参考文献

The ST6Gal-I sialyltransferase adds an $$2-6-linked sialic acid to the N-glycans of certain receptors. ST6Gal-I mRNA has been reported to be upregulated in human cancer,but a prior lack of antibodies has limited immunochemical analysis of the ST6Gal-I protein. Here,we show upregulated ST6Gal-I protein in several epithelial cancers,including many colon carcinomas. In normal colon,ST6Gal-I localized selectively to the base of crypts,where stem/progenitor cells are found,and the tissue staining patterns were similar to the established stem cell marker ALDH1. Similarly,ST6Gal-I expression was restricted to basal epidermal layers in skin,another stem/progenitor cell compartment. ST6Gal-I was highly expressed in induced pluripotent stem (iPS) cells,with no detectable expression in the fibroblasts from which iPS cells were derived. On the basis of these observations,we investigated further an association of ST6Gal-I with cancer stem cells (CSC). Selection of irinotecan resistance in colon carcinoma cells led to a greater proportion of CSCs compared with parental cells,as measured by the CSC markers CD133 and ALDH1 activity (Aldefluor). These chemoresistant cells exhibited a corresponding upregulation of ST6Gal-I expression. Conversely,short hairpin RNA (shRNA)-mediated attenuation of ST6Gal-I in colon carcinoma cells with elevated endogenous expression decreased the number of CD133/ALDH1-positive cells present in the cell population. Collectively,our results suggest that ST6Gal-I promotes tumorigenesis and may serve as a regulator of the stem cell phenotype in both normal and cancer cell populations. View Publication

A goal in human embryonic stem cell (hESC) research is the faithful differentiation to given cell types such as neural lineages. During embryonic development,a basement membrane surrounds the neural plate that forms a tight,apico-basolaterally polarized epithelium before closing to form a neural tube with a single lumen. Here we show that the three-dimensional epithelial cyst culture of hESCs in Matrigel combined with neural induction results in a quantitative conversion into neuroepithelial cysts containing a single lumen. Cells attain a defined neuroepithelial identity by 5 days. The neuroepithelial cysts naturally generate retinal epithelium,in part due to IGF-1/insulin signaling. We demonstrate the utility of this epithelial culture approach by achieving a quantitative production of retinal pigment epithelial (RPE) cells from hESCs within 30 days. Direct transplantation of this RPE into a rat model of retinal degeneration without any selection or expansion of the cells results in the formation of a donor-derived RPE monolayer that rescues photoreceptor cells. The cyst method for neuroepithelial differentiation of pluripotent stem cells is not only of importance for RPE generation but will also be relevant to the production of other neuronal cell types and for reconstituting complex patterning events from three-dimensional neuroepithelia. View Publication

BACKGROUND: Fragile X syndrome (FXS) is a common form of inherited intellectual disability caused by an expansion of CGG repeats located in the 5' untranslated region (UTR) of the FMR1 gene,which leads to hypermethylation and silencing of this locus. Although a dramatic increase in DNA methylation of the FMR1 full mutation allele is well documented,the extent to which these changes affect DNA methylation throughout the rest of the genome has gone unexplored. METHODS: Here we examined genome-wide methylation in both peripheral blood (N = 62) and induced pluripotent stem cells (iPSCs; N = 10) from FXS individuals and controls. RESULTS: We not only found the expected significant DNA methylation differences in the FMR1 promoter and 5' UTR,we also saw that these changes inverse in the FMR1 gene body. Importantly,we found no other differentially methylated loci throughout the remainder of the genome,indicating the aberrant methylation of FMR1 in FXS is locus-specific. CONCLUSIONS: This study provides a comprehensive methylation profile of FXS and helps refine our understanding of the mechanisms behind FMR1 silencing. View Publication

The antitumor activity of LPS was first described by Dr. William Coley. However,its role in lung cancer remains unclear. The aim of our study was to elucidate the dose-dependent effects of LPS (0.1-10 μg/mouse) in a mouse model of B16-F10-induced metastatic lung cancer. Lung tumor growth increased at 3 and 7 d after the administration of low-dose LPS (0.1 μg/mouse) compared with control mice. This was associated with an influx of plasmacytoid dendritic cells (pDCs),regulatory T cells,myeloid-derived suppressor cells,and CD8(+) regulatory T cells. In contrast,high-dose LPS (10 μg/mouse) reduced lung tumor burden and was associated with a greater influx of pDCs,as well as a stronger Th1 and Th17 polarization. Depletion of pDCs during low-dose LPS administration resulted in a decreased lung tumor burden. Depletion of pDCs during high-dose LPS treatment resulted in an increased tumor burden. The dichotomy in LPS effects was due to the phenotype of pDCs,which were immunosuppressive after the low-dose LPS,and Th1- and T cytotoxic-polarizing cells after the high-dose LPS. Adoptive transfer of T cells into nude mice demonstrated that CD8(+) T cells were responsible for pDC recruitment following low-dose LPS administration,whereas CD4(+) T cells were required for pDC influx after the high-dose LPS. In conclusion,our data suggest differential effects of low-dose versus high-dose LPS on pDC phenotype and tumor progression or regression in the lungs of mice. View Publication

