Antibody MBr1 Research Articles

Expression profile of saccharide epitope CaMBr1 in normal and neoplastic tissue from dogs, cats, and rats: implication for the development of human-derived cancer vaccines.

CaMBr1 is a blood group-related tumour-associated antigen, whose pattern of expression provides a therapeutic window for passive or active immunotherapy and points to the promise of a vaccine against carcinomas overexpressing this antigen. In this context, an animal model that closely mimics the human situation would be extremely useful. We, therefore, utilised the murine monoclonal antibody MBr1, which defines CaMBr1, as a useful probe to detect the molecule targeted for vaccine development on canine and feline spontaneous breast and uterus tumours and on their normal counterparts, and on rat normal tissues and carcinoma cell lines. Immunoperoxidase staining of cryostat sections revealed homogeneous CaMBr1 expression only in normal feline uterus and a uterus papilloma, whereas MBr1 reactivity was very weak and heterogeneous in normal (1/3 and 1/3) and tumour (1/10 and 1/6) breast tissues from dogs and cats, respectively. In contrast, the data obtained in rat tissues were reproducible in the strains tested and showed that CaMBr1 was expressed in all epithelial tissues of the digestive tract, although with variable intensities. Monoclonal antibody staining appeared to correspond to membrane-bound structures as well as mucinous secretions. Similarly, secretion products of lactating mammary glands expressed CaMBr1. The spectrum of expression on rat digestive tract was broader than that in humans but the specificity of MBr1 reactivity was confirmed by competition assay with a synthetic tetrasaccharide that mimics the CaMBr1 antigen. On FACS analysis, only one of two clonal derivatives of the rat breast carcinoma line RAMA 25 expressed CaMBr1, and a negative cell subset was evident in repeated experiments. By contrast, both colon carcinoma lines, DHD/K12 and CC531, showed staining with MBr1, albeit at different levels of intensity, and no evidence of a negative subset. The cell line CC531 maintained or even increased CaMBr1 expression levels following transplantation in syngeneic immunocompetent animals. Our data suggest the usefulness of the rat as a test model for vaccines against human cancers overexpressing the CaMBr1 antigen.

Oligosaccharides related to tumor‐associate antigens. Part 3. Synthesis of the propyl glycosides of the trisaccharide β‐D‐Galp‐(1→3)‐β‐D‐GalpNAc‐(1→3)‐α‐D‐Galp and of the Tetrasaccharide α‐L‐Fucp‐(1→2)‐β‐D‐Galp‐(1→3)‐β‐D‐GalpNAc‐(1→3)‐α‐D‐Galp, components of a tumor antigen recognized by the antibody MBr1

AbstractThe synthesis of the trisaccharide β‐D‐Galp‐(1→3)‐β‐D‐GalpNAc‐(1→3)‐α‐D‐Galp‐1‐OPr (2) and of the tetrasaccharide α‐L‐Fucp‐(1→2)‐β‐D‐GalpNAc‐(1→3)‐β‐D‐Galp‐1‐OPr (3), starting from the disaccharidic dihydrooxazole donor 5, is described. Glycosylation of 5 with 6 in the presence of Me3SiOTf gave the trisaccharide 7 which was deprotected with standard methods to give, via 8, compound 2 (Scheme 1). Alternatively, protection of 8 as the 4′,6′‐O‐benzylidene derivative 9 followed by glycosylation with 10 and by standard deprotection afforded the tetrasaccharide 3 (Scheme 2). Biological testing showed that trisaccharide 2 is unable to inhibit the binding of the monoclonal antibody MBr1 to the target tumor cells MCF7, while tetrasaccharide 3 inhibits the binding in ca. 7‐fold extent with respect to the previously tested trisaccharide α‐L‐Fucp‐(1→2)‐β‐D‐Galp‐(1→3)‐β‐D‐GalpNAc‐1‐OPr. These results indicate that the galactose corresponding to the unit D of compound 1 plays an important role in defining the MBr1‐recognized epitope and confirm the essential role of fucose for MAb recognition.

ChemInform Abstract: Oligosaccharides Related to Tumor‐Associated Antigens. Part 1. Synthesis of the Propyl Glycoside of the Trisaccharide α‐L‐Fucp‐( 1 → 2)‐β‐D‐Galp‐(1 → 3)‐β‐D‐GalpNAc, Component of a Tumor Antigen Recognized by the Antibody MBr1.

