Abate and switch: miR-145 in stem cell differentiation

Insights into the development of insulin-producing cells: Precursors correlated involvement of microRNA panels

Type 1 diabetes (T1D) is a chronic autoimmune condition characterized by the destruction of pancreatic β cells, recently estimated to affect approximately 8.75 million individuals worldwide. At variance with conventional management of T1D, which relies on exogenous insulin replacement and insulinotropic drugs, emerging therapeutic strategies include transplantation of insulin-producing cells (IPCs) derived from stem cells or fully reprogrammed differentiated cells. Through the in-depth analysis of the microRNAs (miRNAs) involved in the differentiation of human embryonic stem cells (ESCs), mesenchymal stem cells (MSCs), and induced pluripotent stem cells (iPSCs), into insulin-producing cells, this review provides a comprehensive overview of the molecular mechanisms orchestrating the transformation of precursors to cells producing insulin. In addition to miR-375, involved in all differentiation processes, and to miR-7, mir-145 and miR-9, common to the generation of insulin-producing cells from at least two different sources, the literature reveals panels of miRNAs closely related to precursor cells and associated with specific events of the physiological β cell maturation. Since the forced modulation of miRNAs can direct cells development towards insulin-producing cells or modify their fate, a more comprehensive knowledge of the miRNAs involved in the cellular events leading to obtain efficient β cells could improve the diagnostic, prognostic, and therapeutic approaches to diabetes.

"In medio stat virtus": Insights into hybrid E/M phenotype attitudes

Epithelial-mesenchymal plasticity (EMP) refers to the ability of cells to dynamically interconvert between epithelial (E) and mesenchymal (M) phenotypes, thus generating an array of hybrid E/M intermediates with mixed E and M features. Recent findings have demonstrated how these hybrid E/M rather than fully M cells play key roles in most of physiological and pathological processes involving EMT. To this regard, the onset of hybrid E/M state coincides with the highest stemness gene expression and is involved in differentiation of either normal and cancer stem cells. Moreover, hybrid E/M cells are responsible for wound healing and create a favorable immunosuppressive environment for tissue regeneration. Nevertheless, hybrid state is responsible of metastatic process and of the increasing of survival, apoptosis and therapy resistance in cancer cells. The present review aims to describe the main features and the emerging concepts regulating EMP and the formation of E/M hybrid intermediates by describing differences and similarities between cancer and normal hybrid stem cells. In particular, the comprehension of hybrid E/M cells biology will surely advance our understanding of their features and how they could be exploited to improve tissue regeneration and repair.

Two Worlds Colliding: The Interplay Between Natural Compounds and Non-Coding Transcripts in Cancer Therapy

Cancer is a devastating disease and has recently become the leading cause of death in western countries, representing an immense public health burden. When it comes to cancer treatment, chemotherapy is one of the main pillars, especially for advanced stage tumors. Over the years, natural compounds have emerged as one of the most valuable resources for new chemotherapies. It is estimated that more than half of the currently used chemotherapeutic agents are derived from natural compounds. Usually, natural compounds are discovered empirically and an important limitation of introducing new anti-cancer natural products is lack of knowledge with regard to their mechanism of action. Recent data has proven that several natural compounds may function via modulating the expression and function of non-coding RNAs (ncRNAs). NcRNAs are a heterogenous class of RNA molecules which are usually not translated into proteins but have an important role in gene expression regulation and are involved in multiple tumorigenic processes, including response/resistance to pharmacotherapy. In this review, we will discuss how natural compounds function via ncRNAs while summarizing the available data regarding their effects on over 15 types of cancer. Moreover, we will critically analyze the current advances and limitations in understanding the way natural compounds exert these health-promoting effects by acting on ncRNAs. Finally, we will propose several hypotheses that may open new avenues and perspectives regarding the interaction between natural compounds and ncRNAs, which could lead to improved natural compound-based therapeutic strategies in cancer.

The epitranscriptome landscape of small noncoding RNAs in stem cells

Stem cells (SCs) are unique cells that have an inherent ability to self‐renew or differentiate. Both fate decisions are strongly regulated at the molecular level via intricate signaling pathways. The regulation of signaling networks promoting self‐renewal or differentiation was thought to be largely governed by the action of transcription factors. However, small noncoding RNAs (ncRNAs), such as vault RNAs, and their post‐transcriptional modifications (the epitranscriptome) have emerged as additional regulatory layers with essential roles in SC fate decisions. RNA post‐transcriptional modifications often modulate RNA stability, splicing, processing, recognition, and translation. Furthermore, modifications on small ncRNAs allow for dual regulation of RNA activity, at both the level of biogenesis and RNA‐mediated actions. RNA post‐transcriptional modifications act through structural alterations and specialized RNA‐binding proteins (RBPs) called writers, readers, and erasers. It is through SC‐context RBPs that the epitranscriptome coordinates specific functional roles. Small ncRNA post‐transcriptional modifications are today exploited by different mechanisms to facilitate SC translational studies. One mechanism readily being studied is identifying how SC‐specific RBPs of small ncRNAs regulate fate decisions. Another common practice of using the epitranscriptome for regenerative applications is using naturally occurring post‐transcriptional modifications on synthetic RNA to generate induced pluripotent SCs. Here, we review exciting insights into how small ncRNA post‐transcriptional modifications control SC fate decisions in development and disease. We hope, by illustrating how essential the epitranscriptome and their associated proteome are in SCs, they would be considered as novel tools to propagate SCs for regenerative medicine.

