Effect of Corticosteroids on Ribonuclease and Nucleic Acid Content in Lymphosarcoma P1798.

Administration of 9a-fluoroprednisolone to mice bearing the corticoid-sensitive strain of Lymphosarcoma PI 798 resulted in a prompt regression of tumor size. This regression was accompanied by a selective decrease in tumor RNA. Tumor DNA con centration remained at control levels. These changes were preceded by an increased tumor ribonuclease activity in homogenates of tumor after the in vivoadministration of corticosteroids. Regression of tumor size and activation of tumor ribonuclease were not observed in the resistant strain of tumor after steroid administration.