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Oligosaccharides Related to Tumor‐Associated Antigens. Part I. Synthesis of the propyl glycoside of the trisaccharide α‐L‐Fucp‐(1 → 2)‐β‐D‐Galp‐(1 → 3)‐β‐D‐GalpNAc, component of a tumor antigen recognized by the antibody MBr1

AbstractThe synthesis of the trisaccharide α‐L‐Fucp‐(1 → 2)‐β‐D‐Galp‐(1 → 3)‐β‐D‐GalpNAc‐1‐OPr (2) is described. The N‐acetylgalactosamine 6 was obtained from 4 by an intramolecular displacement of a (trifluoromethyl)sulfonyloxy by a pivaloyloxy group with its concomitant migration from position 3 to position 4 (Scheme 1). The galactosyl donor 9 was obtained from 7 via 8 by regioselective opening of the orthoester function with AcOH/pyridine followed by treatment with CCl3CN and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) (Scheme 2). Glycosylation of 6 with 9 in the presence of BF3 · OEt2 gave the disaccharide 10. Selective deprotection of 10 at OC(2′) followed by glycosylation with 12 and by standard deprotection afforded the title trisaccharide 2 (Scheme 3). Preliminary biological testing showed that 2 is able to inhibit the binding of the monoclonal antibody MBrl to the target tumor cells MCF7 in a dose‐dependent manner.

Use of monoclonal antibody MBr1 to detect micrometastases in bone marrow specimens of breast cancer patients

Bone marrow specimens obtained from 121 breast cancer patients immediately after surgery were examined by an immunofluorescence method with monoclonal antibody MBr1 to detect tumour cells undetectable by other diagnostic procedures. 80 women were node-negative and 41 node-positive. In no case could conventional histology demonstrate tumour cells, whereas MBr1 was positive in 20 (16.5%) of the 121 cases. No difference was observed in MBr1 positivity between node-negative and node-positive cases (17% vs. 15%). With regard to clinical outcome (median follow-up 48 months) 27 women relapsed, including 6 to 20 MBr1-positive and 24 of 101 MBr1-negative patients. First distant metastases or death from progression of disease were taken as end-points. Multivariate analysis showed that the additional contribution of MBr1 positivity, after making allowance for other prognostic factors, was negligible.

Characterisation of the mouse/human chimaeric antibody MBr1 : R. Orlandi, M. Figini, A. Tomassetti, S. Canevari, G. Winter and M.I. Colnaghi Istituto Nazionale Tumori, Milano, Italy; and Medical Research Council, Cambridge, UK

Characterisation of the mouse/human chimaeric antibody MBr1 : R. Orlandi, M. Figini, A. Tomassetti, S. Canevari, G. Winter and M.I. Colnaghi Istituto Nazionale Tumori, Milano, Italy; and Medical Research Council, Cambridge, UK

Type 4 chain H expression by bile ductules and hepatocytes in cirrhosis

The monoclonal antibody MBr1 defines the blood group H determinant with beta 1----3N-acetylgalactosamine linkage (Fuc alpha 1----2Gal beta 1----3GalNAc----R) carried by type 3 or 4 backbone. The distribution of the antigen detected by this antibody was studied immunohistochemically in liver tissues. Although bile ducts with a diameter of more than about 100 microns normally expressed the MBr1-reactive antigen supranuclearly, smaller bile ducts and bile ductules did not express the antigen. In cirrhotic liver, proliferated bile ductules extensively expressed the MBr1-reactive antigen. In spite of the absence in normal liver cells, the antigen was expressed membranously in some cirrhotic liver cells. Under subcellular fractionation, MBr1 reactivity was almost exclusively recovered in the microsomal fraction. By HPTLC immunostaining, the major MBr1-reactive antigen was shown to be carried by type 4 chain H glycolipid (globo-H, Fuc alpha 1----2Gal beta 1----3GalNAc beta 1----3Gal alpha 1----4Gal beta 1----4Glc beta 1----1Cer). MBr1 reactive glycoprotein was not found. In conclusion, although type 4 chain H glycolipid is not expressed by normal bile ductules and liver cells, it is actively synthesized and expressed by proliferated bile ductules and some of the liver cells in cirrhosis in the absence of any neoplastic change.

