Nanog suppresses cell migration by downregulating thymosin β4 and Rnd3

Effect of Nanog overexpression on the metastatic potential of a mouse melanoma cell line B16-BL6

Nanog, a marker and regulator of the undifferentiated state in embryonic stem cells were anticipated to be an effective enhancer of cancer metastasis. We have developed a Nanog overexpressing mouse melanoma cell line B16-BL6 (BL6). BL6 was well recognized as a cell line with a high metastatic potential. In vitro tests revealed the enhancement of cell proliferation, wound healing activity, and matrix metalloproteinase 9 (MMP9) activity. Nanog-induced up- or down-regulated genes were comprehensively analyzed by transcriptome sequencing using Nanog⁺BL6 and wild-type BL6. Principally, up-regulated genes were involved in vesicle-aided glucose transport and oxidative phosphorylation, while down-regulated genes were associated with immunosuppression and apoptosis. A marked finding was that TGF-β1 was down-regulated, because TGF-β1 has been well discussed about its suppressive/progressive dual role in cancer. In vivo test showed that the number and volume of metastatic colonies of BL6 to lung were as high as 115 colonies/lung and 5.6 mm³/lung. Under this condition, Nanog overexpression caused a progressive effect (150 colonies/lung, p = 0.25; 9.2 mm³/lung, p = 0.13) rather than a suppressive effect on the metastasis. In this study, the effectiveness of Nanog overexpression in enhancing the metastatic potential of melanoma cell lines has been demonstrated for the first time.

Single-cell proteomics reveals changes in expression during hair-cell development

Hearing and balance rely on small sensory hair cells that reside in the inner ear. To explore dynamic changes in the abundant proteins present in differentiating hair cells, we used nanoliter-scale shotgun mass spectrometry of single cells, each ~1 picoliter, from utricles of embryonic day 15 chickens. We identified unique constellations of proteins or protein groups from presumptive hair cells and from progenitor cells. The single-cell proteomes enabled the de novo reconstruction of a developmental trajectory using protein expression levels, revealing proteins that greatly increased in expression during differentiation of hair cells (e.g., OCM, CRABP1, GPX2, AK1, GSTO1) and those that decreased during differentiation (e.g., TMSB4X, AGR3). Complementary single-cell transcriptome profiling showed corresponding changes in mRNA during maturation of hair cells. Single-cell proteomics data thus can be mined to reveal features of cellular development that may be missed with transcriptomics.

Nanog suppresses the expression of vasa by directly regulating nlk1 in the early zebrafish embryo

Nanog is a homeodomain transcription factor that is essential for maintenance of pluripotency and self-renewal of embryonic stem cells (ESCs). In the present study, we demonstrate that zebrafish Nanog (zNanog) directly binds to the promoter region of zebrafish nlk1 (znlk1) by ChIP-Seq analysis and that it up-regulates the expression of znlk1 in fibroblast-like embryonic cells of Danio rerio (ZEM-2S cells) and in zebrafish embryos at 30% epiboly both at the mRNA and protein levels. In addition, compared with control (MO-C) embryos at 30% epiboly, the mRNA and protein expression of vasa and the numbers of vasa-positive cells were increased in embryos injected with zNanog morpholino (MO-zNanog). Further, injection of znlk1 mRNA into zNanog-depleted embryos restored the expression of vasa and the number of vasa-positive cells. These data indicated that zNanog up-regulates the expression of znlk1 through directly binding to the znlk1 promoter, thereby suppressing the expression of vasa. Vasa is a marker gene for PGCs. Our results suggest that zNanog plays a role in restraint of PGC cell number through regulating the expression of znlk1 in the early embryonic development. The current results provide fundamental information to support further investigation regarding the regulatory mechanism of zNanog during the development of PGCs.