Rapamycin analogs,temsirolimus and everolimus,are approved for the treatment of advance renal cell carcinoma (RCC). Currently approved agents inhibit mechanistic target of rapamycin (mTOR) complex 1 (mTORC1). However,the mTOR kinase exists in two distinct multiprotein complexes,mTORC1 and mTORC2,and both complexes may be critical regulators of cell metabolism,growth and proliferation. Furthermore,it has been proposed that drug resistance develops due to compensatory activation of mTORC2 signaling during treatment with temsirolimus or everolimus. We evaluated Ku0063794,which is a small molecule that inhibits both mTOR complexes. Ku0063794 was compared to temsirolimus in preclinical models for renal cell carcinoma. Ku0063794 was effective in inhibiting the phosphorylation of signaling proteins downstream of both mTORC1 and mTORC2,including p70 S6K,4E-BP1 and Akt. Ku0063794 was more effective than temsirolimus in decreasing the viability and growth of RCC cell lines,Caki-1 and 786-O,in vitro by inducing cell cycle arrest and autophagy,but not apoptosis. However,in a xenograft model there was no difference in the inhibition of tumor growth by Ku0063794 or temsirolimus. A potential explanation is that temsirolimus has additional effects on the tumor microenvironment. Consistent with this possibility,temsirolimus,but not Ku0063794,decreased tumor angiogenesis in vivo,and decreased the viability of HUVEC (Human Umbilical Vein Endothelial Cells) cells in vitro at pharmacologically relevant concentrations. Furthermore,expression levels of VEGF and PDGF were lower in Caki-1 and 786-O cells treated with temsirolimus than cells treated with Ku0063794. View Publication

BACKGROUND: The self-renewal of human pluripotent stem (hPS) cells including embryonic stem and induced pluripotent stem cells have been reported to be supported by various signal pathways. Among them,fibroblast growth factor-2 (FGF-2) appears indispensable to maintain self-renewal of hPS cells. However,downstream signaling of FGF-2 has not yet been clearly understood in hPS cells. METHODOLOGY/PRINCIPAL FINDINGS: In this study,we screened a kinase inhibitor library using a high-throughput alkaline phosphatase (ALP) activity-based assay in a minimal growth factor-defined medium to understand FGF-2-related molecular mechanisms regulating self-renewal of hPS cells. We found that in the presence of FGF-2,an inhibitor of protein kinase C (PKC),GF109203X (GFX),increased ALP activity. GFX inhibited FGF-2-induced phosphorylation of glycogen synthase kinase-3β (GSK-3β),suggesting that FGF-2 induced PKC and then PKC inhibited the activity of GSK-3β. Addition of activin A increased phosphorylation of GSK-3β and extracellular signal-regulated kinase-1/2 (ERK-1/2) synergistically with FGF-2 whereas activin A alone did not. GFX negated differentiation of hPS cells induced by the PKC activator,phorbol 12-myristate 13-acetate whereas Gö6976,a selective inhibitor of PKCα,β,and γ isoforms could not counteract the effect of PMA. Intriguingly,functional gene analysis by RNA interference revealed that the phosphorylation of GSK-3β was reduced by siRNA of PKCδ,PKCε,and ζ,the phosphorylation of ERK-1/2 was reduced by siRNA of PKCε and ζ,and the phosphorylation of AKT was reduced by PKCε in hPS cells. CONCLUSIONS/SIGNIFICANCE: Our study suggested complicated cross-talk in hPS cells that FGF-2 induced the phosphorylation of phosphatidylinositol-3 kinase (PI3K)/AKT,mitogen-activated protein kinase/ERK-1/2 kinase (MEK),PKC/ERK-1/2 kinase,and PKC/GSK-3β. Addition of GFX with a MEK inhibitor,U0126,in the presence of FGF-2 and activin A provided a long-term stable undifferentiated state of hPS cells even though hPS cells were dissociated into single cells for passage. This study untangles the cross-talk between molecular mechanisms regulating self-renewal and differentiation of hPS cells. View Publication

