参考文献

Neural stem cells (NSCs) are capable of giving rise to neurons,glia,and astrocytes. Although self-renewal and differentiation in NSCs are regulated by many genes,such as Notch and Numb,little is known about the role of defective genes on the self-renewal and differentiation of NSCs from developing brain. The Niemann-Pick type C1 (NPC1) disease is a neurodegenerative disease caused by a mutation of the NPC1 gene that affects the function of the NPC1 protein. The ability of NSC self-renewal and differentiation was investigated using a model of NPC1 disease. The NPC1 disorder significantly affected the self-renewal ability of NSCs,as well as the differentiation. NSCs from NPC1-/- mice showed impaired self-renewal ability compared with the NPC1+/+ mice. These alterations were accompanied by the enhanced activity of p38 mitogen-activated protein kinases (MAPKs). Further,the specific p38 MAPK inhibitor SB202190 improved the self-renewal ability of NSCs from NPC-/- mice. This indicated that the NPC1 deficiency can lead to lack of self-renewal and altered differentiation of NSCs mediated by the activation of p38 MAPK,impairing the generation of neurospheres from NPC1-/- Thus,the NPC1 gene may play a crucial role in NSC self-renewal associated with p38 MAPK. View Publication

The homeobox gene Hoxa-9 is normally expressed in primitive bone marrow cells,and overexpression of Hoxa-9 markedly expands hematopoietic stem cells,suggesting a function in early hematopoiesis. We present evidence for major functional defects in Hoxa-9-/- hematopoietic stem cells. Hoxa-9-/- marrow cells have normal numbers of immunophenotypic stem cells (Lin(-)c-kit(+)flk-2(-)Sca-1+ [KLFS] cells). However,sublethally irradiated Hoxa-9-/- mice develop persistent pancytopenia,indicating unusual sensitivity to ionizing irradiation. In competitive transplantation assays,Hoxa-9-/- cells showed an 8-fold reduction in multilineage long-term repopulating ability,a defect not seen in marrow cells deficient for the adjacent Hoxa-10 gene. Single-cell cultures of KLFS cells showed a 4-fold reduction in large high-proliferation potential colonies. In liquid cultures,Hoxa-9-deficient Lin(-)Sca-1(+) cells showed slowed proliferation (a 5-fold reduction in cell numbers at day 8) and delayed emergence of committed progenitors (a 5-fold decrease in colony-forming cells). Slowing of proliferation was accompanied by a delay in myeloid maturation,with a decrease in Gr-1hiMac-1hi cells at the end of the culture. Retroviral transduction with a Hoxa-9 expression vector dramatically enhanced the cytokine-driven proliferation and in vivo engraftment of Hoxa-9-/- marrow cells. Hoxa-9 appears to be specifically required for normal hematopoietic stem cell function both in vitro and in vivo. View Publication

Valproic acid (VPA) has been used as an anticonvulsant agent for the treatment of epilepsy,as well as a mood stabilizer for the treatment of bipolar disorder,for several decades. The mechanism of action for these effects remains to be elucidated and is most likely multifactorial. Recently,VPA has been reported to inhibit histone deacetylase (HDAC) and HDAC has been reported to play roles in differentiation of mammalian cells. In this study,the effects of HDAC inhibitors on differentiation and proliferation of human adipose tissue-derived stromal cells (hADSC) and bone marrow stromal cells (hBMSC) were determined. VPA increased osteogenic differentiation in a dose dependent manner. The pretreatment of VPA before induction of differentiation also showed stimulatory effects on osteogenic differentiation of hMSC. Trichostatin A (TSA),another HDAC inhibitor,also increased osteogenic differentiation,whereas valpromide (VPM),a structural analog of VPA which does not possess HDAC inhibitory effects,did not show any effect on osteogenic differentiation on hADSC. RT-PCR and Real-time PCR analysis revealed that VPA treatment increased osterix,osteopontin,BMP-2,and Runx2 expression. The addition of noggin inhibited VPA-induced potentiation of osteogenic differentiation. VPA inhibited proliferation of hADSC and hBMSC. Our results suggest that VPA enhance osteogenic differentiation,probably due to inhibition of HDAC,and could be useful for in vivo bone engineering using hMSC. View Publication