MiRNA-145-5p prevents differentiation of oligodendrocyte progenitor cells by regulating expression of myelin gene regulatory factor

The roles of specific microRNAs (miRNA) in oligodendrocyte (OL) differentiation have been studied in depth. However, miRNAs in OL precursors and oligodendrocyte progenitor cells (OPCs) have been less extensively investigated. MiR-145-5p is highly expressed in OPCs relative to differentiating OLs, suggesting this miRNA may serve a function specifically in OPCs. Knockdown of miR-145-5p in primary OPCs led to spontaneous differentiation, as evidenced by an increased proportion of MAG⁺ cells, increased cell ramification, and upregulation of multiple myelin genes including MYRF, TPPP, and MAG, and OL cell cycle exit marker Cdkn1c. Supporting this transition to a differentiating state, proliferation was reduced in miR-145-5p knockdown OPCs. Further, knockdown of miR-145-5p in differentiating OLs showed enhanced differentiation, with increased branching, myelin membrane production, and myelin gene expression. We identified several OL-specific genes targeted by miR-145-5p that exhibited upregulation with miR-145-5p knockdown, including myelin gene regulatory factor (MYRF), that could be regulating the prodifferentiation phenotype in both miR-145 knockdown OPCs and OLs. Indeed, spontaneous differentiation with knockdown of miR-145-5p was fully rescued by concurrent knockdown of MYRF. However, proliferation rate was only partially rescued with MYRF knockdown, and overexpression of miR-145-5p in OPCs increased proliferation rate without affecting expression of already lowly expressed differentiation genes. Taken together, these data suggest that in OPCs miR-145-5p both prevents differentiation at least in part by preventing expression of MYRF and promotes proliferation via as-yet-unidentified mechanisms. These findings clarify the need for differential regulation of miR-145-5p between OPCs and OLs and may have further implications in demyelinating diseases such as multiple sclerosis where miR-145-5p is dysregulated.

miR-145 supports cancer cell survival and shows association with DDR genes, methylation pattern, and epithelial to mesenchymal transition

Background

Despite several reports describing the dual role of miR-145 as an oncogene and a tumor suppressor in cancer, not much has been resolved and understood.

Method

In this study, the potential targets of miR-145 were identified bio-informatically using different target prediction tools. The identified target genes were validated in vitro by dual luciferase assay. Wound healing and soft agar colony assay assessed cell proliferation and migration. miR-145 expression level was measured quantitatively by RT-PCR at different stages of breast tumor. Western blot was used to verify the role of miR-145 in EMT transition using key marker proteins.

Result

Wound healing and soft agar colony assays, using miR-145 over-expressing stably transfected MCF7 cells, unraveled its role as a pro-proliferation candidate in cancerous cells. The association between miR-145 over-expression and differential methylation patterns in representative target genes (DR5, BCL2, TP53, RNF8, TIP60, CHK2, and DCR2) supported the inference drawn. These in vitro observations were validated in a representative set of nodal positive tumors of stage 3 and 4 depicting higher miR-145 expression as compared to early stages. Further, the role of miR-145 in epithelial-mesenchymal (EMT) transition found support through the observation of two key markers, Vimentin and ALDL, where a positive correlation with Vimentin protein and a negative correlation with ALDL mRNA expression were observed.

Conclusion

Our results demonstrate miR-145 as a pro-cancerous candidate, evident from the phenotypes of aggressive cellular proliferation, epithelial to mesenchymal transition, hypermethylation of CpG sites in DDR and apoptotic genes and upregulation of miR-145 in later stages of tumor tissues.

Regulatory feedback loops bridge the human gene regulatory network and regulate carcinogenesis

The development of disease involves a systematic disturbance inside cells and is associated with changes in the interactions or regulations among genes forming biological networks. The bridges inside a network are critical in shortening the distances between nodes. We observed that, inside the human gene regulatory network, one strongly connected core bridged the whole network. Other regulations outside the core formed a weakly connected component surrounding the core like a peripheral structure. Furthermore, the regulatory feedback loops (FBLs) inside the core compose an interface-like structure between the core and periphery. We then denoted the regulatory FBLs as the interface core. Notably, both the cancer-associated and essential biomolecules and regulations were significantly overrepresented in the interface core. These results implied that the interface core is not only critical for the network structure but central in cellular systems. Furthermore, the enrichment of the cancer-associated and essential regulations in the interface core might be attributed to its bridgeness in the network. More importantly, we identified one regulatory FBL between HNF4A and NR2F2 that possesses the highest bridgeness in the interface core. Further investigation suggested that the disturbance of the HNF4A-NR2F2 FBL might protect tumor cells from apoptotic processes. Our results emphasize the relevance of the regulatory network properties to cellular systems and might reveal a critical role of the interface core in cancer.

Design of a nanocomposite substrate inducing adult stem cell assembly and progression toward an Epiblast-like or Primitive Endoderm-like phenotype via mechanotransduction

This work shows that the active interaction between human umbilical cord matrix stem cells and Poly (l-lactide)acid (PLLA) and PLLA/Multi Walled Carbon Nanotubes (MWCNTs) nanocomposite films results in the stem cell assembly as a spheroid conformation and affects the stem cell fate transition. We demonstrated that spheroids directly respond to a tunable surface and the bulk properties (electric, dielectric and thermal) of plain and nanocomposite PLLA films by triggering a mechanotransduction axis. This stepwise process starts from tethering of the cells' focal adhesion proteins to the surface, together with the adherens junctions between cells. Both complexes transmit traction forces to F-Actin stress fibres that link Filamin-A and Myosin-IIA proteins, generating a biological scaffold, with increased stiffening conformation from PLLA to PLLA/MWCNTs, and enable the nucleoskeleton proteins to boost chromatin reprogramming processes. Herein, the opposite expression of NANOG and GATA6 transcription factors, together with other lineage specification related proteins, steer spheroids toward an Epiblast-like or Primitive Endoderm-like lineage commitment, depending on the absence or presence of 1 wt% MWCNTs, respectively. This work represents a pioneering effort to create a stem cell/material interface that can model the stem cell fate transition under growth culture conditions.

