Stem Cells Concise Review Autocrine/Paracrine Mechanisms in Human Hematopoiesis ANNA JANOWSKA-WIECZOREK,a MARCIN MAJKA,b JANINA RATAJCZAK,b MARIUSZ Z. RATAJCZAKb a
Department of Medicine, University of Alberta, Edmonton, AB, Canada; bDepartment of Pathology & Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA Key Words. Autocrine growth · Growth factors · CD34+ cells · Cytokines · Chemokines
A BSTRACT Autocrine/paracrine regulatory mechanisms are believed to play a role in the pathophysiology of several hematologic malignancies. Evidence is accumulating that various growth factors, cytokines, and chemokines are expressed and secreted by normal early and differentiated hematopoietic cells and thus could also regulate normal hematopoiesis in an autocrine/paracrine manner. In this review we summarize recent advances in identification and understanding of the role of autocrine/paracrine axes
in the growth of both malignant and normal human hematopoietic cells. Better understanding of intercellular crosstalk operating in normal and pathological states and the mechanisms regulating synthesis of these endogenously produced factors (potential targets for various pharmacological approaches) may allow us to improve antileukemia treatments, undertake more efficient ex vivo stem cell expansion, and develop other therapeutic strategies. Stem Cells 2001;19:99-107
INTRODUCTION The development of hematopoietic cells is regulated by hematopoietic growth factors, cytokines, and chemokines secreted by: A) hematopoietic accessory cells (e.g., fibroblasts, endothelial cells, macrophages, and osteoblasts) residing in the bone marrow (BM) microenvironment; B) various nonhematopoietic organs (e.g., liver, kidney), and C) normal T lymphocytes (e.g., as part of Th1- and Th2mediated responses) [1-8]. All these factors together modulate the biology of early hematopoietic cells present in the BM niches (Fig. 1). The existence of several putative autocrine/paracrine loops was first demonstrated in human hematologic malignancies [9-14]. More recently, we and others used reverse transcriptase-polymerase chain reaction (RTPCR) to demonstrate the presence of mRNA for several
growth factors, cytokines, and chemokines in normal human CD34+ cells [15-18], megakaryocytes [19-20], and other BM mononuclear cells (BMMNC) [21]. We also demonstrated that various growth factors, cytokines, and chemokines are secreted by normal human early and differentiated hematopoietic cells and thus could regulate hematopoiesis in an autocrine/paracrine manner [17, 2225]. These recent observations may change our traditional view of regulation of the early stages of hematopoietic development. Here we review the evidence supporting the role of autocrine/paracrine axes in the growth of malignant as well as normal human hematopoietic cells. We will focus on the expression of these regulators by hematopoietic cells as well as on the biological consequences of their endogenous secretion.
Correspondence: Mariusz Z. Ratajczak, M.D., Ph.D., Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, University of Pennsylvania, 405A Stellar Chance Labs, 422 Curie Blvd., Philadelphia, Pennsylvania 19104, USA. Fax: 215-573-6317; e-mail:
[email protected] Received December 15, 2000; accepted for publication February 2, 2001. ©AlphaMed Press 1066-5099/2001/$5.00/0
STEM CELLS 2001;19:99-107
www.StemCells.com
100
Figure 1. Early hematopoietic cells which reside in BM niches are under the influence of various growth factors. Cytokines and chemokines are secreted by stromal fibroblasts (1) and endothelium (2) or are derived from other organs (kidney, liver, etc.) and arrive via the blood stream (3), accessory cells (4), differentiating hematopoietic cells (5), osteoblasts (6), and, in an autocrine manner, early hematopoietic cells (7). Interaction of hematopoietic cells with adhesion receptors expressed in the hematopoietic microenvironment may also play a regulatory role (8).
