed larger mucin glycopeptides and >2-fold larger mucin-type chains in human serum compared to [14C]sialyl labeled glycans of fetuin. Overall, the exchange sialylation property of ST3Gal-II provides an efficient avenue to identify mucinous proteins for applications in glycoproteomics and cancer research.

Natural and Induced Humoral Responses to MUC1

MUC1 is a membrane-tethered mucin expressed on the ductal cell surface of glandular epithelial cells. Loss of polarization, overexpression and aberrant glycosylation of MUC1 in mucosal inflammation and in adenocarcinomas induces humoral immune responses to the mucin. MUC1 IgG responses have been associated with a benefit in survival in patients with breast, lung, pancreatic, ovarian and gastric carcinomas. Antibodies bound to the mucin may curb tumor progression by restoring cell-cell interactions altered by tumor-associated MUC1, thus preventing metastatic dissemination, as well as counteracting the immune suppression exerted by the molecule. Furthermore, anti-MUC1 antibodies are capable of effecting tumor cell killing by antibody-dependent cell-mediated cytotoxicity. Although cytotoxic T cells are indispensable to achieve anti-tumor responses in advanced disease, abs to tumor-associated antigens are ideally suited to address minimal residual disease and may be sufficient to exert adequate immune surveillance in an adjuvant setting, destroying tumor cells as they arise or maintaining occult disease in an equilibrium state. Initial evaluation of MUC1 peptide/glycopeptide mono and polyvalent vaccines has shown them to be immunogenic and safe; anti-tumor responses are scarce. Progress in carbohydrate synthesis has yielded a number of sophisticated substrates that include MUC1 glycopeptide epitopes that are at present in preclinical testing. Adjuvant vaccination with MUC1 glycopeptide polyvalent vaccines that induce strong humoral responses may prevent recurrence of disease in patients with early stage carcinomas. Furthermore, prophylactic immunotherapy targeting MUC1 may be a strategy to strengthen immune surveillance and prevent disease in subjects at hereditary high risk of breast, ovarian and colon cancer.

Mucin 13: structure, function, and potential roles in cancer pathogenesis

Mucin 13 (MUC13) is a high-molecular-weight transmembrane glycoprotein that is frequently and aberrantly expressed in a variety of epithelial carcinomas, including gastric, colorectal, and ovarian cancers. On the basis of the high expression of MUC13 in cancer cells as well as recent laboratory findings suggesting a malignant phenotype of MUC13-transfected cell lines, the oncogenic potential of MUC13 has emerged. The various functional domains of MUC13 may confer oncogenic potential to MUC13. For example, the bulky extracellular domain with extensive modification with glycan chains may prevent cell-cell and cell-extracellular matrix binding whereas the cytoplasmic tail containing serine and tyrosine residues for potential phosphorylation may participate in cell signaling. MUC13 exhibits the characteristics suitable as an early marker for cancer screening and presents a promising target for antibody-guided targeted therapy.

Analysis of a cholera toxin B subunit (CTB) and human mucin 1 (MUC1) conjugate protein in a MUC1-tolerant mouse model

Since epithelial mucin 1 (MUC1) is associated with several adenocarcinomas at the mucosal sites, it is pertinent to test the efficacy of a mucosally targeted vaccine formulation. The B subunit of the Vibrio cholerae cholera toxin (CTB) has great potential to act as a mucosal carrier for subunit vaccines. In the present study we evaluated whether a MUC1 tandem repeat (TR) peptide chemically linked to CTB would break self-antigen tolerance in the transgenic MUC1-tolerant mouse model (MUC1.Tg) through oral or parenteral immunizations. We report that oral immunization with the CTB-MUC1 conjugate along with mucosal adjuvant, unmethylated CpG oligodeoxynucleotide (ODN) and interleukin-12 (IL-12) did not break self-antigen tolerance in MUC1.Tg mice, but induced a strong humoral response in wild-type C57BL/6 mice. However, self-antigen tolerance in the MUC1.Tg mouse model was broken after parenteral immunizations with different doses of the CTB-MUC1 conjugate protein and with the adjuvant CpG ODN co-delivered with CTB-MUC1. Importantly, mice immunized systemically with CpG ODN alone and with CTB-MUC1 exhibited decreased tumor burden when challenged with a mammary gland tumor cell line that expresses human MUC1.

