Analysis of Flt3 phosphorylation. Western blot analyses for phosphorylated and total Flt3 of patient no. 13 (Flt3-ITD) (panel A) and patient no. 8 (Flt3-D835) (panel B). Negative control represents whole blood lysate from a healthy donor, and positive control represents whole blood lysate from a healthy donor spiked with an Flt3-expressing cell line. C indicates cycle; D, the day of the cycle when blood was drawn; and pY591, flt3 phosphorylated at tyrosine 591.