Changes in polysomal polyadenylated RNA and alpha-fetoprotein messenger RNA during hepatocarcinogenesis

Polysomal polyadenylated RNA was isolated from preneoplastic and neoplastic livers obtained from rats kept on a choline-deficient diet containing ethionine for 8 and 25 to 32 weeks, respectively. Normal, preneoplastic, and neoplastic liver polysomal messenger RNA's (mRNA's) were hybridized with homologous and heterologous 3H-labeled complementary DNA's (cDNA's). The results show that, in terms of RNA mass, all or most of the polysomal polyadenylated RNA present in preneoplastic or neoplastic liver is also present in normal liver. This was induced by the similar extent of hybridization between [3H]cDNA transcribed from preneoplastic or neoplastic liver mRNA's with their homologous mRNA's and with mRNA from normal liver. Conversely, most or all of the polysomal polyadenylated RNA of normal liver is also found in preneoplastic and neoplastic livers, as indicated by the extent of hybridization of [3H]cDNA transcribed from normal liver with mRNA's from normal, preneoplastic, and neoplastic livers. Shifts in the relative abundance of mRNA sequences were detected in the polysomal mRNA of preneoplastic livers and especially in the mRNA of neoplastic liver. Hybridization of alpha-fetoprotein cDNA with liver polyadenylated RNA showed a substantial increase in alpha-fetoprotein mRNA content after 8 and 15 weeks of feeding the carcinogenic diet. Similar experiments using globin cDNA failed to show an increase in globin mRNA content in preneoplastic livers.