Mir-302 reprograms human skin cancer cells into a pluripotent ES-cell-like state

Interplay between the miRNome and the epigenetic machinery: Implications in health and disease

Epigenetics refers to functionally relevant genomic changes that do not involve changes in the basic nucleotide sequence. Majorly, these are of two types: DNA methylation and histone modifications. Small RNA molecules called miRNAs are often thought to mediate post-transcriptional epigenetic changes by mRNA degradation or translational attenuation. While DNA methylation and histone modifications have their own independent effects on various cellular events, several reports are suggestive of an obvious interplay between these phenomena and the miRNA regulatory program within the cell. Several miRNAs like miR-375, members of miR-29 family, miR-34, miR-200, and others are regulated by DNA methylation and histone modifications in various types of cancers and metabolic diseases. On the other hand, miRNAs like miR-449a, miR-148, miR-101, miR-214, and miR-128 target members of the epigenetic machinery and their dysregulation leads to diverse cellular aberrations. In spite of being independent cellular events, emergence of such reports that suggest a connection between DNA methylation, histone modification, and miRNA function in several diseases indicate that this connecting axis offers a valuable target with great therapeutic potential that might be exploited for disease management. We review the current status of crosstalk between the major epigenetic modifications and the miRNA machinery and discuss this in the context of health and disease.

Current status in cancer cell reprogramming and its clinical implications

PURPOSE

The technology of reprogramming a terminally differentiated cell to an embryonic-like state uncovered the possibility of reprogramming a malignant cell back to a more manageable stem cell-like state. Since the current cancer models suffer from reflecting heterogeneous tumour structure and limited to express the late-stage markers, the induced pluripotent stem cell (iPSC) technology could provide an alternative model to recapitulate the early stages of cancer. Generation of iPSCs from cancer cells could offer a tool for understanding the mechanisms of tumour initiation-progression in vitro, a platform for studying tumour heterogeneity and origin of cancer stem cells and a source for cancer type-specific drug discovery studies.

METHODS

In this review, we discussed the recent findings in reprogramming cancer cells with a special emphasis on similarities between cancer cells and pluripotent cells. We presented the basis of challenges in cancer cell reprogramming including the current problems in reprogramming, cancer-specific epigenetic state and chromosomal aberrations.

RESULTS

Cancer epigenetics represent the major hurdle before the prospective use of cancer iPSCs as a model system and for biomarker research. When the reprogramming process is optimised for cancer cell types, it might serve for two purposes: identification of the specific epigenetic state of cancer as well as reversion of the malignant phenotype to a potentially malignant but manageable state.

CONCLUSIONS

Reprogramming cancer cells would serve for our understanding of cancer-specific epigenome and elucidation of overlapping mechanisms shared by cancer-initiating cells and pluripotent cells.

MicroRNA-302d downregulates TGFBR2 expression and promotes hepatocellular carcinoma growth and invasion

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-associated mortality in China and the third leading cause worldwide. A number of microRNAs (miRNAs) have been implicated in cell cycle progression, growth, apoptosis, angiogenesis and metastasis in HCC. In the present study, reverse transcription-quantitative polymerase chain reaction analysis was used to detect the levels of miR-302d expression in the tissues of 30 patients with HCC. Cell cycle, growth, apoptosis and migration were analyzed using a cell counting kit, flow cytometry and a Transwell migration assay. Dual-luciferase reporter assays and western blotting were also used to analyze the expression levels of transforming growth factor beta type II receptor (TGFBR2) in HCC cells. The present study evaluated the role of miR-302d in the development and progression of HCC. Abnormally high expression of miR-302d was observed in 80% of HCC specimens. Moreover, patients with lower levels of miR-302d expression experienced a longer survival time than those with higher levels of miR-302d expression. It was demonstrated that miR-302d promoted HCC cell growth and migration, suppressed cell apoptosis and affected cell cycle distribution in vitro, and augmented tumorigenicity in vivo. Furthermore, TGFBR2, which is a tumor suppressor, was confirmed as a target of miR-302d in HCC cells. Dual-luciferase reporter assays indicated that TGFBR2 expression was negatively regulated by miR-302d. Taken together, the results of the present study suggest that miR-302d may serve as a valuable tool for predicting the prognosis of patients with HCC.

Induced pluripotent stem cell technology: a decade of progress

Since the advent of induced pluripotent stem cell (iPSC) technology a decade ago, enormous progress has been made in stem cell biology and regenerative medicine. Human iPSCs have been widely used for disease modelling, drug discovery and cell therapy development. Novel pathological mechanisms have been elucidated, new drugs originating from iPSC screens are in the pipeline and the first clinical trial using human iPSC-derived products has been initiated. In particular, the combination of human iPSC technology with recent developments in gene editing and 3D organoids makes iPSC-based platforms even more powerful in each area of their application, including precision medicine. In this Review, we discuss the progress in applications of iPSC technology that are particularly relevant to drug discovery and regenerative medicine, and consider the remaining challenges and the emerging opportunities in the field.

miR-302 Attenuates Amyloid-β-Induced Neurotoxicity through Activation of Akt Signaling

Deficiency of insulin signaling has been linked to diabetes and ageing-related neurodegenerative diseases such as Alzheimer's disease (AD). In this regard, brains exhibit defective insulin receptor substrate-1 (IRS-1) and hence result in alteration of insulin signaling in progression of AD, the most common cause of dementia. Consequently, dysregulation of insulin signaling plays an important role in amyloid-β (Aβ)-induced neurotoxicity. As the derivation of induced pluripotent stem cells (iPSC) involves cell reprogramming, it may provide a means for regaining the control of ageing-associated dysfunction and neurodegeneration via affecting insulin-related signaling. To this, we found that an embryonic stem cell (ESC)-specific microRNA, miR-302, silences phosphatase and tensin homolog (PTEN) to activate Akt signaling, which subsequently stimulates nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) elevation and hence inhibits Aβ-induced neurotoxicity. miR-302 is predominantly expressed in iPSCs and is known to regulate several important biological processes of anti-oxidative stress, anti-apoptosis, and anti-aging through activating Akt signaling. In addition, we also found that miR-302-mediated Akt signaling further stimulates Nanog expression to suppress Aβ-induced p-Ser307 IRS-1 expression and thus enhances tyrosine phosphorylation and p-Ser 473-Akt/p-Ser 9-GSK3β formation. Furthermore, our in vivo studies revealed that the mRNA expression levels of both Nanog and miR-302-encoding LARP7 genes were significantly reduced in AD patients' blood cells, providing a novel diagnosis marker for AD. Taken together, our findings demonstrated that miR-302 is able to inhibit Aβ-induced cytotoxicity via activating Akt signaling to upregulate Nrf2 and Nanog expressions, leading to a marked restoration of insulin signaling in AD neurons.

