The role of miR-200a in mammalian epithelial cell transformation

Impact of rs2107425 Polymorphism and Expression of lncH19 and miR-200a on the Susceptibility of Colorectal Cancer

Cancer is the most common leading cause of mortality, making it a critical public health issue worldwide. Environmental and genetic abnormalities play a role in carcinogenesis, characterized by single nucleotide polymorphisms (SNPs) and abnormal gene expression. Also, non-coding RNA is a hot spot in cancer growth and metastasis. This study aimed to demonstrate the contribution of LncRNA H-19 rs2107425 to colorectal cancer (CRC) susceptibility and the correlation between miR-200a and LncRNA H-19 in patients with CRC. The current study was conducted on 100 participants, divided into 70 subjects with colorectal cancer and 30 age- and sex-matched healthy subjects. Patients with CRC experienced a significant elevation in WBC count, platelets, ALT, AST, and CEA. However, hemoglobin and albumin notably declined in patients with CRC compared with those in healthy controls. The expression of LncRNA H-19 and miR-200a increased in patients with CRC with a significant difference compared to healthy controls. Moreover, LncRNA H-19 and miR-200a expression significantly increased in stage III CRC compared to stage II CRC. As compared to carriers with the homozygous CC genotype, the frequency of rs2107425 CT and rs2107425 TT increased in patients with CRC. Our results indicate that the rs2107425 SNP of LncRNA H-19 may serve as a novel susceptibility marker for colorectal cancer. Moreover, miR-200a and LncRNA H-19 are prospective biomarkers of colorectal cancer.

Crosstalk between miRNAs and DNA Methylation in Cancer

miRNAs are some of the most well-characterized regulators of gene expression. Integral to several physiological processes, their aberrant expression often drives the pathogenesis of both benign and malignant diseases. Similarly, DNA methylation represents an epigenetic modification influencing transcription and playing a critical role in silencing numerous genes. The silencing of tumor suppressor genes through DNA methylation has been reported in many types of cancer and is associated with tumor development and progression. A growing body of literature has described the crosstalk between DNA methylation and miRNAs as an additional layer in the regulation of gene expression. Methylation in miRNA promoter regions inhibits its transcription, while miRNAs can target transcripts and subsequently regulate the proteins responsible for DNA methylation. Such relationships between miRNA and DNA methylation serve an important regulatory role in several tumor types and highlight a novel avenue for potential therapeutic targets. In this review, we discuss the crosstalk between DNA methylation and miRNA expression in the pathogenesis of cancer and describe how miRNAs influence DNA methylation and, conversely, how methylation impacts the expression of miRNAs. Finally, we address how these epigenetic modifications may be leveraged as biomarkers in cancer.

The regulatory role of pivotal microRNAs in the AKT signaling pathway in breast cancer

Breast cancer is the most prevalent type of cancer among women, and it remains the main challenge despite improved treatments. MicroRNAs (miRNAs) are a small non-coding family of RNAs that play an indispensable role in regulating major physiological processes, including differentiation, proliferation, invasion, migration, cell cycle regulation, stem cell maintenance, apoptosis, and organ development. The dysregulation of these tiny molecules is associated with various human malignancies. More than 50% of these non-coding RNA sequences estimated have been placed on genomic regions or fragile sites linked to cancer. Following the discovery of the first signatures of specific miRNA in breast cancer, numerous researches focused on involving these tiny RNAs in breast cancer physiopathology as a new therapeutic approach or as reliable prognostic biomarkers. In the current review, we focus on recent findings related to the involvement of miRNAs in breast cancer via the AKT signaling pathway and the related clinical implications.

Combined analysis of miR-200 family and its significance for breast cancer

While the molecular functions of miR-200 family have been deeply investigated, a role for these miRNAs as breast cancer biomarkers remains largely unexplored. In the attempt to clarify this, we profiled the miR-200 family members expression in a large cohort of breast cancer cases with a long follow-up (H-CSS cohort) and in TCGA-BRCA cohort. Overall, miR-200 family was found upregulated in breast tumors with respect to normal breast tissues while downregulated in more aggressive breast cancer molecular subtypes (i.e. Luminal B, HER2 and triple negative), consistently with their function as repressors of the epithelial-to-mesenchymal transition (EMT). In particular miR-141-3p was found differentially expressed in breast cancer molecular subtypes in both H-CSS and TCGA-BRCA cohorts, and the combined analysis of all miR-200 family members demonstrated a slight predictive accuracy on H-CSS cancer specific survival at 12 years (survival c-statistic: 0.646; 95%CI 0.538–0.754).

