Nuclear oncogenes and alpha-fetoprotein gene expression in hepatoma cell lines.

We have previously demonstrated a correlation between the kinetics of activation of the nuclear oncogenes c-fos, c-jun and c-myc and the alpha-fetoprotein (AFP) gene in adult rat hepatocytes proliferating in culture, which led us to raise the hypothesis of a possible regulation of the AFP gene by nuclear oncogenes. Whether the mechanisms of AFP gene expression in normal and transformed hepatocytes are similar is unknown. In this study we have searched for a possible correlation between the basal level of AFP gene expression, by several hepatoma cell lines that express the AFP gene differently, and the basal level of expression of the nuclear oncogenes c-fos, c-jun and c-myc. The analysis has been performed at the mRNA and protein levels. Our results demonstrate that cell lines that strongly express the AFP gene do not express higher levels of nuclear oncogenes than cell lines with weak expression of the AFP gene. These results, therefore, do not support a direct involvement of nuclear oncogenes on the basal level of AFP gene expression in hepatoma cell lines.