The expanding horizon of MicroRNAs in cellular reprogramming

Research over the last few years in cellular reprogramming has enlightened the magical potential of microRNAs (miRNAs) in changing the cell fate from somatic to pluripotent. Recent investigations on exploring the role(s) of miRNAs in somatic cell reprogramming revealed that they target a wide range of molecules and refine their protein output. This leads to fine tuning of distinct cellular processes including cell cycle, signalling pathways, transcriptional activation/silencing and epigenetic modelling. The concerted actions of miRNA on different pathways simultaneously strengthen the transition from a differentiated to de-differentiated state. Despite the well characterized transcriptional and epigenetic machinery underlying somatic cell reprogramming, the molecular circuitry for miRNA mediated cellular reprogramming is rather fragmented. This review summarizes recent findings addressing the role of miRNAs in inducing or suppressing reprogramming thus uncovering novel potentials of miRNAs as regulators of induced pluripotency maintenance, establishment and associated signalling pathways. Our bioinformatic analysis sheds light on various unexplored biological processes and pathways associated with reprogramming inducing miRNAs, thus helps in identifying roadblocks to full reprogramming. Specifically, the biological significance of highly conserved and most studied miRNA cluster, i.e. miR-302-367, in reprogramming is also highlighted. Further, roles of miRNAs in the differentiation of neurons from iPSCs are discussed. A recent approach of direct conversion or transdifferentiation of differentiated cells into neurons by miRNAs is also elaborated. This approach is now widely gaining impetus for the generation of neurological patient's brain cells directly from his/her somatic cells in an efficient and safe manner. Thus, decoding the intricate circuitry between miRNAs and other gene regulatory networks will not only uncover novel pathways in the direct reprogramming of somatic cells but will also open new avenues in stem cell biology.

Advances and Challenges on Cancer Cells Reprogramming Using Induced Pluripotent Stem Cells Technologies

Cancer cells transformation into a normal state or into a cancer cell population which is less tumorigenic than the initial one is a challenge that has been discussed during last decades and it is still far to be solved. Due to the highly heterogeneous nature of cancer cells, such transformation involves many genetic and epigenetic factors which are specific for each type of tumor. Different methods of cancer cells reprogramming have been established and can represent a possibility to obtain less tumorigenic or even normal cells. These methods are quite complex, thus a simple and efficient method of reprogramming is still required. As soon as induced pluripotent stem cells (iPSC) technology, which allowed to reprogram terminally differentiated cells into embryonic stem cells (ESC)-like, was developed, the method strongly attracted the attention of researches, opening new perspectives for stem cell (SC) personalized therapies and offering a powerful in vitro model for drug screening. This technology is also used to reprogram cancer cells, thus providing a modern platform to study cancer-related genes and the interaction between these genes and the cell environment before and after reprogramming, in order to elucidate the mechanisms of cancer initiation and progression. The present review summarizes recent advances on cancer cells reprogramming using iPSC technology and shows the progress achieved in such field.

Multimodal tumor suppression by miR-302 cluster in melanoma and colon cancer

The miR-302 family is one of the main groups of microRNAs, which are highly expressed in embryonic stem cells (ESCs). Previous reports have indicated that miR-302 can reduce the proliferation rate of some cancer cells while compromising on their oncogenic potential at the same time without having the same effect on normal somatic cells. In this study we aimed to further investigate the role of the miR-302 cluster in multiple cancer signaling pathways using A-375 melanoma and HT-29 colorectal cancer cells. Our results indicate that the miR-302 cluster has the potential to modulate oncogenic properties of cancer cells through inhibition of proliferation, angiogenesis and invasion, and through reversal of the epithelial-to-mesenchymal transition (EMT) in these cells. We showed for the first time that overexpression of miR-302 cluster sensitized A-375 and HT-29 cells to hypoxia and also to the selective BRAF inhibitor vemurafenib. MiR-302 is a pleiotropically acting miRNA family which may have significant implications in controlling cancer progression and invasion. It acts through a reprogramming process, which has a global effect on a multitude of cellular pathways and events. We propose that reprogramming of cancer cells by epigenetic factors, especially miRNAs might provide an efficient tool for controlling cancer and especially for those with more invasive nature.

In vitro models of cancer stem cells and clinical applications

Cancer cells, stem cells and cancer stem cells have for a long time played a significant role in the biomedical sciences. Though cancer therapy is more effective than it was a few years ago, the truth is that still none of the current non-surgical treatments can cure cancer effectively. The reason could be due to the subpopulation called “cancer stem cells” (CSCs), being defined as those cells within a tumour that have properties of stem cells: self-renewal and the ability for differentiation into multiple cell types that occur in tumours.

The phenomenon of CSCs is based on their resistance to many of the current cancer therapies, which results in tumour relapse. Although further investigation regarding CSCs is still needed, there is already evidence that these cells may play an important role in the prognosis of cancer, progression and therapeutic strategy. Therefore, long-term patient survival may depend on the elimination of CSCs. Consequently, isolation of pure CSC populations or reprogramming of cancer cells into CSCs, from cancer cell lines or primary tumours, would be a useful tool to gain an in-depth knowledge about heterogeneity and plasticity of CSC phenotypes and therefore carcinogenesis. Herein, we will discuss current CSC models, methods used to characterize CSCs, candidate markers, characteristic signalling pathways and clinical applications of CSCs. Some examples of CSC-specific treatments that are currently in early clinical phases will also be presented in this review.

MicroRNA-Mediated Reprogramming of Somatic Cells into Induced Pluripotent Stem Cells

MicroRNAs or miRNAs belong to a class of small noncoding RNAs that play a crucial role in posttranscriptional regulation of gene expression. Nascent miRNAs are expressed as a longer transcript, which are then processed into a smaller 18-23-nucleotide mature miRNAs that bind to the target transcripts and induce cleavage or inhibit translation. MiRNAs therefore represent another key regulator of gene expression in establishing and maintaining unique cellular fate. Several classes of miRNAs have been identified to be uniquely expressed in embryonic stem cells (ESC) and regulated by the core transcription factors Oct4, Sox2, and Klf4. One such class of miRNAs is the mir-302/367 cluster that is enriched in pluripotent cells in vivo and in vitro. Using the mir-302/367 either by themselves or in combination with the Yamanaka reprogramming factors (Oct4, Sox2, c-Myc, and Klf4) has resulted in the establishment of induced pluripotent stem cells (iPSC) with high efficiencies. In this chapter, we outline the methodologies for establishing and utilizing the miRNA-based tools for reprogramming somatic cells into iPSC.

A multiplexed miRNA and transgene expression platform for simultaneous repression and expression of protein coding sequences

Knockdown of single or multiple gene targets by RNA interference (RNAi) is necessary to overcome escape mutants or isoform redundancy. It is also necessary to use multiple RNAi reagents to knockdown multiple targets. It is also desirable to express a transgene or positive regulatory elements and inhibit a target gene in a coordinated fashion. This study reports a flexible multiplexed RNAi and transgene platform using endogenous intronic primary microRNAs (pri-miRNAs) as a scaffold located in the green fluorescent protein (GFP) as a model for any functional transgene. The multiplexed intronic miRNA - GFP transgene platform was designed to co-express multiple small RNAs within the polycistronic cluster from a Pol II promoter at more moderate levels to reduce potential vector toxicity. The native intronic miRNAs are co-transcribed with a precursor GFP mRNA as a single transcript and presumably cleaved out of the precursor-(pre) mRNA by the RNA splicing machinery, spliceosome. The spliced intron with miRNA hairpins will be further processed into mature miRNAs or small interfering RNAs (siRNAs) capable of triggering RNAi effects, while the ligated exons become a mature messenger RNA for the translation of the functional GFP protein. Data show that this approach led to robust RNAi-mediated silencing of multiple Renilla Luciferase (R-Luc)-tagged target genes and coordinated expression of functional GFP from a single transcript in transiently transfected HeLa cells. The results demonstrated that this design facilitates the coordinated expression of all mature miRNAs either as individual miRNAs or as multiple miRNAs and the associated protein. The data suggest that, it is possible to simultaneously deliver multiple negative (miRNA or shRNA) and positive (transgene) regulatory elements. Because many cellular processes require simultaneous repression and activation of downstream pathways, this approach offers a platform technology to achieve that dual manipulation efficiently. In conclusion, the current platform technology offers a miRNA/shRNA scaffold for the expression of combinations of native or synthetic intronic miRNAs as singletons or polycistrons for combinatorial multiplexed RNAi silencing or RNA-based gene therapy applications.

