Micro-RNA mediated regulation of proliferation, self-renewal and differentiation of mammalian stem cells

Interaction Between Malat1 and miR-499-5p Regulates Meis1 Expression and Function with a Net Impact on Cell Proliferation

Meis1 is a transcription factor involved in numerous functions including development and proliferation and has been previously shown to harness cell cycle progression. In this study, we used in silico analysis to predict that miR-499-5p targets Meis1 and that Malat1 sponges miR-499-5p. For the first time, we demonstrated that the overexpression of miR-499-5p led to the downregulation of Meis1 mRNA and protein in C166 cells by directly binding to its 3'UTR. Moreover, knocking down Malat1 increased miR-499-5p expression, subsequently suppressing Meis1. Through BrdU incorporation assay, we showed that the knockdown of Malat1, Meis1, or mimicking with miR-499-5p promoted cell proliferation. Enrichment analyses on proteins identified via mass spectrometry after manipulating Malat1, miR-499-5p, or Meis1 revealed a multitude of differentially expressed proteins related to cell cycle, cell division, and key pathways like Wnt and mTOR, essential for cell proliferation. Collectively, our findings confirm that Malat1 sponges miR-499-5p, regulating Meis1, and that Malat1/miR-499-5p/Meis1 could potentially form an axis that has a pivotal influence on cellular proliferation.

MiR-142-3p suppresses the proliferation, migration and invasion through inhibition of NR2F6 in lung adenocarcinoma

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death worldwide and lung adenocarcinoma is its main type. MicroRNAs are small, non-coding and single-strand RNAs that regulate gene expression in human cancers. The aim of our study is to investigate the underlying molecular mechanism of miR-142-3p in NSCLC. The expression of miR-142-3p in lung adenocarcinoma tissues and cells was detected by RT-qPCR. Next, cell proliferation, migration, invasion and apoptosis were examined by CCK-8, scratch assay, transwell assay and flow cytometry in A549 and HCC827 cells, respectively. Then, the target of miR-142-3p was predicted by targetscanHuman 7.2 and confirmed using dual-luciferase reporter assay. Additionally, RT-qPCR and western blot were used to detect the expression of NR2F6, MMP2, MMP9 and caspase-3. The results showed that miR-142-3p expression was significantly decreased in tumor tissues and cells. Overexpression of miR-142-3p inhibited the proliferation, migration, invasion and promoted cell apoptosis in vitro, while knockdown of miR-142-3p had reversed function. Furthermore, NR2F6 was identified as a direct target of miR-142-3p, which was negatively correlated with miR-142-3p expression. Finally, miR-142-3p overexpression suppressed the expression of NR2F6, MMP2 and MMP9, but improved caspase-3 expression, while miR-142-3p knockdown got the opposite expression results. Suppressing MMP2 and MMP9 activities inhibited cell invasion. In summary, these findings indicated that miR-142-3p inhibits lung adenocarcinoma cell proliferation, migration and invasion, and enhances cell apoptosis by targeting NR2F6, suggesting that miR-142-3p may be a novel therapeutic target for lung adenocarcinoma treatment.

MiR-744 increases tumorigenicity of pancreatic cancer by activating Wnt/β-catenin pathway

The Wnt/β-catenin signaling pathway, commonly hyperactivated in pancreatic cancer, has been reported to play an important role in the maintenance of stemness of cancer stem cells (CSCs), which is closely related to the progression of pancreatic cancer. Therefore, exploring the regulatory mechanism in Wnt/β-catenin signaling may provide valuable clinical targets for cancer therapy. In the current study, we demonstrated that upregulation of miR-744 in pancreatic cancer promoted Wnt/β-catenin signaling by directly targeting secreted frizzled-related protein 1 (SFRP1), glycogen synthase kinase 3β (GSK3β), and transducin-like enhancer of split 3 (TLE3), important negative modulators of Wnt/β-catenin signaling. Expression of miR-744 was markedly upregulated in pancreatic cancer and positively correlated with poor patient survival. Furthermore, we found that overexpressing miR-744 enhanced, while inhibiting miR-744 reduced, the stem cell-like phenotype of pancreatic cancer cells in vitro. Importantly, in vivo model of human-derived pancreatic xenografts showed that miR-744 upregulation enhanced the tumorigenicity of pancreatic cancer cells. These findings suggest that miR-744 plays a vital role in promoting the stem cell-like phenotype of pancreatic cancer cells, and may represent a novel prognostic biomarker and therapeutic target.