Extensive enrichment of N-glycolylneuraminic acid in extracellular sialoglycoproteins abundantly synthesized and secreted by human cancer cells

N-Glycolylneuraminic acid (Neu5Gc) is the second most populous sialic acid (Sia). The only known biosynthetic pathway of Neu5Gc is the hydroxylation of cytidine-5'-monophosphate-N-acetylneuraminic acid (CMP-Neu5Ac), catalyzed by CMP-Neu5Ac hydroxylase (CMAH). Neu5Gc is abundantly found in mammals except for human, in which CMAH is inactivated due to mutation in the CMAH gene. Evidence has accumulated to show occurrence of Neu5Gc-containing glycoconjugates in sera of cancer patients, human cancerous tissues and cultured human cell lines. Recently, occurrence of natural antibodies against Neu5Gc was shown in healthy humans and is a serious problem for clinical xenotransplantation and stem cell therapies. Studying human occurrence of Neu5Gc is of importance and interest in a broad area of medical sciences. In this study, using a fluorometric high performance liquid chromatography method, we performed quantitative analyses of Sias both inside and in the external environment of the cell and found that (i) incorporation of Neu5Gc was most prominent in soluble glycoproteins found both in the extracellular space and inside the cell as the major Sia compounds. (ii) Of the total Neu5Gc in the Sia compounds that the cells synthesized, 90% was found in the secreted sialoglycoproteins, whereas for Neu5Ac, 70% was found in the secreted sialoglycoproteins. (iii) The Neu5Gc ratio was higher in the secreted sialoglycoproteins (as high as 40% of total Sias) than in intracellular sialoglycoproteins. (iv) The majority of the secreted sialoglycoproteins was anchored on the culture dishes and solubilized by brief trypsin treatment. Based on these findings, a new idea on the mechanism of accumulation of Neu5Gc in cancer cells was proposed.

Mucins in ovarian cancer diagnosis and therapy

Ovarian cancer is the most lethal gynecologic malignancy and the five-year survival rate is only 35% after diagnosis. Epithelial ovarian cancer is a highly metastatic disease characterized by widespread peritoneal dissemination and ascites. The death incidences from ovarian cancer could be significantly lowered by developing new methods for the early diagnosis and treatment of this fatal disease. Several potential markers have been identified recently. However, mucins are the most promising markers for ovarian cancer diagnosis. Mucins are large extracellular, heavily glycosylated proteins and their aberrant expression has been implicated in the pathogenesis of a variety of cancers, including ovarian cancer. This review will summarize known facts about the pathological and molecular characteristics of ovarian cancer, the current status of ovarian cancer markers, as well as general information about mucins, the putative role of mucins in the progression of ovarian cancer and their potential use for the early diagnosis and treatment of this disease.

Current status of mucins in the diagnosis and therapy of cancer

Mucins are the most abundant high molecular weight glycoproteins in mucus. Their nature and glycosylation content dictates the biochemical and biophysical properties of viscoelastic secretions, pointing out an important role in diverse biological functions, such as differentiation, cell adhesions, immune responses, and cell signaling. Mucins are expressed in tubular organs by specialized epithelial cells in the body. Their aberrant expression is well documented in a variety of inflammatory or malignant diseases. From a prognosis point of view, their expression and alterations in glycosylation are associated with the development and progression of malignant diseases. Therefore, mucins can be used as valuable markers to distinguish between normal and disease conditions. Indeed, this alteration in glycosylation patterns generates several epitopes in the oligosaccharide side chains that can be used as diagnostic and/or prognostic markers. Furthermore, these characteristic tumor-associated epitopes are extensively used as appropriate immunotargets of malignant epithelial cells. Therefore, in an effort to detect and treat cancer at the earliest stage possible, mucins are analyzed as potential markers of disease for diagnosis, progression, and for therapeutic purposes. In this review, we focused on the current status of the distribution of mucins in normal and pathologic conditions and their clinical use both in cancer diagnosis and therapeutics treatments.

Mucin 1 (MUC1) is a novel partner for MAL2 in breast carcinoma cells

BACKGROUND

The MAL2 gene, encoding a four-transmembrane protein of the MAL family, is amplified and overexpressed in breast and other cancers, yet the significance of this is unknown. MAL-like proteins have trafficking functions, but their molecular roles are largely obscure, partly due to a lack of known binding partners.

METHODS

Yeast two-hybrid screening of a breast carcinoma cDNA expression library was performed using a full-length MAL2 bait, and subsequent deletion mapping experiments were performed. MAL2 interactions were confirmed by co-immunoprecipitation analyses and confocal microscopy was employed to compare protein sub-cellular distributions. Sucrose density gradient centrifugation of membranes extracted in cold Triton X-100 was employed to compare protein distributions between Triton X-100-soluble and -insoluble fractions.