Isolation, Characterization, Cryopreservation of Human Amniotic Stem Cells and Differentiation to Osteogenic and Adipogenic Cells

Human stem cells and progenitor cells can be used to treat cancer and replace dysfunctional cells within a tissue or organ. The objective of this study was to identify the appropriate cells type in regenerative medicine and targeted therapy. As an alternative to embryonic and bone marrow stem cells, we examined human amniotic fluid stem cells (hAFSCs), one of the potential source of multipotent stem cells isolated from both cell pellet (using single-stage method), and supernatant of human amniotic fluid. Source of isolation and unique property of the cells emphasize that these cells are one of the promising new tools in therapeutic field. Double sources for isolation and availability of the left over samples in diagnostic laboratory at the same time have less legal and ethical concerns compared with embryonic stem cell studies. Cells were isolated, cultured for 18^th passage for 6 months and characterized using qPCR and flow cytometry. Cells showed good proliferative ability in culture condition. The cells successfully differentiated into the adipogenic and osteogenic lineages. Based on these findings, amniotic fluid can be considered as an appropriate and convenient source of human amniotic fluid stem cells. These cells provide potential tools for therapeutic applications in the field of regenerative medicine. To get a better understanding of crosstalk between Oct4/NANOG with osteogenesis and adipogenesis, we used network analysis based on Common Targets algorithm and Common Regulators algorithm as well as subnetwork discovery based on gene set enrichment. Network analysis highlighted the possible role of MIR 302A and MIR let-7g. We demonstrated the high expression of MIR 302A and low expression of MIR let7g in hAFSCs by qPCR.

Cellular Reprogramming Using Defined Factors and MicroRNAs

Development of human bodies, organs, and tissues contains numerous steps of cellular differentiation including an initial zygote, embryonic stem (ES) cells, three germ layers, and multiple expertized lineages of cells. Induced pluripotent stem (iPS) cells have been recently developed using defined reprogramming factors such as Nanog, Klf5, Oct3/4 (Pou5f1), Sox2, and Myc. This outstanding innovation is largely changing life science and medicine. Methods of direct reprogramming of cells into myocytes, neurons, chondrocytes, and osteoblasts have been further developed using modified combination of factors such as N-myc, L-myc, Sox9, and microRNAs in defined cell/tissue culture conditions. Mesenchymal stem cells (MSCs) and dental pulp stem cells (DPSCs) are also emerging multipotent stem cells with particular microRNA expression signatures. It was shown that miRNA-720 had a role in cellular reprogramming through targeting the pluripotency factor Nanog and induction of DNA methyltransferases (DNMTs). This review reports histories, topics, and idea of cellular reprogramming.

Novel glycylated sugar alcohols protect ESC-specific microRNAs from degradation in iPS cells

Excessive accumulation of embryonic stem cell (ESC)-specific microRNAs occurs in both ESCs and induced pluripotent stem cells (iPSC); yet, the mechanism involved is unknown. In iPSCs, we for the first time found that novel glycylated sugar alcohols, particularly glycylglycerins, are tightly bound with ESC-specific microRNA precursors (pre-miRNA), such as pre-miR-302. Among these isolated glycylglycerins, we further identified that 1,3-diglycylglycerin and 1,2,3-triglycylglycerin are two major compounds bonded with negatively charged nucleic acids via electro-affinity and subsequently forming sugar-like coats in the hairpin-like double helix structures of pre-miRNAs. As a result, such glycylglycerin-formed coating serves as a protection layer against miRNA degradation. Moreover, we found that the pH value of iPSC cytosol determines the charges of these glycylglycerins. During iPSC differentiation, the cytosol pH is increased and hence neutralizes the charges of glycylglycerins, consequently leading to fast miRNA degradation. Therefore, the current findings not only explain how ESC-specific miRNAs are preserved and accumulated in iPSCs and ESCs but also demonstrate an important function of glycylglycerins in protecting the structural integrity of highly degradable miRNAs, providing a useful means for maintaining miRNA/siRNA function as well as developing the related RNA interference (RNAi) applications.

MiR-134-Mbd3 axis regulates the induction of pluripotency

MicroRNAs (miRNAs) are post-transcriptional modulators of gene expression and play an important role in reprogramming process; however, relatively little is known about the underlying regulatory mechanism of miRNAs on how they epigenetically modulate reprogramming and pluripotency. Here, we report that the expression level of microRNA-134 (miR-134) was low in mouse embryonic stem cells (mESCs) but significantly up-regulated during neural differentiation, while down-regulated during the induction of induced pluripotent stem cells (iPSCs) from neural progenitor cells (NPCs). Inhibition of miR-134 by miR-134 sponge promoted the efficiency of reprogramming which also was highly similar to mESCs. On the contrary, up-regulation of miR-134 repressed iPSCs induction. We also found that inhibition of miR-134 promoted the maturation of pre-iPSCs and increased its pluripotency. We also showed that miR-134 can directly target to the pluripotency related factor Methyl-CpG-binding domain protein 3 (Mdb3) 3' untranslated regions (3' UTR) to down-regulate its expression. And Mbd3 was found to promote the induction of iPSCs and could block the repression of reprogramming caused by overexpression of miR-134. This work revealed the critical function of miR-134-Mbd3 axis on regulating reprogramming and pluripotency of iPSCs derived from the NPCs, and might provide an insight into the miR-134-Mbd3 axis on regulating the iPSCs quality for further clinical treatment.

Cryptotanshinone targets tumor-initiating cells through down-regulation of stemness genes expression

Recent evidence indicates that tumor-initiating cells (TICs), also called cancer stem cells (CSCs), are responsible for tumor initiation and progression, therefore representing an important cell population that may be used as a target for the development of future anticancer therapies. In the present study, Cryptotanshinone (CT), a traditional Chinese herbal medicine, was demonstrated to regulate the behaviors of LNCaP prostate cells and prostate LNCaP TICs. The results demonstrate that treatment with CT alters cellular proliferation, cell cycle status, migration, viability, colony formation and notably, sphere formation and down-regulation of stemness genes (Nanog, OCT4, SOX2, β-catenin, CXCR4) in TICs. The present study demonstrates that CT targets the LNCaP CD44+CD24- population that is representative of prostate TICs and also affects total LNCaP cells as well via down-regulation of stemness genes. The strong effect with which CT has on prostate TICs suggests that CT may potentially function as a novel natural anticancer agent that specifically targets TICs.

Reprogramming cancer cells: overview & current progress

INTRODUCTION

Cancer is a disease with genetic and epigenetic origins, and the possible effects of reprogramming cancer cells using the defined sets of transcription factors remain largely uninvestigated. In the handful of publications available so far, findings have shown that reprogramming cancer cells changed the characteristics of the cells to differ from the parental cancer cells. These findings indicated the possibility of utilizing reprogramming technology to create a disease model in the laboratory to be used in studying the molecular pathogenesis or for drug screening of a particular cancer model.

AREAS COVERED

Despite numerous methods employed in generating induced pluripotent stem cells (iPSCs) from cancer cells only a few studies have successfully reprogrammed malignant human cells. In this review we will provide an overview on i) methods to reprogram cancer cells, ii) characterization of the reprogrammed cancer cells, and iii) the differential effects of reprogramming on malignancy, epigenetics and response of the cancer cells to chemotherapeutic agents.

