技术资料

Transcriptional profiling of differentiating human embryonic stem cells (hESCs) revealed that MIXL1-positive mesodermal precursors were enriched for transcripts encoding the G-protein-coupled APELIN receptor (APLNR). APLNR-positive cells,identified by binding of the fluoresceinated peptide ligand,APELIN (APLN),or an anti-APLNR mAb,were found in both posterior mesoderm and anterior mesendoderm populations and were enriched in hemangioblast colony-forming cells (Bl-CFC). The addition of APLN peptide to the media enhanced the growth of embryoid bodies (EBs),increased the expression of hematoendothelial genes in differentiating hESCs,and increased the frequency of Bl-CFCs by up to 10-fold. Furthermore,APLN peptide also synergized with VEGF to promote the growth of hESC-derived endothelial cells. These studies identified APLN as a novel growth factor for hESC-derived hematopoietic and endothelial cells. View Publication

Studies in the past have illuminated the potential benefit of resveratrol as an anticancer (pro-apoptosis) and life-extending (pro-survival) compound. However,these two different effects were observed at different concentration ranges. Studies of resveratrol in a wide range of concentrations on the same cell type are lacking,which is necessary to comprehend its diverse and sometimes contradictory cellular effects. In this study,we examined the effects of resveratrol on cell self-renewal and differentiation of human mesenchymal stem cells (hMSCs),a type of adult stem cells that reside in a number of tissues,at concentrations ranging from 0.1 to 10 µM after both short- and long-term exposure. Our results reveal that at 0.1 µM,resveratrol promotes cell self-renewal by inhibiting cellular senescence,whereas at 5 µM or above,resveratrol inhibits cell self-renewal by increasing senescence rate,cell doubling time and S-phase cell cycle arrest. At 1 µM,its effect on cell self-renewal is minimal but after long-term exposure it exerts an inhibitory effect,accompanied with increased senescence rate. At all concentrations,resveratrol promotes osteogenic differentiation in a dosage dependent manner,which is offset by its inhibitory effect on cell self-renewal at high concentrations. On the contrary,resveratrol suppresses adipogenic differentiation during short-term exposure but promotes this process after long-term exposure. Our study implicates that resveratrol is the most beneficial to stem cell development at 0.1 µM and caution should be taken in applying resveratrol as an anticancer therapeutic agent or nutraceutical supplement due to its dosage dependent effect on hMSCs. View Publication

The sodium-iodine symporter (NIS) is expressed on the cell membrane of many thyroid cancer cells,and is responsible for the radioactive iodine accumulation. However,treatment of anaplastic thyroid cancer is ineffective due to the low expression of NIS on cell membranes of these tumor cells. Human embryonic stem cells (ESCs) provide a potential vehicle to study the mechanisms of NIS expression regulation during differentiation. Human ESCs were maintained on feeder-independent culture conditions. RT-qPCR and immunocytochemistry were used to study differentiation marker expression,(125)I uptake to study NIS function. We designed a two-step protocol for human ESC differentiation into thyroid-like cells,as was previously done for mouse embryonic stem cells. First,we obtained definitive endoderm from human ESCs. Second,we directed differentiation of definitive endoderm cells into thyroid-like cells using various factors,with thyroid stimulating hormone (TSH) as the main differentiating factor. Expression of pluripotency,endoderm and thyroid markers and (125)I uptake were monitored throughout the differentiation steps. These approaches did not result in efficient induction of thyroid-like cells. We conclude that differentiation of human ESCs into thyroid cells cannot be induced by TSH media supplementation alone and most likely involves complicated developmental patterns that are yet to be understood. View Publication

PURPOSE:
Human embryonic stem cells (hESC) hold a great potential for regenerative medicine because,in principle,they can differentiate into any cell type found in the human body. In addition,studying the effect of ionizing radiation (IR) on hESC may provide valuable information about the response of human cells to IR exposure in their most naive state,as well as the consequences of IR exposure on the development of organisms. However,the effect of IR,in particular radionuclide uptake,on the pluripotency,proliferation and survival of hESC has not been extensively studied.
METHODS:
In this study we treated cultured hESC with 5-[(125)I]iodo-2'-deoxyuridine ((125)IdU),a precursor of DNA synthesis. Then we measured the expansion of colonies and expression of pluripotency markers in hESC.
RESULTS:
We found that uptake of (125)IdU was similar in both hESC and HT1080 human fibrosarcoma cells. However,treatment with 0.1 μCi/ml (125)IdU for 24 hours resulted in complete death of the hESC population; whereas HT1080 cancer cells continued to grow. Treatment with a 10-fold lower dose (125)IdU (0.01 μCi/ml) resulted in colonies of hESC becoming less defined with numerous cells growing in monolayer outside of the colonies showing signs of differentiation. Then we analyzed the expression of pluripotency markers (octamer-binding transcription factor 4 [Oct-4] and stage-specific embryonic antigen-4 [SSEA4]) in the surviving hESC. We found that hESC in the surviving colonies expressed pluripotency markers at levels comparable with those in the non-treated controls.
CONCLUSIONS:
Our results provide important initial insights into the sensitivity of hESC to IR,and especially that produced by the decay of an internalized radionuclide. View Publication

