Increased Number of Accessible Sugar Epitopes Defined with Monoclonal Antibody AM-3 on Colonie Mucins Is Associated with Malignant Transformation of Colonie Mucosa1
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چکیده
Monoclonal antibody AM-3 detects a mucin sugar epitope (AM-3 epitope) the expression of which increases in the course of human colon carcinogenesis parallel to the gradual morphological alterations (so called adenoma-carcinoma sequence). In the present report the AM-3-positive mucin has been purified from human normal and carcinomatous colonie tissue. About 300-fold enrichment of the epitope per protein from both sources was achieved after ultracentrifugation, gel filtration on Sepharose CL-6B and isopyknic gradient centrifugaron. Slot-blot and enzymelinked immunosorbent assays of the purified preparation indicated not only different amounts of the mucins but also a consistent qualitative difference between the molecules from both sources. The qualitative difference could be obliterated by a partial removal of the AM-3 epitope from the tumor-derived mucin with neuraminidase. The visualization of the molecules by rotary shadowing indicated that the mucins from both sources have similar length distribution, 80% of the molecules being 100-600 nm long. The reaction with AM-3 antibody followed by rotary shadowing showed that in the purified preparations more than 95% of the tumor-derived molecules and 74% of the normal colon tissue-derived molecules carried the epitope. The tumor-derived mucins bound, on the average, 34 ±15 (SD) antibodies/1000 nm of the protein core while the mucin from normal colon tissue carried 12 ±11 antibodies/1000 nm of the protein core. These data indicate that the increased expression of AM-3 epitopes during malignant transformation of the human colon is due to accumulation of AM-3-positive mucin as well as a higher number of accessible AM-3 epitopes on this mucin.
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Sialyl Lewis" Antigen as Defined by Monoclonal Antibody AM-3 Is a Marker of Dysplasia in the Colonie Adenoma-Carcinoma Sequence
Monoclonal antibody AM-3 (MAb AM-3) raised against a sialomucin from human colorectal carcinoma has previously been shown to define a carbohydrate epitope, which is detectable by immunocytochemistry on all investigated colonie carcinomas and is expressed in correlation with the grade of dysplasia in colonie adenomas (Hanski et al., J. Clin. Pathol., 43:379-385, 1990). Epitope analyses in solid-...
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Monoclonal antibody AM-3 detects a mucin sugar epitope (AM-3 epitope) the expression of which increases in the course of human colon carcinogenesis parallel to the gradual morphological alterations (so called adenoma-carcinoma sequence). In the present report the AM-3-positive mucin has been purified from human normal and carcinomatous colonic tissue. About 300-fold enrichment of the epitope pe...
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