CD34+++ Stem/Progenitor Cells Purified from Cryopreserved Normal Cord Blood can be Transduced with High Efficiency by a Retroviral Vector and Expanded Ex Vivo with Stable Integration and Expression of Fanconi Anemia Complementation C Gene

A future possibility for treatment of genetic diseases may be gene therapy using autologous cord blood (CB) stem/progenitor cells. This might require cryopreservation of CB stem/progenitor cells prior to purification, gene transduction, and ex vivo expansion of cells. To address this possibility, nonadherent low density T-lymphocyte depleted (NALT-) cells from fresh or cryopreserved cord blood were sorted for CD34+++ phenotype, transduced with a recombinant retroviral vector encoding Fanconi anemia complementation C (FACC) gene, and cells expanded ex vivo in suspension culture for 7 days with growth factors. The results demonstrate: 1) high recovery of viable cells after thawing; 2) high efficiency purification of CD34+++ cells from NALT- cells prior to and after cryopreservation; 3) high degree of expansion of nucleated cells and immature progenitors from CD34+++ cells before and after cryopreservation; 4) efficient transduction with stable integration and expression of newly introduced genes in cryopreserved and then sorted stem/progenitor cells, as detected prior to and after ex vivo expansion; and 5) high efficiency transduction of single isolated CD34+++ cells obtained from cryopreserved NALT- CB. This information should be of value for future studies evaluating the use of cryopreserved cord blood for gene transfer/gene therapy.

ID: 95: IL-33/ST2 TRIGGERING OF IL-9–SECRETING T CELLS: FROM PROTEOMICS TO THERAPEUTICS

As one of the most validated immunotherapies to date, allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative option for high-risk hematological malignancies, particularly acute myeloid leukemia (AML). The immunotherapeutic activity of allo-HCT is known as the graft-vs-leukemia (GVL) activity. However, GVL activity is often accompanied by T-cell reactivity to allo-antigens in normal host tissues, which leads to graft-versus-host disease (GVHD), another major cause of death after HCT. Therefore, there is a great unmet need to improve the current process of allo-HCT through increasing the GVL activity and decreasing GVHD. We have shown that an elevated plasma level of soluble (s)ST2 in HCT patients is a risk factor for severe GVHD. ST2 blockade reduces sST2-producing T cells while maintaining protective membrane (m)ST2-expressing T cells such as type 2 T cells and regulatory T cells during aGVHD. A novel IL-9 producing T helper subset, Th9, expresses mST2. Furthermore, Th9 cells and IL-9 producing CD8 cytotoxic (Tc9) cells have higher antitumor activity than Th1 and Tc1 cells in melanoma models. Interestingly, we found that the addition of IL-33 during T9 differentiation (T9IL-33) increased expression of mST2 and PU.1, a transcription factor that promotes IL-9 production in both CD4 and CD8 T cells. Adoptive transfer of T9IL-33 cells with bone marrow cells in a murine model of HCT resulted in less severe GVHD compared to transfer of T9IL-33 cells generated from ST2−/− or IL-9−/− T cells. Furthermore, cytolytic molecules implicated in anti-leukemic activity (granzyme B and perforin) were upregulated in WT T9IL-33 cells while ST2−/− T9IL-33 cells did not. WT T9IL-33 cells also exhibited higher anti-leukemic activity when cultured with a retrovirally transduced MLL-AF9 leukemic cells in comparison to ST2−/− T9IL-33 in in vitro cytolytic assays. In vivo GVL experiments with MLL-AF9 AML and adoptive transfer of T9IL-33 cells resulted in increased survival compared to syngeneic mice, allo-HCT mice transferred with T1 cells, or T9 cells or T9IL-33 cells generated from ST2−/− or IL-9−/− T cells. Human T9 cells are poorly studied. Here we demonstrate that IL-33 has the same impact on human T cells through enhancing IL-9 and Granzyme B production compared to T9 cells as well as demonstrated higher in vitro anti-leukemic cytolytic activity when incubated with MOLM14, an aggressive AML tumor cell line expressing FLT3/ITD mutations. Importantly, CD8α expression was upregulated in WT T9IL-33 (both CD4 and CD8) cells in comparison to ST2−/− T9IL-33 cells, and CD8α blockade with neutralizing antibody during allogeneic specific T9IL-33 differentiation reduced cytotoxicity of both murine T9IL-33, and human T9IL-33 cells as compared to the cell blocked with isotype control, suggesting that CD8α was associated with MHC-restricted cytolytic activity in T9IL-33 cells. Altogether, our observations demonstrated that adoptive transfer of T9IL-33 cells represents a promising cellular therapy following HCT.

Small-molecule inhibitors targeting the DNA-binding domain of STAT3 suppress tumor growth, metastasis and STAT3 target gene expression in vivo

Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in malignant tumors and has important roles in multiple aspects of cancer aggressiveness. Thus targeting STAT3 promises to be an attractive strategy for treatment of advanced metastatic tumors. Although many STAT3 inhibitors targeting the SH2 domain have been reported, few have moved into clinical trials. Targeting the DNA-binding domain (DBD) of STAT3, however, has been avoided due to its 'undruggable' nature and potentially limited selectivity. In a previous study, we reported an improved in silico approach targeting the DBD of STAT3 that resulted in a small-molecule STAT3 inhibitor (inS3-54). Further studies, however, showed that inS3-54 has off-target effect although it is selective to STAT3 over STAT1. In this study, we describe an extensive structure and activity-guided hit optimization and mechanistic characterization effort, which led to identification of an improved lead compound (inS3-54A18) with increased specificity and pharmacological properties. InS3-54A18 not only binds directly to the DBD and inhibits the DNA-binding activity of STAT3 both in vitro and in situ but also effectively inhibits the constitutive and interleukin-6-stimulated expression of STAT3 downstream target genes. InS3-54A18 is completely soluble in an oral formulation and effectively inhibits lung xenograft tumor growth and metastasis with little adverse effect on animals. Thus inS3-54A18 may serve as a potential candidate for further development as anticancer therapeutics targeting the DBD of human STAT3 and DBD of transcription factors may not be 'undruggable' as previously thought.

Insights into the biology of cord blood stem/progenitor cells

OBJECTIVES

To review information on cord blood banking and transplantation with respect to the author's studies, and in context of this field of investigation.

RESULTS

Cord blood transplantation has been successfully used to treat a number of malignant and non-malignant disorders. However, this technique is still associated with limited numbers of cells for transplantation, and with delayed engraftment of neutrophils and platelets. The field of cord blood transplantation will benefit from enhanced and mechanistically based information on haematopoietic stem cell function and potential means to enhance its effectiveness are reviewed. This includes notions concerning possibility of retrieving more cells from the placenta and cord blood, to expand haematopoietic stem cells ex vivo and to increase efficiency of homing and engraftment of these cells. Also discussed are cryopreservation and long-term storage of cord blood haematopoietic and progenitor cells, and new laboratory findings and animal studies for non-haematopoietic uses of cord blood.

Experimental basis of cord blood transplantation

Efforts are needed to enhance the efficacy of cord blood (CB) transplantation. Laboratory information set the stage for the first and subsequent CB transplants, and will be instrumental in continuing to advance the field. This paper offers a brief understanding of the current state of hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC) biology, a look back at laboratory studies leading to the first CB transplants, and a discussion of the possible means to enhance CB transplantation. Results show that physical recovery of greater numbers of HPCs is possible after CB is collected by perfusing the placenta, but how realistic this procedure is for collection of CB to be banked is open to question. We also show that the chemokine stromal cell-derived factor-1/CXCL12 can enhance the ex vivo expansion of CB HPCs beyond that of the combination of SCF, Flt3-ligand and TPO. Advances in cytokine and stromal cell biology, and in intracellular signals mediating the effects of cytokines/stromal cells should be considered in the context of future efforts to enhance functional activities of donor CB HSCs and HPCs and the microenvironmental niche of the recipient, which is required for acceptance and nurturing these HSCs/HPCs.

