技术资料

Differentiation of human embryonic stem cells (hESCs) provides a unique opportunity to study the regulatory mechanisms that facilitate cellular transitions in a human context. To that end,we performed comprehensive transcriptional and epigenetic profiling of populations derived through directed differentiation of hESCs representing each of the three embryonic germ layers. Integration of whole-genome bisulfite sequencing,chromatin immunoprecipitation sequencing,and RNA sequencing reveals unique events associated with specification toward each lineage. Lineage-specific dynamic alterations in DNA methylation and H3K4me1 are evident at putative distal regulatory elements that are frequently bound by pluripotency factors in the undifferentiated hESCs. In addition,we identified germ-layer-specific H3K27me3 enrichment at sites exhibiting high DNA methylation in the undifferentiated state. A better understanding of these initial specification events will facilitate identification of deficiencies in current approaches,leading to more faithful differentiation strategies as well as providing insights into the rewiring of human regulatory programs during cellular transitions. ?? 2013 Elsevier Inc. View Publication

Neural stem cells (NSCs) possess immunosuppressive characteristics,but effects of NSCs on human dendritic cells (DCs),the most important antigen presenting cells,are less well studied. We used an in vitro approach to evaluate the effects of human NSCs on differentiation of human blood CD14+ monocytes into DCs. NSCs derived from H1 human embryonic stem cells (hESC-NSCs) and human ReNcell NSC line,as well as human bone marrow derived mesenchymal stem cells (MSCs),were tested. We observed that in response to treatment with interleukin-4 and granulocyte macrophage colony-stimulating factor CD14+ monocytes co-cultured with NSCs were able to down-regulate CD14 and up-regulate the differentiation marker CD1a,whereas MSC co-culture strongly inhibited CD1a expression and supported prolonged expression of CD14. A similar difference between NSCs and MSCs was noted when lipopolysaccharides were included to induce maturation of monocyte-derived DCs. However,when effects on the function of derived DCs were investigated,NSCs suppressed the elevation of the DC maturation marker CD83,although not the up-regulation of costimulatory molecules CD80,CD86 and CD40,and impaired the functional capacity of the derived DCs to stimulate alloreactive T cells. We did not observe any obvious difference between hESC-NSCs and ReNcell NSCs in inhibiting DC maturation and function. Our data suggest that although human NSCs are less effective than human MSCs in suppressing monocyte differentiation into DCs,these stem cells can still affect the function of DCs,ultimately regulating specific immune responses. View Publication

Everolimus is a potent,oral inhibitor of the mammalian target of rapamycin (mTOR) that has been investigated in multiple clinical development programs since 1996. A unique collaboration between academic and pharmaceutical experts fostered research that progressed rapidly,with simultaneous indication findings across numerous tumor types. Initially developed for the prophylaxis of organ transplant rejection,everolimus has demonstrated efficacy and safety for the treatment of patients with various types of cancer (renal cell carcinoma,neuroendocrine tumors of pancreatic origin,and breast cancer) and for adult and pediatric patients with tuberous sclerosis complex. The FDA approval of everolimus for these diseases has addressed several unmet medical needs and is widely accepted by the medical community where treatment options may be limited. An extensive clinical development program is ongoing to establish the role of everolimus as monotherapy,or in combination with other agents,in the treatment of a broad spectrum of malignancies. View Publication

Lung cancer is the leading cause of cancer-related mortality worldwide. Recent evidence indicates that tumors contain a subpopulation of cancer stem cells (CSCs) that are responsible for tumor maintenance and spread. CSCs have recently been linked to the occurrence of epithelial-to-mesenchymal transition (EMT). Neurotrophins (NTs) are growth factors that regulate the biology of embryonic stem cells and cancer cells,but still little is known about the role NTs in the progression of lung cancer. In this work,we investigated the role of the NTs and their receptors using as a study system primary cell cultures derived from malignant pleural effusions (MPEs) of patients with adenocarcinoma of the lung. We assessed the expression of NTs and their receptors in MPE-derived adherent cultures vs. spheroids enriched in CSC markers. We observed in spheroids a selectively enhanced expression of TrkB,both at the mRNA and protein levels. Both K252a,a known inhibitor of Trk activity,and a siRNA against TrkB strongly affected spheroid morphology,induced anoikis and decreased spheroid forming efficiency. Treatment with neurotrophins reversed the inhibitory effect of K252a. Importantly,TrkB inhibition caused loss of vimentin expression as well as that of a set of transcription factors known to be linked to EMT. These ex vivo results nicely correlated with an inverse relationship between TrkB and E-cadherin expression measured by immunohistochemistry in a panel of lung adenocarcinoma samples. We conclude that TrkB is involved in full acquisition of EMT in lung cancer,and that its inhibition results in a less aggressive phenotype. View Publication