AUTOCRINE/PARACRINE GROWTH IN HEMATOLOGIC MALIGNANCIES It is widely accepted that leukemic cells proliferate due to changes in the activation of proto-oncogenes and/or an inactivation of anti-oncogenes [26]. Activating changes may affect various elements of intracellular stimulatory signaling pathways such as: A) surface receptors; B) downstream signaling proteins; C) transcription factors, and D) cell cycle genes. Similarly the inactivating mutations usually occur in the proteins which negatively regulate: A) intracellular proliferative signaling pathways; B) cell survival, or C) the cell cycle. Factors endogenously secreted by leukemic cells may contribute to leukemogenesis, and cells that synthesize a growth factor and simultaneously express on their surface its corresponding receptor may proliferate by a self-stimulatory or autocrine mechanism. If the factor is secreted by the cells and activates surface receptors, it operates via a “public autocrine loop” [9-13]. In contrast, if the mitogenic signal is generated without evidence of factor secretion, the growth factor may activate a corresponding receptor intracellularly via a “private autocrine loop” [13, 27-29]. In this latter situation a ligand-receptor interaction occurs in the intracellular compartment. It is generally accepted that cells that secrete active growth factors, and thus depend on “public autocrine loops,” proliferate at high density in cultures and that their growth is
Autocrine/Paracrine Mechanisms in Human Hematopoiesis inhibited in the presence of antibodies that neutralize the putative stimulator of autocrine growth. In contrast, the growth of cells in which the autocrine factor interacts with the corresponding receptor intracellularly is neither density-dependent nor inhibited by neutralizing antibodies. There is growing evidence that both mechanisms may affect malignant hematopoiesis. The existence of “public autocrine loops” has been described in cells derived from the blood of patients with acute myelogenous leukemia ([AML] GM-CSF, G-CSF, macrophage-CSF [M-CSF], and interleukin 1β [IL-1β] [9-11]), chronic myelogenous leukemia (IL-3, G-CSF, M-CSF, and IL-1β) [12, 30], and multiple myeloma (IL-6 and kit ligand [KL]) [31]. A “private autocrine loop” has been shown to operate in some human primary AML cells as well as murine experimental models [27-29]. It has been reported that IL-3-dependent murine cell lines (32D and FDC-P1) proliferate when IL-3 is expressed in these cells even as an intracellular, nonsecretable protein. However, experiments in transgenic mice expressing IL-3, GM-CSF, and IL-6 in hematopoietic organs have demonstrated that autocrine/paracrine expression of these factors results in a chronic hyperproliferative state but not acute neoplastic transformation [14]. This supports the notion that several circumstances are necessary for malignant transformation, and autocrine or paracrine production of hematopoietic growth factors or cytokines alone is not sufficient for leukemogenesis. Other “second hit”-type mutations in oncogenes and/or anti-oncogenes are necessary to transform cells. In this context factors secreted by leukemic cells may, for example, inhibit apoptosis of leukemic blasts, allowing these cells to accumulate and become targets for a “second hit,” activating oncogenes and/or inactivating anti-oncogenes. Factors secreted by leukemic cells may also act in a paracrine manner on surrounding cells; for example, stromal or endothelial cells can be stimulated by one factor to produce other multiple hematopoietic growth factors which in turn may affect growth of leukemic blasts. Certain factors secreted by leukemic cells may stimulate expansion and activation of endothelium (e.g., vascular endothelial growth factor [VEGF], fibroblast growth factor [FGF-2]) or BM stromal fibroblasts (platelet-derived growth factor) [32-36]. Subsequently, such expanded and activated endothelium and/or stroma could provide a more permissive environment for leukemic growth [32-36]. Expanded endothelium resulting from paracrine stimulation by VEGF or FGF-2 (both shown to be secreted by leukemic blasts) has been postulated to play an important role in the pathogenesis and progression of human acute leukemias [32, 35, 36], chronic myeloid leukemia [33, 34], myeloproliferative disorders [37], and multiple myelomas [38]. These paracrine effects of leukemic cells on marrow endothelium closely resemble the
Janowska-Wieczorek, Majka, Ratajczak et al.
101
expansion of endothelium and neo-angiogenesis observed in solid tumor tissues [39-42]. NORMAL HUMAN HEMATOPOIETIC CELLS EXPRESS SEVERAL GROWTH FACTORS, CYTOKINES, AND CHEMOKINES We now know that several growth factors, cytokines, and chemokines are expressed and secreted by normal human early and differentiated hematopoietic cells and thus may regulate hematopoiesis in an autocrine/paracrine manner. For example, it has been reported that normal human CD34+ cells express mRNA for IL-1β [15] and tranforming growth factor (TGF)β1 [16, 43-45]. Similarly, we found that both CD34+ and CD34+kit+ cells enriched in stem/progenitor cells express mRNA for KL and FLT-3 [17]. Recently, it was found that CD34+ cells express mRNA for erythropoietin (EPO) [46-48] and stromal-derived factor (SDF)-1 [49]. Similarly, mRNA for IL-1β, IL-6, GM-CSF, and tumor necrosis factor (TNF)-α was found to be expressed in normal human megakaryoblasts [19, 20] and mRNA for EPO in normal erythroblasts [46]. Finally, several cytokines and growth factors were found to be MRNA FOR
