• Journal of Life Science
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• v.34 no.6
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• pp.418-425
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• 2024

Solid tumors are heterogeneous populations of multiple cell types. While the majority of the cells that comprise cancer are unable to divide, cancer stem cells have self-renewal and differentiation properties. Normal stem cell pathways that control self-renewal are overactivated in cancer stem cells, making cancer stem cells important for cancer cell expansion and progression. Dick first proposed the definition of cancer stem cells in acute myeloid leukemia, according to which cancer stem cells can be classified based on the expression of cell surface markers. Cancer stem cells maintain their potential in the tumor microenvironment. Multiple cell types in the tumor microenvironment maintain quiescent cancer stem cells and serve as regulators of cancer growth. Since current cancer treatments target proliferative cells, quiescent state cancer stem cells that are resistant to treatment increase the risk of recurrence or metastasis. Various signals of the tumor microenvironment induce changes to become a tumor-supportive environment by remodeling the vasculature and extracellular matrix. To effectively treat cancer, cancer stem cells and the tumor microenvironment must be targeted. Therefore, it is important to understand how the tumor microenvironment induces reprogramming of the immune response to promote cancer growth, immune resistance, and metastasis. In this review, we discuss the cellular and molecular mechanisms that can enhance immunosuppression in the tumor microenvironment.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2004.07a
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• pp.32-32
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• 2004

• Proceedings of the Korean Statistical Society Conference
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• 2003.05a
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• pp.177-182
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• 2003

• Development and Reproduction
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• v.12 no.1
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• pp.87-95
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• 2008

Neural stem/precursor derived from pluripotent human embryonic stem cells (hESCs) has considerable therapeutic potential due to their ability to generate various neural cells which can be used in cell-replacement therapies for neurodegenerative diseases. However, production of neural cells from hESCs remains technically very difficult. Understanding neural-tube like rosette characteristic neural precursor cells from hESCs may provide useful information to increase the efficiency of hESC neural differentiation. Generally, neural rosettes were derived from differentiating hEBs in attached culture system, however this is time-consuming and complicated. Here, we examined if neural rosettes could be formed in suspension culture system by bypassing attachment requirement. First, we tested whether the size of hESC clumps affected the formation of human embryonic bodies (hEBs) and neural differentiation. We confirmed that hEBs derived from $500{\times}500\;{\mu}m$ square sized hESC clumps were effectively differentiated into neural lineage than those of the other sizes. To induce the rosette formation, regular size hEBs were derived by incubation of hESC clumps($500{\times}500\;{\mu}m$) in EB medium for 1 wk in a suspended condition on low attachment culture dish and further incubated for additional $1{\sim}2$ wks in neuroectodermal sphere(NES)-culture medium. We observed the neural tube-like rosette structure from hEBs after $7{\sim}10$ days of differentiation. Their identity as a neural precursor cells was assessed by measuring their expressions of neural precursor markers(Vimentin, Nestin, MSI1, MSI2, Prominin-1, Pax6, Sox1, N-cadherin, Otx2, and Tuj1) by RT-PCR and immunofluorescence staining. We also confirmed that neural rosettes could be terminally differentiated into mature neural cell types by additional incubation for $2{\sim}6$ wks with NES medium without growth factors. Neuronal(Tuj1, MAP2, GABA) and glial($S100{\beta}$ and GFAP) markers were highly expressed after $2{\sim}3$ and 4 wks of incubation, respectively. Expression of oligodendrocyte markers O1 and CNPase was significantly increased after $5{\sim}6$ wks of incubation. Our results demonstrate that rosette forming neural precursor cells could be successfully derived from suspension culture system and that will not only help us understand the neural differentiation process of hESCs but also simplify the derivation process of neural precursors from hESCs.

