Hck, theprimary focus of this report, is expressed primarily inmyeloid hematopoietic cells where it normally contributes to signaltransduction associated with innate immune responses by neutrophilsand macrophages.8,9 Because of this expression pattern,Hck dysregulation is closely associated with both chronic and acuteforms of myeloid leukemia (CML and AML). Here, HCK is linked to acute myeloid leukemia.