Negative regulation of chemokine receptor CXCR4 by tumor suppressor p53 in breast cancer cells: implications of p53 mutation or isoform expression on breast cancer cell invasion

Chemokine receptor CXCR4 and its ligand CXCL12 are suggested to be involved in migration, invasion and metastasis of breast cancer cells. Mutation of the tumor suppressor gene p53 in breast cancer is associated with metastasis and aggressive clinical phenotype. In this report, we demonstrate that wild type but not the dominant-negative mutant (V143A) or cancer-specific mutants (R175H or R280K) of p53 repress CXCR4 expression. Recently described cancer-specific p53 isoform, Delta133p53, also failed to repress CXCR4 promoter activity. Short-interfering RNA-mediated depletion of p53 increased endogenous CXCR4 expression in MCF-7 breast cancer cells that contain wild-type p53. Basal CXCR4 promoter activity in HCT116 colon carcinoma cells deleted of p53 [HCT116(p53KO)] was 10-fold higher compared to that in parental HCT116 cells with functional wild-type p53. Deletion analysis of CXCR4 promoter identified a seven-base pair p53-repressor element homologous to cyclic AMP/AP-1 response (CRE/AP-1) element. Electrophoretic mobility shift and chromatin immunoprecipitation assays revealed binding of ATF-1 and cJun to the CRE/AP-1 element. The p53 rescue drug PRIMA-1 reduced CXCR4 mRNA and cell surface expression in MDA-MB-231 cells, which express R280K mutant p53. CP-31398, another p53 rescue drug, similarly reduced cell surface levels of CXCR4. PRIMA-1-mediated decrease in CXCR4 expression correlated with reduced invasion of MDA-MB-231 cells through matrigel. These results suggest a mechanism for elevated CXCR4 expression and metastasis of breast cancers with p53 mutations or isoform expression. We propose that p53 rescue drugs either alone or in combination with chemotherapeutic drugs may be effective in reducing CXCR4-mediated metastasis.

Biology of cord blood cells and future prospects for enhanced clinical benefit

Cord blood (CB) has served as a clinically beneficial source of hematopoietic stem (HSC) and progenitor (HPC) cells for transplantation and correction of a large number of malignant and non-malignant disorders. The capacity of CB to perform these functions is intimately related to the quality and quantity of HSC and HPC present in CB. This review covers the biology of HSC and HPC, efforts to expand these cells ex vivo for enhanced clinical utility that has thus far not been very successful, and recent studies on attempts to enhance the homing and engrafting capability of HSC as an alternative means for more effective use of the limited numbers of CB cells collected. This review also highlights the presence in CB of mesenchymal stem cells, unrestricted somatic stem cells, endothelial progenitor cells and immune cells. The presence and biology of these non-HSC/HPC may open up future possibilities for additional clinical benefit of CB, a product considered mainly for discard before its clinical transplantation potential was realized in the late 1980s.

SDF-1α/CXCL12 enhances retroviral-mediated gene transfer into immature subsets of human and murine hematopoietic progenitor cells

Genetic modification of hematopoietic stem and progenitor cells has the potential to treat diseases affecting blood cells. Oncoretroviral vectors have been used for gene therapy; however, clinical success has been limited in part by low gene transfer efficiencies. We found that the presence of stromal-derived factor 1 (SDF-1alpha)/CXCL12 during retroviral transduction significantly enhanced, in a dose-dependent fashion, gene transfer into immature subsets of high proliferative human and murine hematopoietic progenitor cells. Murine mononuclear bone marrow cells and purified c-Kit(+)Lin(-) bone marrow cells were prestimulated and transduced with the bicistronic retroviral vector MIEG3 on Retronectin-coated surfaces in the presence and absence of SDF-1. SDF-1 enhanced gene transduction of murine bone marrow and c-Kit(+)Lin(-) cells by 35 and 29%, respectively. Moreover, SDF-1 enhanced transduction of progenitors in these populations by 121 and 107%, respectively. SDF-1 also enhanced transduction of human immature subsets of high proliferative progenitors present in either nonadherent mononuclear or CD34(+) umbilical cord blood cells. Transduction of hematopoietic progenitors was further increased by preloading Retronectin-coated plates with retrovirus using low-speed centrifugation followed by increasing cell-virus interactions through brief centrifugation during the transduction procedure. These results may be of clinical relevance.

Role of the CC chemokine receptor 9/TECK interaction in apoptosis

Chemokine receptors are members of the G protein coupled receptor (GPCR) supergene family whose expression is highly restricted to hematopoietic cells. Although the primary role of chemokine and chemokine receptor interaction is believed to be regulation of chemotaxis of leukocytes, subsequent information clearly suggests that multiple immune regulatory functions are attributed to chemokine receptor signaling. We recently showed that activation of the CC chemokine 9 receptor (CCR9), a thymus-specific chemokine receptor, led to potent cFLIP(L)-independent resistance to cycloheximide-induced apoptosis and modest resistance to Fas-mediated apoptosis possibly via activation of multiple signaling components involving Akt and glycogen synthase kinase 3beta. The fact that these two apoptotic signals involve activation of similar arrays of death execution machinery such as caspase-8, caspase-9, or caspase-3, suggests that chemokine receptor signaling may provide a wide range of antiapoptotic activities to hematopoietic cells under certain biological conditions. GPCR is a large family of cell surface receptors, many of which are critically involved in hormonal and behavioral control. Recent observations also suggest that GPCR signaling plays a pivotal role in immune cell activation. Heterotrimeric G protein is an integral part of GPCR signaling. Thus, dissection of signaling components involved in the CCR9-mediated antiapoptosis could be a framework for cell survival mechanisms and may provide options for therapeutic interventions for neurdegenerative diseases or T cell malfunctioning.

Steel factor regulates cell cycle asymmetry

Asymmetric segregation of cell-fate determinants during mitosis (spatial asymmetry) is an essential mechanism by which stem cells are maintained while simultaneously giving rise to differentiated progenitors that ultimately produce all the specialized cells in the hematopoietic system. Temporal cell cycle asymmetry and heterogeneity are attributes of cell proliferation that are also essential for maintaining tissue organization. Hematopoietic stem cells (HSCs) are regulated by a complex network of cytokines, some of which have very specific effects, while others have very broad ranging effects on HSCs. Some cytokines, like steel factor (SLF), are known to synergize with other cytokines to produce rapid expansion of progenitor cells. Using the human growth factor-dependent MO7e cell line as a model for synergistic proliferation, we present evidence that links proliferation asymmetry to SLF synergy with GM-CSF, and suggests that temporal asymmetry and cell cycle heterogeneity can be regulated by SLF in vitro. We also show that CDK-inhibitor and cell cycle regulator, p27kip-1, may be involved in this temporal asymmetry regulation. We propose that SLF/GM-CSF synergy is, in part, due to a shift in proliferation pattern from a heterogeneous and asymmetric one to a more synchronous and symmetric pattern, thus contributing dramatically to the rapid expansion that accompanies SLF synergy observed in MO7e cells. This kinetic model of asymmetry is consistent with recent evidence showing that even though SLF synergy results in a strong proliferative signal, it does not increase primary HSC self-renewal, which is believed to be highly dependent on asymmetric divisions. The factor-dependent MO7e/SCF- synergy/asymmetry model described here may therefore be useful for studies of the effects of various cytokines on cell cycle asymmetry.