EXPERT OPINION

Continued technical progress in cancer cell reprogramming technology will be instrumental for more refined in vitro disease models and ultimately for the development of directed and personalized therapy for cancer patients in the future.

Matrix Hyaluronan Promotes Specific MicroRNA Upregulation Leading to Drug Resistance and Tumor Progression

Solid tumor invasion, metastasis and therapeutic drug resistance are the common causes for serious morbidity and cancer recurrence in patients. A number of research studies have searched for malignancy-related biomarkers and drug targets that are closely linked to tumor cell properties. One of the candidates is matrix hyaluronan (HA), which is known as one of the major extracellular matrix (ECM) components. HA serves as a physiological ligand for surface CD44 molecule and also functions as a bio-regulator. The binding of HA to CD44 has been shown to stimulate concomitant activation of a number of oncogenic pathways and abnormal cellular processes in cancer cells and cancer stem cells (CSCs). MicroRNAs (miRNAs) belong to a class of small RNAs containing ~20–25 nucleotides and are known to promote aberrant cellular functions in cancer cells. In this article, I have focused on the role of HA interaction with CD44 and several important signaling molecules in the regulation of unique miRNAs (e.g., miR-21, miR-302 and miR-10b) and their downstream targets leading to multiple tumor cell-specific functions (e.g., tumor cell growth, drug resistance and metastasis) and cancer progression. This new knowledge could provide the groundwork necessary for establishing new tumor markers and developing important, novel drugs targeted against HA/CD44-associated tumor progression, which can be utilized in the therapeutic treatment of metastatic cancer patients.

MicroRNA biogenesis and their functions in regulating stem cell potency and differentiation

Stem cells are unspecialized/undifferentiated cells that exist in embryos and adult tissues or can be converted from somatic differentiated cells. Use of stem cells for tissue regeneration and tissue engineering has been a cornerstone of the regenerative medicine. Stem cells are also believed to exist in cancer tissues, namely cancer stem cells (CSCs). Growing evidence suggests that CSCs are the culprit of cancer dormancy, progression and recurrence, and thus have recently received great attention. MicroRNAs (miRNAs) are a group of short, non-coding RNAs that regulate expression of a wide range of genes at a post-transcriptional manner. They are emerging as key regulators of stem cell behaviors. This mini review summarizes the basic biogenesis and mode of actions of miRNAs, recent progress and discoveries of miRNAs in cellular reprogramming, stem cell differentiation and cellular communication, as well as miRNAs in CSCs. Some potential of miRNAs in future biomedical applications and research pertaining to stem cells are briefly discussed.

Hsa-miR-520d converts fibroblasts into CD105+ populations

BACKGROUND

We have previously shown that hsa-miR-520d-5p can convert cancer cells into induced pluripotent stem cells (iPSCs) or mesenchymal stem cells (MSCs) via a dedifferentiation by a demethylation mechanism.

METHODS

We tested the effect of miR-520d-5p on human fibroblasts to determine whether it could be safely used in normal cells for future clinical therapeutic applications. After we transfected the microRNA into fibroblasts, we analyzed the phenotypic changes, gene expression levels, and stemness induction in vitro, and we evaluated tumor formation in an in vivo xenograft model.

RESULTS

The transfected fibroblasts turned into CD105+ cell populations, survived approximately 24 weeks, and exhibited increases in both the collagen-producing ability and in differentiation. Combinatorial transfection of small interfering RNAs for miR-520d-5p target genes (ELAVL2, GATAD2B, and TEAD1) produced similar results to miR-520d-5p transfection. These molecules converted normal cells into MSCs and not iPSCs.

CONCLUSIONS

In vitro data indicate the potent usefulness of this small molecule as a therapeutic biomaterial in normal cells and cancer cells because CD105+ cells never converted to iPSCs despite repeated transfections and all types of transfectants lost their tumorigenicity. This maintenance of a benign state following miR-520d-5p transfection appears to be caused by p53 upregulation. We conclude that miR-520d-5p may be a useful biomaterial at an in vitro level.

MiR-302a/b/c/d cooperatively sensitizes breast cancer cells to adriamycin via suppressing P-glycoprotein(P-gp) by targeting MAP/ERK kinase kinase 1 (MEKK1)

BACKGROUND

The importance of individual microRNAs (miRNAs) in tumor has been established in different cancers. However, their association with tumor chemoresistance has not been fully understood. Previously, we found two novel MDR-associated microRNAs (miRNAs). In this report, we investigated the combined effects of miRNA gene cluster in chemoresistance of breast cancer.

METHODS

This study was performed in two different breast cancer cell lines (MCF-7 and MCF-7/ADR). The levels of miRNAs and mRNA expression were determined by using Quantitative Real-Time PCR. Western blotting was used to detect the levels of protein molecules. Cell viability was assessed by MTS assay. Bioinformatics and Luciferase reporter assay was performed to examine miRNA binding to the 3'-UTR of target genes.

RESULTS

The miR-302S family including miR-302a, miR-302b, miR-302c, and miR-302d was significantly down-regulated in P-glycoprotein (P-gp)-overexpressing MCF-7/ADR cells. Overexpression of miR-302 increased intracellular accumulation of ADR and sensitized breast cancer cells to ADR. Most importantly, miR-302S produced stronger effects than each individual member alone. The four miRNAs cooperatively downregulate P-gp expression in regulating drug sensitivity. However, our results showed that the suppression of P-gp expression by miR-302 is not through typical miRNA-mediated mRNA degradation but at the level of protein and transcription. Further studies identified MAP/ERK kinase kinase 1 (MEKK1) as a direct and functional target of miR-302. miR-302 showed combinatorial effects on MKEE1 repression and MEKK1-mediated ERK pathway. The suppression of P-gp by miR-302 was reversed by MEKK1 overexpression.

CONCLUSION

Our results indicate that miR-302 cooperatively sensitizes breast cancer cells to adriamycin via suppressing P-glycoprotein by targeting MEKK1 of ERK pathway. miR-302 gene cluster may be a potential target for reversing P-gp-mediated chemoresistance in breast cancer.

miR-302 regulates pluripotency, teratoma formation and differentiation in stem cells via an AKT1/OCT4-dependent manner

Pluripotency makes human pluripotent stem cells (hPSCs) promising for regenerative medicine, but the teratoma formation has been considered to be a major obstacle for their clinical applications. Here, we determined that the downregulation of miR-302 suppresses the teratoma formation, hampers the self-renewal and pluripotency, and promotes hPSC differentiation. The underlying mechanism is that the high endogenous expression of miR-302 suppresses the AKT1 expression by directly targeting its 3'UTR and subsequently maintains the pluripotent factor OCT4 at high level. Our findings reveal that miR-302 regulates OCT4 by suppressing AKT1, which provides hPSCs two characteristics related to their potential for clinical applications: the benefit of pluripotency and the hindrance of teratoma formation. More importantly, we demonstrate that miR-302 upregulation cannot lead OCT4 negative human adult mesenchymal stem cells (hMSCs) to acquire the teratoma formation in vivo. Whether miR-302 upregulation can drive hMSCs to acquire a higher differentiation potential is worthy of deep investigation.

