Plasma stromal cell-derived factor-1 during granulocyte colony-stimulating factor-induced peripheral blood stem cell mobilization

Breast tumor metastasis following filgrastim administration due to the SDF-1/CXCR4 pathway

Filgrastim, a recombinant type of granulocyte-colony stimulating factor (G-CSF), has a high potential to manage chemotherapy-induced leukopenia. It can increase stromal cell-derived factor 1 (SDF-1) which may stimulate C-X-C chemokine receptor type 4 (CXCR4) to migrate bone marrow-derived stem/progenitor cells to the bloodstream. Here, we aimed to investigate in vitro and in vivo effects of filgrastim on cell migration, invasion, and metastasis. A lentivirus vector of the anti-CXCR4 receptor was first used for the CXCR4 knockout. Effects of filgrastim on cell proliferation and migration were then investigated on 4T1 cells by Transwell migration and wound healing assay. At last, the effects of filgrastim on cell metastasis and the possible involved mechanisms have been investigated in a metastatic murine breast tumor. The knockout of the CXCR4 receptor could lead to a decrease in cell proliferation, migration, and invasion of the 4T1 cells. Filgrastim could directly target SDF-1 and upregulate the expression of the CXCR4 receptor. The knockout of the CXCR4 receptor reduced cell metastasis in an animal model of breast cancer. CXCR4 receptor stimulation by the filgrastim-affected pathways is a conserved evolutionary response that could increase cancer cell proliferation and consequent cell metastasis. Our results suggest that the activation of the CXCR4 receptor is a conserved evolutionary response that can increase cell proliferation, migration, and consequent metastasis. It seems that filgrastim may increase the chance of cancer cell metastasis in people continuously receiving it to increase the number of neutrophils. Filgrastim induces the SDF-1/CXCR4 axis on tumor cell growth. SDF-1 and its receptor CXCR4 are vital targets for filgrastim. The CXCR4 can stimulate the PI3K/AKT, NF-κB, and JAK/STAT signaling pathways. The SDF-1/CXCR4 pathway promotes cell chemotaxis and proliferation via MAPKs signaling. It also enhances cell survival, proliferation, and angiogenesis, increasing tumor cell metastasis. The STAT3-mediated inflammation is essential for tumorigenesis processes, and Akt, Wnt, STAT3, and CXCR4 signaling pathways are all correlated. CXCR4 = C-X-C chemokine receptor type 4, SDF-1 = stromal-derived-factor-1, MAPK = mitogen activated protein kinase; NF-κB = nuclear factor-κB, PI3K = phosphoinositide 3-kinase, JAK = Janus kinase, STAT = signal transducer and activator of transcription, PLC = phospholipase C, PKC = Protein kinase C, GRK = G protein-coupled receptor kinase.

Hematopoietic Stem and Progenitor Cells (HSPCs)

Hematopoietic stem/progenitor cells (HSPCs) isolated from bone marrow have been successfully employed for 50 years in hematological transplantations. Currently, these cells are more frequently isolated from mobilized peripheral blood or umbilical cord blood. In this chapter, we overview several topics related to these cells including their phenotype, methods for isolation, and in vitro and in vivo assays to evaluate their proliferative potential. The successful clinical application of HSPCs is widely understood to have helped establish the rationale for the development of stem cell therapies and regenerative medicine.

The Biological and Clinical Relevance of G Protein-Coupled Receptors to the Outcomes of Hematopoietic Stem Cell Transplantation: A Systematized Review

Hematopoietic stem cell transplantation (HSCT) remains the only curative treatment for several malignant and non-malignant diseases at the cost of serious treatment-related toxicities (TRTs). Recent research on extending the benefits of HSCT to more patients and indications has focused on limiting TRTs and improving immunological effects following proper mobilization and engraftment. Increasing numbers of studies report associations between HSCT outcomes and the expression or the manipulation of G protein-coupled receptors (GPCRs). This large family of cell surface receptors is involved in various human diseases. With ever-better knowledge of their crystal structures and signaling dynamics, GPCRs are already the targets for one third of the current therapeutic arsenal. The present paper assesses the current status of animal and human research on GPCRs in the context of selected HSCT outcomes via a systematized survey and analysis of the literature.

