KIT and acute myeloid leukemia: To exclude that blocking of CD117 signaling and survival factor withdrawal, as observed with AMG191, is responsible for CD117×CD3 BTCE-mediated cytotoxicity, we performed in vitro killing assays with human Kasumi-1 cell line (CD117Asn(822)-Lys) and AML-patient-derived xenograft (PDX)-CD117ASP(816)-VAL cells, which both carry an activating CD117 mutation.