Chromatin alterations and gene function disorder in MC-29 virus-derived hepatoma.

The disorder of gene expression in hepatomas was studied by following certain metabolic alterations (enzyme stimulation, nucleic acid labeling) after glucocorticoid treatment and analyzing the site of action of glucocorticoids. Compared to normal liver, the MC-29 virus-derived transplantable hepatoma (VTH) responded abnormally to glucocorticoids, which failed to stimulate the activity of certain enzymes (glucose-6-phosphatase, aryl hydrocarbon hydroxylase) or to inhibit DNA synthesis. Since the binding capacity of the cytosol steroid receptor was the same in liver and VTH but the interaction between the steroid receptor and DNA was reduced in VTH, it was concluded that structural alterations of chromatin nonhistones--including processed steroid receptor--may be responsible for the lack of physiological responses to steroids in VTH. Furthermore, the increased proportion or repetitive sequences in VTH DNA may be a feature of the disorder of gene regulation in malignant cells.