What Is New in the miRNA World Regarding Osteosarcoma and Chondrosarcoma?

Despite the availability of multimodal and aggressive therapies, currently patients with skeletal sarcomas, including osteosarcoma and chondrosarcoma, often have a poor prognosis. In recent decades, advances in sequencing technology have revealed the presence of RNAs without coding potential known as non-coding RNAs (ncRNAs), which provides evidence that protein-coding genes account for only a small percentage of the entire genome. This has suggested the influence of ncRNAs during development, apoptosis and cell proliferation. The discovery of microRNAs (miRNAs) in 1993 underscored the importance of these molecules in pathological diseases such as cancer. Increasing interest in this field has allowed researchers to study the role of miRNAs in cancer progression. Regarding skeletal sarcomas, the research surrounding which miRNAs are involved in the tumourigenesis of osteosarcoma and chondrosarcoma has rapidly gained traction, including the identification of which miRNAs act as tumour suppressors and which act as oncogenes. In this review, we will summarize what is new regarding the roles of miRNAs in chondrosarcoma as well as the latest discoveries of identified miRNAs in osteosarcoma.

Large-Scale microRNA Expression Profiling Identifies Putative Retinal miRNA-mRNA Signaling Pathways Underlying Form-Deprivation Myopia in Mice

Development of myopia is associated with large-scale changes in ocular tissue gene expression. Although differential expression of coding genes underlying development of myopia has been a subject of intense investigation, the role of non-coding genes such as microRNAs in the development of myopia is largely unknown. In this study, we explored myopia-associated miRNA expression profiles in the retina and sclera of C57Bl/6J mice with experimentally induced myopia using microarray technology. We found a total of 53 differentially expressed miRNAs in the retina and no differences in miRNA expression in the sclera of C57BL/6J mice after 10 days of visual form deprivation, which induced -6.93 ± 2.44 D (p < 0.000001, n = 12) of myopia. We also identified their putative mRNA targets among mRNAs found to be differentially expressed in myopic retina and potential signaling pathways involved in the development of form-deprivation myopia using miRNA-mRNA interaction network analysis. Analysis of myopia-associated signaling pathways revealed that myopic response to visual form deprivation in the retina is regulated by a small number of highly integrated signaling pathways. Our findings highlighted that changes in microRNA expression are involved in the regulation of refractive eye development and predicted how they may be involved in the development of myopia by regulating retinal gene expression.

Biomolecular bases of the senescence process and cancer. A new approach to oncological treatment linked to ageing

Human ageing is associated with a gradual decline in the physiological functions of the body at multiple levels and it is a key risk factor for many diseases, including cancer. Ageing process is intimately related to widespread cellular senescence, characterised by an irreversible loss of proliferative capacity and altered functioning associated with telomere attrition, accumulation of DNA damage and compromised mitochondrial and metabolic function. Tumour and senescent cells may be generated in response to the same stimuli, where either cellular senescence or transformation would constitute two opposite outcomes of the same degenerative process. This paper aims to review the state of knowledge on the biomolecular relationship between cellular senescence, ageing and cancer. Importantly, many of the cell signalling pathways that are found to be altered during both cellular senescence and tumourigenesis are regulated through shared epigenetic mechanisms and, therefore, they are potentially reversible. MicroRNAs are emerging as pivotal players linking ageing and cancer. These small RNA molecules have generated great interest from the point of view of future clinical therapy for cancer because successful experimental results have been obtained in animal models. Micro-RNA therapies for cancer are already being tested in clinical phase trials. These findings have potential importance in cancer treatment in aged people although further research-based knowledge is needed to convert them into an effective molecular therapies for cancer linked to ageing.

Therapeutic targeting of CBP/β-catenin signaling reduces cancer stem-like population and synergistically suppresses growth of EBV-positive nasopharyngeal carcinoma cells with cisplatin

Nasopharyngeal carcinoma (NPC) is an EBV-associated epithelial malignancy prevalent in southern China. Presence of treatment-resistant cancer stem cells (CSC) may associate with tumor relapse and metastasis in NPC. ICG-001 is a specific CBP/β-catenin antagonist that can block CBP/β-catenin-mediated transcription of stem cell associated genes and enhance p300/β-catenin-mediated transcription, thereby reducing the CSC-like population via forced differentiation. In this study, we aimed to evaluate the effect of ICG-001 on the CSC-like population, and the combination effect of ICG-001 with cisplatin in the C666-1 EBV-positive NPC cells. Results showed that ICG-001 inhibited C666-1 cell growth and reduced expression of CSC-associated proteins with altered expression of epithelial-mesenchymal transition (EMT) markers. ICG-001 also inhibited C666-1 tumor sphere formation, accompanied with reduced SOX2^hi/CD44^hi CSC-like population. ICG-001 was also found to restore the expression of a tumor suppressive microRNA-145 (miR-145). Ectopic expression of miR-145 effectively repressed SOX2 protein expression and inhibited tumor sphere formation. Combination of ICG-001 with cisplatin synergistically suppressed in vitro growth of C666-1 cells and significantly suppressed growth of NPC xenografts. These results suggested that therapeutically targeting of the CBP/β-catenin signaling pathway with ICG-001 can effectively reduce the CSC-like population and combination with cisplatin can effectively suppress the growth of NPC.

