技术资料

BACKGROUND Many cancers,including melanoma,exclusively express constitutive proteasomes (cPs) and are unable to express immunoproteasomes (iPs). In contrast,mature DCs used for immunotherapy exclusively express iPs. Since proteasomes generate peptides presented by HLA class I molecules,we hypothesized that mature melanoma antigen-loaded DCs engineered to process antigens through cPs would be superior inducers of antimelanoma immunity in vivo. METHODS Subjects with metastatic melanoma were vaccinated with mature DCs transfected with RNAs encoding melanoma antigens MART1,MAGE-3,gp100,and tyrosinase. These DCs were derived from monocytes that were untransfected (Arm A; n = 4),transfected with control siRNA (Arm B; n = 3),or transfected with siRNAs targeting the 3 inducible iP subunits (Arm C; n = 5). RESULTS Vaccination stimulated antigen-specific T cell responses in all subjects,which peaked after 3-4 vaccinations,but remained elevated in Arm C subjects. Also in Arm C,circulating melanoma cell levels (as detected by quantitative PCR) fell,and T cell lytic activity against autologous melanoma was induced. In HLA-A2 subjects,CD8 T cells that bound tetramers loaded with cP-derived melanoma antigenic peptides were found in the peripheral blood only in Arm C subjects. Of 2 subjects with active disease (both in Arm C),one had a partial clinical response,while the other,who exhibited diffuse dermal and soft tissue metastases,had a complete response. CONCLUSION These results suggest that the efficacy of melanoma DC-based immunotherapy is enhanced when tumor antigen-loaded DCs used for vaccination express cPs. TRIAL REGISTRATION Clinicaltrials.gov NCT00672542. FUNDING Duke Clinical Research Institute/Duke Translational Medicine Institute,Duke Melanoma Consortium,and Duke University Department of Surgery. View Publication

Transposon gene delivery systems offer an alternative,non-viral-based approach to generate induced pluripotent stem cells (iPSCs). Here we used the Sleeping Beauty (SB) transposon to generate four human iPSC lines from foetal fibroblasts. In contrast to other gene delivery systems,the SB transposon does not exhibit an integration bias towards particular genetic elements,thereby reducing the risk of insertional mutagenesis. Furthermore,unlike the alternative transposon piggyBac,SB has no SB-like elements within the human genome,minimising the possibility of mobilising endogenous transposon elements. All iPSC lines exhibited the expected characteristics of pluripotent human cells,including the ability to differentiate to derivatives of all three germ layers in vitro. Re-expression of the SB transposase in the iPSCs after reprogramming resulted in the mobilisation of some of the transposons. These results indicate that the SB transposon system is a useful addition to methods for generating human iPSCs,both for basic and applied biomedical research,and in the context of future therapeutic application. textcopyright 2013 International Society of Differentiation. View Publication

Long noncoding RNAs (lncRNAs) are abundant in the mammalian transcriptome,and many are specifically expressed in the brain. We have identified a group of lncRNAs,including rhabdomyosarcoma 2-associated transcript (RMST),which are indispensable for neurogenesis. Here,we provide mechanistic insight into the role of human RMST in modulating neurogenesis. RMST expression is specific to the brain,regulated by the transcriptional repressor REST,and increases during neuronal differentiation,indicating a role in neurogenesis. RMST physically interacts with SOX2,a transcription factor known to regulate neural fate. RMST and SOX2 coregulate a large pool of downstream genes implicated in neurogenesis. Through RNA interference and genome-wide SOX2 binding studies,we found that RMST is required for the binding of SOX2 to promoter regions of neurogenic transcription factors. These results establish the role of RMST as a transcriptional coregulator of SOX2 and a key player in the regulation of neural stem cell fate. ?? 2013 Elsevier Inc. View Publication

Sickle cell disease (SCD) is the most common human genetic disease which is caused by a single mutation of human β-globin (HBB) gene. The lack of long-term treatment makes the development of reliable cell and gene therapies highly desirable. Disease-specific patient-derived human induced pluripotent stem cells (hiPSCs) have great potential for developing novel cell and gene therapies. With the disease-causing mutations corrected in situ,patient-derived hiPSCs can restore normal cell functions and serve as a renewable autologous cell source for the treatment of genetic disorders. Here we successfully utilized transcription activator-like effector nucleases (TALENs),a recently emerged novel genome editing tool,to correct the SCD mutation in patient-derived hiPSCs. The TALENs we have engineered are highly specific and generate minimal off-target effects. In combination with piggyBac transposon,TALEN-mediated gene targeting leaves no residual ectopic sequences at the site of correction and the corrected hiPSCs retain full pluripotency and a normal karyotype. Our study demonstrates an important first step of using TALENs for the treatment of genetic diseases such as SCD,which represents a significant advance toward hiPSC-based cell and gene therapies. View Publication

