MUC6 expression in breast tissues and cultured cells: abnormal expression in tumors and regulation by steroid hormones

Mucins as contrast agent targets for fluorescence-guided surgery of pancreatic cancer

Pancreatic cancer is difficult to resect due to its unique challenges, often leading to incomplete tumor resections. Fluorescence-guided surgery (FGS), also known as intraoperative molecular imaging and optical surgical navigation, is an intraoperative tool that can aid surgeons in complete tumor resection through an increased ability to detect the tumor. To target the tumor, FGS contrast agents rely on biomarkers aberrantly expressed in malignant tissue compared to normal tissue. These biomarkers allow clinicians to identify the tumor and its stage before surgical resection and provide a contrast agent target for intraoperative imaging. Mucins, a family of glycoproteins, are upregulated in malignant tissue compared to normal tissue. Therefore, these proteins may serve as biomarkers for surgical resection. Intraoperative imaging of mucin expression in pancreatic cancer can potentially increase the number of complete resections. While some mucins have been studied for FGS, the potential ability to function as a biomarker target extends to the entire mucin family. Therefore, mucins are attractive proteins to investigate more broadly as FGS biomarkers. This review summarizes the biomarker traits of mucins and their potential use in FGS for pancreatic cancer.

Unsupervised Learning Framework With Multidimensional Scaling in Predicting Epithelial-Mesenchymal Transitions

Clustering tumor metastasis samples from gene expression data at the whole genome level remains an arduous challenge, in particular, when the number of experimental samples is small and the number of genes is huge. We focus on the prediction of the epithelial-mesenchymal transition (EMT), which is an underlying mechanism of tumor metastasis, here, rather than tumor metastasis itself, to avoid confounding effects of uncertainties derived from various factors. In this paper, we propose a novel model in predicting EMT based on multidimensional scaling (MDS) strategies and integrating entropy and random matrix detection strategies to determine the optimal reduced number of dimension in low dimensional space. We verified our proposed model with the gene expression data for EMT samples of breast cancer and the experimental results demonstrated the superiority over state-of-the-art clustering methods. Furthermore, we developed a novel feature extraction method for selecting the significant genes and predicting the tumor metastasis. The source code is available at "https://github.com/yushanqiu/yushan.qiu-szu.edu.cn".

Systematic analysis of somatic mutations driving cancer: uncovering functional protein regions in disease development

Background

Recent advances in sequencing technologies enable the large-scale identification of genes that are affected by various genetic alterations in cancer. However, understanding tumor development requires insights into how these changes cause altered protein function and impaired network regulation in general and/or in specific cancer types.

Results

In this work we present a novel method called iSiMPRe that identifies regions that are significantly enriched in somatic mutations and short in-frame insertions or deletions (indels). Applying this unbiased method to the complete human proteome, by using data enriched through various cancer genome projects, we identified around 500 protein regions which could be linked to one or more of 27 distinct cancer types. These regions covered the majority of known cancer genes, surprisingly even tumor suppressors. Additionally, iSiMPRe also identified novel genes and regions that have not yet been associated with cancer.

Conclusions

While local somatic mutations correspond to only a subset of genetic variations that can lead to cancer, our systematic analyses revealed that they represent an accompanying feature of most cancer driver genes regardless of the primary mechanism by which they are perturbed during tumorigenesis. These results indicate that the accumulation of local somatic mutations can be used to pinpoint genes responsible for cancer formation and can also help to understand the effect of cancer mutations at the level of functional modules in a broad range of cancer driver genes.

Reviewers

This article was reviewed by Sándor Pongor, Michael Gromiha and Zoltán Gáspári.

Electronic supplementary material

The online version of this article (doi:10.1186/s13062-016-0125-6) contains supplementary material, which is available to authorized users.