A novel view of the adult bone marrow stem cell hierarchy and stem cell trafficking

This review presents a novel view and working hypothesis about the hierarchy within the adult bone marrow stem cell compartment and the still-intriguing question of whether adult bone marrow contains primitive stem cells from early embryonic development, such as cells derived from the epiblast, migrating primordial germ cells or yolk sac-derived hemangioblasts. It also presents a novel view of the mechanisms that govern stem cell mobilization and homing, with special emphasis on the role of the complement cascade as a trigger for egress of hematopoietic stem cells from bone marrow into blood as well as the emerging role of novel homing factors and priming mechanisms that support stromal-derived factor 1-mediated homing of hematopoietic stem/progenitor cells after transplantation.

The role of sphingosine-1 phosphate and ceramide-1 phosphate in trafficking of normal stem cells and cancer cells

INTRODUCTION

A common feature of many types of cells is their responsiveness to chemotactic gradients of factors for which they express the corresponding receptors. The most studied chemoattractants so far are peptide-based growth factors and a family of cytokines endowed with strong chemotactic properties, called chemokines. However, additional evidence has accumulated that, in addition to these peptide-based chemoattractants, an important role in cell migration is played by bioactive lipids.

AREAS COVERED

Solid evidence has accumulated that two bioactive phosphorylated sphingolipids that are derivatives of sphingolipid metabolism, namely sphingosine-1-phosphate (S1P) and ceramide-1-phosphate (C1P), are potent chemoattractants for a variety of cells. In this review, we will discuss the effect of these two phosphorylated sphingolipids on the trafficking of normal and malignant cells, and, in particular, we will focus on their role in trafficking of normal hematopoietic stem/progenitor cells. Unlike other mediators, S1P under steady-state conditions maintain a steep gradient between interstitial fluid and peripheral blood and lymph across the endothelial barrier, which is important in the egress of cells from bone marrow. Both S1P and C1P may be upregulated in damaged tissues, which may result in reversal of this gradient.

EXPERT OPINION

S1P and C1P are important regulators of the trafficking of normal and malignant cells, and modification of their biological effects will have important applications in optimizing stem cell mobilization and homing, tissue organ/regeneration, and preventing cancer metastasis.

An emerging link in stem cell mobilization between activation of the complement cascade and the chemotactic gradient of sphingosine-1-phosphate

Under steady-state conditions, hematopoietic stem/progenitor cells (HSPCs) egress from bone marrow (BM) and enter peripheral blood (PB) where they circulate at low levels. Their number in PB, however, increases significantly in several stress situations related to infection, organ/tissue damage, or strenuous exercise. Pharmacologically mediated enforced egress of HSPCs from the BM microenvironment into PB is called "mobilization", and this phenomenon has been exploited in hematological transplantology as a means to obtain HSPCs for hematopoietic reconstitution. In this review we will present the accumulated evidence that innate immunity, including the complement cascade and the granulocyte/monocyte lineage, and the PB plasma level of the bioactive lipid sphingosine-1-phosphate (S1P) together orchestrate this evolutionarily conserved mechanism that directs trafficking of HSPCs.

The role of innate immunity in trafficking of hematopoietic stem cells-an emerging link between activation of complement cascade and chemotactic gradients of bioactive sphingolipids

Hematopoietic stem and progenitor cells (HSPCs) circulate under steady-state conditions at detectable levels in peripheral blood (PB). The phenomenon of enforced release of HSPCs from BM into PB is called mobilization and may be envisioned as a danger-sensing response mechanism triggered by hypoxia or mechanical- or infection-induced tissue damage and is a part of stress response. It is unquestionable that the a-chemokine stromal derived factor-1 (SDF-1)-CXCR4 axis plays crucial role in retention of HSPCs in BM. However, all factors that direct mobilization of HSPCs into PB and homing back to the BM or their allocation to damaged organs are not characterized very well. In this chapter we will present mounting evidence that elements of innate immunity such as complement cascade (CC) cleavage fragments (e.g., C3a and C5a), granulocytes, generation of membrane attack complex (MAC) together with sphingosine-1 phosphate (S1P) orchestrate HSPC mobilization. On other hand some other bioactive lipids e.g., ceramide-1-phosphate (C1P) that is released from damaged/"leaky" cells in BM after myeloablative conditioning for transplant may play an opposite important role in homing of HSPCs to BM. Finally, the chemotactic activity of all chemoattractants for HSPCs including SDF-1, S1P and C1P is enhanced in presence of CC cleavage fragments (e.g., C3a) and MAC that is a final product of CC activation.

