Immunological analysis of mucin molecules expressed by normal and malignant mammary epithelial cells

Gene-based vaccines and immunotherapeutics

DNA vaccines, comprised of plasmid DNA encoding proteins from pathogens, allergens, and tumors, are being evaluated as prophylactic vaccines and therapeutic treatments for infectious diseases, allergies, and cancer; plasmids encoding normal human proteins are likewise being tested as vaccines and treatments for autoimmune diseases. Examples of in vivo prophylaxis and immunotherapy, based on different types of immune responses (humoral and cellular), in a variety of disease models and under evaluation in early phase human clinical trials are presented. Viral vectors continue to show better levels of expression than those achieved by DNA plasmid vectors. We have focused our clinical efforts, at this time, on the use of recombinant viral vectors for both vaccine as well as cytokine gene transfer studies. We currently have four clinical programs in cancer immunotherapy. Two nonspecific immunotherapy programs are underway that apply adenoviral vectors for the transfer of cytokine genes into tumors in situ. An adenovirus-IFN gamma construct (TG1042) is currently being tested in phase II clinical trials in cutaneous lymphoma. A similar construct, adenovirus-IL2 (TG1024), also injected directly into solid tumors, is currently being tested in patients with solid tumors (about one-half of which are melanoma). Encouraging results are seen in both programs. Two cancer vaccine immunotherapy programs focus on two cancer-associated antigens: human papilloma virus E6 and E7 proteins and the epithelial cancer-associated antigen MUC1. Both are encoded by a highly attenuated vaccinia virus vector [modified vaccinia Ankara (MVA)] and both are coexpressed with IL-2. Encouraging results seen in both of these programs are described.

Tissue and serum MUC1 mucin detection in breast cancer patients

Tumor MUC1 expression as well as levels of MUC1, MUC1 circulating immune complexes (MUC1-CIC) and free antibodies against MUC1 (IgG and IgM-MUC1) were evaluated in 70 breast cancer patients with different stages of disease. Controls included: 135 serum samples from healthy women, normal mammary tissue samples (n = 7) and benign breast disease specimens (n = 6). In all assays, pre- and post-vaccination serum samples from breast cancer patients belonging to a vaccination protocol developed at the Memorial Sloan Kettering Cancer Center (New York, USA) were included as controls. Serum MUC1 was measured through Cancer Associated Serum Antigen test and CA15-3 test. Employing ELISA, MUC1-CIC-IgG/M were measured with either C595 or SM3 monoclonal antibodies (MAb) as catchers and also free antibodies against MUC1 (IgG and IgM) using 100mer peptide as catcher. Employing multivariate statistical analysis, results were correlated with age, tumor type, stage of disease and grade of differentiation. By quantitative immunohistochemistry using three anti-MUC1 core protein MAbs (C595, HMFG2 and SM3), tumor MUC1 was detected in 60/70 (86%) breast cancer specimens which reacted with at least one of these MAbs. High MUCI serum levels were detected in 14/67 (21%); IgG and IgM anti-MUC1 antibodies were found elevated in 32 and 14%, respectively, while IgG-MUC1-CIC-measured with C595 in 42% and IgM-MUC1-CIC in 54%; finally, SM3 was positive in 43 and 18%, respectively. Results of these studies demonstrate that in a group of breast cancer patients, MUC1 was detected both in tissue specimens as well as free in serum samples; furthermore, MUC1 can also circulate complexed with IgG and IgM antibodies; thus an accurate measurement should include free and complexed forms. On the other hand, immunohistochemical studies on breast cancer tissues may contribute to reveal different MUC1 glycoforms.

