P53 EXPRESSION IN PRECANCEROUS GASTRIC-LESIONS - AN IMMUNOHISTOCHEMICAL STUDY OF PAB 1801 MONOCLONAL-ANTIBODY ON ADENOMATOUS AND HYPERPLASTIC GASTRIC POLYPS

To determine the chronology of p53 mutation in the gastric carcinogeni c sequence, we studied p53 overexpression in premalignant lesions, inc luding 17 adenomatous polyps (10/17 surrounded by intestinal metaplasi a and 11/17 harboring foci of adenocarcinoma or severe dysplasia), and 18 hyperplastic polyps (4/18 with focal adenomatous changes). Immunoh istochemistry with PAb 1801 monoclonal antibody was performed on archi val material; p53 nuclear staining was seen in 10/17 adenomas, but was limited to the foci of adenocarcinoma in three cases. Five adenomas w ith foci of severe dysplasia or carcinoma were nonreactive. Intestinal metaplasia, normal gastric mucosa, and 14/18 hyperplastic polyps were nonreactive. p53 Reactivity observed in four hyperplastic polyps was limited to adenomatous foci. These results suggest that p53 overexpres sion occurs in dysplastic epithelium of precancerous gastric lesions. Its absence in chronic atrophic gastritis with intestinal metaplasia s uggests it is a relatively late event in the gastric carcinogenic sequ ence.