EXPRESSION OF P53 PROTEIN IN NORMAL, DYSPLASTIC, AND MALIGNANT GASTRIC-MUCOSA - AN IMMUNOHISTOCHEMICAL STUDY

Mutations in the p53 nuclear oncogene are the most frequent genetic ab normalities encountered in human malignancies. Using the polyclonal an tibody CM-1, we have examined the expression of the p53 oncoprotein im munohistochemically in archival material of normal, dysplastic, and ma lignant gastric mucosa. Abnormal expression of this protein was not ob served in biopsies of normal gastric tissue (n=30) but was detected in 22 of the 36 gastric cancers analysed (61 per cent). Nuclear staining was diffuse in 15 of the positive cancer cases, the remaining seven s howing a more varied heterogeneous staining pattern. Abnormal p53 prot ein was not detected in mild (n=14) or moderate (n=16) gastric dysplas ia but was present in 3 out of 15 severe dysplasia cases. The results suggest that expression of the p53 oncoprotein is a common finding in gastric cancer and occurs as a late event in the malignant transformat ion process.