技术资料

We had earlier reported the derivation and characterization of two new sibling human embryonic stem cell lines BJNhem19 and BJNhem20,from discarded grade III embryos of Indian origin. We report here the characteristics of the two sibling cell lines after long-term continuous culture for over 2 yr during which they have been passaged over 200 times. We show that both cell lines adapt well to culture on various mouse and human feeders as well as in feeder-free conditions. The cells show normal diploid karyotype and continue to express all pluripotency markers. Both cell lines differentiate to derivatives of all three germ layers in vitro. However as reported earlier,BJNhem19 is unable to generate teratomas in nude or SCID mice or differentiate to beating cardiomyocytes when tested over several passages during long-term stable culture. On the other hand,the cardiac differentiation capacity of BJNhem20 is greatly increased,and it can generate beating cardiomyocytes that proliferate when isolated and cultured further. In conclusion,the two cell lines have maintained a stable phenotype for over 2 yr and are indeed immortal. Their derivation from grade III embryos does not seem to have any adverse effect on their long-term phenotype. The cells can be obtained for research purposes from the UK Stem Cell Bank and from the authors. View Publication

We report here that butyrate,a naturally occurring fatty acid commonly used as a nutritional supplement and differentiation agent,greatly enhances the efficiency of induced pluripotent stem (iPS) cell derivation from human adult or fetal fibroblasts. After transient butyrate treatment,the iPS cell derivation efficiency is enhanced by 15- to 51-fold using either retroviral or piggyBac transposon vectors expressing 4 to 5 reprogramming genes. Butyrate stimulation is more remarkable (textgreater100- to 200-fold) on reprogramming in the absence of either KLF4 or MYC transgene. Butyrate treatment did not negatively affect properties of iPS cell lines established by either 3 or 4 retroviral vectors or a single piggyBac DNA transposon vector. These characterized iPS cell lines,including those derived from an adult patient with sickle cell disease by either the piggyBac or retroviral vectors,show normal karyotypes and pluripotency. To gain insights into the underlying mechanisms of butyrate stimulation,we conducted genome-wide gene expression and promoter DNA methylation microarrays and other epigenetic analyses on established iPS cells and cells from intermediate stages of the reprogramming process. By days 6 to 12 during reprogramming,butyrate treatment enhanced histone H3 acetylation,promoter DNA demethylation,and the expression of endogenous pluripotency-associated genes,including DPPA2,whose overexpression partially substitutes for butyrate stimulation. Thus,butyrate as a cell permeable small molecule provides a simple tool to further investigate molecular mechanisms of cellular reprogramming. Moreover,butyrate stimulation provides an efficient method for reprogramming various human adult somatic cells,including cells from patients that are more refractory to reprogramming. View Publication

A subset of cells,tentatively called cancer stem cells (CSCs),in breast cancer have been associated with tumor initiation,drug resistance,and tumor persistence or aggressiveness. They are characterized by CD44 positivity,CD24 negativity,and/or ALDH1 positivity in flow cytometric studies. We hypothesized that the frequency or density of these cells may be associated with more aggressive tumor behavior. We borrowed these multiplexed,flow-based methods to develop an in situ method to define CSCs in formalin-fixed paraffin-embedded breast cancer tissue,with the goal of assessing the prognostic value of the presence of CSCs in breast cancer. Using a retrospective collection of 321 node-negative and 318 node-positive patients with a mean follow-up time of 12.6 years,we assessed TMAs using the AQUA method for quantitative immunofluorescence. Using a multiplexed assay for ALDH1,CD44,and cytokeratin to measure the coexpression of these proteins,putative CSCs appear in variable sized clusters and in 27 cases (of 490),which showed significantly worse outcome (log rank P = 0.0003). Multivariate analysis showed that this marker combination is independent of tumor size,histological grade,nodal status,ER-,PR,- and HER2-status. In this cohort,ALDH1 expression alone does not significantly predict outcome. We conclude that the multiplexed method of in situ identification of putative CSCs identifies high risk patients in breast cancer. View Publication

High aldehyde dehydrogenase (ALDH) activity has recently been used to identify tumorigenic cell fractions in many cancer types. Herein we hypothesized that a subpopulation of cells with cancer stem cells (CSCs) properties could be identified in established human osteosarcoma cell lines based on high ALDH activity. We previously showed that a subpopulation of cells with high ALDH activity were present in 4 selected human osteosarcoma cell lines,of which a significantly higher ALDH activity was present in the OS99-1 cell line that was originally derived from a highly aggressive primary human osteosarcoma. Using a xenograft model in which OS99-1 cells were grown in NOD/SCID mice,we identified a highly tumorigenic subpopulation of osteosarcoma cells based on their high ALDH activity. Cells with high ALDH activity (ALDH(br) cells) from the OS99-1 xenografts were much less frequent,averaging 3% of the entire tumor population,compared to those isolated directly from the OS99-1 cell line. ALDH(br) cells from the xenograft were enriched with greater tumorigenicity compared to their counterparts with low ALDH activity (ALDH(lo) cells),generating new tumors with as few as 100 cells in vivo. The highly tumorigenic ALDH(br) cells illustrated the stem cell characteristics of self-renewal,the ability to produce differentiated progeny and increased expression of stem cell marker genes OCT3/4A,Nanog and Sox-2. The isolation of osteosarcoma CSCs by their high ALDH activity may provide new insight into the study of osteosarcoma-initiating cells and may potentially have therapeutic implications for human osteosarcoma. View Publication

