Rapid detection of FLT3 exon 20 tyrosine kinase domain mutations in patients with acute myeloid leukemia by high-resolution melting analysis

Abstract

Th e fms-like tyrosine kinase 3 ( FLT3 ) gene encodes a membrane-bound receptor tyrosine kinase, also known as CD135, which is normally expressed by myeloid and lymphoid progenitors. Activating mutations in this gene can result in constitutive signaling through downstream pathways leading to uncontrolled cellular proliferation and enhanced survival. Acquired FLT3 mutations have been frequently identifi ed in acute myeloid leukemia (AML) samples, particularly among cases with a normal karyotype (NK-AML). Two main types of FLT3 mutations have been described: those aff ecting the cytoplasmic juxtamembrane region, which are commonly internal tandem duplications ( FLT3 ITD), with an incidence of ∼ 25 – 35% in adult AML [1 – 3], and those located in the tyrosine kinase domain ( FLT3 -TKD), with an incidence of ∼ 5 – 10% in adult AML [3 – 5]. FLT3 -TKD mutations specifi cally occur in the activation loop of FLT3 , mostly representing point mutations of D835 or deletions of I836 [3 – 5]. Patients rarely harbor both ITD and TKD mutations [6]. FLT3 -TKD mutants, including D835Y, D835A, D835E, D835H, D835N, D835V, D835del and I836del, have been shown to have constitutive tyrosine kinase activation and factor-independent proliferation when transfected into Ba/F3 cells [7]. Th e prognostic signifi cance of a FLT3 -TKD mutation remains controversial, with the reported impact diff ering between studies [8]. Th is may be due to the low mutation incidence and hence small size of cohorts analyzed, diff erences in the techniques used to screen for mutations between studies and diff erences in downstream eff ectors between FLT3 -ITD and FLT3 -TKD mutations. Although the prognostic signifi cance of FLT3 -TKD mutations has not been fully established, detecting FLT3 -TKD mutations may be of considerable clinical value because of the development of FLT3 tyrosine kinase inhibitors that are currently in clinical trials [9].