Aging is known to be the single most important risk factor for multiple diseases. Sirtuin 6,or SIRT6,has recently been identified as a critical regulator of transcription,genome stability,telomere integrity,DNA repair,and metabolic homeostasis. A knockout mouse model of SIRT6 has displayed dramatic phenotypes of accelerated aging. In keeping with its role in aging,we demonstrated that human dermal fibroblasts (HDFs) from older human subjects were more resistant to reprogramming by classic Yamanaka factors than those from younger human subjects,but the addition of SIRT6 during reprogramming improved such efficiency in older HDFs substantially. Despite the importance of SIRT6,little is known about the molecular mechanism of its regulation. We show,for the first,time posttranscriptional regulation of SIRT6 by miR-766 and inverse correlation in the expression of this microRNA in HDFs from different age groups. Our results suggest that SIRT6 regulates miR-766 transcription via a feedback regulatory loop,which has implications for the modulation of SIRT6 expression in reprogramming of aging cells. View Publication

Tumor heterogeneity of high-grade glioma (HGG) is recognized by four clinically relevant subtypes based on core gene signatures. However,molecular signaling in glioma stem cells (GSCs) in individual HGG subtypes is poorly characterized. Here we identified and characterized two mutually exclusive GSC subtypes with distinct dysregulated signaling pathways. Analysis of mRNA profiles distinguished proneural (PN) from mesenchymal (Mes) GSCs and revealed a pronounced correlation with the corresponding PN or Mes HGGs. Mes GSCs displayed more aggressive phenotypes in vitro and as intracranial xenografts in mice. Further,Mes GSCs were markedly resistant to radiation compared with PN GSCs. The glycolytic pathway,comprising aldehyde dehydrogenase (ALDH) family genes and in particular ALDH1A3,were enriched in Mes GSCs. Glycolytic activity and ALDH activity were significantly elevated in Mes GSCs but not in PN GSCs. Expression of ALDH1A3 was also increased in clinical HGG compared with low-grade glioma or normal brain tissue. Moreover,inhibition of ALDH1A3 attenuated the growth of Mes but not PN GSCs. Last,radiation treatment of PN GSCs up-regulated Mes-associated markers and down-regulated PN-associated markers,whereas inhibition of ALDH1A3 attenuated an irradiation-induced gain of Mes identity in PN GSCs. Taken together,our data suggest that two subtypes of GSCs,harboring distinct metabolic signaling pathways,represent intertumoral glioma heterogeneity and highlight previously unidentified roles of ALDH1A3-associated signaling that promotes aberrant proliferation of Mes HGGs and GSCs. Inhibition of ALDH1A3-mediated pathways therefore might provide a promising therapeutic approach for a subset of HGGs with the Mes signature. View Publication

Human embryonic stem cells and mouse epiblast stem cells represent a primed pluripotent stem cell state that requires TGF-β/activin signaling. TGF-β and/or activin are commonly thought to regulate transcription through both Smad2 and Smad3. However,the different contributions of these two Smads to primed pluripotency and the downstream events that they may regulate remain poorly understood. We addressed the individual roles of Smad2 and Smad3 in the maintenance of primed pluripotency. We found that Smad2,but not Smad3,is required to maintain the undifferentiated pluripotent state. We defined a Smad2 regulatory circuit in human embryonic stem cells and mouse epiblast stem cells,in which Smad2 acts through binding to regulatory promoter sequences to activate Nanog expression while in parallel repressing autocrine bone morphogenetic protein signaling. Increased autocrine bone morphogenetic protein signaling caused by Smad2 down-regulation leads to cell differentiation toward the trophectoderm,mesoderm,and germ cell lineages. Additionally,induction of Cdx2 expression,as a result of decreased Smad2 expression,leads to repression of Oct4 expression,which,together with the decreased Nanog expression,accelerates the loss of pluripotency. These findings reveal that Smad2 is a unique integrator of transcription and signaling events and is essential for the maintenance of the mouse and human primed pluripotent stem cell state. View Publication

Oligodendrocytes-the myelin-forming cells of the central nervous system-can be regenerated during adulthood. In adults,new oligodendrocytes originate from oligodendrocyte progenitor cells (OPCs),but also from neural stem cells (NSCs). Although several factors supporting oligodendrocyte production have been characterized,the mechanisms underlying the generation of adult oligodendrocytes are largely unknown. Here we show that genetic inactivation of SIRT1,a protein deacetylase implicated in energy metabolism,increases the production of new OPCs in the adult mouse brain,in part by acting in NSCs. New OPCs produced following SIRT1 inactivation differentiate normally,generating fully myelinating oligodendrocytes. Remarkably,SIRT1 inactivation ameliorates remyelination and delays paralysis in mouse models of demyelinating injuries. SIRT1 inactivation leads to the upregulation of genes involved in cell metabolism and growth factor signalling,in particular PDGF receptor α (PDGFRα). Oligodendrocyte expansion following SIRT1 inactivation is mediated at least in part by AKT and p38 MAPK-signalling molecules downstream of PDGFRα. The identification of drug-targetable enzymes that regulate oligodendrocyte regeneration in adults could facilitate the development of therapies for demyelinating injuries and diseases,such as multiple sclerosis. View Publication

