Increased Number of Accessible Sugar Epitopes Defined with Monoclonal Antibody AM-3 on Colonie Mucins Is Associated with Malignant Transformation of Colonie Mucosa1

نویسندگان

  • Christoph Hanski
  • John Sheehan
  • Michael Kiehntopf
  • Birgit Stolze
  • Harald Stein
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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تاریخ انتشار 2006