Valproic acid enhances Oct4 promoter activity through PI3K/Akt/mTOR pathway activated nuclear receptors

The cooperation of cis-elements during M-cadherin promoter activation

M-cadherin is a skeletal muscle-specific transmembrane protein mediating the cell-cell adhesion of myoblasts during myogenesis. It is expressed in the proliferating satellite cells and highly induced by myogenic regulatory factors (MRFs) during terminal myogenic differentiation. Several conserved cis-elements, including 5 E-boxes, 2 GC boxes, and 1 conserved downstream element (CDE) were identified in the M-cadherin proximal promoter. We found that E-box-3 and -4 close to the transcription initiation site (TIS) mediated most of its transactivation by MyoD, the strongest myogenic MRF. Including of any one of the other E-boxes restored the full activation by MyoD, suggesting an essential collaboration between E-boxes. Stronger activation of M-cadherin promoter than that of muscle creatine kinase (MCK) by MyoD was observed regardless of culture conditions and the presence of E47. Furthermore, MyoD/E47 heterodimer and MyoD ∼ E47 fusion protein achieved similar levels of activation in differentiation medium (DM), suggesting high affinity of MyoD/E47 to E-boxes 3/4 under DM. We also found that GC boxes and CDE positively affected MyoD mediated activation. The CDE element was predicted to be the target of the chromatin-modifying factor Meis1/Pbx1 heterodimer. Knockdown of Pbx1 significantly reduced the expression level of M-cadherin, but increased that of N-cadherin. Using ChIP assay, we further found significant reduction in MyoD recruitment to M-cadherin promoter when CDE was deleted. Taken together, these observations suggest that the chromatin-modifying function of Pbx1/Meis1 is critical to M-cadherin promoter activation before MyoD is recruited to E-boxes to trigger transcription.

Valproic Acid Enhances Reprogramming Efficiency and Neuronal Differentiation on Small Molecules Staged-Induction Neural Stem Cells: Suggested Role of mTOR Signaling

Inducing somatic cells into neural stem cells (iNSCs) in specific ways provides a new cell therapy in a variety of neurological diseases. In the past, iNSCs were generated by transcription factors which increased the risk of mutagenesis, tumor formations, and immune reactions by viral transduction vectors. Therefore, in this study, different small molecules were used to induce mouse embryonic fibroblasts (MEFs) into iNSCs in different reprogramming stages, which showed high reprogramming efficiency without altering the genome. We demonstrated that the small molecules staged-induction neural stem cells (SMSINS) have the characteristics of neural stem cells (NSCs) in morphology, gene expression, self-renewal and differentiation potential. Furthermore, valproic acid (VPA), one of small molecules, was showed to enhance neural induction with highest efficiency compared with six other small molecules, which were also investigated in the present study. Moreover, our results suggested that activating the mammalian target of rapamycin (mTOR) signaling enhanced the induction efficiency and neuronal differentiation. Collectively, our findings indicated that using this induction program allowed us to obtain safe and efficient iNSCs which were free of genetic manipulation. The VPA-mediated mTOR signaling pathway may enhance reprogramming efficiency and neuronal differentiation. So we suggested that this program could be a new method of obtaining iNSCs for the treatment of neurological diseases by cell replacement therapy in the future.

Neurons Derived from Induced Pluripotent Stem Cells of Patients with Down Syndrome Reproduce Early Stages of Alzheimer's Disease Type Pathology in vitro

People with Down syndrome (DS) are at high risk of developing pathology similar to Alzheimer's disease (AD). Modeling of this pathology in vitro may be useful for studying this phenomenon. In this study, we analyzed three different cultures of neural cells carrying trisomy of chromosome 21, which were generated by directed differentiation from induced pluripotent stem cells (iPS cells). We report here that in vitro generated DS neural cells have abnormal metabolism of amyloid-β (Aβ) manifested by increased secretion and accumulation of Aβ granules of Aβ42 pathological isoform with upregulated expression of the APP gene. Additionally, we found increased expression levels of genes that are considered to be associated with AD (BACE2, RCAN1, ETS2, TMED10), as compared to healthy controls. Thus, the neural cells generated from induced pluripotent stem cells with DS reproduce initial cellular signs of AD-type pathology and can be useful tools for modeling and studying this variant of AD in vitro.

