References

Teratoma formation is a critical obstacle to safe clinical translation of human embryonic stem (ES) cell-based therapies in the future. As current methods of isolation are unable to yield 100% pure population of differentiated cells from a pluripotent donor source, potential development of these tumors is a significant concern. Here we used non-invasive reporter gene imaging to investigate the relationship between human ES cell number and teratoma formation in a xenogenic model of ES cell transplantation. Human ES cells (H9 line) were stably transduced with a double fusion (DF) reporter construct containing firefly luciferase and enhanced green fluorescent protein (Fluc- eGFP) driven by a human ubiquitin promoter. Immunodeficient mice received intramyocardial (n = 35) or skeletal muscle (n = 35) injection of 1 × 102, 1 × 103, 1 × 104, 1 × 105 or 1 × 106 DF positive ES cells suspended in saline for myocardium and Matrigel for skeletal muscle. Cell survival and proliferation were monitored via bioluminescence imaging (BLI) for an 8 week period following transplantation. Mice negative for Fluc signal after 8 weeks were followed out to day 365 to confirm tumor absence. Significantly, in this study, a minimum of 1 × 105 ES cells in the myocardium and 1 × 104 cells in the skeletal muscle was observed to be requisite for teratoma development, suggesting that human ES cell number may be a critical factor in teratoma formation. Engraftment and tumor occurrence were also observed to be highly dependent on ES cell number. We anticipate these results should yield useful insights to the safe and reliable application of human ES cell derivatives in the clinic. Keywords View Publication

The adult rat hippocampus contains fibroblast growth factor 2-responsive stem cells that are self-renewing and have the ability to generate both neurons and glia in vitro, but little is known about the molecular events that regulate stem cell differentiation. Hippocampus-derived stem cell clones were used to examine the effects of retinoic acid (RA) on neuronal differentiation. Exposure to RA caused an immediate up-regulation of NeuroD, increased p21 expression, and concurrent exit from cell cycle. These changes were accompanied by a threefold increase in the number of cells differentiating into immature neurons. An accompanying effect of RA was to sustain or up-regulate trkA, trkB, trkC, and p75NGFR expression. Without RA treatment, cells were minimally responsive to neurotrophins (NTs), whereas the sequential application of RA followed by brain-derived neurotrophic factor or NT-3 led to a significant increase in neurons displaying mature y-a-minobutyric acid, acetylcholinesterase, tyrosine hydroxylase, or calbindin phenotypes. Although NTs promoted maturation, they had little effect on the total number of neurons generated, suggesting that RA and neurotrophins acted at distinct stages in neurogenesis. RA first promoted the acquisition of a neuronal fate, and NTs subsequently enhanced maturation by way of RA-dependent expression of the Trk receptors. In combination, these sequential effects were sufficient to stimulate stem cell-derived progenitors to differentiate into neurons displaying a variety of transmitter phenotypes. View Publication

BACKGROUND: The mitomycins are natural products that contain a variety of functional groups, including aminobenzoquinone- and aziridine-ring systems. Mitomycin C (MC) was the first recognized bioreductive alkylating agent, and has been widely used clinically for antitumor therapy. Precursor-feeding studies showed that MC is derived from 3-amino-5-hydroxybenzoic acid (AHBA), D-glucosamine, L-methionine and carbamoyl phosphate. A genetically linked AHBA biosynthetic gene and MC resistance genes were identified previously in the MC producer Streptomyces lavendulae NRRL 2564. We set out to identify other genes involved in MC biosynthesis. RESULTS: A cluster of 47 genes spanning 55 kilobases of S. lavendulae DNA governs MC biosynthesis. Fourteen of 22 disruption mutants did not express or overexpressed MC. Seven gene products probably assemble the AHBA intermediate through a variant of the shikimate pathway. The gene encoding the first presumed enzyme in AHBA biosynthesis is not, however, linked within the MC cluster. Candidate genes for mitosane nucleus formation and functionalization were identified. A putative MC translocase was identified that comprises a novel drug-binding and export system, which confers cellular self-protection on S. lavendulae. Two regulatory genes were also identified. CONCLUSIONS: The overall architecture of the MC biosynthetic gene cluster in S. lavendulae has been determined. Targeted manipulation of a putative MC pathway regulator led to a substantial increase in drug production. The cloned genes should help elucidate the molecular basis for creation of the mitosane ring system, as well efforts to engineer the biosynthesis of novel natural products. View Publication

Human mesenchymal stem cells are thought to be multipotent cells, which are present in adult marrow, that can replicate as undifferentiated cells and that have the potential to differentiate to lineages of mesenchymal tissues, including bone, cartilage, fat, tendon, muscle, and marrow stroma. Cells that have the characteristics of human mesenchymal stem cells were isolated from marrow aspirates of volunteer donors. These cells displayed a stable phenotype and remained as a monolayer in vitro. These adult stem cells could be induced to differentiate exclusively into the adipocytic, chondrocytic, or osteocytic lineages. Individual stem cells were identified that, when expanded to colonies, retained their multilineage potential. View Publication

AG-490 is a member of the tyrphostin family of tyrosine kinase inhibitors. While AG-490 has been considered to be a Janus kinase (JAK)2-specific inhibitor, these conclusions were primarily drawn from acute lymphoblastic leukemia cells that lack readily detectable levels of JAK3. In the present study, evidence is provided that clearly demonstrates AG-490 potently suppresses IL-2-induced T cell proliferation, a non-JAK2-dependent signal, in a dose-dependent manner in T cell lines D10 and CTLL-2. AG-490 blocked JAK3 activation and phosphorylation of its downstream counterpart substrates, STATs. Inhibition of JAK3 by AG-490 also compromised the Shc/Ras/Raf/mitogen-activated protein kinase (MAPK) signaling pathways as measured by phosphorylation of Shc and extracellular signal-related kinase 1 and 2 (ERK1/2). AG-490 effectively inhibited tyrosine phosphorylation and DNA binding activities of several transcription factors including STAT1, -3, -5a, and -5b and activating protein-1 (AP-1) as judged by Western blot analysis and electrophoretic mobility shift assay. These data suggest that AG-490 is a potent inhibitor of the JAK3/STAT, JAK3/AP-1, and JAK3/MAPK pathways and their cellular consequences. Taken together, these findings support the notion that AG-490 possesses previously unrecognized clinical potential as an immunotherapeutic drug due to its inhibitory effects on T cell-derived signaling pathways. View Publication

Fetal liver, the major site of hematopoiesis during embryonic development, acquires additional various metabolic functions near birth. Although liver development has been characterized biologically as consisting of several distinct steps, the molecular events accompanying this process are just beginning to be characterized. In this study, we have established a novel culture system of fetal murine hepatocytes and investigated factors required for development of hepatocytes. We found that oncostatin M (OSM), an interleukin-6 family cytokine, in combination with glucocorticoid, induced maturation of hepatocytes as evidenced by morphological changes that closely resemble more differentiated hepatocytes, expression of hepatic differentiation markers and intracellular glycogen accumulation. Consistent with these in vitro observations, livers from mice deficient for gp130, an OSM receptor subunit, display defects in maturation of hepatocytes. Interestingly, OSM is expressed in CD45(+) hematopoietic cells in the developing liver, whereas the OSM receptor is expressed predominantly in hepatocytes. These results suggest a paracrine mechanism of hepatogenesis; blood cells, transiently expanding in the fetal liver, produce OSM to promote development of hepatocytes in vivo. View Publication

ADP-ribosylation factors (ARFs) are members of a multigene family of 20-kDa guanine nucleotide-binding proteins that are regulatory components in several pathways of intracellular vesicular trafficking. The relatively small (approximately 180-amino acids) ARF proteins interact with a variety of molecules (in addition to GTP/GDP, of course). Cholera toxin was the first to be recognized, hence the name. Later it was shown that ARF also activates phospholipase D. Different parts of the molecule are responsible for activation of the two enzymes. In vesicular trafficking, ARF must interact with coatomer to recruit it to a membrane and thereby initiate vesicle budding. ARF function requires that it alternate between GTP- and GDP-bound forms, which involves interaction with regulatory proteins. Inactivation of ARF-GTP depends on a GTPase-activating protein or GAP. A guanine nucleotide-exchange protein or GEP accelerates release of bound GDP from inactive ARF-GDP to permit GTP binding. Inhibition of GEP by brefeldin A (BFA) blocks ARF activation and thereby vesicular transport. In cells, it causes apparent disintegration of Golgi structure. Both BFA-sensitive and insensitive GEPs are known. Sequences of peptides from a BFA-sensitive GEP purified in our laboratory revealed the presence of a Sec7 domain, a sequence of approximately 200 amino acids that resembles a region in the yeast Sec7 gene product, which is involved in Golgi vesicular transport. Other proteins of unknown function also contain Sec7 domains, among them a lymphocyte protein called cytohesin-1. To determine whether it had GEP activity, recombinant cytohesin-1 was synthesized in E. coli. It preferentially activated class I ARFs 1 and 3 and was not inhibited by BFA but failed to activate ARF5 (class II). There are now five Sec7 domain proteins known to have GEP activity toward class I ARFs. It remains to be determined whether there are other Sec7 domain proteins that are GEPs for ARFs 4, 5, or 6. View Publication

