Polymerization of murine macrophage inflammatory protein 1 alpha inactivates its myelosuppressive effects in vitro: the active form is a monomer

Aberrant regulation of hematopoiesis by T cells in BAZF-deficient mice

The BAZF (BCL-6b) protein is highly similar to the BCL-6 transcriptional repressor. While BCL-6 has been characterized extensively, relatively little is known about the normal function of BAZF. In order to understand the physiological role of BAZF, we created BAZF-deficient mice. Unlike BCL-6-deficient mice, BAZF-deficient mice are healthy and normal in size. However, BAZF-deficient mice have a hematopoietic progenitor phenotype that is almost identical to that of BCL-6-deficient mice. Compared to wild-type mice, both BAZF-deficient and BCL-6-deficient mice have greatly reduced numbers of cycling hematopoietic progenitor cells (HPC) in the BM and greatly increased numbers of cycling HPC in the spleen. In contrast to HPC from wild-type mice, HPC from BAZF-deficient and BCL-6-deficient mice are resistant to chemokine-induced myelosuppression and do not show a synergistic growth response to granulocyte-macrophage colony-stimulating factor plus stem cell factor. Depletion of CD8 T cells in BAZF-deficient mice reverses several of the hematopoietic defects in these mice. Since both BAZF- and BCL-6-deficient mice have defects in CD8 T-cell differentiation, we hypothesize that both BCL-6 and BAZF regulate HPC homeostasis by an indirect pathway involving CD8 T cells.

Class II transactivator-mediated regulation of major histocompatibility complex class II antigen expression is important for hematopoietic progenitor cell suppression by chemokines and iron-binding proteins

OBJECTIVE

Iron-binding proteins H-ferritin (HF) and lactoferrin (LF), as well as chemokines, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma suppress hematopoietic progenitor cell (HPC) proliferation. Major histocompatibility complex (MHC) class II antigens have been associated with suppressive effects of HF and LF. Because the transcription factor class II transactivator (CIITA) regulates expression of MHC class II antigens, we evaluated influences of CIITA and MHC class II antigens on suppression of colony formation by murine bone marrow HPC in response to HF, LF, CC, and CXC chemokines, TNF-alpha, and IFN-gamma. We also evaluated hematopoiesis in mice deficient in both CIITA and MHC class II antigens (CIITA -/-), in mice deficient in MHC class II antigens but not in CIITA (MHC class II -/-), and in mice deficient in CIITA but not in MHC class II antigens (CIITA-IE).

MATERIALS AND METHODS

HF, LF, CCL3/MIP-1alpha, CXCL5/ENA-78, CXCL8/IL-8, CCL5/RANTES, TNF-alpha, and IFN-gamma were assessed for effects on colony formation by bone marrow HPC (colony-forming unit granulocyte-macrophage, burst-forming unit erythroid, and colony-forming unit multipotential) stimulated in vitro by combinations of growth factors including erythropoietin, stem cell factor, pokeweed mitogen mouse spleen cell conditioned medium, and hemin. Bone marrow cells were from CIITA -/-, MHC class II antigen -/-, CIITA-IE, and littermate control mice. We also evaluated cycling status (percent cells in S-phase) and absolute numbers of marrow and spleen HPC in these mice.

RESULTS

Multiple growth factor-stimulated colony formation by control bone marrow HPC was significantly suppressed by HF, LF, CCL3, CXCL5, CXCL8, TNF-alpha, and IFN-gamma, but not by CCL5. However, HPC from CIITA -/- and MHC class II antigen -/- mouse marrow was insensitive to inhibition by HF, LF, CCL3, CXCL5, CXCL8, and CCL5; these HPC were inhibited by TNF-alpha and IFN-gamma. Restoration of MHC class II expression in CIITA -/- (CIITA-IE) mice restored responsiveness of HPC to inhibition by HF, LF, CCL3, CXCL5, and CXCL8. Increased cycling of splenic HPC in CIITA -/- and MHC class II antigen -/-, compared to control and CIITA-IE, mice was noted.

CONCLUSIONS

Myelosuppressive effects of iron-binding proteins HF and LF and chemokines CCL3, CXCL5, and CXCL8 on mouse bone marrow HPC require expression of MHC class II antigens, and CIITA is involved in this responsiveness through its regulation of expression of MHC class II antigens.

Induction of MIP-1α in Kupffer cell by portal venous transfusion

INTRODUCTION

Previous studies have shown that portal venous transfusion (PVT) induces a state of immunosuppression, and Kupffer cells may be involved in the mechanism.

OBJECTIVE

This study was aimed to investigate the effect of PVT on Kupffer cell gene expression.

MATERIALS AND METHODS

Each BALB/C mouse was subjected to laparotomy and received one of five treatments: PVT, portal venous saline injection (PVS), inferior vena caval transfusion (IVCT), inferior vena caval saline injection (IVCS) or sham operation (S). The blood for PVT and IVCT was sampled from C57BL/6J mice. Kupffer cells were then isolated 1 or 24 h after each of the 5 treatments, for a total of 10 experimental groups (1-h PVT, PVS, IVCT, IVCS and S, and 24-h PVT, PVS, IVCT, IVCS and S) from BALB/C mice. To examine the effect of PVT on Kupffer cell gene expression, RT-PCR differential display was performed.

