DNA in cytosol fractions obtained by differential centrifugation of homogenates of rapidly growing liver tumors

Abstract

Preliminary work revealed that the cytosol fractions obtained by differential centrifugation of homogenates of the rapidly growing Morris hepatomas 7777 and 7288CTC contained substantially more DNA than could be detected with the more slowly growing hepatoma 5123C or the liver of tumor-bearing rats. The amount of DNA in the cytosol fractions of the rapidly growing hepatomas was decreased by concentrations of cations which are known to promote precipitation of solubilized chromatin. Data on the incorporation of [ 3H]thymidine into DNA of nuclear and cytosol fractions and the time-dependent effects of hydroxyurea were compatible with initial nuclear synthesis and later release of the DNA seen in the cytosol fractions. The amount of this DNA was increased in larger tumors and was less in isolated cells than in solid tumors. Postmortem changes in the liver and hepatoma 5123C, but not in hepatomas 7777 and 7288CTC, resulted in a large increase in DNA appearing in the cytosol fraction. The results indicated that the measurement of DNA in cytosol fractions may serve as a guide to the existence of necrosis in tumors, but is not always proportional to the degree of necrosis.