Analysis of the National Cancer Institute Human Tumor Cell Line Anti-Cancer Drug Screen data using the COMPARE algorithm to detect similarities in the pattern of compound action to flavopiridol, a known inhibitor of cyclin-dependent kinases (CDKs), has suggested several possible novel CDK inhibitors. 9-Bromo-7,12-dihydro-indolo[3,2-d][1]benzazepin-6(5H)-one, NSC-664704 (kenpaullone), is reported here to be a potent inhibitor of CDK1/cyclin B (IC50, 0.4 microM). This compound also inhibited CDK2/cyclin A (IC50, 0.68 microM), CDK2/cyclin E (IC50, 7.5 microM), and CDK5/p25 (IC50, 0.85 microM) but had much less effect on other kinases; only c-src (IC50, 15 microM), casein kinase 2 (IC50, 20 microM), erk 1 (IC50, 20 microM), and erk 2 (IC50, 9 microM) were inhibited with IC50s less than 35 microM. Kenpaullone acts by competitive inhibition of ATP binding. Molecular modeling indicates that kenpaullone can bind in the ATP binding site of CDK2 with residue contacts similar to those observed in the crystal structures of other CDK2-bound inhibitors. Analogues of kenpaullone, in particular 10-bromopaullone (NSC-672234), also inhibited various protein kinases including CDKs. Cells exposed to kenpaullone and 10-bromopaullone display delayed cell cycle progression. Kenpaullone represents a novel chemotype for compounds that preferentially inhibit CDKs. View Publication

A brefeldin A (BFA)-inhibited guanine nucleotide-exchange protein (GEP) for ADP-ribosylation factors (ARF) was purified earlier from bovine brain cytosol. Cloning and expression of the cDNA confirmed that the recombinant protein (p200) is a BFA-sensitive ARF GEP. p200 contains a domain that is 50% identical in amino acid sequence to a region in yeast Sec7, termed the Sec7 domain. Sec7 domains have been identified also in other proteins with ARF GEP activity, some of which are not inhibited by BFA. To identify structural elements that influence GEP activity and its BFA sensitivity, several truncated mutants of p200 were made. Deletion of sequence C-terminal to the Sec7 domain did not affect GEP activity. A protein lacking 594 amino acids at the N terminus, as well as sequence following the Sec7 domain, also had high activity. The mutant lacking 630 N-terminal amino acids was, however, only 1% as active, as was the Sec7 domain itself (mutant lacking 697 N-terminal residues). It appears that the Sec7 domain of p200 contains the catalytic site but additional sequence (perhaps especially that between positions 595 and 630) modifies activity dramatically. Myristoylated recombinant ARFs were better than non-myristoylated as substrates; ARFs 1 and 3 were better than ARF5, and no activity was detected with ARF6. Physical interaction of the Sec7 domain with an ARF1 mutant was demonstrated, but it was much weaker than that of the cytohesin-1 Sec7 domain with the same ARF protein. Effects of BFA on p200 and all mutants with high activity were similar with approximately 50% inhibition at textless/=50 microM. The inactive BFA analogue B36 did not inhibit the Sec7 domain or p200. Thus, the Sec7 domain of p200, like that of Sec7 itself (Sata, M., Donaldson, J. G., Moss, J., and Vaughan, M. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 4204-4208), plays a role in BFA inhibition as well as in GEP activity, although the latter is markedly modified by other structural elements. View Publication

The propagation of pluripotent mouse embryonic stem (ES) cells depends on signals transduced through the cytokine receptor subunit gp130. Signalling molecules activated downstream of gp130 in ES cells include STAT3, the protein tyrosine phosphatase SHP-2, and the mitogen-activated protein kinases, ERK1 and ERK2. A chimaeric receptor in which tyrosine 118 in the gp130 cytoplasmic domain was mutated did not engage SHP-2 and failed to activate ERKs. However, this receptor did support ES cell self-renewal. In fact, stem cell colonies formed at 100-fold lower concentrations of cytokine than the unmodified receptor. Moreover, altered ES cell morphology and growth were observed at high cytokine concentrations. These indications of deregulated signalling in the absence of tyrosine 118 were substantiated by sustained activation of STAT3. Confirmation that ERK activation is not required for self-renewal was obtained by propagation of pluripotent ES cells in the presence of the MEK inhibitor PD098059. In fact, the growth of undifferentiated ES cells was enhanced by culture in PD098059. Thus activation of ERKs appears actively to impair self-renewal. These data imply that the self-renewal signal from gp130 is a finely tuned balance of positive and negative effectors. View Publication

OBJECTIVE To investigate the inhibition of matrix metalloproteinase 1 (MMP-1), MMP-8, and MMP-13 by doxycycline, and to determine whether the variable hemopexin-like domain of each MMP was responsible for the differences in susceptibility to doxycycline inhibition among these collagenases. METHODS Recombinant human MMP-1 (collagenase 1), MMP-8 (collagenase 2), and MMP-13 (collagenase 3), truncated forms of MMP-8 and MMP-13 lacking the hemopexin-like domain, and a mutant form of truncated MMP-13 were used in these studies. The activity of the full-length MMP in the presence of doxycycline was tested against type II collagen, a natural substrate for the enzymes. A small peptolide substrate was used to determine which structural features of the MMPs were related to sensitivity to doxycycline inhibition. RESULTS The activity of MMP-13 and MMP-8 against type II collagen was inhibited by 50-60% by 30 microM doxycycline, while that of MMP-1 was inhibited only 18% by 50 microM doxycycline. In contrast, in experiments with the peptolide substrate, neither full-length nor truncated MMP-13 was inhibited until the concentration of the drug exceeded 90 microM. MMP-8 and truncated MMP-8 were sensitive to inhibition by 30 microM doxycycline, while MMP-1 was slightly inhibited (14%) by 90 microM doxycycline. For MMP-8, inhibition was reversible upon dilution and was independent of the order in which the reagents were added. Kinetic analysis of the inhibition constant (K(i)) of MMP-8 (K(i) = 36 microM) and truncated MMP-8 (K(i) = 77 microM) indicated that inhibition was noncompetitive. CONCLUSION Significant inhibition of MMP-13 and MMP-8 activity against collagen occurred in vitro at concentrations that were near the concentrations achieved in serum after oral dosing. Studies with truncated enzymes and 2 substrates suggest that doxycycline disrupts the conformation of the hemopexin-like domain of MMP-13 and the catalytic domain of MMP-8. View Publication

We have generated rat monoclonal antibodies specific for the mouse eotaxin receptor, C-C chemokine receptor 3 (CCR3). Several anti-CCR3 mAbs proved to be useful for in vivo depletion of CCR3-expressing cells and immunofluorescent staining. In vivo CCR3 mAbs of the IgG2b isotype substantially depleted blood eosinophil levels in Nippostrongyus brasiliensis-infected mice. Repeated anti-CCR3 mAb treatment in these mice significantly reduced tissue eosinophilia in the lung tissue and bronchoalveolar lavage fluid. Flow cytometry revealed that mCCR3 was expressed on eosinophils but not on stem cells, dendritic cells, or cells from the thymus, lymph node, or spleen of normal mice. Unlike human Th2 cells, mouse Th2 cells did not express detectable levels of CCR3 nor did they give a measurable response to eotaxin. None of the mAbs were antagonists or agonists of CCR3 calcium mobilization. To our knowledge, the antibodies described here are the first mAbs reported to be specific for mouse eosinophils and to be readily applicable for the detection, isolation, and in vivo depletion of eosinophils. View Publication

