Enhanced Expression of e-1la-ras p21 in Human Stomach Adenocarcinomas Defined by Immunoassays Using Monoclonal Antibodies and in Situ Hybridization

Using c-Ha-, c-Ki-, and c-N-r<w-specific probes in a RNA-RNA hy bridization assay we found enhanced expression of c-Ha-nu protoonco gene in stomach adenocarcinomas relative to nonneoplastic epithelium, whereas little or no transcription of either c-Kior c-N-ros was detected. Enhanced levels of c-Ha-ros RNA expression were detected in all of the adenocarcinomas examined. Hybridization with c-Ha-ras was also de tected in nonneoplastic gastric epithelium adjacent to carcinoma, although the labeling was less intense than that of carcinoma cells. More extensive analysis of the c-Ha-ras p21 expression was then carried out in formalinfixed, paraffin-embedded tissue sections and extracts from surgically resected stomach tissues using monoclonal antibodies (M.Vhs) RAP-S and Y13-259. The data obtained from the immunohistochemical studies were consistent with the results of in situ hybridization assay. Adenocar cinomas were much more reactive with MAb RAP-5 than benign and normal tissues, and the majority of carcinomas demonstrated increased expression of c-IIa-rav p21. Quantitative liquid competition radioimmunoassays using MAb Y13-259 also demonstrated significantly higher levels of c-Ha-ros p21 in extracts from stomach adenocarcinomas than those from normal mucosae. No strict correlation was found between ras p21 expression and the degree of tumor differentiation or histolÃ3gica! type. Although advanced carcinomas generally demonstrated higher lev els of ras p21 than early carcinomas, no correlation among advanced carcinomas and ras p21 levels was observed in relation to depth of tumor invasion to the muscularis propria, subserosa, or serosa. Benign lesions, in comparison, were much less reactive with MAb RAP-5 than carcino mas. Among the benign lesions tested, dysplastic lesions were more reactive than nondysplastic lesions. Normal stomach mucosa was gener ally nonreactive with the exception of parietal cells. Our results indicate that transformation of the stomach mucosa from benign to malignant phenotype is associated with an increase in c-Ha-ros p21 expression.