[The expression of C-myc, N-ras mRNA and its relations to the differentiation of preneoplastic altered hepatocytes].

The expression of C-myc and N-ras mRNA was studied in preneoplastic hepatic lesions induced by multiple small doses of diethylnitrosamine (DEN). Dot blot analysis showed that the expression of C-myc and N-ras mRNA was in elevated levels during the early stage of hepatocarcinogenesis. In situ hybridization in tissue sections demonstrated that the over-expression of C-myc and N-ras mRNA was clearly seen in some of the preneoplastic altered liver cell lesions. In comparison of these over-expressed oncogene lesions with the expression of carbamyl phosphate synthetase I (CPS I), known as a differentiation marker of hepatocytes, in serial sections revealed that almost all of the foci with over-expressed C-myc and/or N-ras mRNA also showed low expression of CPS I mRNA, which means a low differentiation nature of the liver cells. These findings suggested that the overexpression of C-myc and N-ras are closely correlated to the differentiation state of altered liver cells.