expressed at the mRNA level in peripheral blood-derived MNC [21]. To extend these studies we isolated highly purified CD34+ cells, myeloblasts, megakaryoblasts, and erythroblasts and found these cells expressed mRNA for various growth factors, cytokines, and chemokines (Table 1) [23, 24]. The hematopoietic growth factors we selected are known to be regulators of mesodermal development and activate receptors possessing intrinsic tyrosine kinase activity. We found that human BM-derived CD34+ cells express mRNA for KL, FLT-3, FGF-2, VEGF, hepatocyte growth factor (HGF), and insulin-like growth factor (IGF)-1. We also observed that normal human BM CD34+ cells express mRNA for growth factors and cytokines that may stimulate cell proliferation (thrombopoietin [TPO] and IL-1) or alternatively inhibit it (TNF-α, interferon-α, and Fas-L). On the other hand, mRNA for M-CSF and nerve growth factor-β was not expressed in these cells. We were also not able to detect mRNA for IL-3, IL-6, EPO, G-CSF, and GM-CSF. However, evaluating whether these cells express mRNA for various chemokines, we found mRNAs for macrophage
Table 1. RT-PCR analysis (30 cycles) of highly purified CD34+ cells, myeloblasts, erythroblasts, and megakaryoblasts for expression of various growth factors, cytokines, and chemokines. Cells from three independent donors were analyzed with similar results. CD34+ BM
CFU-GM-derived
BFU-E-derived
CFU-Meg-derived
KL FLT-3 M-CSF FGF-2 VEGF HGF IGF-I NGF-β
+ + – + + + + –
+ + + + + – – –
+ + + + + + + –
+ – + + + + + –
IL-1 IL-3 IL-6 EPO TPO G-CSF GM-CSF TNF-α IFN-α Fas-L
+ – – – + – – + + +
– – – – + – – + + +
– – – – + – – + + +
– – – – + – + + + +
MIP-1α MIP-1β RANTES MCP-1 MCP-2 MCP-3 MCP-4 IL-8 IP-10 MDC SDF-1 PF-4
+ + + – – + + + + + – +
+ + + – + + + – + – – +
+ – – – + – + – + – – +
+ + + – + + + + + – – +
Autocrine/Paracrine Mechanisms in Human Hematopoiesis
102
inflammatory protein (MIP)-1α, MIP-1β, RANTES, MCP-3, MCP-4, IL-8, IP-10, MDC, and PF-4 in highly purified human BM CD34+ cells. Similarly, mRNA for several hematopoietic regulators was found to be expressed in colony-forming unit-granulocyte, macrophage (CFU-GM)-, BFU-E-, and CFU-megakaryocyte (Meg)-derived cells (Table 1). Furthermore, the micro-array strategy, a powerful tool to screen mRNAs expressed in human cells, has also been successfully employed to screen mRNA molecules expressed in normal and malignant human hematopoietic cells [25, 50]. NORMAL HUMAN HEMATOPOIETIC CELLS SECRETE SEVERAL GROWTH FACTORS, CYTOKINES, AND CHEMOKINES Although the expression of various hematopoietic regulators has been demonstrated at the mRNA level, it has not been clear whether these regulators are expressed at the protein level and secreted by early normal human hematopoietic cells. Functional studies performed with anti-TGF-β-blocking monoclonal antibodies (mAbs) [16], as well as studies of downregulation of mRNA encoding KL and FLT-3 using antisense oligomers [17], supported the notion that these factors are expressed at the protein level and modulate the biology of CD34+ cells. Moreover, in a recent study using immunohistochemistry, it has been demonstrated that normal human CD34+ cells express IL-8 and IL-1 proteins [18]. In our recent studies to correlate RT-PCR expression with protein secretion, we used sensitive, commercially available enzyme-linked immunosorbent assays (ELISA) to ascertain whether normal human BM-derived CD34+ cells, myeloblasts, erythroblasts, and megakaryoblasts secrete detectable amounts of various hematopoietic growth factors, cytokines, and chemokines (Table 2) [17, 22-24, 51]. We found that highly
purified human CD34+ cells secrete many regulatory proteins at picogram levels which could potentially: A) affect the proliferation of CD34+ cells either by their stimulation (e.g., KL, FLT-3, and TPO) or inhibition (e.g., TGF-β1, TGF-β2, and PF-4); B) autoprotect these cells from undergoing apoptosis (e.g., KL, FLT-3, TPO, and IGF-I), and C) attract and/or stimulate human endothelial cells (e.g.,VEGF, HGF, FGF-2, and IL-8). Moreover, using the sensitive ELISA we also found that highly purified human CD34+ cells secrete chemokines such as MIP-1α, MIP-1β, RANTES, IL-8, and PF-4. The potential biological significance of these chemokines is intriguing. Endogenously secreted chemokines could: A) attract other cells; B) stimulate angiogenesis, and C) regulate cell migration and adhesion. We also observed that several of these chemokines are secreted by CFU-GM-, BFU-E-, and CFU-Meg cells derived from ex vivo-expanded CD34+ cells. While we were able to detect mRNA for different growth factors and cytokines in normal early human hematopoietic cells (Table 1), it is not surprising that many of these factors were not detectable at the protein level in media conditioned by these cells (Table 2). EXPERIMENTAL METHODS FOR STUDYING AUTOCRINE MECHANISMS Several methods are currently available to study the biological function of putative autocrine regulatory loops. Generally, the function of these loops may be perturbed by using: A) mAbs against ligands and their corresponding receptors [16]; B) antisense oligodeoxynucleotides against mRNA encoding factors or their receptors [17]; C) modified ligands or synthetic molecules that block surface receptors [52]; D) an intracrine strategy [53], and finally, E) by