Cellular reprogramming from adult somatic cells into an embryonic cell-like state,termed induced pluripotency,has been achieved in several cell types. However,the ability to reprogram human amniotic epithelial cells (hAECs),an abundant cell source derived from discarded placental tissue,has only recently been investigated. Here we show that not only are hAECs easily reprogrammed into induced pluripotent stem cells (AE-iPSCs),but hAECs reprogram faster and more efficiently than adult and neonatal somatic dermal fibroblasts. Furthermore,AE-iPSCs express higher levels of NANOG and OCT4 compared to human foreskin fibroblast iPSCs (HFF1-iPSCs) and express decreased levels of genes associated with differentiation,including NEUROD1 and SOX17,markers of neuronal differentiation. To elucidate the mechanism behind the higher reprogramming efficiency of hAECs,we analyzed global DNA methylation,global histone acetylation,and the mitochondrial DNA A3243G point mutation. Whereas hAECs show no differences in global histone acetylation or mitochondrial point mutation accumulation compared to adult and neonatal dermal fibroblasts,hAECs demonstrate a decreased global DNA methylation compared to dermal fibroblasts. Likewise,quantitative gene expression analyses show that hAECs endogenously express OCT4,SOX2,KLF4,and c-MYC,all four factors used in cellular reprogramming. Thus,hAECs represent an ideal cell type for testing novel approaches for generating clinically viable iPSCs and offer significant advantages over postnatal cells that more likely may be contaminated by environmental exposures and infectious agents. View Publication

Stem cell (SC) lines that capture the genetics of disease susceptibility provide new research tools. To assess the utility of mouse central nervous system (CNS) SC-containing neurosphere cultures for studying heritable neurodegenerative disease,we compared neurosphere cultures from transgenic mice that express human tau with the P301L familial frontotemporal dementia (FTD) mutation,rTg(tau(P301L))4510,with those expressing comparable levels of wild type human tau,rTg(tau(wt))21221. rTg(tau(P301L))4510 mice express the human tau(P301L) variant in their forebrains and display cellular,histological,biochemical and behavioral abnormalities similar to those in human FTD,including age-dependent differences in tau phosphorylation that distinguish them from rTg(tau(wt))21221 mice. We compared FTD-hallmark tau phosphorylation in neurospheres from rTg(tau(P301L))4510 mice and from rTg(tau(wt))21221 mice. The tau genotype-specific phosphorylation patterns in neurospheres mimicked those seen in mice,validating use of neurosphere cultures as models for studying tau phosphorylation. Genotype-specific tau phosphorylation was observed in 35 independent cell lines from individual fetuses; tau in rTg(tau(P301L))4510 cultures was hypophosphorylated in comparison with rTg(tau(wt))21221 as was seen in young adult mice. In addition,there were fewer human tau-expressing cells in rTg(tau(P301L))4510 than in rTg(tau(wt))21221 cultures. Following differentiation,neuronal filopodia-spine density was slightly greater in rTg(tau(P301L))4510 than rTg(tau(wt))21221 and control cultures. Together with the recapitulation of genotype-specific phosphorylation patterns,the observation that neurosphere lines maintained their cell line-specific-differences and retained SC characteristics over several passages supports the utility of SC cultures as surrogates for analysis of cellular disease mechanisms. View Publication

