Effect of hepatocyte growth factor on early human haemopoietic cell development

Cancer non-stem cells as a potent regulator of tumor microenvironment: a lesson from chronic myeloid leukemia

A limited subset of human leukemia cells has a self-renewal capacity and can propagate leukemia upon their transplantation into animals, and therefore, are named as leukemia stem cells, in the early 1990’s. Subsequently, cell subpopulations with similar characteristics were detected in various kinds of solid cancers and were denoted as cancer stem cells. Cancer stem cells are presently presumed to be crucially involved in malignant progression of solid cancer: chemoresitance, radioresistance, immune evasion, and metastasis. On the contrary, less attention has been paid to cancer non-stem cell population, which comprise most cancer cells in cancer tissues, due to the lack of suitable markers to discriminate cancer non-stem cells from cancer stem cells. Chronic myeloid leukemia stem cells generate a larger number of morphologically distinct non-stem cells. Moreover, accumulating evidence indicates that poor prognosis is associated with the increases in these non-stem cells including basophils and megakaryocytes. We will discuss the potential roles of cancer non-stem cells in fostering tumor microenvironment, by illustrating the roles of chronic myeloid leukemia non-stem cells including basophils and megakaryocytes in the pathogenesis of chronic myeloid leukemia, a typical malignant disorder arising from leukemic stem cells.

Dnmt3b catalytic activity is critical for its tumour suppressor function in lymphomagenesis and is associated with c-Met oncogenic signalling

BACKGROUND

DNA methylation regulates gene transcription in many physiological processes in mammals including development and haematopoiesis. It is catalysed by several DNA methyltransferases, including Dnmt3b that mediates both methylation-dependant and independent gene repression. Dnmt3b is critical for mouse embryogenesis and functions as a tumour suppressor in haematologic malignancies in mice. However, the extent to which Dnmt3b's catalytic activity (CA) is involved in development and cancer is unclear.

METHODS

We used a mouse model expressing catalytically inactive Dnmt3b (Dnmt3bCI) to study a role of Dnmt3b's CA in development and cancer. We utilized global approaches including Whole-genome Bisulfite sequencing and RNA-seq to analyse DNA methylation and gene expression to identify putative targets of Dnmt3b's CA. To analyse postnatal development and haematopoiesis, we used tissue staining, histological and FACS analysis. To determine potential involvement of selected genes in lymphomagenesis, we used overexpression and knock down approaches followed by in vitro growth assays.

FINDINGS

We show that mice expressing Dnmt3bCI only, survive postnatal development and develop ICF (the immunodeficiency-centromeric instability-facial anomalies) -like syndrome. The lack of Dnmt3b's CA promoted fibroblasts transformation in vitro, accelerated MLL-AF9 driven Acute Myeloid Leukaemia and MYC-induced T-cell lymphomagenesis in vivo. The elimination of Dnmt3b's CA resulted in decreased methylation of c-Met promoter and its upregulation, activated oncogenic Met signalling, Stat3 phosphorylation and up-regulation of Lin28b promoting lymphomagenesis.

INTERPRETATION

Our data demonstrates that Dnmt3b's CA is largely dispensable for mouse development but critical to prevent tumourigenesis by controlling events involved in cellular transformation.

FUNDING

This study was supported by Department of Anatomy and Cell Biology and Cancer Centre at the University of Florida start-up funds, NIH/NCI grant 1R01CA188561-01A1 (R.O.).

The underestimated role of basophils in Ph+ chronic myeloid leukaemia

Chronic myeloid leukaemia (CML) is a hematopoietic neoplasm defined by the chromosome translocation t(9;22) and the related oncogene, BCR-ABL1. In most patients, leukaemic cells can be kept under control using BCR-ABL1-targeting drugs. However, many patients relapse which remains a clinical challenge. In particular, patients with advanced (accelerated or blast phase) CML have a poor prognosis. So far, little is known about molecular and cellular interactions and features that contribute to disease progression and drug resistance in CML. One key prognostic factor at diagnosis is marked basophilia. However, although basophils are well-known multifunctional effector cells, their impact in CML remains uncertain. In this article, we discuss the potential role of basophils as active contributors to disease evolution and progression in CML. In particular, basophils serve as a unique source of inflammatory, angiogenic and fibrogenic molecules, such as vascular endothelial growth factor or hepatocyte growth factor. In addition, basophils provide vasoactive substances, like histamine as well as the cytokine-degrading enzyme dipeptidyl-peptidase IV which may promote stem cell mobilization and the extramedullary spread of stem and progenitor cells. Finally, basophils may produce autocrine growth factors for myeloid cells. Understanding the role of basophils in CML evolution and progression may support the development of more effective treatment concepts.