Lynch syndrome-associated breast cancers do not overexpress chromosome 11-encoded mucins

Mismatch repair-deficient breast cancers may be identified in Lynch syndrome mutation carriers, and have clinicopathological features in common with mismatch repair-deficient colorectal and endometrial cancers such as tumour-infiltrating lymphocytes and poor differentiation. Mismatch repair-deficient colorectal cancers frequently show mucinous differentiation associated with upregulation of chromosome 11 mucins. The aim of this study was to compare the protein expression of these mucins in mismatch repair-deficient and -proficient breast cancers. Cases of breast cancer (n=100) were identified from families where (1) both breast and colon cancer co-occurred and (2) families met either modified Amsterdam criteria or had at least one early-onset (<50 years) colorectal cancer. Tumour sections were stained for the epithelial mucins, MUC2, MUC5AC, MUC5B and MUC6, and the homeobox protein CDX2, a regulator of MUC2 expression. In all, 16 mismatch repair-deficient Lynch syndrome breast cancers and 84 non-Lynch breast cancers were assessed for altered mucin expression. No significant difference in the expression of MUC2, MUC5AC or MUC6 was observed between the mismatch repair-deficient and mismatch repair-proficient breast cancers; however, there was a trend for mismatch repair-deficient tumours to express high levels of MUC5B less frequently (P=0.07, OR=0.2 (0.0-1.0)). Co-expression of two or more gel-forming mucins was common. Ectopic expression of CDX2 was associated with expression of MUC2 (P=0.035, OR=8.7 (1.3-58.4)). Mismatch repair-deficient breast cancers do not show differential expression of the mucins genes on chromosome 11 when compared with mismatch repair-proficient breast cancers, in contrast with mismatch repair-deficient colorectal and endometrial cancers, which frequently have increased mucin protein expression when compared with their mismatch repair-proficient counterparts. In addition, ectopic CDX2 expression is positively associated with de novo MUC2 expression.

Monoclonal antibodies toward different Tn-amino acid backbones display distinct recognition patterns on human cancer cells. Implications for effective immuno-targeting of cancer

The Tn antigen (GalNAcα-O-Ser/Thr) is a well-established tumor-associated marker which represents a good target for the design of anti-tumor vaccines. Several studies have established that the binding of some anti-Tn antibodies could be affected by the density of Tn determinant or/and by the amino acid residues neighboring O-glycosylation sites. In the present study, using synthetic Tn-based vaccines, we have generated a panel of anti-Tn monoclonal antibodies. Analysis of their binding to various synthetic glycopeptides, modifying the amino acid carrier of the GalNAc(*) (Ser* vs Thr*), showed subtle differences in their fine specificities. We found that the recognition of these glycopeptides by some of these MAbs was strongly affected by the Tn backbone, such as a S*S*S* specific MAb (15G9) which failed to recognize a S*T*T* or a T*T*T* structure. Different binding patterns of these antibodies were also observed in FACS and Western blot analysis using three human cancer cell lines (MCF-7, LS174T and Jurkat). Importantly, an immunohistochemical analysis of human tumors (72 breast cancer and 44 colon cancer) showed the existence of different recognition profiles among the five antibodies evaluated, demonstrating that the aglyconic part of the Tn structure (Ser vs Thr) plays a key role in the anti-Tn specificity for breast and colon cancer detection. This new structural feature of the Tn antigen could be of important clinical value, notably due to the increasing interest of this antigen in anticancer vaccine design as well as for the development of anti-Tn antibodies for in vivo diagnostic and therapeutic strategies.

MUC6 mucin expression inhibits tumor cell invasion

The MUC6 mucin has a critical protective function in the normal stomach, pancreas and duodenum and is aberrantly expressed during the progression of some gastrointestinal cancers. Our aim was to determine whether MUC6 contributes to the etiology or progression of pancreatic cancer and elucidate the molecular basis of its involvement. Expression of MUC6 glycoprotein was examined in pancreatic cancer tissues by immunofluorescence and loss of MUC6 was observed. Next, to determine whether MUC6 inhibits tumor growth and metastasis by altering cell adhesion and invasion, recombinant MUC6 cDNA and separate MUC6 N-terminal and C-terminal domains were transfected into pancreatic, colorectal and breast cancer cell lines. The recombinant N- and C-terminal proteins were each seen to oligomerize under non-reducing conditions. Overexpression of both domains of the MUC6 glycoprotein significantly inhibited cell adhesion to matrix proteins (collagen I, collagen IV, fibronectin and laminin) in LS 180 but not in PANC-1 cells. Moreover, the N- and C-terminal domains of MUC6 inhibited invasion of both LS 180 and PANC-1 cells by 40% and 70%, respectively, in comparison with controls. These results suggest that MUC6 may inhibit invasion of tumor cells through the basement membrane of the pancreatic duct and slow the development of infiltrating carcinoma.