Double-negative feedback loop between ZEB2 and miR-145 regulates epithelial-mesenchymal transition and stem cell properties in prostate cancer cells

The invasion and metastasis of tumors are triggered by an epithelial to mesenchymal transition (EMT), which is regulated by microRNAs (miRNAs). EMT also promotes malignant tumor progression and the maintenance of the stem cell property, which endows cancer cells with the capabilities of self-renewal and immortalized proliferation. The transcriptional repressor zinc-finger E-box binding homeobox 2 (ZEB2), as an EMT activator, might be an important promoter of metastasis in some tumors. Here, we report that ZEB2 directly represses the transcription of miR-145, which is a strong repressor of EMT. In turn, ZEB2 is also a direct target of miR-145. Further, our findings show that the downregulation of ZEB2 not only represses invasion, migration, EMT, and the stemness of prostate cancer (PCa) cells, but also suppresses the capability of PC-3 cells to invade bone in vivo. Importantly, the expression level of ZEB2 as revealed by immunohistochemical analysis is positively correlated to bone metastasis, the serum free PSA level, the total PSA level, and the Gleason score in PCa patients and is negatively correlated with miR-145 expression in primary PCa specimens. Thus, our findings demonstrate a double-negative feedback loop between ZEB2 and miR-145 and indicate that the ZEB2/miR-145 double-negative feedback loop plays a significant role in the control of EMT and stem cell properties during the bone metastasis of PCa cells. These results suggest that the double-negative feedback loop between ZEB2 and miR-145 contributes to PCa progression and metastasis and might have therapeutic relevance for the bone metastasis of PCa.

The chemosensitivity of testicular germ cell tumors

Although rare cancers overall, testicular germ cell tumors (TGCTs) are the most common type of cancer in young males below 40 years of age. Both subtypes of TGCTs, i.e., seminomas and non-seminomas, are highly curable and the majority of even metastatic patients may expect to be cured. These high cure rates are not due to the indolent nature of these cancers, but rather to their sensitivity to chemotherapy (and for seminomas to radiotherapy). The delineation of the cause of chemosensitivity at the molecular level is of paramount importance, because it may provide insights into the minority of TGCTs that are chemo-resistant and, thereby, provide opportunities for specific therapeutic interventions aimed at reverting them to chemosensitivity. In addition, delineation of the molecular basis of TGCT chemo-sensitivity may be informative for the cause of chemo-resistance of other more common types of cancer and, thus, may create new therapeutic leads. p53, a frequently mutated tumor suppressor in cancers in general, is not mutated in TGCTs, a fact that has implications for their chemo-sensitivity. Oct4, an embryonic transcription factor, is uniformly expressed in the seminoma and embryonic carcinoma components of non-seminomas, and its interplay with p53 may be important in the chemotherapy response of these tumors. This interplay, together with other features of TGCTs such as the gain of genetic material from the short arm of chromosome 12 and the association with disorders of testicular development, will be discussed in this paper and integrated in a unifying hypothesis that may explain their chemo-sensitivity.

Dendrosomal curcumin nanoformulation downregulates pluripotency genes via miR-145 activation in U87MG glioblastoma cells

Glioblastoma is an invasive tumor of the central nervous system. Tumor recurrence resulting from ineffective current treatments, mainly due to the blood-brain barrier, highlights the need for innovative therapeutic alternatives. The recent availability of nanotechnology represents a novel targeted strategy in cancer therapy. Natural products have received considerable attention for cancer therapy because of general lower side effects. Curcumin is a new candidate for anticancer treatment, but its low bioavailability and water solubility represent the main disadvantages of its use. Here, curcumin was efficiently encapsulated in a nontoxic nanocarrier, termed dendrosome, to overcome these problems. Dendrosomal curcumin was prepared as 142 nm spherical structures with constant physical and chemical stability. The inhibitory role of dendrosomal curcumin on the proliferation of U87MG cells, a cellular model of glioblastoma, was evaluated by considering master genes of pluripotency and regulatory miRNA (microribonucleic acid). Methylthiazol tetrazolium assay and flow cytometry were used to detect the antiproliferative effects of dendrosomal curcumin. Annexin-V-FLUOS and caspase assay were used to quantify apoptosis. Real-time polymerase chain reaction was used to analyze the expression of OCT4 (octamer binding protein 4) gene variants (OCT4A, OCT4B, and OCT4B1), SOX-2 (SRY [sex determining region Y]-box 2), Nanog, and miR-145. Dendrosomal curcumin efficiently suppresses U87MG cells growth with no cytotoxicity related to dendrosome. Additionally, the accumulation of cells in the SubG1 phase was observed in a time- and dose-dependent manner as well as higher rates of apoptosis after dendrosomal curcumin treatment. Conversely, nonneoplastic cells were not affected by this formulation. Dendrosomal curcumin significantly decreased the relative expression of OCT4A, OCT4B1, SOX-2, and Nanog along with noticeable overexpression of miR-145 as the upstream regulator. This suggests that dendrosomal curcumin reduces the proliferation of U87MG cells through the downregulation of OCT4 (octamer binding protein 4) variants and SOX-2 (SRY [sex determining region Y]-box 2) in an miR-145-dependent manner.