Serum Evaluation of Angiogenic Cytokines Basic Fibroblast Growth Factor, Hepatocyte Growth Factor and TNF-ALPHA in Patients with Myelodysplastic Syndromes: Correlation with Bone Marrow Microvascular Density

Recent studies have documented that angiogenesis plays a significant role in haematological malignancies, including mylodysplastic syndromes (MDS). Basic fibroblast growth factor (b-FGF), Hepatocyte growth factor (HGF) and Tumor necrosis factor-α (TNF-α) are multifunctional cytokines that potently stimulate angiogenesis. The aim of the present study was to evaluate the microvascular density (MVD) and the serum levels of these angiogenic factors in patients with myelodysplastic syndromes (MDS). In 61 patients with MDS, MVD was measured in bone marrow biopsies and b-FGF, HGF and TNF-α were determined in the serum of the same patients by enzyme-linked immunosorbent assay (ELISA). Serum levels of b-FGF, HGF and TNF-α as well as MVD in the bone marrow were increased in MDS patients compared to healthy controls (p<0.0001). Levels of b-FGF, HGF and TNF-α were also significantly higher in high-risk for leukemic transformation MDS than in low-risk (p<0.0001). Significant differences were also found regarding MVD in high and low risk patients (p<0.001). Both b-FGF and HGF levels were significant predictors of survival (p<0.0005, log-rank test). The present study showed that serum levels of b-FGF, HGF and TNF-α are significantly increased and dependent on the severity of MDS suggesting that the determination of these parameters may offer considerable information regarding disease progression and prognosis.

The Hepatocyte Growth Factor (HGF)/Met Axis: A Neglected Target in the Treatment of Chronic Myeloproliferative Neoplasms?

Met is the receptor of hepatocyte growth factor (HGF), a cytoprotective cytokine. Disturbing the equilibrium between Met and its ligand may lead to inappropriate cell survival, accumulation of genetic abnormalities and eventually, malignancy. Abnormal activation of the HGF/Met axis is established in solid tumours and in chronic haematological malignancies, including myeloma, acute myeloid leukaemia, chronic myelogenous leukaemia (CML), and myeloproliferative neoplasms (MPNs). The molecular mechanisms potentially responsible for the abnormal activation of HGF/Met pathways are described and discussed. Importantly, inCML and in MPNs, the production of HGF is independent of Bcr-Abl and JAK2V617F, the main molecular markers of these diseases. In vitro studies showed that blocking HGF/Met function with neutralizing antibodies or Met inhibitors significantly impairs the growth of JAK2V617F-mutated cells. With personalised medicine and curative treatment in view, blocking activation of HGF/Met could be a useful addition in the treatment of CML and MPNs for those patients with high HGF/MET expression not controlled by current treatments (Bcr-Abl inhibitors in CML; phlebotomy, hydroxurea, JAK inhibitors in MPNs).

Identification of basophils as a major source of hepatocyte growth factor in chronic myeloid leukemia: a novel mechanism of BCR-ABL1-independent disease progression

Chronic myeloid leukemia (CML) is a hematopoietic neoplasm characterized by the Philadelphia chromosome and the related BCR-ABL1 oncoprotein. Acceleration of CML is usually accompanied by basophilia. Several proangiogenic molecules have been implicated in disease acceleration, including the hepatocyte growth factor (HGF). However, little is known so far about the cellular distribution and function of HGF in CML. We here report that HGF is expressed abundantly in purified CML basophils and in the basophil-committed CML line KU812, whereas all other cell types examined expressed only trace amounts of HGF or no HGF. Interleukin 3, a major regulator of human basophils, was found to promote HGF expression in CML basophils. By contrast, BCR-ABL1 failed to induce HGF synthesis in CML cells, and imatinib failed to inhibit expression of HGF in these cells. Recombinant HGF as well as basophil-derived HGF induced endothelial cell migration in a scratch wound assay, and these effects of HGF were reverted by an anti-HGF antibody as well as by pharmacologic c-Met inhibitors. In addition, anti-HGF and c-Met inhibitors were found to suppress the spontaneous growth of KU812 cells, suggesting autocrine growth regulation. Together, HGF is a BCR-ABL1-independent angiogenic and autocrine growth regulator in CML. Basophils are a unique source of HGF in these patients and may play a more active role in disease-associated angiogenesis and disease progression than has so far been assumed. Our data also suggest that HGF and c-Met are potential therapeutic targets in CML.

Mimics of the dimerization domain of hepatocyte growth factor exhibit anti-Met and anticancer activity

The angiotensin IV analog norleual [Nle-Tyr-Leu-ψ-(CH(2)-NH(2))-Leu-His-Pro-Phe] has been shown recently to act as a hepatocyte growth factor (HGF)/Met antagonist capable of blocking the binding of HGF to the Met receptor, inhibiting HGF-dependent activation of Met, and attenuating HGF-dependent cellular activities. In addition, norleual exhibited marked anticancer activity. Homology between norleual and the dimerization domain (hinge region) of HGF led to the hypothesis that norleual acts by interfering with HGF dimerization/multimerization and functions as a dominant-negative hinge region mimic. To test this hypothesis we investigated the ability of norleual to bind to and inhibit the dimerization of HGF. To further evaluate the idea that norleual was acting as a hinge region mimic, we synthesized a hexapeptide representing the HGF hinge sequence and established its capacity to similarly block HGF-dependent activation of Met and HGF-dependent cellular functions. The hinge peptide not only bound with high affinity directly to HGF and blocked its dimerization but it also inhibited HGF-dependent Met activation, suppressed HGF-dependent cellular functions, and exhibited anticancer activity. The major implication of this study is that molecules targeting the dimerization domain of HGF may represent novel and viable anticancer therapeutic agents; the development of such molecules should be feasible using norleual and the hinge peptide as synthetic templates.