More recently,reprogramming of somatic cells to an embryonic stem cell-like state presents a milestone in the realm of stem cells,making it possible to derive all cell types from any patients bearing specific genetic mutations. With the development of induced pluripotent stem (iPS) cells,we are now able to use the derivatives of iPS cells to study the mechanisms of disease and to perform drug screening and toxicology testing. In addition,differentiated iPS cells are now close to be used in clinical practice. Here we review the progress of iPS technique and the possible application in the area of Parkinson's disease treatment. View Publication

We have systematically developed single cell-inoculated suspension cultures of human embryonic stem cells (hESC) in defined media. Cell survival was dependent on hESC re-aggregation. In the presence of the Rho kinase inhibitor Y-27632 (Ri) only ∼ 44% of the seeded cells were rescued,but an optimized heat shock treatment combined with Ri significantly increased cell survival to ∼ 60%. Mechanistically,our data suggest that E-cadherin plays a role in hESC aggregation and that dissociation and re-aggregation upon passaging functions as a purification step towards a pluripotency markers-enriched population. Mass expansion of hESC was readily achieved by up-scaling 2 ml cultures to serial passaging in 50 ml spinner flasks. A media comparison revealed that mTeSR was superior to KnockOut-SR in supporting cell proliferation and pluripotency. Persistent expression of pluripotency markers was achieved for two lines (hES2,hES3) that were used at higher passages (textgreater 86). In contrast,rapid down regulation of Oct4,Tra-1-60,and SSEA4 was observed for ESI049,a clinically compliant line,used at passages 20-36. The up-scaling strategy has significant potential to provide pluripotent cells on a clinical scale. Nevertheless,our data also highlights a significant line-to-line variability and the need for a critical assessment of novel methods with numerous relevant cell lines. textcopyright 2010 Elsevier B.V. All rights reserved. View Publication

Whether garcinol,the active component of Garcinia indica,can modulate the sensitivity of cancer cells to TRAIL,a cytokine currently in phase II clinical trial,was investigated. We found that garcinol potentiated TRAIL-induced apoptosis of cancer cells as indicated by intracellular esterase activity,DNA strand breaks,accumulation of the membrane phospholipid phosphatidylserine,mitochondrial activity,and activation of caspase-8,-9,and -3. We found that garcinol,independent of the cell type,induced both of the TRAIL receptors,death receptor 4 (DR4) and DR5. Garcinol neither induced the receptors on normal cells nor sensitized them to TRAIL. Deletion of DR5 or DR4 by small interfering RNA significantly reduced the apoptosis induced by TRAIL and garcinol. In addition,garcinol downregulated various cell survival proteins including survivin,bcl-2,XIAP,and cFLIP,and induced bid cleavage,bax,and cytochrome c release. Induction of death receptors by garcinol was found to be independent of modulation of CCAAT/enhancer-binding protein-homologous protein,p53,bax,extracellular signal-regulated kinase,or c-Jun-NH(2)-kinase. The effect of garcinol was mediated through the generation of reactive oxygen species,in as much as induction of both death receptors,modulation of antiapoptotic and proapoptotic proteins,and potentiation of TRAIL-induced apoptosis were abolished by N-acetyl cysteine and glutathione. Interestingly,garcinol also converted TRAIL-resistant cells into TRAIL-sensitive cells. Overall,our results indicate that garcinol can potentiate TRAIL-induced apoptosis through upregulation of death receptors and downregulation of antiapoptotic proteins. Mol Cancer Ther; 9(4); 856-68. (c)2010 AACR. View Publication

Numerous publications have described the importance of bone morphogenetic protein (BMP) signaling in the specification of hematopoietic tissue in developing embryos. Here we investigate the full role of canonical BMP signaling in both adult and fetal liver hematopoiesis using conditional knockout strategies because conventional disruption of components of the BMP signaling pathway result in early death of the embryo. By targeting both Smad1 and Smad5,we have generated a double-knockout mouse with complete disruption of canonical BMP signaling. Interestingly,concurrent deletion of Smad1 and Smad5 results in death because of extrahematopoietic pathologic changes in the colon. However,Smad1/Smad5-deficient bone marrow cells can compete normally with wild-type cells and display unaffected self-renewal and differentiation capacity when transplanted into lethally irradiated recipients. Moreover,although BMP receptor expression is increased in fetal liver,fetal liver cells deficient in both Smad1 and Smad5 remain competent to long-term reconstitute lethally irradiated recipients in a multilineage manner. In conclusion,canonical BMP signaling is not required to maintain either adult or fetal liver hematopoiesis,despite its crucial role in the initial patterning of hematopoiesis in early embryonic development. View Publication