RESULTS

Increase in the expression of MIP-1alpha mRNA post PVT and IVCT was identified by differential display. PVT groups revealed higher levels of serum MIP-1alpha than any other groups.

CONCLUSION

These results suggest that MIP-1alpha may be involved in a cascade of signaling events associated with the PVT-mediated immunologic modulation in Kupffer cells.

Distinct requirements for Stat4 and Stat6 in hematopoietic progenitor cell responses to growth factors and chemokines

Hematopoietic progenitor cell (HPC) homeostasis is critical in maintaining innate immunity and healing processes. Recently, we demonstrated that Th1 cells regulate HPC homeostasis, partly based on altered homeostasis in Stat4- and Stat6-deficient mice. To explore changes in HPC responsiveness in altered T helper cell environments, we directly examined growth factor-stimulated colony formation and chemokine-induced myelosuppression of HPC in Stat4- and Stat6-deficient bone marrow cells. Stat6-deficient cells have increased responses to the synergy between granulocyte-macrophage colony-stimulating factor (GM-CSF) and steel factor (SLF), compared to wild-type and Stat4-deficient cells. Increased responses are eliminated by in vivo depletion of CD4 cells. Whereas Stat6-deficient bone marrow cells respond to chemokine-mediated myelosuppression, Stat4-deficient bone marrow cells are refractory to the suppressive effects of chemokines. Thus, T helper cell development affects HPC homeostasis through several mechanisms, including the sensitivity to growth factor stimulation and chemokine suppression of HPC colony formation. Since Stat4 and Stat6 regulate opposing programs of T helper differentiation, there are distinct requirements for Stat4 and Stat6 in regulation of growth factor and chemokine responses of HPC.

Regulation of hematopoiesis by chemokine family members

Chemokines, originally designated as chemoattractant cytokines, comprise a large family of molecules that have been implicated in a number of different functions mediated through chemokine receptors. Among these functions are regulatory roles in hematopoiesis that encompass effects on the proliferation, survival, and homing/migration of myeloid progenitor cells. This article reviews the field of chemokine regulation of hematopoiesis at the level of myeloid progenitor cells.

Synthesis and biological evaluation of analogues of the tetrapeptide N-Acetyl-Ser-Asp-Lys-Pro (AcSDKP), an inhibitor of primitive haematopoietic cell proliferation

The tetrapeptide N-Acetyl-Ser-Asp-Lys-Pro (AcSDKP), an inhibitor of haematopoietic stem cell proliferation, reduces in vivo and in vitro the damage to the stem cell compartment resulting from treatment with chemotherapeutic agents or ionizing radiations. In order to provide new molecules likely to improve the myeloprotection displayed by this tetrapeptide, we have prepared a set of analogues of AcSDKP. These compounds are derived from the parent peptide by substitution or modification of the N- or of the C-terminus, or substitution of side chains. We report here that almost all investigated analogues retain the antiproliferative activity reducing in vitro the proportion of murine Colony-Forming Units Granulocyte, Macrophage (CFU-GM) in S-phase and inhibiting the entry into cycle of High Proliferative Potential Colony-Forming Cells (HPP-CFC). This shows that the polar groups of Ser, Asp or Lys are critical for the expression of biological activity, but that the modification of the N- or C-terminus mostly yielded compounds still retaining antiproliferative activity and devoid of toxicity. The efficacy of AcSDKP analogues in preventing in vitro the primitive haematopoietic cells from entering into cycle makes these molecules new candidates for further in vivo investigations.

Changing the chemokine gradient: CINC1 crosses the blood-brain barrier

Chemokines are a large family of small, inducible, secreted, chemoattractant cytokines that are involved in inflammatory processes. It is well known that systemic and CNS infections cause disruption of the blood-brain barrier (BBB); however, it is not clear how chemokines are involved in this process. We studied the pharmacokinetics of the passage of the chemokine cytokine-induced neutrophil chemoattractant-1 (CINC1) from blood to brain after i.v. bolus injection and its efflux out of the brain after i.c.v. injection. Radiolabeled CINC1 was injected i.v. into mice, and the results were determined by multiple-time regression analysis. Using HPLC, we detected intact CINC1 in brain homogenate and blood after i.v. administration. CINC1 accumulated in the cerebral vasculature but also crossed the BBB completely and rapidly. No saturation of the influx was found, suggesting that either CINC1 crossed the BBB by simple diffusion or the dynamic interactions of binding and internalization precluded the self-inhibition typical of a transport system. Furthermore, there was no efflux system, with CINC1 exiting the brain at the same rate as reabsorption of CSF. The CINC1 injected into blood or CSF did not cause any breakdown of the BBB during the course of the experiments. Thus, the influx of CINC1 may alter the "chemokine gradient" across the BBB and therefore affect inflammatory reactions involving the CNS.

