Nanog induces hyperplasia without initiating tumors

Methionine adenosyltransferase2A inhibition restores metabolism to improve regenerative capacity and strength of aged skeletal muscle

We investigate the age-related metabolic changes that occur in aged and rejuvenated myoblasts using in vitro and in vivo models of aging. Metabolic and signaling experiments reveal that human senescent myoblasts and myoblasts from a mouse model of premature aging suffer from impaired glycolysis, insulin resistance, and generate Adenosine triphosphate by catabolizing methionine via a methionine adenosyl-transferase 2A-dependant mechanism, producing significant levels of ammonium that may further contribute to cellular senescence. Expression of the pluripotency factor NANOG downregulates methionine adenosyltransferase 2 A, decreases ammonium, restores insulin sensitivity, increases glucose uptake, and enhances muscle regeneration post-injury. Similarly, selective inhibition of methionine adenosyltransferase 2 A activates Akt2 signaling, repairs pyruvate kinase, restores glycolysis, and enhances regeneration, which leads to significant enhancement of muscle strength in a mouse model of premature aging. Collectively, our investigation indicates that inhibiting methionine metabolism may restore age-associated impairments with significant gain in muscle function.

Ameliorating the hallmarks of cellular senescence in skeletal muscle myogenic progenitors in vitro and in vivo

Senescence of myogenic progenitors impedes skeletal muscle regeneration. Here, we show that overexpression of the transcription factor NANOG in senescent myoblasts can overcome the effects of cellular senescence and confer a youthful phenotype to senescent cells. NANOG ameliorated primary hallmarks of cellular senescence including genomic instability, loss of proteostasis, and mitochondrial dysfunction. The rejuvenating effects of NANOG included restoration of DNA damage response via up-regulation of DNA repair proteins, recovery of heterochromatin marks via up-regulation of histones, and reactivation of autophagy and mitochondrial energetics via up-regulation of AMP-activated protein kinase (AMPK). Expression of NANOG in the skeletal muscle of a mouse model of premature aging restored the number of myogenic progenitors and induced formation of eMyHC+ myofibers. This work demonstrates the feasibility of reversing the effects of cellular senescence in vitro and in vivo, with no need for reprogramming to the pluripotent state.

3D chromatin architecture and epigenetic regulation in cancer stem cells

Dedifferentiation of cell identity to a progenitor-like or stem cell-like state with increased cellular plasticity is frequently observed in cancer formation. During this process, a subpopulation of cells in tumours acquires a stem cell-like state partially resembling to naturally occurring pluripotent stem cells that are temporarily present during early embryogenesis. Such characteristics allow these cancer stem cells (CSCs) to give rise to the whole tumour with its entire cellular heterogeneity and thereby support metastases formation while being resistant to current cancer therapeutics. Cancer development and progression are demarcated by transcriptional dysregulation. In this article, we explore the epigenetic mechanisms shaping gene expression during tumorigenesis and cancer stem cell formation, with an emphasis on 3D chromatin architecture. Comparing the pluripotent stem cell state and epigenetic reprogramming to dedifferentiation in cellular transformation provides intriguing insight to chromatin dynamics. We suggest that the 3D chromatin architecture could be used as a target for re-sensitizing cancer stem cells to therapeutics.

Epithelium-specific ETS transcription factor-1 regulates NANOG expression and inhibits NANOG-induced proliferation of human embryonic carcinoma cells

The epithelium-specific ETS transcription factor-1 (ESE-1) plays multiple roles in pathogenesis and normal development of epithelial tissues. NANOG, a key mediator of stem cell self-renewal and pluripotency, is also expressed in various cancers and pluripotent cells. In this study, we investigated how ESE-1 influences NANOG expression and NANOG-induced proliferation in human germ cell-derived embryonic carcinoma NCCIT cells. Endogenous ESE-1 expression in NCCIT cells significantly increased during differentiation, whereas NANOG expression decreased. In addition, NANOG expression was downregulated by exogenous overexpression of ESE-1, and increased by shRNA-mediated knockdown of ESE-1. NANOG transcriptional activity was reduced by dose-dependent ESE-1 overexpression and a putative ESE-1 binding site (EBS) was mapped within conserved region 2. Site-directed mutagenesis of the putative EBS abrogated the repressive effect of ESE-1 on NANOG promoter activity. ESE-1 directly interacted with the putative EBS to regulate transcriptional activity of NANOG. Furthermore, NANOG-induced proliferation and colony formation of NCCIT cells were inhibited by ESE-1 overexpression and stimulated by ESE-1 shRNA-mediated knockdown. Altogether, our results suggest that ESE-1 exerts an anti-proliferative effect on NCCIT cells by acting as a novel transcriptional repressor of NANOG.