A novel homology model of the kinase domain of Janus kinase (JAK) 3 was used for the structure-based design of dimethoxyquinazoline compounds with potent and specific inhibitory activity against JAK3. The active site of JAK3 in this homology model measures roughly 8 A x 11 A x 20 A, with a volume of approximately 530 A3 available for inhibitor binding. Modeling studies indicated that 4-(phenyl)-amino-6,7-dimethoxyquinazoline (parent compound WHI-258) would likely fit into the catalytic site of JAK3 and that derivatives of this compound that contain an OH group at the 4' position of the phenyl ring would more strongly bind to JAK3 because of added interactions with Asp-967, a key residue in the catalytic site of JAK3. These predictions were consistent with docking studies indicating that compounds containing a 4'-OH group, WHI-P131 [4-(4'-hydroxyphenyl)-amino-6,7-dimethoxyquinazoline], WHI-P154 [4-(3'-bromo-4'-hydroxylphenyl)-amino-6,7-dimethoxyquinazoline], and WHI-P97 [4-(3',5'-dibromo-4'-hydroxylphenyl)-amino-6,7-dimethoxyquinazolin e], were likely to bind favorably to JAK3, with estimated K(i)s ranging from 0.6 to 2.3 microM. These compounds inhibited JAK3 in immune complex kinase assays in a dose-dependent fashion. In contrast, compounds lacking the 4'-OH group, WHI-P79 [4-(3'-bromophenyl)-amino-6,7-dimethoxyquinazoline], WHI-P111 [4-(3'-bromo-4'-methylphenyl)-amino-6,7-dimethoxyquinazoline], WHI-P112 [4-(2',5'-dibromophenyl)-amino-6,7-dimethoxyquinazoline], WHI-P132 [4-(2'-hydroxylphenyl)-amino-6,7-dimethoxyquinazoline], and WHI-P258 [4-(phenyl)-amino-6,7-dimethoxyquinazoline], were predicted to bind less strongly, with estimated K(i)s ranging from 28 to 72 microM. These compounds did not show any significant JAK3 inhibition in kinase assays. Furthermore, the lead dimethoxyquinazoline compound, WHI-P131, which showed potent JAK3-inhibitory activity (IC50 of 78 microM), did not inhibit JAK1 and JAK2, the ZAP/SYK family tyrosine kinase SYK, the TEC family tyrosine kinase BTK, the SRC family tyrosine kinase LYN, or the receptor family tyrosine kinase insulin receptor kinase, even at concentrations as high as 350 microM. WHI-P131 induced apoptosis in JAK3-expressing human leukemia cell lines NALM-6 and LC1;19 but not in melanoma (M24-MET) or squamous carcinoma (SQ20B) cells. Leukemia cells were not killed by dimethoxyquinazoline compounds that were inactive against JAK3. WHI-P131 inhibited the clonogenic growth of JAK3-positive leukemia cell lines DAUDI, RAMOS, LC1;19, NALM-6, MOLT-3, and HL-60 (but not JAK3-negative BT-20 breast cancer, M24-MET melanoma, or SQ20B squamous carcinoma cell lines) in a concentration-dependent fashion. Potent and specific inhibitors of JAK3 such as WHI-P131 may provide the basis for the design of new treatment strategies against acute lymphoblastic leukemia, the most common form of childhood cancer. View Publication

PP1 has previously been described as an inhibitor of the Src-family kinases p56(Lck) and FynT. We have therefore decided to use PP1 to determine the functional role of Src in platelet-derived growth factor (PDGF)-induced proliferation and migration of human coronary artery smooth muscle cells (HCASMCs). A synthetic protocol for PP1/AGL1872 has been developed, and the inhibitory activity of PP1/AGL1872 against Src was examined. PP1/AGL1872 potently inhibited recombinant p60(c-src) in vitro and Src-dependent tyrosine phosphorylation in p60(c-srcF572)-transformed NIH3T3 cells. PP1/AGL1872 also potently inhibited PDGF-stimulated migration of HCASMCs, as determined in the modified Boyden chamber, as well as PDGF-stimulated proliferation of HCASMCs. Surprisingly, in addition to inhibition of Src kinase, PP1/AGL1872 was found to inhibit PDGF receptor kinase in cell-free assays and in various types of intact cells, including HCASMCs. PP1/AGL1872 did not inhibit phosphorylation of the vascular endothelial growth factor receptor KDR (VEGF receptor-2; kinase-insert domain containing receptor) in cell-free assays as well as in intact human coronary artery endothelial cells. In line with the insensitivity of KDR, PP1/AGL1872 had only a weak effect on vascular endothelial growth factor-stimulated migration of human coronary artery endothelial cells. On treatment of cells expressing different receptor tyrosine kinases, the activities of the epidermal growth factor receptor, fibroblast growth factor receptor-1, and insulin-like growth factor-1 receptor were resistant to PP1/AGL1872, whereas PDGF alpha-receptor was susceptible, albeit to a lesser extent than PDGF beta-receptor. These data suggest that the previously described tyrosine kinase inhibitor PP1/AGL1872 is not selective for the Src family of tyrosine kinases. It is also a potent inhibitor of the PDGF beta-receptor kinase but is not a ubiquitous tyrosine kinase inhibitor. PP1/AGL1872 inhibits migration and proliferation of HCASMCs probably by interference with 2 distinct tyrosine phosphorylation events, creating a novel and potent inhibitory principle with possible relevance for the treatment of pathological HCASMC activity, such as vascular remodeling and restenosis. View Publication

Wine polyphenols were examined for their capacity to protect the lipid and protein moieties of porcine low density lipoproteins (LDL) during oxidation. The efficiency of resveratrol (3, 4', 5, trihydroxystilbene) and defined flavonoids was compared to that of a wine extract (WE) containing 0.5 g/g proanthocyanidols. The efficiency of resveratrol for protecting polyunsaturated fatty acids (PUFA) was higher than that of flavonoids in copper-induced oxidation and lower in AAPH (radical initiator)-induced oxidation. The LDL receptor activity was evaluated by flow cytometry using LDL labeled with fluorescein isothiocyanate (FITC) and Chinese hamster ovary cells (CHO-K1). The incubation of CHO-K1 with FITC-LDL oxidized for 16 h reduced the proportion of fluorescent cells from 97% to 4%. At a concentration of 40 microM, resveratrol and flavonoids completely restored the uptake of copper-oxidized LDL and AAPH-oxidized LDL respectively. Total fluorescence could also be obtained with 20 mg/L of WE with both oxidation systems. These data are consistent with previous findings relative to the formation of degradative products from PUFA. They confirm that resveratrol was more effective than flavonoids as a chelator of copper and less effective as a free-radical scavenger. Moreover, they show that WE, which contained monomeric and oligomeric forms of flavonoids and phenolic acids, protected LDL by both mechanisms. View Publication

In this report, we sought to optimize gene transfer into primitive human umbilical cord blood (UCB) cells. Initially, we found that fresh UCB isolated with the CD34brCD38 CD33 phenotype were highly enriched for hematopoietic progenitors detected in extended long-term cultures (8-week LTCs). In addition, following ex vivo gene transfer, this population possessed virtually all the 8-week LTC activity of the cultured cells. A multiparameter FACS assay was developed to efficiently screen the effects of alternative retroviral vector gene transfer procedures on the transduction efficiency and maintenance of CD34brCD38 CD33 cells. Proliferation of the CD34brCD38 CD33 cells was found to be a prerequisite for efficient transduction. However, in all conditions tested, proliferation of the CD34brCD38 CD33 cells was associated with a progressive loss of primitive cell properties including a reduction in CD34 expression, an increase in CD38/CD33 expression, and a decline in the ability to sustain 8-week LTCs. These observations indicate that it will be necessary to define conditions that more effectively support the self-renewal capacity of CD34brCD38 CD33 cells to optimize retroviral vector gene transfer in these cells. Evaluating these conditions and reagents will be facilitated by the multiparameter FACS assay described in this report. View Publication

Bispecific antibodies directed against tumor-associated target antigens and to surface receptors mediating T-cell activation, such as the TCR/CD3 complex and the costimulatory receptor CD28, are capable of mediating T-cell activation resulting in tumor cell killing. In this study, we used the B-cell-associated antigens CD19 and CD20 as target structures on human leukemic cells. We found that a combination of bispecific antibody fragments (bsFab2) with target x CD3 and target x CD28 specificity induces vigorous autologous T-cell activation and killing of malignant cells in peripheral blood and bone marrow cultures from patients with chronic lymphocytic leukemia and follicular lymphoma. The bsFab2 targeting CD20 were considerably more effective than those binding to CD19. The colony-forming capacity of treated bone marrow was impaired due to large amounts of tumor necrosis factor alpha produced during bsFab2-induced T-cell activation. Neutralizing tumor necrosis factor alpha antibodies were found to reverse this negative effect without affecting T-cell activation and tumor cell killing. CD20 x CD28 bsFab2, when used alone rather than in combination, markedly improved the recognition of leukemic cells by allogeneic T cells. Therefore, these reagents may be capable of enhancing the immunogenicity of leukemic cells in general and, in particular, of increasing the antileukemic activity of allogeneic donor buffy coat cells in relapsed bone marrow transplanted patients. View Publication