Biological significance of the expression of HIV-related chemokine coreceptors (CCR5 and CXCR4) and their ligands by human hematopoietic cell lines

The aim of this study was to learn more about the role of the HIV-related chemokine-chemokine receptor axes in human hematopoiesis. To address this issue we phenotyped 35 selected hematopoietic cell lines for the expression of CD4, CXCR4 and CCR5. We next evaluated the functionality of these chemokine receptors by calcium flux and chemotaxis assays, and by the ability of SDF-1, MIP-1alpha, MIP-1beta and RANTES to influence the growth of the cells expressing CXCR4 and/or CCR5. Lastly, we examined whether human hematopoietic cell lines may secrete some HIV-related chemokines, and whether endogenously secreted chemokines might interfere with the infectability. of hematopoietic cells by X4 and R5 HIV strains. These results demonstrate that: (1) HIV-related receptors are widely expressed on human hematopoietic cell lines; (2) stimulation of CXCR4 by SDF-1 induces calcium flux and chemotaxis in several hematopoietic cell lines more efficiently than stimulation of CCR5 by receptor-specific beta-chemokines; (3) chemokines do not regulate proliferation of the hematopoietic cells; and finally (4) infectability of the hematopoietic cells by HIV-1 may be auto-modulated by endogenously secreted chemokines. These data shed more light on the role of HIV-related chemokine-chemokine receptors axes in human hematopoiesis and interaction of hematopoietic cells with HIV.

The role of HIV-related chemokine receptors and chemokines in human erythropoiesis in vitro

In order to better define the role of HIV-related chemokines in human erythropoiesis we studied: A) the expression of chemokine receptors, both on human CD34(+) cells which include erythroid progenitors and on more mature erythroid cells; B) the functionality of these receptors by calcium flux, chemotaxis assay and phosphorylation of mitogen-activated protein kinases (MAPK) p42/44 (ERK1/ERK2) and AKT, and finally C) the influence of chemokines on BFU-E formation. We found that HIV-related chemokine receptor CXCR4, but not CCR5, is detectable on human CD34(+) BFU-E cells. CXCR4 surface expression decreased during erythroid maturation, although CXCR4 mRNA was still present in cells isolated from differentiated erythroid colonies. SDF-1, a CXCR4 ligand, induced calcium flux and phosphorylation of MAPK (p42/44) and AKT in CD34(+)KIT(+) bone marrow mononuclear cells which contain BFU-E, as well as chemotactic activity of both human CD34(+) BFU-E progenitors and erythroid cells isolated from day 2-6 BFU-E colonies. Responsiveness to SDF-1 decreased when the cells differentiated to the point of surface expression of the erythroid-specific marker Glycophorin-A. In contrast, the CCR5 ligands (macrophage inflammatory protein-1alpha [MIP-1alpha], MIP-1beta, and RANTES) did not activate calcium flux, MAPK and AKT phosphorylation or chemotaxis of CD34(+)KIT(+) cells or cells isolated from the BFU-E colonies. Interestingly, none of the chemokines tested in this study had any effect on BFU-E colony formation. In conclusion, only CXCR4 is functional, and its specific ligand SDF-1 may therefore play an important role in the homing and/or retention of early erythroid precursors in the bone marrow environment.

Liver-infiltrating T lymphocytes are attracted selectively by IFN-inducible protein-10

We have demonstrated that interferon-inducible protein-10 (IP-10) is produced in hepatocytes surrounded by infiltrative mononuclear cells in chronic hepatitis. To clarify the role of IP-10 in hepatitis, we examined the chemoattractive activity of IP-10 on liver-infiltrating lymphocytes in experimental animal models of hepatitis. IP-10 was specifically induced in the livers of mice treated intravenously (i.v.) with Con A, while monocyte chemotactic protein-1 (MCP-1) showed a much lower level of induction and neither RANTES nor macrophage inflammatory protein-1alpha (MIP-1alpha) was detected. The liver-infiltrating lymphocytes in Con A-induced hepatitis were attracted only by IP-10, and not by other chemokines such as RANTES, MCP-1 and MIP-1alpha. The chemoattractive effect of IP-10 was dose-dependent and was neutralized by monoclonal antibodies to IP-10. The specific effect of IP-10 on liver-infiltrating lymphocytes was also seen on those obtained from rat livers with fulminant hepatitis induced by sequential treatment with killed Propionibacterium acnes (P. acnes) and LPS. Peripheral blood lymphocytes were slightly attracted by IP-10 as well as RANTES and MIP-1alpha, while hepatic resident lymphocytes were not. On the other hand, thioglycolate-elicited peritoneal macrophages did not respond to IP-10, although they did show a response to RANTES, MCP-1 and MIP-1alpha. These results indicated that IP-10 is a specific chemoattractant for T lymphocytes in the inflammatory liver tissues and may play a specific role in the development of hepatitis.