MicroRNA as potential modulators in chemoresistant high-grade gliomas

Gliomas account for 70% of human malignant primary brain tumours. The most common form is glioblastoma multiforme, World Health Organization grade IV. Despite the implementation of post-operative adjuvant radiotherapy with concurrent temozolomide (TMZ), the disease's overall prognosis remains dismal. TMZ is currently the only mono-chemotherapeutic agent for newly-diagnosed high-grade glioma patients and acquired resistance inevitably occurs in the majority of such patients, further limiting treatment options. Therefore, there is an urgent need to better understand the underlying mechanisms involved in TMZ resistance, a critical step to developing effective, targeted treatments. An emerging body of evidence suggests the intimate involvement of a novel class of nucleic acid, microRNA (miRNA), in tumorigenesis and disease progression for a number of human malignancies, including primary brain tumours. miRNA are short, single-stranded, non-coding RNA (∼22 nucleotides) that function as post-transcriptional regulators of gene expression. This review provides an overview of the key treatment obstacles faced in patients with high-grade gliomas, especially in the context of recurrent, chemoresistant tumours and the potential roles of miRNA in chemoresistance and management of this disease.

MiR-145 functions as a tumor-suppressive RNA by targeting Sox9 and adducin 3 in human glioma cells

BACKGROUND

MicroRNAs (miRNAs) are increasingly being recognized as being involved in cancer development and progression in gliomas.

METHODS

Using a model cell system developed in our lab to study glioma progression comprising human neuroglial culture (HNGC)-1 and HNGC-2 cells, we report here that miR-145 is one of the miRNAs significantly downregulated during malignant transformation in glioblastoma multiforme (GBM). In a study using tumor samples derived from various glioma grades, we show that expression of miR-145 is decreased in a graded manner, with GBM patients showing lowest expression relative to lower-grade gliomas (P < .05) and normal brain tissues (P < .0001). Functional studies involving ectopic expression of miR-145 in glioma cells had a negative impact on cell proliferation and tumor development, as well as invasion and induced apoptosis, providing further support to the concept that inactivation of miR-145 is important for glioma disease pathogenesis. More notably, these growth-suppressive effects of miR-145 are mediated through its target proteins Sox9 and the cell adhesion-associated molecule adducin 3 (ADD3).

RESULTS

Inhibiting Sox9 and ADD3 rescued effects of miR-145 loss. Interestingly, miR-145 loss in glioma cells led to overexpression of molecules involved in cell proliferation, like cyclin D1, c-myc, and N-myc, as well as enhanced expression of cell adhesion- and invasion-related molecules N-cadherin and E-cadherin, an effect which was again restored upon miR-145 overexpression in glioma cells. The miR-145 promoter was methylated at its cytosine-phosphate-guanine (CpG) islands in the glioma cell lines studied.

CONCLUSION

Our study demonstrates that miR-145 has a tumor-suppressive function in glioblastoma in that it reduces proliferation, adhesion, and invasion of glioblastoma cells, apparently by suppressing the activity of oncogenic proteins Sox9 and ADD3. Reduced levels of miR-145 may lead to neoplastic transformation and malignant progression in glioma due to unregulated activity of these proteins.

The microRNA-302-367 cluster suppresses the proliferation of cervical carcinoma cells through the novel target AKT1

The miR-302-367 cluster is specifically expressed in human embryonic stem cells and has been shown to convert human somatic cells into induced pluripotent stem cells. Here, we investigated the role of the miR-302-367 cluster in cervical carcinoma. The cluster was not endogenously expressed in cervical cancer cells, and its ectopic expression did not reprogram the cervical cancer cells to an embryonic stem cell-like state. However, ectopic expression of the miR-302-367 cluster in HeLa and SiHa cervical cancer cells inhibited cell proliferation and tumor formation by blocking the G1/S cell cycle transition. We identified a new cell cycle regulatory pathway in which the miR-302-367 cluster directly down-regulated both cyclin D1 and AKT1 and indirectly up-regulated p27(Kip1) and p21(Cip1), leading to the suppression of cervical cancer cell proliferation. Our findings suggest that the miR-302-367 cluster may be used as a therapeutic reagent for the treatment of cervical carcinoma.

A comparison of pluripotency and differentiation status of four mesenchymal adult stem cells

The self-renewal and differentiation status of a stem cell is very important in the applications concerning regenerative medicine. Proliferation capacity, differentiation potentials and epigenetic properties of stem cells differ between sources. Studies have shown the high potentials of stem cells in iPS reprogramming. To examine this; we have compared the stem-ness and differential potential of four adult stem cells from common sources. We show a correlation between pluripotency and differentiation status of each stem cell with available data on the reprogramming efficiency. Four human adult stem cells including, adipose tissue-mesenchymal stem cells (AT-MSC), bone marrow mesenchymal stem cells (BM-MSCs), nasal septum derived multipotent progenitors (NSP) and umbilical cord blood stem cells (USSCs) were isolated and characterized. The self- renewal and differentiation potentials of each stem cell were assessed. Stem-ness transcription factors and the propagation potentials of all cells were analyzed. Furthermore the differentiation potentials were evaluated using treatment with induction factors and specific MicroRNA profile. Real-time PCR results showed that our stem cells express innate differentiation factors, miR145 and Let7g, which regulate the stem-ness and also the reprogramming potentials of each stem cell. To complete our view, we compared the propagation and differentiation potentials by correlating the stem-ness gene expression with differentiation MicroRNAs, also the direct effect of these factors on reprogramming. Our results suggest that the potentials of adipose tissue stem cells for GMP (Good Manufacturing Practice) compliant starting material are adequate for clinical applications. Our results indicate a low risk potential for AT-MSCs as starting material for iPS production. Although let7g and mir145 are well known for their differentiation promoting effects, but function more of a fine tuning system between self-renewal and differentiation status.

miR-145 is differentially regulated by TGF-β1 and ischaemia and targets Disabled-2 expression and wnt/β-catenin activity