shRNA-mediated decreases in c-Met levels affect the differentiation potential of human mesenchymal stem cells and reduce their capacity for tissue repair

Mesenchymal stem cells/marrow stromal cells (MSC) are adult multipotent cells that can augment tissue repair. We previously demonstrated that culturing MSC in hypoxic conditions causes upregulation of the hepatocyte growth factor (HGF) receptor c-Met, allowing them to respond more robustly to HGF. MSC preconditioned in hypoxic environments contributed to restoration of blood flow after an ischemic injury more rapidly than MSC cultured in normoxic conditions. We now investigated the specific role of HGF/c-Met signaling in MSC function. An shRNA-mediated knockdown (KD) of c-Met in MSC did not alter their phenotypic profile, proliferation, or viability in vitro. However, we determined that while HGF/c-Met signaling does not play a role in the adipogenic differentiation of the cells, the disruption of this signaling pathway inhibited the ability of MSC to differentiate into the osteogenic and chondrogenic lineages. We next assessed the impact of c-Met KD on human MSC function in a xenogeneic hindlimb ischemia injury model. A 70% KD of c-Met in MSC resulted in a significant decrease in their capacity to regenerate blood flow to the ischemic limb, as compared to the MSC transduced with control shRNA. MSC with only a 60% KD of c-Met exhibited an intermediate capacity to restore blood flow, suggesting that MSC function is sensitive to the dosage of c-Met signaling. The current study highlights the significance of HGF/c-Met signaling in the capacity of MSC to restore blood flow after an ischemic injury and in their ability to differentiate into the osteogenic and chondrogenic lineages.

The HGF/c-Met axis synergizes with G-CSF in the mobilization of hematopoietic stem/progenitor cells

As granulocyte-colony-stimulating factor (G-CSF)-induced mobilization of hematopoietic stem/progenitor cells (HSPCs) increases human serum levels of hepatocyte growth factor (HGF), our aim was to investigate the role of HGF and its receptor, c-Met, in the mobilization of HSPC. CD34(+) cells and leukocytes were isolated from the bone marrow (BM) of normal donors and the peripheral blood (PB) of patients mobilized with G-CSF and chemotherapy. Plasma HGF levels were evaluated by ELISA and HGF and c-Met expression by RT-PCR, fluorescence-activated cell sorter (FACS) analysis, and confocal microscopy. Because matrix metalloproteinases (MMPs) facilitate migration across extracellular matrix (ECM) and basement membranes, we also examined expression of MMP-9 and membrane type 1 (MT1)-MMP in hematopoietic cells after HGF stimulation. We found that plasma HGF levels in mobilized (m)PB were higher in patients who are good mobilizers and correlated with their white blood cell (WBC) and CD34(+) cell counts. Moreover, HGF and c-Met expression was significantly higher in mPB CD34(+) cells and leukocytes than in their steady-state BM counterpart cells and was up-regulated by G-CSF. Like G-CSF, HGF increased the secretion of MMP-9 and the expression of MT1-MMP in leukocytes, which was abrogated by the c-Met inhibitor K-252a. This inhibitor also significantly reduced the trans-Matrigel migration of mPB CD34(+) cells toward HGF. Our results suggest that G-CSF-mediated HSPC mobilization occurs in part through the HGF/c-Met axis in HSPC and myeloid cells, eliciting increased production of matrix-degrading enzymes and subsequently facilitating egress of HSPC.

Contribution of human hematopoietic stem cells to liver repair

Immune-deficient mouse models of liver damage allow examination of human stem cell migration to sites of damage and subsequent contribution to repair and survival. In our studies, in the absence of a selective advantage, transplanted human stem cells from adult sources did not robustly become hepatocytes, although some level of fusion or hepatic differentiation was documented. However, injected stem cells did home to the injured liver tissue and release paracrine factors that hastened endogenous repair and enhanced survival. There were significantly higher levels of survival in mice with a toxic liver insult that had been transplanted with human stem cells but not in those transplanted with committed progenitors. Transplantation of autologous adult stem cells without conditioning is a relatively safe therapy. Adult stem cells are known to secrete bioactive factors that suppress the local immune system, inhibit fibrosis (scar formation) and apoptosis, enhance angiogenesis, and stimulate recruitment, retention, mitosis, and differentiation of tissue-residing stem cells. These paracrine effects are distinct from the direct differentiation of stem cells to repair tissue. In patients at high risk while waiting for a liver transplant, autologous stem cell therapy could be considered, as it could delay the decline in liver function.

