Development and pharmacological characterization of a stable HEK293 cell model for the study of human FLT3 signaling and its pharmacological modulation

Transient transfection in adherent cell lines has been used to study the function and pharmacology of the receptor tyrosine kinase FLT3, which is involved in myeloid leukemia and pain. However, transiently transfected cells express high levels of receptors, which show ligand-independent constitutive activity. We generated a stable recombinant cell line by transfecting a plasmid construct containing the full-length Flt3 cDNA into HEK293 cells. Four individual clones, numbered 6, 10, 15 and 17 were obtained. The FLT3 receptors expressed in the four clones showed high affinity for the ligand FL, as assessed in saturation and competition binding experiments, and FLT3 activation by FL effectively initiated the recruitment of the MAPK signaling pathway, a key mediator of downstream signaling cascades for the FLT3 receptor. Clone 6 showed highest receptor activation (nearly 6-fold increase upon FL stimulation), which was selected for further pharmacological characterization. FL-induced phospho-ERK levels were inhibited by quizartinib or BDT001 with potencies like those previously reported, and showed successful phosphorylation of the FLT3 receptor assessed by TYR969. The clone N°6 of FLT3-transfected cell line therefore appears as a suitable and versatile cell line for assessing the potency of FLT3-based therapeutic candidates.