Expression Pattern of the Genes for Different Members of the Heat-Shock Protein 70 Family, Ornithine Decarboxylase, and c-Ha-ras During the Early Stages of Hepatocarcinogenesis

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Abstract
Northern blot analysis with specific probes indicates that, in the liver of normothermic rats under the carcinogenic regimen of Solt and Farber (Nature 263:701, 1976), diethylnitrosamine (DEN), 2-acetylaminofluorene (AAF), and partial hepatectomy (PH), either alone or in combination, do not induce the expression of the heat-shock protein 70 (hsp70) gene family. On the contrary, the inducibility of hsp70 mRNAs in the liver of heat-shocked animals is maintained throughout the treatment, as it is in nodules that are found in the liver 2 weeks posttreatment. The steady-state level of the constitutive hsp70-related cognate protein (hsc73) mRNA, which is known to be particularly high in fast-growing cells, increases above the normal level only during liver regeneration, stays at a high level up to 8 days after hepatectomy, independently of any associated exposure to carcinogenic chemicals, and is practically unchanged in the nodules. Ornithine decarboxylase mRNA increases only in livers of normothermic rats at 16 h of regeneration. The expression of the c-Ha-ras oncogene increases slightly, but steadily, during the carcinogenic treatment and persists at a high level when other changes have subsided.