pE4 is a rat carcinoma-associated antigen identified by monoclonal antibody E4, which was raised against a rat colon carcinoma cell line. This glycoprotein is expressed at the surface of all the rat colon carcinoma cell lines tested, as determined by immunofluorescence analysis. In contrast, a barely detectable level was found on normal adult rat colon and lung and no expression could be detected on the other normal rat tissues tested. The corresponding Tage4 gene (tumor-associated glycoprotein E4) is also expressed in rat colon tumors induced by 1,2-dimethylhydrazine and in Min mouse intestinal adenomas. The Tage4 gene product is closely related to the hepatocellular carcinoma antigen TuAg.1. The Tage4 cDNA has been isolated and sequenced. Analysis of the deduced aminoacid sequence indicated that Tage4 is a member of the immunoglobulin supergene family. This family contains cell adhesion molecules which have wide-ranging functions and mediate a variety of homotypic and heterotypic cellular interactions playing a general role in cell surface recognition. The Tage4 gene has been mapped to rat chromosome 1q22 and mouse 7A2-B1, regions that are homologous to the long arm of human chromosome 19. Summary review of our work is presented.

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