Inhibition of CD26 peptidase activity significantly improves engraftment of retrovirally transduced hematopoietic progenitors

IntroductionWHIM syndrome is characterized by warts, hypogammaglobulinemia, recurrent bacterial infection, and myelokathexis (severe chronic neutropenia with marrow hyperplasia and inappropriate apoptosis of mature myeloid cells in the bone marrow [BM]). [1][2][3][4][5] Many but not all cases of WHIM syndrome have been linked to autosomal dominant mutations in CXC chemokine receptor 4 (CXCR4), all of which cause truncations of the carboxy-terminus of CXCR4. Specific mutations identified in some families with myelokathexis include R334X, S339fs342X, E343X, and G335 X. 2,6,7 CXCR4 and its ligand, stromal cell-derived factor-1 (SDF-1; also known as CXCL12), play a central role in BM homing and trafficking of hematopoietic progenitor cells, mobilization of lymphocytes, and release of developing neutrophils from bone marrow. 1,[8][9][10] Mice lacking CXCR4 demonstrate defective hematopoiesis and cerebellar and cardiovascular development and die perinatally, highlighting the importance of CXCR4 in these organ systems. 11 There is 1 report of a cardiac malformation in a patient who may have had WHIM syndrome. 12 In vitro studies of WHIM variants of CXCR4 (mutated CXCR4) have provided evidence for increased agonist-dependent signaling by the mutant receptor, suggesting that the clinical manifestations may be due to hyperfunction of these receptors in vivo. In particular, we previously reported that transduction of the R334X WHIM variant into healthy human CD34 ϩ peripheral blood mobilized stem cells (PBSCs) results in enhanced chemotactic and calcium flux responses of the cells to SDF-1, and found that this effect was associated with and presumably caused by a failure of the mutant receptor to downregulate and internalize, leading to prolongation of activation. 13 In the current study we explore the mechanism of myelokathexis in WHIM syndrome using the NOD.CB17-Prkdc scid /J mouse (nonobese diabetic/severe combined immunodeficiency [NOD/SCID] mouse) xenotransplantation model engrafted with healthy human mobilized CD34 ϩ PBSCs that had been transduced with internal ribosome entry site (IRES)-containing bifunctional retrovirus vectors encoding mutated CXCR4 or wild-type (wt) CXCR4 together with a green fluorescent protein (GFP) construct or with vector-encoding GFP construct only. We will demonstrate that expression of mutated CXCR4 does not itself induce apoptosis in transduced myeloid cells differentiated in culture from the transduced PBSCs, but does result in a WHIM-type myelokathexis pattern of the transduced human cells in the in vivo xenotransplantation model (myeloid apoptosis in marrow and decreased release of cells from the marrow to the circulation). An Inside Blood analysis of this article appears at the front of this issue.The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked ''advertisement'' in accordance with 18 USC section 1734. Materials and methods G-CSF-mobilized CD34 ؉ PBSCsFollowing informed cons...

Section: Discussionmentioning

confidence: 99%

WHIM syndrome myelokathexis reproduced in the NOD/SCID mouse xenotransplant model engrafted with healthy human stem cells transduced with C-terminus–truncated CXCR4

Kawai

Choi

Cardwell

et al. 2006

“…Taking into consideration effects of DPP4 inhibition on enhanced homing and engraftment of mouse HSC 5,6,[26][27][28] and engraftment of human CD34…”

Section: Effects Of Dpp4 On Hscs and Hpcsmentioning

confidence: 99%

Implications of DPP4 modification of proteins that regulate stem/progenitor and more mature cell types

O’Leary

Broxmeyer

2013

120

122

Dipeptidylpeptidase (DPP) 4 has the potential to truncate proteins with a penultimate alanine, proline, or other selective amino acids at the N-terminus. DPP4 truncation of certain chemokines, colony-stimulating factors, and interleukins have recently been linked to regulation of hematopoietic stem/progenitor cells, more mature blood cells, and other cell types. We believe that the potential role of DPP4 in modification of many regulatory proteins, and their subsequent effects on numerous stem/progenitor and other cell-type functions has not been adequately appreciated. This review addresses the potential implications of the modifying effects of DPP4 on a large number of cytokines and other growth-regulating factors with either proven or putative DPP4 truncation sites on hematopoietic cells, and subsequent effects of DPP4-truncated proteins on multiple aspects of steady-state and stressed hematopoiesis, including stem/progenitor cell, and more mature cell, function.

“…[15][16][17] During a screen of stromal feeders from fetal sites of hematopoiesis, used to mimic the hematopoietic niche, we found that transcripts for Tfpi were .20-fold higher in murine stromal cells that supported long-term repopulating (LTR) HSCs in noncontact cultures. 18 Tissue-factor (TF) pathway inhibitor (TFPI) mediates the coagulation cascade.…”

mentioning

confidence: 99%

Glypican-3–mediated inhibition of CD26 by TFPI: a novel mechanism in hematopoietic stem cell homing and maintenance

Khurana

Margamuljana

Joseph

et al. 2013

Key Points• TFPI inhibits CD26 activity in murine and human HSPCs via GPC3 resulting in better transwell migration as well as BM homing. • GPC32/2 mice show increased CD26 activity that leads to poor HSC retention in BM and increased circulating HSPCs.Directional migration determines hematopoietic stem/progenitor cell (HSPC) homing, which depends upon the interaction between the chemokine CXCL12 and its receptor CXCR4. CD26 is a widely expressed membrane-bound ectopeptidase that cleaves CXCL12 thereby depleting its chemokine activity. We identified tissue-factor pathway inhibitor (TFPI) as a biological inhibitor of CD26 in murine and human HSPCs. We observed low-level TFPI expression in endothelial cells in the bone marrow (BM), which did not increase following radiation injury. Treatment of HSPCs with TFPI in vitro led to enhanced HSPC migration toward CXCL12, as well as homing and engraftment in the BM upon transplantation. We found that Glypican-3 (GPC3), a heparan sulfate proteoglycan expressed on murine as well as human HSPCs, mediated this effect. TFPI did not affect CD26 activity, migration, or homing of GPC3 2/2 HSPCs, while it affected GPC1 2/2 HSPCs similar to wild-type HSPCs. Moreover, proliferation of GPC3 2/2 but not GPC1 2/2 BM HSPCs was significantly increased, which was associated with a decrease in the primitive HSC pool in BM and an increase in proportion of the circulating HSPCs in the peripheral blood. Hence, we present a novel role for TFPI and GPC3 in regulating HSC homing as well as retention in the