BACKGROUND: Previous studies have shown that patients with Bcr-Abl-positive acute lymphoblastic leukemia (ALL) either have primary disease that is refractory to imatinib mesylate or develop disease recurrence after an initial response. METHODS: The authors investigated the effects of a newly designed Bcr-Abl inhibitor,AMN107,by comparing its in vitro inhibitory potency on p190 Bcr-Abl ALL cell lines with that of imatinib. RESULTS: In two Philadelphia (Ph)-positive ALL cell lines,AMN107 was found to be 30-40 times more potent than imatinib in inhibiting cellular proliferation. AMN107 was also more effective than imatinib in inhibiting phosphorylation of p190 Bcr-Abl tyrosine kinase in cell lines and primary ALL cells. The inhibition of cellular proliferation was associated with the induction of apoptosis in only one of the cell lines. No activity was observed in cell lines lacking the BCR-ABL genotype. CONCLUSIONS: The results of the current study suggest the superior potency of AMN107 compared with imatinib in Ph-positive ALL and support clinical trials of AMN107 in patients with Ph-positive ALL. View Publication

Selective and regulatable expansion of transduced cells could augment gene therapy for many disorders. The activation of modified growth factor receptors via synthetic chemical inducers of dimerization allows for the coordinated growth of transduced cells. This system can also provide information on specific receptor-mediated signaling without interference from other family members. Although several receptor subunits have been investigated in this context,little is known about the precise molecular events associated with dimerizer-initiated signaling. We have constructed and expressed an AP20187-regulated KDR chimeric receptor in human TF1 cells and analyzed activation of this gene switch using functional,biochemical,and microarray analyses. When deprived of natural ligands,GM-CSF,interleukin-3,or erythropoietin,AP20187 prevented apoptosis of transduced TF1 cells,induced dose-dependent proliferation,and supported long-term growth. In addition,AP20187 stimulation activated the signaling molecules associated with mitogen-activated protein kinase and phosphatidyl-inositol 3-kinase/Akt pathways. Microarray analysis determined that a number of transcripts involved in a variety of cellular processes were differentially expressed. Notably,mRNAs affiliated with heat stress,including Hsp70 and Hsp105,were up-regulated. Functional assays showed that Hsp70 and Hsp105 protected transduced TF1 cells from apoptosis and premature senescence,in part through regulation of Akt. These observations delineate specific roles for kinase insert domain-containing receptor,or KDR,signaling and suggest strategies to endow genetically modified cells with a survival advantage enabling the generation of adequate cell numbers for therapeutic outcomes. View Publication

Hoechst-effluxing cells (side population cells) are a rare subset of cells found in adult tissues that are highly enriched for stem and progenitor cell activity. To identify potential stem and progenitor cells during lung development,we generated gene expression profiles for CD45- and CD45+ side population cells in the embryonic day 17.5 lung. We found that side population cells comprise 1% of total embryonic day 17.5 lung cells (55% CD45+,45% CD45-). Gene profiling data demonstrated an overrepresentation of endothelial genes within the CD45- side population. We used expression of several distinct genes to identify two types of CD45- side population cells: 1) von Willebrand factor+/smooth muscle actin+ cells that reside in the muscular layer of select large vessels and 2) von Willebrand factor+/intercellular adhesion molecule+ cells that reside within the endothelial layer of select small vessels. Gene profiling of the CD45+ side population indicated an overrepresentation of genes associated with myeloid cell differentiation. Consistent with this,culturing CD45+ side population cells was associated with induction of mature dendritic markers (CD86). The microarray results suggested that expression of myeloperoxidase and proteinase-3 might be used to identify CD45+ side population cells. By immunohistochemistry,we found that myeloperoxidase+/proteinase-3+ cells represent a small subset of total CD45+ cells in the embryonic day 17.5 lung and that they reside in the mesenchyme and perivascular regions. This is the first detailed information regarding the phenotype and localization of side population cells in a developing organ. View Publication

