Spontaneous and 5-Azacytidine-Induced Reexpression of Ornithine Carbamoyl Transferase in Hepatoma Cells

Rat hepatoma cells that do not synthesize the hepatic enzyme ornithine carbamoyl transferase spontaneously give rise to producing cells at a low frequency. Reexpression of this differentiation trait is strongly increased by 5-azacytidine treatment, suggesting that hypermethylation plays a critical role in the impaired expression of the ornithine carbamoyl transferase gene in hepatoma cells.