Sinusoidal ephrin receptor EPHB4 controls hematopoietic progenitor cell mobilization from bone marrow
Hyeongil Kwak, … , Jason M. Butler, Giovanna Tosato
Hyeongil Kwak, … , Jason M. Butler, Giovanna Tosato
Published November 7, 2016
Citation Information: J Clin Invest. 2016;126(12):4554-4568. https://doi.org/10.1172/JCI87848.
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Research Article Hematology Oncology

Sinusoidal ephrin receptor EPHB4 controls hematopoietic progenitor cell mobilization from bone marrow

Abstract

Hematopoietic stem and progenitor cells (HSPCs) reside in the bone marrow. Stress signals from cancer and other conditions promote HSPC mobilization into circulation and subsequent homing to tissue microenvironments. HSPC infiltration into tissue microenvironments can influence disease progression; notably, in cancer, HSPCs encourage tumor growth. Here we have uncovered a mutually exclusive distribution of EPHB4 receptors in bone marrow sinusoids and ephrin B2 ligands in hematopoietic cells. We determined that signaling interactions between EPHB4 and ephrin B2 control HSPC mobilization from the bone marrow. In mice, blockade of the EPHB4/ephrin B2 signaling pathway reduced mobilization of HSPCs and other myeloid cells to the circulation. EPHB4/ephrin B2 blockade also reduced HSPC infiltration into tumors as well as tumor progression in murine models of melanoma and mammary cancer. These results identify EPHB4/ephrin B2 signaling as critical to HSPC mobilization from bone marrow and provide a potential strategy for reducing cancer progression by targeting the bone marrow.

Authors

Hyeongil Kwak, Ombretta Salvucci, Roberto Weigert, Jorge L. Martinez-Torrecuadrada, Mark Henkemeyer, Michael G. Poulos, Jason M. Butler, Giovanna Tosato

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Figure 1

Bone marrow sinusoidal vessels are EPHB4+ephrin B2–, and hematopoietic cells are ephrin B2+EPHB4–.

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Bone marrow sinusoidal vessels are EPHB4+ephrin B2–, and hematopoietic c...
(A) Cartoon representation: femur with sinusoidal vessels, diaphysis (dp), metaphysis (mp), and central sinus (CS). Red dotted line indicates position of sections in B–D. (B) Immunofluorescence staining: EPHB4+Sca-1– (green) sinusoidal vessels, Sca-1+EPHB4– (magenta) arterioles, and central sinus; right panel shows a magnification of the middle panel. Scale bars: 100 μm. (C) Endomucin+ sinusoidal vessels are EPHB4+Sca-1lo/– (yellow arrows); Sca-1+ arterial vessels are endomucin–EPHB4lo/– (white arrows). Endomucin (Endo, green), EPHB4 (red), and Sca-1 (light blue); DAPI (blue) identifies cell nuclei. Scale bar: 20 μm. (D) OPN+ osteoblasts are endomucinlo/–EPHB4lo/– (white arrows); endomucin+ sinusoidal vessels are EPHB4+OPN– (yellow arrows). OPN (green); endomucin (magenta); EPHB4 (red); DAPI (blue). Scale bar: 50 μm. (E) EPHB4 and CD31 in lysates of the endothelial (MS-1 and BMEC) mouse cell lines, primary sinusoidal endothelial cells (SEC), and primary calvarial osteoblasts (COB); membrane reprobed for β-actin. (F) Distribution of ephrin B2+EPHB4– cells (red) surrounding EPHB4+ephrin B2– sinusoidal vessels (green). Scale bar: 20 μm. (G) Relative ephrin B2–GFP abundance in bone marrow cell populations of Lin–c-Kit+Sca-1+, CD11b+Ly6ChiLy6G–, and CD11b+Ly6CintLy6G+ from an EfnB2H2BGFP reporter mouse by flow cytometry. (H) Intravital time-lapse imaging of calvarium showing the time-dependent attachment of tdTomato-fluorescent (red) cells to the outside wall of sinusoidal vessels, followed by their disappearance. White and yellow arrows point to two fluorescent cells initially on or lateral to sinusoidal vessels that later disappear from view. Sinusoidal vessels: green (FITC-dextran was used to perfuse vessels).