LACK OF CORRELATION BETWEEN CODON-12 K-RAS MUTATIONS AND MAJOR HISTOCOMPATIBILITY COMPLEX ANTIGENS IN BRONCHOGENIC CARCINOMAS

In experimental systems, an association between K-ras activity and exp ression of major histocompatibility complex (MHC) molecules has been r eported. In this study, 52 surgically resected bronchogenic carcinomas were studied for human leukocyte antigen (HLA) class I and Il express ion, and for the presence of point mutations in codon 12 of the K-ras gene. HLA class I loss was detected in 18 carcinomas, and most of the tumors (43 cases) were found negative for HLA class II antigen express ion by the APAAP technique with specific monoclonal antibodies. Analys is using the polymerase chain reaction (PCR), together with selective hybridization using mutation-specific synthetic oligonucleotides, demo nstrated K-ras mutations in five cases, all of them corresponding to t he adenocarcinoma subtype (31.2% of the adenocarcinomas included in ou r study) with a poor degree of differentiation. We did not find any co rrelation between K-ras mutations and HLA class I and II expression in bronchogenic carcinomas. Therefore, it would appear that downregulati on of MHC antigens by point mutations of K-ms does not take place in v ivo.