Increased DNA polymerase activity in a series of rat hepatomas.

Abstract

It has previously been reported that there may be a correlation between DNA synthesis and the growth of a series of rat hepatomas. This study describes a similar correlation that exists with DNA polymerase activity partially purified from normal liver and from 12 types of hepatomas. Not only are the hepatomas characterized by increased DNA polymerase levels, but the hepatoma enzymes prefer denatured DNA as primer. Normal and regenerating rat liver DNA polymerase apparently prefer native DNA primer. Another consistent difference was noted between hepatomas and normal liver. In all instances the deoxyribonuclease activity with denatured DNA as substrate was lower in tumors than in the livers of normal rats or of host liver. Therefore, it appears that increased DNA synthesis by these tumors is supported by a rise in key anabolic enzyme activity and a fall in catabolic enzymes. Characterization of these enzyme systems will be described in subsequent reports.