The effect of wnt/β-catenin signalling in the response to acute myocardial infarction (AMI) remains controversial. The membrane receptor adaptor protein Disabled-2 (Dab2) is a tumour suppressor protein and has a critical role in stem cell specification. We recently demonstrated that down-regulation of Dab2 regulates cardiac protein expression and wnt/β-catenin activity in mesenchymal stem cells (MSC) in response to transforming growth factor-β(1) (TGF-β(1)). Although Dab2 expression has been shown to have effects in stem cells and tumour suppression, the molecular mechanisms regulating this expression are still undefined. We identified putative binding sites for miR-145 in the 3'-UTR of Dab2. In MSC in culture, we observed that TGF-β(1) treatment led to rapid and sustained up-regulation of pri-miR-145. Through gain and loss of function studies we demonstrate that miR-145 up-regulation was required for the down-regulation of Dab2 and increased β-catenin activity in response to TGF-β(1). To begin to define how Dab2 might regulate wnt/β-catenin in the heart following AMI, we quantified myocardial Dab2 as a function of time after left anterior descending ligation. There was no significant Dab2 expression in sham-operated myocardium. Following AMI, Dab2 levels were rapidly up-regulated in cardiac myocytes in the infarct border zone. The increase in cardiac myocyte Dab2 expression correlated with the rapid and sustained down-regulation of myocardial pri-miR-145 expression following AMI. Our data demonstrate a novel and critical role for miR-145 expression as a regulator of Dab2 expression and β-catenin activity in response to TGF-β(1) and hypoxia.

Over-expression of miR-145 enhances the effectiveness of HSVtk gene therapy for malignant glioma

This study attempts to combine two findings toward developing a rational strategy for improved therapy for glioma. One of the findings, made in this pre-clinical study, is that an hTERT-targeting ribozyme-controlled HSVtk gene (hTERT.Rz.HSVtk) exerts anti-tumor effects. The second observation is that the over-expression of a small noncoding RNA, miR-145, causes down-regulation of metastasis-related genes, such as PLAUR, SPOCK3, ADAM22, SLC7A5 and FASCN1. While blocking in vivo tumor growth only slightly, over-expression of miR-145 significantly inhibits both the migration and invasion of U87MG/U373MG glioma cells. We hypothesized that a simultaneous adenoviral-mediated over-expression of miR-145 might enhance the anti-tumor effects of hTERT.Rz.HSVtk and that a combination therapy with miR-145 and the HSVtk gene would be an effective approach for treating glioma. We tested this by developing adenoviral vectors that over-express miR-145 under the CMV promoter and employing them in combination with hTERT.Rz.HSVtk expression, both in vitro and in vivo in animal studies. We found that the adenovirus Ad5CMV.Rz.HSVtk.miR145 harboring an HSVtk expression cassette plus miR-145 produced prolonged survival benefits compared to administration of Ad5CMV.Rz.HSVtk or Ad5CMV.miR-145 alone. This study demonstrates that combination therapy using the hTERT.Rz.HSVtk gene together with miR-145 over-expression produces enhanced anti-tumor effects compared to that resulting from hTERT.Rz.HSVtk gene therapy alone.

NEDD9, a novel target of miR-145, increases the invasiveness of glioblastoma

miR-145 is an important repressor of pluripotency in embryonic stem cells and a tumor suppressor in different cancers. Here, we found that miR-145 is strongly down-regulated in glioblastoma (GB) specimens and corresponding glioblastomaneurospheres (GB-NS, containing GB stem-like cells) compared to normal brain (NB) and to low-grade gliomas (LGG). We observed a direct correlation between miR-145 expression and the progression-free survival (PFS) in LGG patients and overall survival (OS) in GB patients. Using microarray analysis, we identified relevant differences in gene expression profiles between GB-NS over-expressing miR-145 (miRover-NS) and GB-NS Empty (Empty-NS). We focused our attention on HEF1/Cas-L/NEDD9, a scaffold protein involved in invasion in several types of cancer. We confirmed a significant down-regulation of NEDD9 in miRover-NS and we found a higher expression in GB and GB-NS compared to NB. Approximately 50% of LGG patients expressed higher levels of NEDD9 than NB, and the PFS of such patients was shorter than in patients expressing lower levels of NEDD9. We observed that intracranial injection of GB-NS over-expressing miR-145 delays significantly tumor development :deriving tumors showed a significant down-regulation of NEDD9. In addition, we demonstrated a significant inhibition of invasion in silencing experiments with GB-NS shNEDD9 (shNEDD9), and an up-regulation of miR-145 in shNEDD9, suggesting a doublenegative feedback loop between miR-145 and NEDD9. Our results demonstrate the critical role of miR-145 and NEDD9 in regulating glioblastoma invasion and suggest a potential role of NEDD9 as a biomarker for glioma progression.

Hypoxia modulates the undifferentiated phenotype of human renal inner medullary CD133+ progenitors through Oct4/miR-145 balance