PI3K/AKT/mTOR Signaling Mediates Valproic Acid-Induced Neuronal Differentiation of Neural Stem Cells through Epigenetic Modifications

Although valproic acid (VPA), has been shown to induce neuronal differentiation of neural stem cells (NSCs), the underlying mechanisms remain poorly understood. Here we investigated if and how mammalian target of rapamycin (mTOR) signaling is involved in the neuronal differentiation of VPA-induced NSCs. Our data demonstrated that mTOR activation not only promoted but also was necessary for the neuronal differentiation of NSCs induced by VPA. We further found that inhibition of mTOR signaling blocked demethylation of neuron-specific gene neurogenin 1 (Ngn1) regulatory element in induced cells. These are correlated with the significant alterations of passive DNA demethylation and the active DNA demethylation pathway in the Ngn1 promoter, but not the suppression of lysine-specific histone methylation and acetylation in the promoter region of Ngn1. These findings highlight a potentially important role for mTOR signaling, by working together with DNA demethylation, to influence the fate of NSCs via regulating the expression of Ngn1 in VPA-induced neuronal differentiation of NSCs.

Correlation of Cancer Stem-Cell Markers OCT4, SOX2, and NANOG with Clinicopathological Features and Prognosis in Operative Patients with Rectal Cancer

PURPOSE

To investigate the association of cancer stem-cell markers [octamer-binding transcription factor 4 (OCT4), sex determining region Y-box 2 (SOX2), and Nanog homebox (NANOG)] expression with clinicopathological properties and overall survival (OS) in operative rectal cancer (RC) patients receiving adjuvant therapy.

MATERIALS AND METHODS

153 patients with primary RC receiving surgery were enrolled. Tumor tissue and paired adjacent normal tissue sample were collected, and OCT4, SOX2, and NANOG expressions were assessed by immunofluorescent staining. The median follow-up duration was 5.2 years, and the last follow-up date was August 2016.

RESULTS

Tumor tissue OCT4 (p<0.001), SOX2 (p=0.003), and NANOG (p<0.001) expressions were higher than those in adjacent tissue. OCT4 expression was positively correlated with pathological grade (R=0.185, p=0.022), tumor size (R=0.224, p=0.005), and N stage (R=0.170, p=0.036). NANOG expression was positively associated with tumor size (R=0.169, p=0.036). Kaplan-Meier suggested that OCT4⁺ was associated with worse OS compared with OCT4? (p<0.001), while no association of SOX2 (p=0.121) and NANOG expressions (p=0.195) with OS was uncovered. Compared with one or no positive marker, at least two positive markers were associated with shorter OS (p<0.001), while all three positive markers were correlated with worse OS compared with two or less positive markers (p<0.001). Multivariate Cox's analysis revealed that OCT4⁺ (p<0.001) and N stage (p=0.046) were independent factors for shorter OS.

CONCLUSION

Tumor tissue OCT4 expression was correlated with poor differentiation, tumor size, and N stage, and it can serve as an independent prognostic biomarker in operative patients with RC receiving adjuvant therapy.

Cellular reprogramming for clinical cartilage repair

The repair of articular cartilage needs a sufficient number of chondrocytes to replace the defect tissue, and therefore, expansion of cells is generally required. Chondrocytes derived by cellular reprogramming may provide a solution to the limitations of current (stem) cell-based therapies. In this article, two distinct approaches-induced pluripotent stem cell (iPSC)-mediated reprogramming and direct lineage conversion-are analysed and compared according to criteria that encompass the qualification of the method and the derived chondrocytes for the purpose of clinical application. Progress in iPSC generation has provided insights into the replacement of reprogramming factors by small molecules and chemical compounds. As follows, multistage chondrogenic differentiation methods have shown to improve the chondrocyte yield and quality. Nevertheless, the iPSC 'detour' remains a time- and cost-consuming approach. Direct conversion of fibroblasts into chondrocytes provides a slight advantage over these aspects compared to the iPSC detour. However, the requirement of constitutive transgene expression to inhibit hypertrophic differentiation limits this approach of being translated to the clinic. It can be concluded that the quality of the derived chondrocytes highly depends on the characteristics of the reprogramming method and that this is important to keep in mind during the experimental set-up. Further research into both reprogramming approaches for clinical cartilage repair has to include proper control groups and epigenetic profiling to optimize the techniques and eventually derive functionally stable articular chondrocytes.