Over-expression of hepatocyte growth factor in smooth muscle cells regulates endothelial progenitor cells differentiation, migration and proliferation

BACKGROUND

Endothelial repair is one of key events after vascular injury. The mechanisms by which hepatocyte growth factor (HGF) and endothelial progenitor cells (EPCs) may be responsible for re-endothelialization of injured blood vessel wall are poorly understood.

METHODS

Primary culture SMCs were transfected with pcDNA3.0-HGF followed by G418 selection, one of G418-resistant colonies in well was picked, propagated and used as donor cells for further experiments. HGF and VEGF expression in SMCs were detected with western blot and enzyme linked immunosorbent assays (ELISA). Rat EPCs were cultured in untreated, pcDNA3.0 and pcDNA3.0-HGF transfected SMCs conditioned medium with or without anti-VEGF or exogenous recombinant HGF addition. eNOS, KDR and CD31 expression in EPCs was determined by real-time quantitative polymerase chain reaction (RT-qPCR) or flow cytometry; EPCs migration and proliferation were measured by using a modified Boyden chambers and MTT assay respectively.

RESULTS

Abundant and stable expression of HGF was found in G418-resistant colony-derived SMCs. VEGF expression significantly increased in HGF transfected SMCs. Exogenous recombinant HGF (rHGF) markedly up-regulated eNOS mRNA expression in EPCs and promoted EPCs migration and proliferation, but no significant changes were found in KDR and CD31 mRNA expression. HGF transfection in SMCs was more effective than exogenous HGF for EPCs differentiation, proliferation and migration.

CONCLUSIONS

Over-expression of HGF in SMCs can be helpful for promoting EPCs differentiation, increasing EPCs migration and proliferation. It may be responsible for angiogenesis of arteriosclerosis lesions and useful for blood vessel tissue engineering.

Effect of hepatocyte growth factor (HGF) on the level of Survivin & XIAP expression in several human cancer cell lines, after treating with DNA damaging agent

Hepatocyte growth factor (HGF) has opposite biological activities in regulating apoptosis, also underlying molecular mechanisms are not clearly defined. We investigated HGF ability to inhibit cell death, which was induced by Doxorubicin, a DNA damaging agent. Also Survivin and XIAP mRNA levels were compared in HGF treated and non-treated cells. Cell proliferation and death were assessed using MTT assay and dye exclusion tests. Quantitative real-time PCR was used to evaluate Survivin and XIAP expression levels after treatment with HGF. ELISA was performed to quantify HGF secretion in the selected cancer cell lines media. HGF appeared to have inhibitory effect on Doxorubicin induced cell death in all of the studied cell lines. It had minimal effect on XAIP and Survivin expression levels in MRC-5, MOLT-4 and AGS cell lines; except for XIAP expression level in AGS cell line, which was increased substantially after treatment. Surprisingly, in KG-1 cell line, XIAP and Survivin expression levels were significantly reduced after HGF treatment. Although several members of IAP gene family are reported to play role in HGF mediated cytoprotective pathway, we showed that XIAP and Survivin do not seem to be involved.

Differentiation of hematopoietic progenitor cells towards the myeloid and B-lymphoid lineage by hepatocyte growth factor (HGF) and thrombopoietin (TPO) together with early acting cytokines

OBJECTIVES

The effect of stem cell factor (SCF), flt3-ligand (FL), and interleukin (IL)-3 (SF3) in combination with hepatocyte growth factor (HGF), thrombopoietin (TPO), and Hyper-IL-6 on maintenance and differentiation of early human peripheral blood-derived progenitor cells was investigated.

METHODS

Single sorted CD34(+) 38(-) cells were cultured with various combinations of these growth factors in order to identify the most effective cytokine combination. Then, lineage-depleted cells were stimulated for 7 d in bulk culture before they were assessed by flow cytometry and in functional assays.

RESULTS

The highest number of clones in the single-cell assay was obtained after culture with SF3 + TPO + HGF. Cell expansion with SF3 + TPO + HGF yielded an increase of the total cell number (11-fold), the number of CD34(+) cells (sevenfold), colony forming cells (CFC; 13-fold), granulocytes (CD15/66b(+); 45-fold) and B-cells (CD19/20(+); 55-fold). However, the number of long-term culture initiating cells (LTC-IC) decreased from 779 +/- 338 per 1 x 10(5) CD34(+) cells on day 0 to 253 +/- 115 on day 7. In parallel, the number of pluripotent mouse repopulating cells decreased by the factor 11, and no significant change in the proportion of human myeloid or lymphoid cells found in the mouse bone marrow was noted.

CONCLUSION

The observation that mature cells of different lineages are generated and that transplantable multipotent hematopoietic cells are lost during culture suggests the differentiation of early hematopoietic progenitors toward lineage committed cells by the tested cytokines. The detection of cells expressing B-lymphoid markers after culture indicates a possible role in the propagation of B-cells.

