The role of ribonuclease in regression of lymphosarcoma P1798.

RNase activity increases in P1798 lymphoid tumors main tained in BALB/c mi ce that are undergoing irevitro drug-induced regression. Corticosteroids, 5-fluorouracil, vincristine, vinblastine, methotrexate, and triethylenemelamine produce re gression of appropriate sublines of P1798 lymphosarcoma as well as an increase in RNase activity. Numerous other agents tested had no effect either on tumor regression or on RNase activity. Separation of the different cell types by glass bead chromatosrraphy showed that the increased RNase activity was in the purified tumor lymphocytes.