Because hematopoietic stem cells are rich in aldehyde dehydrogenase (ALDH) activity, we developed a fluorescent substrate for ALDH, termed BODIPY aminoacetaldehyde (BAAA), and tested its potential for isolating primitive human hematopoietic cells. A population of cells with low orthogonal light scattering and bright fluorescence intensity (SSC(lo)ALDH(br) cells) could be readily fractionated from human umbilical cord blood cells costained with BAAA and the multidrug-resistance inhibitor verapamil. The SSC(lo)ALDH(br) population was depleted of lineage-committed cells, 40-90% pure for CD34(+)CD38(lo/-) cells, and enriched 50- to 100-fold for primitive hematopoietic progenitors detected in short- and long-term culture analyses. Together, these observations indicate that fractionating human hematopoietic stem cells on the basis of ALDH activity using BAAA is an effective method for isolating primitive human hematopoietic progenitors. This technique may be useful for isolating stem cells from other tissues as well. View Publication

To study molecular events involved in B lymphocyte development and V(D)J rearrangement, we have established an efficient system for the differentiation of embryonic stem (ES) cells into mature Ig-secreting B lymphocytes. Here, we show that B lineage cells generated in vitro from ES cells are functionally analogous to normal fetal liver-derived or bone marrow-derived B lineage cells at three important developmental stages: first, they respond to Flt-3 ligand during an early lymphopoietic progenitor stage; second, they become targets for Abelson murine leukemia virus (A-MuLV) infection at a pre-B cell stage; third, they secrete Ig upon stimulation with lipopolysaccharide at a mature mitogen-responsive stage. Moreover, the ES cell-derived A-MuLV-transformed pre-B (EAB) cells are phenotypically and functionally indistinguishable from standard A-MuLV-transformed pre-B cells derived from infection of mouse fetal liver or bone marrow. Notably, EAB cells possess functional V(D)J recombinase activity. In particular, the generation of A-MuLV transformants from ES cells will provide an advantageous system to investigate genetic modifications that will help to elucidate molecular mechanisms in V(D)J recombination and in A-MuLV-mediated transformation. View Publication

The termination of activation signals is a critical step in the control of the immune response; perturbation of inhibitory feedback pathways results in profound immune defects culminating in autoimmunity and overwhelming inflammation. FcgammaRIIB receptor is a well described inhibitory receptor. The ligation of B-cell receptor (BCR) and FcgammaRIIB leads to the inhibition of B-cell activation. Numerous studies have demonstrated that the SH2-domain-containing inositol 5-phosphatase SHIP (referred hereto as SHIP-1) is essential in this process. The cDNA encoding a second SH2-domain-containing inositol 5-phosphatase, SHIP-2, has been cloned [Pesesse, Deleu, De Smedt, Drayer and Erneux (1997) Biochem. Biophys. Res. Commun. 239, 697-700]. Here we report the distribution of SHIP-2 in mouse tissues: a Western blot analysis of mouse tissues reveals that SHIP-2 is expressed in both haemopoietic and non-haemopoietic cells. In addition to T-cell and B-cell lines, spleen, thymus and lung are shown to coexpress SHIP-1 and SHIP-2. Moreover, SHIP-2 is detected in fibroblasts, heart and different brain areas. SHIP-2 shows a maximal tyrosine phosphorylation and association to Shc after ligation of BCR to FcgammaRIIB but not after stimulation of BCR alone. Our results therefore suggest a possible role for SHIP-2 in the negative regulation of immunocompetent cells. View Publication

Chemotherapy and radiation therapy for cancer often have severe side effects that limit their efficacy. Because these effects are in part determined by p53-mediated apoptosis, temporary suppression of p53 has been suggested as a therapeutic strategy to prevent damage of normal tissues during treatment of p53-deficient tumors. To test this possibility, a small molecule was isolated for its ability to reversibly block p53-dependent transcriptional activation and apoptosis. This compound, pifithrin-alpha, protected mice from the lethal genotoxic stress associated with anticancer treatment without promoting the formation of tumors. Thus, inhibitors of p53 may be useful drugs for reducing the side effects of cancer therapy and other types of stress associated with p53 induction. View Publication

We have previously identified multipotent neuroepithelial (NEP) stem cells and lineage-restricted, self-renewing precursor cells termed NRPs (neuron-restricted precursors) and GRPs (glial-restricted precursors) present in the developing rat spinal cord (A. Kalyani, K. Hobson, and M. S. Rao, 1997, Dev. Biol. 186, 202-223; M. S. Rao and M. Mayer-Proschel, 1997, Dev. Biol. 188, 48-63; M. Mayer-Proschel, A. J. Kalyani, T. Mujtaba, and M. S. Rao, 1997, Neuron 19, 773-785). We now show that cells identical to rat NEPs, NRPs, and GRPs are present in mouse neural tubes and that immunoselection against cell surface markers E-NCAM and A2B5 can be used to isolate NRPs and GRPs, respectively. Restricted precursors similar to NRPs and GRPs can also be isolated from mouse embryonic stem cells (ES cells). ES cell-derived NRPs are E-NCAM immunoreactive, undergo self-renewal in defined medium, and differentiate into multiple neuronal phenotypes in mass culture. ES cells also generate A2B5-immunoreactive cells that are similar to E9 NEP-cell-derived GRPs and can differentiate into oligodendrocytes and astrocytes. Thus, lineage restricted precursors can be generated in vitro from cultured ES cells and these restricted precursors resemble those derived from mouse neural tubes. These results demonstrate the utility of using ES cells as a source of late embryonic precursor cells. View Publication

Basophils (Ba) and mast cells (MC) are important effector cells of inflammatory reactions. Both cell types derive from CD34(+) hematopoietic progenitors. However, little is known about the cell subsets that become committed to and give rise to Ba and/or MC. We have generated a monoclonal antibody (MoAb), 97A6, that specifically detects human Ba, MC (lung, skin), and their CD34(+) progenitors. Other mature hematopoietic cells (neutrophils, eosinophils, monocytes, lymphocytes, platelets) did not react with MoAb 97A6, and sorting of 97A6(+) peripheral blood (PB) and bone marrow (BM) cells resulted in an almost pure population (textgreater98%) of Ba. Approximately 1% of CD34(+) BM and PB cells was found to be 97A6(+). Culture of sorted CD34(+)97A6(+) BM cells in semisolid medium containing phytohemagglutinin-stimulated leukocyte supernatant for 16 days (multilineage assay) resulted in the formation of pure Ba colonies (10 of 40), Ba-eosinophil colonies (7 of 40), Ba-macrophage colonies (3 of 40), and multilineage Ba-eosinophil-macrophage and/or neutrophil colonies (12 of 40). In contrast, no Ba could be cultured from CD34(+)97A6(-) cells. Liquid culture of CD34(+) PB cells in the presence of 100 ng/mL interleukin (IL)-3 (Ba progenitor assay) resulted in an increase of 97A6(+) cells, starting from 1% of day-0 cells to almost 70% (basophils) after day 7. Culture of sorted BM CD34(+)97A6(+) cells in the presence of 100 ng/mL stem cell factor (SCF) for 35 days (mast cell progenitor assay) resulted in the growth of MC (textgreater30% on day 35). Anti-IgE-induced IgE receptor cross-linking on Ba for 15 minutes resulted in a 4-fold to 5-fold upregulation of 97A6 antigen expression. These data show that the 97A6-reactive antigen plays a role in basophil activation and is expressed on multipotent CD34(+) progenitors, MC progenitors, Ba progenitors, as well as on mature Ba and tissue MC. The lineage-specificity of MoAb 97A6 suggests that this novel marker may be a useful tool to isolate and analyze Ba/MC and their progenitors. View Publication