TGF-β-SMAD-miR-520e axis regulates NSCLC metastasis through a TGFBR2-mediated negative-feedback loop

Transforming growth factor-β (TGF-β) pathway plays crucial roles during the carcinogenesis and metastasis. TGF-β receptor 2 (TGFBR2) is a key molecule for the regulation of TGF-β pathway and frequently downregulated or lost in several cancer types including non-small cell lung cancer (NSCLC), and TGF-β pathway is often regulated by negative-feedback mechanisms, but little is known about the mechanism of TGFBR2 downregulation in NSCLC. Here, we found that the expression of miR-520e is upregulated in metastatic tumor tissues compared with non-metastatic ones, and its expression is inversely correlated with that of TGFBR2 in clinical samples. We also discovered that TGF-β dramatically increased the expression of miR-520e, which targeted and downregulated TGFBR2, and the suppression of miR-520e significantly impaired TGF-β-induced TGFBR2 downregulation. Chromatin immunoprecipitation-PCR experiments further showed that miR-520e is transcriptionally induced by SMAD2/3 in response to TGF-β. Our findings reveal a novel negative-feedback mechanism in TGF-β signaling and the expression level of miR-520e could be a predictive biomarker for NSCLC metastasis.

Overexpressed miR-200a promotes bladder cancer invasion through direct regulating Dicer/miR-16/JNK2/MMP-2 axis

Invasive bladder cancer (BC) is one of the most lethal malignant urological tumors. Although miR-200a has been reported as an onco-miRNA that targets the PTEN gene in endometrioid carcinoma, its biological significance in BC invasion has been poorly explored. In the current study, we found that miR-200a was markedly overexpressed in both human BC tissues and BBN-induced muscle-invasive BC tissues. We further showed that miR-200a overexpression specifically promoted human BC cell invasion, but not migration, via transcriptional upregulation of matrix metalloproteinase (MMP)-2. Mechanistic studies indicated that the increased phosphorylation of c-Jun mediated the increasing levels of MMP-2 mRNA transcription. Further investigation revealed that Dicer was decreased in miR-200a overexpressed BC cells; this resulted in inhibition of miR-16 maturation and consequently led to increased JNK2 protein translation and c-Jun activation. Taken together, the studies here showed that miR-200a overexpression inhibited Dicer expression, in turn, resulted in inhibition of miR-16 maturation, leading to upregulation of JNK2 expression, c-Jun phosphorylation, MMP-2 transcription and, ultimately, BC invasion. Collectively, these results demonstrate that miR-200a is an onco-miRNA that is a positive regulator for BC invasion. This finding could be very useful in the ongoing development of new strategies to treat invasive BC patients.

miR-331-3p functions as an oncogene by targeting ST7L in pancreatic cancer

Pancreatic cancer (PC) is a highly invasive tumor with early metastasis and poor prognosis, yet the mechanisms for tumor progression have not been fully elucidated. Emerging evidence indicates that microRNA-331-3p (miR-331-3p) plays an important role in the progression of diverse human cancers. Here, we found that miR-331-3p was significantly upregulated in tumor specimens of PC patients and PC cell lines. Functional studies showed that downregulation of miR-331-3p inhibited PC cell proliferation and epithelial-mesenchymal transition (EMT)-mediated metastasis in vitro. Furthermore, suppression of tumorigenicity 7 like (ST7L) was identified as a novel target gene of miR-331-3p. Tumor promotion effects of miR-331-3p were partially reversed by ST7L re-expression. In addition, miR-331-3p antagomir suppressed PC tumor growth and metastasis via upregulation of ST7L in xenograft mice. In summary, these results demonstrate that miR-331-3p is a tumor-promoting microRNA (miRNA) in PC cells and a promising biomarker for PC.