Knockdown of zebrafish Nanog increases primordial germ cells during early embryonic development

Nanog is a homeodomain transcription factor that plays a prominent role in maintaining the pluripotency and self-renewal capacity of embryonic stem cells (ESCs) in mammals. Medaka Nanog is necessary for S-phase transition and proliferation during embryonic development. However, whether Nanog regulates the proliferation of primordial germ cells (PGCs) during embryonic development has not yet been investigated. In this study, we identified the homologue of the mammalian Nanog gene in zebrafish (zNanog). The expression of both zNanog mRNA and protein was demonstrated in the spermatogonia (male germ stem cells) of the testis and the early oocytes of the ovary. During the embryonic development, zNanog mRNA is expressed in the cytoplasm of PGCs, and its protein is localized to the PGC nuclei. We also found that zNanog depletion using morpholinos resulted in the increases and aberrant localization of PGCs in the zebrafish embryos from the sphere stage to the 50% epiboly stage. These data indicated that zNanog inhibits the PGCs proliferation in early embryonic development of zebrafish.

Pathophysiological Functions of Rnd3/RhoE

Rnd3, also known as RhoE, belongs to the Rnd subclass of the Rho family of small guanosine triphosphate (GTP)-binding proteins. Rnd proteins are unique due to their inability to switch from a GTP-bound to GDP-bound conformation. Even though studies of the biological function of Rnd3 are far from being concluded, information is available regarding its expression pattern, cellular localization, and its activity, which can be altered depending on the conditions. The compiled data from these studies implies that Rnd3 may not be a traditional small GTPase. The basic role of Rnd3 is to report as an endogenous antagonist of RhoA signaling-mediated actin cytoskeleton dynamics, which specifically contributes to cell migration and neuron polarity. In addition, Rnd3 also plays a critical role in arresting cell cycle distribution, inhibiting cell growth, and inducing apoptosis and differentiation. Increasing data have shown that aberrant Rnd3 expression may be the leading cause of some systemic diseases; particularly highlighted in apoptotic cardiomyopathy, developmental arrhythmogenesis and heart failure, hydrocephalus, as well as tumor metastasis and chemotherapy resistance. Therefore, a better understanding of the function of Rnd3 under different physiological and pathological conditions, through the use of suitable models, would provide a novel insight into the origin and treatment of multiple human diseases.

Stem cell transcription factor NANOG in cancers--is eternal youth a curse?

INTRODUCTION

Targeting cancer stem cells can be a more effective approach to treat cancer. NANOG is one of the key factors for maintaining the self-renewal ability and pluripotency of stem cells, including cancer stem cells. Overexpression of NANOG has been observed in various human malignancies. Several reports have suggested that NANOG contributes to carcinogenesis by initiating and preserving cancer stem cells. It is obvious that NANOG is also involved in establishing other hallmarks of cancer such as uncontrolled cell growth, chemoresistance, metastasis, and immune evasion.

AREAS COVERED

This review will discuss the molecular properties and oncogenic roles of NANOG. The idea of using agents that inhibit the transcription factor to treat cancer is presented. Interfering with NANOG-mediated transcriptions using small interfering RNA, transcription factor decoy, genome editing, and small-molecule inhibitors may provide novel strategies to target cancer stem cells.

EXPERT OPINION

As a pivotal controller in cancer stem cell maintenance and a positive regulator of various oncogenic pathways, NANOG may be an important target for cancer therapy. However, as a transcription factor, it is inherently difficult to target by pharmacological means. Novel approaches need to be explored before the inhibition of NANOG can be applied in a clinical setting.

Overexpression of Oct4 suppresses the metastatic potential of breast cancer cells via Rnd1 downregulation