Mucins in the pathogenesis of breast cancer: implications in diagnosis, prognosis and therapy

Mucins are high molecular weight, multifunctional glycoproteins comprised of two structural classes-the large transmembrane mucins and the gel-forming or secreted mucins. The primary function of mucins is to protect and lubricate the luminal surfaces of epithelium-lined ducts in the human body. Recent studies have identified a differential expression of both membrane bound (MUC1, MUC4 and MUC16) and secreted mucins (MUC2, MUC5AC, MUC5B and MUC6) in breast cancer tissues when compared with the non-neoplastic breast tissues. Functional studies have also uncovered many unique roles of mucins during the progression of breast cancer, which include modulation in proliferative, invasive and metastatic potential of tumor cells. Mucins function through many unique domains that can form complex association with various signaling molecules including growth factor receptors and intercellular adhesion molecules. While there is growing information about mucins in various malignancies including breast cancer, no focused review is there on the expression and functional roles of mucins in breast cancer. In this present review, we have discussed the differential expression and functional roles of mucins in breast cancer. The potential of mucins as diagnostic and prognostic markers and as therapeutic targets in breast cancer have also been discussed.

Low-grade salivary duct carcinoma of the parotid gland: report of a case with immunohistochemical analysis

Salivary duct carcinoma (SDC) is a highly aggressive malignancy of the salivary glands. However, one type of SDC, which shows minimal invasion and better prognosis, is known as low-grade SDC (LG-SDC). This report presents an additional case of LG-SDC of the parotid gland. The patient was a 38-year-old Japanese woman who noticed painless swelling of the left parotid region. Grossly, the cut surface of the tumor was cystic. Microscopically, the tumor showed a multicystic pattern, which was lined by eosinophilic to clear atypical cells with cribriform or Roman bridge patterns. An immunohistochemical examination revealed the tumor was positive for cytokeratin (CK) 7 and epithelial membrane antigen, partially positive for androgen receptor and gross cystic disease fluid protein-15, and diffusely positive for Her-2/Neu, progesterone, and estrogen receptors. The cancer cells showed focal immunopositivity for S-100 protein. Immunostaining for p63, CK14, and calponin showed an in situ pattern in most areas of this tumor, whereas the tumor showed minimal invasion. The cancer cells were diffusely positive for MUC1 and MUC6 and focally positive for MUC2 and MUC4. Finally, the tumor was diagnosed to be LG-SDC. The differential diagnosis and the mucin pattern were evaluated.

Mucin genes have different expression patterns in healthy and diseased upper airway mucosa

BACKGROUND

Mucus hyper-secretion is a feature of several airways diseases such as chronic rhinosinusitis, asthma, and cystic fibrosis (CF). Since mucins are major components of mucus, the knowledge of their distribution and regulation in nasal tissues is likely to improve mucus hyper-secretion therapy.

OBJECTIVE

The aim of this study was to evaluate and compare mucin gene expression at epithelial and glandular levels, and to identify potential mucin expression patterns for specific upper airways pathologies.

METHODS

Immunohistochemistry for MUC1, MUC2, and MUC4-MUC8 mucins was performed on healthy nasal mucosa (NM; n=12), bilateral nasal polyps (NP; n=38), NP from CF patients (n=10), and antrochoanal (AC) polyps (n=11). MUC2, MUC4, MUC5AC, and MUC6 mRNA expression were also analysed by in situ hybridization.

RESULTS

MUC1, MUC4, and MUC5AC mucins were highly expressed in the epithelium and their expression pattern was similar in all NP types, MUC1 and MUC4 being increased and MUC5AC decreased compared with NM. MUC8 was highly detected at both epithelial and glandular levels with marked variability between groups. MUC5B was mainly detected in glands and the expression in all polyp types was higher than in NM. Moreover, MUC5B expression was higher in NP epithelia from CF patients than in bilateral NP and healthy NM. Although MUC2 expression was low, especially in AC polyps, it was detected in most samples. In NM, MUC6 and MUC7 were scarcely detected and MUC7 expression was restricted to glands.

CONCLUSIONS

These results suggest that NP have a different pattern of mucin expression than healthy NM and that CF polyps (increased MUC5B) and AC polyps (decreased MUC2) have a different mucin expression pattern than bilateral NP.