Human embryonic stem cells (hESCs) hold great promise for regenerative medicine because they can undergo unlimited self-renewal and retain the capability to differentiate into all cell types in the body. Although numerous genes/proteins such as Oct4 and Gata6 have been identified to play critical regulatory roles in self-renewal and differentiation of hESC,the majority of the regulators in these cellular processes and more importantly how these regulators co-operate with each other and/or with epigenetic modifications are still largely unknown. We propose here a systematic approach to integrate genomic and epigenomic data for identification of direct regulatory interactions. This approach allows reconstruction of cell-type-specific transcription networks in embryonic stem cells (ESCs) and fibroblasts at an unprecedented scale. Many links in the reconstructed networks coincide with known regulatory interactions or literature evidence. Systems-level analyses of these networks not only uncover novel regulators for pluripotency and differentiation,but also reveal extensive interplays between transcription factor binding and epigenetic modifications. Especially,we observed poised enhancers characterized by both active (H3K4me1) and repressive (H3K27me3) histone marks that contain enriched Oct4- and Suz12-binding sites. The success of such a systems biology approach is further supported by experimental validation of the predicted interactions. View Publication

Considerable progress has been made in identifying signaling pathways that direct the differentiation of human pluripotent stem cells (hPSCs) into specialized cell types,including neurons. However,differentiation of hPSCs with extrinsic factors is a slow,step-wise process,mimicking the protracted timing of human development. Using a small-molecule screen,we identified a combination of five small-molecule pathway inhibitors that yield hPSC-derived neurons at textgreater75% efficiency within 10 d of differentiation. The resulting neurons express canonical markers and functional properties of human nociceptors,including tetrodotoxin (TTX)-resistant,SCN10A-dependent sodium currents and response to nociceptive stimuli such as ATP and capsaicin. Neuronal fate acquisition occurs about threefold faster than during in vivo development,suggesting that use of small-molecule pathway inhibitors could become a general strategy for accelerating developmental timing in vitro. The quick and high-efficiency derivation of nociceptors offers unprecedented access to this medically relevant cell type for studies of human pain. View Publication

Sox2 (sex-determining region Y-box protein 2) is a transcription factor regulating pluripotency in embryonic stem cells. Sox2 is aberrantly expressed in breast and other cancers,though its biological significance remains widely unexplored. To understand the significance of this aberrancy,we assessed the transcription activity of Sox2 in two Sox2-expressing breast cancer cell lines,MCF7 and ZR751,using a lentiviral Sox2 GFP reporter vector. Surprisingly,Sox2 transcription activity,as measured by GFP expression encoded in a Sox2 reporter construct,was detectable only in a small subset of cells in both cell lines. Purification of GFP+ cells (cells with Sox2 activity) and GFP- cells (cells without Sox2 activity) was enriched for two phenotypically distinct cell populations in both MCF7 and ZR751 cell lines. Specifically,GFP+ cells formed significantly more colonies in methylcellulose and more mammospheres in vitro compared to GFP- cells. These phenotypic differences are directly linked to Sox2 as siRNA knockdown of Sox2 in GFP+ cells abolished these abilities. To provide a mechanistic explanation to our observations,we performed gel shift and chromatin immunoprecipitation studies; Sox2 was found to bind to its DNA binding consensus sequence and the promoters of Cyclin D1 and Nanog (two known Sox2 downstream targets) only in GFP+ cells. GFP+ cells also up-regulated CD49f,phospho-GSK3$$,and $$-catenin. In summary,we have identified two novel phenotypically distinct cell subsets in two breast cancer cell lines based on their differential Sox2 transcription activity. We demonstrate that Sox2 transcription activity,and not its protein expression alone,underlies the tumorigenicity and cancer stem cell-like phenotypes in breast cancers. View Publication

Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) induces apoptosis specifically in tumor cells and its efficacy has been tested in pre-clinical models by delivering it systemically as a purified ligand or via engineered stem cells (SC). However,about 50% of tumor lines are resistant to TRAIL and overcoming TRAIL resistance in aggressive tumors,such as glioblastoma-multiforme (GBM),and understanding the molecular dynamics of TRAIL-based combination therapies are critical to broadly use TRAIL as a therapeutic agent. In this study,we developed death receptor (DR)4/5-reporters that offer an imaging-based platform to identify agents that act in concert with a potent,secretable variant of TRAIL (S-TRAIL) by monitoring changes in DR4/5 expression. Utilizing these reporters,we show a differential regulation of DR4/5 when exposed to a panel of clinically relevant agents. A histone deacetylase inhibitor,MS-275,resulted in upregulation of DR4/5 in all GBM cell lines,and these changes could be followed in real time both in vitro and in vivo in mice bearing tumors and they correlated with increased TRAIL sensitivity. To further assess the dynamics of combinatorial strategies that overcome resistance of tumors to SC released S-TRAIL,we also engineered tumor cells to express live-cell caspase-reporters and SCs to express S-TRAIL. Utilizing DR4/5 and caspase reporters in parallel,we show that MS-275 sensitizes TRAIL-resistant GBM cells to stem cell (SC) delivered S-TRAIL by changing the time-to-death in vitro and in vivo. This study demonstrates the effectiveness of a combination of real-time reporters of TRAIL-induced apoptosis pathway in evaluating the efficacy of SC-TRAIL-based therapeutics and may have implications in targeting a broad range of cancers. View Publication

