ABSTRACT
Many patients with hematological neoplasms fail to mobilize sufficient numbers of hematopoietic stem cells (HSCs) in response to granulocyte colony-stimulating factor (G-CSF) precluding subsequent autologous HSC transplantation. Plerixafor, a specific antagonist of the chemokine receptor CXCR4, can rescue some but not all patients who failed to mobilize with G-CSF alone. These refractory poor mobilizers cannot currently benefit from autologous transplantation. To discover alternative targetable pathways to enhance HSC mobilization, we studied the role of hypoxia-inducible factor-1α (HIF-1α) and the effect of HIF-1α pharmacological stabilization on HSC mobilization in mice. We demonstrate in mice with HSC-specific conditional deletion of the Hif1a gene that the oxygen-labile transcription factor HIF-1α is essential for HSC mobilization in response to G-CSF and Plerixafor. Conversely, pharmacological stabilization of HIF-1α with the 4-prolyl hydroxylase inhibitor FG-4497 synergizes with G-CSF and Plerixafor increasing mobilization of reconstituting HSCs 20-fold compared with G-CSF plus Plerixafor, currently the most potent mobilizing combination used in the clinic.
Subject(s)
Hematopoietic Stem Cell Mobilization , Hematopoietic Stem Cell Transplantation , Hematopoietic Stem Cells/cytology , Hypoxia-Inducible Factor 1, alpha Subunit/physiology , Prolyl Hydroxylases/physiology , Animals , Anti-HIV Agents/pharmacology , Benzylamines , Blotting, Western , Cell Movement/drug effects , Cell Proliferation/drug effects , Cells, Cultured , Cyclams , Flow Cytometry , Granulocyte Colony-Stimulating Factor/pharmacology , Hematopoietic Stem Cells/metabolism , Heterocyclic Compounds/pharmacology , Humans , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Prolyl-Hydroxylase Inhibitors/pharmacology , RNA, Messenger/genetics , Real-Time Polymerase Chain Reaction , Receptors, CXCR4/antagonists & inhibitors , Reverse Transcriptase Polymerase Chain Reaction , Transplantation, AutologousABSTRACT
The CXCR4 antagonist AMD3100 is progressively replacing cyclophosphamide (CYP) as adjuvant to granulocyte colony-stimulating factor (G-CSF) to mobilize hematopoietic stem cells (HSC) for autologous transplants in patients who failed prior mobilization with G-CSF alone. It has recently emerged that G-CSF mediates HSC mobilization and inhibits bone formation via specific bone marrow (BM) macrophages. We compared the effect of these three mobilizing agents on BM macrophages, bone formation, osteoblasts, HSC niches and HSC reconstitution potential. Both G-CSF and CYP suppressed niche-supportive macrophages and osteoblasts, and inhibited expression of endosteal cytokines resulting in major impairment of HSC reconstitution potential remaining in the mobilized BM. In sharp contrast, although AMD3100 was effective at mobilizing HSC, it did not suppress osteoblasts, endosteal cytokine expression or reconstitution potential of HSC remaining in the mobilized BM. In conclusion, although G-CSF, CYP and AMD3100 efficiently mobilize HSC into the blood, their effects on HSC niches and bone formation are distinct with both G-CSF and CYP targeting HSC niche function and bone formation, whereas AMD3100 directly targets HSC without altering niche function or bone formation.