High expression of RELP (Reg IV) in neoplastic goblet cells of appendiceal mucinous cystadenoma and pseudomyxoma peritonei

The regenerating protein (Reg)-like protein (RELP, also known as Reg IV) is a recently characterized fourth member of the human Reg protein family. The Reg proteins are small, about 20-kD-sized, secretory proteins of C-lectin type. The previously known Reg proteins have been functionally implicated in regeneration, proliferation, and differentiation of the pancreas, liver, and gastrointestinal mucosa. To study the tissue expression of RELP, we raised a monoclonal antibody to RELP. By immunohistochemistry and in situ hybridization, we found a robust de novo expression of RELP in the neoplastic goblet cells of appendiceal mucinous cystadenomas and in the epithelial implants of pseudomyxoma peritonei (PMP). Our findings indicate that RELP serves as a marker for appendiceal mucinous cystadenomas and PMP, and that RELP may contribute to the pathogenesis of these disorders.

Expression of mucins (MUC1, MUC2, MUC3, MUC4, MUC5AC and MUC6) and their prognostic significance in human breast cancer

Mucins are a large family of glycoproteins expressed by many epithelial cells and their malignant counterparts. Much interest has been focused on expression of its members in breast cancer because of their potential role as prognostic indicators and their involvement in cancer therapy. We have examined 1447 cases of invasive breast carcinoma with a long-term follow-up, using tissue microarray (TMA) technology and immunohistochemistry to evaluate the expression profiles of several mucins (MUC1, MUC2, MUC3, MUC4, MUC5AC and MUC6) and to assess their prognostic value. We detected MUC1 expression in 91% of tumours. MUC1 overexpression was associated with a lower grade, smaller tumour size, a higher oestrogen receptor (ER)-positive phenotype and absence of both regional recurrence and distance metastasis. The subcellular localization but not the level of expression had a prognostic value in predicting outcome. The aberrant cytoplasmic and membranous localization of MUC1 was associated with poor outcome compared with apical localization, which is the normal physiological site of expression. MUC2 expression was noticed in only 8.3% of all cases and was restricted to the cytoplasm of the tumour cells. An inverse trend was identified between MUC2 expression and lymph node stage and vascular invasion status. On excluding cases of mucinous carcinoma from the analysis, the inverse association with vascular invasion was still defined and in addition an inverse association with ER status emerged. MUC3 expression was detected in 91% of cases and its expression was associated with increased local recurrence, and lymph node stage. The membranous expression of MUC3 was found to be a potentially poor prognostic feature, with higher grade and poorer Nottingham Prognostic Index (NPI), and negative ER expression. MUC4, MUC5AC and MUC6 were expressed in 95, 37 and 20% of cases, respectively. Apart from an association between MUC4 expression and tumour grade and between MUC6 and ER-negative tumours, no other associations with any clinicopathological variables were found. Apart from the higher expression of MUC2 and MUC6 in mucinous carcinomas, no association was found between the expression of different mucins and tumour type. No association between the level of expression of any of the studied mucins and patient outcomes has been identified. In conclusion, most breast carcinomas express MUC1, MUC3 and MUC4. Among the various mucins expressed in breast cancer, MUC1 and MUC3 are potential prognostic indicators, MUC1 having the strongest relationship with patient outcome.

Immunohistochemical analysis of MUC5B apomucin expression in breast cancer and non-malignant breast tissues

A deregulation of several MUC genes (MUC1, MUC2, MUC3, MUC5AC, and MUC6) was previously demonstrated in breast carcinomas. Considering that recently we found the "non-mammary" MUC5B mRNA in primary breast tumors (Berois et al. 2003), we undertook the present study to evaluate the expression profile of MUC5B protein product in breast tissues, using LUM5B-2 antisera raised against sequences within the non-glycosylated regions of this apomucin. Expression of MUC5B by breast cancer cells was confirmed by immunocytochemistry, in situ hybridization, and Western blot on MCF-7 cancer cells. Using an immunohistochemical procedure, MUC5B apomucin was detected in 34/42 (81%) primary breast tumors, in 13/14 (92.8%) samples of non-malignant breast diseases, in 8/19 (42.1%) samples of normal-appearing breast epithelia adjacent to cancer, and in 0/5 normal control breast samples. The staining pattern of MUC5B was very different when comparing breast cancer cells (cytoplasmic) and non-malignant breast cells (predominantly apical and in the secretory material). We analyzed MUC5B mRNA expression using RT-PCR in bone marrow aspirates from 22/42 patients with breast cancer to compare with MUC5B protein expression in the primary tumors. Good correlation was observed because the six MUC5B-positive bone marrow samples also displayed MUC5B expression in the tumor. Our results show, for the first time at the protein level, that MUC5B apomucin is upregulated in breast cancer. Its characterization could provide new insights about the glycobiology of breast cancer cells.

