Expression Level of Granulocyte-Colony Stimulating Factor Receptor and Effect of Two Forms of G-CSF to in AML1/ETO+ Acute Myelogenous Leukemia.

In our previous study, we have revealed that cases showing remission after treatment with G-CSF mostly had leukemia with AML1/ETO rearrangement and suggested that this finding might be explained by higher expression of G-CSF receptor (G-CSFR) in AML1/ETO⁺ cells than in AML1/ETO⁻ cells. To confirm the relationship between AML1/ETO fusion gene and G-CSFR expression, we applied small interfering RNAs (siRNAs) for efficient suppression of AML1/ETO gene expression and observed the change of G-CSFR expression. Moreover, we investigated the effect of most commonly used two forms of G-CSF (glycosylated lenograstim and nonglycosylated filgrastim) on AML1/ETO positive leuekemic cells and other cell lines. Kasumi-1 cells (AML with AML1/ETO gene rearrangement) were transfected with AML1/ETO specific siRNAs (siAM, siAGF1) and isolated for investigation of G-CSFR gene expression using real time PCR. The proliferation effect of two different forms of G-CSF on was evaluated using Cell-Titer 96® Non-Radioactive Cell Proliferation Assay (Promega Co., Madison, WI, USA). G-CSFR expression was decreased in AML1/ETO gene suppressed cells by both siRNAs. The levels of G-CSFR mRNA were 27% of untreated control with siAGF, 23% with siAM at 16 hours after trasnfection. Both forms of G-CSF significantly stimulated the proliferation of Kasumi-1 cells compared to control cells without G-CSF treatment (40–80% of control increased). The degree of proliferation was similar with different forms of G-CSF (filgrastim and lenograstim) at different concentrations (10, 50 and 100 ng/mL). In K562 cells(chronic myelogenous leukemia), proliferation was increased only at 50ng/ml filgrastim after 72 hours. The CTV-1 cells (AML without AML1/ETO gene rearrangement) showed slightly increased proliferation activities only after 72 hours of lenograstim treatment. In U266 cells (Multiple myeloma) showed no significant response on proliferation with G-CSF. In conclusion, our study revealed that AML1/ETO rearrangement increased the G-CSFR expression and G-CSF had proliferation effect on AML1/ETO-positive cells. Thus, the effect of G-CSF should be considered when we decide the remission or treatment plan, especially for AML1/ETO⁺ AML with high G-CSFR expression.