title: [Low dose methotrexate combined with GM-CSF induced differentiation of U937 cells].
abstract: OBJECTIVE
  To explore the effect of methotrexate on acute monoblastic leukemia cells, and the potential role of low-dose methotrexate in the treatment of monoblastic leukemia.
  
  
  METHODS
  By using U937 cell line as a model, the induced differentiation of MTX or GM-CSF or their combination was detected by NBT reduction test, morphological observation and CD(14) expression. TRAP-ELISA was used for measuring telomerase activity.
  
  
  RESULTS
  After incubation with 20 nmol/L methotrexate for 24, 48, 72 and 96 hours, the size of the U937 cells increased, the nuclear/plasma ratio gradually decreased, NBT reductive test became positive, and CD(14) positive cells increased from 3% to 20% after 72 hours incubation, indicating partial differentiation. Treatment of U937 cells with 100 U/ml GM-CSF alone failed to induce differentiation. However, GM-CSF combined with low-dose methotrexate resulted in 63% of differentiated cells after 72 hours incubation, and telomerase activity of the U937 cells decreased from 2.11 (before treatment) to 1.48, 0.77, 0.24 (after treatment for 24, 48, 72 hrs respectively). The extent of the decrease of telomerase activity was in proportion with the degree of differentiation.
  
  
  CONCLUSIONS
  Monoblastic leukemia might be treated with low-dose methotrexate plus GM-CSF as a differentiation induction regimen.
authors.affiliation: Xinhua Hospital and Shanghai Children's Medical Center, Shanghai Second Medical University, Shanghai 200127, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Long-jun
authors.initials: LJ
authors.lastname: Gu
authors.forename: Da-ming
authors.initials: DM
authors.lastname: Ying
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects*; D045744:Cell Line, Tumor; D004357:Drug Synergism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D007948:Leukemia, Monocytic, Acute / Q000473:pathology; D008727:Methotrexate / Q000008:administration & dosage / Q000494:pharmacology*; D019098:Telomerase / Q000187:drug effects / Q000378:metabolism; D020298:U937 Cells
chemical_list: D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019098:Telomerase; D008727:Methotrexate