Expression patterns and clinical significance of the potential cancer stem cell markers OCT4 and NANOG in colorectal cancer patients

Colorectal cancer (CRC) is one of the most important malignancies and causes of cancer-related deaths worldwide. Cancer stem cell markers identification could be helpful to acquire important prognostic information and develop new treatment regimens. This study aimed to evaluate the expression of OCT4 and NANOG in CRC patients and their clinical significance.

Totally 359 CRC samples were stained for OCT4 and NANOG expression using tissue microarray. The correlation between their expression and clinical and pathological features was explored.

The majority of CRC cases showed low-level expression of OCT4 (80%) and NANOG (75%). Lower expression of OCT4 was more often detected in CRC cases with no vascular involvement (P = .01). Also, a trend found between low level of OCT4 expression and absence of distant metastasis or lymph node involvement (P = .07 and P = .09, respectively). Surprisingly, a significant positive correlation was observed between NANOG expression and cellular differentiation (P = .05). Our combined analysis demonstrated that OCT4 ^low/NANOG ^low phenotype has frequently seen in colorectal cancer cases with no vascular invasion (P = .05).

Our observations indicated that higher expression of OCT4 and NANOG can confer malignant and aggressive behavior to CRC. Evaluation of the co-expression of these cancer stem cell markers can serve a new diagnostic and prognostic approach in CRC patients. These findings also suggested that simultaneous expression of OCT4 and NANOG can be considered as a therapeutic marker for targeted therapy of CRC, especially in advanced stages.

Low-Level Nanog Expression in the Regulation of Quiescent Endothelium

Supplemental Digital Content is available in the text.

Nanog is expressed in adult endothelial cells (ECs) at a low-level, however, its functional significance is not known. The goal of our study was to elucidate the role of Nanog in adult ECs using a genetically engineered mouse model system.

Impact of modulation of telomerase and cancer stem-cell marker OCT4 axis in cervical cancer pathogenesis with underlying HPV16 infection

Lacunae exist in the molecular event(s) specificity associated with cervical cancer (CaCx) pathogenesis. The present study aimed to evaluate the significance of telomerase-cervical cancer stem cells (CSCs) modulation in CaCx pathogenesis with underlying HPV16 infection. The study included HPV16 positive cases only (N = 65) of the total enrolled cases from Northeast India. The analysis of viral load and the differential messenger RNA expression of E6, E7, hTERT, hTR, and cancer stem-cell markers was studied by real-time polymerase chain reaction. Further the protein and colocalization study for E6, hTERT, and oct4 was performed by immunofluorescence. The real-time polymerase chain reaction based analysis showed an upregulation of HPV16 viral oncoprotein E6 and E7, and telomerase component hTERT and hTR expression and their correlation in CaCx susceptibility and severity. The hTERT expression correlated with viral load; while the E6 and telomerase protein expression colocalized in the nucleus. The CSCs marker octamer-binding transcription factor 4 (OCT4) was significantly upregulated in CaCx cases, was associated with CaCx susceptibility and severity, and colocalized with E6 expression in the nucleus as revealed from the immunofluorescence studies. To conclude, the telomerase-OCT4 axis modulation holds key in HPV16 CaCx pathogenesis mediated by HPV16 E6 viral oncoprotein expression, and underlines its potential for therapeutic targeting.

The pluripotency network in colorectal cancer pathogenesis and prognosis: an update

Stemness characteristics are defining properties of cancer initiating cells and are associated with the ability to metastasize and survive in hostile environments. Establishment of the stem cell network depends on the action of a set of core transcription factors that work in concert with other ancillary proteins that are also important during embryonic development. New data consolidate the role of core pluripotency transcription factors OCT4, SOX2 and NANOG as adverse prognostic factors in colorectal cancer. mRNA-binding proteins LIN28 and Musashi, that are associated with stemness, and epigenetic modifiers such as de-acetylase SIRT1 may also have prognostic value in colorectal cancer. This paper provides an update of the stem cell factors in the pathogenesis and prognosis of colorectal cancer.