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

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

Heregulin and retinoids synergistically induce branching morphogenesis of breast cancer cells cultivated in 3D collagen gels

C-erbB and retinoid receptor signaling control mammary epithelial cell proliferation, differentiation, and morphology. Here, we examined the morphogenetic activities of c-erbB specific ligands such as heregulin and of retinoids on non-malignant (primary, MTSV1-7) and malignant (T47D, SKBR-3) human mammary epithelial cells (HMEC) cultivated in 3D collagen type I gels. These cells are positive for both c-erbB and retinoid receptors. Non-malignant primary HMEC spontaneously formed branched structures in collagen, whereas SV40 large T antigen-immortalized non-tumorigenic MTSV1-7 spontaneously formed balls and required heregulin or retinoid X receptor alpha-selective retinoid Ro 25-7386 for branching, which was further stimulated by combination of both types of agents. In malignant cells, heregulin alone induced ball formation and cooperated either with Ro 25-7386 (T47D) or with retinoic acid receptor alpha-selective AM580 (SKBR-3) for branching morphogenesis, which was accompanied by changes in the subcellular distribution of alpha(2)beta(1)-integrin and E-cadherin, and by down-regulation of c-erbB-2, -3, or -4. Heregulin and/or retinoids correspondingly increased the integrin-dependent adhesion of malignant cells to type I collagen. Our data demonstrate cooperative signaling of c-erbB and retinoid receptor pathways at the levels of morphogenesis and immunophenotypic differentiation.

MUC1 mucin and carbohydrate associated antigens as tumor markers in head and neck squamous cell carcinoma

An immunological analysis to study MUC1 mucin core protein and carbohydrate associated antigens as tissue tumor markers in head and neck carcinoma was performed. Twenty nine patients with the following tumor localizations were included: tongue (n=10), larynx (n=8), oral cavity (n=4), maxillary sinus (n=3), tonsillar ring (n=3) and pharynx (n=1); seven samples of epithelium obtained from normal organs at the same localizations were studied as controls. Immunohistochemical analysis was performed following standard procedures and reaction was graded according to staining intensity and distribution. From each tissue section, membrane, cytoplasmic and nuclear moieties were obtained by differential centrifugation with subsequent fractionation by density gradient centrifugation (6M guanidium chloride-CsCl); subcellular moieties and CsCl derived fractions were analyzed by immunoblotting. Monoclonal antibodies (MAbs) reacting with the core protein of MUCI (C595) and associated carbohydrate antigens were: Tn, 83D4 MAb; Lewis y antigen (Le y), C14 MAb; Lewis x antigen (Le x), KM380 MAb and sialyl Lewis x (sLe x), KM93 MAb. Statistical analysis was undertaken by Spearman rank correlation. In tumor samples, the immunohistochemical identification of MUCl core protein and associated antigens was extended; differences were found in the pattern and intensity of expression; results were corroborated by immunoblotting although in a few samples there was not coincidence between both methods. Localization, tumor mass or node involvement did not show significant differences for any of the antigens studied.

CONCLUSIONS

1) head and neck carcinoma expressed MUCI and associated carbohydrate antigens in high levels; 2) no relationship between antigenic expression and tumor status was found.

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.

The value of the human milk fat globule membrane antigen HMFG2 in epithelial ovarian cancer monitoring: comparison with CA125

We assayed serum HMFG2 in serial samples from 215 primary epithelial ovarian cancer patients using an 'in-house' single determinant ELISA, 45% of patients with stage I, 54% with stage II, 61% with stage III and 75% with stage IV disease had elevated serum HMFG2. Post-operative levels were significantly related with residual tumour volume (P < 0.005), and fell in the majority of responders, although the association with response to first-line chemotherapy was not significant. HMFG2 had a sensitivity of 50% specificity of 83%, accuracy of 61%, PVP of 86% and PVN of 45% for disease at second-look laparotomy. Serial levels gave a lead time to clinical relapse in 47% of patients who responded to therapy, including one patient with negative CA125 levels. HMFG, paralleled CA125 in many respects, although it was elevated in fewer patients. In a stepwise discriminant analysis, HMFG2 added to the discrimination of CA125 (r = 0.183, P < 0.005), although additional accurate information was only given in patients with advanced poorly differentiated serous cystadenocarcinoma. Given that HMFG2 is expressed in few patients who are CA125 negative it is unlikely that it will have a significant clinical impact upon patient management.

