title: Differential effect of GM-CSF pretreatment on intracellular Ara-C metabolism in normal bone marrow mononuclear cells vs acute myeloid leukemia (AML) blasts.
abstract: The effect of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) on the intracellular metabolism of cytosine arabinoside (Ara-C) was comparatively analyzed in normal bone marrow mononuclear cells (NBMMC) from eight healthy volunteers and in leukemic blasts from 50 patients with acute myeloid leukemia (AML). Pretreatment with GM-CSF (100 U/ml) for 48 h resulted in a significant enhancement of DNA synthesis in both cell types: 21 of 35 AML specimens were found to be responsive to GM-CSF as defined by an increase of 3H-TdR incorporation into the DNA > 1.5-fold while NBMMC from normal donors were responsive in all cases. In GM-CSF responsive AML blasts, overall DNA polymerase and DNA polymerase alpha activity increased from a median of 84.4 to 96.1 and from 3.45 to 5.2 pmol/min x mg as compared to a median of 96.7 to 189.9 and 1.2 to 2.2 pmol/min x mg in NBMMC (P < 0.05). Median Ara-C-mediated inhibition of DNA synthesis was significantly more effective in AML blasts as compared to NBMMC (76.5 vs 55.0% at 0.05 microM and 99.0 vs 96.0% at 5.0 microM Ara-C, P < 0.01) but was not influenced by GM-CSF pretreatment. Similarly, intracellular Ara-CTP levels were higher in AML blasts as compared to NBMMC (median of 46.9 vs 18.7 at 1 microM, 167.8 vs 48.0 at 10 microM and 337.5 vs 59.5 ng/10(7) cells at 100 microM extracellular Ara-C, P < 0.01) but showed no enhancement in the presence of GM-CSF. Median deoxycytidine (DCK) and thymidine kinase (TK) activity were only slightly increased in AML blasts after GM-CSF priming. In contrast, NBMMC revealed a significant increase in TK activity after GM-CSF pretreatment (from a median of 1.9 to 3.6 pmol/min x mg, P = 0.039). At low; intermediate and high extracellular Ara-C concentrations GM-CSF pretreatment resulted in a significant enhancement of the 3H-Ara-C incorporation into the DNA in both GM-CSF responsive AML blasts and NBMMC (median of 1.3 to 2.1- and 1.4 to 1.6-fold, P < 0.05). GM-CSF non-responsive AML blasts showed no change in 3H-Ara-C incorporation into the DNA in response to GM-CSF at low Ara-C concentrations but significant increases at intermediate and high extracellular Ara-C concentrations (median increases of 1.63-fold at 1.06 microM with P = 0.01 and 1.37-fold at 10 microM extracellular Ara-C with P = 0.0+005). NBMMC revealed significantly lower GM-CSF-induced increases of the 3H-Ara-C incorporation into the DNA as compared to the effect of GM-CSF priming on DNA synthesis (median increases of 1.4 to 1.7-fold vs 2.6-fold, P < 0.05). These data reveal a different effect of GM-CSF priming on the metabolism of Ara-C in normal vs leukemic cells which may cause a preferential increase in the antileukemic cytotoxicity of Ara-C in the presence of GM-CSF.
authors.affiliation: Department of Hematology, University of Göttingen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Reuter
authors.forename: E
authors.initials: E
authors.lastname: Schleyer
authors.forename: C
authors.initials: C
authors.lastname: Rolf
authors.forename: B
authors.initials: B
authors.lastname: Wörmann
authors.forename: T
authors.initials: T
authors.lastname: Büchner
authors.forename: W
authors.initials: W
authors.lastname: Hiddemann
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000964:Antimetabolites, Antineoplastic / Q000378:metabolism*; D001853:Bone Marrow / Q000187:drug effects* / Q000473:pathology; D003561:Cytarabine / Q000378:metabolism*; D004273:DNA, Neoplasm / Q000096:biosynthesis; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D003842:Deoxycytidine Kinase / Q000378:metabolism; D004347:Drug Interactions; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D007951:Leukemia, Myeloid / Q000473:pathology*; D008875:Middle Aged; D013937:Thymidine Kinase / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D000964:Antimetabolites, Antineoplastic; D004273:DNA, Neoplasm; D003561:Cytarabine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013937:Thymidine Kinase; D003842:Deoxycytidine Kinase; D004259:DNA-Directed DNA Polymerase