Low-oxygen tension is an important component of the stem cell microenvironment. In rodents, renal resident stem cells have been described in the papilla, a relatively hypoxic region of the kidney. In the present study, we found that CD133+ cells, previously described as renal progenitors in the human cortex, were enriched in the renal inner medulla and localized within the Henle's loop and thin limb segments. Once isolated, the CD133+ cell population expressed renal embryonic and stem-related transcription factors and was able to differentiate into mature renal epithelial cells. When injected subcutaneously in immunodeficient mice within Matrigel, CD133+ cells generated canalized structures positive for renal specific markers of different nephron segments. Oct4A levels and differentiation potential of papillary CD133+ cells were higher than those of CD133+ cells from cortical tubuli. Hypoxia was able to promote the undifferentiated phenotype of CD133+ progenitors from papilla. Hypoxia stimulated clonogenicity, proliferation, vascular endothelial growth factor synthesis, and expression of CD133 that were in turn reduced by epithelial differentiation with parallel HIF-1α downregulation. In addition, hypoxia downregulated microRNA-145 and promoted the synthesis of Oct4A. Epithelial differentiation increased microRNA-145 and reduced Oct4 level, suggesting a balance between Oct4 and microRNA-145. MicroRNA-145 overexpression in CD133+ cells induced downrelation of Oct4A at the protein level, inhibited cell proliferation, and stimulated terminal differentiation. This study underlines the role of the hypoxic microenvironment in controlling the proliferation and maintaining a progenitor phenotype and stem/progenitor properties of CD133+ cells of the nephron. This mechanism may be at the basis of the maintenance of a CD133+ population in the papillary region and may be involved in renal regeneration after injury.

Differentiation MicroRNAs Affect Stemness Status of USSCs

BACKGROUND

MicroRNAs are endogenous non-coding RNAs with important regulatory and cell fate functions. Many studies have shown that several microRNAs are obviously up-regulated during stem cell differentiation. The question rises here is weather inhibiting differentiation will affect the stemness and self renewal status of stem cells.

METHODS

miRCURY ™LNA microRNA inhibitor (anti-miR-145 and anti-let7g) are a sequence-specific and chemically modified oligonucleotide that specifically target and knockdown miR-145 and let7g miRNA molecules. Unrestricted somatic stem cells (USSCs) were isolated from umbilical cord blood and treated with LNAs. The effect of anti-miRNA transfection was assessed by quantitative real-time PCR.

RESULTS

Real-time PCR showed that LNA was efficiently introduced into the cells and reduced miR145 and Let7g expression levels to 40% and 10% in relation to corresponding scramble control, respectively. Gene expression analysis as to self renewal and expansion showed more than 3.5 fold up regulation in Oct4 in cells treated with mir145 inhibition. Similarly a significant up to 2.5 fold up-regulation in Oct4 and cMyc expression was observed in samples treated with anti-let7g.

CONCLUSION

Suppression in differentiation inducing microRNAs (miR-145 and let7g) can enhance the self renewal and stemness status of USSCs at transcriptional level.

down-regulation of Kruppel-like factor-4 (KLF4) by microRNA-143/145 is critical for modulation of vascular smooth muscle cell phenotype by transforming growth factor-beta and bone morphogenetic protein 4

In the postnatal vasculature, fully differentiated and quiescent vascular smooth muscle cells (VSMCs) in a "contractile" phenotype are required for the normal regulation of vascular tone. The transforming growth factor-β (TGF-β) superfamily of growth factors (TGF-βs and bone morphogenetic proteins (BMPs)) are potent inducers of contractile phenotype and mediate (i) induction of contractile genes, and (ii) inhibition of VSMC growth and migration. Transcription of contractile genes is positively regulated by a regulatory DNA element called a CArG box. The CArG box is activated by the binding of serum response factor and its coactivators, myocardin (Myocd) or Myocd-related transcription factors (MRTFs). Krüppel-like factor-4 (KLF4) is known to inhibit activation of the CArG box. However, the potential role of KLF4 in the contractile activities of TGF-β or BMP has not been explored. Here, we demonstrate that TGF-β and BMP4 rapidly down-regulate KLF4 through induction of microRNA-143 (miR-143) and miR-145, which leads to a reduction of KLF4 transcripts and decreased KLF4 protein expression. Inhibition of miR-145 prevents down-regulation of KLF4 and activation of contractile genes by TGF-β or BMP4, suggesting that modulation of KLF4 is a prerequisite for induction of contractile genes by TGF-β and BMP4. Interestingly, both TGF-β and BMP4 activate transcription of the miR-143/145 gene cluster through the CArG box, however, TGF-β mediates this effect through induction of Myocd expression, whereas BMP4 utilizes nuclear translocation of MRTF-A. Thus, this study sheds light on both the similarities and the differences of TGF-β and BMP4 signaling in the regulation of KLF4 and contractile genes.

De novo myocardial regeneration: advances and pitfalls

The capability of adult tissue-derived stem cells for cardiogenesis has been extensively studied in experimental animals and clinical studies for treatment of postischemic cardiomyopathy. The less-than-anticipated improvement in the heart function in most clinical studies with skeletal myoblasts and bone marrow cells has warranted a search for alternative sources of stem cells. Despite their multilineage differentiation potential, ethical issues, teratogenicity, and tissue rejection are main obstacles in developing clinically feasible methods for embryonic stem cell transplantation into patients. A decade-long research on embryonic stem cells has paved the way for discovery of alternative approaches for generating pluripotent stem cells. Genetic manipulation of somatic cells for pluripotency genes reprograms the cells to pluripotent status. Efforts are currently focused to make reprogramming protocols safer for clinical applications of the reprogrammed cells. We summarize the advancements and complicating features of stem cell therapy and discuss the decade-and-a-half-long efforts made by stem cell researchers for moving the field from bench to the bedside as an adjunct therapy or as an alternative to the contemporary therapeutic modalities for routine clinical application. The review also provides a special focus on the advancements made in the field of somatic cell reprogramming.

