技术资料

Hematopoiesis is dependent upon the bone marrow microenvironment,which is comprised of multiple mesenchymal cell types,including fibroblasts,endothelial cells,osteoblasts,and stroma progenitors. The canonical Wnt signaling pathway,which relies on the beta-catenin protein to mediate its signal,is necessary for the normal development of mesenchymal tissue. We hypothesized that canonical Wnt signaling regulates the cellular composition and function of the bone marrow microenvironment. We observed that a beta-catenin-deficient bone marrow microenvironment maintained hematopoietic stem cells but exhibited a decreased capacity to support primitive hematopoietic cells. These results correlated with decreased numbers of osteoblasts and with decreased production of basic fibroblast growth factor,stem cell factor,and vascular cell adhesion molecule-1. From these data,we propose a model in which beta-catenin in the microenvironment is required noncell autonomously for long-term maintenance of hematopoietic progenitors. View Publication

This study investigated the effect of mechanical load on human mesenchymal stem cell (hMSC) differentiation under different exogenous transforming growth factor-beta1 (TGF-beta(1)) concentrations (0,1 or 10 ng/ml).The role of the TGF-beta signalling pathway in this process was also studied. Human MSCs were seeded into fibrin-biodegradable polyurethane scaffolds at a cell density of 5 x 10(6) cells per scaffold and stimulated using our bioreactor. One hour of surface motion superimposed on cyclic compression was applied once a day over seven consecutive days. Scaffolds were analysed for gene expression,DNA content and glycosaminoglycan amount. Addition of TGF-beta(1) in the culture medium was sufficient to induce chondrogenesis of hMSCs. Depending on the TGF-beta(1) concentration of the culture medium,mechanical load stimulated chondrogenesis of hMSCs compared to the unloaded scaffolds,with a much stronger effect on gene expression at lower TGF-beta(1) concentrations. With TGF-beta(1) absent in the culture medium,mechanical load stimulated gene transcripts and protein synthesis of TGF-beta(1) and TGF-beta(3). TGF-beta type I receptor inhibitor LY364947 blocked the up-regulation on TGF-beta(1) and TGF-beta(3) production stimulated by mechanical load,and also blocked the chondrogenesis of hMSCs. Taken together,these findings suggest that mechanical load promotes chondrogenesis of hMSCs through TGF-beta pathway by up-regulating TGF-beta gene expression and protein synthesis. View Publication

BACKGROUND Interleukin (IL-6) and transforming growth factor (TGF)-beta have been shown to play a role in skin development and maintenance. OBJECTIVES A link between these two cytokines has yet to be identified and therefore in this study we investigated the modulation of TGF-beta1 and TGF-beta type 2 receptor (TGF-betaR2) by IL-6 in skin. METHODS An IL-6 knockout (IL-6KO) fibroblast-populated lattice model and intradermal injections of IL-6 into unwounded IL-6KO mice were used to investigate the direct effects of IL-6 treatment on TGF-beta and TGF-betaR2 expression and to determine the signalling mechanism. In addition,IL-6KO and C57BL/6 control mice were wounded by a 4-mm punch biopsy to monitor expression of TGF-beta1 and TGF-betaR2 within a wound over time. The expression of TGF-beta1 and TGF-betaR2 was assessed by real-time quantitative polymerase chain reaction,enzyme-linked immunosorbent assay and immunohistology. RESULTS Recombinant IL-6 treatment of IL-6KO lattices and intradermal injections of IL-6 showed a significant induction of TGF-beta1 mRNA and protein,with TGF-beta1 expression localized in the dermis,while TGF-betaR2 expression was primarily in the epidermis in IL-6KO mice. During healing,the expression of TGF-beta1 and TGF-betaR2 mRNA was significantly greater in unwounded and 7-day-old wounds from wild-type mice; however,protein expression did not differ. Treatment with signal transduction inhibitors indicated that IL-6 modulates TGF-beta through a mitogen-activated protein kinase/extracellular signal-regulated kinase (Mapk/Erk)-dependent mechanism. CONCLUSION These studies indicate that IL-6 has the ability to modulate the expression of TGF-beta and TGF-betaR2 to varying degrees in the skin,which may provide a possible mechanism for defining the role of IL-6 in skin maintenance and a new association of IL-6 with TGF-beta in pathologies associated with fibrosis. View Publication