HIV infection leads to a state of chronic immune activation and progressive deterioration in immune function,manifested most recognizably by the progressive depletion of CD4+ T cells. A substantial percentage of natural killer (NK) cells from patients with HIV infection are activated and express the natural cytotoxicity receptor (NCR) NKp44. Here we show that a cellular ligand for NKp44 (NKp44L) is expressed during HIV-1 infection and is correlated with both the progression of CD4+ T cell depletion and the increase of viral load. CD4+ T cells expressing this ligand are highly sensitive to the NK lysis activity mediated by NKp44+ NK cells. The expression of NKp44L is induced by the linear motif NH2-SWSNKS-COOH of the HIV-1 envelope gp41 protein. This highly conserved motif appears critical to the sharp increase in NK lysis of CD4+ T cells from HIV-infected patients. These studies strongly suggest that induction of NKp44L plays a key role in the lysis of CD4+ T cells by activated NK cells in HIV infection and consequently provide a framework for considering how HIV-1 may use NK cell immune surveillance to trigger CD4+ T cells. Understanding this mechanism may help to develop future therapeutic strategies and vaccines against HIV-1 infection. View Publication

To realize the full potential of targeted protein kinase inhibitors for the treatment of cancer,it is important to address the emergence of drug resistance in treated patients. Mutant forms of BCR-ABL,KIT,and the EGF receptor (EGFR) have been found that confer resistance to the drugs imatinib,gefitinib,and erlotinib. The mutations weaken or prevent drug binding,and interestingly,one of the most common sites of mutation in all three kinases is a highly conserved gatekeeper" threonine residue near the kinase active site. We have identified existing clinical compounds that bind and inhibit drug-resistant mutant variants of ABL� View Publication

Bisphosphonates are now the most widely used drugs for diseases associated with increased bone resorption,such as osteoporosis. Although bisphosphonates act directly on osteoclasts,and interfere with specific biochemical processes such as protein prenylation,their ability to adsorb to bone mineral also contributes to their potency and duration of action. The aim of the present study was to compare the binding affinities for hydroxyapatite (HAP) of 6 bisphosphonates currently used clinically and to determine the effects of these bisphosphonates on other mineral surface properties including zeta potential and interfacial tension. Affinity constants (K(L)) for the adsorption of bisphosphonates were calculated from kinetic studies on HAP crystal growth using a constant composition method at 37 degrees C and at physiological ionic strength (0.15 M). Under conditions likely to simulate bisphosphonate binding onto bone,there were significant differences in K(L) among the bisphosphonates for HAP growth (pH 7.4) with a rank order of zoledronate textgreater alendronate textgreater ibandronate textgreater risedronate textgreater etidronate textgreater clodronate. The measurements of zeta potential show that the crystal surface is modified by the adsorption of bisphosphonates in a manner best explained by molecular charges related to the protonation of their side-chain moieties,with risedronate showing substantial differences from alendronate,ibandronate,and zoledronate. The studies of the solid/liquid interfacial properties show additional differences among the bisphosphonates that may influence their mechanisms for binding and inhibiting crystal growth and dissolution. The observed differences in kinetic binding affinities,HAP zeta potentials,and interfacial tension are likely to contribute to the biological properties of the various bisphosphonates. In particular,these binding properties may contribute to differences in uptake and persistence in bone and the reversibility of effects. These properties,therefore,have potential clinical implications that may be important in understanding differences among potent bisphosphonates,such as the apparently more prolonged duration of action of alendronate and zoledronate compared with the more readily reversible effects of etidronate and risedronate. View Publication