Expression of angiogenic factors in chronic myeloid leukaemia: role of the bcr/abl oncogene, biochemical mechanisms, and potential clinical implications

Chronic myeloid leukaemia (CML) is a stem cell disease characterized by an increased production and accumulation of clonal BCR/ABL-positive cells in haematopoietic tissues. The chronic phase of CML is inevitably followed by an accelerated phase of the disease, with consecutive blast crisis. However, depending on genetic stability, epigenetic events, and several other factors, the clinical course and survival appear to vary among patients. Recent data suggest that angiogenic cytokines such as vascular endothelial growth factor (VEGF), are up-regulated in CML, and play a role in the pathogenesis of the disease. These factors appear to be produced and released in leukaemic cells in patients with CML. In line with this notion, increased serum-levels of angiogenic growth factors are measurable in CML patients. In this study we provide an overview of angiogenic growth factors expressed in CML cells, discuss the possible pathogenetic role of these cytokines, the biochemical basis of their production in leukaemic cells, and their potential clinical implications.

High serum hepatocyte growth factor level in patients with non-Hodgkin's lymphoma

Higher pretreatment serum hepatocyte growth factor (HGF) levels were observed in patients with multiple myeloma and Hodgkin's disease, but not in those with non-Hodgkin's lymphoma (NHL). We examined patients' serum levels at diagnosis using enzyme-linked immunosorbent assay and histological expression of HGF in pathological specimens of lymphoma, in relation to clinical features. The subjects were 77 NHL patients and 40 healthy controls. The serum levels of HGF in NHL patients at diagnosis were significantly higher than those in healthy controls (median 1019 vs. 689 pg/mL, P < 0.001). At diagnosis, patients with more than two sites of extranodal involvement (P = 0.001), higher scores of international prognostic index (P = 0.015), and advanced Ann Arbor stage (P = 0.023) had a higher level of serum HGF. Although the association of pretreatment serum HGF level and survival was not significant, a correlation of serial change of serum HGF levels with treatment response was found in limited cases. Furthermore, HGF expression of lymphoma tissues was shown in 18 of 24 (75%) different NHL subtypes, including most of the diffuse large B cell lymphoma (12 of 15, 80%). In conclusion, our study showed higher pretreatment serum HGF levels in NHL patients, which was related to clinical features; and the serial change of HGF seemed to parallel the treatment response. The pathogenic role of HGF in NHL patients was further highlighted by a modest expression of HGF in most of the diffuse large B cell lymphoma.

Oligodeoxynucleotide-mediated inhibition of c-myb gene expression in autografted bone marrow: a pilot study

Antisense oligodeoxynucleotide (ODN) drugs might be more effective if their delivery was optimized and they were targeted to short-lived proteins encoded by messenger RNA (mRNA) species with equally short half-lives. To test this hypothesis, an ODN targeted to the c-myb proto-oncogene was developed and used to purge marrow autografts administered to allograft-ineligible chronic myelogenous leukemia patients. CD34(+) marrow cells were purged with ODN for either 24 (n = 19) or 72 (n = 5) hours. After purging, Myb mRNA levels declined substantially in approximately 50% of patients. Analysis of bcr/abl expression in long-term culture-initiating cells suggested that purging had been accomplished at a primitive cell level in more than 50% of patients and was ODN dependent. Day-100 cytogenetics were evaluated in surviving patients who engrafted without infusion of unmanipulated "backup" marrow (n = 14). Whereas all patients were approximately 100% Philadelphia chromosome-positive (Ph(+)) before transplantation, 2 patients had complete cytogenetic remissions; 3 patients had fewer than 33% Ph(+) metaphases; and 8 remained 100% Ph(+). One patient's marrow yielded no metaphases, but fluorescent in situ hybridization evaluation approximately 18 months after transplantation revealed approximately 45% bcr/abl(+) cells, suggesting that 6 of 14 patients had originally obtained a major cytogenetic response. Conclusions regarding clinical efficacy of ODN marrow purging cannot be drawn from this small pilot study. Nevertheless, these results lead to the speculation that enhanced delivery of ODN, targeted to critical proteins of short half-life, might lead to the development of more effective nucleic acid drugs and the enhanced clinical utility of these compounds in the future.

Hepatocyte growth factor/scatter factor released during peritonitis is active on mesothelial cells

Peritonitis causes mesothelial detachment that may result in persistent peritoneal denudation and fibrosis. We investigated whether hepatocyte growth factor (HGF), a scatter factor that induces detachment from substrate and fibroblastic transformation of several cell types, is produced during peritonitis and is active on mesothelial cells. We studied 18 patients on peritoneal dialysis, 9 uncomplicated, 9 with peritonitis. HGF was measured in serum, peritoneal fluid, and supernatant of peripheral blood mononuclear cells and peritoneal mononuclear cells. Primary culture of human peritoneal mesothelial cells and the human mesothelial cell line MeT-5A were conditioned with recombinant HGF, serum, and peritoneal fluid. HGF levels were significantly higher in serum and peritoneal fluid of peritonitic than uncomplicated patients. Mononuclear cells of peritonitic patients produced more HGF than cells of uncomplicated patients. Recombinant HGF, serum, and peritoneal fluid of peritonitic patients caused mesothelial cell growth, detachment, transformation from epithelial to fibroblast-like shape, overexpression of vimentin, and synthesis of type I and III collagen. In conclusion, HGF released during peritonitis causes a change in mesothelial cell phenotype and function. HGF may affect the healing process facilitating repair through mesothelial cell growth, but may contribute to peritoneal fibrosis inducing cell detachment with mesothelial denudation and collagen synthesis.

