Increase in nuclease activity as a possible means for detecting tumor cell sensitivity to anticancer agents

Histochemical activity of nucleases was investigated in sensitive and resistant rat tumors at several periods after a single dose of cyclophosphamide and was compared with that in a control group of untreated tumors. Intense increase of nuclease activity(mainly that of acid DNAse) appeared only in the cells of the sensitive tumors at 12 hours, reaching its maximum three days after drug administration. Untreated malignant tumors usually have variable amounts of spontaneous necrosis with high nuclease activity. Not the absolute values of high nuclease activity but only the increase of such activity from the basal level of untreated tumors to that measured at frequent periods after trial treatment may be suggested as an early marker of therapeutically induced tumor cell necrosis. However, more investigation is needed before such a marker might be applied as a test for tumor sensitivity to therapeutic agents.