Reduced-intensity conditioning regimens for transplant recipients have heightened awareness of immunologic resistance to allogeneic bone marrow transplants (BMT). Although T cell-mediated cytotoxicity has been assumed to play a role in the resistance against donor allogeneic hematopoietic stem and progenitor cell grafts,several studies have reported relatively unimpaired resistance by recipients who lack perforin,Fas ligand (FasL),and other cytotoxic mediators. This study compared the early kinetics of T cell-mediated resistance in B6 (H2b) cytotoxically normal versus deficient recipients after transplantation with major histocompatibility complex-matched,minor histocompatibility antigen (MiHA)-mismatched allogeneic marrow grafts. Wild-type B6 or cytotoxic double-deficient perforin-/-/ gld+/+ (B6-cdd) mice were sensitized against major histocompatibility complex-matched BALB.B or C3H.SW (H2b) MiHA and transplanted with a high dose (1 ?? 107) of T cell-depleted bone marrow. CD8 T memory cells were shown to be present in recipients before BMT,and anti-CD8 monoclonal antibody infusion abolished resistance,thus demonstrating that CD8 T cells are the host effector population. Donor-committed and high proliferative potential progenitor numbers were markedly diminished by 48 hours after transplantation in both wild-type B6 and B6-cdd anti-donor MiHA-sensitized recipients. These observations indicate that the resistance pathway used in the cytotoxic deficient mice was both potent and rapidly induced - consistent with a CD8 memory T-cell response. To examine the role of Tumor necrosis factor-like weak inducer of apoptosis (TWEAK)- and TL1A-mediated cytotoxicity in this strong resistance,newly generated monoclonal antibodies specific for these ligands were administered to B6-cdd recipients sensitized to donor antigens. Recipients of syngeneic B6-gfp bone marrow exhibited significant donor colony-forming unit numbers after BMT. In contrast,low or absent colony-forming unit levels were detected in allogeneic recipients,including those that lacked perforin and FasL and that received anti-TWEAK,anti-tumor necrosis factor-related apoptosis-inducing ligand,and anti-TL1A monoclonal antibodies. These findings extend previous observations by demonstrating the existence of a rapidly effected resistance pathway mediated by memory CD8 effector T cells independent of the 2 major pathways of cytotoxicity. Together with previous findings,these results support the notion that effector cells derived from memory CD8 T-cell populations can mediate strong resistance against donor allogeneic MiHA-disparate hematopoietic engraftment by using a mechanism that is independent of the contribution of perforin,FasL,and the known death ligand receptor pathways. ?? 2005 American Society for Blood and Marrow Transplantation. View Publication

In the present investigation,we studied the modulating effects of several tea catechins and bioflavonoids on DNA methylation catalyzed by prokaryotic SssI DNA methyltransferase (DNMT) and human DNMT1. We found that each of the tea polyphenols [catechin,epicatechin,and (-)-epigallocatechin-3-O-gallate (EGCG)] and bioflavonoids (quercetin,fisetin,and myricetin) inhibited SssI DNMT- and DNMT1-mediated DNA methylation in a concentration-dependent manner. The IC(50) values for catechin,epicatechin,and various flavonoids ranged from 1.0 to 8.4 microM,but EGCG was a more potent inhibitor,with IC(50) values ranging from 0.21 to 0.47 microM. When epicatechin was used as a model inhibitor,kinetic analyses showed that this catechol-containing dietary polyphenol inhibited enzymatic DNA methylation in vitro largely by increasing the formation of S-adenosyl-L-homocysteine (a potent noncompetitive inhibitor of DNMTs) during the catechol-O-methyltransferase-mediated O-methylation of this dietary catechol. In comparison,the strong inhibitory effect of EGCG on DNMT-mediated DNA methylation was independent of its own methylation and was largely due to its direct inhibition of the DNMTs. This inhibition is strongly enhanced by Mg(2+). Computational modeling studies showed that the gallic acid moiety of EGCG plays a crucial role in its high-affinity,direct inhibitory interaction with the catalytic site of the human DNMT1,and its binding with the enzyme is stabilized by Mg(2+). The modeling data on the precise molecular mode of EGCG's inhibitory interaction with human DNMT1 agrees perfectly with our experimental finding. View Publication

TLRs are involved in innate cell activation by conserved structures expressed by microorganisms. Human T cells express the mRNA encoding most of TLRs. Therefore,we tested whether some TLR ligands may modulate the function of highly purified human CD4+ T lymphocytes. We report that,in the absence of APCs,flagellin (a TLR5 ligand) and R-848 (a TLR7/8 ligand) synergized with suboptimal concentrations of TCR-dependent (anti-CD3 mAb) or -independent stimuli (anti-CD2 mAbs or IL-2) to up-regulate proliferation and IFN-gamma,IL-8,and IL-10 but not IL-4 production by human CD4+ T cells. No effect of poly(I:C) and LPS,ligands for TLR3 and TLR4,respectively,was detected. We also observed that CD4+CD45RO+ memory T cell responses to TLR ligands were more potent than those observed with CD4+CD45RA+ naive T cells. Moreover,among the memory T cells,CCR7- effector cells were more sensitive to TLR ligands than CCR7+ central memory cells. These data demonstrate for the first time a direct effect of TLR5 and TLR7/8 ligands on human T cells,and highlight an innate arm in T cell functions. They also suggest that some components from invading microorganisms may directly stimulate effector memory T cells located in tissues by up-regulating cytokine and chemokine production. View Publication