The chemokine receptor CXCR4 enhances integrin-mediated in vitro adhesion and facilitates engraftment of leukemic precursor-B cells in the bone marrow.
OBJECTIVE
It has been demonstrated that acute lymphoblastic leukemia (ALL) blasts migrate into layers of bone marrow fibroblasts (BMF) in vitro using the beta1 integrins VLA-4 and VLA-5, and that the chemokine SDF-1 and its receptor CXCR4 influences ALL migration. We investigated whether this effect was due to SDF-1-mediated induction of adhesion through beta1 integrins.


METHODS
Adhesion of pre-B ALL cells or the cell line NALM6 to extracellular matrix proteins was examined using short-term in vitro binding assays. The effects of exposure of cells to SDF-1, antibodies to CXCR4, and the G protein inhibitor pertussis toxin (PTX) were assessed. The consequences of down regulation of CXCR4 on the in vivo behavior of pre-B ALL cells after injection into sublethally irradiated NOD/SCID mice was studied.


RESULTS
Treatment with SDF-1 of NALM6 cells or cells from cases of precursor-B ALL resulted in a doubling of adhesion to fibronectin, laminin, and VCAM-1, but had no effect on binding to collagens I or IV. Antibodies to CXCR4 and PTX inhibited SDF-1-induced adhesion on these substrates. NALM6 cells with CXCR4 expression downregulated by SDF-1 exposure demonstrated a reduced capacity to engraft into the bone marrow of NOD/SCID mice, with only 22 +/- 11% of marrow cells being of human origin in mice receiving SDF-1-treated cells compared to 48 +/- 5% in mice receiving untreated cells (p < 0.001). The homing of SDF-1-treated cells to the bone marrow after 24 hours was also reduced by 72 +/- 16% compared to control cells.


CONCLUSIONS
These data show that SDF-1 and CXCR4 are involved in regulation of beta1 integrin function, and are important for the localization of pre-B cells to the bone marrow in vivo.
Shen
W
W
Westmead Institute for Cancer Research, Westmead Millennium Institute, Westmead, Australia.
Bendall
L J
LJ
Gottlieb
D J
DJ
Bradstock
K F
KF
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001402:B-Lymphocytes / Q000473:pathology*; D001854:Bone Marrow Cells / Q000473:pathology*; D002051:Burkitt Lymphoma / Q000473:pathology; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology*; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000494:pharmacology* / Q000502:physiology; D015536:Down-Regulation / Q000187:drug effects*; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D037342:Pertussis Toxin; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000473:pathology; D011485:Protein Binding; D019718:Receptors, CXCR4 / Q000187:drug effects / Q000502:physiology*; D014183:Transplantation, Heterologous / Q000276:immunology; D014407:Tumor Cells, Cultured; D019010:Vascular Cell Adhesion Molecule-1 / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000906:Antibodies; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; C515256:Cxcl12 protein, mouse; D016326:Extracellular Matrix Proteins; D019718:Receptors, CXCR4; D019010:Vascular Cell Adhesion Molecule-1; D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin