Background : Treatment result of acute myelogenous leukemia(AML) depend on the outcome of remission induction chemotherapy. Most antileukenic drugs are mainly effective in the S phase of the cell cycle but a substantial proportion of AML blasts are in the chemoresistant Go phase. This study was conducted to confirm that granulocyte-macrophage colony-stimulating factor(GM-CSF) induced recruitment and methotrxate induced synchronization in AML blasts. Also the combined preincubation of GM-CSF and MTX resulted in a significant increase in S phase fraction to provide a rationale for a novel approach to the treatment of AML.
Method : The AML cell lines(HL-60 and KG-1) were preconditioned with GM-CSF and/or MTX to modulate the cell cycle. HL-60 and KG-1 cells(cell density 1×10⁵/mL)were preincubated with GM-CSF and/or MTX on various dose-schedules. In vitro conditions for GM-CSF and MTX were analyzed to maximize S phase fraction by flow cytometry after dual labeling with bromodeoxyuridine and propidium iodied.
Result : The optimum dose and duration of precondition were found to be 1ng/mL for 48 hours for GM-CSF and 0.04μM for 24 hours ofr MTX. Precondition with the combination of GM-CSF and MTX(GM-CSF for 48 hours and for the last 24 hours with MTX)showed most effective increase in S phase fraction. There was an increase in S phase cells: from 30.5% in control to 86.1% in the combination(HL-60) and from 30.4% in control to 51.4% in the combination(KG-1).
Conclusion: This study confirmed GM-CSF induced recruitment and MTX induced synchronization in AML blasts and combined GM-CSF and MTX coul modulate cell cycle synergistically. These results suggest that simultaneous GM-CSF and MTX priming with cell cycle specific drug such as ara-C could be a new treatment protocol to improve the outcome of AML.

Keywords: Acute myelogenous leukemia, Granulocyte-macrophage colony-stimulating factor, Methotrexate, Recruitment, Synchronization