Anticoagulation in large-volume leukapheresis: comparison between citrate- versus heparin-based anticoagulation on safety and CD34 (+) cell collection efficiency

BACKGROUND AIMS

Little is known of the effect of anticoagulation on peripheral blood progenitor cell (PBPC) harvest during large-volume leukapheresis (LVL). Because of the interaction of heparin with stromal cell-derived factor (SDF)-1α, it has been proposed that a heparin-based anticoagulation may result in an increased PBPC collection efficiency compared with standard citrate-based anticoagulation.

METHODS

We conducted a prospective randomized trial to address the effect of both anticoagulation regimes on safety, subjective comfort and CD34 (+) collection efficiency in 90 adult patients undergoing standardized LVL. Anticoagulation consisted of either citrate (group C) or a combination of heparin and low-dose citrate (group H).

RESULTS

The overall incidence of adverse reactions (AR) during LVL was 17%. AR consisted only of citrate-related AR; no bleeding complications were observed. Determination of parameters of the acid-base balance revealed a higher frequency of metabolic alkalosis in group C. Analysis of serum SDF-1α revealed no differences in SDF-1α plasma levels. There were no differences in the CD34 (+) cell collection efficiency, resulting in the harvest of equal CD34 (+) cell yields independent of the anticoagulation used.

CONCLUSIONS

Our data show no clinical relevant effect of a heparin containing anticoagulation in terms of an increased overall CD34 (+) cell collection during LVL, although this regime shows some benefits in terms of the incidence and subjective tolerance towards AR. Based on our results the decision between a citrate- and heparin-substituted anticoagulation for LVL should be driven by patient-related factors, and should concern potential contraindications of both methods.

Innate immunity as orchestrator of stem cell mobilization

Hematopoietic stem and progenitor cells (HSPCs), as well as other types of stem cells, circulate under steady-state conditions at detectable levels in peripheral blood (PB), with their numbers increasing in response to stress, inflammation and tissue/organ injury. This mobilization process may be envisioned as a danger-sensing response mechanism triggered by hypoxia or mechanical or infection-induced tissue damage that recruits into PB different types of stem cells that have a role in immune surveillance and organ/tissue regeneration. Mobilization is also significantly enhanced by the administration of pharmacological agents, which has been exploited in hematological transplantology as a means to obtain HSPCs for hematopoietic reconstitution. In this review we will present mounting evidence that innate immunity orchestrates this evolutionarily conserved mechanism of HSPC mobilization.

Novel insight into stem cell mobilization-plasma sphingosine-1-phosphate is a major chemoattractant that directs the egress of hematopoietic stem progenitor cells from the bone marrow and its level in peripheral blood increases during mobilization due to activation of complement cascade/membrane attack complex

Complement cascade (CC) becomes activated and its cleavage fragments play a crucial role in the mobilization of hematopoietic stem/progenitor cells (HSPCs). Here, we sought to determine which major chemottractant present in peripheral blood (PB) is responsible for the egress of HSPCs from the BM. We noticed that normal and mobilized plasma strongly chemoattracts HSPCs in a stromal derived factor-1 (SDF-1)-independent manner because i) plasma SDF-1 level does not correlate with mobilization efficiency, ii) the chemotactic plasma gradient is not affected in the presence of AMD3100, and iii) it is resistant to denaturation by heat. Surprisingly, the observed loss of plasma chemotactic activity after charcoal stripping suggested involvement of bioactive lipids and we focused on sphingosine-1 phosphate (S1P), a known chemoattracant of HSPCs. We found that S1P i) creates in plasma a continuously present gradient for BM-residing HSPCs, ii) is at physiologically relevant concentrations a chemoattractant several magnitudes stronger than SDF-1, and iii) its plasma level increases during mobilization due to CC activation and the interaction of membrane attack complex (MAC) with erythrocytes that are a major reservoir of S1P. We conclude and propose a new paradigm that S1P is a crucial chemoattractant for BM-residing HSPCs and that CC via MAC induces release of S1P from erythrocytes for optimal egress/mobilization of HSPCs.