INTRODUCTION: Ischemic stroke is a leading cause of death and disability,but treatment options are severely limited. Cell therapy offers an attractive strategy for regenerating lost tissues and enhancing the endogenous healing process. In this study,we investigated the use of human embryonic stem cell-derived neural precursors as a cell therapy in a murine stroke model.backslashnbackslashnMETHODS: Neural precursors were derived from human embryonic stem cells by using a fully adherent SMAD inhibition protocol employing small molecules. The efficiency of neural induction and the ability of these cells to further differentiate into neurons were assessed by using immunocytochemistry. Whole-cell patch-clamp recording was used to demonstrate the electrophysiological activity of human embryonic stem cell-derived neurons. Neural precursors were transplanted into the core and penumbra regions of a focal ischemic stroke in the barrel cortex of mice. Animals received injections of bromodeoxyuridine to track regeneration. Neural differentiation of the transplanted cells and regenerative markers were measured by using immunohistochemistry. The adhesive removal test was used to determine functional improvement after stroke and intervention.backslashnbackslashnRESULTS: After 11 days of neural induction by using the small-molecule protocol,over 95% of human embryonic stem-derived cells expressed at least one neural marker. Further in vitro differentiation yielded cells that stained for mature neuronal markers and exhibited high-amplitude,repetitive action potentials in response to depolarization. Neuronal differentiation also occurred after transplantation into the ischemic cortex. A greater level of bromodeoxyuridine co-localization with neurons was observed in the penumbra region of animals receiving cell transplantation. Transplantation also improved sensory recovery in transplant animals over that in control animals.backslashnbackslashnCONCLUSIONS: Human embryonic stem cell-derived neural precursors derived by using a highly efficient small-molecule SMAD inhibition protocol can differentiate into electrophysiologically functional neurons in vitro. These cells also differentiate into neurons in vivo,enhance regenerative activities,and improve sensory recovery after ischemic stroke. View Publication

The development of the mature epidermis requires a coordinated sequence of signaling events and transcriptional changes to specify surface ectodermal progenitor cells to the keratinocyte lineage. The initial events that specify epidermal keratinocytes from ectodermal progenitor cells are not well understood. Here,we use both developing mouse embryos and human embryonic stem cells (hESCs) to explore the mechanisms that direct keratinocyte fate from ectodermal progenitor cells. We show that both hESCs and murine embryos express p63 before keratin 14. Furthermore,we find that Notch signaling is activated before p63 expression in ectodermal progenitor cells. Inhibition of Notch signaling pharmacologically or genetically reveals a negative regulatory role for Notch signaling in p63 expression during ectodermal specification in hESCs or mouse embryos,respectively. Taken together,these data reveal a role for Notch signaling in the molecular control of ectodermal progenitor cell specification to the epidermal keratinocyte lineage. View Publication

The groundbreaking discovery of induced pluripotent stem cells (iPS cells) provides a new source for cell therapy. However,whether the iPS derived functional lineages from different cell origins have different immunogenicity remains unknown. It had been known that the cells isolated from extra-embryonic tissues,such as umbilical cord mesenchymal cells (UMCs),are less immunogenic than other adult lineages such as skin fibroblasts (SFs). In this report,we differentiated iPS cells from human UMCs and SFs into neural progenitor cells (NPCs) and analyzed their immunogenicity. Through co-culture with allologous peripheral blood mononuclear cells (PBMCs),we showed that UMCs were indeed less immunogenic than skin cells to simulate proliferation of PBMCs. Surprisingly,we found that the NPCs differentiated from UMC-iPS cells retained low immunogenicity as the parental UMCs based on the PBMC proliferation assay. In cytotoxic expression assay,reactions in most kinds of immune effector cells showed more perforin and granzyme B expression with SF-NPCs stimulation than that with UMC-NPCs stimulation in PBMC co-culture system,in T cell co-culture system as well. Furthermore,through whole genome expression microarray analysis,we showed that over 70 immune genes,including all members of HLA-I,were expressed at lower levels in NPCs derived from UMC-iPS cells than that from SF-iPS cells. Our results demonstrated a phenomenon that the low immunogenicity of the less immunogenic cells could be retained after cell reprogramming and further differentiation,thus provide a new concept to generate functional lineages with lower immunogenicity for regenerative medicine. View Publication

The future of safe cell-based therapy rests on overcoming teratoma/tumor formation,in particular when using human pluripotent stem cells (hPSCs),such as human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs). Because the presence of a few remaining undifferentiated hPSCs can cause undesirable teratomas after transplantation,complete removal of these cells with no/minimal damage to differentiated cells is a prerequisite for clinical application of hPSC-based therapy. Having identified a unique hESC signature of pro- and antiapoptotic gene expression profile,we hypothesized that targeting hPSC-specific antiapoptotic factor(s) (i.e.,survivin or Bcl10) represents an efficient strategy to selectively eliminate pluripotent cells with teratoma potential. Here we report the successful identification of small molecules that can effectively inhibit these antiapoptotic factors,leading to selective and efficient removal of pluripotent stem cells through apoptotic cell death. In particular,a single treatment of hESC-derived mixed population with chemical inhibitors of survivin (e.g.,quercetin or YM155) induced selective and complete cell death of undifferentiated hPSCs. In contrast,differentiated cell types (e.g.,dopamine neurons and smooth-muscle cells) derived from hPSCs survived well and maintained their functionality. We found that quercetin-induced selective cell death is caused by mitochondrial accumulation of p53 and is sufficient to prevent teratoma formation after transplantation of hESC- or hiPSC-derived cells. Taken together,these results provide the proof of concept" that small-molecule targeting of hPSC-specific antiapoptotic pathway(s) is a viable strategy to prevent tumor formation by selectively eliminating remaining undifferentiated pluripotent cells for safe hPSC-based therapy." View Publication

