title: Up-regulation of homeodomain genes, DLX1 and DLX2, by FLT3 signaling.
abstract: BACKGROUND
  Activating mutations in fms-like tyrosine kinase-3 (FLT3) are frequent in acute myeloid leukemia and represent both a poor prognostic feature and a therapeutic target. We have identified a previously unrecognized downstream effect of FLT3 activation, namely up-regulation of the homeodomain genes, DLX1 and DLX2.
  
  
  METHODS
  MV4;11 cells with FLT3-internal tandem duplication mutation, RS4;11 cells with wild-type FLT3 and blasts from patients with acute myeloid leukemia were used to pursue the relation between FLT3, DLX1/2 and transforming growth factor-β (TGFβ). Real-time quantitative reverse transcriptase polymerase chain reaction, western blot and reverse-phase protein array were performed to detect changes in gene and protein expression. RNA interference and MTS assays were used to study the interaction of PKC412, FLT3 inhibitor and TGFβ1.
  
  
  RESULTS
  A direct relationship between FLT3 activity and DLX1/2 expression was revealed by both inhibition and up-regulation of FLT3 signaling in MV4;11 and RS4;11 cell lines, respectively, in isolated blast cells from patients with acute myeloid leukemia, and in reverse-phase protein array assays of samples from patients with acute myeloid leukemia. Mechanistically, the link between FLT3 and DLX1 expression appears to involve MAPK signaling through the ERK and JNK pathways. To determine whether elevated DLX1 had a functional consequence, we explored the reported inhibition by DLX1 on TGFβ/Smad signaling. Indeed, TGFβ responses were blunted by FLT3 activation in a DLX1-dependent manner and FLT3 inhibition resulted in a time-dependent increase in nuclear phospho-Smad2.
  
  
  CONCLUSIONS
  These findings suggest that alterations in DLX1/2 contribute to the biological consequences of FLT3 activation.
authors.affiliation: Division of Hematology-Oncology, Medical University of South Carolina, Charleston, SC, USA. julia.starkova@lfmotol.cuni.cz
authors.forename: Julia
authors.initials: J
authors.lastname: Starkova
authors.forename: Sharvari
authors.initials: S
authors.lastname: Gadgil
authors.forename: Yi Hua
authors.initials: YH
authors.lastname: Qiu
authors.forename: Nianxiang
authors.initials: N
authors.lastname: Zhang
authors.forename: Ivana
authors.initials: I
authors.lastname: Hermanova
authors.forename: Steven M
authors.initials: SM
authors.lastname: Kornblau
authors.forename: Harry A
authors.initials: HA
authors.lastname: Drabkin
mesh_terms: D000954:Antigens, Surface / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D020868:Gene Silencing; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000503:physiopathology; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D051899:Smad2 Protein / Q000378:metabolism; D019311:Staurosporine / Q000031:analogs & derivatives / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D051941:fms-Like Tyrosine Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000954:Antigens, Surface; C088334:Distal-less homeobox proteins; D018398:Homeodomain Proteins; D047428:Protein Kinase Inhibitors; D051899:Smad2 Protein; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C092261:antigen Dlx-2; D051941:fms-Like Tyrosine Kinase 3; D019311:Staurosporine; C059539:midostaurin