Immunohistochemical analysis of the distribution of a breast tumor associated antigen recognized by a monoclonal antibody

A new monoclonal antibody (MoAb), MM 1-80, recognizing a tumor associated epitope of a breast high molecular weight mucin molecule was tested, using the avidin biotin immunoperoxidase method on normal and pathological mammary tissues. The normal mammary ducts and lobules were negative. Fibroadenomas showed a strong intracytoplasmic staining. In apocrine metaplasia, adenosis, and papillomatosis, scattered cells showed intracytoplasmic, luminal border or secretion reactivity. In lobular and ductal hyperplasia the cells showed intracytoplasmic immunoreactivity which, however, became more intense and homogeneous in atypical lesions, i.e. lobular and ductal in-situ carcinomas. The infiltrating carcinomas of different histotype expressed positivity on 98% of the cases (113/115) and axillary metastatic lymph nodes were always positive (20/20). The MoAb was tested on 175 human neoplasias of different origin which were in the majority of the cases negative with the exception of adenocarcinomas of the lung, ovary and bladder. MM1-80 appears to react preferentially with mammary cells undergoing hyperplastic, metaplastic and neoplastic processes. The 1-80 epitope distribution is different in these lesions starting with a predominant luminal expression in benign lesions and becoming strong and cytoplasmic in the malignant breast cell.

Epithelial membrane antigen expression in breast fluids and 'witch's milk'

We have examined breast fluids from non-lactating women and male neonates for the expression of epithelial membrane antigen (EMA), also termed polymorphic epithelial mucin (PEM). All fluids exhibited significant amounts of EMA as demonstrated by immunoblot analyses and enzyme immunoassay. EMA was present in the breast fluids of both pre- and post-menopausal women, and these results suggest that nipple aspirates could provide an easily accessible source of antigen for assessing the value of EMA as a tumor marker both before and after various therapeutic modalities. The presence of EMA in the 'witch's milks' indicates that full maturation of the breast is not a prerequisite for antigen expression in breast tissue.

Antigenic modulation of metastatic breast and ovary carcinoma cells by intracavitary injection of IFN-alpha

Antigenic modulation of major histocompatibility and tumour associated antigens was observed in neoplastic cells obtained from patients with pleural and abdominal effusions of breast and ovary carcinomas following a single intracavitary dose of 18 x 10(6) U recombinant IFN-alpha. This regimen resulted in antigenic modulation in seven out of 11 tested cases, suggesting a potential, although limited, responsiveness of at least a fraction of breast and ovary carcinoma cells to in situ biomodification with IFN-alpha.

Mucin-type glycoproteins

Considerable advances have been made in recent years in our understanding of the biochemistry of mucin-type glycoproteins. This class of compounds is characterized mainly by a high level of O-linked oligosaccharides. Initially, the glycoproteins were solely known as the major constituents of mucus. Recent studies have shown that mucins from the gastrointestinal tract, lungs, salivary glands, sweat glands, breast, and tumor cells are structurally related to high-molecular-weight glycoproteins, which are produced by epithelial cells as membrane proteins. During mucin synthesis, an orchestrated sequence of events results in giant molecules of Mr 4 to 6 x 10(6), which are stored in mucous granules until secretion. Once secreted, mucin forms a barrier, not only to protect the delicate epithelial cells against the extracellular environment, but also to select substances for binding and uptake by these epithelia. This review is designed to critically examine relations between structure and function of the different compounds categorized as mucin glycoproteins.

Aberrant expression of intestinal mucin antigens associated with colorectal carcinoma defined by a panel of monoclonal antibodies