Transcriptional factor OCT4 promotes esophageal cancer metastasis by inducing epithelial-mesenchymal transition through VEGF-C/VEGFR-3 signaling pathway

The octamer-binding transcription factor 4 (OCT4) can promote cancer proliferation and metastasis. Esophageal carcinoma (ECC) harbors different quantities of OCT4-positive cancer cells. These cells are highly malignant and prone to metastasis; however, the mechanism remains unknown. In this study, we found that OCT4 enhances vascular endothelial growth factor C (VEGF-C) promoter activity to promote VEGF-C expression and activates VEGF receptor 3 (VEGFR-3) in ECC cells, thereby inducing cancer cell epithelial-mesenchymal transition (EMT). Studies using xenograft models showed that OCT4 promoted xenograft growth and intraperitoneal implantation metastasis of ECC cells. Downregulation of OCT4 expression could inhibit cancer metastasis. OCT4- and VEGF-C-positive ECC presented more malignant biological behaviors and the corresponding patients exhibited a poor prognosis. The study confirmed that the OCT4/VEGF-C/VEGFR-3/EMT signaling plays a role in the progression of ECC. Understanding of how OCT4 regulates EMT and how ECC metastasis occurs will provide useful targets for the biological treatment of ECC.

Dual inhibiting OCT4 and AKT potently suppresses the propagation of human cancer cells

AKT serves as an epigenetic modulator that links epigenetic regulation to cell survival and proliferation while the epigenetic mediator OCT4 critically controls stem cell pluripotency and self-renewal. Emerging evidence indicated their complicated interplays in cancer cells and cancer stem cells (CSCs), and inhibiting either one may activate the other. Thus, in this study, we propose a strategy to targeting both factors simultaneously. Firstly, a combination of an OCT4-specific shRNA and the specific AKT inhibitor Akti-1/2 potently suppressed the propagation of human embryonal carcinoma cells, adherent cancer cells and stem-like cancer cells, establishing the proof-of-concept that dual inhibiting OCT4 and AKT can effectively target various cancer cells. Next, we combined Akti-1/2 with metformin, a widely-prescribed drug for treating type 2 diabetes, which was reported to down-regulate OCT4 expression. The metformin + Akti-1/2 combo significantly altered multiple signaling and epigenetic pathways, induced growth arrest and cell death of adherent and stem-like glioblastoma U87 cells, and attenuated their tumorigenicity in vivo. Taken together, we demonstrate here that simultaneously targeting an epigenetic mediator and an epigenetic modulator, by dual inhibiting OCT4 and AKT, can have significantly improved efficacies over single treatment in suppressing the propagation of CSCs as well as the entire bulk of differentiated cancer cells.

alproic Acid Modulates the Multipotency in Periodontal Ligament Stem Cells via p53-Mediated Cell Cycle

Human periodontal ligament stem cells (PDLSCs), a type of mesenchymal stem cell, are a promising source for dental regeneration and are identified in human periodontal ligaments from extracted third molars. Valproic acid (VPA) is a histone deacetylase inhibitor that has been used as a wide-spectrum antiepileptic drug and a medication for mood disorders. VPA has shown several effects on increasing the pluripotency of embryonic stem cells and controlling osteogenic differentiation, besides the prevention of seizures. However, its effect on proliferation and osteogenesis depends on the cell type and concentration. The aim of this study was to investigate the effects of cyclic and constant VPA treatment on PDLSCs. Proliferation and apoptosis of PDLSCs were determined with cyclic and constant VPA treatment. In cemento/osteogenic differentiation, osteogenic markers decreased significantly after cyclic treatment with 0.5 mM VPA. In contrast, VPA enhanced osteogenic differentiation after constant treatment. With cyclic VPA treatment, p53 levels related to apoptotic pathway decreased to induce proliferation. These findings indicated that VPA has different roles in proliferation and differentiation of PDLSCs in vitro and in vivo via p53-related pathway.