Chimeric NANOG repressors inhibit glioblastoma growth in vivo in a context-dependent manner

Targeting stemness promises new therapeutic strategies against highly invasive tumors. While a number of approaches are being tested, inhibiting the core transcription regulatory network of cancer stem cells is an attractive yet challenging possibility. Here we have aimed to provide the proof of principle for a strategy, previously used in developmental studies, to directly repress the targets of a salient stemness and pluripotency factor: NANOG. In doing so we expected to inhibit the expression of so far unknown mediators of pro-tumorigenic NANOG function. We chose NANOG since previous work showed the essential requirement for NANOG activity for human glioblastoma (GBM) growth in orthotopic xenografts, and it is apparently absent from many adult human tissues thus likely minimizing unwanted effects on normal cells. NANOG repressor chimeras, which we name NANEPs, bear the DNA-binding specificity of NANOG through its homeodomain (HD), and this is linked to transposable human repressor domains. We show that in vitro and in vivo, NANEP5, our most active NANEP with a HES1 repressor domain, mimics knock-down (kd) of NANOG function in GBM cells. Competition orthotopic xenografts also reveal the effectiveness of NANEP5 in a brain tumor context, as well as the specificity of NANEP activity through the abrogation of its function via the introduction of specific mutations in the HD. The transcriptomes of cells expressing NANEP5 reveal multiple potential mediators of pro-tumorigenic NANEP/NANOG action including intercellular signaling components. The present results encourage further studies on the regulation of context-dependent NANEP abundance and function, and the development of NANEP-based anti-cancer therapies.

Efficient and high yield isolation of myoblasts from skeletal muscle

Skeletal muscle (SkM) regeneration relies on the activity of myogenic progenitors that reside beneath the basal lamina of myofibers. Here, we describe a protocol for the isolation of the SkM progenitors from young and old mice by exploiting their outgrowth potential from SkM explants on matrigel coated dishes in the presence of high serum, chicken embryo extract and basic fibroblast growth factor. Compared to other protocols, this method yields a higher number of myoblasts (10-20 million) by enabling the outgrowth of these cells from tissue fragments. The majority of outgrowth cells (~90%) were positive for myogenic markers such as α7-integrin, MyoD, and Desmin. The myogenic cell population could be purified to 98% with one round of pre-plating on collagen coated dishes, where differential attachment of fibroblasts and other non-myogenic progenitors separates them from myoblasts. Moreover, the combination of high serum medium and matrigel coating provided a proliferation advantage to myogenic cells, which expanded rapidly (~24 h population doubling), while non-myogenic cells diminished over time, thereby eliminating the need for further purification steps such as FACS sorting. Finally, myogenic progenitors gave rise to multinucleated myotubes that exhibited sarcomeres and spontaneous beating in the culture dish.

E‑cadherin regulates proliferation of colorectal cancer stem cells through NANOG

Cancer stem cells (CSCs) possess a self-renewal ability and display tumorigenic potential in immunodeficient mice. Colorectal CSCs are thought to be a uniform population and no functionally distinct subpopulations have been identified. Because E-cadherin is an essential molecule for self-renewal of embryonic stem cells, we examined E-cadherin expression, which may play a role in maintaining the properties of CSCs, in EpCAM^high/CD44⁺ colorectal CSCs from human primary colorectal cancers. We obtained 18 surgical specimens of human primary colorectal cancer. CD44, EpCAM, and E-cadherin expression were analyzed by fluorescence-activated cell sorting. Sorted EpCAM^high/CD44⁺ colorectal CSCs were injected into immunodeficient mice to estimate the tumorigenic potential. Genetic profiles were analyzed by cDNA microarray. Notably, colorectal CSCs could be divided into two populations based on the E-cadherin expression status, and they exhibited different pathological characteristics. Compared to E-cadherin-negative colorectal CSCs, E-cadherin-positive (EC⁺) colorectal CSCs demonstrated higher tumor growth potential in vivo. EC⁺ colorectal CSCs revealed a higher expression of the pluripotency factor NANOG, which contributed to the higher tumor growth potential of EC⁺ colorectal CSCs through control of cyclin D1 expression. These findings are the first demonstration of functionally distinct subpopulations of colorectal CSCs in human clinical samples.

Upregulation of embryonic stem cell marker Nanog in human gingival fibroblasts stimulated with cyclosporine A: An in vitro study

Background/purpose

Gingival overgrowth is a common side effect of medication with the immunosuppressant cyclosporine A (CsA). This study proposed to verify whether Nanog, an embryonic stem cell marker, contributes to gingival overgrowth stimulated with CsA in human gingival fibroblasts (HGFs).