Cutting edge: IL-17F, a novel cytokine selectively expressed in activated T cells and monocytes, regulates angiogenesis and endothelial cell cytokine production

A novel secreted cytokine, termed IL-17F, was cloned using nested RACE PCR. This cytokine bears homology to IL-17. IL-17F was expressed only in activated CD4(+) T cells and activated monocytes. Recombinant human IL-17F did not stimulate the proliferation of hematopoietic progenitors or the migration of mature leukocytes. However, it markedly inhibited the angiogenesis of human endothelial cells and induced endothelial cells to produce IL-2, TGF-beta, and monocyte chemoattractant protein-1.

Blocking of c-FLIP(L)--independent cycloheximide-induced apoptosis or Fas-mediated apoptosis by the CC chemokine receptor 9/TECK interaction

Chemokines play a pivotal role in regulating leukocyte migration as well as other biological functions. CC chemokine receptor 9 (CCR9) is a specific receptor for thymus-expressed CC chemokine (TECK). It is shown here that engagement of CCR9 with TECK leads to phosphorylation of Akt (protein kinase B), mitogen-activated protein kinases (MAPKs), glycogen synthase kinase--3 beta (GSK-3 beta), and a forkhead transcription factor, FKHR, in a human T-cell line, MOLT4, that naturally expresses CCR9. By means of chemical inhibitors, it is shown that phosphoinositide-3 kinase (PI-3 kinase), but not MAPK, is required for CCR9-mediated chemotaxis. Akt, GSK-3 beta, FKHR, and MAPK have been previously implicated in cell survival signals in response to an array of death stimuli. When MOLT4 cells, which expressed Fas as well as CXCR4, were stimulated with cycloheximide (CHX), an agonistic anti-Fas antibody, or a combination of these, the cells rapidly underwent apoptosis. However, costimulation of MOLT4 cells with TECK or stromal derived factor--1 significantly blocked CHX-mediated apoptosis, whereas stimulation only with TECK partially blocked Fas-mediated apoptosis. Concomitant with this blocking, cleavage of poly (adenosine 5'-diphosphate--ribose) polymerase and activation of caspase 3 were significantly attenuated, but the expression level of FLICE inhibitory protein c-FLIP(L), which had been shown to be regulated by CHX, was unchanged. This demonstrates that activation of CCR9 leads to phosphorylation of GSK-3 beta and FKHR and provides a cell survival signal to the receptor expressing cells against CHX. It also suggests the existence of a novel pathway leading to CHX-induced apoptosis independently of c-FLIP(L). (Blood. 2001;98:925-933)

Therapeutic potential of 4-1BB (CD137) as a regulator for effector CD8(+) T cells

A fundamental problem of antitumor immunity is tumor-induced immunosuppression. Tumor cells often down-regulate expression of co-stimulatory molecules, tumor antigens, and major histocompatibility complex (MHC) molecules on tumor cells, secrete immunosuppressive substance such as transforming growth factor-beta (TGF-beta) or interleukin-4 (IL-4), and induce apoptosis of effector T cells to escape surveillance. A major goal of antitumor or antivirus immunotherapy is to generate long-lived protective T cells that enable killing of target cells. In this review, we discuss the importance of 4-1BB for development or survival of functionally active effector CD8(+) T cells against tumors, virus infection, and allogeneic immune responses and for potential therapeutic application.

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.

Mzf1 controls cell proliferation and tumorigenesis

MZF1 is a transcription factor belonging to the Krüppel family of zinc finger proteins, expressed in totipotent hemopoietic cells as well as in myeloid progenitors. Here we have inactivated Mzfi1 by gene targeting. Mzf1(-/-) mice develop lethal neoplasias characterized by the infiltration and complete disruption of the liver architecture by a monomorphic population of cells of myeloid origin reminiscent of human chloromas. Mzf1 inactivation results in a striking increase of the autonomous cell proliferation and of the ability of Mzf1(-/-) hemopoietic progenitors to sustain long-term hemopoiesis. These findings demonstrate that Mzf1 can act as a tumor/growth suppressor in the hemopoietic compartment.

Chemokine regulation of hematopoiesis and the involvement of pertussis toxin-sensitive G alpha i proteins

Chemokines have been implicated in regulation of various aspects of hematopoiesis, including negative regulation of the proliferation of immature subsets of myeloid progenitor cells (MPCs), chemotaxis of MPCs, and survival enhancement of MPCs after delayed growth factor addition. Since chemokine receptors are seven-transmembrane-spanning G-protein-linked receptors and the chemotactic effect in vitro of the CXC chemokine SDF-1 is pertussis toxin (PT)-sensitive, implying the involvement of G alpha i proteins as mediators of SDF-1-induced chemotaxis, we evaluated the effects of PT on other chemokine actions influencing MPCs. While the in vitro survival-enhancing effects of SDF-1 on GM-CSF and steel factor-dependent mouse bone marrow granulocyte macrophage progenitors (CFU-GM) were pertussis toxin-sensitive, the suppressive effects of the CC chemokine MIP-1 alpha and the CXC chemokine IL-8 on colony formation by GM-CSF and steel factor-sensitive CFU-GM were insensitive to pertussis toxin. These results suggest that not all chemokine-mediated effects on MPCs are necessarily mediated through pertussis toxin-sensitive G alpha i proteins.

Synergistic activation of RSK correlates with c-fos induction in MO7e cells stimulated with GM-CSF plus Steel factor

Steel factor (SLF) plus GM-CSF induces proliferative synergy in factor-dependent cell line MO7e and hematopoietic progenitor cells. We previously reported ERK1/2 involvement in this synergy, but its downstream signaling molecules are not defined. Here, we investigated activation of the 90-kDa ribosomal S6 kinase (RSK) proteins by measuring the phosphorylation status and in vitro kinase activity in MO7e cells. Both GM-CSF and SLF induced activation of RSK, and the combined stimulation with these two cytokines induced synergistic and persistent activation of RSK. RSK activity was reduced by PI3 kinase inhibitor LY294002 or MEK1 inhibitor PD98059, suggesting that the ERK as well as the PI3 kinase pathways are involved in regulation of RSK activity. Sensitivities of RSK activity to inhibitory drugs correlated well with those of c-fos gene induction. Taken together, synergistic activation of RSK may contribute, at least in part, to the synergistic induction of c-fos after combined stimulation with GM-CSF plus SLF.

The interphase microtubule damage checkpoint defines an S-phase commitment point and does not require p21(waf-1)

Cell cycle checkpoints ensure orderly progression of events during cell division. A microtubule damage (MTD)-induced checkpoint has been described in G(1) phase of the cell cycle (G(1)MTC) for which little is known. The present study shows that the G(1)MTC is intact in activated T lymphocytes from mice with the p21(waf-1) gene deleted. However, p21(waf-1) gene deletion does affect the ratio of cells that arrest at the G(1)MTC and the spindle checkpoint after MTD. The G(1)MTC arrests T lymphocytes in G(1) prior to cdc2 up-regulation and prior to G(1) arrest by p21(waf-1). Once cells have progressed past the G(1)MTC, they are committed to chromosome replication and metaphase progression, even with extreme MTD. The G(1)MTC is also present in a human myeloid cell line deficient in p21(waf-1) gene expression. The p21-independent G(1)MTC may be important in cellular responses to MTD such as those induced by drugs used to treat cancer.