The Importance of Ubiquitination and Deubiquitination in Cellular Reprogramming

Ubiquitination of core stem cell transcription factors can directly affect stem cell maintenance and differentiation. Ubiquitination and deubiquitination must occur in a timely and well-coordinated manner to regulate the protein turnover of several stemness related proteins, resulting in optimal embryonic stem cell maintenance and differentiation. There are two switches: an E3 ubiquitin ligase enzyme that tags ubiquitin molecules to the target proteins for proteolysis and a second enzyme, the deubiquitinating enzyme (DUBs), that performs the opposite action, thereby preventing proteolysis. In order to maintain stemness and to allow for efficient differentiation, both ubiquitination and deubiquitination molecular switches must operate properly in a balanced manner. In this review, we have summarized the importance of the ubiquitination of core stem cell transcription factors, such as Oct3/4, c-Myc, Sox2, Klf4, Nanog, and LIN28, during cellular reprogramming. Furthermore, we emphasize the role of DUBs in regulating core stem cell transcriptional factors and their function in stem cell maintenance and differentiation. We also discuss the possibility of using DUBs, along with core transcription factors, to efficiently generate induced pluripotent stem cells. Our review provides a relatively new understanding regarding the importance of ubiquitination/deubiquitination of stem cell transcription factors for efficient cellular reprogramming.

Simultaneous Reprogramming and Gene Correction of Patient Fibroblasts

The derivation of genetically modified induced pluripotent stem (iPS) cells typically involves multiple steps, requiring lengthy cell culture periods, drug selection, and several clonal events. We report the generation of gene-targeted iPS cell lines following a single electroporation of patient-specific fibroblasts using episomal-based reprogramming vectors and the Cas9/CRISPR system. Simultaneous reprogramming and gene targeting was tested and achieved in two independent fibroblast lines with targeting efficiencies of up to 8% of the total iPS cell population. We have successfully targeted the DNMT3B and OCT4 genes with a fluorescent reporter and corrected the disease-causing mutation in both patient fibroblast lines: one derived from an adult with retinitis pigmentosa, the other from an infant with severe combined immunodeficiency. This procedure allows the generation of gene-targeted iPS cell lines with only a single clonal event in as little as 2 weeks and without the need for drug selection, thereby facilitating "seamless" single base-pair changes.

miR-302a/b/c/d cooperatively inhibit BCRP expression to increase drug sensitivity in breast cancer cells

OBJECTIVE

BCRP is overexpressed in many tumors and mediates multidrug resistance in breast cancer. In this study, we determined the involvement of miR-302S in the development of drug resistance in breast cancer.

METHODS

The differential miRNA expression profiling in parental MCF-7 cells and its derivative mitoxantrone (MX)-resistant MCF-7 (MCF-7/MX) cells was determined by the microarray analysis. The levels of miR-302S family and BCRP mRNA expression were determined by using Quantitative Real-Time PCR. The targeting effect between the individuals of miR-302S and BCRP mRNA-3'UTR were detected by dual-luciferase reporter assay. Proteins of BCRP are represented by Western blot assay. Cell viability was assessed by MTS assay. Efflux capacity was evaluated using flow cytometry.

RESULTS

The miR-302S family including miR-302a, miR-302b, miR-302c, and miR-302d was significantly down-regulated in BCRP-overexpressing MCF-7/MX cells. Luciferase activity assay showed that miR-302 inhibited BCRP expression by targeting the 3'-untranslated region (UTR) of the BCRP mRNA. Overexpression of miR-302 increased intracellular accumulation of MX and sensitized breast cancer cells to MX. Furthermore, intratumoral injection of miR-302 potentiated the inhibitory effect of MX on tumor growth in mice transplanted with MCF-7/MX cells. Most importantly, miR-302S produced stronger effects than each individual member alone.

CONCLUSIONS

These findings suggest that miR-302 inhibits BCRP expression via targeting the 3'-UTR of BCRP mRNA. miR-302 members may cooperatively downregulate BCRP expression to increase chemosensitivity of breast cancer cells. miR-302 gene cluster may be a potential target for reversing BCRP-mediated chemoresistance in breast cancer.

Differentiation of human neuroblastoma cells toward the osteogenic lineage by mTOR inhibitor

Current hypothesis suggest that tumors can originate from adult cells after a process of 'reprogramming' driven by genetic and epigenetic alterations. These cancer cells, called cancer stem cells (CSCs), are responsible for the tumor growth and metastases. To date, the research effort has been directed to the identification, isolation and manipulation of this cell population. Independently of whether tumors were triggered by a reprogramming of gene expression or seeded by stem cells, their energetic metabolism is altered compared with a normal cell, resulting in a high aerobic glycolytic 'Warburg' phenotype and dysregulation of mitochondrial activity. This metabolic alteration is intricately linked to cancer progression.The aim of this work has been to demonstrate the possibility of differentiating a neoplastic cell toward different germ layer lineages, by evaluating the morphological, metabolic and functional changes occurring in this process. The cellular differentiation reported in this study brings to different conclusions from those present in the current literature. We demonstrate that 'in vitro' neuroblastoma cancer cells (chosen as experimental model) are able to differentiate directly into osteoblastic (by rapamycin, an mTOR inhibitor) and hepatic lineage without an intermediate 'stem' cell step. This process seems owing to a synergy among few master molecules, metabolic changes and scaffold presence acting in a concerted way to control the cell fate.

Development of Novel Antisense Oligonucleotides for the Functional Regulation of RNA-Induced Silencing Complex (RISC) by Promoting the Release of microRNA from RISC

MicroRNAs (miRNAs) are known to be important post-transcription regulators of gene expression. Aberrant miRNA expression is associated with pathological disease processes, including carcinogenesis. Therefore, miRNAs are considered significant therapeutic targets for cancer therapy. MiRNAs do not act alone, but exhibit their functions by forming RNA-induced silencing complex (RISC). Thus, the regulation of RISC activity is a promising approach for cancer therapy. MiRNA is a core component of RISC and is an essential to RISC for recognizing target mRNA. Thereby, it is expected that development of the method to promote the release of miRNA from RISC would be an effective approach for inhibition of RISC activity. In this study, we synthesized novel peptide-conjugated oligonucleotides (RINDA-as) to promote the release of miRNA from RISC. RINDA-as showed a high rate of miRNA release from RISC and high level of inhibitory effect on RISC activity.

Cross platform analysis of methylation, miRNA and stem cell gene expression data in germ cell tumors highlights characteristic differences by tumor histology

Background

Alterations in methylation patterns, miRNA expression, and stem cell protein expression occur in germ cell tumors (GCTs). Our goal is to integrate molecular data across platforms to identify molecular signatures in the three main histologic subtypes of Type I and Type II GCTs (yolk sac tumor (YST), germinoma, and teratoma).

Methods

We included 39 GCTs and 7 paired adjacent tissue samples in the current analysis. Molecular data available for analysis include DNA methylation data (Illumina GoldenGate Cancer Methylation Panel I), miRNA expression (NanoString nCounter miRNA platform), and stem cell factor expression (SABiosciences Human Embryonic Stem Cell Array). We evaluated the cross platform correlations of the data features using the Maximum Information Coefficient (MIC).

Results

In analyses of individual datasets, differences were observed by tumor histology. Germinomas had higher expression of transcription factors maintaining stemness, while YSTs had higher expression of cytokines, endoderm and endothelial markers. We also observed differences in miRNA expression, with miR-371-5p, miR-122, miR-302a, miR-302d, and miR-373 showing elevated expression in one or more histologic subtypes. Using the MIC, we identified correlations across the data features, including six major hubs with higher expression in YST (LEFTY1, LEFTY2, miR302b, miR302a, miR 126, and miR 122) compared with other GCT.

Conclusions

While prognosis for GCTs is overall favorable, many patients experience resistance to chemotherapy, relapse and/or long term adverse health effects following treatment. Targeted therapies, based on integrated analyses of molecular tumor data such as that presented here, may provide a way to secure high cure rates while reducing unintended health consequences.