Genome-wide expression changes induced by HTLV-1 Tax: evidence for MLK-3 mixed lineage kinase involvement in Tax-mediated NF-kappaB activation

The Tax protein of human T-lymphotropic virus type 1 (HTLV-1), an oncoprotein that transactivates viral and cellular genes, plays a key role in HTLV-1 replication and pathogenesis. We used cDNA microarrays to examine Tax-mediated transcriptional changes in the human Jurkat T-cell lines JPX-9 and JPX-M which express Tax and Tax-mutant protein, respectively, under the control of an inducible promoter. Approximately 300 of the over 2000 genes examined were differentially expressed in the presence of Tax. These genes were grouped according to their function and are discussed in the context of existing findings in the literature. There was strong agreement between our results and genes previously reported as being Tax-responsive. Genes that were differentially expressed in the presence of Tax included those related to apoptosis, the cell cycle and DNA repair, signaling factors, immune modulators, cytokines and growth factors, and adhesion molecules. Functionally, we provide evidence that one of these genes, the mixed-lineage kinase MLK-3, is involved in Tax-mediated NF-kappa-B signaling. Our current results provide additional insights into Tax-mediated signaling.

Increased hepatocyte growth factor in serum in acute graft-versus-host disease

Hepatocyte growth factor (HGF) was reported to be effective in preventing acute graft-versus-host disease (GVHD) in a murine model. We examined serum HGF concentrations in 38 patients receiving allogeneic bone marrow transplants, and investigated the relationship of serum HGF concentrations to severity of acute GVHD. More HGF was present in sera from patients with than without acute GVHD. Serum HGF correlated significantly with grade of acute GVHD. Furthermore, serum HGF correlated with serum concentrations of C-reactive protein, gamma-glutamyltranspeptidase (GTP), and aspartate aminotransferase (AST). Serum concentrations of HGF in transplanted patients without GVHD were consistently low, while those in patients with acute GVHD increased with exacerbation. We conclude that HGF was produced during induction of the GVH reaction, and probably increased as a physiological response.

Autocrine/paracrine mechanisms in human hematopoiesis

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.

Numerous growth factors, cytokines, and chemokines are secreted by human CD34(+) cells, myeloblasts, erythroblasts, and megakaryoblasts and regulate normal hematopoiesis in an autocrine/paracrine manner

The aim of this study was to explore further the hypothesis that early stages of normal human hematopoiesis might be coregulated by autocrine/paracrine regulatory loops and by cross-talk among early hematopoietic cells. Highly purified normal human CD34(+) cells and ex vivo expanded early colony-forming unit-granulocyte-macrophage (CFU-GM)-derived, burst forming unit-erythroid (BFU-E)-derived, and CFU-megakaryocyte (CFU-Meg)-derived cells were phenotyped for messenger RNA expression and protein secretion of various growth factors, cytokines, and chemokines to determine the biological significance of this secretion. Transcripts were found for numerous growth factors (kit ligand [KL], FLT3 ligand, fibroblast growth factor-2 [FGF-2], vascular endothelial growth factor [VEGF], hepatocyte growth factor [HGF], insulinlike growth factor-1 [IGF-1], and thrombopoietin [TPO]); cytokines (tumor necrosis factor-alpha, Fas ligand, interferon alpha, interleukin 1 [IL-1], and IL-16); and chemokines (macrophage inflammatory protein-1alpha [MIP-1alpha], MIP-1beta, regulated upon activation, normal T cell expressed and secreted [RANTES], monocyte chemotactic protein-3 [MCP-3], MCP-4, IL-8, interferon-inducible protein-10, macrophage-derived chemokine [MDC], and platelet factor-4 [PF-4]) to be expressed by CD34(+) cells. More importantly, the regulatory proteins VEGF, HGF, FGF-2, KL, FLT3 ligand, TPO, IL-16, IGF-1, transforming growth factor-beta1 (TGF-beta1), TGF-beta2, RANTES, MIP-1alpha, MIP-1beta, IL-8, and PF-4 were identified in media conditioned by these cells. Moreover, media conditioned by CD34(+) cells were found to inhibit apoptosis and slightly stimulate the proliferation of other freshly isolated CD34(+) cells; chemo-attract CFU-GM- and CFU-Meg-derived cells as well as other CD34(+) cells; and, finally, stimulate the proliferation of human endothelial cells. It was also demonstrated that these various hematopoietic growth factors, cytokines, and chemokines are expressed and secreted by CFU-GM-, CFU-Meg-, and BFU-E-derived cells. It is concluded that normal human CD34(+) cells and hematopoietic precursors secrete numerous regulatory molecules that form the basis of intercellular cross-talk networks and regulate in an autocrine and/or a paracrine manner the various stages of normal human hematopoiesis.

