title: Modulation of intracellular metabolism of cytosine arabinoside in acute myeloid leukemia by granulocyte-macrophage colony-stimulating factor.
abstract: The current study investigated the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on the intracellular metabolism and cytotoxicity of 1-beta-D-arabinofuranosylcytosine (araC) in leukemic cells of 45 patients with acute myeloid leukemia (AML). AML blasts from bone marrow (BM) (n = 39) and peripheral blood (PB) (n = 17) were incubated for 48 h with or without GM-CSF (100 U/ml) followed by a concurrent treatment with increasing concentrations of araC (0.06-100 microM) for an additional 24 h. After GM-CSF a 1.5-8.4-fold (median 2.3) increase in 3H-araC incorporation into the DNA was observed in ten of 14 peripheral blast specimens and in 23 of 28 bone marrow samples, 18 of whom also showed an enhanced 3H-TdR incorporation (1.5-8.5-fold, median 2.0-fold). Four different types of response were identified when analyzing 3H-araC incorporation into the DNA of bone marrow samples in relation to the applied araC dose: (i) 8/28 cases had increases of the araC incorporation at all araC dose levels applied (0.06-100 microM), (ii) 12/28 at low araC concentrations only (0.06-1.0 microM), (iii) 3/28 at high araC concentrations only (10-100 microM), and (iv) 5/28 showed no increase at any dose level given. Hence, 20 of the 23 responding patients revealed a GM-CSF induced enhancement of araC incorporation at low or conventional doses of araC (0.06-1.0 microM). Fourteen of the 18 cases with concomitant rises of 3H-TdR and 3H-araC incorporation into the DNA after GM-CSF had elevated DNA polymerase alpha activity (16-531%, median 72%) and in ten cases overall DNA polymerase activity was enhanced (10-70%, median 22.5%). In contrast, thymidine kinase (TK) and deoxycytidine kinase (dCK) activity were elevated after GM-CSF in only ten and five patients, respectively. An increase in the fraction of cells in S phase was found in 11/21 bone marrow specimens and in 5/9 peripheral blast samples. However, no correlation was observed between increases in the proportion of cells in S phase and enhancements in enzyme activities. In 13 cases the cytotoxicity of araC with and without GM-CSF was assessed by means of a blast cell colony assay. Preincubation with GM-CSF increased the araC mediated cytotoxicity in ten of 13 patients by a median of 3.2-fold (range 2.2-229-fold). The respective LD50 values for araC were reduced from 0.45 to 0.19 microM on average.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Department of Internal Medicine, Georg-August-Universität, Göttingen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Reuter
authors.forename: U
authors.initials: U
authors.lastname: Auf der Landwehr
authors.forename: E
authors.initials: E
authors.lastname: Schleyer
authors.forename: M
authors.initials: M
authors.lastname: Zühlsdorf
authors.forename: C
authors.initials: C
authors.lastname: Ameling
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: D000293:Adolescent; D000328:Adult; D000368:Aged; D001085:Arabinofuranosylcytosine Triphosphate / Q000378:metabolism; D003561:Cytarabine / Q000378:metabolism* / Q000494:pharmacology; D004257:DNA Polymerase II / Q000378:metabolism; D004273:DNA, Neoplasm / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D003842:Deoxycytidine Kinase / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism* / Q000473:pathology; D008875:Middle Aged; D016196:S Phase; D013937:Thymidine Kinase / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
chemical_list: D004273:DNA, Neoplasm; D003561:Cytarabine; D001085:Arabinofuranosylcytosine Triphosphate; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013937:Thymidine Kinase; D003842:Deoxycytidine Kinase; D004257:DNA Polymerase II; D004259:DNA-Directed DNA Polymerase