Impact of gene dosage, loss of wild-type allele, and FLT3 ligand on Flt3-ITD-induced myeloproliferation.
Kharazi S., Mead AJ., Mansour A., Hultquist A., Böiers C., Luc S., Buza-Vidas N., Ma Z., Ferry H., Atkinson D., Reckzeh K., Masson K., Cammenga J., Rönnstrand L., Arai F., Suda T., Nerlov C., Sitnicka E., Jacobsen SE.
Acquisition of homozygous activating growth factor receptor mutations might accelerate cancer progression through a simple gene-dosage effect. Internal tandem duplications (ITDs) of FLT3 occur in approximately 25% cases of acute myeloid leukemia and induce ligand-independent constitutive signaling. Homozygous FLT3-ITDs confer an adverse prognosis and are frequently detected at relapse. Using a mouse knockin model of Flt3-internal tandem duplication (Flt3-ITD)-induced myeloproliferation, we herein demonstrate that the enhanced myeloid phenotype and expansion of granulocyte-monocyte and primitive Lin(-)Sca1(+)c-Kit(+) progenitors in Flt3-ITD homozygous mice can in part be mediated through the loss of the second wild-type allele. Further, whereas autocrine FLT3 ligand production has been implicated in FLT3-ITD myeloid malignancies and resistance to FLT3 inhibitors, we demonstrate here that the mouse Flt3(ITD/ITD) myeloid phenotype is FLT3 ligand-independent.