Aromatase inhibitors (AIs) are an effective therapy in treating estrogen receptor-positive breast cancer. Nonetheless,a significant percentage of patients either do not respond or become resistant to AIs. Decreased dependence on ER-signaling and increased dependence on growth factor receptor signaling pathways,particularly human epidermal growth factor receptor 2 (EGFR2/HER2),have been implicated in AI resistance. However,the role of growth factor signaling remains unclear. This current study investigates the possibility that signaling either through HER2 alone or through interplay between epidermal growth factor receptor 1 (EGFR/HER1) and HER2 mediates AI resistance by increasing the tumor initiating cell (TIC) subpopulation in AI-resistant cells via regulation of stem cell markers,such as breast cancer resistance protein (BCRP). TICs and BCRP are both known to be involved in drug resistance. Results from in vitro analyses of AI-resistant versus AI-sensitive cells and HER2-versus HER2+ cells,as well as from in vivo xenograft tumors,indicate that (1) AI-resistant cells overexpress both HER2 and BCRP and exhibit increased TIC characteristics compared to AI-sensitive cells; (2) inhibition of HER2 and/or BCRP decrease TIC characteristics in letrozole-resistant cells; and (3) HER2 and its dimerization partner EGFR/HER1 are involved in the regulation of BCRP. Overall,these results suggest that reducing or eliminating the TIC subpopulation with agents that target BCRP,HER2,EGFR/HER1,and/or their downstream kinase pathways could be effective in preventing and/or treating acquired AI resistance. View Publication

INTRODUCTION: Retinoic acid signaling plays key roles in embryonic development and in maintaining the differentiated status of adult tissues. Recently,the nuclear retinoic acid receptor (RAR) isotypes α,β and γ were found to play specific functions in the expansion and differentiation of the stem compartments of various tissues. For instance,RARγ appears to be involved in stem cell compartment expansion,while RARα and RARβ are implicated in the subsequent cell differentiation. We found that over-expressing c-Myc in normal mouse mammary epithelium and in a c-Myc-driven transgenic model of mammary cancer,disrupts the balance between RARγ and RARα/β in favor of RARγ. METHODS: The effects of c-Myc on RAR isotype expression were evaluated in normal mouse mammary epithelium,mammary tumor cells obtained from the MMTV-Myc transgenic mouse model as well as human normal immortalized breast epithelial and breast cancer cell lines. The in vivo effect of the RARα-selective agonist 4-[(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthyl)carboxamido]benzoic acid (Am580) was examined in the MMTV-Myc mouse model of mammary tumorigenesis. RESULTS: Modulation of the RARα/β to RARγ expression in mammary glands of normal mice,oncomice,and human mammary cell lines through the alteration of RAR-target gene expression affected cell proliferation,survival and tumor growth. Treatment of MMTV-Myc mice with the RARα-selective agonist Am580 led to significant inhibition of mammary tumor growth (˜90%,Ptextless0.001),lung metastasis (Ptextless0.01) and extended tumor latency in 63% of mice. Immunocytochemical analysis showed that in these mice,RARα responsive genes such as Cyp26A1,E-cadherin,cellular retinol-binding protein 1 (CRBP1) and p27,were up-regulated. In contrast,the mammary gland tumors of mice that responded poorly to Am580 treatment (37%) expressed significantly higher levels of RARγ. In vitro experiments indicated that the rise in RARγ was functionally linked to promotion of tumor growth and inhibition of differentiation. Thus,activation of the RARα pathway is linked to tumor growth inhibition,differentiation and cell death. CONCLUSIONS: The functional consequence of the interplay between c-Myc oncogene expression and the RARγ to RARα/β balance suggests that prevalence of RARγ over-RARα/β expression levels in breast cancer accompanied by c-Myc amplification or over-expression in breast cancer should be predictive of response to treatment with RARα-isotype-specific agonists and warrant monitoring during clinical trials. View Publication