Emerging role of microRNAs in cancer stem cells: Implications in cancer therapy

A small subset of cancer cells that act as tumor initiating cells or cancer stem cells (CSCs) maintain self-renewal and growth promoting capabilities of cancer and are responsible for drug/treatment resistance, tumor recurrence and metastasis. Due to their potential clinical importance, many researchers have put their efforts over decades to unravel the molecular mechanisms that regulate CSCs functions. MicroRNAs (miRNAs) which are 21-23 nucleotide long, endogenous non-coding RNAs, regulate gene expression through gene silencing at post-transcriptional level by binding to the 3'-untranslated regions or the open reading frames of target genes, thereby result in target mRNA degradation or its translational repression and serve important role in several cellular, physiological and developmental processes. Aberrant miRNAs expression and their implication in CSCs regulation by controlling asymmetric cell division, drug/treatment resistance and metastasis make miRNAs a tool of great therapeutic potential against cancer. Recent advancements on the biological complexities of CSCs, modulation in CSCs properties by miRNA network and development of miRNA based treatment strategies specifically targeting the CSCs as an attractive therapeutic targets for clinical application are being critically analysed.

Human induced pluripotent stem cells in Parkinson's disease: A novel cell source of cell therapy and disease modeling

Human induced pluripotent stem cells (hiPSCs) and human embryonic stem cells (hESCs) are two novel cell sources for studying neurodegenerative diseases. Dopaminergic neurons derived from hiPSCs/hESCs have been implicated to be very useful in Parkinson's disease (PD) research, including cell replacement therapy, disease modeling and drug screening. Recently, great efforts have been made to improve the application of hiPSCs/hESCs in PD research. Considerable advances have been made in recent years, including advanced reprogramming strategies without the use of viruses or using fewer transcriptional factors, optimized methods for generating highly homogeneous neural progenitors with a larger proportion of mature dopaminergic neurons and better survival and integration after transplantation. Here we outline the progress that has been made in these aspects in recent years, particularly during the last year, and also discuss existing issues that need to be addressed.

Pluripotent Conversion of Muscle Stem Cells Without Reprogramming Factors or Small Molecules

Muscle derived stem cells (MDSCs) are multipotent stem cells that can differentiate into several lineages including skeletal muscle precursor cells. Here, we show that MDSCs from myostatin null mice (Mstn (-/-) ) can be readily induced into pluripotent stem cells without using reprogramming factors. Microarray studies revealed a strong upregulation of markers like Leukemia Inhibitory factor (LIF) and Leukemia Inhibitory factor receptor (LIFR) in Mstn (-/-) MDSCs as compared to wild type MDSCs (WT-MDSCs). Furthermore when cultured in mouse embryonic stem cell media with LIF for 95 days, Mstn (-/-) MDSCs formed embryonic stem cell (ES) like colonies. We termed such ES like cells as the culture-induced pluripotent stem cells (CiPSC). CiPSCs from Mstn (-/-) MDSCs were phenotypically similar to ESCs, expressed high levels of Oct4, Nanog, Sox2 and SSEA-1, maintained a normal karyotype. Furthermore, CiPSCs formed embryoid bodies and teratomas when injected into immunocompromised mice. In addition, CiPSCs differentiated into somatic cells of all three lineages. We further show that culturing in ES cell media, resulted in hypermethylation and downregulation of BMP2 in Mstn(-/-) MDSCs. Western blot further confirmed a down regulation of BMP2 signaling in Mstn (-/-) MDSCs in supportive of pluripotent reprogramming. Given that down regulation of BMP2 has been shown to induce pluripotency in cells, we propose that lack of myostatin epigenetically reprograms the MDSCs to become pluripotent stem cells. Thus, here we report the successful establishment of ES-like cells from adult stem cells of the non-germline origin under culture-induced conditions without introducing reprogramming genes.

Sendai virus-mediated expression of reprogramming factors promotes plasticity of human neuroblastoma cells

Neuroblastoma (NB) is the most common extracranial solid tumor that originates from multipotent neural crest cells. NB cell populations that express embryonic stem cell-associated genes have been identified and shown to retain a multipotent phenotype. However, whether somatic reprogramming of NB cells can produce similar stem-cell like populations is unknown. Here, we sought to reprogram NB cell lines using an integration-free Sendai virus vector system. Of four NB cell lines examined, only SH-IN cells formed induced pluripotent stem cell-like colonies (SH-IN 4F colonies) at approximately 6 weeks following transduction. These SH-IN 4F colonies were alkaline phosphatase-positive. Array comparative genomic hybridization analysis indicated identical genomic aberrations in the SH-IN 4F cells as in the parental cells. SH-IN 4F cells had the ability to differentiate into the three embryonic germ layers in vitro, but rather formed NBs in vivo. Furthermore, SH-IN 4F cells exhibited resistance to cisplatin treatment and differentiated into endothelial-like cells expressing CD31 in the presence of vascular endothelial growth factor. These results suggest that SH-IN 4F cells are partially reprogrammed NB cells, and could be a suitable model for investigating the plasticity of aggressive tumors.

Profiling of the small RNA populations in human testicular germ cell tumors shows global loss of piRNAs

Background

Small non-coding RNAs play essential roles in gene regulation, however, the interplay between RNA groups, their expression levels and deregulations in tumorigenesis requires additional exploration. In particular, a comprehensive analysis of microRNA (miRNA), PIWI-interacting RNAs (piRNAs), and tRNA-derived small RNAs in human testis and testicular germ cell tumor (TGCT) is lacking.

Results

We performed small RNA sequencing on 22 human TGCT samples from 5 histological subtypes, 3 carcinoma in situ, and 12 normal testis samples. miRNA was the most common group among the sequences 18–24 nt in length and showed histology-specific expression. In normal samples, most sequences 25–31 nucleotides in length displayed piRNA characteristics, whereas a large proportion of the sequences 32–36 nt length was derived from tRNAs. Expression analyses of the piRNA population demonstrated global loss in all TGCT subtypes compared to normal testis. In addition, three 5′ small tRNA fragments and 23 miRNAs showed significant (p < 10⁻⁶) differential expression in cancer vs normal samples.

Conclusions

We have documented significant changes in the small RNA populations in normal adult testicular tissue and TGCT samples. Although components of the same pathways might be involved in miRNA, piRNA and tRNA-derived small RNA biogenesis, our results showed that the response to the carcinogenic process differs between these pathways, suggesting independent regulation of their biogenesis. Overall, the small RNA deregulation in TGCT provides new insight into the small RNA interplay.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0411-4) contains supplementary material, which is available to authorized users.

Applications of iPSCs in Cancer Research

Induced pluripotent stem cells (iPSCs) derived from reprogrammed somatic cells are emerging as one of the most versatile tools in biomedical research and pharmacological studies. Oncogenic transformation and somatic cell reprogramming are multistep processes that share some common features, and iPSCs generated from cancerous cells can help us better understand the molecular mechanisms underlying the initiation and progression of human cancers and overcome them. Aside from the mechanistic modeling of human tumorigenesis, immediate applications of this technology in cancer research include high-throughput drug screening, toxicological testing, early biomarker identification, and bioengineering of replacement tissues. Here, we review the current advances in generating iPSCs from cancer cell lines and patient-derived primary cancer tissues, and discuss their potential applications.

