DNA ligation in relation to DNA strand breaks in phytohemagglutinin-stimulated blast cells from acute lymphoblastic and nonlymphoblastic leukemia

DNA ligase activity was determined in the WBCs from 306 cases of acute lymphoblastic leukemia (ALL) and acute nonlymphocytic leukemia (ANLL). In T-ALL cells this activity was either low or absent. DNA analysis by nucleoid, alkaline elution, and alkaline sucrose centrifugation after cells were embedded in agarose inserts has shown more DNA breaks in T- ALL than in ANLL blasts. Phytohemagglutinin stimulation of T-ALL blasts resulted in the apparent joining of the DNA breaks. Apparent identical results can be obtained by the incubation of DNA with exogenous DNA ligase. The authors suggest that this enzyme is a crucially regulated step of replication and subsequent proliferation in this type of leukemia.