Adenosine is produced during inflammation and modulates different functional activities in macrophages. In murine bone marrow-derived macrophages, adenosine inhibits M-CSF-dependent proliferation with an IC50 of 45 microM. Only specific agonists that can activate A2B adenosine receptors such as 5'-N-ethylcarboxamidoadenosine, but not those active on A1 (N6-(R)-phenylisopropyladenosine), A2A ([p-(2-carbonylethyl)phenylethylamino]-5'-N-ethylcarboxamido adenosine), or A3 (N6-(3-iodobenzyl)adenosine-5'-N-methyluronamide) receptors, induce the generation of cAMP and modulate macrophage proliferation. This suggests that adenosine regulates macrophage proliferation by interacting with the A2B receptor and subsequently inducing the production of cAMP. In fact, both 8-Br-cAMP (IC50 85 microM) and forskolin (IC50 7 microM) inhibit macrophage proliferation. Moreover, the inhibition of adenylyl cyclase and protein kinase A blocks the inhibitory effect of adenosine and its analogues on macrophage proliferation. Adenosine causes an arrest of macrophages at the G1 phase of the cell cycle without altering the activation of the extracellular-regulated protein kinase pathway. The treatment of macrophages with adenosine induces the expression of p27kip-1, a G1 cyclin-dependent kinase inhibitor, in a protein kinase A-dependent way. Moreover, the involvement of p27kip-1 in the adenosine inhibition of macrophage proliferation was confirmed using macrophages from mice with a disrupted p27kip-1 gene. These results demonstrate that adenosine inhibits macrophage proliferation through a mechanism that involves binding to A2B adenosine receptor, the generation of cAMP, and the induction of p27kip-1 expression. View Publication

Predictive in vitro hematotoxicity assays using human cells will provide estimation of tolerable level and aid considerably the development of agents with greater therapeutic activity and less toxicity. Human hematopoietic cells can be derived from three sources: human bone marrow by sternal or femoral aspiration, mobilized peripheral blood, or umbilical cord blood samples collected from placentas after deliveries. Because of the difficulties to have a continuous supply of bone marrow cells from normal human donors and the related ethical problems, we performed a study to compare the sensitivity of human bone marrow cells (h-BMC) and human cord blood cells (h-CBC) to chemicals in order to confirm if h-CBC can readily replace bone marrow cells in checking the sensitivity of GM-CFU progenitors to drugs as preliminarily reported in literature. Our results showed that the prediction of IC50 values in human model is quite similar by using h-BMC or h-CBC. On the contrary, the type of medium influenced in a significant way the ICs determination of some drugs. View Publication

Regulatory mechanisms governing adhesion of hematopoietic progenitor cells to the stromal nische are poorly understood. Growth factors such as stem cell factor (SCF), granulocyte-macrophage colony-stimulating factor, and thrombopoietin were reported to upregulate the adhesion of hematopoietic progenitors to immobilized fibronectin through activation of integrin alpha4beta1 and alpha5beta1. Macrophage inflammatory protein (MIP)-1alpha is a C-C chemokine that suppresses colony formation by stem/progenitor cells in vitro. We asked if MIP-1alpha would modulate the adhesive phenotype of colony-forming cells (CFCs) obtained from healthy donor bone marrow (BM), cord blood (CB), and mobilized peripheral blood (mPB) CD34+ cells, in comparison with SCF, using immobilized fibronectin. SCF significantly increased the level of adhesion of CFCs from BM, CB, and mPB. On the other hand, MIP-1alpha significantly increased the level of adhesion of CFCs from BM and CB, but less so from mPB. The effects of MIP-1alpha were inhibited by blocking antibodies to integrin alpha4, alpha5, or beta1, and polymerization plus rearrangement of F-actin were observed in affected cells by labeling with rhodamine-conjugated phalloidine. These data indicate that the effect of MIP-1alpha on the adhesive phenotype of CFCs is mediated by modulation of the organization of integrin. The amount of MIP-1alpha receptor on mPB was less than for BM or CB, which may explain the distinct characteristics in the adhesive response induced by MIP-1alpha. We suggest that hematopoietic progenitor cells from different sources may be heterogeneous with respect to maturation, integrin affinity, MIP-1alpha receptor expression, and regulation of MIP-1alpha signaling. Our data indicate that MIP-1alpha may affect migration, homing, and mobilization of hematopoietic progenitors by modulating the adhesive phenotype of these cells. View Publication

Dietary flavonoid intake has been reported to be inversely related to mortality from coronary heart disease, and the anti-atherosclerotic effect of flavonoids is considered to be due probably to their antioxidant properties. Oxidation of low density lipoprotein (LDL) has been reported to be induced by the constituent cells of the arterial wall. Accordingly, we examined the effect of pretreatment with tea flavonoids, such as theaflavin digallate, on the ability of cells to oxidize LDL. Theaflavin digallate pretreatment of macrophages or endothelial cells reduced cell-mediated LDL oxidation in a concentration- (0-400 microM) and time- (0-4 hr) dependent manner. This inhibitory effect of flavonoids on cell-mediated LDL oxidation was in the order of theaflavin digallate textgreater theaflavin textgreater or = epigallocatechin gallate textgreater epigallocatechin textgreater gallic acid. Further, we investigated the mechanisms by which flavonoids inhibited cell-mediated LDL oxidation using macrophages and theaflavin digallate. Theaflavin digallate pretreatment decreased superoxide production of macrophages and chelated iron ions significantly. These results suggest that tea flavonoids attenuate the ability of the cell to oxidize LDL, probably by reducing superoxide production in cells and chelating iron ions. View Publication

The molecular and cellular requirements for the development of different populations of human dendritic cells (DC) were studied. Conditions were defined that support DC production from lymphoid progenitors but that fail to induce DC formation from peripheral monocytes. The production of these lymphoid-related DC was severely blocked when hematopoietic progenitors overexpressed Ik7, a mutant dominant-negative Ikaros protein. In contrast, Ik7 did not block the formation of DC in conditions supporting the development of monocyte-derived DC. Furthermore, Ik7 did not block the formation of monocyte/macrophages and enhanced granulopoiesis. One of the molecular mechanisms mediated by Ik7 appears to be down-regulation of the flt3-receptor mRNA. Thus, distinct signals control the formation of DC demonstrating that some aspects of DC diversity are determined in part by distinct molecular cues at the hematopoietic level. (Blood. 2000;95:128-137) View Publication

We have used a murine retrovirus vector containing an enhanced green fluorescent protein complimentary DNA (EGFP cDNA) to dynamically follow vector-expressing cells in the peripheral blood (PB) of transplanted rhesus macaques. Cytokine mobilized CD34(+) cells were transduced with an amphotropic vector that expressed EGFP and a dihydrofolate reductase cDNA under control of the murine stem cell virus promoter. The transduction protocol used the CH-296 recombinant human fibronectin fragment and relatively high concentrations of the flt-3 ligand and stem cell factor. Following transplantation of the transduced cells, up to 55% EGFP-expressing granulocytes were obtained in the peripheral circulation during the early posttransplant period. This level of myeloid marking, however, decreased to 0.1% or lower within 2 weeks. In contrast, EGFP expression in PB lymphocytes rose from 2%-5% shortly following transplantation to 10% or greater by week 5. After 10 weeks, the level of expression in PB lymphocytes continued to remain at 3%-5% as measured by both flow cytometry and Southern blot analysis, and EGFP expression was observed in CD4(+), CD8(+), CD20(+), and CD16/56(+) lymphocyte subsets. EGFP expression was only transiently detected in red blood cells and platelets soon after transplantation. Such sustained levels of lymphocyte marking may be therapeutic in a number of human gene therapy applications that require targeting of the lymphoid compartment. The transient appearance of EGFP(+) myeloid cells suggests that transduction of a lineage-restricted myeloid progenitor capable of short-term engraftment was obtained with this protocol. (Blood. 2000;95:445-452) View Publication

Stable cell lines that individually express the eight known human prostanoid receptors (EP(1), EP(2), EP(3), EP(4), DP, FP, IP and TP) have been established using human embryonic kidney (HEK) 293(EBNA) cells. These recombinant cell lines have been employed in radioligand binding assays to determine the equilibrium inhibitor constants of known prostanoid receptor ligands at these eight receptors. This has allowed, for the first time, an assessment of the affinity and selectivity of several novel compounds at the individual human prostanoid receptors. This information should facilitate interpretation of pharmacological studies that employ these ligands as tools to study human tissues and cell lines and should, therefore, result in a greater understanding of prostanoid receptor biology. View Publication