Table 2. Various growth factors, cytokines, and chemokines detected by ELISA in media conditioned by normal human hematopoietic cells. Cells from three to five independent healthy donors were analyzed with similar results. Cells CD34+
MyeloCFU-GM-derived ErythroBFU-E-derived MegCFU-Meg-derived
Factors detected by ELISA VEGF, HGF, TPO, FGF-2, KL, IGF-I, FLT-3, TGF-β1, TGF-β2, RANTES, PF-4, MIP-1α, MIP-1β, MCP-1, IL-8, IL-16
Factors not detected GM-CSF, TNF-α, INF-α, INF-γ, IL-7
VEGF, FLT-3
KL, FGF-2, IL-7, HGF, RANTES, TPO, PF-4
VEGF, TGF-β1
FGF-2, HGF, TPO, FLT-3, INF-α, IL-7, RANTES, MIP-1α, MIP-1β, PF-4
VEGF, TGF-β1, FGF-2, RANTES, PF-4 MCP-1
KL, HGF, IGF-I, GM-CSF, TGF-β2, INF-α, IL-7, MIP-1α
*Cells were cultured for 24 h in serum-free medium at a concentration of 1 × 106/ml of medium. The sensitivities (pg/ml) of the ELISA were as follows: HGF > 40 ,VEGF > 5, TPO > 15, FGF-2 > 3, TGF-β1 > 31, TGF-β2 > 31, GM-CSF > 7, INF-α > 5, INF-γ > 10, TNF-α > 10, IGF-I > 12, FLT-3 > 7, KL > 9, MIP-1α > 31, MIP-1β > 31, MCP-1 > 31, PF-4 > 10, IL-8 > 1.
Janowska-Wieczorek, Majka, Ratajczak et al. “homologous-recombination” which allows “knock-out” of appropriate genes involved in the particular axes [54]. Generally, blocking-mAbs are more suitably used for investigating public, and antisense oligomers for studying private, autocrine regulatory loops. BIOLOGICAL IMPLICATIONS OF ENDOGENOUS EXPRESSION AND SECRETION OF HEMATOPOIETIC REGULATORS Cells that express and synthesize a growth factor or growth-regulating cytokine and simultaneously express the corresponding receptor for this factor have the potential for self-stimulatory or autocrine growth. Nevertheless, endogenously secreted factors, in addition to their influence on proliferation, may also have other biological functions stimulating cells in an autocrine or paracrine manner, and the proper biological combination of these various factors may be necessary to provide stimulatory signals and gradients to the cells. Hence various scenarios in which these mechanisms operate are possible. For example, endogenously secreted factors may serve as chemoattractants for other hematopoietic cells (accessory cells, facilitating cells, etc.), stimulate the secretion of other regulatory molecules, modulate the expression of adhesion molecules on the cell surface (and thus regulate their adhesion and homing), and/or influence the survival of the hematopoietic cells. It has been reported that neutralizing (by mAb) of TGFβ1, which is endogenously secreted by cord blood-derived CD34+ cells, increased the formation of hematopoietic colonies [16]. Moreover, it has been shown that blocking of the autocrine inhibitory TGF-β1-TGF-β1R axis improved ex vivo expansion of these cells [16, 45]. Hence inhibition of the autocrine negative regulatory axes could provide a useful strategy for optimizing the ex vivo expansion of early hematopoietic cells. Since the number of progenitor cells in cord blood is limited, this strategy could significantly expand their availability for clinical transplantation. Autocrine negative regulatory axes could be perturbed by mAbs or antisense oligodeoxynucleotides targeted against negative regulators and/or their corresponding receptors. Similarly, by employing appropriate antisense oligomers targeted against mRNA encoding several tyrosine kinase receptors, we were able to show that perturbation of expression of receptors for KL and FLT-3 [17], but not VEGF, FGF-2, or HGF [33, 55, 56], affects the proliferation and survival of human CD34+ cells, a finding which suggests that both KL and FLT-3 may operate as positive autocrine regulators in these cells [17]. In agreement with these observations, other investigators have also recently suggested the secretion of KL by normal CD34+ cells, having found that kitlow/- CD34+ cells began to proliferate after transduction with kit cDNA, even when
103
exogenous KL was absent from the culture medium [57]. Moreover, since human CD34+ cells secrete TPO and express c-mpl [58, 59], a putative role for c-mpl-TPO in autocrine regulation of CD34+ cells has also been postulated but requires further investigation. Similarly, as human CD34+ cells express CD95 (Apo/Fas) and TNF-R (p55 and p7E) (Fig. 2), and as we found that mRNA for Fas-L and TNF-α is expressed in these cells (Table 1), we suggest that two other negative regulatory axes (Fas-L-CD95 and TNF-α-TNF-R), in addition to the TGF-β1-TGF-βR axis [16, 43-45, 60], may operate in the early stages of hematopoiesis. Although the precise role in normal hematopoiesis of the numerous endogenously secreted hematopoietic regulators requires further investigation, it is worth noting that even if endogenous factors are secreted at very low levels, they may be much more biologically effective than corresponding recombinant proteins employed at similar doses [61]. Thus the endogenously secreted factors we identified (and likely those as yet undiscovered) may play a key role in the biology of early hematopoietic cells in vivo. In vitro, where recombinant molecules are used, this effect will likely differ. As an example, autocrine TGF-β1 secretion in human hematopoietic progenitors upregulates