RESULTS

The tumor-associated protein mucin 1 (MUC1) was identified as a potential MAL2 partner, with MAL2/MUC1 interactions being confirmed in myc-tagged MAL2-expressing MCF-10A cells using co-immunoprecipitation assays. Deletion mapping experiments demonstrated a requirement for the first MAL2 transmembrane domain for MUC1 binding, whereas the MAL2 N-terminal domain was required to bind D52-like proteins. Confocal microscopy identified cytoplasmic co-localisation of MUC1 and MAL2 in breast cell lines, and centrifugation of cell lysates to equilibrium in sucrose density gradients demonstrated that MAL2 and MUC1 proteins were co-distributed between Triton X-100-soluble and -insoluble fractions. However co-immunoprecipitation analyses detected MAL2/MUC1 interactions in Triton X-100-soluble fractions only. Myc-MAL2 expression in MCF-10A cells was associated with both increased MUC1 detection within Triton X-100-soluble and -insoluble fractions, and increased MUC1 detection at the cell surface.

CONCLUSION

These results identify MUC1 as a novel MAL2 partner, and suggest a role for MAL2 in regulating MUC1 expression and/or localisation.

Expression and functions of transmembrane mucin MUC13 in ovarian cancer

MUC13, a transmembrane mucin, is normally expressed in gastrointestinal and airway epithelium. Its aberrant expression has been correlated with gastric colon and cancer. However, the expression and functions of MUC13 in ovarian cancer are unknown. In the present study, the expression profile and functions of MUC13 were analyzed to elucidate its potential role in ovarian cancer diagnosis and pathogenesis. A recently generated monoclonal antibody (clone PPZ0020) was used to determine the expression profile of MUC13 by immunohistochemistry using ovarian cancer tissue microarrays and 56 additional epithelial ovarian cancer (EOC) samples. The expression of MUC13 was significantly (P < 0.005) higher in cancer samples compared with the normal ovary/benign tissues. Among all ovarian cancer types, MUC13 expression was specifically present in EOC. For the functional analyses, a full-length MUC13 gene cloned in pcDNA3.1 was expressed in a MUC13 null ovarian cancer cell line, SKOV-3. Here, we show that the exogenous MUC13 expression induced morphologic changes, including scattering of cells. These changes were abrogated through c-Jun NH(2) kinase (JNK) chemical inhibitor (SP600125) or JNK2 siRNA. Additionally, a marked reduction in cell-cell adhesion and significant (P < 0.05) increases in cell motility, proliferation, and tumorigenesis in a xenograft mouse model system were observed upon exogenous MUC13 expression. These cellular characteristics were correlated with up-regulation of HER2, p21-activated kinase 1, and p38 protein expression. Our findings show the aberrant expression of MUC13 in ovarian cancer and that its expression alters the cellular characteristics of SKOV-3 cells. This implies a significant role of MUC13 in ovarian cancer.

Clinical potential of mucins in diagnosis, prognosis, and therapy of ovarian cancer

Knowledge of mucins and their multiple roles in various normal and pathological processes has improved greatly in the past two decades. Mucins belong to a family of glycoproteins characterised by densely O-glycosylated repetitive domains and expressed by various surface epithelial cells. Altered expression of mucins is present in various diseases, including cancer. Ovarian cancer is the sixth most common cancer worldwide and the seventh leading cause of cancer-related deaths in women. The most common ovarian cancer is epithelial ovarian carcinoma, which is characterised by few early symptoms, widespread peritoneal dissemination, and ascites at advanced stages that result in poor prognosis. After diagnosis, 5 year survival is only 35-45%. Therefore, improved strategies for early diagnosis and treatment are needed. Because of the surface epithelial origin of epithelial ovarian cancer, mucins are obvious biomolecules for investigation as markers for early diagnosis and as therapeutic targets. We discuss the potential role and clinical usefulness of mucins in early diagnosis, prognosis, and treatment of ovarian cancer.