Introduction of human erythropoietin receptor complementary DNA by retrovirus-mediated gene transfer into murine embryonic stem cells enhances erythropoiesis in developing embryoid bodies

To evaluate the role of the erythropoietin (Epo) receptor (R) in erythropoiesis in more primitive stem cells, we assessed the influence of retrovirus-mediated gene transfer of human (h) EpoR complementary DNA (cDNA) into murine embryonic stem (ES) cells on erythroid differentiation of these cells. The hEpoR cDNA was efficiently transduced into ES cells, forming hEpoR that stably expressed ES (ES-hEpoR) cells. Expression of hEpoR cDNA was confirmed in ES-hEpoR cells by reverse transcriptase-polymerase chain reaction and Northern blot analysis. Colony assays demonstrated that definitive erythroid and primitive erythroid colonies were significantly increased from ES-hEpoR cells, when compared with mock virus-transduced ES (ES-Neo) cells, during the time course of differentiation induced by withdrawal of leukemia inhibitory factor, in either the presence or the absence of Epo. Multipotential colony-forming units (CFU-Mix) were also increased in ES-hEpoR cells at different stages of differentiation, but no changes were detected for CFU-granulocyte-macrophage colonies (CFU-GM). Time course studies by Northern blot analysis demonstrated elevated levels of expression of beta-H1 and beta-Major globin genes in embryoid bodies derived from ES-hEpoR cells stimulated with Epo, when compared with similar expression from ES-Neo cells. Expression of the GATA-1 gene was enhanced in ES-hEpoR cells, when compared with ES-Neo cells, beginning immediately after initiation of the cultures until 8 days of differentiation. These data indicate that primitive and definitive erythropoiesis in differentiating embryoid bodies can be enhanced by retrovirus-mediated gene transfer of an hEpoR gene.

Human recombinant interferon-inducible protein-10: intact disulfide bridges are not required for inhibition of hematopoietic progenitors and chemotaxis of T lymphocytes and monocytes

Human recombinant interferon-inducible protein-10 (rIP-10), a C-X-C chemokine, inhibits proliferation of human hematopoietic progenitors responsive to co-stimulation by recombinant steel factor (rSLF), is chemotactic for human monocytes and T-lymphocytes, and promotes T-lymphocyte adhesion to endothelial cells. Because chemokines have four conserved cysteines forming two intramolecular disulfide bridges, we decided to investigate their contribution in the biological activity of rIP-10. Since amino acid residues 22-98 of the sequence predicted by the cDNA constitute the naturally occurring IP-10, they were cloned after an initiating methionine into expression vector pET-3d. Subsequently rIP-10 was purified by enzymatic cell lysis, solubilization of refractile bodies with guanidine hydrochloride, renaturation by dialysis against dilute acetic acid, and sequential ion-exchange and reverse-phase high-performance liquid chromatography. Purified rIP-10 was reduced with 20 mM dithiothreitol, and chemically modified with 100 mM iodoacetamide (IAA), or S-methyl-methanethiosulfonate (MMTS), or N-methylmaleimide (NMM). Radiolabeling experiments demonstrated that 95% of the rIP-10 thiols were modified, and this was confirmed with SDS-PAGE. The biological activity of modified rIP-10 was determined in vitro by inhibition of rSLF-responsive human bone marrow hematopoietic progenitor proliferation and by chemotaxis assays using human T-lymphocytes and monocytes. In both assay systems, the biological activity was evident at rIP-10 concentrations of 20-100 ng/ml. The activity was preserved after modification of rIP-10 by IAA or MMTS, but was abolished after modification by NMM. We conclude that disulfide bridges are not essential for the biological activity of rIP-10.

Transcriptional and ERK1/2-dependent synergistic upregulation of p21(cip1/waf1) associated with steel factor synergy in MO7e

Steel factor (SLF) plus GM-CSF induces proliferative synergy in myeloid progenitors and factor-dependent cell line MO7e. We previously reported that the protein level of cyclin-dependent kinase inhibitor p21(cip1/waf1) (p21) increased synergistically when MO7e cells were stimulated with SLF plus GM-CSF and that p21 induction was required for SLF synergistic responses. Here we show that this p21 induction is regulated at the transcriptional level. Based on use of a multiprobe RNase protection assay, the synergistic increase of p21 mRNA was unique among many cell cycle regulators. While STAT5A and 5B were activated after stimulation with GM-CSF alone or SLF plus GM-CSF, there was no difference in activation between the groups. p44/42 MAP kinase (ERK1/2) was synergistically activated by SLF plus GM-CSF, but SAPK/JNK and p38 MAP kinase were not. Synergistic induction of p21 was significantly decreased with a MEK1 inhibitor, suggesting that the ERK1/2 pathway is involved in the synergistic increase of p21 after GM-CSF plus SLF stimulation.

Current status of cord blood banking and transplantation in the United States and Europe

Cord blood (CB) transplantation has expanded the ability of the transplantation community to meet the growing needs of their patients. Clinical data over the last decade show promising results in CB transplantation using blood from related as well as unrelated donors. Basic science continues to look for ways to expand the quality and quantity of CB. CB banks are now established around the world, with major efforts to standardize banking to facilitate regulation, collection, processing, and distribution as a way of providing the highest-quality CB for patient use. This review article discusses the current status of CB transplantation and banking in the United States and Europe.

An expansion phase precedes terminal erythroid differentiation of hematopoietic progenitor cells from cord blood in vitro and is associated with up-regulation of cyclin E and cyclin-dependent kinase 2

The dynamics of cell cycle regulation were investigated during in vitro erythroid proliferation and differentiation of CD34(+) cord blood cells. An unusual cell cycle profile with a majority of cells in S phase (70.2%) and minority of cells in G1 phase (27.4%) was observed in burst-forming unit-erythrocytes (BFU-E)-derived erythroblasts from a 7-day culture of CD34(+) cells stimulated with interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), Steel factor, and Epo. Terminal erythroid differentiation was accompanied by a rapid increase of G0/G1 phase cells. Expression of cyclin E and cyclin-dependent kinase 2 (cdk2) correlated with the proportion of S phase cells. Cyclin D3 was moderately up-regulated during the proliferation phase, and both cyclin E and D3 were rapidly down-regulated during terminal differentiation. This suggests that the high proliferation potential of erythroblasts is associated with temporal up-regulation of cyclin E and cdk2. (Blood. 2000;96:3985-3987)

Co-transduction of cDNAs for c-kit and steel factor into single CD34+ cord blood cells further enhances the growth of erythroid and multipotential progenitors

Previous studies have demonstrated that the c-kit encoded tyrosine kinase receptor and its ligand, steel factor (SLF), are critical for normal blood cell development. We have reported that transduction of the c-kit gene into single hematopoietic progenitor cells (HPC), CD34(+++) cells, from cord blood (CB) enhances erythroid colony formation via a SLF-dependent mechanism. We therefore decided to evaluate the impact on cell proliferation of co-transducing c-kit and SLF cDNAs into these cells. CD34(+++) cells were sorted as a population or as 1 cell/well for cells expressing the highest levels of CD34 and different levels of c-kit. Cells were then prestimulated with granulocyte macrophage (GM)-colony stimulating factor (CSF), interleukin (IL)-3, IL-6, erythropoietin (Epo) in the presence and absence of various concentrations of SLF. Cells were then transduced with SLF and/or c-kit cDNAs, and then assayed for colony formation with the same cytokine combination. At a single cell level, co-transduction with c-kit and SLF genes significantly enhanced colony formation compared with individual gene transduction, especially by erythroid and multipotential progenitors that responded to stimulation by added cytokines. Little or no growth was seen with the c-kit- and/or SLF-transduced cells without addition of cytokines. The degree of enhancement effected by co-transduction inversely correlated with the degree of expression of c-kit protein before transduction. Optimal enhancing effects were noted in CD34(+++) kit(Lo/-) cells co-transduced with both c-kit and SLF cDNAs. Reverse transcriptase-polymerase chain (RT-PCR) analysis of SLF mRNA expression in CD34(+++) cells and enzyme-linked immunoadsorbent assay (ELISA) measurement of secreted SLF protein demonstrated that the transduced SLF cDNA was expressed and soluble SLF was released in medium cultured with SLF gene transduced MACS-separated CD34(+) cells in the presence, but not in the absence, of IL-3, GM-CSF, IL-6, and Epo. These results demonstrate the enhancement of the proliferation of growth factor responsive HPC that express transduced c-kit and SLF genes.