bcl-2 expression and plays an important role in regulating the survival and differentiation of primitive proliferating hematopoietic progenitors by cell cycle-independent mechanisms [44], whereas exogenously added TGF-β1 affects the cell cycle and inhibits proliferation of these cells [16, 45]. Studying autocrine/paracrine mechanisms regulating normal human hematopoiesis we observed that CD34+ cells cultured ex vivo in conditioned media harvested from other CD34+ cells survive better. This suggested that in the mixture of various factors secreted by these cells, the effect of antiapoptotic factors prevailed [23, 24]. We also observed that conditioned media harvested from CD34+ cells chemoattract other CD34+ cells as well as normal human lymphocytes [23, 24]. Since CD34+ cells do not secrete SDF-1 (Table 2), this observation suggests that another important as yet unidentified chemoattractant for human CD34+ cells exists and is endogenously secreted by them [23, 24]. The fact that CD34+ cells also attract lymphocytes suggests that this mechanism could be employed to attract certain subpopulations of lymphoid cells or facilitating cells which perhaps may play a regulatory role in the development of early hematopoietic cells [24]. We also reported that conditioned media harvested from CD34+ cells containing VEGF, FGF-2, HGF, and IL-8 stimulated proliferation of human endothelium (Table 2). Thus, crosstalk between hematopoietic cells and endothelium is not only evident in malignant hematopoiesis but also during normal hematopoiesis [32, 35, 40, 42, 53, 62]. Further, we found that some of the identified β-chemokines secreted by CD34+ cells
104
Autocrine/Paracrine Mechanisms in Human Hematopoiesis
Figure 2. Expression of TNF-R1 (p55-CD120a), TNF-R2 (75p-CD120b), and CD95 (APO-1/Fas) on BM CD34+ BMMNC. BMMNC were isolated from BM aspirates of healthy donors by Ficoll-gradient centrifugation and stained with mAb against CD34 antigen (fluorescein isothiocyanate) and TNF-R1, TNF-R2, and CD95 receptors (phycoerythrin [PE]). A) Forward and side scatter analysis of CD34+ cells isolated from BMMNC isolated from BM CD34+ cells. Lymphocyte region is defined by R1. B) Purity of CD34+ cells is shown by immunostaining with PE-anti-CD34 mAb. C) Analysis of CD34+ cells labeled with PE-anti-TNF-R1 mAb. D) Analysis of CD34+ cells labeled with PE-anti-TNF-R2 mAb. E) Analysis of CD34+ cells labeled with PE-anti-CD95 mAb. All the mAbs were from Pharmingen (San Diego, CA). Data from at least five different donors were analyzed with similar results. Data from a representative donor are presented.
that bind to CCR5, such as MIP-1α, MIP-1β, and RANTES, may interfere with the infectability of these cells by R5 HIV (macrophagotropic human immunodeficiency virus) by competing with the virus for binding to CCR5 [22, 51]. Similarly RANTES endogenously secreted by human megakaryoblasts and megakaryocytes protects these cells from infection by R5 HIV. Thus, since endogenously secreted β-chemokines could contribute to AIDS-free status, we predict that therapeutic agents that may stimulate the endogenous synthesis of these chemokines in human hematopoietic cells could protect them from HIV infection, and we recommend their development in the future. OTHER POTENTIAL HEMATOPOIETIC REGULATORS EXPRESSED AND/OR SECRETED BY EARLY NORMAL HUMAN HEMATOPOIETIC CELLS In addition to cytokines, growth factors, and chemokines, there are many other proteins that are secreted by different subsets of normal human hematopoietic cells and may modulate hematopoiesis. The most important candidates are matrix
metalloproteinases [63], tissue inhibitors of metalloproteinases, morphogenetic proteins, complement proteins (C3), soluble receptors (sFas, sgp130, sTNF-R1, sTNF-R2, uPAR, etc.), and soluble adhesion molecules (cCD14, sCD31, sLselectin, sP-selectin, etc.). These proteins are detectable by sensitive ELISA, zymography, reverse zymography, Westernblotting, and immunocytochemistry. PROTEOMICS STRATEGY TO IDENTIFY PROTEINS SECRETED BY EARLY HUMAN HEMATOPOIETIC CELLS In the last few years, a powerful proteomics strategy has been developed, and we are employing it to screen conditioned media harvested from CD34+ cells, as well as lineage-expanded BFU-E-, CFU-GM-, and CFU-Meg-derived cells, for the presence of various proteins. First, the conditioned media are concentrated and then the proteins present in these concentrates are fractionated, separated by twodimensional electrophoresis, isolated from the gels, and subjected to mass-spectrophotometry. Finally, the identified peptides are screened against a proteomics database
Janowska-Wieczorek, Majka, Ratajczak et al. [64]. This strategy is helping us to identify other hematopoietic regulators secreted by normal human hematopoietic cells. In conclusion, evidence is accumulating that normal human hematopoietic cells (BM or PB CD34+ cells, myeloblasts, erythroblasts, and megakaryoblasts) secrete numerous growth factors, cytokines, and chemokines which contribute to intercellular crosstalk networks and regulate the various
105
stages of hematopoiesis. We believe that these observations direct us towards a new area of investigation into human hematopoiesis. ACKNOWLEDGMENT This work was supported by an NIH grant R01 HL61796-01 to M.Z.R. and a Canadian Blood Services R & D grant (XE000D) to A.J.W.