Expression of hepatocyte nuclear factor 4 alpha in primary ovarian mucinous tumors

Hepatocyte nuclear factor 4 alpha (HNF4 alpha) is a member of the nuclear receptor superfamily and is expressed in several endodermal tissues. The aim of the present study was to examine the expression of HNF4 alpha on ovarian epithelial tumors with immunocytochemistry and immunohistochemistry using mAbs recognizing P1 and P2 promoter-driven HNF4 alpha. Ovarian mucinous adenoma, mucinous tumors of borderline malignancy, and mucinous adenocarcinoma had positive nuclear staining for HNF4 alpha (41/45, 91%). One-third (34%) of mucinous tumors had P1-positive staining and most had P1/P2-positive staining (93%). MUC2- and MUC5AC-positive staining was observed in 34% and 95% of mucinous tumors, respectively. The histological subtype of these mucinous tumors was not correlated with HNF4 alpha expression. On cytology it was found that cancer cells in the ascites from ovarian mucinous adenocarcinomas were HNF4 alpha positive, but tumor cells in ascites from other types of ovarian carcinomas were negative for HNF4 alpha. Thus, HNF4 alpha is demonstrated to be a useful marker for histological and cytological diagnosis of ovarian mucinous tumors.

DETECTION OF DISSEMINATED TUMOR CELLS IN PERIPHERAL BLOOD

Metastases are the major cause of cancer-related deaths in patients with solid epithelial malignancies, such as breast, colorectal and prostate carcinomas. Hematogenous spreading of tumor cells from a primary tumor can be considered as a crucial step in the metastasis cascade leading eventually to the formation of clinically manifest metastases. Consequently, as shown in recent studies, the detection of disseminated tumor cells in peripheral blood might be of clinical relevance with respect to individual patient prognosis and staging or monitoring of therapy. However, the rarity of disseminated tumor cells in peripheral blood renders the application of sensitive techniques mandatory for their detection. The emergence of highly sophisticated reverse transciptase-polymerase chain reaction (RT-PCR) assays, combining a preanalytical enrichment step with the assessment of multiple molecular tumor markers expressed in disseminated tumor cells, provides a powerful tool in detecting disseminated tumor cells with high sensitivity and specificity. This review will discuss currently used tumor markers as well as experimental means to enhance the sensitivity and specificity of RT-PCR assays to detect disseminated tumor cells in the peripheral blood of patients with breast, colorectal, and prostate cancers, and their clinical relevance assessed in recent studies.

MUC1 and the MUCs: A Family of Human Mucins with Impact in Cancer Biology

Mucins represent a family of glycoproteins characterized by repeat domains and a dense O-glycosylation. During the last two decades, the gene and peptide structures of various mucins as well as their glycosylation states were partly elucidated. Characteristic tumor-associated alterations of the expression patterns and glycosylation profiles were observed in biochemical, immunochemical, and histological studies and are discussed in the light of efforts to use the most prominent member in this family, MUC1, as a tumor target in anti-tumor strategies. Within this context the present review, focusing on MUC1, describes recent work on the regulation of mucin biosynthesis by cytokines and hormones, the role of mucins in cell adhesion, and their interaction with the immune system. Important aspects of clinical diagnostics based on mucin antigens are discussed, including the application of tumor serum assays and the significance of numerous studies revealing correlations between the expression of peptide cores or mucin-associated carbohydrates and clinicopathological parameters like tumor progression and prognosis.

Induction of IgG antibodies to MUC1 and survival in patients with epithelial ovarian cancer

We investigated whether epithelial ovarian cancer patients participating in a randomized phase III trial comparing single intraperitoneal (IP) administration of yttrium-90-labeled murine HMFG1 ((90)Y-muHMFG1) plus standard treatment (AT) vs. standard treatment (ST) alone developed IgG ab to MUC1 that had an impact on disease outcome. Serial serum samples from 208 patients in the AT and 199 patients in the ST arm were tested for IgG ab to MUC1 (anti-MUC1 IgG). Anti-MUC1 IgG at weeks 4, 8 and 12 ranked higher in the AT than in the ST arm (p < 0.001). The median (range) area under the curve (AUC) of anti-MUC1 IgG for weeks 1 to 12 was 5.53 (1.51-39.51) and 3.92 (1.17-68.74) for the AT and ST arm, respectively (p < 0.001). An anti-MUC1 IgG AUC > 13 was associated with a benefit in overall survival (OS) and disease-free survival (DFS) in the AT arm in univariate (p = 0.043 and 0.036, respectively), but not in multivariate analysis (Cox proportional hazards regression model). Kaplan-Meier analysis showed a benefit in OS and DFS in patients with an anti-MUC1 IgG AUC > 13 in the AT arm (p = 0.043 and 0.036, respectively), but not in the ST arm. A single IP injection with muHMFG1 did not lead to a survival benefit in the randomized trial, but it induced ab to MUC1 that were associated with an improved disease outcome in patients with highest levels of anti-MUC1 IgG. Immunotherapy against MUC1 could be effective in the treatment of epithelial ovarian cancer.