Internalization of a monoclonal antibody against human breast cancer by immunoelectron microscopy.

Using an avidin-gold conjugate, the binding and internalization of the biotinylated anti-breast cancer monoclonal antibody MBr1 in MCF-7 cells were examined. After labelling MCF-7 cells at 0 degrees C, MBr1 was found to specifically bind to the entire cell surface. MBr1 distribution was diffused in cells fixed before labelling, but appeared in patches of different sizes in cells immediately fixed after labelling. On warming prelabelled cells at 37 degrees C for 2 min, MBr1 was internalized through non-coated small invaginations and vesicles an also through smooth invaginations with coated regions at the bottom. After warming for 15 and 30 min to 37 degrees C, the MBr1 internalization sites were observed as large membrane invaginations, large vesicular structures and lysosomes. The early steps of MBr1 internalization which consists of non-coated micro-invaginations seem to be correlated to the glycolipidic nature of the MBr1 recognized molecule. The MBr1 ability to enter MCF-7 cells suggests that this anti-tumour monoclonal antibody may be used as a toxin ability to enter MCF-7 cells suggests that this anti-tumour monoclonal antibody may be used as a toxin carrier agent.

Evaluation of toxic effects following administration of monoclonal antibody MBr1 in patients with breast cancer.

Twelve patients with disseminated breast cancer were injected with monoclonal antibody MBr1 at the National Cancer Institute of Milan, Italy, from January 1983 to March 1985. The first seven patients had advanced disease and the remaining five operable breast cancer. In the first seven patients the initial dosage of MBr1 was 0.5 mg and was doubled in the next patient up to 16 mg. The last five women received 10 mg of MBr1. No general side effects such as bronchospasm, hypotension, immediate or delayed allergic reactions were observed. Four patients who were injected with 10 mg or more experienced fever, shudder and vague abdominal and articular pain. The following tests were monitored: R.B.C., W.B.C., percentage of lymphocytes, blood glucose, urea nitrogen and creatinine, serum levels of Na+, K+, Cl-, total proteins levels, albumins and globulins, bilirubin, GOT, GPT, alkaline phosphatase, LDH, amylase, gamma GT and CPK. No major modifications were observed: a limited increase of the transaminases, LDH and gamma GT was evident at the last check. An early temporary alteration of CPK was observed in the four patients who had symptoms. Serum levels of MBr1 are detectable immediately after injection starting from 4 mg, and all sera were negative 48 hours later. It is concluded that the scanty toxicity allows to continue clinical investigations to verify the linkage between MBr1 and Ca-MBr1 "in vivo" after a single injection of no more than 16 mg of the MoAb. The increase of this dosage as well as multiple injections do not seem safe at present.

Characterization of a glycosphingolipid antigen defined by the monoclonal antibody MBr1 expressed in normal and neoplastic epithelial cells of human mammary gland.

The antigen defined by a monoclonal antibody, MBr1, was found to be expressed in normal human mammary gland epithelia and human mammary carcinoma cells (Ménard, S., Tagliabue, E., Canevari, S., Fossati, G., and Colnaghi, M. I. (1983) Cancer Res. 43, 1295-1300). The antigen has been isolated from breast cancer cell line MCF-7, which was used as immunogen, and its structure was determined by methylation analysis, NMR spectroscopy, direct probe mass spectrometry, and enzymatic degradation as identified below. Fuc alpha 1----2Gal beta 1----3GalNAc beta 1----3Gal alpha 1----4Gal beta 1----4Glc beta 1----1Cer The antibody cross-reacted weakly with fucosylasialo-GM1 (IV2FucGg4), which shares the same terminal sequence, Fuc alpha 1----2Gal beta 1----3GalNAc, with this antigen. However, various other structures, including lacto-series H structure (Fuc alpha 1----2 Gal beta 1----4/or 3GlcNAc beta 1----3Gal), did not show any reactivity with this antibody. Therefore, this antigen represents a blood group H antigen with a globo-series structure which is abundant in human teratocarcinoma (Kannagi, R., Levery, S. B., Ishigami, F., Hakomori, S., Shevinsky, L. H., Knowles, B. B., and Solter, D. (1983) J. Biol. Chem. 258, 8934-8942), although its presence must be limited in normal adult human tissue.