• Development and Reproduction
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• v.11 no.2
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• pp.59-66
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• 2007

Understanding molecular mechanisms that control embryonic stem cell (ESC) self-renewal and differentiation is important for the development of ESC-based therapies. Statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase), potently reduce cholesterol level. As well as inhibiting cholesterol synthesis, statins inhibit other intermediates in the mevalonate pathway such as farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), major substrates for protein isoprenylation. Studies showed that pleiotropic effects of statins beyond cholesterol lowering property arise from inhibition of protein isoprenylation that is involved in various cellular functions including proliferation and differentiation. It has been determined that statins have inhibitory effect on ESC self-renewal and stimulatory effect on ESC differentiation into adipogenic/osteogenic lineages. Importantly, statins mediate downregulation of ESC self-renewal by inhibiting RhoA-dependent signaling, independently of their choresterol-lowering properties. Understanding statin's actions on ESCs may provide important insights into the molecular mechanisms that regulate self-renewal or differentiation of ESCs.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.3
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• pp.337-342
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• 2019

The aim of this study was to analyze cells from human dental pulp tissue of impacted supernumerary teeth as stem cells with flow cytometry. Human dental pulp cells from 15 supernumerary teeth were identified their characteristics as stem cells by expression of mesenchymal stem cell markers through flow cytometry analysis at passage 3 and passage 10. Cluster of differentiation (CD) 73, CD 90, CD 34, CD 45 and STRO-1 cell surface markers were used to figure out characteristics of dental pulp stem cells from supernumerary teeth. At passage 3, the cell population showed positive expression of CD 73, CD90 and STRO-1, lacked expression of CD 34 and CD 45. At passage 10, CD 73, CD 90 and STRO-1 showed positive expression while CD 34 and CD 45 showed negative expression. This study indicated that dental pulp stem cells of supernumerary teeth had the properties of mesenchymal stem cells at both early and late passage. Impacted supernumerary teeth could be considered as a noble source of stem cells because of rapid growth and maintaining characteristics of stem cells until late passage.

• Journal of Life Science
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• v.17 no.5 s.85
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• pp.678-686
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• 2007

Human mesenchymal stem cells(hMSC), that have been reported to be present in bone marrow, adipose tissues, dermis, muscles and peripheral blood, have the potential to differentiate along different lineages including those forming bone, cartilage, fat, muscle and neuron. Therefore, hMSC are attractive candidates for cell and gene therapy. The optimal conditions for hMSC expansion require medium supplemented with fetal bovine serum(FBS). Some forms of cell therapy will involve multiple doses, raising a concern over immunological reactions caused by medium-derived FBS proteins. Previously, we have shown that hADSC can be cultured in human serum(HS) during their isolation and expansion, and that they maintain their proliferative capacity and ability for multilineage differentiation and promote engraftment of peripheral blood-derived CD34 cells mobilized from bone marrow in NOD/SCID mice. In this study we determined whether hADSC grown in HS maintain surface markers expression similar with cells grown in FBS during culture expansion and compared gene expression profile by Affymetrix microarray. Flow cytometry analysis showed that HLA-DR, CD117, CD29 and CD44 expression in HS-cultured hADSC during culture expansion were similar with that in FBS-cultured cells. However, the gene expression profile in HS-cultured hADSC was significantly different from that in FBS-cultured cells. Therefore, these data indicated that HS-cultured hADSC should be used in vivo animal study of hADSC transplantation for direct extrapolation of preclinical data into clinical application.

• Journal of Life Science
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• v.23 no.4
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• pp.471-478
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• 2013

Human adipose tissue-derived mesenchymal stem cells (hADSCs) have therapeutic potential, including the ability to self-renew and differentiate into multiple lineages. Understanding of molecular mechanisms of stem cell differentiation is important for improving the therapeutic efficacies of stem cell transplantation. In this study, we determined the role of nuclear factor of activated T cells (NFAT5) in the osteogenic differentiation of hADSCs. The down-regulation of NFAT5 expression by the transfection of a specific siRNA significantly inhibited osteogenic differentiation of hADSCs and decreased the activity of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-${\kappa}B$) promoter without affecting their proliferation and adipogenic differentiation. The inhibition of NFAT5 expression inhibited the basal and Tumor Necrosis Factor ${\alpha}$ (TNF-${\alpha}$) induced activation of NF-${\kappa}B$, but it did not affect TNF-${\alpha}$-induced degradation of the $I{\kappa}B$ protein. These findings indicate that NFAT5 plays an important role in the osteogenic differentiation of hADSCs through the modulation of the NF-${\kappa}B$ pathway.

