Relationship between Ras Oncogene Expression and Clinical and Pathological Features of Colonic Carcinoma

Abstract

In order to investigate the value of ras oncogene expression as a prognostic indicator in colonic adenocarcinoma, we evaluated the level of ras gene protein product (p21) in the available material of 109 surgical specimens resected at our institution between 1978 and 1981. Pathology slides and archived paraffin blocks were retrieved for confirmation of the original diagnosis, determination of stage, and measurement of p21 content. P21 titers were obtained using the RAP-5 monoclonal antibody in a semiquantitative immunohistochemical assay. Titer was expressed as the highest dilution of antibody given definitive staining using the Avidin-Biotin peroxidase method. The analysis indicated that tumors with high ( > 1:40,000) p21 titer had a lower five-year survival rate than tumors with low ( < 1:40,000) titers (34.3% vs 60.8%, p < 0.02). When a logistic regression analysis was used with the dependent variable being five-year survival and the independent variables being age, sex, location of tumor, Dukes’ stage, mucin production, p21 titer, differentiation degree and tumor size, the statistically significant relationship of the level of ras gene protein product to long-term survival was negated by the concomitant knowledge of Dukes’ stage. On the other hand, when only the variables available in the preoperative period were entered in the multivariate analysis, p21 titers retained a significant relationship with long-term survival (p < 0.05). We conclude that ras oncogene determination in colonic carcinomas may have importance for the pre-operative identification of a group of colonic tumors with a more aggressive behavior and a poorer prognosis.