Human Amniocytes Are Receptive to Chemically Induced Reprogramming to Pluripotency

Restoring pluripotency using chemical compounds alone would be a major step forward in developing clinical-grade pluripotent stem cells, but this has not yet been reported in human cells. We previously demonstrated that VPA_AFS cells, human amniocytes cultivated with valproic acid (VPA) acquired functional pluripotency while remaining distinct from human embryonic stem cells (hESCs), questioning the relationship between the modulation of cell fate and molecular regulation of the pluripotency network. Here, we used single-cell analysis and functional assays to reveal that VPA treatment resulted in a homogeneous population of self-renewing non-transformed cells that fulfill the hallmarks of pluripotency, i.e., a short G1 phase, a dependence on glycolytic metabolism, expression of epigenetic modifications on histones 3 and 4, and reactivation of endogenous OCT4 and downstream targets at a lower level than that observed in hESCs. Mechanistic insights into the process of VPA-induced reprogramming revealed that it was dependent on OCT4 promoter activation, which was achieved independently of the PI3K (phosphatidylinositol 3-kinase)/AKT/mTOR (mammalian target of rapamycin) pathway or GSK3β inhibition but was concomitant with the presence of acetylated histones H3K9 and H3K56, which promote pluripotency. Our data identify, for the first time, the pluripotent transcriptional and molecular signature and metabolic status of human chemically induced pluripotent stem cells.

Valproic acid attenuates skeletal muscle wasting by inhibiting C/EBPβ-regulated atrogin1 expression in cancer cachexia

Muscle wasting is the hallmark of cancer cachexia and is associated with poor quality of life and increased mortality. Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, has important biological effects in the treatment of muscular dystrophy. To verify whether VPA could ameliorate muscle wasting induced by cancer cachexia, we explored the role of VPA in two cancer cachectic mouse models [induced by colon-26 (C26) adenocarcinoma or Lewis lung carcinoma (LLC)] and atrophied C2C12 myotubes [induced by C26 cell conditioned medium (CCM) or LLC cell conditioned medium (LCM)]. Our data demonstrated that treatment with VPA increased the mass and cross-sectional area of skeletal muscles in tumor-bearing mice. Furthermore, treatment with VPA also increased the diameter of myotubes cultured in conditioned medium. The skeletal muscles in cachectic mice or atrophied myotubes treated with VPA exhibited reduced levels of CCAAT/enhancer binding protein beta (C/EBPβ), resulting in atrogin1 downregulation and the eventual alleviation of muscle wasting and myotube atrophy. Moreover, atrogin1 promoter activity in myotubes was stimulated by CCM via activating the C/EBPβ-responsive cis-element and subsequently inhibited by VPA. In contrast to the effect of VPA on the levels of C/EBPβ, the levels of inactivating forkhead box O3 (FoxO3a) were unaffected. In summary, VPA attenuated muscle wasting and myotube atrophy and reduced C/EBPβ binding to atrogin1 promoter locus in the myotubes. Our discoveries indicate that HDAC inhibition by VPA might be a promising new approach for the preservation of skeletal muscle in cancer cachexia.

Valproic acid promotes radiosensitization in meningioma stem-like cells

Although meningioma stem-like cells have been isolated and characterized, their therapeutic targeting remains a challenge. Meningioma sphere cells (MgSCs) with cancer stem cells properties show chemo- and radioresistance in comparison with meningioma adherent cells (MgACs). We tested the effect of valproic acid (VPA), a commonly used anti-epileptic drug, which passes the blood brain barrier, on cultured MgSCs. VPA reduced the viability of MgSCs and MgACs. In MgSCs, treatment with VPA increased radio-sensitivity, expression of p-cdc2, p-H2AX and cleaved caspase-3 and PARP. Anchorage-independent growth (AIG) was reduced by VPA. AIG was further reduced by combined treatment with irradiation. Expression of a stem cell marker, Oct4, was reduced by VPA. Oct4 was further decreased by combined treatment with irradiation. These results suggest that VPA may be a potential treatment for meningioma through targeting meningioma stem-like cells.

Induced pluripotent stem (iPS) cells from human fetal stem cells

Pluripotency defines the ability of stem cells to differentiate into all the lineages of the three germ layers and self-renew indefinitely. Somatic cells can regain the developmental potential of embryonic stem cells following ectopic expression of a set of transcription factors or, in certain circumstances, via modulation of culture conditions and supplementation with small molecule, that is, induced pluripotent stem (iPS) cells. Here, we discuss the use of fetal tissues for reprogramming, focusing in particular on stem cells derived from human amniotic fluid, and the development of chemical reprogramming. We next address the advantages and disadvantages of deriving pluripotent cells from fetal tissues and the potential clinical applications.