Anterior foregut endoderm (AFE) gives rise to therapeutically relevant cell types in tissues such as the esophagus,salivary glands,lung,thymus,parathyroid and thyroid. Despite its importance,reports describing the generation of AFE from pluripotent stem cells (PSCs) by directed differentiation have mainly focused on the Nkx2.1(+) lung and thyroid lineages. Here,we describe a novel protocol to derive a subdomain of AFE,identified by expression of Pax9,from PSCs using small molecules and defined media conditions. We generated a reporter PSC line for isolation and characterization of Pax9(+) AFE cells,which when transplanted in vivo,can form several distinct complex AFE-derived epithelia,including mucosal glands and stratified squamous epithelium. Finally,we show that the directed differentiation protocol can be used to generate AFE from human PSCs. Thus,this work both broadens the range of PSC-derived AFE tissues and creates a platform enabling the study of AFE disorders. View Publication

SOX2 (Sex-determining region Y (SRY)-Box2) has important functions during embryonic development and is involved in cancer stem cell (CSC) maintenance,in which it impairs cell growth and tumorigenicity. However,the function of SOX2 in pancreatic cancer cells is unclear. The objective of this study was to analyze SOX2 expression in human pancreatic tumors and determine the role of SOX2 in pancreatic cancer cells regulating CSC properties. In this report,we show that SOX2 is not expressed in normal pancreatic acinar or ductal cells. However,ectopic expression of SOX2 is observed in 19.3% of human pancreatic tumors. SOX2 knockdown in pancreatic cancer cells results in cell growth inhibition via cell cycle arrest associated with p21(Cip1) and p27(Kip1) induction,whereas SOX2 overexpression promotes S-phase entry and cell proliferation associated with cyclin D3 induction. SOX2 expression is associated with increased levels of the pancreatic CSC markers ALDH1,ESA and CD44. Importantly,we show that SOX2 is enriched in the ESA(+)/CD44(+) CSC population from two different patient samples. Moreover,we show that SOX2 directly binds to the Snail,Slug and Twist promoters,leading to a loss of E-Cadherin and ZO-1 expression. Taken together,our findings show that SOX2 is aberrantly expressed in pancreatic cancer and contributes to cell proliferation and stemness/dedifferentiation through the regulation of a set of genes controlling G1/S transition and epithelial-to-mesenchymal transition (EMT) phenotype,suggesting that targeting SOX2-positive cancer cells could be a promising therapeutic strategy. View Publication

Purine biosynthesis and metabolism,conserved in all living organisms,is essential for cellular energy homeostasis and nucleic acid synthesis. The de novo synthesis of purine precursors is under tight negative feedback regulation mediated by adenosine and guanine nucleotides. We describe a distinct early-onset neurodegenerative condition resulting from mutations in the adenosine monophosphate deaminase 2 gene (AMPD2). Patients have characteristic brain imaging features of pontocerebellar hypoplasia (PCH) due to loss of brainstem and cerebellar parenchyma. We found that AMPD2 plays an evolutionary conserved role in the maintenance of cellular guanine nucleotide pools by regulating the feedback inhibition of adenosine derivatives on de novo purine synthesis. AMPD2 deficiency results in defective GTP-dependent initiation of protein translation,which can be rescued by administration of purine precursors. These data suggest AMPD2-related PCH as a potentially treatable early-onset neurodegenerative disease. ?? 2013 Elsevier Inc. View Publication

Efficient strategies for precise genome editing in human-induced pluripotent cells (hiPSCs) will enable sophisticated genome engineering for research and clinical purposes. The development of programmable sequence-specific nucleases such as Transcription Activator-Like Effectors Nucleases (TALENs) and Cas9-gRNA allows genetic modifications to be made more efficiently at targeted sites of interest. However,many opportunities remain to optimize these tools and to enlarge their spheres of application. We present several improvements: First,we developed functional re-coded TALEs (reTALEs),which not only enable simple one-pot TALE synthesis but also allow TALE-based applications to be performed using lentiviral vectors. We then compared genome-editing efficiencies in hiPSCs mediated by 15 pairs of reTALENs and Cas9-gRNA targeting CCR5 and optimized ssODN design in conjunction with both methods for introducing specific mutations. We found Cas9-gRNA achieved 7-8× higher non-homologous end joining efficiencies (3%) than reTALENs (0.4%) and moderately superior homology-directed repair efficiencies (1.0 versus 0.6%) when combined with ssODN donors in hiPSCs. Using the optimal design,we demonstrated a streamlined process to generated seamlessly genome corrected hiPSCs within 3 weeks. View Publication