Bone marrow CD34(+) cells and megakaryoblasts secrete beta-chemokines that block infection of hematopoietic cells by M-tropic R5 HIV

CD34(+) cells are nonpermissive to infection by HIV strains X4 and R5, despite the fact that many CD34(+) cells express high levels of the viral receptor protein CD4 and the coreceptor CXCR4 on their surface. In these cells, the co-receptor CCR5 protein, which, like CXCR4, is a chemokine receptor, is detected mainly intracellularly. We hypothesized that CD34(+) cells secrete CCR5-binding chemokines and that these factors interfere with HIV R5 interactions with these cells, possibly by binding CCR5 or by inducing its internalization. We found that human CD34(+) cells and CD34(+)KIT(+) cells, which are enriched in myeloid progenitor cells, expressed and secreted the CCR5 ligands RANTES, MIP-1alpha, and MIP-1beta and that IFN-gamma stimulated expression of these chemokines. In contrast, SDF-1, a CXCR4 ligand, was not detectable in the CD34(+)KIT(+) cells, even by RT-PCR. Conditioned media from CD34(+) cell culture significantly protected the T lymphocyte cell line PB-1 from infection by R5 but not X4 strains of HIV. Interestingly, the secretion of endogenous chemokines decreased with the maturation of CD34(+) cells, although ex vivo, expanded megakaryoblasts still secreted a significant amount of RANTES. Synthesis of CCR5-binding chemokines by human CD34(+) cells and megakaryoblasts therefore largely determines the susceptibility of these cells to infection by R5 HIV strains. We postulate that therapeutic agents that induce the endogenous synthesis of chemokines in human hematopoietic cells may protect these cells from HIV infection.

Altered responsiveness to chemokines due to targeted disruption of SHIP

SHIP has been implicated in negative signaling in a number of hematopoietic cell types and is postulated to downregulate phosphatidylinositol-3-kinase- (PI-3K-) initiated events in diverse receptor signaling pathways. Because PI-3K is implicated in chemokine signaling, we investigated whether SHIP plays any role in cellular responses to chemokines. We found that a number of immature and mature hematopoietic cells from SHIP-deficient mice manifested enhanced directional migration (chemotaxis) in response to the chemokines stromal cell-derived factor-1 (SDF-1) and B-lymphocyte chemoattractant (BLC). SHIP(-/-) cells were also more active in calcium influx and actin polymerization in response to SDF-1. However, colony formation by SHIP-deficient hematopoietic progenitor cell (HPCs) was not inhibited by 13 myelosuppressive chemokines that normally inhibit proliferation of HPCs. These altered biologic activities of chemokines on SHIP-deficient cells are not caused by simple modulation of chemokine receptor expression in SHIP-deficient mice, implicating SHIP in the modulation of chemokine-induced signaling and downstream effects.

Regulation of hematopoiesis in a sea of chemokine family members with a plethora of redundant activities

The field of chemokine biology is a rapidly advancing one, with over 50 chemokines identified that mediate their effects through one or more of 16 different chemokine receptors. Chemokines, originally identified as chemotactic cytokines, manifest a number of functions, including modulation of blood cell production at the level of hematopoietic stem/progenitor cells and the directed movement of these early blood cells. This report reviews chemokines and chemokine/receptor activities mainly in the context of hematopoietic cell regulation and the numerous chemokines that manifest suppressive activity on proliferation of stem/progenitor cells. This is contrasted with the specificity of only a few chemokines for the chemotaxis of these early cells. The large number of chemokines with suppressive activity is hypothesized to reflect the different cell, tissue, and organ sites of production of these chemokines and the need to control stem/progenitor cell proliferation in different organ sites throughout the body.

Identification of amino acid residues critical for aggregation of human CC chemokines macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and RANTES. Characterization of active disaggregated chemokine variants

Human CC chemokines macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and RANTES (regulated on activation normal T cell expressed) self-associate to form high-molecular mass aggregates. To explore the biological significance of chemokine aggregation, nonaggregating variants were sought. The phenotypes of 105 hMIP-1alpha variants generated by systematic mutagenesis and expression in yeast were determined. hMIP-1alpha residues Asp26 and Glu66 were critical to the self-association process. Substitution at either residue resulted in the formation of essentially homogenous tetramers at 0.5 mg/ml. Substitution of identical or analogous residues in homologous positions in both hMIP-1beta and RANTES demonstrated that they were also critical to aggregation. Our analysis suggests that a single charged residue at either position 26 or 66 is insufficient to support extensive aggregation and that two charged residues must be present. Solution of the three-dimensional NMR structure of hMIP-1alpha has enabled comparison of these residues in hMIP-1beta and RANTES. Aggregated and disaggregated forms of hMIP-1alpha, hMIP-1beta, and RANTES generally have equivalent G-protein-coupled receptor-mediated biological potencies. We have therefore generated novel reagents to evaluate the role of hMIP-1alpha, hMIP-1beta, and RANTES aggregation in vitro and in vivo. The disaggregated chemokines retained their human immunodeficiency virus (HIV) inhibitory activities. Surprisingly, high concentrations of RANTES, but not disaggregated RANTES variants, enhanced infection of cells by both M- and T-tropic HIV isolates/strains. This observation has important implications for potential therapeutic uses of chemokines implying that disaggregated forms may be necessary for safe clinical investigation.