The Dishevelled (Dvl) gene family encodes cytoplasmic proteins that are necessary for Wnt signal transduction. Utilizing the yeast two-hybrid system, we identified protein phosphatase 2Calpha (PP2C) as a Dvl-PDZ domain-interacting protein. PP2C exists in a complex with Dvl, beta-catenin, and Axin, a negative regulator of Wnt signaling. In a Wnt-responsive LEF-1 reporter gene assay, expression of PP2C activates transcription and also elicits a synergistic response with beta-catenin and Wnt-1. In addition, PP2C expression relieves Axin-mediated repression of LEF-1-dependent transcription. PP2C utilizes Axin as a substrate both in vitro and in vivo and decreases its half-life. These results indicate that PP2C is a positive regulator of Wnt signal transduction and mediates its effects through the dephosphorylation of Axin. View Publication

We studied the suitability of collagen-based semisolid medium for assay of endogenous erythroid colony formation performed in myeloproliferative disorders. Bone marrow (BM) mononuclear cells (MNC) from 103 patients suspected of having polycythemia vera (PV, 76 patients) or essential thrombocythemia (ET, 27 patients) were grown in collagen-based, serum-free, cytokine-free semisolid medium. Colony analysis at day 8 or 10 showed that this collagen assay is specific, as endogenous growth of erythroid colonies was never observed in cultures of 16 healthy donors and 6 chronic myelogenous leukemia (CML) patients. Endogenous erythroid colony formation was observed in 53.3% of patients suspected of PV, with only 15.4% of positive cultures for patients with 1 minor PV criterion and 72% (p = 0.009) of positive cultures for patients with textgreater or =2 minor or 1 major PV criterion. Similarly, endogenous growth of erythroid colonies was found in 44.4% of patients suspected of ET, with 31.6% of positive cultures for patients with 1 ET criterion versus 75% for patients with textgreater or =2 ET criteria. In addition, we found that in collagen gels, tests of erythropoietin (EPO) hypersensitivity in the presence of 0.01 or 0.05 U/ml of EPO and tests of endogenous colony-forming units-megakaryocyte (CFU-MK) formation cannot be used to detect PV or ET, as these tests were positive for, respectively, 21.4% and 50% of healthy donors and 83% and 50% of CML patients. A retrospective analysis suggests that collagen assays are more sensitive than methylcellulose assays to assess endogenous growth of erythroid colonies. In summary, serum-free collagen-based colony assays are simple and reliable assays of endogenous growth of erythroid colonies in myeloproliferative diseases. They also appear to be more sensitive than methylcellulose-based assays. View Publication

Retinoic acid derivatives (retinoids) exert their pleiotropic effects on cell development through specific nuclear receptors, the retinoic acid receptors and retinoid X receptors. Despite recent progress in understanding the cellular and molecular mechanisms of retinoid activity, it is unknown which of the retinoid receptor pathways are involved in the specific processes of sebocyte growth and development. In this study, we investigated the roles of specific retinoid receptors in sebocyte growth and differentiation, by testing the effects of selective retinoic acid receptor and retinoid X receptor ligands at concentrations between 10-10 M and 10-6 M in a primary rat preputial cell monolayer culture system. Cell growth was determined by number of cells and colonies, and cell differentiation by analysis of lipid-forming colonies. All-trans retinoic acid and selective retinoic acid receptor agonists (CD271 = adapalene, an RAR-beta,gamma agonist; CD2043 = retinoic acid receptor pan-agonist; and CD336 = Am580, an RAR-alpha agonist) caused significant decreases in numbers of cells, colonies, and lipid-forming colonies, but with an exception at high doses of all-trans retinoic acid (10-6 M), with which only a small number of colonies grew but they became twice as differentiated as controls (42.2 +/- 4.0% vs 22.6 +/- 2.7%, mean +/- SEM, lipid-forming colonies, p textless 0.01). Furthermore, the RAR-beta,gamma antagonist CD2665 antagonized the suppressive effects of all-trans retinoic acid, adapalene, and CD2043 on both cell growth and differentiation. In contrast, the retinoid X receptor agonist CD2809 increased cell growth slightly and lipid-forming colonies dramatically in a clear dose-related manner to a maximum of 73.7% +/- 6.7% at 10-6 M (p textless 0. 001). Our data suggest that retinoic acid receptors and retinoid X receptors differ in their roles in sebocyte growth and differentiation: (i) retinoic acid receptors, especially the beta and/or gamma subtypes, mediate both the antiproliferative and antidifferentiative effects of retinoids; (ii) retinoid X receptors mediate prominent differentiative and weak proliferative effects; (iii) the antiproliferative and antidifferentiative effects of all-trans retinoic acid are probably mediated by retinoic acid receptors, whereas its differentiative effect at high dose may be mediated by retinoid X receptors via all-trans retinoic acid metabolism to 9-cis retinoic acid, the natural ligand of retinoid X receptors. View Publication

The small heat-shock protein HSP25 is expressed in the heart early during development, and although multiple roles for HSP25 have been proposed, its specific role during development and differentiation is not known. P19 is an embryonal carcinoma cell line which can be induced to differentiate in vitro into either cardiomyocytes or neurons. We have used P19 to examine the role of HSP25 in differentiation. We found that HSP25 expression is strongly increased in P19 cardiomyocytes. Antisense HSP25 expression reduced the extent of cardiomyocyte differentiation and resulted in reduced expression of cardiac actin and the intermediate filament desmin and reduced level of cardiac mRNAs. Thus, HSP25 is necessary for differentiation of P19 into cardiomyocytes. In contrast, P19 neurons did not express HSP25 and antisense HSP25 expression had no effect on neuronal differentiation. The phosphorylation of HSP25 by the p38/SAPK2 pathway is known to be important for certain of its functions. Inhibition of this pathway by the specific inhibitor SB203580 prevented cardiomyocyte differentiation of P19 cells. In contrast, PD90589, which inhibits the ERK1/2 pathway, had no effect. Surprisingly, cardiogenesis was only sensitive to SB203580 during the first 2 days of differentiation, before HSP25 expression increases. In contrast to the effect of antisense HSP25, SB203580 reduced the level of expression of the mesodermal marker Brachyury-T during differentiation. Therefore, we propose that the p38 pathway acts on an essential target during early cardiogenesis. Once this initial step is complete, HSP25 is necessary for the functional differentiation of P19 cardiomyocytes, but its phosphorylation by p38/SAPK2 is not required. View Publication

We report here the cloning, expression, and characterization of human PDE11A1, a member of a distinct cyclic nucleotide phosphodiesterase (PDE) family. PDE11A exhibits textless/=50% amino acid identity with the catalytic domains of all other PDEs, being most similar to PDE5, and has distinct biochemical properties. The human PDE11A1 cDNA isolated contains a complete open reading frame encoding a 490-amino acid enzyme with a predicted molecular mass of 55,786 Da. At the N terminus PDE11A1 has a single GAF domain homologous to that found in other signaling molecules, including PDE2, PDE5, PDE6, and PDE10, which constitutes a potential allosteric binding site for cGMP or another small ligand. Tissue distribution studies indicate that PDE11A mRNA occurs at highest levels in skeletal muscle, prostate, kidney, liver, pituitary, and salivary glands and testis. PDE11A is expressed as at least three major transcripts of approximately 10.5, approximately 8.5, and approximately 6.0 kb, thus suggesting the existence of multiple subtypes. This possibility is further supported by the detection of three distinct proteins of approximately 78, approximately 65, and approximately 56 kDa by Western blotting of human tissues for PDE11A isoforms. Recombinant human PDE11A1 hydrolyzes both cGMP and cAMP with K(m) values of 0.52 microM and 1.04 microM, respectively, and similar V(max) values. Therefore, PDE11A represents a dual-substrate PDE that may regulate both cGMP and cAMP under physiological conditions. PDE11A is sensitive to the nonselective PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX) as well as zaprinast and dipyridamole, inhibitors that are generally considered relatively specific for the cGMP-selective PDEs, with IC(50) values of 49.8 microM, 12.0 microM, and 0.37 microM, respectively. View Publication