Comparative effects of retroviral-mediated gene transfer into primary human stromal cells of Flt3-ligand, interleukin 3 and GM-CSF on production of cord blood progenitor cells in long-term culture

The effects of different cytokines on growth of human cord blood CD34 cells was studied by performing long-term culture (LTC) with primary human stromal cells transduced with genes for either Flt3-ligand (L) (human transmembrane, murine soluble or murine membrane-bound forms), human interleukin 3 (IL-3) or human GM-CSF. Molecular analysis of genomic DNA from transduced stromal cells using neo-specific polymerase chain reaction demonstrated gene transfer of G418-selected stromal cell populations. Enzyme-linked immunosorbent assay and biological assays of conditioned media from transduced stromal cells indicated expression and release of soluble cytokines. Numbers of both immature and more mature progenitors (colony-forming unit-granulocyte, erythroid, macrophage, megakaryocyte; CFU-GEMM, BFU-E, CFU-GM) were increased threefold compared to control in the Flt3-L (transmembrane) LTC throughout five weeks of culture. IL-3 and GM-CSF feeders increased progenitor cell output also, but these effects were significantly lower than Flt3-L feeders. The two Flt3-L isoform engineered feeders, Ex6 (soluble isoform) and 5H (membrane-bound isoform), showed a decreased effect compared to the transmembrane Flt3-L feeders and, in particular, Ex6 feeders were similar to control feeders and 5H feeders were comparable to Flt3-L feeders only in the first two weeks of LTC. These results were apparent also by limiting dilution assays that showed a higher frequency of pre-CFU in the transmembrane Flt3-L feeders compared to control and the other cytokine feeders. Exogenous addition of soluble growth factors to suspension cultures without feeder layers, while superior to stromal feeders for short-term expansion of early progenitors, were inferior to the long-term maintenance/output on stromal feeders. Pre-CFU analysis supported these data. These results may be of some significance to understanding the actions of Flt3-L on blood cell production.

Analysis of engraftment, graft-versus-host disease, and immune recovery following unrelated donor cord blood transplantation

Unrelated cord blood (UCB) is being used as a source of alternative hematopoietic stem cells for transplantation with increasing frequency. From November 1994 to February 1999, 30 UCB transplant procedures were performed for both malignant and nonmalignant diseases in 27 children, aged 0.4 to 17.1 years. Patients received either HLA-matched (n = 3) or 1- or 2-antigen-mismatched (n = 27) UCB following 1 of 2 standardized preparative and graft-versus-host disease regimens (hyperfractionated total body irradiation, cyclophosphamide, and antithymocyte globulin [ATG] with cyclosporine A and methotrexate; or busulfan, melphalan, and ATG with cyclosporine A and prednisone). The median time to neutrophil and platelet engraftment was 27 days (12-60 days) and 75 days (33-158 days) posttransplantation, respectively. No correlation was noted between neutrophil and platelet engraftment and nucleated cells per kilogram, CD34(+) cells per kilogram infused, or cytomegalovirus status of recipient. The cumulative probability of acute grade 2 or greater graft-versus-host disease (GVHD) was 37.2%, and of grade 3 or greater GVHD was 8.8%. No patients developed chronic GVHD. CD4, CD19, and natural killer cell recovery was achieved at a median of 12, 6, and 2 months, respectively. CD8 recovery was delayed at a median of 9 months. Normal mitogen response was achieved at 6 to 9 months. The probability of survival, disease-free survival, and event-free survival at 1 year was 52.3% (34.1%-70.5%), 54.7% (34.5%-74.9 %) and 49.6% (29.9%-69.4%), respectively. This series of 30 UCB transplants suggests that although CD8 cell recovery is delayed, the pattern of immune reconstitution with UCB is similar to that reported for other stem cell sources. (Blood. 2000;96:2703-2711)

Flt3 ligand induces tyrosine phosphorylation of gab1 and gab2 and their association with shp-2, grb2, and PI3 kinase

The receptor tyrosine kinase Flt3 has been shown to play an important role in proliferation, differentiation, and survival of hematopoietic stem and progenitor cells. Although some postreceptor signaling events of Flt3 have been characterized, the involvement of Gab family proteins in Flt3 signaling is not known. In this study, we show that both Gab1 and Gab2 are rapidly tyrosine phosphorylated after Flt3 ligand stimulation of Flt3 ligand-responsive cells. They interact with tyrosine-phosphorylated Shp-2, p85, Grb2, and Shc. The results suggest that Gab proteins are engaged in Flt3 signaling to mediate downstream activation of Shp-2 and PI3 kinase pathways and possibly the Ras/Raf/MAPK pathway.

Differentially expressed genes during in vitro differentiation of murine embryonic stem cells transduced with a human erythropoietin receptor cDNA

Our previous study demonstrated that transduction of murine embryonic stem (ES) cells with a human erythropoietin (Epo) receptor (R) cDNA resulted in enhanced erythropoiesis in developing embryonic bodies (EBs). To address possible mechanisms of gene regulation, we compared gene expression between hEpoR cDNA-transduced ES (ES-hEpoR) cells and parental ES cells during in vitro differentiation induced by withdrawal of leukemia inhibitory factor (LIF) and cultured in the absence of Epo using differential display reverse transcriptase-polymerase chain reaction (DDRT-PCR). A total of 48 differentially expressed cDNA fragments were found; 12 were sequenced and five were confirmed by Northern blot analysis to be up- or down-regulated in ES-hEpoR cells during differentiation compared to parental ES cells. In a GenBank search of the five putatively regulated cDNA fragments, two fragments shared high sequence homology to two known genes: the Surf-6 gene and the gene for calcyclin binding protein. Northern blot analysis demonstrated that 2.5-kb and 0.3-kb transcripts of the Surf-6 gene were expressed in undifferentiated ES-hEpoR and parental ES cells at a low level, but this expression was enhanced from day 2 to 14 of differentiation after withdrawal of LIF and culture in the presence of Epo. Furthermore, the enhanced expression of these two transcripts was also noticed in EML-C1 cells, a murine multipotential hematopoietic cell line that has erythroid differentiation potential in response to Epo. In summary, our results demonstrate that Surf-6 gene expression is regulated during differentiation of hematopoietic stem/progenitor cells in response to Epo, suggesting a possible role for Surf-6 gene in erythropoiesis.

Chemokines, chemokine receptors and hematopoiesis

Hematopoiesis during steady state conditions is regulated and finely tuned by a network of cytokines and their effects on hematopoietic stem and progenitor cells and on accessory cells that influence the stem and progenitor cells. Amongst the numerous cytokines implicated in this regulation are members of the CC, CXC and C family of chemokines. Twenty-five chemokine members have been demonstrated to have the capacity to suppress the proliferation of myeloid progenitor cells. Three chemokines have been implicated in the chemotaxis of these stem and progenitor cells, and one has been linked to their survival after growth factor withdrawal. This review focuses on the proliferation-suppressing, chemotaxis-induced, and cell survival effects of different chemokine family members on myeloid progenitor cells. This is placed in the context of what we know and don't know about the intracellular signaling events mediating these effects. This information and what is yet to be learned in this area could have important clinical implications for treatment of disease.