Small intestine mucin antigen (SIMA) is an oncofoetal antigen for the colon and is distinct from the normal large intestinal mucin antigen (LIMA). In the present study, a panel of anti-SIMA and anti-LIMA monoclonal antibodies (MAb) was used to charaterise altered mucin expression in colorectal adenocarcinomas, by immunohistochemistry and quantitative immunoassays of tissue extracts. These results are compared with CEA expression and correlated with various clinicopathological indices. All mucin MAb reacted with a high proportion of the 100 colon cancers of every stage, histological type (including non-mucinous cancers), differentiation, site, or size. Inappropriate SIMA production was detected by either anti-SIMA MAb 4D3 or 4A1, even in 85% of early stage cancers. MAb 4D3 reacted with a higher proportion of cancers of smaller size and better differentiation. At the subcellular level, both anti-SIMA MAb showed reactivity typical of normal mucin, i.e., goblet cell and extracellular mucin. The normal colonic antigen, LIMA, was also detectable in the majority of cases, but quantitatively overproduced in some cases and reduced in others. However, in contrast to SIMA, LIMA was detected in predominantly undifferentiated cancer cells but not in goblet cells. Heterogeneity of MAb reactivity between cases and complementarity within each cancer was frequently observed. Mucin reactive with at least one of the MAb was detected in all of the CEA-negative cancers. A high rate of inappropriate SIMA expression was also detected in the perineoplastic transitional mucosa (88%, c.f. CEA, 35%) and adjacent, morphologically normal mucosa (80% c.f. CEA, 24%), indicating biochemical changes similar to the cancer. This panel of anti-mucin MAb demonstrated altered mucin glycoprotein metabolism associated with the development and progression of most colorectal cancers, which emphasises their utility as indicators of neoplastic change in the colon, and their superiority to CEA.

Oncofetal expression of the human intestinal mucin glycoprotein antigens in gastrointestinal epithelium defined by monoclonal antibodies

A mucin preparation from a colonic adenocarcinoma was used to prepare monoclonal antibodies (MAbs) that reacted specifically either with normal adult small-intestine mucin antigen(s) (SIMA), or normal adult large-intestine mucin antigen(s) (LIMA). Both SIMA and LIMA show a unique oncofetal pattern of expression. Thus SIMA was expressed in early fetal stomach, large and small intestines but thereafter only in the normal small intestine. SIMA expression was detected immunohistochemically in cancers of the colorectum (82/112) and stomach (48/86). LIMA was detected in the stomach of the early fetus but thereafter only in the normal large intestine. LIMA expression was detected in 61/86 cancers of the stomach. Moreover, both SIMA and LIMA were expressed inappropriately in mucosa adjacent to tumors, indicative of the detection of possible pre-malignant epithelium. We used a sandwich ELISA and biochemical procedures to show that the SIMA and LIMA molecules were large extensively glycosylated multi-unit mucin glycoproteins that differed markedly from each other. SIMA, whether extracted from normal small-intestine or colonic cancers, had a molecular weight above 1.000 kDa, a mean buoyant density 1.33 g/ml and s value of 4.8. LIMA had a molecular weight above 10.000 kDa, a mean buoyant density 1.45 g/ml and an s value 9.5. The SIMA and LIMA epitopes were judged to be carbohydrate in nature by reason of their resistance to harsh physical chemical treatments or protease digestion, and sensitivity to periodate oxidation, neuraminidase or beta elimination. Only the SIMA epitope was sensitive to neuraminidase. In conclusion, MAbs to carbohydrate-dependent epitopes on SIMA and LIMA identify the oncofetal pattern of expression of these distinct intestinal mucin glycoproteins in colonic and gastric carcinoma. These MAbs will be useful in further studies of the significance of oncofetal mucin expression during carcinogenesis.

Characterization, isolation and amino terminal sequencing of a rat colon carcinoma-associated antigen

Monoclonal antibodies have been raised against a cell line derived from a dimethylhydrazine-induced rat colon carcinoma. One of these antibodies (MAb E4) has previously been shown to react slightly with normal small intestine and colon, and not with other normal tissues as determined by immunohistochemistry. Using Western immunoblotting we confirmed this tumor specificity. Therefore, the Mr of approx. 66,000 glycosylated antigen (pE4) recognized by MAb E4 appeared to be a potential marker of colon carcinoma. Fifteen human tumor cell lines were tested by flow cytometry for the expression of pE4. This antigen was not detected on these cells. In the rat colon carcinoma cell, pE4 was exclusively found on the cell membrane. pE4 was purified to near homogeneity by immunoaffinity chromatography. The first 20 N-terminal amino acids were identified. Comparison with the NBRF data bank did not reveal a complete homology with known sequenced proteins but similarities were found with the mouse L3T4 precursor, the env polyprotein of human immunodeficiency virus type I, flagellin from Halobacterium halobium and the gp30 from hepatitis B surface antigen. Homology was always found in transmembranous or hydrophobic domains of these proteins. By indirect immunofluorescence analysis of adherent cells and size exclusion chromatography under native conditions, pE4 was found to interact with other molecules and perhaps to be involved in intercellular contact.