Molecular Basis of Incomplete O-Glycan Synthesis in MCF-7 Breast Cancer Cells: Putative Role of MUC6 in Tn Antigen Expression

An incomplete elongation of O-glycan saccharide chains in mucins have been found in epithelial cancers, leading to the expression of shorter carbohydrate structures, such as the Tn antigen (GalNAc-O-Ser/Thr). This antigen is one of the most specific human cancer-associated structures and is capable of inducing effective immune responses against cancer cells. We aimed to investigate the causes of the expression of Tn antigen in the Tn-rich MCF-7 breast cancer cell line focusing on the first step of the O-glycosylation process. Interestingly, amino acid sequences derived from "non-mammary" apomucins (MUC5B and MUC6) were very good acceptor substrates for ppGalNAc-Ts, which are the enzymes catalyzing the Tn antigen synthesis. MUC6 peptide glycosylation with MCF-7 microsome extracts as source of ppGalNAc-T activity yielded 95% conversion of the peptide into MUC6-Tn. In addition, the MUC6-Tn glycopeptide was a poor acceptor substrate for core 1 beta3Gal-T, the next enzyme involved in the saccharide chain biosynthesis, yielding only 5% conversion of MUC6-Tn into MUC6-TF. These results indicate that non-mammary apomucin expression could be responsible, at least in part, for Tn antigen expression in MCF-7 breast cancer cells due to a combined action on glycosyltransferases: an increase of ppGalNAc-T activity and a decrease of core 1 beta3Gal-T activity. Our hypothesis is supported by experiments in vivo showing that (a) native MUC6 glycoproteins express the Tn antigen in MCF-7 cells and (b) Tn antigen expression is increased after transfection with a construct encoding for a MUC6 recombinant protein into the low Tn-expressing breast cancer cell T47D. These results open new horizons in breast cancer glycoimmunology, stressing the potential role of non-mammary apomucins.

Expression of Membrane-Bound Mucins (MUC1 and MUC4) and Secreted Mucins (MUC2, MUC5AC, MUC5B, MUC6 and MUC7) in Mucoepidermoid Carcinomas of Salivary Glands

Mucins are glycoproteins normally synthesized by a variety of secretory epithelial cells. The aim of this study was to investigate the expression of mucins (MUC1, MUC2, MUC4, MUC5AC, MUCB, MUC6, MUC7) in mucoepidermoid carcinomas, the most frequent malignant tumor of salivary glands. Forty mucoepidermoid carcinomas and twenty-two normal salivary glands were studied for these mucins by immunohistochemistry from formalin-fixed and paraffin-embedded material. Normal salivary glands frequently expressed MUC1 and MUC4, mainly in ductal cells; MUC5B and MUC7 stained mucous and serous acini respectively of submandibular and minor salivary glands; and MUC5AC and MUC2 were poorly detected in excretory ducts. All mucoepidermoid carcinomas expressed MUC1, and 38/40 tumors expressed MUC4. Both membrane-bound mucins stained membranes and cytoplasm of all cell types (epidermoid, intermediate, mucous, clear and columnar). MUC5AC and MUC5B stained glandular differentiated cells in most tumors (29/40 and 33/40 cases, respectively). MUC6 was positive in 13/40 tumors, and both MUC2 and MUC7 in only 2/40 tumors. The high expression of MUC1 was related to high histologic grades, high recurrence and metastasis rates and a shorter disease-free interval (P < 0.05). Conversely, MUC4 high expression was mainly related to low-grade tumors, lower recurrence rates and a longer disease-free interval (P < 0.05). In conclusion, mucoepidermoid carcinomas of salivary glands usually express MUC1, MUC4, MUC5AC and MUC5B; less frequently MUC6; and rarely MUC2 and MUC7. This mucin expression pattern can be useful for diagnostic purposes. Therefore, MUC1 expression is related to tumor progression and worse prognosis, whereas MUC4 expression is related to a better prognosis.