Human amnion epithelial cells (hAECs) are a heterologous population positive for stem cell markers; they display multilineage differentiation potential,differentiating into cells of the endoderm (liver,lung epithelium),mesoderm (bone,fat),and ectoderm (neural cells). They have a low immunogenic profile and possess potent immunosuppressive properties. Hence,hAECs may be a valuable source of cells for cell therapy. This unit describes an efficient and effective method of hAEC isolation,culture,and cryopreservation that is animal product-free and in accordance with current guidelines on preparation of cells for clinical use. Cells isolated using this method were characterized after 5 passages by analysis of karyotype,cell cycle distribution,and changes in telomere length. The differentiation potential of hAECs isolated using this animal product-free method was demonstrated by differentiation into lineages of the three primary germ layers and expression of lineage-specific markers analyzed by PCR,immunocytochemistry,and histology. View Publication

BACKGROUND: We recently reported that gastrointestinal (GI) cancer cells can be reprogrammed to a pluripotent state by the ectopic expression of defined embryonic stem (ES)-like transcriptional factors. The induced pluripotent cancer (iPC) cells from GI cancer were sensitized to chemotherapeutic agents and differentiation-inducing treatment during a short-term culture,although a phenotype induced by long-term culture needs to be studied. METHODS: A long-term cultured (Lc)-iPC cells were produced in GI cancer cell lines by virus-mediated introduction of four ES-like genes-c-MYC,SOX2,OCT3/4,and KLF4-followed by a culture more than three months after iPC cells induction. An acquired state was studied by expression of immature-related surface antigens,Tra-1-60,Tra-1-81,Tra-2-49,and Ssea-4; and epigenetic trimethyl modification at lysine 4 of histone H3. Sensitivity to chemotherapeutic agents and tumorigenicity were studied in Lc-iPC cells. RESULTS: Whereas the introduction of defined factors of iPC cells once induced an immature state and sensitized cells to therapeutic reagents,the endogenous expression of the ES-like genes except for activated endogenous c-MYC was down-regulated in a long-term culture,suggesting a high magnitude of the reprogramming induction by defined factors and the requirement of therapeutic maintenance in Lc-iPC cells from cholangiocellular carcinoma HuCC-T1 cells,which harbor TP53(R175H) and KRAS(G12D). The Lc-iPC cells showed resistance to 5-fluorouracil in culture,and high tumorigenic ability with activated endogenous c-MYC in immunodeficient mice. CONCLUSION: The Lc-iPC cells from HuCC-T1 might be prone to an undesirable therapeutic response because of an association with the activated endogenous c-MYC. To consider the possible therapeutic approach in GI cancer,it would be necessary to develop a predictive method for evaluating the improper reprogramming-associated aggressive phenotype of iPC cells. View Publication

Using a high-throughput chemical screen,we identified two small molecules that enhance the survival of human embryonic stem cells (hESCs). By characterizing their mechanisms of action,we discovered an essential role of E-cadherin signaling for ESC survival. Specifically,we showed that the primary cause of hESC death following enzymatic dissociation comes from an irreparable disruption of E-cadherin signaling,which then leads to a fatal perturbation of integrin signaling. Furthermore,we found that stability of E-cadherin and the resulting survival of ESCs were controlled by specific growth factor signaling. Finally,we generated mESC-like hESCs by culturing them in mESC conditions. And these converted hESCs rely more on E-cadherin signaling and significantly less on integrin signaling. Our data suggest that differential usage of cell adhesion systems by ESCs to maintain self-renewal may explain their profound differences in terms of morphology,growth factor requirement,and sensitivity to enzymatic cell dissociation. View Publication

Accidental insertional activation of proto-oncogenes and potential vector mobilization pose serious challenges for human gene therapy using retroviral vectors. Comparative analyses of integration sites of different retroviral vectors have elucidated distinct target site preferences,highlighting vectors based on the alpharetrovirus Rous sarcoma virus (RSV) as those with the most neutral integration spectrum. To date,alpharetroviral vector systems are based mainly on single constructs containing viral coding sequences and intact long terminal repeats (LTR). Even though they are considered to be replication incompetent in mammalian cells,the transfer of intact viral genomes is unacceptable for clinical applications,due to the risk of vector mobilization and the potentially immunogenic expression of viral proteins,which we minimized by setting up a split-packaging system expressing the necessary viral proteins in trans. Moreover,intact LTRs containing transcriptional elements are capable of activating cellular genes. By removing most of these transcriptional elements,we were able to generate a self-inactivating (SIN) alpharetroviral vector,whose LTR transcriptional activity is strongly reduced and whose transgene expression can be driven by an internal promoter of choice. Codon optimization of the alpharetroviral Gag/Pol expression construct and further optimization steps allowed the production of high-titer self-inactivating vector particles in human cells. We demonstrate proof of principle for the versatility of alpharetroviral SIN vectors for the genetic modification of murine and human hematopoietic cells at a low multiplicity of infection. View Publication