title: GM-CSF and asparaginase potentiate ara-C cytotoxicity in HL-60 cells.
abstract: In preparation for a clinical trial using GM-CSF on days 4-10 of sequential high-dose cytarabine (ara-C) and asparaginase (ASNase) on days 1-3 and 8-10, potential interactions between the protein synthesis inhibitor ASNase and GM-CSF were evaluated. Granulocyte-macrophage colony-stimulating factor (GM-CSF) can stimulate acute myeloid leukemia (AML) cells to proliferate in vitro and in vivo. Log phase HL-60 cells were exposed to ara-C (10 microM x 3 h) and/or ASNase (10 U/ml during the last 2 h of ara-C). Ara-C and/or ASNase was removed and cells were incubated with or without GM-CSF (10 ng/ml). After 24, 48 and 72 h of GM-CSF there was no significant difference in the S phase fraction of cells exposed to ASNase prior to GM-CSF. Soft agar cloning efficiency was determined after retreatment with ara-C +/- ASNase 24 h into the GM-CSF incubation. GM-CSF enhanced cytotoxicity for all combinations, although this effect was of borderline significance (P = 0.0621); addition of ASNase to the treatment regimen significantly (P = 0.0229) enhanced cytotoxicity without any evidence of a negative interaction with GM-CSF. In addition, ara-C metabolism was assessed during simultaneous exposure to ara-C (10 microM x 3 h) +/- ASNase (10 U/ml the last 2 h) +/- GM-CSF (10 ng/ml beginning 24 h prior to ara-C). Ara-C incorporated into DNA (P = 0.0302) and ara-CTP formation (P = 0.0084 and P = 0.0003 at 2 and 3 h timepoints, respectively) were both increased significantly by GM-CSF, with modest non-significant increases with ASNase exposures. Neither ASNase nor GM-CSF inhibited the effects of the other in this in vitro model. Therefore, when appropriately scheduled, both GM-CSF and ASNase may potentiate ara-C cytotoxicity.
authors.affiliation: Department of Medicine, Wake Forest University, Bowman Gray School of Medicine, Winston-Salem, NC 27157-1082.
authors.forename: B L
authors.initials: BL
authors.lastname: Powell
authors.forename: L M
authors.initials: LM
authors.lastname: Wang
authors.forename: B W
authors.initials: BW
authors.lastname: Gregory
authors.forename: L D
authors.initials: LD
authors.lastname: Case
authors.forename: G L
authors.initials: GL
authors.lastname: Kucera
mesh_terms: D001085:Arabinofuranosylcytosine Triphosphate / Q000378:metabolism; D001215:Asparaginase / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology*; D004273:DNA, Neoplasm / Q000737:chemistry; D004357:Drug Synergism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000473:pathology*; D014411:Neoplastic Stem Cells / Q000187:drug effects*; D016196:S Phase / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014410:Tumor Stem Cell Assay
chemical_list: D004273:DNA, Neoplasm; D003561:Cytarabine; D001085:Arabinofuranosylcytosine Triphosphate; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D001215:Asparaginase