MicroRNA-106b-5p promotes hepatocellular carcinoma development via modulating FOG2

Background: A recent study has revealed that miR-106b-5p might promote hepatocellular carcinoma (HCC) stemness maintenance and metastasis by targeting PTEN via PI3K/Akt pathway based on HCC cell lines and animal models. Its clinical relevance remains unknown.

Purpose: Herein, we aimed to evaluate associations of miR-106b-5p dysregulation with various clinicopathological features of HCC patients and investigate its functions during HCC progression.

Patients and methods: At first, miR-106b-5p expression in 130 pairs of HCC and adjacent normal liver tissues was detected by quantitative PCR. Chi-square test was then performed to determine clinical significance. Further investigations on its functions were performed by miRNA target prediction and validation, as well as cellular experiments.

Results: miR-106b-5p levels in HCC tissues were significantly higher than those in the adjacent normal liver tissues (P<0.001). High miR-106b-5p expression was significantly associated with advanced tumor stage (P=0.02) and high tumor grade (P=0.03). In addition, Friend of GATA 2 (FOG2) was identified as a direct target of miR-106b-5p in HCC cells. Moreover, the clinical relevance to HCC progression of the combined high miR-106b-5p and low FOG2 expression was more significant than high miR-106b-5p alone. Functionally, enforced expression of miR-106b-5p reduced FOG2 expression and promoted the proliferation and invasion of HCC cells. Furthermore, co-transfection of FOG2 restored the oncogenic roles of miR-106b-5p over-expression.

Conclusion: Our data offer the convincing evidence that miR-106b-5p upregulation may promote the aggressive progression of HCC. miR-106b-5p overexpression may promote HCC cell proliferation and invasion by suppressing FOG2, implying its potentials as a promising therapeutic target for HCC patients.

"Beige" Cross Talk Between the Immune System and Metabolism

With thymic senescence the epithelial network shrinks to be replaced by adipose tissue. Transcription factor TBX-1 controls thymus organogenesis, however, the same TBX-1 has also been reported to orchestrate beige adipose tissue development. Given these different roles of TBX-1, we have assessed if thymic TBX-1 expression persists and demonstrates this dualism during adulthood. We have also checked whether thymic adipose involution could yield beige adipose tissue. We have used adult mouse and human thymus tissue from various ages to evaluate the kinetics of TBX-1 expression, as well as mouse (TEP1) and human (1889c) thymic epithelial cells (TECs) for our studies. Electron micrographs show multi-locular lipid deposits typical of beige adipose cells. Histology staining shows the accumulation of neutral lipid deposits. qPCR measurements show persistent and/or elevating levels of beige-specific and beige-indicative markers (TBX-1, EAR-2, UCP-1, PPAR-gamma). We have performed miRNome profiling using qPCR-based QuantStudio platform and amplification-free NanoString platform. We have observed characteristic alterations, including increased miR21 level (promoting adipose tissue development) and decreased miR34a level (bias toward beige adipose tissue differentiation). Finally, using the Seahorse metabolic platform we have recorded a metabolic profile (OCR/ECAR ratio) indicative of beige adipose tissue. In summary, our results support that thymic adipose tissue emerging with senescence is bona fide beige adipose tissue. Our data show how the borders blur between a key immune tissue (the thymus) and a key metabolic tissue (beige adipose tissue) with senescence. Our work contributes to the understanding of cross talk between the immune system and metabolism.

Potential Contributions of miR-200a/-200b and Their Target Gene-Leptin to the Sexual Size Dimorphism in Yellow Catfish

Sexual size dimorphism is the consequence of differential expression of sex-biased genes related to feeding and growth. Leptin is known to regulate energy balance by regulating food intake. In order to investigate the molecular mechanism of sexual size dimorphism in yellow catfish (Pelteobagrus fulvidraco), the expression of leptin (lep) and its functional receptor (lepr) were detected during larval development. Both lep and lepr have lower expression in males than in females during 1–4 weeks post hatching. 17a-Methyltestosterone (MT) treatment resulted in decreased expression of lep and lepr in both male and female larval fish. Interestingly, the mRNA levels of lep and lepr in juvenile male were significantly decreased compared with juvenile female during short-term fasting periods. Lep was predicted to be a potential target of miR-200a and miR-200b that had an opposite expression pattern to lep in male and female larvas. The results of luciferase reporter assay suggested that lep is a target of miR-200a/-200b. Subsequently, male hormone and fasting treatment have opposite effects on the expression of miR-200a/-200b and lep between males and females. In summary, our results suggest that sexual size dimorphism in fish species is probably caused by the sexually dimorphic expression of leptin, which could be negatively regulated by miR-200a/-200b.