Effects of CC, CXC, C, and CX3C chemokines on proliferation of myeloid progenitor cells, and insights into SDF-1-induced chemotaxis of progenitors

Chemokines have been implicated in the regulation of stem/progenitor cell proliferation and movement. The purpose of the present study was to assess a number of new chemokines for suppressive activity and to delve further into SDF-1-mediated chemotaxis of progenitor cells. This report extends the list of chemokines that have suppressive activity against immature subsets of myeloid progenitors stimulated to proliferate by multiple growth factors to include: MCP-4/CK beta-10, MIP-4/CK beta-7, I-309, TECK, GCP-2, MIG and lymphotactin. The suppressive activity of a number of other chemokines was confirmed. Additionally, pretreatment of the active chemokines with an acetylnitrile solution enhanced specific activity of a number of these chemokines. The new chemokines found to be lacking suppressive activity include: MCP-2, MCP-3, eotaxin-1, MCIF/HCC-1/CK beta-1, TARC, MDC, MPIF-2/eotaxin-2/CK beta-6, SDF-1 and fractalkine/neurotactin. Overall, 19 chemokines, crossing the CC, CXC, and C subgroups, have now been found to be myelosuppressive, and 14 chemokines crossing the CC, CXC and CX3C subgroups have been found to lack myelosuppressive activity under the culture conditions of our assays. Because of the redundancy in chemokine/chemokine receptor interactions, it is not yet clear through which chemokine receptors many of these chemokines signal to elicit suppressive activities. It was also found that SDF-1-induced chemotaxis of progenitors can occur in the presence of fibronectin (FN) and extracellular matrix components and that FN effects involve activation of beta 1-, and possibly alpha 4-, integrins.

Protective effects of BB-10010 treatment on chemotherapy-induced neutropenia in mice

Chemotherapy-induced neutropenia is a major dose-limiting factor in the management of cancer patients. Most chemotherapeutic agents are active against proliferating cells, interfering with DNA replication and/or mitosis. A number of chemokines, notably macrophage inflammatory protein-1 alpha [MIP-1alpha], have been reported to induce cell-cycle arrest in immature hematopoietic progenitors, raising the possibility that chemokines, such as MIP-1alpha, could be used to reduce or even eliminate the hematologic toxicity of cycle-active chemotherapy. We tested the effectiveness of BB-10010 [a genetically engineered analog of human MIP-1alpha] in vivo against three different cytotoxic drugs [cyclophosphamide (Cy), 5-fluorouracil (5-FU) and cytosine arabinoside (Ara-C)] commonly used in cancer therapy. BB-10010 treatment reduced the toxicity of all three agents, though the precise mode of protection varied with the cytotoxic drug used. BB-10010 reduced the neutropenic interval in Cy-treated mice without affecting the neutropenic nadir, whereas the absolute neutrophil counts [ANC] of both 5-FU and Ara-C treated mice were significantly higher throughout the neutropenic interval for mice receiving BB-10010 prior to chemotherapy. These findings indicate that the ability to manipulate the cell cycle of hematopoietic progenitors with chemokines, such as BB-10010/MIP-1alpha and other negative regulators, may be exploited to reduce chemotherapy-induced neutropenia; furthermore, the fact that BB-10010 is effective against several different cytotoxic agents is cause for guarded optimism that this approach may be generally applicable, and, once optimized for patient use, may prove to be of significant clinical benefit.

The growth inhibitory role and potential clinical value of macrophage inflammatory protein 1 alpha in myeloid leukaemias

The control of primitive haemopoietic progenitor cell proliferation in vitro can be achieved with combinations of growth stimulatory cytokines. Acting in apparent opposition to these growth stimulators are growth inhibitory substances, including prostaglandins, cytokines and chemokines which bind to specific cognate cell surface receptors and promote signal transduction events that interfere with cellular proliferation. Within the bone marrow microenvironment, significant quantities of both growth inhibitors and growth promoters can be detected. The ratio of their concentrations within microenvironmental niches of the marrow may regulate primitive blood cell production. The potential exists, therefore, for the disregulation of haemopoiesis via the disruption of the balance between positive and negative regulators of haemopoietic progenitor proliferation. In one particular disease, chronic myeloid leukaemia (CML), there is a lack of response of leukaemic cells to the chemokine growth inhibitor, Macrophage Inflammatory Protein-1alpha (MIP-1alpha). The role of MIP-1alpha in regulation of haemopoiesis, the response of CML progenitor cells and other myeloid leukaemic cells to this chemokine, and the reasons for lack of response to MIP-1alpha in leukaemic cells are reviewed.

Myeloid progenitor cell proliferation and mobilization effects of BB10010, a genetically engineered variant of human macrophage inflammatory protein-1alpha, in a phase I clinical trial in patients with relapsed/refractory breast cancer

Macrophage Inflammatory Protein (MIP)-1alpha is myelosuppressive in vitro and in vivo for hematopoietic stem and immature subsets of myeloid progenitor cells, demonstrates some myeloprotective effects in mice treated with Ara-C and hydroxyurea, and has stem/progenitor cell mobilizing activity in mice. Based on these observations, BB10010, a genetic variant of MIP-1alpha, was assessed for effects on marrow and blood myeloid progenitor cells in patients with relapsed/refractory breast cancer. MIP-1alpha readily polymerizes, whereas BB10010 has a reduced tendency to form large polymers at physiological pH and ionic strength and retains biological activity. Patients were injected with 5, 10, 30 or 100 microg/kg BB10010 s.c. daily for 3 days. BB10010 significantly reduced the cycling status of marrow myeloid progenitors from pretreatment levels of 39-58% to 0 - 11% one day after the third and last injection of BB10010. This was associated with significant decreases in frequency of marrow progenitors (number of colonies formed per number of cells plated) and percent biopsied marrow CD34+ cells. The suppressive effects were reversible in patients and the rapidity of this reversal demonstrated in mouse studies. BB10010 had no effect on nucleated cellularity or on the proliferation of nucleated cells as assessed in marrow biopsies from the patients. These latter effects may in part reflect the noted decreased apoptosis of nucleated cells by BB10010. BB10010 also demonstrated significant but modest myeloid progenitor cell mobilizing capacity. Blood progenitors were in a slow or non-cycling state prior to treatment and this did not change after administration of BB10010. The above effects of BB10010 were similar at the four different dosage levels assessed. These results demonstrate in humans the suppressive and mobilizing effects of MIP-1alpha and BB10010 previously noted in vivo in mice.