DNMT-dependent suppression of microRNA regulates the induction of GBM tumor-propagating phenotype by Oct4 and Sox2

Cancer stem-like cells represent poorly differentiated multipotent tumor-propagating cells that contribute disproportionately to therapeutic resistance and tumor recurrence. Transcriptional mechanisms that control the phenotypic conversion of tumor cells lacking tumor-propagating potential to tumor-propagating stem-like cells remain obscure. Here we show that the reprogramming transcription factors Oct4 and Sox2 induce glioblastoma cells to become stem-like and tumor-propagating via a mechanism involving direct DNA methyl transferase (DNMT) promoter transactivation, resulting in global DNA methylation- and DNMT-dependent downregulation of multiple microRNAs (miRNAs). We show that one such downregulated miRNA, miRNA-148a, inhibits glioblastoma cell stem-like properties and tumor-propagating potential. This study identifies a novel and targetable molecular circuit by which glioma cell stemness and tumor-propagating capacity are regulated.

Embryonic MicroRNA-369 Controls Metabolic Splicing Factors and Urges Cellular Reprograming

Noncoding microRNAs inhibit translation and lower the transcript stability of coding mRNA, however miR-369 s, in aberrant silencing genomic regions, stabilizes target proteins under cellular stress. We found that in vitro differentiation of embryonic stem cells led to chromatin methylation of histone H3K4 at the miR-369 region on chromosome 12qF in mice, which is expressed in embryonic cells and is critical for pluripotency. Proteomic analyses revealed that miR-369 stabilized translation of pyruvate kinase (Pkm2) splicing factors such as HNRNPA2B1. Overexpression of miR-369 stimulated Pkm2 splicing and enhanced induction of cellular reprogramming by induced pluripotent stem cell factors, whereas miR-369 knockdown resulted in suppression. Furthermore, immunoprecipitation analysis showed that the Argonaute complex contained the fragile X mental retardation-related protein 1 and HNRNPA2B1 in a miR-369-depedent manner. Our findings demonstrate a unique role of the embryonic miR-369-HNRNPA2B1 axis in controlling metabolic enzyme function, and suggest a novel pathway linking epigenetic, transcriptional, and metabolic control in cell reprogramming.

Reprogramming mediated radio-resistance of 3D-grown cancer cells

In vitro 3D growth of tumors is a new cell culture model that more closely mimics the features of the in vivo environment and is being used increasingly in the field of biological and medical research. It has been demonstrated that cancer cells cultured in 3D matrices are more radio-resistant compared with cells in monolayers. However, the mechanisms causing this difference remain unclear. Here we show that cancer cells cultured in a 3D microenvironment demonstrated an increase in cells with stem cell properties. This was confirmed by the finding that cells in 3D cultures upregulated the gene and protein expression of the stem cell reprogramming factors such as OCT4, SOX2, NANOG, LIN28 and miR-302a, compared with cells in monolayers. Moreover, the expression of β-catenin, a regulating molecule of reprogramming factors, also increased in 3D-grown cancer cells. These findings suggest that cancer cells were reprogrammed to become stem cell-like cancer cells in a 3D growth culture microenvironment. Since cancer stem cell-like cells demonstrate an increased radio-resistance and chemo-resistance, our results offer a new perspective as to why. Our findings shed new light on understanding the features of the 3D growth cell model and its application in basic research into clinical radiotherapy and medicine.

MicroRNA delivery for regenerative medicine

MicroRNA (miRNA) directs post-transcriptional regulation of a network of genes by targeting mRNA. Although relatively recent in development, many miRNAs direct differentiation of various stem cells including induced pluripotent stem cells (iPSCs), a major player in regenerative medicine. An effective and safe delivery of miRNA holds the key to translating miRNA technologies. Both viral and nonviral delivery systems have seen success in miRNA delivery, and each approach possesses advantages and disadvantages. A number of studies have demonstrated success in augmenting osteogenesis, improving cardiogenesis, and reducing fibrosis among many other tissue engineering applications. A scaffold-based approach with the possibility of local and sustained delivery of miRNA is particularly attractive since the physical cues provided by the scaffold may synergize with the biochemical cues induced by miRNA therapy. Herein, we first briefly cover the application of miRNA to direct stem cell fate via replacement and inhibition therapies, followed by the discussion of the promising viral and nonviral delivery systems. Next we present the unique advantages of a scaffold-based delivery in achieving lineage-specific differentiation and tissue development.

Microenvironmental factors involved in human amnion mesenchymal stem cells fate decisions

Human amnion mesenchymal stem cells (HAMCs) show great differentiation and proliferation potential and also other remarkable features that could serve as an outstanding alternative source of stem cells in regenerative medicine. Recent reports have demonstrated various kinds of effective artificial niche that mimic the microenvironment of different types of stem cell to maintain and control their fate and function. The components of the stem cell microenvironment consist mainly of soluble and insoluble factors responsible for regulating stem cell differentiation and self-renewal. Extensive studies have been made on regulating HAMCs differentiation into specific phenotypes; however, the understanding of relevant factors in directing stem cell fate decisions in HAMCs remain underexplored. In this review, we have therefore identified soluble and insoluble factors, including mechanical stimuli and cues from the other supporting cells that are involved in directing HAMCs fate decisions. In order to strengthen the significance of understanding on the relevant factors involved in stem cell fate decisions, recent technologies developed to specifically mimic the microenvironments of specific cell lineages are also reviewed. Copyright © 2015 John Wiley & Sons, Ltd.

A Synthetic DNA-Binding Domain Guides Distinct Chromatin-Modifying Small Molecules to Activate an Identical Gene Network

Synthetic dual-function ligands targeting specific DNA sequences and histone-modifying enzymes were applied to achieve regulatory control over multi-gene networks in living cells. Unlike the broad array of targeting small molecules for histone deacetylases (HDACs), few modulators are known for histone acetyltransferases (HATs), which play a central role in transcriptional control. As a novel chemical approach to induce selective HAT-regulated genes, we conjugated a DNA-binding domain (DBD) "I" to N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-benzamide (CTB), an artificial HAT activator. In vitro enzyme activity assays and microarray studies were used to demonstrate that distinct functional small molecules could be transformed to have identical bioactivity when conjugated with a targeting DBD. This proof-of-concept synthetic strategy validates the switchable functions of HDACs and HATs in gene regulation and provides a molecular basis for developing versatile bioactive ligands.

High miR-196a and low miR-367 cooperatively correlate with unfavorable prognosis of high-grade glioma

Identification of microRNAs (miRNAs) could be beneficial for the diagnosis and prognosis of glioma. Therefore, we attempted to identify and develop specific miRNAs as prognostic and predictive markers for glioma patients. We compared the expression profiles of 365 miRNAs between 4 glioblastomas (GBMs, WHO grade IV) and 4 anaplastic astrocytomas (AAs, WHO grade III) using miRNA qPCR Array. MiR-196a (P = 0.004, fold change = 289.86) and miR-367 (P = 0.044, fold change = 0.03) were identified as the most up-regulated and down-regulated miRNAs in GBMs compared with AAs, respectively. We subsequently examined miR-196a and miR-367 expression levels in an independent series of 63 gliomas including 50 GBMs and 13 AAs, as well as 10 non-neoplastic brain tissues, and statistically analyzed the associations between miRNA expression and clinicopathological characteristics and survivals of these glioma patients. MiR-196a and miR-367 showed significant increased and decreased expression in high-grade gliomas relative to non-neoplastic brains, as well as in GBMs versus AAs, respectively. Additionally, high-miR-196a and low-miR-367 expression, alone or in combination, statistically correlated with aggressive clinicopathological features of gliomas. Furthermore, overall survivals of glioma patients with high-miR-196a, low-miR-367 and high-miR-196a/low-miR-367 expression tended to be shorter than the corresponding control groups (all P ≤ 0.001). Moreover, multivariate analysis indicated high-miR-196a/low-miR-367 as an independent prognostic indicator for glioma patients (P = 0.005, risk ratio = 1.8). Our results suggested that both high-miR-196a and low-miR-367 expression may be associated with aggressive progression and unfavorable clinical outcome in glioma patients. And combination of high-miR-196a and low-miR-367 expression may be a novel biomarker in identifying a poor prognosis group of high-grade glioma.

