Internal Tandem Duplication Mutations in FLT3 Gene Augment Chemotaxis to Cxcl12 Protein by Blocking the Down-Regulation of the Rho-associated Kinase via the Cxcl12/Cxcr4 Signaling Axis

J Biol Chem. 2014 Nov 7;289(45):31053-65. doi: 10.1074/jbc.M114.568287. Epub 2014 Sep 18.

Abstract

Internal tandem duplication mutations in the Flt3 gene (ITD-FLT3) enhance cell migration toward the chemokine Cxcl12, which is highly expressed in the therapy-protective bone marrow niche, providing a potential mechanism underlying the poor prognosis of ITD-FLT3(+) acute myeloid leukemia. We aimed to investigate the mechanisms linking ITD-FLT3 to increased cell migration toward Cxcl12. Classification of the expression of Cxcl12-regulated genes in ITD-FLT3(+) cells demonstrated that the enhanced migration of ITD-FLT3(+) cells toward Cxcl12 was associated with the differential expression of genes downstream of Cxcl12/Cxcr4, which are functionally distinct from those expressed in ITD-FLT3(-) cells but are independent of the Cxcr4 expression levels. Among these differentially regulated genes, the expression of Rock1 in the ITD-FLT3(+) cells that migrated toward Cxcl12 was significantly higher than in ITD-FLT3(-) cells that migrated toward Cxcl12. In ITD-FLT3(-) cells, Rock1 expression and Mypt1 phosphorylation were transiently up-regulated but were subsequently down-regulated by Cxcl12. In contrast, the presence of ITD-FLT3 blocked the Cxcl12-induced down-regulation of Rock1 and early Mypt1 dephosphorylation. Likewise, the FLT3 ligand counteracted the Cxcl12-induced down-regulation of Rock1 in ITD-FLT3(-) cells, which coincided with enhanced cell migration toward Cxcl12. Rock1 antagonists or Rock1 shRNA abolished the enhanced migration of ITD-FLT3(+) cells toward Cxcl12. Our findings demonstrate that ITD-FLT3 increases cell migration toward Cxcl12 by antagonizing the down-regulation of Rock1 expression. These findings suggest that the aberrant modulation of Rock1 expression and activity induced by ITD-FLT3 may enhance acute myeloid leukemia cell chemotaxis to the therapy-protective bone marrow niche, where Cxcl12 is abundantly expressed.

Keywords: CXCL12; CXCR4; Cell Biology; Gene Regulation; Hematopoiesis; ITD-Flt3; Leukemia; Rho-associated Kinase; Signal Transduction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Movement
  • Cell Proliferation
  • Chemokine CXCL12 / genetics*
  • Chemotaxis
  • Down-Regulation
  • Gene Expression Regulation
  • Hematopoiesis
  • Humans
  • Leukemia, Myeloid, Acute / metabolism
  • Mice
  • Mutation*
  • Phenotype
  • Phosphorylation
  • Receptors, CXCR4 / metabolism*
  • Signal Transduction
  • fms-Like Tyrosine Kinase 3 / genetics*
  • rho-Associated Kinases / metabolism*

Substances

  • CXCL12 protein, human
  • CXCR4 protein, human
  • Chemokine CXCL12
  • Receptors, CXCR4
  • FLT3 protein, human
  • fms-Like Tyrosine Kinase 3
  • ROCK1 protein, human
  • rho-Associated Kinases