CONSTITUTIVE ENDONUCLEASE TO INDUCE HIGH-MOLECULAR-WEIGHT OR INTERNUCLEOSOMAL DNA FRAGMENTATION IN FRESHLY ISOLATED LEUKEMIA-CELLS

Using an autodigestion method, we investigated endogenous endonuclease (s) in leukemia cells freshly obtained from pediatric patients with va rious types of leukemia. Endonucleolytic activity was found to cause b oth high molecular weight and internucleosomal DNA fragmentation at a neutral pH in whole cell lysates of all common acute lymphoblastic leu kemia (cALL) blasts, which was Mg2+-dependent and Ca2+-independent, Wh ole lysates from most acute myeloblastic leukemia (AML) cells possesse d similar endonuclease activity, but both Mg2+ and Ca2+ were required for the activity. Our results suggest that leukemia cells of different lineages have distinct constitutive endonucleases, which may play a r ole in the occurrence of apoptosis in these cells. (C) 1997 Elsevier S cience Ireland Ltd.