R EFERENCES 1 Verfaille C. Adhesion receptors as regulators of the hematopoietic process. Blood 1998;92:2609-2612. 2 Taichman RS, Emerson SG. The role of osteoblasts in the hematopoietic microenvironment. STEM CELLS 1998;16:7-15. 3 Sharkis SJ, Cremo C, Collector MI et al. Thymic regulation of hematopoiesis. Isolation of helper and suppressor populations using counterflow centrifugal elutriation. Blood 1986;68:787-789. 4 Morel PA, Oriss TB. Crossregulation between Th1 and Th2 cells. Crit Rev Immunol 1998;18:275-303. 5 Ratajczak MZ, Gewirtz AM. The biology of hemopoietic stem cells. Semin Oncol 1995;22:210-217. 6 Rafii S, Mohle R, Shapiro F et al. Regulation of hematopoiesis by microvascular endothelium. Leuk Lymphoma 1997;27:375-386. 7 Rafii S, Shapiro F, Pettengell R et al. Human bone marrow microvascular endothelial cells support long-term proliferation and differentiation of myeloid and megakaryocytic progenitors. Blood 1995;86:3353-3363. 8 Schuchert MJ, Wright RD, Colson YL. Characterization of a newly discovered T-cell receptor β-chain heterodimer expressed on a CD8+ bone marrow subpopulation that promotes allogeneic stem cell engraftment. Nat Med 2000;6:904-909. 9 Young DC, Griffin JD. Autocrine secretion of GM-CSF in acute myeloblastic leukemia. Blood 1986;68:1178-1181. 10 Young DC, Wagner K, Griffin JD. Constitutive expression of the granulocyte-macrophage colony-stimulating factor gene in acute myeloblastic leukemia. J Clin Invest 1997;79:100-106. 11 Rambaldi A, Wakamiya N, Vellenga E et al. Expression of the macrophage colony-stimulating factor and c-fms genes in human acute myeloblastic leukemia cells J Clin Invest 1988;81:1030-1035. 12 Jiang X, Lopez A, Holyoake T et al. Autocrine production and action of IL-3 and granulocyte colony-stimulating factor in chronic myeloid leukemia. Proc Natl Acad Sci USA 1999;96:12804-12809. 13 Browder TM, Dunbar CE, Nienhuis AW. Private and public autocrine loops in neoplastic cells. Cancer Cells 1989;1:9-17. 14 Soma T, Dunbar CE. In vivo models for studying the role of autocrine or paracrine growth factors in hematologic malignancies. Exp Hematol 1995;23:385-388.
