Combinations of the FLT3 inhibitor CEP-701 and chemotherapy synergistically kill infant and childhood MLL-rearranged ALL cells in a sequence-dependent manner.
Mixed lineage leukemia (MLL) rearrangements occur in 80% of infants and 5% of older children with acute lymphoblastic leukemia (ALL). These cases have a poor prognosis with current therapy. The FLT3 kinase is overexpressed and constitutively activated in MLL-rearranged ALL cells. The FLT3 inhibitor CEP-701 selectively kills these cells, but is unlikely to be curative if used as monotherapy. To identify potentially synergistic combination strategies, we studied CEP-701 and six standard chemotherapeutic agents in three sequences of exposure (S1: chemotherapy followed by CEP-701, S2: simultaneous exposure to both; and S3: CEP-701 followed by chemotherapy) using MLL-rearranged ALL cell lines and patient bone marrow samples. MTT cytotoxicity and annexin V binding apoptosis assays were used to assess antileukemic effects. Combination indices (CI) were calculated for each combination (CI<0.9 - synergistic; CI 0.9-1.1 - additive; CI>1.1 - antagonistic). A striking pattern of sequence-dependent synergy was observed: S1 was markedly synergistic (mean CI=0.59+/-0.10), S2 was additive (mean CI=0.99+/-0.09) and S3 was antagonistic (mean CI=1.23+/-0.10). The sequence dependence is attributable to the effect of CEP-701 on cell cycle kinetics, and is mediated specifically by FLT3 inhibition, as these effects are not seen in control cells without activated FLT3.
Brown
P
P
Department of Oncology, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD 21231, USA.
Levis
M
M
McIntyre
E
E
Griesemer
M
M
Small
D
D
D000970:Antineoplastic Agents / Q000008:administration & dosage*; D002227:Carbazoles / Q000008:administration & dosage* / Q000494:pharmacology; D045744:Cell Line, Tumor; D002648:Child; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005663:Furans; D016193:G1 Phase / Q000187:drug effects; D015321:Gene Rearrangement; D011495:Histone-Lysine N-Methyltransferase; D006801:Humans; D007211:Indoles / Q000008:administration & dosage* / Q000494:pharmacology; D007223:Infant; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage*; D051941:fms-Like Tyrosine Kinase 3 / Q000037:antagonists & inhibitors*
D000970:Antineoplastic Agents; D002227:Carbazoles; D005663:Furans; D007211:Indoles; C497422:KMT2A protein, human; D047428:Protein Kinase Inhibitors; D051788:Myeloid-Lymphoid Leukemia Protein; C119379:lestaurtinib; D011495:Histone-Lysine N-Methyltransferase; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3