Enhancement of proliferation and differentiation of erythroid progenitors by co-transduction of erythropoietin receptor and H-ras cDNAS into single CD34(3+) cord blood cells

Our previous studies have demonstrated that retrovirus-mediated gene transduction of either the human erythropoietin receptor (EpoR) or H-ras cDNA into single purified hematopoietic progenitor (HPC), CD34(3+), cells from cord blood (CB) resulted in increased numbers and sizes of erythroid cell containing colonies. We therefore evaluated if there were further effects when H-ras and EpoR genes were co-transduced into the same progenitor cells. Highly purified single sorted CD34(3+) CB cells were transduced with retroviral vectors encoding EpoR or H-ras cDNA. At the single cell level, and in response to stimulation by a combination of growth factors, including Epo, the number of colonies formed by BFU-E and CFU-GEMM was significantly increased in cells transduced with either single H-ras or EpoR cDNA compared to mock virus-transduced cells as previously described. Increased numbers of BFU-E, but not CFU-GEMM, colonies were produced from cells simultaneously co-transduced with both EpoR and Hras genes. Little or no growth was seen in transduced cells without exogenously added cytokines. The size of all types of colonies including CFU-GM was increased in cells transduced with H-ras and/or EpoR cDNAs, and the greatest increase was noticed in cells co-transduced with both genes. Integration and expression of either gene in individual colonies as assessed by PCR and RT-PCR analysis were 45-62% and 48-58%, respectively, with approximately 31% of the cells containing and expressing both genes. These results add to information suggesting an enhancing interacting role of H-ras and EpoR in erythroid proliferation/differentiation.

Expression and activation of caspase-3/CPP32 in CD34(+) cord blood cells is linked to apoptosis after growth factor withdrawal

Caspase-3/CPP32, a member of the interleukin-1 converting enzyme (ICE) family, is considered an executioner protease in mammalian cells during apoptosis. Although expression and activation of caspase-3/CPP32 protein have been studied in many tissues and leukemia cell lines, this has not been explored in primitive hematopoietic CD34(+) cells. In this study, we evaluated expression and activation of caspase-3/CPP32 protein in CD34(+) cells from cord blood (CB) during apoptosis induced by growth factor deprivation. Reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, and flow cytometry analysis were used in this study to determine the expression of caspase-3/CPP32 in CD34(+) CB cells during apoptosis. Our results demonstrated that caspase-3/CPP32 mRNA was constitutively expressed at a very low level in freshly isolated CD34(+) cells. Expression of caspase-3/CPP32 mRNA and protein was upregulated when these cells were first expanded in suspension culture with growth factors for 3 days. However, only the 32 kDa inactive caspase-3/CPP32 proenzyme was detected in the freshly isolated CD34(+) cells and after 3 days expansion with cytokines. Within 12 hours after growth factor withdrawal from expanded cells caspase-3/CPP32 was activated and a cleavage 20 kDa protein was detected; a poly(ADP-ribose) polymerase (PARP) was cleaved by activated caspase-3/CPP32. Activation of caspase-3/CPP32 and apoptosis upon growth factor withdrawal were inhibited/reduced by the caspase inhibitors, z-VAD-fmk and DEVD-CHO. These results demonstrate that caspase-3/CPP32 is involved in apoptosis of primitive CB CD34(+) cells but may not be the only mechanism involved.

The CC chemokine CK beta-11/MIP-3 beta/ELC/Exodus 3 mediates tumor rejection of murine breast cancer cells through NK cells

CK beta-11 chemoattracts T cells, B cells, dendritic cells, macrophage progenitors, and NK cells and facilitates dendritic cell and T cell interactions in secondary lymphoid tissues. We hypothesized that expression of CK beta-11 in tumor cells may generate antitumor immunity through these interactions. After transduction with the retroviral vector L(CK beta 11)SN, the murine breast cancer cell line C3L5 (C3L5-CK beta 11) showed expression of retroviral mRNA by Northern analysis and production of functional CK beta-11 by chemotaxis of human NK cells to C3L5-CK beta 11 supernatant. Only 10% of mice injected with C3L5-CK beta 11 developed tumors, compared with 100% of mice injected with a transduced control C3L5 line (C3L5-G1N). Importantly, the in vitro growth characteristics of the CK beta-11-transduced cell line were unaffected, suggesting the difference in growth in vivo was a result of chemokine production. Vaccination with C3L5-CK beta 11 partially protected animals from parental C3L5 challenge. Immunodepletion with anti-asialo-GM1 or anti-CD4 during C3L5-CK beta 11 vaccination significantly reduced CK beta-11 antitumor activity compared with control and anti-CD8-treated groups. Splenocytes from NK-depleted animals transferred the acquired immunity generated with C3L5-CK beta 11 vaccination, while splenocytes from the CD4-depleted animals did not. These results indicate, for the first time, that expression of CK beta-11 in a breast cancer cell line mediates rejection of the transduced tumor through a mechanism involving NK and CD4+ cells. Furthermore, CK beta-11-transduced tumor cells generate long-term antitumor immunity that requires CD4+ cells. These studies demonstrate the potential role of CK beta-11 as an adjuvant in stimulating antitumor responses.

Suppressive effects of TNF-alpha, TGF-beta1, and chemokines on megakaryocytic colony formation in CD34+ cells derived from umbilical cord blood compared with mobilized peripheral blood and bone marrow

CD34+ cells from human umbilical cord blood (CB) were isolated and investigated for megakaryocytic (MK) colony formation in response to recombinant human (rh) stimulatory and suppressive cytokines and compared with their counterparts in normal BM and G-CSF-mobilized peripheral blood (mPBL). First, we observed that IL-11 by itself at any dosage had no stimulator activity on MK colony formation derived from CD34+ cells in CB, mPBL, and BM. IL-3, steel factor (SLF), or thrombopoietin (Tpo) alone stimulated numbers of colony-forming unit-megakaryocyte (CFU-MK) in a dose-dependent fashion. Maximum growth of MK progenitor cells was noted in the presence of a combination of cytokines: IL-11, IL-3, SLF, and Tpo. The frequency of CFU-MK in CB and mPBL was significantly greater than that in BM, and the size of colonies in CB and mPBL was significantly greater than that in BM, and the size of colonies was larger as well. In addition, an increased number of big mixed colonies containing MK were observed in CB and mPBL. In the presence of IL-11, IL-3, SLF, and Tpo, CFU-MK derived from CB, mPBL, and BM was suppressed by tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta1 (TGF-beta1). CFU-MK derived from normal BM was inhibited by some chemokines evaluated, whereas CFU-MK derived from CB was suppressed only by platelet factor-4 (PF-4), IFN-inducible protein-10 (IP-10), Exodus-1, Exodus-2, and Exodus-3, but to a lesser degree. In CB, unlike granulocyte-macrophage (CFU-GM), erythroid (BFU-E), high-proliferative potential (HPP-CFC), or multipotential (CFU-GEMM) progenitors, at least a subpopulation of MK progenitors are in S-phase. Therefore, CB MK progenitors respond to the suppressive effects of some members of the chemokine family. Similar results were noted for burst-forming unit-MK (BFU-MK). Our results indicate that CB and mPBL are rich sources of MK progenitors and that MK progenitors in CB are responsive to the suppressive effects of TNF-alpha and TGF-beta1 and some members of the chemokine family.

