A comparative study on expression of mucin related antigens in preneoplastic and neoplastic rat colorectal mucosa

A polyclonal antibody (PAb35) defined antigen (Ag) was characterized in association with two monoclonal antibody (MAbM1 and MAb660) defined mucin M1 and 660 Ags in colorectal mucosa during 20-methylcholanthrene-induced rat carcinogenesis in the same organ. Immunohistochemistry and ELISA revealed that these three antibodies were reactive with most of the colorectal carcinomas. MAbM1 and MAb660 were reactive with preneoplastic colorectal mucosa in rats with no detectable carcinoma, in contrast to non-reactivity with PAb35. PAb35 reacted with preneoplastic mucosa, present adjacent to the cancerous tissues only. Staining was mainly localized in the cytoplasm of cancer cells, goblet cells and luminal mucous deposits. In control rats, M1 and 660 Ags were present in gastric mucosa, but not in colorectum. PAb35 defined Ag was absent in gastrointestinal mucosa of controls. ELISA revealed 82% reduction in reactivity, when PAb35 was reacted with 2-mercaptoethanol (2ME) treated colorectal mucosal extracts. Ninety percent reduction was seen in the case of MAbM1. However, 50% reduction was demonstrated when MAb660 was reacted with 2ME treated extracts.