Genetic subtype-independent inhibition of human immunodeficiency virus type 1 replication by CC and CXC chemokines

We have studied the breadth and potency of the inhibitory actions of the CC chemokines macrophage inhibitory protein 1alpha (MIP-1alpha), MIP-1beta, and RANTES against macrophage-tropic (M-tropic) primary isolates of human immunodeficiency virus type 1 (HIV-1) and of the CXC chemokine stromal cell-derived factor 1alpha against T-cell-tropic (T-tropic) isolates, using mitogen-stimulated primary CD4+ T cells as targets. There was considerable interisolate variation in the sensitivity of HIV-1 to chemokine inhibition, which was especially pronounced for the CC chemokines and M-tropic strains. However, this variation was not obviously dependent on the genetic subtype (A through F) of the virus isolates. Peripheral blood mononuclear cell donor-dependent variation in chemokine inhibition potency was also observed. Among the CC chemokines, the rank order for potency (from most to least potent) was RANTES, MIP-1beta, MIP-1alpha. Some M-tropic isolates, unexpectedly, were much more sensitive to RANTES than to MIP-1beta, whereas other isolates showed sensitivities comparable to those of these two chemokines. Down-regulation of the CCR5 and CXCR4 receptors occurred in cells treated with the cognate chemokines and probably contributes to anti-HIV-1 activity. Thus, for CCR5, the rank order for down-regulation was also RANTES, MIP-1beta, MIP-1alpha.

Biology and mechanisms of action of synergistically stimulated myeloid progenitor cell proliferation and suppression by chemokines

A number of cytokines can act together to stimulate/enhance the proliferation of hematopoietic stem and progenitor cells in a greater than additive fashion. An example of this is the combination of a colony-stimulating factor with a potent costimulating molecule such as steel factor. Certain members of the chemokine family of cytokines can suppress this synergistically enhanced proliferation. This review focuses on cytokines involved in these stimulating/enhancing/suppressing effects with regard to biological activity and what is beginning to be learned about the intracellular signal transduction events that may be mediating these effects. Examples of intracellular mediators involved include, but are not limited to, the Raf-1/ MAP kinase pathway and cyclin-dependent kinase inhibitors p21cip-1 and p27kip-1 for cell proliferation, and eukaryotic initiation factor-4E and 4E binding protein 1 for protein synthesis.

Comparison of the effects of AcSDKP, thymosin beta4, macrophage inflammatory protein 1alpha and transforming growth factor beta on human leukemic cells

We have compared the effects of AcSDKP, Thymosin beta4 (Tbeta4), MIP1alpha and TGFbeta on acute myeloid leukemia (AML) and B-lineage acute lymphoid leukemia (B-ALL) cells using liquid cultures in the presence of GM-CSF, IL-3 and SCF for AML cells and IL-3 and IL-7 for ALL cells. Each molecule was added daily and cell proliferation was evaluated on day 3 by thymidine incorporation. Whereas TGFbeta was found inhibitory in all the AML and B-ALL cases studied, MIP1alpha was inhibitory in 6/12 AML cases and had no effect on B-ALL cells. AcSDKP and Tbeta4 showed an inhibitory effect in a few cases but only at high doses which were inactive on normal cells. Thus, our study not only confirms the effect of TGFbeta, MIP1alpha and AcSDKP on AML cells but also provides new data concerning their effect on B-ALL and the possible inhibitory effect of AcSDKP at high doses. Furthermore, we show for the first time the effect of Tbeta4 on leukemic cells. Altogether, our data indicate differences of sensitivity of leukemic cells to negative regulators, some leukemias being inhibited by one or several of these molecules whereas others were unresponsive to all used. The clinical relevance of these observations still remains to be determined.

Human chemokines: an update

Interleukin 8, the first chemokine to be characterized, was discovered nearly ten years ago. Today, more than 30 human chemokines are known. They are often upregulated in inflammation and act mainly on leukocytes inducing migration and release responses. The present review deals largely with the new developments of the last three years. Several structural studies have shown that most chemokines form dimers. The dimers, however, dissociate upon dilution, and the monomers constitute the biologically active form. Chemokine activities are mediated by seven-transmembrane-domain, G protein coupled receptors, five of which were discovered in the past three years. The primary receptor-binding domain of all chemokines is near the NH2 terminus, and antagonists can be obtained by truncation or substitutions in this region. Major progress has been made in the understanding of chemokine actions on T lymphocytes that respond to several CC chemokines but also to IP10 and Mig, two CXC chemokines that selectively attract T cells via a novel receptor. Effects of chemokines on angiogenesis and tumor growth have been reported, but the data are still contradictory and the mechanisms unknown. Of considerable interest is the recent discovery that some chemokines function as HIV-suppressive factors by interacting with chemokine receptors which, together with CD4, were recognized as the binding sites for HIV-1.

