Changes in serum RNase activities in chronic phase and acute crisis of chronic myelocytic leukemia

We investigated serum acid and alkaline RNase activities in 16 cases of acute crisis of chronic myelocytic leukemia (CML), 21 cases of untreated CML, and 13 cases of treated CML, to clarify clinical significance of the determination of RNase activities in acute crisis of CML. We obtained results as follows; the ratio of acid to alkaline Rnase activities (Ac/Al ratio) of chronic phase of CML was 1.64 +/- 0.47 (mean +/- SD) in the untreated cases, and was 1.32 +/- 0.16 in the treated cases. The Ac/Al ratio always indicated over 1.0 in the chronic phase of CML without any relationship to treatments. On the other hand, in the cases of acute crisis, the Ac/Al ratio was significantly lowered (0.94 +/- 0.22) as compared to the chronic phase of CML (p less than 0.001), and was similar to that of acute leukemia. The acid and alkaline RNase activities of the blast from the patients with acute crisis of CML showed remarkably lower value than those of leukemic cells from patients with chronic phase of CML. Therefore, it was Suggested that the return to normal range of Ac/Al ratio in acute crisis of CML depended on marked decrease of RNase activities of blasts. Thus, serial determinations of the enzyme activities are considered to be one of useful tools for prediction of acute crisis of CML.