title: Differences in growth promotion, drug response and intracellular protein trafficking of FLT3 mutants.
abstract: OBJECTIVE
  Mutant forms FMS-like tyrosine kinase-3 (FLT3), are reported in 25% of childhood acute lymphoid leukemia (ALL) and 30% of acute myeloid leukemia (AML) patients. In this study, drug response, growth promoting, and protein trafficking of FLT3 wild-type was compared with two active mutants (Internal Tandem Duplication (ITD)) and D835Y.
  
  
  METHODS
  FLT3 was expressed on factor-dependent cells (FDC-P1) using retroviral transduction. The inhibitory effects of CEP701, imatinib, dasatinib, PKC412 and sunitinib were studied on cell proliferation and FLT3 tyrosine phosphorylation. Total expression and proportion of intracellular and surface FLT3 was also determined.
  
  
  RESULTS
  FDC-P1 cells became factor-independent after expression of human FLT3 mutants (ITD and D835Y). FDC-P1 cells expressing FLT3-ITD grow 3 to 4 times faster than those expressing FLT3-D835Y. FD-FLT3-ITD cells were three times more resistant to sunitinib than the FD-FLT3-WT cells. The Geo means for surface FLT3 expression in FD-FLT3-ITD and -D835Y were 65 and 70% less than the FD-FLT3-WT cells. About 40% of expressed FLT3 was detected as intracellular in FD-FLT3-D835Y cell compared to 4 and 4.5% in FD-FLT3-WT and -ITD cells.
  
  
  CONCLUSIONS
  Retention of D835Y FLT3 mutant protein may cause altered signaling, endoplasmic reticulum stress and activation of apoptotic signaling pathways leading to lower proliferation rate in FD-FLT3-D835Y than the FLT3-WT and ITD mutant., these may also also contribute, along with the preferential affinity, to the increased sensitivity of D835Y of CEP701 and PKC412. Studying these genetic variations can help determining the prognosis and designing a therapeutic plan for the patients with FLT3 mutations.
authors.affiliation: Department of Medical Biochemistry, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran ; Discipline of Medical Biochemistry, School of Biomedical Sciences and Pharmacy, University of Newcastle, NSW 2308, Australia.
authors.forename: Baratali
authors.initials: B
authors.lastname: Mashkani
authors.affiliation: School of Medical Sciences/Pharmacology, University of New South Wales, Sydney, NSW 2052, Australia ; School of Environmental and Life Sciences, University of Newcastle, NSW 2308, Australia.
authors.forename: Renate
authors.initials: R
authors.lastname: Griffith
authors.affiliation: Discipline of Medical Biochemistry, School of Biomedical Sciences and Pharmacy, University of Newcastle, NSW 2308, Australia.
authors.forename: Leonie
authors.initials: L
authors.lastname: Ashman
keywords: Activating mutation; Drug response; FLT3; Protein trafficking