Differential expression of cellular microRNAs in HPV-11 transfected cells. An analysis by three different array platforms and qRT-PCR

Human papillomavirus type 11 (HPV-11) infects the genital and the respiratory tract leading to condylomas and respiratory papillomatosis. HPV infections are restricted to epithelial tissue and the progression through the virus lifecycle is tightly coordinated to the differentiation of the host cell. The changes of cellular microRNAs by HPV-11 gene expression were investigated in a cell culture model of HaCaT cells transfected with HPV-11, with the goal of understanding which cellular processes were affected by the virus. Human microRNA profiling was conducted on three different array platform systems and because very few microRNAs (miR-663, -638, -149* and -92b*) were consistently found in all three array data sets we performed extensive statistical analyses of the array data and the qRT-PCR validation. We assume that the most reliable differentially expressed microRNAs are the ones identified by more than one array platform. We also show that TaqMan® qRT-PCR validation is of limited use for less abundant microRNAs.

Analysis of microRNA transcriptome by deep sequencing of small RNA libraries of peripheral blood

Background

MicroRNAs are a class of small non-coding RNAs that regulate mRNA expression at the post - transcriptional level and thereby many fundamental biological processes. A number of methods, such as multiplex polymerase chain reaction, microarrays have been developed for profiling levels of known miRNAs. These methods lack the ability to identify novel miRNAs and accurately determine expression at a range of concentrations. Deep or massively parallel sequencing methods are providing suitable platforms for genome wide transcriptome analysis and have the ability to identify novel transcripts.

Results

The results of analysis of small RNA sequences obtained by Solexa technology of normal peripheral blood mononuclear cells, tumor cell lines K562 and HL60 are presented. In general K562 cells displayed overall low level of miRNA population and also low levels of DICER. Some of the highly expressed miRNAs in the leukocytes include several members of the let-7 family, miR-21, 103, 185, 191 and 320a. Comparison of the miRNA profiles of normal versus K562 or HL60 cells revealed a specific set of differentially expressed molecules. Correlation of the miRNA with that of mRNA expression profiles, obtained by microarray, revealed a set of target genes showing inverse correlation with miRNA levels. Relative expression levels of individual miRNAs belonging to a cluster were found to be highly variable. Our computational pipeline also predicted a number of novel miRNAs. Some of the predictions were validated by Real-time RT-PCR and or RNase protection assay. Organization of some of the novel miRNAs in human genome suggests that these may also be part of existing clusters or form new clusters.

Conclusions

We conclude that about 904 miRNAs are expressed in human leukocytes. Out of these 370 are novel miRNAs. We have identified miRNAs that are differentially regulated in normal PBMC with respect to cancer cells, K562 and HL60. Our results suggest that post - transcriptional processes may play a significant role in regulating levels of miRNAs in tumor cells. The study also provides a customized automated computation pipeline for miRNA profiling and identification of novel miRNAs; even those that are missed out by other existing pipelines. The Computational Pipeline is available at the website: http://mirna.jnu.ac.in/deep_sequencing/deep_sequencing.html

Human pluripotent stem cells: from biology to cell therapy

Human pluripotent stem cells (PSCs), encompassing embryonic stem cells and induced pluripotent stem cells, proliferate extensively and differentiate into virtually any desired cell type. PSCs endow regenerative medicine with an unlimited source of replacement cells suitable for human therapy. Several hurdles must be carefully addressed in PSC research before these theoretical possibilities are translated into clinical applications. These obstacles are: (1) cell proliferation; (2) cell differentiation; (3) genetic integrity; (4) allogenicity; and (5) ethical issues. We discuss these issues and underline the fact that the answers to these questions lie in a better understanding of the biology of PSCs. To contribute to this aim, we have developed a free online expression atlas, Amazonia!, that displays for each human gene a virtual northern blot for PSC samples and adult tissues (http://www.amazonia.transcriptome.eu).

EWS-FLI-1 modulates miRNA145 and SOX2 expression to initiate mesenchymal stem cell reprogramming toward Ewing sarcoma cancer stem cells

Cancer stem cells (CSCs) display plasticity and self-renewal properties reminiscent of normal tissue stem cells, but the events responsible for their emergence remain obscure. We recently identified CSCs in Ewing sarcoma family tumors (ESFTs) and showed that they retain mesenchymal stem cell (MSC) plasticity. In the present study, we addressed the mechanisms that underlie ESFT CSC development. We show that the EWS-FLI-1 fusion gene, associated with 85%-90% of ESFTs and believed to initiate their pathogenesis, induces expression of the embryonic stem cell (ESC) genes OCT4, SOX2, and NANOG in human pediatric MSCs (hpMSCs) but not in their adult counterparts. Moreover, under appropriate culture conditions, hpMSCs expressing EWS-FLI-1 generate a cell subpopulation displaying ESFT CSC features in vitro. We further demonstrate that induction of the ESFT CSC phenotype is the result of the combined effect of EWS-FLI-1 on its target gene expression and repression of microRNA-145 (miRNA145) promoter activity. Finally, we provide evidence that EWS-FLI-1 and miRNA-145 function in a mutually repressive feedback loop and identify their common target gene, SOX2, in addition to miRNA145 itself, as key players in ESFT cell differentiation and tumorigenicity. Our observations provide insight for the first time into the mechanisms whereby a single oncogene can reprogram primary cells to display a CSC phenotype.

Primary brain tumors, neural stem cell, and brain tumor cancer cells: where is the link?

The discovery of brain tumor-derived cells (BTSC) with the properties of stem cells has led to the formulation of the hypothesis that neural stem cells could be the cell of origin of primary brain tumors (PBT). In this review we present the most common molecular changes in PBT, define the criteria of identification of BTSC and discuss the similarities between the characteristics of these cells and those of the endogenous population of neural stem cells (NPCs) residing in germinal areas of the adult brain. Finally, we propose possible mechanisms of cancer initiation and progression and suggest a model of tumor initiation that includes intrinsic changes of resident NSC and potential changes in the microenvironment defining the niche where the NSC reside.