Limbal epithelial stem-microenvironmental alteration leads to pterygium development

Maintenance of tissue homeostasis relies on the accurate regulation of tissue specific stem cell activity which is governed by the dynamic interaction between the positive and negative feedback modulating mechanism of stem cell microenvironmental niche. Alteration or deregulation of the "stem-microenvironmental networking" provokes disease development. Limbal epithelial stem cells (LESC) are the initiator hierarchy that maintains corneal integrity. Compartmentalization of LESC within the limbal vicinity provides an opportunity to understand the stem-microenvironmental relationship. The purpose of this study was to determine the microenvironmental alteration associated with LESCs fate in pterygium condition in comparison with healthy state. Clinical observations evaluated the ocular surface disorder with respect to corneal vascularization, tear film abnormality, and thickening of limbal area in pterygium patients. Structural alteration of limbal stem/progenitor cells and its neighboring niche components were observed using histology and scanning electron microscopy. Receptor overexpression of TGFβ-R1, EGF-R1, and IL6-Rα and alteration of IL2-Rα expression pointed toward aberration of "stem-microenvironmental networking" in the limbal vicinity during disease development. Increased cell proliferation index along with TERT, Cyclin-D1, and PCNA over-expression in limbal part of pterygium epithelial cells indicated increased cellular proliferation and disturbed homeostatic equilibrium. We postulate that pterygium is associated with limbal microenvironmental anomaly where the resident epithelial cells became hyperproliferative.

MicroRNA-296-5p (miR-296-5p) functions as a tumor suppressor in prostate cancer by directly targeting Pin1

Upregulation of Pin1 was shown to advance the functioning of several oncogenic pathways. It was recently shown that Pin1 is potentially an excellent prognostic marker and can also serve as a novel therapeutic target for prostate cancer. However, the molecular mechanism of Pin1 overexpression in prostate cancer is still unclear. In the present study, we showed that the mRNA expression levels of Pin1 were not correlated with Pin1 protein levels in prostate cell lines which indicated that Pin1 may be regulated at the post-transcriptional level. A key player in post-transcriptional regulation is represented by microRNAs (miRNAs) that negatively regulate expressions of protein-coding genes at the post-transcriptional level. A bioinformatics analysis revealed that miR-296-5p has a conserved binding site in the Pin1 3'-untranslated region (UTR). A luciferase reporter assay demonstrated that the seed region of miR-296-5p directly interacts with the 3'-UTR of Pin1 mRNA. Moreover, miR-296-5p expression was found to be inversely correlated with Pin1 expression in prostate cancer cell lines and prostate cancer tissues. Furthermore, restoration of miR-296-5p or the knockdown of Pin1 had the same effect on the inhibition of the ability of cell proliferation and anchorage-independent growth of prostate cancer cell lines. Our results support miR-296-5p playing a tumor-suppressive role by targeting Pin1 and implicate potential effects of miR-296-5p on the prognosis and clinical application to prostate cancer therapy.

