In vitro PKC412 cytotoxicity in childhood ALL with and without MLL gene rearrangements. (A) MTT dose-response curves showing the mean cytotoxic response to PKC412 in primary leukemic cells from infants with MLL (n = 29), noninfants with ALL (n = 19), and FLT3/ITD⁺ AML patients (n = 5). (B) MTT dose-response curves showing the mean cytotoxic response to PKC412 in infant MLL samples expressing high levels of FLT3 (n = 9) compared to infant MLL samples expressing lower FLT3 levels (n = 8). Error bars represent SEM.