Estrogens as well as some antiestrogens have been shown to prevent bone loss in postmenopausal women. These compounds seem to inhibit bone resorption, but their anabolic effects have been less explored. In this study, bone marrow cultures were used to compare the effect of 17beta-estradiol (E2), and two triphenylethylene derivatives, tamoxifen (TAM), and FC1271a, and a benzothiophene derivative raloxifene (RAL) on differentiation of osteoblasts. All enhanced osteoblastic differentiation of 21-day cultures as indicated by increased mineralization and bone nodule formation. All, except RAL, stimulated cell proliferation during the first 6 days of the culture. However, in the presence of RAL the content of total protein was increased in 13-day cultures. SDS-PAGE and autoradiography of [14C]-proline labeled proteins revealed elevated level of the newly synthesized collagen type I. The pure antiestrogen ICI 182,780 abolished the increase of the specific activity of alkaline phosphatase by E2, TAM, and FC1271a but not the effect of RAL on protein synthesis. Our results show that E2 as well as TAM, FC1271a, and RAL stimulate bone formation in vitro but the mechanism of the anabolic action of RAL in bone clearly differs from that of E2, TAM, and FC1271a. View Publication

Hematologic malignancies such as acute and chronic myeloid leukemia are characterized by the malignant transformation of immature CD34(+) progenitor cells. Transformation is associated with elevated expression of the Wilm's tumor gene encoded transcription factor (WT1). Here we demonstrate that WT1 can serve as a target for cytotoxic T lymphocytes (CTL) with exquisite specificity for leukemic progenitor cells. HLA-A0201- restricted CTL specific for WT1 kill leukemia cell lines and inhibit colony formation by transformed CD34(+) progenitor cells isolated from patients with chronic myeloid leukemia (CML), whereas colony formation by normal CD34(+) progenitor cells is unaffected. Thus, the tissue-specific transcription factor WT1 is an ideal target for CTL-mediated purging of leukemic progenitor cells in vitro and for antigen-specific therapy of leukemia and other WT1-expressing malignancies in vivo. View Publication

Adult human mesenchymal stem cells are primary, multipotent cells capable of differentiating to osteocytic, chondrocytic, and adipocytic lineages when stimulated under appropriate conditions. To characterize the molecular mechanisms that regulate osteogenic differentiation, we examined the contribution of mitogen-activated protein kinase family members, ERK, JNK, and p38. Treatment of these stem cells with osteogenic supplements resulted in a sustained phase of ERK activation from day 7 to day 11 that coincided with differentiation, before decreasing to basal levels. Activation of JNK occurred much later (day 13 to day 17) in the osteogenic differentiation process. This JNK activation was associated with extracellular matrix synthesis and increased calcium deposition, the two hallmarks of bone formation. Inhibition of ERK activation by PD98059, a specific inhibitor of the ERK signaling pathway, blocked the osteogenic differentiation in a dose-dependent manner, as did transfection with a dominant negative form of MAP kinase kinase (MEK-1). Significantly, the blockage of osteogenic differentiation resulted in the adipogenic differentiation of the stem cells and the expression of adipose-specific mRNAs peroxisome proliferator-activated receptor gamma2, aP2, and lipoprotein lipase. These observations provide a potential mechanism involving MAP kinase activation in osteogenic differentiation of adult stem cells and suggest that commitment of hMSCs into osteogenic or adipogenic lineages is governed by activation or inhibition of ERK, respectively. View Publication

Potent inhibition of Janus kinase 3 was found for a series of naphthyl(beta-aminoethyl)ketones (e.g. 7, pIC50 = 7.1+/-0.3). Further studies indicated that these compounds fragment in less than 1 h by retro-Michael reaction in the Jak3 in vitro ELISA assay procedure. The breakdown product of 7, 2-naphthylvinyl ketone (22, pIC50 = 6.8+/-0.3) showed very similar inhibitory activity to 7. Compounds 7 (in neutral buffer) and 22 will be useful pharmacological tools for the investigation of the Janus tyrosine kinase Jak3. View Publication

Cell fate during development is defined by transcription factors that act as molecular switches to activate or repress specific gene expression programmes. The POU transcription factor Oct-3/4 (encoded by Pou5f1) is a candidate regulator in pluripotent and germline cells and is essential for the initial formation of a pluripotent founder cell population in the mammalian embryo. Here we use conditional expression and repression in embryonic stem (ES) cells to determine requirements for Oct-3/4 in the maintenance of developmental potency. Although transcriptional determination has usually been considered as a binary on-off control system, we found that the precise level of Oct-3/4 governs three distinct fates of ES cells. A less than twofold increase in expression causes differentiation into primitive endoderm and mesoderm. In contrast, repression of Oct-3/4 induces loss of pluripotency and dedifferentiation to trophectoderm. Thus a critical amount of Oct-3/4 is required to sustain stem-cell self-renewal, and up- or downregulation induce divergent developmental programmes. Our findings establish a role for Oct-3/4 as a master regulator of pluripotency that controls lineage commitment and illustrate the sophistication of critical transcriptional regulators and the consequent importance of quantitative analyses. View Publication

U937 monocytic cells are shown here to express a range of PDE4, cAMP-specific phosphodiesterase (PDE) isoenzymes: the long isoenzymes, PDE4A4, PDE4D5 and PDE4D3, plus the short isoenzyme, PDE4B2. These isoenzymes provide around 76% of the total cAMP PDE activity of U937 cells. The specific activities of the total PDE4A, PDE4B and PDE4D activities were 0.63+/-0.09, 8.8+/-0.2 and 34.4+/-2.9 pmol/min per mg of protein respectively. The PDE4 selective inhibitor, rolipram, inhibited immunopurified PDE4B and PDE4D activities similarly, with IC(50) values of approx. 130 nM and 240 nM respectively. In contrast, rolipram inhibited immunopurified PDE4A activity with a dramatically lower IC(50) value of around 3 nM. Rolipram increased phosphorylation of cAMP-response-element-binding protein (CREB) in U937 cells in a dose-dependent fashion, which implied the presence of both high affinity (IC(50) value approx. 1 nM) and low affinity (IC(50) value approx. 120 nM) components. Rolipram dose-dependently inhibited the interferon-gamma (IFN-gamma)-stimulated phosphorylation of p38 mitogen-activated protein (MAP) kinase in a simple monotonic fashion with an IC(50) value of approx. 290 nM. On this basis, it is suggested that rolipram inhibition of PDE4A4 is involved in regulating CREB phosphorylation but not IFN-gamma-stimulated p38 MAP kinase phosphorylation. PDE4A4 was also selectively activated by challenge of U937 cells with either bacterial lipopolysaccharide (LPS) or IFN-gamma through a process which was attenuated by both wortmannin and rapamycin. It is proposed that the PDE4A4 isoform is involved in compartmentalized cAMP signalling responses in U937 monocytes. View Publication

Green tea has shown remarkable anti-inflammatory and cancer chemopreventive effects in many animal tumor bioassays, cell culture systems, and epidemiological studies. Many of these biological effects of green tea are mediated by epigallocatechin 3-gallate (EGCG), the major polyphenol present therein. We have earlier shown that EGCG treatment results in apoptosis of several cancer cells, but not of normal cells (J. Natl. Cancer Inst. 89, 1881-1886 (1997)). The mechanism of this differential response of EGCG is not known. In this study, we investigated the involvement of NF-kappaB during these differential responses of EGCG. EGCG treatment resulted in a dose-dependent (i) inhibition of cell growth, (ii) G0/G1-phase arrest of the cell cycle, and (iii) induction of apoptosis in human epidermoid carcinoma (A431) cells, but not in normal human epidermal keratinocytes (NHEK). Electromobility shift assay revealed that EGCG (10-80 microM) treatment results in lowering of NF-kappaB levels in both the cytoplasm and nucleus in a dose-dependent manner in both A431 cells and NHEK, albeit at different concentrations. EGCG treatment was found to result in a dose-based differential inhibition of TNF-alpha- and LPS-mediated activation of NF-kappaB in these cells. The inhibition of NF-kappaB constitutive expression and activation in NHEK was observed only at high concentrations. The immunoblot analysis also demonstrated a similar pattern of inhibition of the constitutive expression as well as activation of NF-kappaB/p65 nuclear protein. This inhibition of TNF-alpha-caused NF-kappaB activation was mediated via the phosphorylative degradation of its inhibitory protein IkappaBalpha. Taken together, EGCG was found to impart differential dose-based NF-kappaB inhibitory response in cancer cells vs normal cells; i.e., EGCG-mediated inhibition of NF-kappaB constitutive expression and activation was found to occur at much higher dose of EGCG in NHEK as compared to A431 cells. This study suggests that EGCG-caused cell cycle deregulation and apoptosis of cancer cells may be mediated through NF-kappaB inhibition. View Publication

