The capacity of rat hepatoma cell lines for O6-methylguanine-DNA repair correlates with their status of differentiation.

O6-Methylguanine-DNA methyltransferase activity, i.e., the capacity of cells to transfer the methyl group from O6-methylguanine in DNA to protein, was determined in 10 hepatoma cell lines, all derived from Reuber H35 hepatoma but differing in their status of differentiation. Methyltransferase activity of the six differentiated lines tested was at least 4-5 times higher than that of two dedifferentiated lines. The activity of the two poorly differentiated lines examined was low to intermediate. Some of the differentiated lines possessed methyltransferase activities comparable to those in hepatocytes freshly isolated from adult rat. The results suggest that certain differentiated hepatoma lines are capable of mimicking liver in the capacity for repair of O6-methylguanine lesions and in this respect may be useful as model systems for studying liver-specific effects of monofunctional alkylating agents.