FLT3 and leukemia: Leukemia is an aggressive malignancy frequently associated with activating mutations of receptor tyrosine kinases (RTKs), including BCR/ABL, KIT and FLT3 etc.1–4 Many tyrosine kinase inhibitors (TKIs) against these mutations have entered the clinic, but rapidly acquired resistance to TKIs represents a major hurdle to successful leukemia treatment.