Assessment of milk fat globule membrane antibodies and lectins as markers of short-term prognosis in breast cancer

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.

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

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

Pathogenesis of invasive micropapillary carcinoma: role of MUC1 glycoprotein

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

Characterization of lectins and their specificity in carcinomas-An appraisal

Lectins, a group of specific glycoproteins present in animal as well as plant cells, are used as differentiating markers to study cancers and metastatic cell lines. This property of lectins depends on the process of cellular glycosylation. Glycosylation of some of the extracellular membrane proteins and lipids maintains the cell/cell and cell/matrix interactions. Chemical alterations in glycosylation play an important role in the metastatic behavior of tumor cells. Carbohydrate residues of the membrane glycoproteins can be detected using lectins due to their binding specificity to carbohydrates. Lectins, therefore have gained an importance in the field of cancer research. Galectins, a specialized group of lectin like proteins that are Ca+ independent and galactoside binding, are also considered as differentiation markers in some specific cancers like the carcinomas of thyroid.Thus the use of lectins and galectins to identify specific carbohydrates present on cell surface help in invasion and metastasis processes.

EMA: a differentiation antigen related to node metastatic capacity of breast carcinomas

Epithelial membrane antigen (EMA), also known as MUC1, is a mucinous glycoprotein fixed to the luminal domain of the epithelial cell membrane of normal breast ducts. However, in breast cancer cells, it is usually dispersed in the cytoplasm. EMA staining patterns of 330 breast carcinomas were examined, and three groups formed: lineal (16%), cytoplasmic (75%), and negative (9%). Although these patterns were somewhat related to histological cancer types, this was not statistically significant. However, EMA showed statistically significant univariate relationships to tumor grade, tumor size, estrogen and progesterone receptors, and nodal stage. Logistic regression analysis showed that among these variables, all of which were univariately related to node metastasis, only tumor size and EMA were independent nodal stage predictors. A combined analysis of these two factors revealed that the statistical probability of a tumor metastasizing to four or more nodes increased in each tumor size group from 0.9% to 12% for pT1, from 2% to 29% for pT2 and from 10% to 63% for pT3, depending on the EMA staining. The tumors showing a lineal pattern were the least metastasizing, while the EMA-negative tumors were the most. After recognizing these relationships between EMA staining patterns and other well-known differentiation markers and the lymph node metastatic capacity of carcinomas, and considering the results obtained by others on survival, one might conclude that EMA is both a differentiation marker and a histological prognostic factor.

The importance of MUC1 cellular localization in patients with breast carcinoma: an immunohistologic study of 71 patients and review of the literature

BACKGROUND

The MUC1 mucin is present on the apical surface of normal secretory epithelia. In breast carcinoma, MUC1 expression is variable in amount and cellular localization, the significance of which is controversial. The authors undertook a detailed analysis of staining pattern combined with a comprehensive literature review to better understand the role of MUC1 in breast carcinoma.

METHODS

Seventy-one patients with breast carcinoma were examined for MUC1, beta-catenin, and E-cadherin staining patterns. These data were compared with data from 25 articles from the literature examining the expression of MUC1 in breast carcinoma.

RESULTS

All invasive carcinomas showed some MUC1 staining. In invasive ductal carcinomas, MUC1 was detected in the apical membrane (15%), cytoplasm (93%), or circumferential membrane (13%), with 81% of tumors showing a mixture of patterns. Tumors with low overall MUC1 expression (< or = 50% positive tumor cells) had a higher nuclear grade than tumors with high overall MUC1 expression (> 50%; P = 0.01). Tumors with high and low cytoplasmic expression had no difference in nuclear grade (P > 0.3). Circumferential membrane staining was correlated with positive lymph node status (P = 0.011).

CONCLUSIONS

In the literature, similar findings prevailed in which overall MUC1 expression was increased in lower grade (10 of 14 studies), estrogen receptor positive (8 of 13 studies) tumors and was associated with a better prognosis (8 of 13 studies). High cytoplasmic staining was associated with a worse prognosis, an association that was not explained by differences in histologic grade. Thus, the presence of MUC1 in the majority of tumor cells is associated with better differentiated tumors and with an improved prognosis. However, aberrantly localized MUC1 in the tumor cell cytoplasm or nonapical membrane is associated with a worse prognosis.