15 Watari K, Lansdorp PM, Dragowska W et al. Expression of interleukin-1β gene in candidate human hematopoietic stem cells. Blood 1994;84:36-42. 16 Cardoso AA, Li ML, Batard P et al. Release from quiescence of CD34+ CD38– human umbilical cord blood cells reveals their potentiality to engraft adults. Proc Natl Acad Sci USA 1993;90:8707-8711. 17 Ratajczak MZ, Kuczynski W, Sokol D et al. Expression and physiologic significance of Kit ligand and stem cell tyrosine kinase-1 receptor ligand expression in normal human CD34+, C-Kit R+ marrow cells. Blood 1995;86:2161-2167. 18 Behringer D, Kresin V, Henschler R et al. Cytokine and chemokine production by CD34+ haematopoietic progenitor cells: detection in single cells. Br J Haematol 1997;97:9-14. 19 Wickenhauser C, Lorenzen J, Thiele J et al. Secretion of cytokines (interleukin-1α, -3, and -6 and granulocytemacrophage colony stimulating factor) by normal human bone marrow megakaryocytes. Blood 1995;85:685-691. 20 Jiang S, Levine JD, Fu Y et al. Cytokine production by primary bone marrow megakaryocytes. Blood 1994;84:4151-4156. 21 Cluitmans FHM, Esendam BHJ, Landegent JE et al. Constitutive in vivo cytokine and hematopoietic growth factor gene expression in the bone marrow and peripheral blood of healthy individuals. Blood 1995;85:2038-2044. 22 Majka M, Rozmyslowicz T, Lee B et al. Bone marrow CD34+ cells and megakaryoblasts secrete β-chemokines; implications for infectability by M-tropic human immunodeficiency virus (R5 HIV). J Clin Invest 1999;104:1739-1749. 23 Majka M, Ratajczak J, Ehrenman K et al. Normal human CD34+ cells and ex vivo expanded myeloblasts, megakaryoblasts and erythroblasts secrete various growth factors, cytokines and chemokines: biological significance of endogenous secretion. Blood 1999;94(suppl 1):465a. 24 Majka M, Janowska-Wieczorek A, Ratajczak J et al. Numerous growth factors, cytokines and chemokines are secreted by normal human CD34+ cells, myeloblasts, erythroblasts and megakaryoblasts and regulate hematopoiesis in an autocrine/paracrine manner. Blood 2001 (in press). 25 Phillips RL, Ernst RE, Brunk B et al. The genetic program of hematopoietic stem cells. Science 2000;288:1635-1640. 26 Gewirtz AM, Sokol DL, Ratajczak MZ. Nucleic acid therapeutics: state of the art and future prospects. Blood 1998;92:712-736.
106
Autocrine/Paracrine Mechanisms in Human Hematopoiesis
27 Lang RA, Metcalf NM, Gough AR et al. Expression of hematopoietic growth factor cDNA in a factor-dependent cell line results in autonomous growth and tumorigenecity. Cell 1985;43:531-542.
43 Fortunel N, Hatzfeld J, Kisselev S et al. A release from quiescence of primitive human hematopoietic stem/progenitor cells by blocking their cell-surface TGF-β type II receptor in a short-term in vitro assay. STEM CELLS 2000;18:102-111.
28 Browder TM, Abrams JS, Wong PMC et al. Mechanism of autocrine stimulation in hematopoietic cells producing interleukin-3 after retrovirus-mediated gene transfer. Mol Cell Biol 1989;9:204-213.
44 Pierelli L, Marone M, Bonanno G et al. Modulation of bcl-2 and p27 in human primitive proliferating hematopoietic progenitors by autocrine TGF-β1 is a cycle-independent effect and influences their hematopoietic potential. Blood 2000;95:3001-3010.
29 Rogers SY, Bradbury D, Kozlowski R et al. Evidence for internal autocrine regulation of growth in acute myeloblastic leukemia cells. Exp Hematol 1994;22:593-598. 30 Specchia G, Liso V, Capalbo S et al. Constitutive expression of IL-1β, M-CSF and c-fms during the myeloid blastic phase of chronic myelogenous leukaemia. Br J Haematol 1992;80:310-316. 31 Lemoli RM, Fortuna A, Grande A et al. Expresion and functional role of c-kit ligand (SCF) in human multiple myeloma cells. Br J Haematol 1994;88:760-769. 32 Perez-Atayde AR, Sallan SE, Tedrow U et al. Spectrum of tumor angiogenesis in the bone marrow of children with acute lymphoblastic leukemia. Am J Pathol 1997;150:815-821. 33 Ratajczak MZ, Ratajczak J, Machalinski B et al. Role of vascular endothelial growth factor (VEGF), placenta derived growth factor (PlGF)/Flt-1 and Flk-1/KDR receptor axes in human adult and fetal hematopoiesis. Br J Haematol 1998;103:969-979. 34 Majka M, Kowalczyk D, Gee M et al. Evidence that both human and murine bcr-abl+ cells stimulate vasculogenesis in vivo in matrigel implants: potential therapeutic implications. Blood 1999;94(suppl 1):100a. 35 Padro T, Ruiz S, Bieker R et al. Increased angiogenesis in the bone marrow of patients with acute myeloid leukemia. Blood 2000;95:2637-2644. 36 Fiedler W, Graeven U, Ergun S et al. Vascular endothelial growth factor, a possible paracrine growth factor in human acute myeloid leukemia. Blood 1997;89:1870-1875. 37 Goran L, Lerner R, Sundelin P et al. Bone marrow in polycythemia vera, chronic myelocytic leukemia, and myelofibrosis has an increased vascularity. Am J Pathol 2000;157:15-19. 38 Rajkumar SV, Fonesca R, Witzig TE et al. Bone marrow angiogenesis in patients achieving complete response after stem cell transplantation for multiple myeloma. Leukemia 1999;13:469-472. 39 Risau W. Mechanisms of angiogenesis. Nature 1997;386:671674. 40 Veikkola T, Alitalo K. VEGFs, receptors and angiogenesis. Cancer Biol 1999;9:211-220. 41 Folkman J, D’Amore PA. Blood vessel formation: what is its molecular basis? Cell 1996;87:1153-1155. 42 Yoshida S, Ono M, Shono T et al. Involvement of interleukin8, vascular endothelial growth factor, and basic fibroblast growth factor in tumor necrosis factor alpha-dependent angiogenesis. Mol Cell Biol 1997;17:4015-4023.