MUC3 and MCA serum levels and steroid receptor content in breast cancer

Mucins are an important class of complex glycoproteins expressed by many epithelial cells and their malignant counterparts. The aim of this study was to determine the serum levels of MUC3 and mucin-like carcinoma-associated antigen (MCA) in patients with primary breast cancer and to analyze the possible relationships between these two mucins and the steroid receptor status. The preoperative basal serum levels of MUC3 (ELISA assay with monoclonal antibody 1143/B7) and MCA (EIA assay with anti-MCA mouse monoclonal antibody b-12) were determined in 44 patients with breast cancer while estrogen receptor (ER) and progesterone receptor (PgR) levels were measured by the dextran-coated charcoal method in the cytosol of neoplastic tissue. MUC3 was expressed in 43/44 serum samples while high MCA serum levels were found in 16/44 only; the mean values of both markers did not correlate with menopausal status, tumor size, nodal involvement or ER. The only significant difference observed was a lower median value of MCA in patients with small tumors (T1-T2). No statistically significant correlation between MUC3 and MCA, MUC3 and ER or MCA and ER was observed; a statistically significant direct correlation between MUC3 and PgR+ status and a statistically significant inverse correlation between MCA and PgR+ were observed. Our results suggest that further investigations are necessary to establish whether progesterone can modulate MUC3 and MCA expression in breast cancer.

Immunohistochemical evaluation of immune response in invasive ductal breast cancer of not-otherwise-specified type

We investigated endotumoral and peritumoral lymphocytic subsets [natural killer cells (NK), B-cells and cytotoxic/suppressor (CD(8)+) T-cells], and expression of MUC1 and MUC6 glycoprotein with regard to various clinicopathological parameters in invasive breast cancer tissues. The study population consisted of 64 female patients with invasive ductal breast cancer of not-otherwise-specified type. Thirty-five women with benign breast lesions served as controls. High-grade carcinomas exhibited higher numbers of endotumoral NK cells and B-cell aggregates than the rest of the tumors examined (P=0.0003 and 0.027, respectively). Cases with more than three positive lymph nodes and with tumors over 2 cm in diameter exhibited higher numbers of endotumoral NK cells (P=0.047 and 0.023, respectively). Increased numbers of peritumoral CD(8)+ T-cells were detected in cases with lymph node metastases (P=0.045). MUC1 was expressed with weaker staining intensity in the control group than in the group with breast cancer (P=0.011). Grade III carcinomas exhibited significantly stronger expression of MUC6 glycoprotein (P=0.001) than the control group. In conclusion, tumors with markers of poor prognosis exhibited increased numbers of lymphocytic infiltrates, and of NK cells in particular, and stronger MUC1 and MUC6 glycoprotein immunoreactivity than did the other tumors.

Mucin-rich variant of salivary duct carcinoma: a clinicopathologic and immunohistochemical study of four cases

Salivary duct carcinoma is a relatively uncommon aggressive neoplasm, typically found in the parotid glands of older men. The histologic appearance is that of an in situ and invasive high-grade adenocarcinoma, and it closely resembles ductal carcinoma of the breast. Several variants of the latter are very well known, but only papillary, sarcomatoid, and low-grade subtypes have so far been reported in salivary duct carcinoma. This study describes the clinicopathologic and immunohistochemical findings in four examples of an additional previously undescribed variant, rich in mucin. Each tumor showed areas of typical salivary duct carcinoma, but in addition there were lakes of epithelial mucin-containing malignant cells, i.e., mucinous (colloid) carcinoma. All four tumors expressed androgen receptors, cytokeratins, epithelial membrane antigen, gross cystic disease fluid protein-15, and carcinoembryonic antigen, but S-100 protein, other myoepithelial markers, and estrogen and progesterone receptors were negative. The mucin antigen profile showed positivity for MUC2, MUC5B, and MUC6 in all cases but only rare staining with MUC5AC and MUC7. Strong immunohistochemical overexpression of HER2/neu was demonstrated in one tumor, together with amplification by fluorescence in situ hybridization; another case was weakly positive with just one antiserum, but the remaining two tumors were completely negative. Small quantities of mucin have often been described in salivary duct carcinoma but not large extracellular mucinous lakes, which though prominent in the present series, were not as extensive as in mucinous adenocarcinoma. The relatively poor clinical outcome of the patients in our study mirrored that seen in usual-type salivary duct carcinoma and emphasizes the importance of differentiating mucin-rich salivary duct carcinoma from pure mucinous (colloid) adenocarcinoma, a tumor not fully defined, but possibly with a better prognosis.