Dental pulp is a promising source of mesenchymal stem cells with the potential for cell-mediated therapies and tissue engineering applications. We recently reported that isolation of dental pulp-derived stem cells (DPSC) is feasible for at least 120h after tooth extraction,and that cryopreservation of early passage cultured DPSC leads to high-efficiency recovery post-thaw. This study investigated additional processing and cryobiological characteristics of DPSC,ending with development of procedures for banking. First,we aimed to optimize cryopreservation of established DPSC cultures,with regards to optimizing the cryoprotective agent (CPA),the CPA concentration,the concentration of cells frozen,and storage temperatures. Secondly,we focused on determining cryopreservation characteristics of enzymatically digested tissue as a cell suspension. Lastly,we evaluated the growth,surface markers and differentiation properties of DPSC obtained from intact teeth and undigested,whole dental tissue frozen and thawed using the optimized procedures. In these experiments it was determined that Me(2)SO at a concentration between 1 and 1.5M was the ideal cryopreservative of the three studied. It was also determined that DPSC viability after cryopreservation is not limited by the concentration of cells frozen,at least up to 2x10(6) cells/mL. It was further established that DPSC can be stored at -85 degrees C or -196 degrees C for at least six months without loss of functionality. The optimal results with the least manipulation were achieved by isolating and cryopreserving the tooth pulp tissues,with digestion and culture performed post-thaw. A recovery of cells from textgreater85% of the tissues frozen was achieved and cells isolated post-thaw from tissue processed and frozen with a serum free,defined cryopreservation medium maintained morphological and developmental competence and demonstrated MSC-hallmark trilineage differentiation under the appropriate culture conditions. View Publication

Persistent viral infections are a major health concern worldwide. During persistent infection,overwhelming viral replication and the rapid loss of antiviral T-cell function can prevent immune-mediated clearance of the infection,and therapies to reanimate the immune response and purge persistent viruses have been largely unsuccessful. Adoptive immunotherapy using memory T cells is a highly successful therapeutic approach to eradicate a persistent viral infection. Understanding precisely how therapeutically administered memory T cells achieve clearance should improve our ability to terminate states of viral persistence in humans. Mice persistently infected from birth with lymphocytic choriomeningitis virus are tolerant to the pathogen at the T-cell level and thus provide an excellent model to evaluate immunotherapeutic regimens. Previously,we demonstrated that adoptively transferred memory T cells require recipient dendritic cells to effectively purge an established persistent viral infection. However,the mechanisms that reactivate and sustain memory T-cell responses during clearance of such an infection remain unclear. Here we establish that therapeutic memory T cells require CD80 and CD86 costimulatory signals to efficiently clear an established persistent viral infection in vivo. Early blockade of costimulatory pathways with CTLA-4-Fc decreased the secondary expansion of virus-specific CD8(+) and CD4(+) memory T cells as well as their ability to produce antiviral cytokines and purge the persistent infection. Late costimulation blockade also reduced virus-specific T-cell numbers,illustrating that sustained interactions with costimulatory molecules is required for efficient T-cell expansion. These findings indicate that antiviral memory T cells require costimulation to efficiently clear a persistent viral infection and that costimulatory pathways can be targeted to modulate the magnitude of an adoptive immunotherapeutic regimen. View Publication

As a member of the class III histone deacetylases,Sirtuin-2 (SIRT2) is critical in cell cycle regulation which makes it a potential target for cancer therapeutics. In this study,we identified a novel SIRT2 inhibitor,AC-93253,with IC(50) of 6 microM in vitro. The compound is selective,inhibiting SIRT2 7.5- and 4-fold more potently than the closely related SIRT1 and SIRT3,respectively. AC-93253 significantly enhanced acetylation of tubulin,p53,and histone H4,confirming SIRT2 and SIRT1 as its cellular targets. AC-93253 as a single agent exhibited submicromolar selective cytotoxicity towards all four tumor cell lines tested with a therapeutic window up to 200-fold,comparing to any of the three normal cell types tested. Results from high content analysis suggested that AC-93253 significantly triggered apoptosis. Taken together,SIRT2 selective inhibitor AC-93253 may serve as a novel chemical scaffold for structure-activity relationship study and future lead development. View Publication

Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase that is overexpressed in many types of tumors,including pancreatic cancer,and plays an important role in cell adhesion and survival signaling. Pancreatic cancer is a lethal disease and is very resistant to chemotherapy,and FAK has been shown recently to assist in tumor cell survival. Therefore,FAK is an excellent potential target for anti-cancer therapy. We identified a novel small molecule inhibitor (1,2,4,5-Benzenetetraamine tetrahydrochloride,that we called Y15) targeting the main autophosphorylation site of FAK and hypothesized that it would be an effective treatment strategy against human pancreatic cancer. Y15 specifically blocked phosphorylation of Y397-FAK and total phosphorylation of FAK. It directly inhibited FAK autophosphorylation in a dose- and time-dependent manner. Furthermore,Y15 increased pancreatic cancer cell detachment and inhibited cell adhesion in a dose-dependent manner. Y15 effectively caused human pancreatic tumor regression in vivo,when administered alone and its effects were synergistic with gemcitabine chemotherapy. This was accompanied by a decrease in Y397-phosphorylation of FAK in the tumors treated with Y15. Thus,targeting the Y397 site of FAK in pancreatic cancer with the small molecule inhibitor,1,2,4,5-Benzenetetraamine tetrahydrochloride,is a potentially effective treatment strategy in this deadly disease. View Publication

The phosphatidylinositide 3-kinase pathway is frequently deregulated in human cancers and inhibitors offer considerable therapeutic potential. We previously described the promising tricyclic pyridofuropyrimidine lead and chemical tool compound PI-103. We now report the properties of the pharmaceutically optimized bicyclic thienopyrimidine derivatives PI-540 and PI-620 and the resulting clinical development candidate GDC-0941. All four compounds inhibited phosphatidylinositide 3-kinase p110alpha with IC(50) textless or = 10 nmol/L. Despite some differences in isoform selectivity,these agents exhibited similar in vitro antiproliferative properties to PI-103 in a panel of human cancer cell lines,with submicromolar potency in PTEN-negative U87MG human glioblastoma cells and comparable phosphatidylinositide 3-kinase pathway modulation. PI-540 and PI-620 exhibited improvements in solubility and metabolism with high tissue distribution in mice. Both compounds gave improved antitumor efficacy over PI-103,following i.p. dosing in U87MG glioblastoma tumor xenografts in athymic mice,with treated/control values of 34% (66% inhibition) and 27% (73% inhibition) for PI-540 (50 mg/kg b.i.d.) and PI-620 (25 mg/kg b.i.d.),respectively. GDC-0941 showed comparable in vitro antitumor activity to PI-103,PI-540,and PI-620 and exhibited 78% oral bioavailability in mice,with tumor exposure above 50% antiproliferative concentrations for textgreater8 hours following 150 mg/kg p.o. and sustained phosphatidylinositide 3-kinase pathway inhibition. These properties led to excellent dose-dependent oral antitumor activity,with daily p.o. dosing at 150 mg/kg achieving 98% and 80% growth inhibition of U87MG glioblastoma and IGROV-1 ovarian cancer xenografts,respectively. Together,these data support the development of GDC-0941 as a potent,orally bioavailable inhibitor of phosphatidylinositide 3-kinase. GDC-0941 has recently entered phase I clinical trials. View Publication

Platelet factor 4 (PF4) is a negative regulator of megakaryopoiesis,but its mechanism of action had not been addressed. Low-density lipoprotein (LDL) receptor-related protein-1 (LRP1) has been shown to mediate endothelial cell responses to PF4 and so we tested this receptor's importance in PF4's role in megakaryopoiesis. We found that LRP1 is absent from megakaryocyte-erythrocyte progenitor cells,is maximally present on large,polyploidy megakaryocytes,and near absent on platelets. Blocking LRP1 with either receptor-associated protein (RAP),an antagonist of LDL family member receptors,or specific anti-LRP1 antibodies reversed the inhibition of megakaryocyte colony growth by PF4. In addition,using shRNA to reduce LRP1 expression was able to restore megakaryocyte colony formation in bone marrow isolated from human PF4-overexpressing mice (hPF4(High)). Further,shRNA knockdown of LRP1 expression was able to limit the effects of PF4 on megakaryopoiesis. Finally,infusion of RAP into hPF4(High) mice was able to increase baseline platelet counts without affecting other lineages,suggesting that this mechanism is important in vivo. These studies extend our understanding of PF4's negative paracrine effect in megakaryopoiesis and its potential clinical implications as well as provide insights into the biology of LRP1,which is transiently expressed during megakaryopoiesis. View Publication