45 Fortunel NO, Hatzfeld A, Hatzfeld JA. Transforming growth factor-β: pleiotropic role in the regulation of hematopoiesis. Blood 2000;96:2022-2036. 46 Stopka T, Zivny JH, Stopkova P et al. Human hematopoietic progenitors express erythropoietin. Blood 1998;91:3766-3772. 47 Sato T, Maekawa T, Watanabe S et al. Erythroid progenitors differentiate and mature in response to endogenous erythropoietin. J Clin Invest 2000;106:263-270. 48 Pech N, Olivier H, Goldwasser E. Further study of internal autocrine regulation of multipotent hematopoietic cells. Blood 1993;82:1502-1506. 49 Aiuti A, Turchetto L, Cota M et al. Human CD34+ cells express CXCR4 and its ligand stromal derived factor-1. Implications for infection by T-cell tropic human immunodeficiency virus. Blood 1999;94:62-73. 50 Graf L, Torok-Storb B. Comparison of gene expression in CD34+ cells from bone marrow and G-CSF mobilized peripheral blood by high density oligonucleotide array analysis. Blood 2000;96(suppl 1):517a. 51 Majka M, Rozmyslowicz T, Ratajczak J et al. The limited infectability by R5 HIV of CD34+ cells from thymus, cord and peripheral blood and bone marrow is explained by their ability to produce β-chemokines. Exp Hematol 2000;28:1334-1342. 52 Dinarello CA. The role of the interleukin-1- receptor antagonist in blocking inflammation mediated by interleukin-1. N Engl J Med 2000;343:732-734. 53 Onai N, Zhang Y, Yoneyama H et al. Impairment of lymphopoiesis and myelopoiesis in mice reconstituted with bone marrow-hematopoietic progenitor cells expressing SDF-1intrakine. Blood 2000;96:2074-2080. 54 Ratajczak MZ, Gewirtz AM. Current experimental strategies for investigating human hematopoietic stem cell biology. [Editorial Review]. Folia Histochem Cytobiol 1996;34:59-67. 55 Ratajczak MZ, Ratajczak J, Skorska M et al. Effect of basic (FGF-2) and acidic (FGF-1) fibroblast growth factors on early hematopoietic cell development. Br J Haematol 1996;93:772-782. 56 Ratajczak MZ, Marlicz W, Ratajczak J et al. Effect of hepatocyte growth factor (HGF) on human early haematopoietic cell development. Br J Haematol 1997;99:228-236. 57 Lu L, Heinrich MC, Wang LS et al. Retroviral-mediated gene transduction of c-kit into single hematopoietic progenitor cells from cord blood enhances erythroid colony formation and decreases sensitivity of inhibition by tumor necrosis factor-α and transforming growth factor-β1. Blood 1999;94:2319-2332.
Janowska-Wieczorek, Majka, Ratajczak et al. 58 Solar GP, Kerr WC, Zeigler FC et al. Role of c-mpl in early hematopoiesis. Blood 1998;92:4-10. 59 Ratajczak MZ, Ratajczak J, Marlicz W et al. Recombinant human thrombopoietin (TPO) stimulates erythropoiesis by inhibiting erythroid progenitor cell apoptosis. Br J Haematol 1997;98:8-17. 60 Wallach D, Varfolomeev EE, Malinin NL et al. Tumor necrosis factor receptor and fas signaling mechanisms. Annu Rev Immunol 1999;17:331-367. 61 Wagner L, Yang OO, Garcia-Zepeda EA et al. β-chemokines are released from HIV-1 specific cytolytic T-cell granules complexed to proteoglycans. Nature 1998;391:908-911.
107
62 Cines DB, Pollak ES, Buck CA et al. Endothelial cells in physiology and in the pathophysiology of vascular disorders. Blood 1998;91:3527-3561. 63 Janowska-Wieczorek A, Marquez LA, Nabholtz J-M et al. Growth factors and cytokines upregulate gelatinase expression in bone marrow CD34+ cells and their transmigration through reconstituted basement membrane. Blood 1999;93:3379-3390. 64 Wall DB, Kachman MT, Gong S et al. Isoelectric focusing nonporous RP HPLC: a two-dimensional liquid-phase separation method for mapping of cellular proteins with identification using MALDI-TOF mass spectrometry. Anal Chem 2000;72:1099-1111.
