title: In AML cell lines Ara-C combined with purine analogues is able to exert synergistic as well as antagonistic effects on proliferation, apoptosis and disruption of mitochondrial membrane potential.
abstract: The pyrimidine analogue Ara-C and the purine analogues fludarabine and cladribine (2-CdA) are essential compounds in the treatment of acute myeloid leukemia (AML). Inhibition of cell proliferation and induction of apoptosis are the major mechanisms of cytotoxic agents to cause tumor cell death. Therefore, we studied whether Ara-C in combination with the purine analogues exerts synergistic or antagonistic effects on cell proliferation, phosphatidylserine exposure and disruption of mitochondrial membrane potential (MMP) in the AML cell lines HL60 and HEL. Furthermore, effects of the combination of Ara-C with bendamustine, a new bifunctional agent with alkylating activity and a purine nucleus, was investigated. Assessment by combination index analysis showed that Ara-C combined with fludarabine or bendamustine exhibited additive to antagonistic effects on inhibition of cell proliferation, induction of apoptosis as well as on disruption of mitochondrial membrane potential, independent of a simultaneous or consecutive (purine analogues before Ara-C) incubation schedule. In contrast, the combination of Ara-C with 2-CdA exclusively yielded synergistic effects. While inducing IC50 levels of apoptosis neither the antagonistic nor the synergistic drug combinations caused a specific expression pattern of apoptosis-associated proteins such as the pro- or antiapoptotic Bcl-2 family members, executioner caspases, IAPs (inhibitor of apoptosis proteins), proapoptotic Par-4, PARP, or p53. In conclusion, we here demonstrate that the in vitro efficacy of drug combinations containing Ara-C and purine analogues depends on the purine analogue applied, whereas incubation schedules or escalating dosages do not contribute to the synergistic effects.
authors.affiliation: Department of Internal Medicine III, Hematology and Oncology, Johann Wolfgang Goethe-University, University Hospital, Theodor-Stern-Kai 7, 60590 Franfurt/Main, Germany. chow@em.uni-frankfurt.de
authors.forename: Kai U
authors.initials: KU
authors.lastname: Chow
authors.forename: Simone
authors.initials: S
authors.lastname: Boehrer
authors.forename: Simone
authors.initials: S
authors.lastname: Napieralski
authors.forename: Daniel
authors.initials: D
authors.lastname: Nowak
authors.forename: Andrea
authors.initials: A
authors.lastname: Knau
authors.forename: Dieter
authors.initials: D
authors.lastname: Hoelzer
authors.forename: Paris S
authors.initials: PS
authors.lastname: Mitrou
authors.forename: Eckhart
authors.initials: E
authors.lastname: Weidmann
mesh_terms: D000208:Acute Disease; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology*; D004336:Drug Antagonism; D004357:Drug Synergism; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects; D007951:Leukemia, Myeloid / Q000188:drug therapy / Q000473:pathology*; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000648:ultrastructure; D011687:Purines / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: D011687:Purines; D003561:Cytarabine