Novel insight into stem cell mobilization-plasma sphingosine-1-phosphate is a major chemoattractant that directs the egress of hematopoietic stem progenitor cells from the bone marrow and its level in peripheral blood increases during mobilization due to activation of complement cascade/membrane attack complex

We reported that complement cascade (CC) becomes activated in bone marrow (BM) during mobilization of hematopoietic stem/progenitor cells (HSPCs) induced by granulocyte-colony stimulating factor (G-CSF) and C5 cleavage plays an important role in optimal egress of HSPCs. In the current work, we explored whether CC is involved in mobilization of HSPCs induced by the CXCR4 antagonist, AMD3100. To address this question, we performed mobilization studies in mice that display a defect in the activation of the proximal steps of CC (Rag^−/−, SCID, C2.Cfb^−/−) as well as in mice that do not activate the distal steps of CC (C5^−/−). We noticed that proximal CC activation-deficient mice (above C5 level), in contrast to distal step CC activation-deficient C5^−/− ones mobilize normally in response to AMD3100 administration. We hypothesized that this discrepancy in mobilization could be explained by AMD3100 activating C5 in Rag^−/−, SCID, C2.Cfb^−/− animals in a non-canonical mechanism involving activated granulocytes. To support this granulocytes i) as first egress from BM and ii) secrete several proteases that cleave/activate C5 in response to AMD3100. We conclude that AMD3100-directed mobilization of HSPCs, similarly to G-CSF-induced mobilization, depends on activation of CC; however, in contrast to G-CSF, AMD3100 activates the distal steps of CC directly at the C5 level. Overall, these data support that C5 cleavage fragments and distal steps of CC activation are required for optimal mobilization of HSPCs.

Peripheral blood circulating immature cell counts predict CD34+ cell yields in G-CSF-induced PBPC mobilization in healthy donors

BACKGROUND

It has been previously reported that the number of circulating immature cells (CIC) in peripheral blood (PB) estimates the number of CD34+ cells collected in G-CSF plus chemotherapy-induced PBPC mobilization. The correlation of CIC counts in PB with CD34+ cell yield and its usefulness was evaluated in G-CSF-induced PBPC mobilization for healthy donors.

STUDY DESIGN AND METHODS

CIC counts in PB and CD34+ cell counts in the apheresis product from 122 collections were assessed, and the relationship between these two variables was evaluated with the Pearson rank correlation analysis, the chi-squared test, and the U-test.

RESULTS

CIC counts were correlated weakly with the number of CD34+ cells per L of blood processed in the apheresis product (Pearson rank correlation analysis; r=0.357, p<0.0001). When a level of 1.7 x 10(9) CICs per L was selected as a cutoff value, the sensitivity and specificity for collecting more than 20 x 10(6) CD34+ cells per L of blood processed were 63.6 and 77.5 percent, respectively.

CONCLUSION

The present study suggests that the number of CICs in PB may estimate the number of CD34+ cells collected. The data indicate that CIC counts above 1.7 x 10(9) per L can be used as a good predictor for PBPC collections containing more than 20 x 10(6) CD34+ cells per L of blood processed in a single apheresis procedure.

Current mechanistic scenarios in hematopoietic stem/progenitor cell mobilization

Uncovering the molecular mechanisms governing the exit of stem/progenitor cells from bone marrow to peripheral blood at steady state or after their enforced migration has been an ongoing challenge. Recently, however, several new avenues or paradigms in mobilization have emerged from ever-expanding work in humans subjected to granulocyte colony-stimulating factor (G-CSF) mobilization, as well as from studies in normal and gene-deficient mouse models. Although these developments represent notable advances that met with considerable excitement, they have been quenched by surprising vacillations in subsequent research. This perspective highlights recent developments in mobilization along with their controversies. A full understanding of the directional cues that control the migratory behavior and the fate of stem/progenitor cells once they migrate out of bone marrow will await further experimentation, aiming to bridge our current gaps in knowledge.