Flt3 tandem duplication mutations cooperate with Wnt signaling in leukemic signal transduction.
Activating Flt3 mutations occur in about 30% of patients with acute myeloid leukemia (AML), often as in-frame internal tandem duplication (ITD) at the juxtamembrane domain of the receptor. These mutations transform hematopoietic cell lines and primary mouse bone marrow. Here, we analyzed the interaction between oncogenic Flt3-ITD mutations and the Wingless-type (Wnt) signaling pathway in the myeloid progenitor cell line 32D. Microarray analyses revealed higher mRNA expression of Frizzled-4, a receptor for Wnt ligands in 32D/Flt3-ITD cells. Findings were verified by quantitative realtime reverse transcription-polymerase chain reaction (RT-PCR) and on the protein level. Compared with 32D/Flt3-WT (wild-type) cells, 32D/Flt3-ITD cells also showed greatly enhanced beta-catenin protein levels, irrespective of their exposure to Wnt3a, a ligand inducing the canonical Wnt signal transduction pathway. In addition, 5 of 7 AML samples with Flt3-ITD mutations expressed high beta-catenin protein levels, whereas patients with wild-type Flt3 did not. Also, Flt3-ITD induced enhanced T-cell factor (TCF)-dependent transcriptional activity and the induction of the Wnt target gene c-myc. In the presence of Flt3-WT or Flt3-ITD signaling, Wnt3a slightly increased 32D cell proliferation. However, transfection experiments with dominant-negative (dn) TCF4 revealed a strong dependence of Flt3-ITD-mediated clonogenic growth on TCF activity. Taken together, our results indicate that Flt3-ITD and Wnt-dependent signaling pathways synergize in myeloid transformation.
Tickenbrock
Lara
L
Department of Medicine, Hematology, and Oncology, University of Münster, Domagkstr. 3, 48149 Münster, Germany.
Schwäble
Joachim
J
Wiedehage
Markus
M
Steffen
Björn
B
Sargin
Bülent
B
Choudhary
Chunaram
C
Brandts
Christian
C
Berdel
Wolfgang E
WE
Müller-Tidow
Carsten
C
Serve
Hubert
H
D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D003598:Cytoskeletal Proteins / Q000032:analysis; D004268:DNA-Binding Proteins; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology*; D007938:Leukemia / Q000209:etiology / Q000235:genetics / Q000473:pathology*; D051379:Mice; D009154:Mutation; D023461:Myeloid Progenitor Cells; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000502:physiology; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics* / Q000502:physiology; D015398:Signal Transduction; D051820:TCF Transcription Factors; D020080:Tandem Repeat Sequences; D015534:Trans-Activators / Q000032:analysis; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin; D051941:fms-Like Tyrosine Kinase 3
C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D036341:Intercellular Signaling Peptides and Proteins; D011518:Proto-Oncogene Proteins; D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; C544895:Tcf7l2 protein, mouse; D015534:Trans-Activators; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin; C497970:FLT3 protein, human; C497971:Flt3 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3