Leukocyte migration and activation by murine chemokines

Chemokines are a family of chemotactic cytokines which attract different types of leukocytes. This property, combined with some additional inflammatory and growth-regulatory activities, demonstrate their crucial role in the immune system. Chemokines are low molecular weight proteins and possess a typical positioning of four conserved cysteines. This family is further subdivided in two subfamilies depending on whether the first two cysteines are adjacent or not (CC and CXC chemokines, respectively). The CXC chemokines (including interleukin-8) predominantly attract neutrophils, whereas CC chemokines induce migration of monocytes, as well as other leukocyte cell types. In this article, the general characteristics of chemokines are reviewed. Furthermore, the murine CC chemokines, JE/MCP-1, MCP-3/MARC, MIP-1 alpha, MIP-1 beta, RANTES, TCA3, C10/MRP-1, MRP-2, and eotaxin, are discussed more in detail.

Feedback inhibitors in normal and tumor tissues

Negative feedback represents the principal mechanism for regulating growth in biological systems. Over the past 20 years, our understanding of the role played by inhibitory factors governing this process has advanced considerably. This is particularly well illustrated in the field of experimental hematology with the recognition of hemopoietic progenitor cell proliferation inhibitors, an expanding group of unrelated peptides that act to limit proliferation in hemopoietic precursor cells. The characterization and subsequent production of these molecules by chemical synthesis or recombinant DNA technology has enabled investigators to explore their role in normal hemopoiesis and define a potential role in clinical medicine. A number of inhibitory factors, including macrophage inflammatory protein-1 alpha (MIP-1 alpha) and the tetrapeptide AcSDKP appear to share a relative specificity to hemopoietic progenitor cell subsets. Others, such as interferon and tumor necrosis factor, have a more complex action and their hemopoietic effects are likely to be indirect and nonspecific. In addition to the role of inhibitors in normal steady state, it has become increasingly evident that loss of sensitivity to the normal feedback inhibitory signals may be of central importance in carcinogenesis and tumor promotion. This presumably represents a developmental strategy that allows the neoplastic cell to maintain a growth advantage over its normal cell counterpart. The underlying mechanisms that terminate in inhibitor-resistance are yet to be elucidated, but in some instances they may be associated with aberrant tumor suppressor gene function.

Human chemokines: enhancement of specific activity and effects in vitro on normal and leukemic progenitors and a factor-dependent cell line and in vivo in mice

The myelosuppressive effects of human chemokines were evaluated in vitro on normal myeloid progenitors obtained from bone marrow and cord blood, on bone marrow progenitors from patients with acute or chronic leukemia, on proliferation of human factor-dependent cell line M07e, and in vivo on myelopoiesis in mice. Preincubation of human MIP-1 alpha, MIP-2 alpha, interleukin (IL)-8, platelet factor (PF) 4, monocyte chemotactic and activating factor (MCAF), and interferon-inducible protein-10 (IP-10) in an acetonitrile (ACN) solution significantly enhanced the specific activity of these chemokines for in vitro suppression of granulocyte-macrophage (CFU-GM), erythroid (BFU-E), and multipotential (CFU-GEMM) progenitor cells stimulated to proliferate with a colony stimulating factor plus steel factor (SLF). Combinations of any two of these ACN-treated chemokines synergized to suppress colony formation of CFU-GM, BFU-E, and CFU-GEMM at chemokine concentrations below that at which combinations of non-ACN treated chemokines are active. Cord blood progenitors, as previously reported, were in a slow or noncycling state and nonresponsive to inhibition by chemokines. However, after suspension culture with GM-CSF, IL-3, and SLF, they were placed into rapid cell cycle and were responsive to inhibition by ACN-treated chemokines. Low doses of these ACN-pretreated chemokines were active in vivo in suppressing absolute numbers and cycling status of femoral marrow CFU-GM, BFU-E, and CFU-GEMM in C3H/HeJ mice. Other chemokines, alone and in combination, including MIP-1 beta, MIP-2 beta, GRO-alpha NAP-2, and RANTES, were inactive in vitro and in vivo whether or not they were pretreated with ACN. While heterogeneity in responsiveness of CFU-GM from different patients with leukemia to suppression by ACN-treated chemokines was apparent, if the patients had CFU-GM responsive to one of the active chemokines these cells were responsive to the other active chemokines; if patient CFU-GM were not responsive to one of the chemokines, they were not responsive to the other active chemokines. M07e colony-forming cells were responsive to the growth-inhibiting effects of the active ACN-treated chemokines, alone and in combination, but these effects were rapidly reversible and sustained only by multiple daily additions of chemokines. These results should be of value in considering these chemokines for potential clinical use and for assessment of their mechanisms of action, alone and in combination.