Development of a transgenic mouse that overexpresses a novel product of the growth hormone-releasing hormone gene

The GH-releasing hormone (GHRH) precursor molecule contains a 30-amino acid C-terminal region that has been designated GHRH-related peptide (GHRH-RP). To begin to understand the physiological role of GHRH-RP, transgenic (Tg) mice that constituitively express this peptide were developed. To generate these mice, a transgene (SS-RP) was constructed by overlap primer extension PCR. This transgene, under the control of the mouse phosphoglycerate kinase gene, selectively expresses GHRH-RP, but not GHRH. Western blot analysis confirmed that the transgene produces GHRH-RP. Animals were evaluated for the effect of excess GHRH-RP on growth, fertility, behavior, stem cell factor (SCF) expression, and hematopoiesis. Northern blot and RT-PCR were used to demonstrate ubiquitous expression of the transgene in tissues from GHRH-RP Tg animals. These tissues also had marked overexpression of SCF messenger RNA compared with controls. Tg animals had significantly increased cell cycling for granulocyte-macrophage, erythroid, and multilineage progenitor cells. Transgenic animals did not differ from control mice in their growth, fertility, or behavior. These findings demonstrate, for the first time, that in vivo the C-terminal peptide of the pro-GHRH molecule is a biologically active peptide that is capable of stimulating the expression of SCF and hematopoiesis in vivo and suggests that GHRH-RP may play a role in normal blood cell development.

Macrophage migration inhibitory factor release by macrophages after ingestion of Plasmodium chabaudi-infected erythrocytes: possible role in the pathogenesis of malarial anemia

Human falciparum malaria, caused by Plasmodium falciparum infection, results in 1 to 2 million deaths per year, mostly children under the age of 5 years. The two main causes of death are severe anemia and cerebral malaria. Malarial anemia is characterized by parasite red blood cell (RBC) destruction and suppression of erythropoiesis (the mechanism of which is unknown) in the presence of a robust host erythropoietin response. The production of a host-derived erythropoiesis inhibitor in response to parasite products has been implicated in the pathogenesis of malarial anemia. The identity of this putative host factor is unknown, but antibody neutralization studies have ruled out interleukin-1beta, tumor necrosis factor alpha, and gamma interferon while injection of interleukin-12 protects susceptible mice against lethal P. chabaudi infection. In this study, we report that ingestion of P. chabaudi-infected erythrocytes or malarial pigment (hemozoin) induces the release of macrophage migration inhibitory factor (MIF) from macrophages. MIF, a proinflammatory mediator and counter-regulator of glucocorticoid action, inhibits erythroid (BFU-E), multipotential (CFU-GEMM), and granulocyte-macrophage (CFU-GM) progenitor-derived colony formation. MIF was detected in the sera of P. chabaudi-infected BALB/c mice, and circulating levels correlated with disease severity. Liver MIF immunoreactivity increased concomitant with extensive pigment and parasitized RBC deposition. Finally, MIF was elevated three- to fourfold in the spleen and bone marrow of P. chabaudi-infected mice with active disease, as compared to early disease, or of uninfected controls. In summary, the present results suggest that MIF may be a host-derived factor involved in the pathophysiology of malaria anemia.

Recombinant human thrombopoietin attenuates carboplatin-induced severe thrombocytopenia and the need for platelet transfusions in patients with gynecologic cancer

BACKGROUND

Thrombocytopenia is a significant problem in the treatment of cancer.

OBJECTIVE

To assess the clinical safety of therapy with recombinant human thrombopoietin (rhTPO) and its ability to ameliorate chemotherapy-induced severe thrombocytopenia.

DESIGN

Phase I/II clinical cohort study.

SETTING

The University of Texas M.D. Anderson Cancer Center, Houston, Texas.

PATIENTS

29 patients with gynecologic cancer.

INTERVENTION

Recombinant human thrombopoietin was given before chemotherapy and after a second cycle of carboplatin therapy.

MEASUREMENTS

Peripheral blood counts and platelet transfusions.

RESULTS

Administration of rhTPO after chemotherapy significantly reduced the degree and duration of thrombocytopenia and enhanced platelet recovery. In patients who received the optimal biological dose of rhTPO (1.2 microg/kg of body weight) in cycle 2 (carboplatin plus rhTPO), the mean platelet count nadir was higher (44x10(9) cells/L and 20x10(9) cells/L; P = 0.002) and the duration of thrombocytopenia was shorter (days with a platelet count <20x10(9) cells/L, 1 and 4 [P = 0.002]; days with a platelet count <50x10(9) cells/L, 4 and 7 [P = 0.006]) than in cycle 1 (carboplatin only). The need for platelet transfusion in this group was reduced from 75% of patients in cycle 1 to 25% of patients in cycle 2 (P = 0.013).

CONCLUSIONS

Therapy with rhTPO seems to be safe and may attenuate chemotherapy-induced severe thrombocytopenia and reduce the need for platelet transfusions.

Interleukin-11 enhancement of VLA-5 mediated adhesion of CD34+ cells from cord blood to fibronectin is associated with the PI-3 kinase pathway

Adhesion is required for cell growth, differentiation, survival, and function. Cell adhesion is mediated by a structurally diverse group of plasma membrane receptors, each exhibiting specialized ligand-binding properties that are needed for specific tasks. Integrin-mediated adhesion is important for hematopoietic stem (HSC)/progenitor (HPC) cell survival and may prevent programmed cell death. Interleukin (IL)-11, a multi-functional cytokine secreted by the bone marrow environment, plays an important role in regulating growth and differentiation of HSCs/HPCs. In this report, we demonstrate that IL-11 enhanced adhesion of freshly isolated and 3 day-expanded CD34+ cells to immobilized fibronectin. the expression of very late antigen (VLA)-4 and VLA-5 integrins was detected on CD34+ cells. CD34+ cells also expressed a-chain and gp130 subunits of the IL-11 receptor (R). Enhanced adhesion by IL-11 was mediated via activation of VLA-5 integrins, since this action could be blocked by monoclonal antibodies against beta 1 and alpha 5, but not alpha 4, integrins. Addition of phosphatidylinositol (PI)-3 kinase inhibitors blocked IL-11 enhanced adhesion of CD34+ cells to fibronectin. The results suggest that this enhanced adhesion is associated with the PI-3 kinase pathway, an inside-out signaling pathway.

Enhancing effects of co-transduction of both human erythropoietin receptor and c-kit cDNAs into hematopoietic stem/progenitor cells from cord blood on proliferation and differentiation of erythroid progenitors

Steel factor (SLF) and erythropoietin (Epo) play critical roles in erythropoiesis. To evaluate interactive effects of Epo and SLF receptors (R) in erythropoiesis, CD34+ and CD34 cord blood cells were transduced with human EpoR and c-kit cDNAs by retroviral mediated gene transfer. Erythroid (BFU-E) colonies derived from CD34+ or CD34 cells transduced with either the EpoR or c-kit gene were significantly increased in the presence of interleukin (IL)-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), Epo, and different concentrations of SLF compared with that from mock transduced cells. This number was further enhanced by co-transduction of both genes. Enhancement was more apparent in the absence of SLF. Cell numbers in individual erythroid colonies were also significantly increased in cells transduced with both genes compared with cells transduced with a single gene. Short-term liquid culture showed that ex vivo expansion for five days and numbers of CD34+CD71+ cells in expanded cells from single CD34 cells co-transduced with both EpoR and c-kit genes were increased compared with those of EpoR or c-kit-transduced cells. These results demonstrate that co-transduction of both c-kit and EpoR enhances the proliferative capacity of erythroid progenitors under cytokine stimulation above that of single-gene transduced cells.

