A comparison of DNA and DNA-binding protein levels in malignant disease

Measurements of serum concentrations of DNA and the DNA-binding protein C3DP by radioimmunoassay showed that the levels of both substances tend to increase in cancer patients during active malignant disease. In most cases, the levels returned to normal during chemotherapy-induced remission; however, the changes in concentration for DNA and C3DP did not occur simultaneously, and no correlation was found between their levels. The sera of cancer patients contained a strong inhibitor of DNAse. We examined the possibility that C3DP may have such an inhibitory effect by binding to DNA and preventing the action of DNAse. The enzyme was fully active in the presence of purified C3DP, indicating that the DNAse inhibitor in cancer serum was a substance other than C3DP. Although the relationship between DNA and the DNA-binding protein remains unknown, their measurement may have diagnostic and prognostic value.