The IP-10 chemokine binds to a specific cell surface heparan sulfate site shared with platelet factor 4 and inhibits endothelial cell proliferation

IP-10 is a member of the chemokine family of cytokines and is induced in a variety of cells in response to interferon gamma and lipopolysaccharide. The self-aggregation common to many chemokines, including IP-10, has hindered the identification of a specific IP-10 receptor. Using an IP-10 alkaline phosphatase fusion protein that fortuitously blocks this self-aggregation, we have identified an IP-10 binding site on a variety of cells including endothelial, epithelial, and hematopoietic cells. This binding site has a Kd of 25 nM, is inhibited by recombinant murine or human IP-10, and is dependent on the presence of cell surface heparan sulfate proteoglycans (HSPG). This conclusion is based on the findings that IP-10 binding to cells is: (a) inhibited by heparin and heparan sulfate; (b) sensitive to a 1 M NaCl wash; (c) eliminated by treatment with heparinase and trypsin; and (d) absent on mutant CHO cells that do not express cell surface HSPG. Platelet factor 4 (PF4), but not IL-8, monocyte chemoattractant protein-1, RANTES, monocyte inflammatory protein (MIP)-1 alpha, or MIP-1 beta, can compete effectively with IP-10 for binding to the cell surface. Furthermore, IP-10 shares with PF4 the ability to inhibit endothelial cell proliferation (IC50 = 150 nM). These studies demonstrate specificity in the interaction of chemokines and HSPG, and they define IP-10 and PF4 as a distinct subset of chemokines sharing an HSPG-binding site and angiostatic properties.

Inhibition of endothelial cell proliferation by platelet factor-4 involves a unique action on S phase progression

Modulation of endothelial cell proliferation and cell cycle progression by the "chemokine" platelet factor-4 (PF-4) was investigated. PF-4 inhibited DNA synthesis, as well as proliferation of endothelial cells derived from large and small blood vessels. Inhibition by PF-4 was independent of the type and the concentration of stimuli used for the induction of endothelial cell proliferation. Inhibition of cell growth by PF-4 was reversible. The effects of PF-4 were antagonized by heparin. Cell cycle analysis using [3H]thymidine pulse labeling during traverse of synchronous cells from G0/G1 to S phase revealed that addition of PF-4 during G1 phase completely abolished the entry of cells into S phase. In addition, PF-4 also inhibited DNA synthesis in cells that were already in S phase. In exponentially growing cells, addition of PF-4 resulted in an accumulation of > 70% of the cells in early S phase, as determined by FACS (Becton-Dickinson Immunocytometry Systems, Mountain View, CA). In cells synchronized in S phase by hydroxyurea and then released, addition of PF-4 promptly blocked further progression of DNA synthesis. These results demonstrate that in G0/G1-arrested cells, PF-4 inhibited entry of endothelial cells into S phase. More strikingly, our studies have revealed a unique mode of endothelial cell growth inhibition whereby PF-4 effectively blocked cell cycle progression during S phase.

Macrophage inflammatory protein 1 alpha, interleukin 3 and diffusible marrow stromal factors maintain human hematopoietic stem cells for at least eight weeks in vitro

Factors that induce proliferation of the human hematopoietic stem cell are ill-defined. Primitive hematopoietic progenitors can be maintained and differentiate in stroma-dependent, long-term bone marrow cultures (LTBMC), originally described by Dexter et al. (Dexter, T. M., L. H. Coutinho, E. Spooncer, C. M. Heyworth, C. P. Daniel, R. Schiro, J. Chang, and T. D. Allen. 1990. Molecular Control of Haemopoiesis). However, 70-80% of primitive progenitors capable of reinitiating secondary stromal cultures (LTBMC-initiating cells [IC]) are lost over a period of 5 wk in such cultures. We have recently described a novel "stroma-noncontact" culture system, in which hematopoietic progenitors are separated from the stromal layer by a 0.4-micron microporous filter membrane. Primitive progenitors in such cultures can not only differentiate into committed progenitors, but are also maintained to a greater extent than in "Dexter" cultures. However, still only 50% of the originally seeded LTBMC-IC are recovered at week 5. Since maintenance of primitive progenitors may depend not only on growth-promoting factors but also on factors that inhibit differentiation and/or proliferation, we evaluated the effect of macrophage inflammatory protein 1 alpha (MIP-1 alpha) or "stem cell inhibitor" in combination with the growth-inducing factor interleukin 3 (IL-3) on the recovery of LTBMC-IC from stroma-noncontact cultures. We demonstrate that addition of MIP-1 alpha alone to stroma-noncontact cultures does not change the number of LTBMC-IC present after 8 wk, indicating that this factor may not directly inhibit or stimulate proliferation of primitive progenitors. Addition of the growth stimulatory cytokine, IL-3, alone results in exhaustion of LTBMC-IC after 8 wk of culture, possibly as a result of their terminal differentiation. However, LTBMC-IC can be maintained for at least 8 wk when grown in stroma-noncontact cultures supplemented with both MIP-1 alpha plus IL-3. This effect depends on soluble (ill-defined) stromal factors, and results from a direct interaction of these cytokines with the progenitor population or its progeny, but not the stroma.