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

The milk fat globule membrane antibodies HMFG1, HMFG2, NCRC 11 and four of the Mam 6 series, and the lectins peanut agglutinin, wheat germ agglutinin, Concanavalin A, Lotus tetragonolobus and Ulex europaeus I have been applied to 115 stage I and II breast carcinomas (median follow up = 36 months) to assess their value as prognostic markers. Of the milk fat globule membrane antibodies only NCRC 11 staining showed a relationship to development of recurrent disease and overall survival, but this did not act as an independent indicator over and above that provided by histological grade. None of the lectins gave prognostic information, including those whose binding related to node status or grade. It is concluded that for short-term prognosis none of the markers can given independent prognostic information over and above that provided by histological evaluation.

Analysis of the tumour-associated antigen TAG-12 by monoclonal antibody 7A9 in normal, benign and malignant mammary tissues

A monoclonal antibody 7A9 was raised against the tumour-associated glycoprotein TAG-12 purified from T47-D breast carcinoma cells. In immunoblots from cytosol of T47-D cells and from sera of breast cancer patients, antibody 7A9 detects the high molecular weight mucin-like TAG-12 antigen. A series of paraffin sections of normal, benign and malignant mammary tissues have been studied with monoclonal antibody 7A9 and the immunoalkaline phosphatase method. In resting gland, proliferating gland and fibroadenoma ducts, reactivity of 7A9 was mainly restricted to luminal membranes of epithelial cells and secretions. 77/79 primary breast carcinomas including ductal, lobular and various other carcinoma types showed cytoplasmic and/or membrane-associated staining with 7A9 in most tumour cells. Metastases (31/31) from different sites were also positive. Strong immunoreactivity with single tumour cells was noted in cytological preparations from freshly resected breast cancer tissue. Thus, monoclonal antibody 7A9 seems to be very useful for the targeting of breast carcinoma cells.

Ultrastructural localization of milk fat globule membrane antigens in human breast carcinomas

The localization of milk fat globule membrane components has been assessed using post-fixation immunoelectron microscopy with three different antibodies for a group of breast carcinomas of different type and histological differentiation. For well differentiated carcinomas localization was in relation to the cell membrane, with polarization being evident in a proportion of cases. Moderately differentiated carcinomas showed a combined picture of cell membrane, vesicular, and intracytoplasmic luminal localization. The latter is a feature of infiltrating lobular carcinomas. Poorly differentiated carcinomas exhibited vesicular labelling throughout the cytoplasm, with no cell membrane localization. No labelling was seen over endoplasmic reticulum. It is proposed that carcinomas exhibit defects in intracellular transport of milk fat globule membrane components resulting in failure of expression at the cell surface and accumulation of vesicles within the cytoplasm, the extent of change relating to tumour differentiation.

Polymorphic epithelial mucin from the sera of advanced breast cancer patients--isolation and partial characterisation

The anti-breast carcinoma monoclonal antibody (MAb), NCRC-11 defines a polymorphic epithelial mucin (PEM) which is elevated in the circulation of advanced breast carcinoma patients. Here we describe the purification and partial characterisation of this component from patients' sera and its use in the production of a second generation MAb, C568 (IgM). Pooled sera was fractionated by immunoaffinity and size-exclusion chromatography and the purity of preparations assessed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Serum-derived PEM shows a similar pattern of electrophoretic mobility to PEM isolated from primary breast tumour tissue and migrates as several bands in 4% SDS polyacrylamide gels (Mr greater than 400,000). The epitope expression of PEMs isolated from either source is also similar, with both bearing topographically distinct determinants for several anti-mucin MAbs. The immunoreactivities of antibodies C568 and NCRC-11 were unaffected by boiling, reduction and alkylation, or by enzyme desialylation of PEM. Periodate oxidation and proteolytic digestion have suggested that the antigenic determinant for C568 is carbohydrate in nature whilst that of NCRC-11 is peptidic. In accord with the mucinous nature of the molecule, serum-derived PEM is susceptible to reductive beta-elimination, elutes in the void volume of a Sepharose CL-4B column and has a buoyant density of 1.45 g ml-1.