Materials and methods

The effect of CsA on HGFs was used to elucidate whether Nanog expression could be induced by CsA using quantitative real-time reverse transcription-polymerase chain reaction and Western blotting. Cell growth in CsA-treated HGFs with Nanog lentivirus-mediated short hairpin RNA interference knockdown was evaluated by tetrazolium bromide reduction assay.

Results

CsA upregulated Nanog transcript in HGFs in a dose-dependent manner (P < 0.05). CsA was also shown to increase Nanog protein expression in HGFs in a dose-dependent manner (P < 0.05). In addition, downregulation of Nanog by lentiviral infection significantly inhibited CsA-stimulated cell growth in HGFs (P < 0.05).

Conclusion

CsA upregulated Nanog expression and cell growth in HGFs, while silencing Nanog effectively reversed these phenomena. Nanog may act as a major switch in the pathogenesis of CsA-induced gingival overgrowth.

Epigenetic modulators, modifiers and mediators in cancer aetiology and progression

This year is the tenth anniversary of the publication in this journal of a model suggesting the existence of 'tumour progenitor genes'. These genes are epigenetically disrupted at the earliest stages of malignancies, even before mutations, and thus cause altered differentiation throughout tumour evolution. The past decade of discovery in cancer epigenetics has revealed a number of similarities between cancer genes and stem cell reprogramming genes, widespread mutations in epigenetic regulators, and the part played by chromatin structure in cellular plasticity in both development and cancer. In the light of these discoveries, we suggest here a framework for cancer epigenetics involving three types of genes: 'epigenetic mediators', corresponding to the tumour progenitor genes suggested earlier; 'epigenetic modifiers' of the mediators, which are frequently mutated in cancer; and 'epigenetic modulators' upstream of the modifiers, which are responsive to changes in the cellular environment and often linked to the nuclear architecture. We suggest that this classification is helpful in framing new diagnostic and therapeutic approaches to cancer.

Dissecting the role of distinct OCT4-SOX2 heterodimer configurations in pluripotency

The transcription factors OCT4 and SOX2 are required for generating induced pluripotent stem cells (iPSCs) and for maintaining embryonic stem cells (ESCs). OCT4 and SOX2 associate and bind to DNA in different configurations depending on the arrangement of their individual DNA binding elements. Here we have investigated the role of the different OCT4-SOX2-DNA assemblies in regulating and inducing pluripotency. To this end, we have generated SOX2 mutants that interfere with specific OCT4-SOX2 heterodimer configurations and assessed their ability to generate iPSCs and to rescue ESC self-renewal. Our results demonstrate that the OCT4-SOX2 configuration that dimerizes on a Hoxb1-like composite, a canonical element with juxtaposed individual binding sites, plays a more critical role in the induction and maintenance of pluripotency than any other OCT4-SOX2 configuration. Overall, the results of this study provide new insight into the protein interactions required to establish a de novo pluripotent network and to maintain a true pluripotent cell fate.

The roles of NANOG in tumorigenesis

The pluripotency factor Nanog is highly expressed in pluripotent stem cells and certain adult stem cells, but is not expressed in normal adult cells. However, Nanog is frequently overexpressed in human cancers. Here, we discuss the distinct oncogenic roles of Nanog at various stages of tumorigenesis.

Concise Review: NANOG in Cancer Stem Cells and Tumor Development: An Update and Outstanding Questions

The homeobox domain transcription factor NANOG, a key regulator of embryonic development and cellular reprogramming, has been reported to be broadly expressed in human cancers. Functional studies have provided strong evidence that NANOG possesses protumorigenic attributes. In addition to promoting self-renewal and long-term proliferative potential of stem-like cancer cells, NANOG-mediated oncogenic reprogramming may underlie clinical manifestations of malignant disease. In this review, we examine the molecular origin, expression, biological activities, and mechanisms of action of NANOG in various malignancies. We also consider clinical implications such as correlations between NANOG expression and cancer prognosis and/or response to therapy. We surmise that NANOG potentiates the molecular circuitry of tumorigenesis, and thus may represent a novel therapeutic target or biomarker for the diagnosis, prognosis, and treatment outcome of cancer. Finally, we present critical pending questions relating NANOG to cancer stem cells and tumor development.