Quantitative and/or qualitative changes in the p21-H-ras post-translational products in regenerating liver and during hepatocarcinogenesis.

Using Western immunoblot analysis with the Ras-10 monoclonal antibody (MAb), we characterized 4 post-translational products of the c-H-ras gene in rat tissues, and showed that they were readily distinguished from the normal p21-N-ras or Val12 mutant p21-H-ras products. In the present study, we used this approach to compare the electrophoretic pattern of p21-H-ras during chemically induced hepatocarcinogenesis in rats with that in control liver samples. Three types of pattern were defined in the liver samples taken at various stages of malignant progression. The first type, like all the 18 normal samples analyzed, was characterized by a predominant intensity of spot a (corresponding to the palmitoylated p21-H-ras product). This was observed in all the samples at the stage of foci and only in a proportion of nodular or tumoral tissues. The second type of pattern deviates from this normal basal pattern by a higher relative level in one or more of the precursors of the fully processed p21-H-ras product. It was observed in all liver samples at the stage of nodules and in a proportion of tumors, but also in all samples from fetal or regenerative liver, thus suggesting an association with high proliferative activity of the hepatocytes. The third type of pattern was characterized by the presence of spots never detected in any of the normal rat tissue or cells that we investigated. Abnormal spots were observed in nodular liver samples and in hepatocarcinomas, indicating that they probably correspond to mutant p21-H-ras products. The fact that the 2 types of abnormal products were not constantly associated with neoplasms indicates that if they play a role in their induction or maintenance this may also be achieved in an independent way, perhaps, but not necessarily, involving another mutation of the ras gene.