LOCALIZATION OF TUMOR-ASSOCIATED GLYCOPROTEIN DF3 IN NORMAL, INFLAMMATORY, AND NEOPLASTIC LESIONS OF THE COLON

Background. The expression of DF3 was assessed by a monoclonal antibod y in normal, inflammatory, and neoplastic conditions in the large bowe l. Methods. Using immunohistochemistry, expression was examined in for malin-fixed paraffin-embedded biopsy and resection samples of 19 norma l colonic mucosal specimens, 49 inflammatory lesions, 34 adenomas, and 38 primary colonic adenocarcinomas. In addition, Western blots of nor mal colonic mucosa and adenocarcinoma were examined. Results. DF3 expr ession was detected in 84% of the adenocarcinomas with coarse membrane staining, intense positivity of luminal secretions, and focal cytopla smic and intracytoplasmic vacuole staining. Nine of 32 areas of transi tional mucosa revealed reactivity along apical membranes in crypt cell s. Five adenomas containing carcinoma revealed DF3 positivity in the m alignant areas Only, whereas the remaining 29 were negative. Staining was membrane, luminal, and intracytoplasmic. Two examples of active ul cerative colitis revealed focal reactivity along the apical membrane o f crypt cells. No other areas of staining were noted, including 12 cas es containing dysplasia. Four of 10 other inflammatory lesions also re vealed similar membrane reactivity in crypt cells. Normal colonic muco sa was nonreactive. Examples of normal colonic mucosa were negative fo r DF3 by Western blot analysis, whereas two carcinoma samples that rea cted immunohistochemically were positive. Conclusions. DF3 is not dete ctable in normal colonic tissues. It is expressed focally and predomin antly along the apical membrane of crypt cells in some inflammatory le sions and in the transitional mucosa of primary adenocarcinomas. Most adenocarcinomas of the colon and adenomas with foci of invasive carcin oma demonstrate reactivity in the cytoplasm and luminal secretions.