Isolation and characterization of 5T4, a tumour-associated antigen

The monoclonal antibody (MAb) 5T4 defines a human trophoblast antigen marker with a restricted pattern of expression in normal adult tissues but this antigen is expressed on a variety of carcinomas. The purification of 5T4 antigenic molecules is described from term syncytiotrophoblast by a combination of lectin- and immunoaffinity chromatography and gel filtration giving up to 10,000-fold purification with 70% yield. The antigen is carried by non-associated glycoprotein molecules with an apparent molecular weight of 72 kDa on SDS-PAGE and a neutral pI. Removal of N-linked sugars by N-glycanase reveals a core protein of 42 kDa. Treatment with enzymes that cleave O-linked sugars does not substantially alter the molecular size. The native 5T4 molecules are very resistant to proteolysis until the N-linked sugars are removed or the glycoprotein is denatured and reduced. Glycopeptides generated by these approaches will be suitable for amino acid sequencing.

Evidence of mucin M1 antigens in seminal plasma and normal cells of human prostatic urethra in relation to embryonic development and tumors

By employing immunoperoxidase methodology, using monoclonal antibodies against the peptide core of gastric mucins (M1 antigens), we demonstrate the presence of M1 mucin-producing cells that are associated with the prostatic urethral epithelium and located mainly in the veru montanum area near the prostatic ductal and utriculus junctions. The significance of these M1 cells is not yet clear. Using an immunoradiometric assay, these M1 mucins were found predominantly in the prostatic fraction obtained from seminal plasma. By chromatography on Sepharose 6B and 2B and cesium chloride gradient centrifugation, we demonstrate that high-molecular-weight components (greater than 10(7) Da) show a density of 1.45 g/ml, similar to mucins, and are immunochemically related to peptidic gastric M1 mucins. The particular location of these M1 antigens in prostatic adult urethra and their fetal expression in cloacal structures suggest that, in males, the prostatic urethral epithelium includes some remnant cells from the enteric cloaca. Finally, the presence of mucin-containing cells in the prostatic urethra could possibly explain the histogenesis of the rare benign villous tumors and primary mucinous adenocarcinomas arising from the prostatic urethral epithelium.

Monoclonal antibodies reactive with mucin expressed in breast cancer

Three murine monoclonal antibodies (BC1, BC2 and BC3) were developed against human milk fat globule membrane (HMFGM). By immunoperoxidase staining, it was found that the antigenic determinants had a predominant distribution in breast cancer tissue. In addition, the antibodies reacted preferentially with mucin derived from human milk rather than that derived from the breast cancer cell line ZR75; they also recognized polymorphic high molecular weight components (MW greater than or equal to 230,000) in serum and in human milk fat globule membrane. Thus the antibodies appear to react with a component of the family of mucins found in breast cancer and human milk and it appears likely that at least part of each epitope is protein in nature. Antibodies BC1, BC2 and BC3 recognized related but not identical epitopes, and they appear to be co-expressed on the same molecules as 3E1.2-defined antigen (mammary serum antigen, MSA) which is also a member of the family of breast cancer-related mucin. However, the 3E1.2 epitope is distinct and non-cross-reactive with those described for BC1, BC2 and BC3. The BC2 and BC3 defined epitopes were examined for their value in serum assays. Immunoassay was developed with a combination of two antibodies, using antibody BC3 for antigen capture and antibody BC2 or 3E1.2 for antigen detection and gave reasonable sensitivity (approximately 85%) and specificity (approximately 95%) in such serum tests for breast cancer. In a limited study, these tests appeared to complement the MSA test in the detection of breast cancer.