MicroRNA-Mediated In Vitro and In Vivo Direct Conversion of Astrocytes to Neuroblasts

BACKGROUND

The conversion of astrocytes to neuroblasts holds great promise for treatment of neurodegenerative and traumatic brain diseases.

METHODOLOGY AND PRINCIPAL FINDINGS

Here we have shown that adult human astrocytes could be reprogrammed to neuroblasts by miR-302/367, both in vivo and in vitro. However, the reprogramming of adult mouse astrocytes to neuroblasts required valproic acid (VPA), a histone deacetylase inhibitor. Following induction of astrocytes toward neurons the expression of pluripotency markers were not detected, which suggested direct cell conversion. We did not observed tumor formation during two months follow up.

CONCLUSIONS AND SIGNIFICANCE

These results show that neuroblasts can be generated directly from adult human and mouse astrocytes by miR-302/367-driven induction. This approach seems promising for converting glial scar cells into neuroblasts in a wide range of neurological diseases.

Role of tumor suppressor genes in the cancer-associated reprogramming of human induced pluripotent stem cells

Because of their pluripotent characteristics, human induced pluripotent stem cells (iPSCs) possess great potential for therapeutic application and for the study of degenerative disorders. These cells are generated from normal somatic cells, multipotent stem cells, or cancer cells. They express embryonic stem cell markers, such as OCT4, SOX2, NANOG, SSEA-3, SSEA-4, and REX1, and can differentiate into all adult tissue types, both in vitro and in vivo. However, some of the pluripotency-promoting factors have been implicated in tumorigenesis. Here, we describe the merits of tumor suppresser genes as reprogramming factors for the generation of iPSCs without tumorigenic activity. The initial step of reprogramming is induction of the exogenous pluripotent factors to generate the oxidative stress that leads to senescence by DNA damage and metabolic stresses, thus inducing the expression of tumor suppressor genes such as p21^CIP1 and p16^INK4a through the activation of p53 to be the pre-induced pluripotent stem cells (pre-iPSCs). The later stage includes overcoming the barrier of reprogramming-induced senescence or cell-cycle arrest by shutting off the function of these tumor suppressor genes, followed by the induction of endogenous stemness genes for the full commitment of iPSCs (full-iPSCs). Thus, the reactive oxygen species (ROS) produced by oxidative stress might be critical for the induction of endogenous reprogramming-factor genes via epigenetic changes or antioxidant reactions. We also discuss the critical role of tumor suppressor genes in the evaluation of the tumorigenicity of human cancer cell-derived pluripotent stem cells, and describe how to overcome their tumorigenic properties for application in stem cell therapy in the field of regenerative medicine.

MicroRNAs Induce Epigenetic Reprogramming and Suppress Malignant Phenotypes of Human Colon Cancer Cells

Although cancer is a genetic disease, epigenetic alterations are involved in its initiation and progression. Previous studies have shown that reprogramming of colon cancer cells using Oct3/4, Sox2, Klf4, and cMyc reduces cancer malignancy. Therefore, cancer reprogramming may be a useful treatment for chemo- or radiotherapy-resistant cancer cells. It was also reported that the introduction of endogenous small-sized, non-coding ribonucleotides such as microRNA (miR) 302s and miR-369-3p or -5p resulted in the induction of cellular reprogramming. miRs are smaller than the genes of transcription factors, making them possibly suitable for use in clinical strategies. Therefore, we reprogrammed colon cancer cells using miR-302s and miR-369-3p or -5p. This resulted in inhibition of cell proliferation and invasion and the stimulation of the mesenchymal-to-epithelial transition phenotype in colon cancer cells. Importantly, the introduction of the ribonucleotides resulted in epigenetic reprogramming of DNA demethylation and histone modification events. Furthermore, in vivo administration of the ribonucleotides in mice elicited the induction of cancer cell apoptosis, which involves the mitochondrial Bcl2 protein family. The present study shows that the introduction of miR-302s and miR-369s could induce cellular reprogramming and modulate malignant phenotypes of human colorectal cancer, suggesting that the appropriate delivery of functional small-sized ribonucleotides may open a new avenue for therapy against human malignant tumors.

MiR-302a inhibits the tumorigenicity of ovarian cancer cells by suppression of SDC1

MicroRNA plays an important role in tumor proliferation and cell cycle. In this study, we suggested the level of miR-302a was increasing in the human ovarian cancer cells compared to the normal cells. We aimed to explore the role of miR-302a downregulation in human ovarian cancer cells. Functional studies demonstrate over expression of miR-302a could significant suppress ovarian cancer cells proliferation and promote the cell cycle progress. In vitro reporter assay suggested SDC1 is a direct target gene of miR-302a. Furthermore, the expressions of miR-302a in ovarian cancer cells were inversely corrected with that of SDC1. Upregulation of SDC1 could rescue the effect of over expressed miR-302a in the ovarian cancer cells. These findings provide evidence that miR-302a plays a key role in inhibition of the ovarian cancer cells proliferation, and enhancing the cells' apoptosis through targeting SDC1, and strongly suggest that exogenous miR-302a may have therapeutic value in treating ovarian cancer.

Importance of Myc-related microRNAs in induced pluripotency

Pluripotent stem cells (PSCs) have the capacity to differentiate into any cell type of the body. Therefore, induced pluripotent stem cells (iPSCs) are seen as a promising solution for patient-specific cell therapies. However, the safety is major issue for in vitro methods that are used in induction of pluripotency and also in differentiation of PSCs toward specific cell types. In pioneer studies of iPSC generation, the role of c-Myc has been highlighted as a possible master regulator of pluripotency, but direct c-Myc overexpression is known to prompt drawbacks, especially in human cells. In recent studies, the role of non-protein coding RNA molecules such as microRNAs (miRNAs) has been shown in enhanced reprogramming efficiency. In addition, new reprogramming methods have been ultimately improved by adding miRNAs, in the absence of previous factors. Cross interaction between miRNAs and c-Myc has been also found in differentiation of iPSCs, as well as in reprogramming and self-renewing the pluripotent state. Thence, miRNAs are promising solution for efficiency and safety of iPSC derivation and differentiation methods. The purpose of the present review is to evaluate interaction mechanisms of miRNAs with c-Myc and in iPSC technology.

MicroRNAs: modulators of cell identity, and their applications in tissue engineering

MicroRNAs post-transcriptionally regulate the expression of approximately 60% of the mammalian genes, and have an important role in maintaining the differentiated state of somatic cells through the expression of unique tissue-specific microRNA sets. Likewise, the stemness of pluripotent cells is also sustained by embryonic stem cell-enriched microRNAs, which regulate genes involved in cell cycle, cell signaling and epigenetics, among others. Thus, microRNAs work as modulator molecules that ensure the appropriate expression profile of each cell type. Manipulation of microRNA expression might determine the cell fate. Indeed, microRNA-mediated reprogramming can change the differentiated status of somatic cells towards stemness or, conversely, microRNAs can also transform stem- into differentiated-cells both in vitro and in vivo. In this Review, we outline what is currently known in this field, focusing on the applications of microRNA in tissue engineering.