The exodus subfamily of CC chemokines inhibits the proliferation of chronic myelogenous leukemia progenitors

Chemokines are a family of related proteins that regulate leukocyte infiltration into inflamed tissue and play important roles in disease processes. Among the biologic activities of chemokines is inhibition of proliferation of normal hematopoietic progenitors. However, chemokines that inhibit normal progenitors rarely inhibit proliferation of hematopoietic progenitors from patients with chronic myelogenous leukemia (CML). We and others recently cloned a subfamily of CC chemokines that share similar amino-terminal peptide sequences and a remarkable ability to chemoattract T cells. These chemokines, Exodus-1/LARC/MIP-3alpha, Exodus-2/SLC/6Ckine/TCA4, and Exodus-3/CKbeta11/MIP-3beta, were found to inhibit proliferation of normal human marrow progenitors. The study described here found that these chemokines also inhibited the proliferation of progenitors in every sample of marrow from patients with CML that was tested. This demonstration of consistent inhibition of CML progenitor proliferation makes the 3 Exodus chemokines unique among chemokines. (Blood. 2000;95:1506-1508)

Transduction of human IL-9 receptor cDNA into TF1 cells induces IL-9 dependency and erythroid differentiation

Human growth factor-dependent cell line TF1, which lacks interleukin (IL)-9 receptors (R) and does not grow in IL-9, was transduced with a retroviral vector containing human IL-9R cDNA and a selection marker. An IL-9-dependent TF1 cell line, which could also grow in other cytokines, was established after selection in G418 and could produce mature RBC in response to cytokine stimulation. TF1 cells transduced with the same viral vector without the IL-9R insert cDNA (mock control) and then selected responded the same as nontransduced TF1 cells. They failed to grow in response to IL-9 and did not generate RBC. An increased number and size of burst-forming units-erythroid (BFU-E)-like colonies were detected from IL-9R-transduced TF1 cells, compared with mock-transduced cells, in response to erythropoietin (EPO) and IL-9. To evaluate self-renewal and differentiation capacity, colony-replating assays were performed in the presence of IL-3, GM-CSF, IL-9, and EPO. After four replatings, the cloning efficiency of IL-9R-transduced TF1 cells decreased from 98% to 38%, most likely due to terminal erythroid cell differentiation. In contrast, no change in replating efficiency was detected in mock-transduced cells. TF1 cells stably expressing IL-9R and responding to IL-9 can serve as a cell line model to study the intracellular signals mediating IL-9-induced erythroid cell proliferation and differentiation.

Differential in vitro maturation of hematopoietic stem cells from wild-type and immunoglobulin transgenic mice

During B-cell lymphopoiesis, hematopoietic stem cells commit to the B-cell lineage as monitored by the expression of phenotypic cell surface antigens and the production of immunoglobulin chains. Two cytokines, interleukin-7 (IL-7) and Flt-3 ligand (FL), appear to act in conjunction to drive this development process. Using an in vitro, stroma-free culture system and these cytokines, the commitment of murine Sca+ Lin- bone marrow cells to the B-cell lineage was examined with stem cells from immunoglobulin (Ig) transgenic and wild-type mice. After 12 days of culture in IL-7 and FL, stem cells from wild-type animals had matured to express surface B220, CD19, CD43, BP-1 and heat-stable antigen (HSA). These cells lacked detectable intracellular mu chains while exhibiting partial D-J rearrangement. In contrast, Sca+Lin- cells from Ig transgenic mice that were cultured similarly expressed B220, CD19, IgD, intracellular and surface mu, HSA but not CD43 or BP-1. These results suggest that expression of the Ig transgene during in vitro development overcame a block in B-cell lymphopoiesis and recapitulated in vivo events. Thus, IL-7 and FL treatment allowed uncommitted stem cells to progress to the early pre-B-cell stage while similarly treated Ig transgenic cells progressed completely to the mature B-cell stage.

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.

Retroviral-mediated gene transduction of c-kit into single hematopoietic progenitor cells from cord blood enhances erythroid colony formation and decreases sensitivity to inhibition by tumor necrosis factor-alpha and transforming growth factor-beta1

The c-kit receptor and its ligand, steel factor (SLF), are critical for optimal hematopoiesis. We evaluated effects of transducing cord blood (CB) progenitor cells with a retrovirus encoding human c-kit cDNA. CD34(+) cells were sorted as a population or as 1 cell/well for cells expressing high levels of CD34 and different levels of c-kit (++,+,Lo/-), transduced and then cultured in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), IL-6, erythropoietin (Epo) +/- SLF in the absence of serum. At a single-cell level, transduction with c-kit, but not with control (neo only), virus significantly increased colony formation, especially by erythroid and multipotential progenitors. The enhancing effect of c-kit transduction was inversely correlated with expression of c-kit protein before transduction. The greatest enhancing effects were noted in CD34KitLo+/- cells transduced with c-kit. The stimulating effect was apparent even in the absence of exogenously added SLF, but in the presence of GM-CSF, IL-3, IL-6, and Epo. Enzyme-linked immunosorbent assay (ELISA) of SLF protein, reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of SLF mRNA expression in CD34+ cells, and use of neutralizing antibodies to SLF and/or c-kit suggested the presence of endogenous, although probably very low level, expression of SLF by these progenitor cells. Transduction of c-kit significantly decreased sensitivity of progenitor cells to the inhibitory effects of transforming growth factor-beta1 and tumor necrosis factor-alpha. c-kit-transduced cells had increased expression of c-kit protein and decreased spontaneous or cytokine-induced apoptosis. Our results suggest that transduced c-kit into selected progenitor cells can enhance proliferation and decrease apoptosis and that endogenous SLF may mediate this effect.

TECK, an efficacious chemoattractant for human thymocytes, uses GPR-9-6/CCR9 as a specific receptor

Chemokines regulate leukocytes trafficking in normal and inflammation conditions. Thymus-seeding progenitors are made in bone marrow and migrate to the thymus where they undergo their maturation to antigen-specific T cells. Immature T cells are in thymic cortex, while mature thymocytes are in medulla. Chemokines may be important for homing of thymus-seeding progenitors, and/or differential thymocyte localization in thymus. Here we report that GPR-9-6, now called CC chemokine receptor 9 (CCR9), is a receptor for thymus-expressed chemokine, TECK. Among a panel of chemokines tested, TECK specifically induced calcium flux in CCR9-expressing cell lines. We also showed that TECK efficaciously induced chemotaxis of immature CD4(+)CD8(+) double-positive, and mature CD4(+) and CD8(+) single-positive human thymocytes. Our data suggest that TECK/CCR9 interaction may play a pivotal role in T-cell migration in the thymus.

The effects of GM-CSF, steel factor and MIP-1alpha on the expression and activation of Cdc25A phosphatase in Mo7e cells

Active cyclin-dependent kinases (CDKs) are required for progression through the G1 phase of the cell cycle and entry into S phase. Activity of G1 CDKs is controlled by mechanisms including phosphorylation of Thr14 and Tyr15 residues. Removal of inhibitory phosphates on these amino acid residues is required for G1 CDK activation, and is mediated by the Cdc25A phosphatase. Regulation of active Cdc25A phosphatase levels may be important for the proliferation of hematopoietic progenitor cells, effects assessed in the human growth-factor-dependent cell line Mo7e. Constitutive Cdc25A protein levels were enhanced with granulocyte-macrophage colony-stimulating factor (GM-CSF) plus steel factor (SF). Cdc25A is thought to exert its activity in the nucleus, and nuclear protein levels of Cdc25A were also enhanced with GM-CSF and SF. GM-CSF plus SF promote synergistic growth of Mo7e cells. Pretreatment with macrophage inflammatory protein (MIP-1alpha) inhibited GM-CSF- plus SF-induced growth and upregulation of Cdc25A protein levels. Stimulation with GM-CSF and SF also rapidly increased Cdc25A phosphatase activity, an effect suppressed by MIP-1alpha. A concomitant inhibition of increased CDK4 kinase activity correlated with increased phosphotyrosine levels on CDK4 when cells were pretreated with MIP-1alpha prior to GM-CSF and SF. These data suggest that Cdc25A expression and activity are regulated during proliferation of Mo7e cells.