Although Oct4 is known as a critical transcription factor involved in maintaining "stemness", its role in tumor metastasis is still controversial. Herein, we overexpressed and silenced Oct4 expression in two breast cancer cell lines, MDA-MB-231 and 4T1, separately. Our data showed that ectopic overexpression of Oct4 suppressed cell migration and invasion in vitro and the formation of metastatic lung nodules in vivo. Conversely, Oct4 downregulation increased the metastatic potential of breast cancer cells both in vitro and in vivo. Furthermore, we identified Rnd1 as the downstream target of Oct4 by ribonucleic acid sequencing (RNA-seq) analysis, which was significantly downregulated upon Oct4 overexpression. Chromatin immunoprecipitation assays revealed the binding of Oct4 to the promoter region of Rnd1 by ectopic overexpression of Oct4. Dual luciferase assays indicated that Oct4 overexpression suppressed transcriptional activity of the Rnd1 promoter. Moreover, overexpression of Rnd1 partially rescued the inhibitory effects of Oct4 on the migration and invasion of breast cancer cells. Overexpression of Rnd1 counteracted the influence of Oct4 on the formation of cell adhesion and lamellipodia, which implied a potential underlying mechanism involving Rnd1. In addition, we also found that overexpression of Oct4 led to an elevation of E-cadherin expression, even in 4T1 cells that possess a relatively high basal level of E-cadherin. Rnd1 overexpression impaired the promoting effects of Oct4 on E-cadherin expression in MDA-MB-231 cells. These results suggest that Oct4 affects the metastatic potential of breast cancer cells through Rnd1-mediated effects that influence cell motility and E-cadherin expression.

On the origin and evolutionary history of NANOG

Though pluripotency is well characterized in mammals, many questions remain to be resolved regarding its evolutionary history. A necessary prerequisite for addressing this issue is to determine the phylogenetic distributions and orthology relationships of the transcription factor families sustaining or modulating this property. In mammals, the NANOG homeodomain transcription factor is one of the core players in the pluripotency network. However, its evolutionary history has not been thoroughly studied, hindering the interpretation of comparative studies. To date, the NANOG family was thought to be monogenic, with numerous pseudogenes described in mammals, including a tandem duplicate in Hominidae. By examining a wide-array of craniate genomes, we provide evidence that the NANOG family arose at the latest in the most recent common ancestor of osteichthyans and that NANOG genes are frequently found as tandem duplicates in sarcopterygians and as a single gene in actinopterygians. Their phylogenetic distribution is thus reminiscent of that recently shown for Class V POU paralogues, another key family of pluripotency-controlling factors. However, while a single ancestral duplication has been reported for the Class V POU family, we suggest that multiple independent duplication events took place during evolution of the NANOG family. These multiple duplications could have contributed to create a layer of complexity in the control of cell competence and pluripotency, which could explain the discrepancies relative to the functional evolution of this important gene family. Further, our analysis does not support the hypothesis that loss of NANOG and emergence of the preformation mode of primordial germ cell specification are causally linked. Our study therefore argues for the need of further functional comparisons between NANOG paralogues, notably regarding the novel duplicates identified in sauropsids and non-eutherian mammals.

Induction of dental epithelial cell differentiation marker gene expression in non-odontogenic human keratinocytes by transfection with thymosin beta 4

Previous studies have shown that the recombination of cells liberated from developing tooth germs develop into teeth. However, it is difficult to use human developing tooth germ as a source of cells because of ethical issues. Previous studies have reported that thymosin beta 4 (Tmsb4x) is closely related to the initiation and development of the tooth germ. We herein attempted to establish odontogenic epithelial cells from non-odontogenic HaCaT cells by transfection with TMSB4X. TMSB4X-transfected cells formed nodules that were positive for Alizarin-red S (ALZ) and von Kossa staining (calcium phosphate deposits) when cultured in calcification-inducing medium. Three selected clones showing larger amounts of calcium deposits than the other clones, expressed PITX2, Cytokeratin 14, and Sonic Hedgehog. The upregulation of odontogenesis-related genes, such as runt-related transcription factor 2 (RUNX2), Amelogenin (AMELX), Ameloblastin (AMBN) and Enamelin (ENAM) was also detected. These proteins were immunohistochemically observed in nodules positive for the ALZ and von Kossa staining. RUNX2-positive selected TMSB4X-transfected cells implanted into the dorsal subcutaneous tissue of nude mice formed matrix deposits. Immunohistochemically, AMELX, AMBN and ENAM were observed in the matrix deposits. This study demonstrated the possibility of induction of dental epithelial cell differentiation marker gene expression in non-odontogenic HaCaT cells by TMSB4X.