title: Comparison of the cytotoxicity of cladribine and clofarabine when combined with fludarabine and busulfan in AML cells: Enhancement of cytotoxicity with epigenetic modulators.
abstract: Clofarabine (Clo), fludarabine (Flu), and busulfan (Bu) combinations are efficacious in hematopoietic stem cell transplantation for myeloid leukemia. We sought to determine whether the more affordable drug cladribine (Clad) can provide a viable alternative to Clo, with or without panobinostat (Pano) and 5-aza-2'-deoxycytidine (DAC). Both Clad+Flu+Bu and Clo+Flu+Bu combinations showed synergistic cytotoxicity in KBM3/Bu250(6), HL60, and OCI-AML3 cell lines. Cell exposure to these drug combinations resulted in 60%-80% inhibition of proliferation; activation of the ATM pathway; increase in histone modifications; decrease in HDAC3, HDAC4, HDAC5 and SirT7 proteins; decrease in mitochondrial membrane potential; activation of apoptosis and stress signaling pathways; and downregulation of the AKT pathway. These drug combinations activated DNA-damage response and apoptosis in primary cell samples from AML patients. At lower concentrations of Clad/Clo, Flu, and Bu, inclusion of Pano and DAC enhanced cell killing, increased histone modifications and DNA demethylation, and increased the levels of P16/INK4a, P15/INK4b and P21/Waf1/Cip1 proteins. The observed DNA demethylating activity of Clad and Clo may complement DAC activity; increase demethylation of the gene promoters for SFRP1, DKK3, and WIF1; and cause degradation of β-catenin in cells exposed to Clad/Clo+Flu+Bu+DAC+Pano. The overlapping activities of Clad/Clo+Flu+Bu, Pano, and DAC in DNA-damage formation and repair, histone modifications, DNA demethylation, and apoptosis may underlie their synergism. Our results provide a basis for supplanting Clo with Clad and for including epigenetic modifiers in the pre-hematopoietic stem cell transplantation conditioning regimen for myeloid leukemia patients.
authors.affiliation: Department of Stem Cell Transplantation and Cellular Therapy, University of Texas MD Anderson Cancer Center, Houston, TX, USA. Electronic address: bvaldez@mdanderson.org.
authors.forename: Benigno C
authors.initials: BC
authors.lastname: Valdez
authors.affiliation: Department of Stem Cell Transplantation and Cellular Therapy, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Murray
authors.affiliation: Department of Stem Cell Transplantation and Cellular Therapy, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Ji
authors.affiliation: Department of Stem Cell Transplantation and Cellular Therapy, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Stem Cell Transplantation and Cellular Therapy, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Uday
authors.initials: U
authors.lastname: Popat
authors.affiliation: Department of Stem Cell Transplantation and Cellular Therapy, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Champlin
authors.affiliation: Department of Stem Cell Transplantation and Cellular Therapy, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Borje S
authors.initials: BS
authors.lastname: Andersson
mesh_terms: D000227:Adenine Nucleotides / Q000008:administration & dosage / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology; D017209:Apoptosis; D001087:Arabinonucleosides / Q000008:administration & dosage / Q000494:pharmacology*; D064007:Ataxia Telangiectasia Mutated Proteins / Q000378:metabolism; D002066:Busulfan / Q000008:administration & dosage / Q000494:pharmacology*; D045744:Cell Line, Tumor; D017338:Cladribine / Q000008:administration & dosage / Q000494:pharmacology*; D000077866:Clofarabine; D044127:Epigenesis, Genetic; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D060888:Real-Time Polymerase Chain Reaction; D014740:Vidarabine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D000970:Antineoplastic Agents; D001087:Arabinonucleosides; D017338:Cladribine; D000077866:Clofarabine; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D014740:Vidarabine; D002066:Busulfan; C024352:fludarabine