Role of epigenetic reprogramming in hematopoietic stem cell function

PURPOSE OF REVIEW

Epigenetic regulatory networks determine the fate of dividing hematopoietic stem cells (HSCs). Prior attempts at the ex-vivo expansion of transplantable human HSCs have led to the depletion or at best maintenance of the numbers of HSCs because of the epigenetic events that silence the HSC gene-expression pattern. The purpose of this review is to outline the recent efforts to use small molecules to reprogram cultured CD34 cells so as to expand their numbers.

RECENT FINDINGS

Chromatin-modifying agents (CMAs) reactivate the gene-expression patterns of HSCs that have been silenced as they divide ex vivo. Increasing evidence indicates that CMAs act not only by promoting HSC symmetrical self-renewal divisions, but also by reprogramming progenitor cells, resulting in greater numbers of HSCs. The use of such CMAs for these purposes has not resulted in malignant transformation of the ex-vivo treated cell product.

SUMMARY

The silencing of the gene-expression program that determines HSC function after ex-vivo culture can be reversed by reprogramming the progeny of dividing HSCs with transient exposure to CMAs. The successful implementation of this approach provides a strategy which might lead to the development of a clinically relevant means of manufacturing increased numbers of HSCs.

Epigenetic modulation of dental pulp stem cells: implications for regenerative endodontics

Dental pulp stem cells (DPSCs) offer significant potential for use in regenerative endodontics, and therefore, identifying cellular regulators that control stem cell fate is critical to devising novel treatment strategies. Stem cell lineage commitment and differentiation are regulated by an intricate range of host and environmental factors of which epigenetic influence is considered vital. Epigenetic modification of DNA and DNA-associated histone proteins has been demonstrated to control cell phenotype and regulate the renewal and pluripotency of stem cell populations. The activities of the nuclear enzymes, histone deacetylases, are increasingly being recognized as potential targets for pharmacologically inducing stem cell differentiation and dedifferentiation. Depending on cell maturity and niche in vitro, low concentration histone deacetylase inhibitor (HDACi) application can promote dedifferentiation of several post-natal and mouse embryonic stem cell populations and conversely increase differentiation and accelerate mineralization in DPSC populations, whilst animal studies have shown an HDACi-induced increase in stem cell marker expression during organ regeneration. Notably, both HDAC and DNA methyltransferase inhibitors have also been demonstrated to dramatically increase the reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) for use in regenerative therapeutic procedures. As the regulation of cell fate will likely remain the subject of intense future research activity, this review aims to describe the current knowledge relating to stem cell epigenetic modification, focusing on the role of HDACi on alteration of DPSC phenotype, whilst presenting the potential for therapeutic application as part of regenerative endodontic regimens.

Wnt3a signal pathways activate MyoD expression by targeting cis-elements inside and outside its distal enhancer

Wnt proteins are secreted cytokines and several Wnts are expressed in the developing somites and surrounding tissues. Without proper Wnt stimulation, the organization of the dermomyotome and myotome can become defective. These Wnt signals received by somitic cells can lead to activation of Pax3/Pax7 and myogenic regulatory factors (MRFs), especially Myf5 and MyoD. However, it is currently unknown whether Wnts activate Myf5 and MyoD through direct targeting of their cis-regulatory elements or via indirect pathways. To clarify this issue, in the present study, we tested the regulation of MyoD cis-regulatory elements by Wnt3a secreted from human embryonic kidney (HEK)-293T cells. We found that Wnt3a activated the MyoD proximal 6.0k promoter (P6P) only marginally, but highly enhanced the activity of the composite P6P plus distal enhancer (DE) reporter through canonical and non-canonical pathways. Further screening of the intervening fragments between the DE and the P6P identified a strong Wnt-response element (WRE) in the upstream −8 to −9k region (L fragment) that acted independently of the DE, but was dependent on the P6P. Deletion of a Pax3/Pax7-targeted site in the L fragment significantly reduced its response to Wnt3a, implying that Wnt3a activates the L fragment partially through Pax3/Pax7 action. Binding of β-catenin and Pax7 to their target sites in the DE and the L fragment respectively was also demonstrated by ChIP. These observations demonstrated the first time that Wnt3a can directly activate MyoD expression through targeting cis-elements in the DE and the L fragment.

We found that Wnt3a can directly activate MyoD expression through targeting cis-elements in the distal enhancer and in the upstream −8 to −9k region. A novel Pax3/Pax7-involved pathway and both canonical and non-canonical Wnt pathways are involved in this activation.