Detection of bone marrow-disseminated breast cancer cells using an RT-PCR assay of MUC5B mRNA

The evaluation of disseminated epithelial tumor cells in breast cancer patients has generated considerable interest due to its potential association with disease recurrence. Our work was performed to analyze the usefulness of 5 mucin genes expression (MUC2, MUC3, MUC5B, MUC6 and MUC7), using RT-PCR assays, to detect disseminated cancer cells in patients with operable breast cancer. The highest frequencies of positive RT-PCR tests in breast tumor extracts were observed for MUC5B (7/15) and MUC7 (5/12). The best specificity, negative results on all peripheral blood mononuclear (PBMN) cell samples from healthy donors, were shown for MUC2, MUC5B and MUC6 RT-PCR assays. Thus, we selected MUC5B as a target gene for further evaluation. Using a nested RT-PCR, MUC5B mRNA transcripts were detected in 16/31 primary breast tumors (but not in 36 samples of normal PBMN cells) and in the human MCF-7 breast cancer cell line but not in BT20, MDA, T47D and ZR-75 breast cancer cell lines, indicating that MUC5B mRNA is expressed in a population of breast cancer cells. Using this method, 9/46 patients (19.5%) who underwent curative surgery showed positive MUC5B mRNA in bone marrow aspirates obtained prior to surgery, including 5/24 patients (20.8%) with stage I or II breast cancer, without histopathologic lymph node involvement. These results indicate that MUC5B mRNA could be a specific marker applicable to the molecular diagnosis of breast cancer cell dissemination. A comparative evaluation between MUC5B mRNA, cytokeratin 19 (CK19) mRNA and carcinoembryonic antigen (CEA) mRNA in all bone marrow aspirates suggests a putative complementation for molecular detection of disseminated carcinoma cells. Considering that breast cancer is characterized by a great phenotypic heterogeneity, the use of multimarker approach could contribute to tumor cell detection in bone marrow and blood.

Expression of human mucin genes in normal kidney and renal cell carcinoma

AIMS

Human mucins are large O-glycoproteins expressed by epithelial cells. Mucins are thought to be implicated in cell protection, cell adhesion and signalling. The aim of this study was to investigate the expression of the human mucin genes (MUC1-4, 5AC, 5B, 6-7) in normal kidney and renal cell carcinoma.

METHODS AND RESULTS

We analysed by in-situ hybridization, immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR) the expression of these genes in normal adult kidney (n=14) and renal cell carcinomas (n=29). MUC1, MUC3 and MUC6 were expressed both in normal kidney and in renal carcinomas. In normal kidney, MUC1 was expressed in the distal convoluted tubules and in collecting ducts, whereas MUC3 was restricted to the proximal tubules. MUC4 was strongly expressed in epithelial urothelial cells of pyelocalyceal cavities. MUC6 was only detected by RT-PCR. In renal carcinoma, we showed a heterogeneous expression of MUC1 and MUC3 with an over-expression of MUC3 in renal clear cell carcinoma. The level of MUC3 expression by in-situ hybridization was associated with the nuclear grade in clear cell carcinoma.

CONCLUSIONS

This study is the first large series investigating human mucin gene expression in the kidney. MUC1, MUC3 and MUC6 are expressed in normal and tumour kidney. The over-expression of MUC3 in renal cell carcinomas favours its implication in renal tumorigenesis.

Sialomucin complex (rat Muc4) transmembrane subunit binds the differentiation marker peanut lectin in the normal rat mammary gland

Sialomucin complex (SMC, rat Muc4) is a heterodimeric glycoprotein composed of two subunits, the mucin component ASGP-1 and the transmembrane subunit ASGP-2. SMC/Muc4 is highly expressed on the surface of 13762 rat mammary adenocarcinoma cells at approximately 100 times the level found in the lactating mammary gland. Immunocytochemical staining of SMC/Muc4 in the developing rat mammary gland is localized to the apical membrane of the ductal epithelium. This staining pattern is similar to that for peanut lectin, a differentiation marker, which binds to cells expressing the disaccharide Thomsen-Friedenreich or TF antigen. Blotting of glycoproteins expressing the TF antigen from mammary tissues with peanut lectin detects a protein matching the migration of ASGP-2. Analysis of immunoprecipitated SMC/Muc4 by peanut lectin blotting shows that the TF antigen is abundantly present on the ASGP-2 subunit, hence the similarity of staining pattern with SMC/Muc4 antisera and peroxidase-conjugated lectin in mammary tissues. The TF antigen is also present on ASGP-2 of SMC/Muc4 produced by confluent cultures of Rama 37 rat mammary epithelial stem cells after their induction to an alveolar-like phenotype with prolactin. These results indicate that the TF antigen is present on the ASGP-2 transmembrane subunit of SMC/Muc4 from phenotypically normal tissues and cells, in contrast to malignant cells whose peanut lectin-binding disaccharide is located on ASGP-1.

