Resistance of FLT3-ITD-R4 cell line to SU5614 and activation of STAT5 and MAPK in FLT3-ITD-R1-4 cells in response to the inhibitor. (A) Ba/F3 FLT3-ITD-R4 cells were seeded at a density of 4 × 104 cells/mL in the absence or presence of different concentrations of SU5614 and viable cells were counted after 72 hours by trypan blue exclusion. Values represent means and standard errors from 3 independent experiments. (B-C) The phosphorylation status of STAT5 and MAPK in extracts of Ba/F3 FLT3-ITD and FLT3-ITD-R4/2 cells treated with 1 and 10 μM SU5614 for 4 hours was determined by Western blot analysis by using the polyclonal anti-pSTAT5 (B) and anti-pMAPK antibodies (C). Expression of STAT5 and MAPK in the same lysates was analyzed by immunoblotting with polyclonal anti-STAT5 and anti-MAPK antibodies.