Recent studies involving bone marrow mesenchymal stromal cells (MSCs) demonstrated that interferon (IFN)-gamma stimulation induces major histocompatibility complex (MHC) class II-mediated antigen presentation in MSCs both in vitro and in vivo. Concordantly,we investigated the ability of MSCs to present extracellular antigen through their MHC class I molecules,a process known as cross-presentation. Using an in vitro antigen presentation assay,we demonstrated that murine MSCs can cross-present soluble ovalbumin (OVA) to naive CD8(+) T cells from OT-I mice. Cross-presentation by MSC was proteasome dependent and partly dependent on transporter associated with antigen-processing molecules. Pretreatment of MSC with IFN-gamma increased cross-presentation by up-regulating antigen processing and presentation. However,although the transcription of the transporter associated with antigen processing-1 molecules and the immunoproteasome subunit LMP2 induced by IFN-gamma was inhibited by transforming growth factor-beta,the overall cross-presentation capacity of MSCs remained unchanged after transforming growth factor-beta treatment. These observations were validated in vivo by performing an immune reconstitution assay in beta(2)-microglobulin(-/-) mice and show that OVA cross-presentation by MSCs induces the proliferation of naive OVA-specific CD8(+) T cells. In conclusion,we demonstrate that MSCs can cross-present exogenous antigen and induce an effective CD8(+) T-cell immune response,a property that could be exploited as a therapeutic cell-based immune biopharmaceutic for the treatment of cancer or infectious diseases. View Publication

Human breast tumors contain a breast cancer stem cell (BCSC) population with properties reminiscent of normal stem cells. We found 37 microRNAs that were differentially expressed between human BCSCs and nontumorigenic cancer cells. Three clusters,miR-200c-141,miR-200b-200a-429,and miR-183-96-182 were downregulated in human BCSCs,normal human and murine mammary stem/progenitor cells,and embryonal carcinoma cells. Expression of BMI1,a known regulator of stem cell self-renewal,was modulated by miR-200c. miR-200c inhibited the clonal expansion of breast cancer cells and suppressed the growth of embryonal carcinoma cells in vitro. Most importantly,miR-200c strongly suppressed the ability of normal mammary stem cells to form mammary ducts and tumor formation driven by human BCSCs in vivo. The coordinated downregulation of three microRNA clusters and the similar functional regulation of clonal expansion by miR-200c provide a molecular link that connects BCSCs with normal stem cells. View Publication

Inappropriate activation of the Hedgehog (Hh) signaling pathway has been implicated in a diverse spectrum of cancers,and its pharmacological blockade has emerged as an anti-tumor strategy. While nearly all known Hh pathway antagonists target the transmembrane protein Smoothened (Smo),small molecules that suppress downstream effectors could more comprehensively remediate Hh pathway-dependent tumors. We report here four Hh pathway antagonists that are epistatic to the nucleocytoplasmic regulator Suppressor of Fused [Su(fu)],including two that can inhibit Hh target gene expression induced by overexpression of the Gli transcription factors. Each inhibitor has a unique mechanism of action,and their phenotypes reveal that Gli processing,Gli activation,and primary cilia formation are pharmacologically targetable. We further establish the ability of certain compounds to block the proliferation of cerebellar granule neuron precursors expressing an oncogenic form of Smo,and we demonstrate that Hh pathway inhibitors can have tissue-specific activities. These antagonists therefore constitute a valuable set of chemical tools for interrogating downstream Hh signaling mechanisms and for developing chemotherapies against Hh pathway-related cancers. View Publication