Knockdown of Axl gene expression by siRNA. (A) After transfecting Ctrl or Axl siRNA, cells from the MV4;11 human FLT3-ITD⁺ AML cell line were counted in trypan blue at the indicated times. This is the representative of 2 separate experiments and data are the mean ± SD (triplicate). **P < .01. (B) At 3 days after transfection with Ctrl or Axl siRNA, cells from the MV4;11 human FLT3-ITD⁺ AML cell line were stained with annexin V-FITC and PI for detection of apoptosis. Numbers indicate the percentage of each quadrant. This is the representative of 2 separate experiments. (C) Four days after transfection of Ctrl or Axl siRNA, cells from the MV4;11 human FLT3-ITD⁺ AML cell line were harvested and measurement of mRNA expression level of each gene was performed by quantitative real-time RT-PCR. The graph shows fold induction of gene expression by Axl siRNA over Ctrl siRNA with mean ± SEM (n = 3).