Secretory component in differentiating normal epithelium, benign lesions and malignancy in the human breast as monitored by monoclonal antibodies

An immunohistochemical study of the expression of the secretory component (SC) in human mammary gland epithelium at various stages of differentiation, as well as in benign and malignant breast tumours, was undertaken using three mouse monoclonal antibodies. Antibody RICEO-SC-05 (SC-05), raised against a partially purified preparation of human SC, and reacting with a reduction-resistant epitope present in both free and polymeric immunoglobulin-bound SC, was compared in immunoperoxidase and immunofluorescence studies on a diverse range of normal tissues, to 2 reference anti-SC antibodies (LICR-LONLC28 and RICEO-MFG-12). All three antibodies reacted with secretory epithelia only, consistent with known patterns of expression of SC in tissues, although there was an unexpected reaction by all anti-SC antibodies with some Hassal's corpuscles of the thymus. Staining patterns seen in the normal resting, pregnant, lactating and regressing (after weaning) breast provide evidence for differentiation-associated changes in the production of SC, and support the concept of terminal ductal lobular units (TDLUs) as functional compartments of the mammary gland. SC was detected in all but one benign breast lesion (n = 53) as compared to only 24% positive cases with heterogeneous expression of SC found among 176 primary and metastatic breast carcinomas examined. In a series of 40 primary breast carcinomas and their corresponding lymph node metastases, a good overall correlation was found between the expression of SC in the matched specimens; aside from 3 heterogeneously SC-positive carcinomas whose metastatic counterparts were SC-negative. Our results demonstrate a potential application for monoclonal antibodies to SC in the study of human mammary gland differentiation, but suggest that the value of an assay for SC in the diagnosis of breast carcinomas is questionable due to the generally low expression of SC by either primary or metastatic breast lesions.

Purification and biochemical characterisation of a novel breast carcinoma associated mucin-like glycoprotein defined by antibody 3E1.2

A member of the high molecular weight glycoproteins of human milk and breast cancer was isolated from the sera, ascites and breast carcinoma tissue of patients with breast cancer using monoclonal antibody 3E1.2. The 3E1.2 defined antigen, termed mammary serum antigen (MSA) was obtained by immunoaffinity chromatography and a solid phase immuno-precipitation technique (SPIT) from serum of patients with metastatic breast cancer. MSA was found to be a high molecular weight glycoprotein with a Mr greater than 300,000 by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and a native Mr approximately 1 x 10(6) by gel filtration chromatography; in accord with the published Mr of other high molecular weight glycoproteins obtained from human milk and breast cancer. A high degree of glycosylation of MSA molecule was shown by its poor staining with Coomassie blue but good staining in a PAS-silver stain. In addition, MSA contained N-acetyl neuraminic acid and N-acetyl glucosamine as indicated by its binding to wheat-germ agglutinin. The epitope defined by antibody 3E1.2 is sensitive to treatment by sodium periodate and neuraminidase, implying that both carbohydrate and sialic acid are required for binding of antibody 3E1.2. Sandwich immunoassays demonstrated that MSA+ molecules are likely to express repeated 3E1.2 defined epitopes. Furthermore, MSA was susceptible to degradation by pronase, subtilisin and proteinase K and gave a different peptide profile from that of the PAS-O glycoprotein of human milk. MSA+ molecules were found to carry epitopes for a number of other monoclonal antibodies which were reactive with the PAS-O glycoprotein. It is suggested that MSA has the same core protein as is recognised by antibody DF3 which has been used to clone the same cDNA as was cloned with antibodies HMFG-1, HMFG-2 and SM-3. However, the epitope detected by the 3E1.2 antibody is either absent or weakly expressed on human milk, human milk-fat globule membrane (HMFGM) or deglycosylated HMFGM--all of which react strongly with various anti-HMFG antibodies. The antibody 3E1.2 thus recognises a unique epitope of the high molecular weight glycoproteins of human milk and breast cancer, being found in cancer tissue, serum and ascitic fluid of patients with breast cancer but weakly expressed or absent in human milk.