Y-27632 [(+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide++ + dihydrochloride] is widely used as a specific inhibitor of the Rho-associated coiled-coil forming protein serine/threonine kinase (ROCK) family of protein kinases. This study examined the inhibition mechanism and profile of actions of Y-27632 and a related compound, Y-30141 [(+)-(R)-trans- 4-(1-aminoethyl)-N-(1H-pyrrolo[2, 3-b]pyridin-4-yl)cyclohexan-ecarboxamide dihydrochloride]. Y-27632 and Y-30141 inhibited the kinase activity of both ROCK-I and ROCK-II in vitro, and this inhibition was reversed by ATP in a competitive manner. This suggests that these compounds inhibit the kinases by binding to the catalytic site. Their affinities for ROCK kinases as determined by K(i) values were at least 20 to 30 times higher than those for two other Rho effector kinases, citron kinase and protein kinase PKN. [(3)H]Y-30141 was taken up by cells in a temperature- and time-dependent and saturable manner, and this uptake was competed with unlabeled Y-27632. No concentrated accumulation was found, suggesting that the uptake is a carrier-mediated facilitated diffusion. Y-27632 abolished stress fibers in Swiss 3T3 cells at 10 microM, but the G(1)-S phase transition of the cell cycle and cytokinesis were little affected at this concentration. Y-30141 was 10 times more potent than Y-27632 in inhibiting the kinase activity and stress fiber formation, and it caused significant delay in the G(1)-S transition and inhibition of cytokinesis at 10 microM. View Publication

Protein kinase CK2 (formerly casein kinase II) is a serine/threonine kinase overexpressed in many human tumors, transformed cell lines, and rapidly proliferating tissues. Recent data have shown that many cancers involve inappropriate reactivation of Wnt signaling through ectopic expression of Wnts themselves, as has been seen in a number of human breast cancers, or through mutation of intermediates in the Wnt pathway, such as adenomatous polyposis coli or beta-catenin, as described in colon and other cancers. Wnts are secreted factors that are important in embryonic development, but overexpression of certain Wnts, such as Wnt-1, leads to proliferation and transformation of cells. We report that upon stable transfection of Wnt-1 into the mouse mammary epithelial cell line C57MG, morphological changes and increased proliferation are accompanied by increased levels of CK2, as well as of beta-catenin. CK2 and beta-catenin co-precipitate with the Dvl proteins, which are Wnt signaling intermediates. A major phosphoprotein of the size of beta-catenin appears in in vitro kinase reactions performed on the Dvl immunoprecipitates. In vitro translated beta-catenin, Dvl-2, and Dvl-3 are phosphorylated by CK2. The selective CK2 inhibitor apigenin blocks proliferation of Wnt-1-transfected cells, abrogates phosphorylation of beta-catenin, and reduces beta-catenin and Dvl protein levels. These results demonstrate that endogenous CK2 is a positive regulator of Wnt signaling and growth of mammary epithelial cells. View Publication

BACKGROUND: Transforming growth factor beta (TGF-beta) plays an important role in skeletal remodelling. However, few studies have examined its effects on cultured human osteoblasts. Our aim is to characterise the biological effects of TGF-beta1 on human osteoblasts and to examine the interaction between TGF-beta1 and calcitriol. DESIGN: In vitro study employing two models of normal human osteoblasts: human bone marrow stromal cells [hMS/(OB)] containing osteoprogenitor cells and trabecular bone osteoblasts (hOB), which are mature osteoblasts. A reverse-transcriptase-polymerase-chain-reaction assay was employed to measure steady state mRNA levels of TGF-beta(s) isoforms and receptors. Effects of short-term treatment of TGF-beta1 on osteoblast proliferation and differentiation markers were assessed. The effect of cotreatment of calcitriol (10-8 M) and TGF-beta1 on osteoblast differentiation was also determined. RESULTS: Both hMS(OB) and hOB cells expressed mRNA transcripts of TGF-beta1, TGF-beta2, TGF-beta 3, TGF-beta type I and type II receptors. TGF-beta 1 stimulated osteoblast proliferation in hMS(OB) and in hOB cultures. In hOB cultures, TGF-beta1 stimulated AP production and cotreatment with calcitriol induced a synergistic increase in AP levels to 250 +/- 61% of calcitriol-treated controls. Effects of TGF-beta1 and calcitriol were less pronounced in hMS(OB) cultures. TGF-beta1 inhibited collagen type I production in hMS(OB) cells and these effects were abolished in presence of calcitriol. In presence of calcitriol, TGF-beta1 increased collagen type I production in hOB cells. In both hOB and hMS(OB) cultures, TGF-beta1 inhibited osteocalcin production. CONCLUSIONS: TGF-beta increases osteoblastic cell proliferation irrespective of the differentiation state. In presence of calcitriol, it initiates osteoblast cell differentiation and matrix formation. As TGF-beta inhibits osteocalcin production, other factors are necessary for inducing terminal differentiation of osteoblasts. The observed effects of TGF-beta on human osteoblasts in vitro may represent important regulatory steps in controlling osteoblast cell proliferation and differentiation in vivo. View Publication

The zinc finger protein GATA-1 functions in a concentration-dependent fashion to activate the transcription of erythroid and megakaryocytic genes. Less is understood, however, regarding factors that regulate the GATA-1 gene. Presently elements within intron 1 are shown to markedly affect its erythroid-restricted transcription. Within a full-length 6. 8-kilobase GATA-1 gene construct (G6.8-Luc) the deletion of a central subdomain of intron 1 inhibited transcription textgreater/=10-fold in transiently transfected erythroid SKT6 cells, and likewise inhibited high-level transcription in erythroid FDCW2ER-GATA1 cells. In parental myeloid FDCER cells, however, low-level transcription was largely unaffected by intron 1 deletions. Within intron 1, repeated GATA and Ap1 consensus elements in a central region are described which when linked directly to reporter cassettes promote transcription in erythroid SKT6 and FDCER-GATA1 cells at high rates. Moreover, GATA-1 activated transcription from this subdomain in 293 cells, and in SKT6 cells this subdomain footprinted in vivo. For stably integrated GFP reporter constructs in erythroid SKT6 cells, corroborating results were obtained. Deletion of intronic GATA and Ap1 motifs abrogated the activity of G6.8-pEGFP; activity was decreased by 43 and 56%, respectively, by the deletion of either motif; and the above 1800-base pair region of intron 1 per se was transcribed at rates uniformly greater than G6.8-pEGFP. Also described is the differential utilization of exons 1a and 1b among primary erythromegakaryocytic and myeloid cells. View Publication

OBJECTIVE: +HOX genes are expressed in the hematopoietic system and increasing data point to their involvement in the control of proliferation and/or differentiation. Genes belonging to the C cluster are preferentially expressed in developing and differentiated lymphoid lineages. However, recent studies demonstrated, by RT-PCR, that the HOXC4 gene is also actively transcribed in the most undifferentiated hematopoietic cells (CD34(+)38(low)) and in more mature myeloid and erythroid progenitors. We evaluated the expression of HOXC4 protein on human CD34(+) cells and the in vitro effect of its overexpression on proliferation and differentiation. MATERIALS AND METHODS: We assessed the expression of HOXC4 on human CD34(+) cells using a polyclonal antibody raised against the C-terminal portion of the protein expressed using the baculovirus system. Overexpression of HOXC4 in human CD34(+) cells was obtained by retroviral gene transfer; its effect on clonogenic (CFU-GM, BFU-E, and CFU-GEMM) and early progenitors (LTC-IC) was evaluated. RESULTS: The HOXC4 protein is indeed expressed in human CD34(+) cells, and its overexpression in human CD34(+) cells increases the proliferation potential of clonogenic and early progenitors. CFU-GM showed a median threefold expansion (range: 1.1-19.4; p textless 0.002) compared with control transduced with the vector alone. The increment of BFU-E was higher (median ninefold, range 2.5-35; p textless 0. 0009) and erythroid colonies presented a larger size with normal morphology. An even more marked effect was observed on LTC-IC (median 13, onefold; range 4.1-102.1, p textless 0.0001). CONCLUSION: We demonstrate that HOXC4 is expressed in CD34(+) cells and that its overexpression induces an in vitro expansion of committed as well as very early hematopoietic progenitors. The most striking effect was obtained on LTC-IC with an expansion of 13.1-fold. The enforced expression of HOXC4 induced a significant increase (p textless 0.009) in the number of erythroid colonies compared with CFU-GM, although without perturbing, at least in vitro, the maturation program of the cells. On the other hand, the effect of the gene overexpression did not induce any skewing in the colony types derived from the myeloid lineage. View Publication