Internal tandem duplication of Flt3 modulates chemotaxis and survival of hematopoietic cells by SDF1alpha but negatively regulates marrow homing in vivo.
OBJECTIVE
We have previously shown that Flt3 ligand (FL)/Flt3 signaling regulates hematopoietic cell migration by modulating the SDF1alpha/CXCR4 signaling pathway. Herein, we evaluated whether a functional interaction between SDF1alpha/CXCR4 signaling and internal tandem duplication (ITD) of Flt3 regulates aberrant hematopoietic survival. We also investigated molecular mechanisms responsible for enhanced migration to SDF1alpha as a result of ITD-Flt3 expression and whether ITD-Flt3 regulates hematopoietic cell trafficking.


METHODS
Hematopoietic progenitor cell survival was determined using marrow cells retrovirally expressing ITD-Flt3 and stimulated with SDF1alpha. Migration, to SDF1alpha adhesion to vascular cell adhesion molecule-1, and in vivo homing were determined using Ba/F3 cells expressing ITD-Flt3 and transfected with dominant negative (DN) H-Ras.


RESULTS
Addition of SDF1alpha significantly increased growth factor-independent proliferation of colony-forming unit granulocyte-macrophage induced by ITD-Flt3. Although a negative gradient of SDF1alpha inhibited migration regardless of the stimulation, a positive gradient of FL or ITD-Flt3 significantly increased cell migration even in the presence of a negative SDF1alpha gradient. Enhanced migration induced by ITD-Flt3 was inhibited by DN-H-Ras, whereas overexpression of a constitutive active form of H-Ras in wild-type Flt3-Ba/F3 cells significantly elevated migration to SDF1alpha. Despite enhanced migration to SDF1alpha, preincubation with FL or ITD-Flt3 overexpression significantly reduced homing of primary mouse bone marrow cells or Ba/F3 cells to bone marrow that was associated with significant reduction in adhesion to vascular cell adhesion molecule-1 and VLA4 expression.


CONCLUSIONS
Our results suggest that functional interactions between Flt3 and SDF1alpha/CXCR4 regulate oncogenic proliferation and migration of hematopoietic cells, which is mediated by Ras, and that Flt3 signaling regulates hematopoietic cell trafficking in vivo.
Fukuda
Seiji
S
Department of Microbiology and Immunology and the Walther Oncology Center, Indiana University School of Medicine, and the Walther Cancer Institute, Indianapolis, IN 46202, USA. sfukuda@iupui.edu
Pelus
Louis M
LM
D000818:Animals; D001854:Bone Marrow Cells / Q000502:physiology*; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000502:physiology*; D002633:Chemotaxis; D005260:Female; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D015398:Signal Transduction; D020080:Tandem Repeat Sequences; D019010:Vascular Cell Adhesion Molecule-1 / Q000502:physiology; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics / Q000502:physiology*; D018631:ras Proteins / Q000502:physiology
D054377:Chemokine CXCL12; D019743:Chemokines, CXC; C515256:Cxcl12 protein, mouse; D019010:Vascular Cell Adhesion Molecule-1; C497971:Flt3 protein, mouse; D051941:fms-Like Tyrosine Kinase 3; D018631:ras Proteins