• Journal of Life Science
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• v.21 no.5
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• pp.631-646
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• 2011

Mesenchymal stem cells (MSC) are multipotent and can be isolated from diverse human tissues including bone marrow, fat, placenta, dental pulp, synovium, tonsil, and the thymus. They function as regulators of tissue homeostasis. Because of their various advantages such as plasticity, easy isolation and manipulation, chemotaxis to cancer, and immune regulatory function, MSCs have been considered to be a potent cell source for regenerative medicine, cancer treatment and other cell based therapy such as GVHD. However, relating to its supportive feature for surrounding cell and tissue, it has been frequently reported that MSCs accelerate tumor growth by modulating cancer microenvironment through promoting angiogenesis, secreting growth factors, and suppressing anti-tumorigenic immune reaction. Thus, clinical application of MSCs has been limited. To understand the underlying mechanism which modulates MSCs to function as tumor supportive cells, we co-cultured human adipose tissue derived mesenchymal stem cells (ASC) with cancer cell lines H460 and U87MG. Then, expression data of ASCs co-cultured with cancer cells and cultured alone were obtained via microarray. Comparative expression analysis was carried out using DAVID (Database for Annotation, Visualization and Integrated Discovery) and PANTHER (Protein ANalysis THrough Evolutionary Relationships) in divers aspects including biological process, molecular function, cellular component, protein class, disease, tissue expression, and signal pathway. We found that cancer cells alter the expression profile of MSCs to cancer associated fibroblast like cells by modulating its energy metabolism, stemness, cell structure components, and paracrine effect in a variety of levels. These findings will improve the clinical efficacy and safety of MSCs based cell therapy.

• Journal of Life Science
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• v.21 no.2
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• pp.183-193
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• 2011

Migration and differentiation of mesenchymal stem cells are crucial for tissue regeneration in response to injury. Sphingosine-1-phosphate (S1P) is a bioactive lipid that regulates a variety of biological processes, including proliferation, survival, differentiation and motility. In the present study, we determined the role of S1P in migration and differentiation of human bone marrow-derived mesenchymal stem cells (BMSCs). S1P stimulated migration of BMSCs in a dose- and time-dependent manner, and pre-incubation of the cells with pertussis toxin completely abrogated S1P-induced migration, suggesting involvement of Gi-coupled receptors in S1P-induced cell migration. S1P elicited elevation of intracellular concentration of $Ca^{2+}$ ($[Ca^{2+}]_i$) and pretreatment with VPC23019, an antagonist of $S1P_1/S1P_3$, blocked S1P-induced migration and increase of $[Ca^{2+}]_i$. Small interfering RNA-mediated knockdown of endogenous $S1P_1$ attenuated S1P-induced migration of BMSCs. Furthermore, S1P treatment induced expression of $\alpha$-smooth muscle actin ($\alpha$-SMA), a smooth muscle marker, and pretreatment with VPC23019 abrogated S1P-induced $\alpha$-SMA expression. S1P induced phosphorylation of p38 mitogen-activated protein kinase (MAPK), and pretreatment of cells with SB202190, an inhibitor of p38 MAPK, or adenoviral overexpression of a dominant-negative mutant of the p38 MAPK blocked S1P-induced cell migration and $\alpha$-SMA expression. Taken together, these results suggest that S1P stimulates migration and smooth muscle differentiation of BMSCs through an $S1P_1$-p38 MAPK-dependent mechanism.