AIM To investigate the expression status of periostin in colorectal cancer (CRC) to lay a foundation for managing this disease. METHODS Periostin expression status was detected by immunohistochemistry staining in 720 CRC specimens. The relationship between the periostin protein and clinicopathological factors and prognosis was subsequently determined. RESULT The periostin protein was expressed significantly higher in CD133+ tumor cells compared to CD133- tumor cells. Positively expressed periostin was observed in 218 (30.28%) of the 720 cases. Spearman correlation analysis showed that periostin expression has a linear correlation to the tumor size,histological type,lymph node metastasis,TNM stage,and postoperative liver metastasis (p=0.02,0.035,0.001,0.001,and 0.001,respectively). Multivariate analysis showed that histological type,lymph node metastasis,TNM stage,and periostin were found to be related to liver metastasis (p=0.01,0.035,0.01,and 0.001,respectively). In the Cox regression test,the histological grade,Lymph node metastasis,TNM stage,and periostin were detected as independent prognostic factors (p=0.01,0.001,0.001,and 0.001,respectively). CONCLUSION Periostin was found to be related to the liver metastasis of CRC and may be a potential target for CRC. View Publication

Studies have suggested the potential importance of Notch signaling to the cancer stem cell population in some tumors,but it is not known whether all cells in the cancer stem cell fraction require Notch activity. To address this issue,we blocked Notch activity in MCF-7 cells by expressing a dominant-negative MAML-GFP (dnMAML) construct,which inhibits signaling through all Notch receptors,and quantified the effect on tumor-initiating activity. Inhibition of Notch signaling reduced primary tumor sphere formation and side population. Functional quantification of tumor-initiating cell numbers in vivo showed a significant decrease,but not a complete abrogation,of these cells in dnMAML-expressing cells. Interestingly,when assessed in secondary assays in vitro or in vivo,there was no difference in tumor-initiating activity between the dnMAML-expressing cells and control cells. The fact that a subpopulation of dnMAML-expressing cells was capable of forming primary and secondary tumors indicates that there are Notch-independent tumor-initiating cells in the breast cancer cell line MCF-7. Our findings thus provide direct evidence for a heterogeneous cancer stem cell pool,which will require combination therapies against multiple oncogenic pathways to eliminate the tumor-initiating cell population. View Publication

Mesenchymal progenitors or stromal cells have shown promise as a therapeutic strategy for a range of diseases including heart failure. In this context,we explored the growth and differentiation potential of mesenchymal progenitors (MPs) derived in vitro from human embryonic stem cells (hESCs). Similar to MPs isolated from bone marrow,hESC derived MPs (hESC-MPs) efficiently differentiated into archetypical mesenchymal derivatives such as chondrocytes and adipocytes. Upon treatment with 5-Azacytidine or TGF-β1,hESC-MPs modified their morphology and up-regulated expression of key cardiac transcription factors such as NKX2-5,MEF2C,HAND2 and MYOCD. Nevertheless,NKX2-5+ hESC-MP derivatives did not form contractile cardiomyocytes,raising questions concerning the suitability of these cells as a platform for cardiomyocyte replacement therapy. Gene profiling experiments revealed that,although hESC-MP derived cells expressed a suite of cardiac related genes,they lacked the complete repertoire of genes associated with bona fide cardiomyocytes. Our results suggest that whilst agents such as TGF-β1 and 5-Azacytidine can induce expression of cardiac related genes,but treated cells retain a mesenchymal like phenotype. View Publication

Intracellular delivery of macromolecules is a challenge in research and therapeutic applications. Existing vector-based and physical methods have limitations,including their reliance on exogenous materials or electrical fields,which can lead to toxicity or off-target effects. We describe a microfluidic approach to delivery in which cells are mechanically deformed as they pass through a constriction 30–80% smaller than the cell diameter. The resulting controlled application of compression and shear forces results in the formation of transient holes that enable the diffusion of material from the surrounding buffer into the cytosol. The method has demonstrated the ability to deliver a range of material,such as carbon nanotubes,proteins,and siRNA,to 11 cell types,including embryonic stem cells and immune cells. When used for the delivery of transcription factors,the microfluidic devices produced a 10-fold improvement in colony formation relative to electroporation and cell-penetrating peptides. Indeed,its ability to deliver structurally diverse materials and its applicability to difficult-to-transfect primary cells indicate that this method could potentially enable many research and clinical applications. View Publication