Expression of FLT3 in SU5614-resistant and parental FLT3-ITD cell lines. (A) The expression of FLT3 in Ba/F3 FLT3-ITD-R1-4 was analyzed by fluorescence activated cell sorting (FACS) analysis with the use of an anti-CD135 PE-labeled antibody compared with parental FLT3-ITD cells. Open histograms represent isotype control (PE-labeled control antibody); filled histograms show fluorescence intensity of CD135. (B) Lysates were prepared from these cells, and FLT3 expression was determined by immunoblotting with the use of a polyclonal anti-FLT3 antibody. Identical protein loading in all lanes was confirmed by immunoblotting with the use of an anti–β-actin antibody.