Expression of the c-met proto-oncogene and its ligand, hepatocyte growth factor, in Hodgkin disease

The receptor for hepatocyte growth factor (HGF) is a transmembrane tyrosine kinase that is encoded by the proto-oncogene c-met. Recently, c-MET was detected in Reed-Sternberg (RS) cells from Epstein-Barr virus-positive (EBV(+)) Hodgkin disease (HD). The c-MET, EBER-1, and LMP-1 expression in 45 lymph node biopsies and 12 bone marrow biopsies obtained from patients with HD was analyzed. In addition, HGF levels in serum samples from 80 healthy individuals and 135 HD patients in different phases of disease. In all 45 lymph node and 12 bone marrow samples examined, RS cells expressed c-MET but not HGF(+). These results were independent of the EBV infection. Interestingly, several HGF(+) dendritic-reticulum cells were found scattered around c-MET(+) RS cells. The mean +/- SEM serum HGF levels in HD patients at diagnosis and at the time of relapse were 1403 +/- 91 (95% confidence interval [CI], 1221-1585) and 1497 +/- 242 pg/mL (95% CI, 977-2017), respectively. HGF values were significantly higher than those of healthy individuals (665 +/- 28 pg/mL; 95% CI, 600-721; and P <.001 for both groups of patients) and of HD patients in remission (616 +/- 49 pg/mL; 95% CI, 517-714; and P <.001 for both groups of patients). A significant correlation was found between serum HGF levels and B symptoms at diagnosis (P =.014). In conclusion, this study indicates that HGF and c-MET constitute an additional signaling pathway between RS cells and the reactive cellular background, thereby affecting adhesion, proliferation, and survival of RS cells. Furthermore, the serum concentration of HGF in HD patients may be a useful tool in monitoring the status of disease.

Hepatocyte growth factor is secreted by osteoblasts and cooperatively permits the survival of haematopoietic progenitors

Human osteoblasts (HOBs) support the growth of human haematopoietic progenitor cells, and support the survival and limited expansion of long-term culture-initiating cells. Using human CD34+ cells and the murine myelomonocytic cell line NFS-60 as targets, we previously found that one component of HOB-derived haematopoietic activity is cell-associated granulocyte colony-stimulating factor (G-CSF). However, antibody failed to neutralize all the activity, suggesting that more than one factor supports haematopoietic cells. In the present investigations, we asked whether the HOB-derived, non-G-CSF secreted activity was as a result of other known growth factors. We found that, among the cytokines expressed by HOBs, only hepatocyte growth factor (HGF) and G-CSF stimulated NFS-60 cell proliferation. HOB cells and osteosarcoma cells secreted biologically active HGF, although the levels varied considerably. Moreover, addition of neutralizing HGF antibody to CD34+ cell/HOB co-cultures resulted in a significant reduction ( approximately 50%) in the ability of the HOBs to support haematopoietic progenitor cells. These results suggest that a major component of osteoblast-derived haematopoietic activity is HGF. Secretion of HGF, in concert with cell-associated cytokines such as G-CSF, may account for the stem cell-stimulating activities of osteogenic cells and, thereby, the unique stem cell-supporting role of the osteoblasts within the bone marrow microenvironment.

Haploinsufficiency of CBFA2 causes familial thrombocytopenia with propensity to develop acute myelogenous leukaemia

Familial platelet disorder with predisposition to acute myelogenous leukaemia (FPD/AML, MIM 601399) is an autosomal dominant disorder characterized by qualitative and quantitative platelet defects, and propensity to develop acute myelogenous leukaemia (AML). Informative recombination events in 6 FPD/AML pedigrees with evidence of linkage to markers on chromosome 21q identified an 880-kb interval containing the disease gene. Mutational analysis of regional candidate genes showed nonsense mutations or intragenic deletion of one allele of the haematopoietic transcription factor CBFA2 (formerly AML1) that co-segregated with the disease in four FPD/AML pedigrees. We identified heterozygous CBFA2 missense mutations that co-segregated with the disease in the remaining two FPD/AML pedigrees at phylogenetically conserved amino acids R166 and R201, respectively. Analysis of bone marrow or peripheral blood cells from affected FPD/AML individuals showed a decrement in megakaryocyte colony formation, demonstrating that CBFA2 dosage affects megakaryopoiesis. Our findings support a model for FPD/AML in which haploinsufficiency of CBFA2 causes an autosomal dominant congenital platelet defect and predisposes to the acquisition of additional mutations that cause leukaemia.