Binding evaluation of Isoform 1 from Cratylia mollis lectin to human mammary tissues

The phenomenon of altered carbohydrates in transformed cell surfaces has been studied through histochemical techniques using lectins. Specific binding patterns to normal and transformed mammary tissues were evaluated by Isoform 1 from Cratylia mollis lectin (Cra Iso 1). Protocols using a direct method, incubation of Cra Iso I conjugated to peroxidase (Cra Iso 1-Per) with mammary tissues, followed by diaminobenzidine and hydrogen peroxidase interaction, were performed. Neoplastic tissues, marked by Cra Iso 1, showed a higher intensity of staining than normal ones, in comparison with Canavalia ensiformis lectin, Concanavalin A (Con A), conjugated to peroxidase (Con A-Per). The assay with Cra Iso 1 also indicated a possible utilization of this lectin to characterize normal and transformed mammary cells.

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

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

Use of lectins as diagnostic and therapeutic tools for cancer

Within the past few years, lectins have become a well-established means for understanding varied aspects of cancer and metastasis. Evidence is now emerging that lectins are dynamic contributors to tumor cell recognition (surface markers), cell adhesion and localization, signal transduction across membranes, mitogenic stimulation, augmentation of host immune defense, cytotoxicity, and apoptosis. To advance understanding of these lectin-dependent processes, attempts are being made to discover new lectins that have one or more of these functions and to develop lectin- (or glycoconjugate-) based tools that could be used to home in on tumor cells. This review will summarize current research on the lectins and recent advances in the development of lectin-based diagnostic and therapeutic tools for cancer. Additionally, the future potential of lectin-based diagnosis and therapy is discussed.

Prognostic value of a breast cancer-associated glycoprotein detected by monoclonal antibody LU-BCRU-G7

The immunohistochemical reactivity of a second generation murine monoclonal antibody (LU-BCRU-G7), raised against a novel fucosylated glycoprotein of M(r) 2300,000, has shown a significant association with prognosis of early stage carcinomas. Staining was observed in 72% of the 190 breast carcinomas tested. No relationship with steroid receptor status, stage or node status was found. An association with grade was observed (chi 2 7.83, 2 degrees of freedom, P = 0.02) only when the negative cut-off level was raised from < 10% cells staining to < 25%. Antibody reactivity was always cytoplasmic. Immunoblotting shows the antibody is reactive with a component of M(r) 230,000 not detected by HMFG 2. A significant association was found between lack of reactivity and improved disease-free interval (0.005 > P > 0.001) and survival (0.02 > P > 0.01). Subdivision of cases on the basis of node status showed that staining could refine survival data. A decreased reactivity of LU-BCRU-G7 was observed after pretreatment with beta-galactosidase but not a sialidase or beta-N-acetylhexosaminodase indicating that non-reducing terminal galactose residues in beta 1-3 or beta 1-4 linkages may be involved in the antibody binding site. This approach has identified a useful and novel prognostic marker in early stage human breast carcinoma.

Expression of MUC2 epithelial mucin in breast carcinoma

AIMS

To examine the expression of the MUC2 epithelial mucin in breast carcinoma; to relate this to patient survival.

METHODS

Sections from 210 breast carcinomas were stained with the anti-MUC2 core protein monoclonal antibody, 4F1, using an immunoperoxidase technique. The proportion of tumour cells positively stained and the localisation and intensity of any staining were recorded. Expression of MUC2 was compared with histological type and grade, tumour size, presence of nodal metastases, presence of oestrogen receptors, and menopausal status. The prognostic value of MUC2 expression was examined using Kaplan-Meier survival analysis.

RESULTS

MUC2 mucin was detected in 19% of cases of invasive carcinoma, in 11% of cases of carcinoma in situ, where present, but very rarely in adjacent normal breast epithelium. Presence of MUC2 was significantly associated with a shorter disease free interval (p < 0.05), although the observed difference in duration of overall survival was not significant.

CONCLUSIONS

The MUC2 detected in breast carcinoma may be underglycosylated or staining may represent detection of the protein core before the completion of glycosylation. The virtual absence of 4F1 reactivity in normal breast epithelium suggests that, unlike the MUC1 mucin, the MUC2 mucin is not highly expressed by these cells. The mechanism by which expression of MUC2 affects the biology of breast tumours is unclear, although expression may be a reflection of general derepression of genes during tumour progression.