Immunohistochemical study of the expression of MUC5AC and MUC6 in breast carcinomas and adjacent breast tissues

AIM

To study the protein expression patterns of MUC5AC and MUC6 in normal and diseased breast tissues and to compare their expression with that of a mucin (MUC1) normally expressed in mammary tissues.

METHODS

Formalin fixed, paraffin wax embedded tissue from 69 cases of invasive breast carcinoma and surrounding breast tissue was studied immunohistochemically with monoclonal antibodies against MUC1 (SM3), MUCSAC (CLH2), and MUC6 (CLH6), using the avidin-biotin-peroxidase method.

RESULTS

MUC5AC was detected in five of 68 cases of invasive carcinoma including one of three cases of pure colloid carcinoma. MUCSAC expression in the adjacent normal breast epithelium was present in one of 29 cases and in one of two cases of ductal carcinoma in situ. None of 15 cases of ductal hyperplasia without atypia was positive for MUCSAC. MUC6 was present in 15 of 65 cases of invasive carcinoma, in four of 29 cases of normal adjacent epithelium, two of 15 cases of ductal hyperplasia without atypia, and one of two cases of ductal carcinoma in situ. MUC1 immunoreactivity detected by the SM3 antibody was present in 50 of the 67 cases of invasive carcinoma, but expression was also detected in benign epithelium. All invasive carcinomas expressing MUCSAC were positive for MUC1 and four were positive for MUC6. No significant association was found between the expression of these mucins and tumour size, histological grade, node status, oestrogen receptor status, p53 positivity, or c-ErbB-2 overexpression.

CONCLUSIONS

This study documents the expression of two different mucins (MUCSAC and MUC6) not described as being expressed by normal breast tissues in a minority of breast carcinomas, as well as in normal and hyperplastic epithelium. Although the role of mucins in malignant transformation and the progression of breast cancer is not well understood, in some cases, there is probably an upregulation of several genes that encode distinct mucin proteins.

Mucins as differentiation markers in bronchial epithelium. Squamous cell carcinoma and adenocarcinoma display similar expression patterns

Highly glycosylated apomucins are important to maintain the viscoelastic properties of the mucus. Changes in their expression are frequently associated with inflammatory and neoplastic conditions. We analyzed the expression of apomucins in normal respiratory tract (n = 8) and compared it with distal, peritumoral, and tumoral epithelia from patients with squamous cell carcinoma (n = 20), adenocarcinoma (n = 13), and small cell carcinoma (n = 12). Squamous metaplasia (n = 16) was also analyzed. MUC1, MUC2, MUC4, MUC5AC, MUC6, and MUC8 apomucins were detected by immunohistochemistry, and mucin transcripts by in situ hybridization and reverse transcriptase polymerase chain reaction. Bronchial epithelium from normal individuals and distal epithelium from cancer patients showed a similar expression pattern: MUC1, MUC4, and MUC8 were always present, MUC2 and MUC5AC showed more variability, and MUC6 was focally detected. MUC5AC was downregulated in peritumoral epithelium and in squamous metaplasia, and MUC6 was upregulated in peritumoral epithelium. A reduced expression of MUC4, MUC5AC, and MUC8 was observed in non-small cell carcinomas, regardless of their histologic subtype. In small cell tumors, only MUC1 was consistently expressed.

CONCLUSIONS

(1) peritumoral epithelium and squamous metaplasia show an abnormal pattern of mucin expression; (2) squamous cell carcinomas and adenocarcinomas display a similar pattern of mucin gene expression, supporting the concept of a common cellular origin.

Prevention of breast cancer

With the advent of screening and the increased incidence of breast cancer, concern for the prevention of breast cancer has become forefront in today's society. Determining individual risk is the key to prescribing prevention. Prevention of breast cancer is still under clinical investigation with only one drug, tamoxifen, showing benefit in high risk patients. This paper reviews the possible sites for prevention of neoplastic transformation via biomarkers in a breast cell as well as the investigational drugs and their potential use in the chemoprevention of breast cancer.