Differences in phosphorylation of the IL-2R associated JAK/STAT proteins between HTLV-I(+), IL-2-independent and IL-2-dependent cell lines and uncultured leukemic cells from patients with adult T-cell lymphoma/leukemia

To determine activation status of the IL-2R-associated (Jak/STAT) pathway in the HTLV-I infected cells, we examined tyrosine phosphorylation of Jak3, STAT3, and STAT5 in several HTLV-I(+) T-cell lines and in uncultured leukemic T cells isolated from patients with adult T-cell lymphoma/leukemia (ATLL). Constitutive basal phosphorylation of Jak3 and, usually, STAT3 and STAT5 was detected in all four IL-2-independent cell lines tested, but in none of the three IL-2-dependent cell lines. Similarly, there was no detectable basal phosphorylation of Jak3 and STAT5 in the leukemic cells from ATLL patients (0/8 and 0/3, respectively). However, stimulation with IL-2 resulted in Jak3 and STAT5 phosphorylation in both leukemic ATLL cells and IL-2-dependent lines. Furthermore, expression of SHP-1 phosphatase which is a negative regulator of cytokine receptor signaling, was lost in most IL-2 independent cell lines (3/4) but not in the leukemic ATLL cells (0/3). Finally, the HTLV-I(+) T-cell lines (313) but not the control, HTLV-I(-) T-cell lines were resistant to rapamycin and its novel analog RAD. We conclude that (1) HTLV-I infection per se does not result in a constitutive phosphorylation of the Jak3, STAT3, and STAT5 proteins; (2) malignant transformation in at least some cases of ATLL does not require the constitutive, but may require IL-2-induced, activation of the IL-2R Jak/STAT pathway; and (3) there are major differences in T-cell immortalization mechanism(s) which appear to involve SHP-1 and target molecules for rapamycin and RAD.

Elevated serum concentrations of hepatocyte growth factor in acute myelocytic leukaemia

Serum concentrations of hepatocyte growth factor (HGF) were measured in 60 patients suffering from acute myelocytic leukaemia (AML). At the time of diagnosis elevated HGF concentrations (> 1.25 ng/ml) were found in 28% of the patients. HGF levels correlated with the presence of disseminated intravascular coagulation (DIC), levels of lysozyme, creatinine, peripheral blood blast counts and lactic dehydrogenase. In the group of patients with high HGF (>1.25 ng/ml) we found a tendency towards an increased early mortality; 41% of them died within 15 d from diagnosis, as opposed to 5% of the patients with normal HGF (log rank test p=0.07). DIC-related bleeding or thrombosis contributed to this early mortality. In responders, HGF levels normalized after treatment. HGF levels are low in neutropenia and neutropenic infections.

The role of hepatocyte growth factor and its receptor c-Met in multiple myeloma and other blood malignancies

The cytokine hepatocyte growth factor (HGF) and its receptor c-Met are a ligand-receptor pair with important functions in a communicative interplay between HGF-producing, mesenchymal cells and c-Met-expressing target cells. HGF is cytoprotective and causes regeneration of parenchyma after tissue damage in several organs. The receptor c-Met was first characterized as an oncogene product being responsible for the transformation of an osteosarcoma cell line. HGF or c-Met is overexpressed in several human cancers, including various carcinomas. Some cells of hematopoietic origin also seem to be capable of c-Met expression, but the precise role of HGF in normal hematopoiesis is yet to be determined. In blood malignancies like acute myelogenous leukemia and, notably, multiple myeloma, HGF is overproduced and has implications for the prognosis of the patients. Biological significance of HGF overexpression in multiple myeloma is discussed and is likely to include effects on bone turnover and angiogenesis.

Role of vascular endothelial growth factor (VEGF) and placenta-derived growth factor (PlGF) in regulating human haemopoietic cell growth

Vascular endothelial growth factor (VEGF) and placental derived growth factor (PlGF) stimulate cell proliferation and differentiation by binding to their specific receptors, Flk-1/KDR and Flt-1 respectively. Flk-1/KDR-deficient murine embryos manifest failure of blood-island formation and vasculogenesis. The aim of this study was to directly evaluate the importance of VEGF, PlGF/Flt-1 and Flk-1/KDR receptor ligand interactions in regulating normal and malignant human haemopoiesis. Addition of VEGF and PlGF failed to enhance survival or cloning efficiency of human haemopoietic progenitors isolated from adult bone marrows, fetal livers or cord blood samples. This finding may be explained by the apparent absence of mRNA encoding Flt-1 and Flk-1/KDR receptors on stem cell rich CD34+ c-kit-R+ Rh123(low) cells. Further studies revealed that Fit-1 R mRNA, but not Flk-1/KDR mRNA was first detectable in the more mature cells isolated from haemopoietic colonies. Accordingly, VEGF receptors are either absent, or expressed at very low level, on human haemopoietic stem/progenitor cells. Of interest, normal and malignant human haemopoietic cells appeared to secrete VEGF protein. However, in contrast to normal haemopoietic progenitors, VEGF co-stimulated HEL cell proliferation as well as CFU-GM colony formation from approximately 15% of the chronic myeloid leukaemia (CML) and acute myeloid leukaemia (AML) patients studied. Therefore, although VEGF appeared to have minimal effects on normal haemopoietic cell growth it would appear to drive malignant haemopoietic cell proliferation to some degree. Of more importance, however, we speculate that VEGF may play an very important role in leukaemogenesis by stimulating growth of vascular endothelium, thereby providing a sufficient blood supply to feed the growing haematological tumour.