Label-retaining cancer cells (LRCCs) represent a novel population of stem-like cancer cells exhibiting slow cycling,chemoresistance and tumor-initiating capacities; however,their properties remain unclear,and approaches to eradicate LRCCs remain elusive. Here,we report that colon cancer cells with high fluorescent intensity,referred to as LRCCs,have the greatest cancer stem cell (CSC)-like capacities and that they preferentially express CSC markers and stemness-related genes. Moreover,we found that Lgr5,which has been reported to be a marker of rapid cycling CSCs,is almost negatively expressed in LRCCs but that its expression is gradually increased in the differentiation process of LRCCs. Interestingly,we found that LRCCs are especially sensitive to the pro-apoptotic effect of IFN-γ treatment both in vitro and in vivo because LRCCs possess higher IFN-γR levels compared with non-LRCCs,which results in the upregulation of the apoptosis pathway after IFN-γ treatment. Furthermore,we found that IFN-γ shows synergistic effects with the conventional anticancer drug Oxaliplatin to eliminate both LRCCs and non-LRCCs. In conclusion,this is the first study to suggest that LRCCs,as a distinct tumor-initiating population,can be selectively eradicated by IFN-γ,which may provide a novel therapeutic strategy for colon cancer treatment. View Publication

Human pluripotent stem cells are a powerful tool for modeling brain development and disease. The human cortex is composed of two major neuronal populations: projection neurons and local interneurons. Cortical interneurons comprise a diverse class of cell types expressing the neurotransmitter GABA. Dysfunction of cortical interneurons has been implicated in neuropsychiatric diseases,including schizophrenia,autism,and epilepsy. Here,we demonstrate the highly efficient derivation of human cortical interneurons in an NKX2.1::GFP human embryonic stem cell reporter line. Manipulating the timing of SHH activation yields three distinct GFP+ populations with specific transcriptional profiles,neurotransmitter phenotypes,and migratory behaviors. Further differentiation in a murine cortical environment yields parvalbumin- and somatostatin-expressing neurons that exhibit synaptic inputs and electrophysiological properties of cortical interneurons. Our study defines the signals sufficient for modeling human ventral forebrain development in vitro and lays the foundation for studying cortical interneuron involvement in human disease pathology. View Publication

Reprogramming of somatic cells into patient-specific pluripotent analogues of human embryonic stem cells (ESCs) emerges as a prospective therapeutic angle in molecular medicine and a tool for basic stem cell biology. However,the combination of relative inefficiency and high variability of non-defined culture conditions precluded the use of this technique in a clinical setting and impeded comparability between laboratories. To overcome these obstacles,we sequentially devised a reprogramming protocol using one lentiviral-based polycistronic reprogramming construct,optimized for high co-expression of OCT4,SOX2,KLF4 and MYC in conjunction with small molecule inhibitors of non-permissive signaling cascades,such as transforming growth factor $\$(SB431542),MEK/ERK (PD0325901) and Rho-kinase signaling (Thiazovivin),in a defined extracellular environment. Based on human fetal liver fibroblasts we could efficiently derive induced pluripotent stem cells (iPSCs) within 14 days. We attained efficiencies of up to 10.97±1.71% resulting in 79.5- fold increase compared to non-defined reprogramming using four singular vectors. We show that the overall increase of efficiency and temporal kinetics is a combinatorial effect of improved lentiviral vector design,signaling inhibition and definition of extracellular matrix (Matrigel®) and culture medium (mTESR®1). Using this protocol,we could derive iPSCs from patient fibroblasts,which were impermissive to classical reprogramming efforts,and from a patient suffering from familial platelet disorder. Thus,our defined protocol for highly efficient reprogramming to generate patient-specific iPSCs,reflects a big step towards therapeutic and broad scientific application of iPSCs,even in previously unfeasible settings. View Publication

Recent clinical studies suggest that adoptive transfer of donor-derived natural killer (NK) cells may improve clinical outcome in hematological malignancies and some solid tumors by direct anti-tumor effects as well as by reduction of graft versus host disease (GVHD). NK cells have also been shown to enhance transplant engraftment during allogeneic hematopoietic stem cell transplantation (HSCT) for hematological malignancies. The limited ex vivo expansion potential of NK cells from peripheral blood (PB) or umbilical cord blood (UCB) has however restricted their therapeutic potential. Here we define methods to efficiently generate NK cells from donor-matched,full-term human placenta perfusate (termed Human Placenta-Derived Stem Cell,HPDSC) and UCB. Following isolation from cryopreserved donor-matched HPDSC and UCB units,CD56+CD3- placenta-derived NK cells,termed pNK cells,were expanded in culture for up to 3 weeks to yield an average of 1.2 billion cells per donor that were textgreater80% CD56+CD3-,comparable to doses previously utilized in clinical applications. Ex vivo-expanded pNK cells exhibited a marked increase in anti-tumor cytolytic activity coinciding with the significantly increased expression of NKG2D,NKp46,and NKp44 (p textless 0.001,p textless 0.001,and p textless 0.05,respectively). Strong cytolytic activity was observed against a wide range of tumor cell lines in vitro. pNK cells display a distinct microRNA (miRNA) expression profile,immunophenotype,and greater anti-tumor capacity in vitro compared to PB NK cells used in recent clinical trials. With further development,pNK may represent a novel and effective cellular immunotherapy for patients with high clinical needs and few other therapeutic options. View Publication