Growth factor control of myoepithelial-cell differentiation in cultures of human mammary gland

The relationship between growth and cytodifferentiation was studied in cultured human mammary myoepithelial cells under serum-free culture conditions. Myoepithelial-cell differentiation was monitored by quantifying cells showing immunoreactivity to the muscle isoform of actin; to the membrane glycoprotein common acute lymphoblastic leukemia antigen (CALLA); and to type IV collagen. Growth was quantified either by measuring the actual increase in cell number, or in a more-sensitive assay using immunoreactivity to the cell-proliferation-associated nuclear antigen Ki-67 as a measurement of the number of cells leaving the G0-phase of the cell cycle. The results showed that: (a) Primary cultures of myoepithelial cells on DME-F12 supplemented with cholera toxin (CT) alone resulted in the formation of quiescent cell islets (in the G0-phase of the cell cycle) showing phenotypic traits preserved from the in vivo situation (actin- and CALLA-positive cells with little or no type-IV-collagen immunoreactivity). (b) After addition of epidermal growth factor (EGF), with an ED50 of 1-10 ng/ml, in the presence of CT, the cells entered the G1-phase of the cell cycle, without further increase in cell number. At the same ED50 of EGF, the frequency of CALLA-positive cells decreased, while the number of cells immunoreactive for type IV collagen increased with a maximal effect of EGF seen after 7-11 days. During the same period, the cells remained fully differentiated with respect to actin immunoreactivity. (c) Further addition of insulin (I) to the medium in the presence of EGF and CT resulted in the cells entering an exponential growth phase associated with simultaneous decrease in actin immunoreactivity with a maximal effect of I after 11 days of exposure. The dose-response curve to I was virtually identical for stimulating cell proliferation and for reducing the frequency of actin-immunoreactive cells (ED50 in the range of 30 ng/ml), suggesting that the two processes were controlled by the same initial I-receptor interaction. (d) Some reduction in the number of actin-positive cells was exerted by I-EGF-CT independently of the mitogenic response, but this reduction was further augmented if the cells were allowed to proliferate. (e) Time-course studies of quiescent (G0-phase) cells stimulated to exponential growth revealed that entrance of cells into the G1-phase of the cell cycle preceded the loss of muscle actin filaments. (f) Exponentially growing actin-negative epithelial cells did not resume a myoepithelial phenotype in density-arrested postconfluent cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium butyrate induces differentiation in breast cancer cell lines expressing the estrogen receptor

Addition of sodium butyrate (NaB) to 6 cultured human breast carcinoma cell lines results in a dose and time-dependent growth inhibition. Kinetic evidence, related to the growth of a minority cell population which decreases in size with time of exposure, is presented to indicate that the NaB effect is reversible. In those cell lines that express the estrogen receptor (ER), growth inhibition is accompanied by a more differentiated phenotype, which is characterized by increased accumulation of lipid and milk-fat globule membrane glycoproteins. The potential for differentiation is not blocked by tamoxifen, indicating that the relationship to ER expression is likely secondary to the association of ER expression with a particular stage of secretory cell differentiation that is susceptible to NaB induction. Of the 3 lines shown to respond in this way (MCF-7, ZR-75-1, and MDA-134), ZR-75-1 is an extreme example that may serve as a model for studies of gene expression during human mammary epithelial cell differentiation.

Monoclonal antibodies to epithelial sialomucins recognize epitopes at different cellular sites in adenolymphomas of the parotid gland

Fourteen monoclonal antibodies (MAbs) to epithelial sialomucins were studied for their immunohistochemical reactivity on serial sections of 14 formalin-fixed and paraffin-embedded adenolymphomas of the parotid gland. Two types of reactivity were observed, suggesting different cellular distribution of the corresponding epitopes. Most antibodies reacted with the luminal membrane of the columnar tumor cells (type-A reaction). The other reaction (type B) was observed with the membrane of basal epithelial cells. The antibodies could be ranked according to their tendency to show type-A and/or type-B reactions. MAb Cal was the only one with a pure type-A reaction. A strong tendency to type-A reactivity (with traces of type-B reactions) was observed for the antibodies HMFG-2, M8, E29 and NCRC-II. Several antibodies gave good type-B reactions in addition to strong type-A reactivity (MAbs 126E7, 115G2, 115D8, 140C1, F36/22, 139H2). MAb DF3 showed equally strong reactions with both cell types. A clear-cut preference of the reactions with basal cells was seen with the antibodies HMFG-1 and 115F5. This subclassification of the antibodies is in accordance with epitope mapping data, obtained by conventional blocking studies reported in the literature.