MicroRNA expression profile of gastric cancer stem cells in the MKN-45 cancer cell line

MicroRNAs (miRNAs) play important roles in post-transcriptional gene silencing of target messenger RNAs, which are involved in virtually all biological processes. Previously, we have demonstrated that spheroid body-forming cells from the MKN-45 cancer cell line possessed gastric cancer stem cell (CSC) properties. In this study, we aimed to determine the miRNA profile of the gastric CSCs and to explore the role of miRNAs in gastric CSCs. Human miRNA microarrays, which contain probes specific for 1887 human miRNAs were used to determine the expression profiles of the gastric CSCs. A total of 182 miRNAs with a more than 2-fold change were identified to be differentially expressed between the spheroid body-forming cells and the parental cells. Of these miRNAs, 9 miRNAs were over-expressed in the spheroid body-forming cells, while the other 173 miRNAs were all under-expressed, indicating that the role of most miRNAs in human gastric CSCs may be tumor suppressors. The results of microarray analysis were validated by quantitative real-time polymerase chain reaction, and the consistence rate is 70% (7 out of 10). The target genes for the validated miRNAs were predicted by using three online software programs, miRanda, PicTar, and TargetScan. Most of the potential targets of the miRNAs were relevant to the regulation of actin cytoskeleton, focal adhesion, extracellular matrix-receptor interaction, and the pathways in cancer. Especially, several genes are associated with some pivotal signaling pathways of the 'stem cell genes'. Evaluating the characteristic miRNAs of the gastric CSCs may be a new method for studying gastric cancer and developing therapeutic strategies, which aimed at eradicating the subpopulation of CSCs in gastric cancer.

Priming adult stem cells by hypoxic pretreatments for applications in regenerative medicine

The efficiency of regenerative medicine can be ameliorated by improving the biological performances of stem cells before their transplantation. Several ex-vivo protocols of non-damaging cell hypoxia have been demonstrated to significantly increase survival, proliferation and post-engraftment differentiation potential of stem cells. The best results for priming cultured stem cells against a following, otherwise lethal, ischemic stress have been obtained with brief intermittent episodes of hypoxia, or anoxia, and reoxygenation in accordance with the extraordinary protection afforded by the conventional maneuver of ischemic preconditioning in severely ischemic organs. These protocols of hypoxic preconditioning can be rather easily reproduced in a laboratory; however, more suitable pharmacological interventions inducing stem cell responses similar to those activated in hypoxia are considered among the most promising solutions for future applications in cell therapy. Here we want to offer an up-to-date review of the molecular mechanisms translating hypoxia into beneficial events for regenerative medicine. To this aim the involvement of epigenetic modifications, microRNAs, and oxidative stress, mainly activated by hypoxia inducible factors, will be discussed. Stem cell adaptation to their natural hypoxic microenvironments (niche) in healthy and neoplastic tissues will be also considered.

MicroRNA-185 and 342 inhibit tumorigenicity and induce apoptosis through blockade of the SREBP metabolic pathway in prostate cancer cells

MicroRNA (miRNA or miR) inhibition of oncogenic related pathways has been shown to be a promising therapeutic approach for cancer. Aberrant lipid and cholesterol metabolism is involved in prostate cancer development and progression to end-stage disease. We recently demonstrated that a key transcription factor for lipogenesis, sterol regulatory element-binding protein-1 (SREBP-1), induced fatty acid and lipid accumulation and androgen receptor (AR) transcriptional activity, and also promoted prostate cancer cell growth and castration resistance. SREBP-1 was overexpressed in human prostate cancer and castration-resistant patient specimens. These experimental and clinical results indicate that SREBP-1 is a potential oncogenic transcription factor in prostate cancer. In this study, we identified two miRNAs, miR-185 and 342, that control lipogenesis and cholesterogenesis in prostate cancer cells by inhibiting SREBP-1 and 2 expression and down-regulating their targeted genes, including fatty acid synthase (FASN) and 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR). Both miR-185 and 342 inhibited tumorigenicity, cell growth, migration and invasion in prostate cancer cell culture and xenograft models coincident with their blockade of lipogenesis and cholesterogenesis. Intrinsic miR-185 and 342 expression was significantly decreased in prostate cancer cells compared to non-cancerous epithelial cells. Restoration of miR-185 and 342 led to caspase-dependent apoptotic death in prostate cancer cells. The newly identified miRNAs, miR-185 and 342, represent a novel targeting mechanism for prostate cancer therapy.

MicroRNA expression profiling identifies miR-328 regulates cancer stem cell-like SP cells in colorectal cancer

Background:

Side population (SP) cells and their relationship to stem cell-like properties have been insufficiently studied in colorectal cancer (CRC). MicroRNAs (miRNAs) have attracted much attention but their roles in the maintenance of SP phenotype remain unclear.

Methods:

The SPs from CRC cell lines and primary cell cultures were analysed for stem cell-like properties. MiRNA microarray analysis identified miR-328 as a potential stemness miRNA of SP phenotype. The level of miR-328 expression in clinical samples and its correlation with SP fraction were determined. Gain-of-function and loss-of-function studies were performed to examine its roles in cancer stem-like SP cells. Furthermore, bioinformatics prediction and experimental validation were used to identify miR-328 target genes.

Results:

The SP cells sorted from CRC possess cancer stem cell (CSC)-like properties, including self-renewal, differentiation, resistance to chemotherapy, invasive and strong tumour formation ability. MiR-328 expression was significantly reduced in SP cells compared with Non-SP cells (P<0.05). Moreover, miR-328 expression was downregulated in CRC (n=33, P<0.05) and low miR-328 expression tend to correlate with high SP fraction (n=15, r=0.6559, P<0.05, Pearson's correlation). Functional studies indicated that miR-328 expression affects the number of SP cells. In addition, miR-328 overexpression reversed drug resistance and inhibited cell invasion of SP cells. Furthermore, luciferase reporter assay demonstrated that miR-328 directly targets ABCG2 and MMP16 and affects the levels of mRNA and protein expression in SP cells.

Conclusion:

These findings indicate that CRC contain cancer stem-like SP cells. MiR-328 has an important role in maintaining cancer stem-like SP phenotype that may be a potential target for effective CRC therapy.

The role of upregulated miRNAs and the identification of novel mRNA targets in prostatospheres

TICs are characterized by their ability to self-renew, differentiate and initiate tumor formation. miRNAs are small noncoding RNAs that bind to mRNAs resulting in regulation of gene expression and biological functions. The role of miRNAs and TICs in cancer progression led us to hypothesize that miRNAs may regulate genes involved in TIC maintenance. Using whole genome miRNA and mRNA expression profiling of TICs from primary prostate cancer cells, we identified a set of up-regulated miRNAs and a set of genes down-regulated in PSs. Inhibition of these miRNAs results in a decrease of prostatosphere formation and an increase in target gene expression. This study uses genome-wide miRNA profiling to analyze expression in TICs. We connect aberrant miRNA expression and deregulated gene expression in TICs. These findings can contribute to a better understanding of the molecular mechanisms governing TIC development/maintenance and the role that miRNAs have in the fundamental biology of TICs.

The 'real world' utility of miRNA patents: lessons learned from expressed sequence tags

Strategies are needed for drafting miRNA patent applications, in light of the existing patent landscape and genomic patent strategies of the past decades.

Skeletal myoblasts for cardiac repair

Stem cells provide an alternative curative intervention for the infarcted heart by compensating for the cardiomyocyte loss subsequent to myocardial injury. The presence of resident stem and progenitor cell populations in the heart, and nuclear reprogramming of somatic cells with genetic induction of pluripotency markers are the emerging new developments in stem cell-based regenerative medicine. However, until safety and feasibility of these cells are established by extensive experimentation in in vitro and in vivo experimental models, skeletal muscle-derived myoblasts, and bone marrow cells remain the most well-studied donor cell types for myocardial regeneration and repair. This article provides a critical review of skeletal myoblasts as donor cells for transplantation in the light of published experimental and clinical data, and indepth discussion of the advantages and disadvantages of skeletal myoblast-based therapeutic intervention for augmentation of myocardial function in the infarcted heart. Furthermore, strategies to overcome the problems of arrhythmogenicity and failure of the transplanted skeletal myoblasts to integrate with the host cardiomyocytes are discussed.