Cellular and extracellular vesicular origins of miRNAs within the bovine ovarian follicle

The ovarian follicle components must provide an ideal environment to ensure the success of reproductive processes, and communication between follicular cells is crucial to support proper oocyte growth. Recently, it has been demonstrated that the presence of extracellular vesicles (EVs) carrying microRNAs (miRNAs) in follicular fluid represents an important autocrine and paracrine communication mechanism inside the ovarian follicle. In this study, we tested the hypothesis that the miRNA content of EVs isolated from ovarian follicular (granulosa and cumulus-oocyte complexes) cell-conditioned culture media is dependent upon cell type. We initially screened bovine granulosa cells (GCs) and cumulus-oocyte complexes (COCs), as well as their derived EVs for 348 miRNAs using real-time PCR, and detected 326 miRNAs in GCs and COCs cells and 62 miRNAs in GCs and COCs EVs. A bioinformatics analysis of the identified cell-specific and differentially expressed miRNAs predicted that they likely modulate important cellular processes, including signalling pathways such as the PI3K-Akt, MAPK and Wnt pathways. By investigating the origins of miRNAs within the follicular fluid, the results of this study provide novel insights into follicular miRNA content and intercellular communication that may be of invaluable use in the context of reproductive technologies, diagnostic of ovarian-related diseases and/or the identification of biomarkers for oocyte and embryo quality.

microRNA-200a-3p increases 5-fluorouracil resistance by regulating dual specificity phosphatase 6 expression

Acquisition of resistance to anti-cancer drugs is a significant obstacle to effective cancer treatment. Although several efforts have been made to overcome drug resistance in cancer cells, the detailed mechanisms have not been fully elucidated. Here, we investigated whether microRNAs (miRNAs) function as pivotal regulators in the acquisition of anti-cancer drug resistance to 5-fluorouracil (5-FU). A survey using a lentivirus library containing 572 precursor miRNAs revealed that five miRNAs promoted cell survival after 5-FU treatment in human hepatocellular carcinoma Hep3B cells. Among the five different clones, the clone expressing miR-200a-3p (Hep3B-miR-200a-3p) was further characterized as a 5-FU-resistant cell line. The cell viability and growth rate of Hep3B-miR-200a-3p cells were higher than those of control cells after 5-FU treatment. Ectopic expression of a miR-200a-3p mimic increased, while inhibition of miR-200a-3p downregulated, cell viability in response to 5-FU, doxorubicin, and CDDP (cisplatin). We also showed that dual-specificity phosphatase 6 (DUSP6) is a novel target of miR-200a-3p and regulates resistance to 5-FU. Ectopic expression of DUSP6 mitigated the pro-survival effects of miR-200a-3p. Taken together, these results lead us to propose that miR-200a-3p enhances anti-cancer drug resistance by decreasing DUSP6 expression.

MicroRNA-200c binding to FN1 suppresses the proliferation, migration and invasion of gastric cancer cells

We aimed to investigate the effects of miR-200c binding to fibronectin 1 (FN1) on proliferation, migration and invasion of gastric cancer (GC) cells. A total of 52 GC tissues and their corresponding normal adjacent tissue samples were collected. Then, miR-200c and FN1 were tested using quantitative real-time RT-PCR in the clinical specimens and GC cells, while immunohistochemistry and western blotting assay were carried out to detect FN1 expressions. Dual luciferase reporter gene assay was used to assess the effect of miR-200c on the luciferase activity of FN1 3'UTR. BGC-823 cells were transfected with miR-200c mimics, miR-200c inhibitors and FN1 siRNA, respectively. The effects of miR-200c inhibitors and FN1 siRNA on cellular proliferation, migration and invasion were detected through MTT assay and Transwell assay. Compared to normal tissues and cells, miR-200c was significantly down-regulated and FN1 was significantly up-regulated (P<0.01). Dual luciferase reporter gene assay showed that miR-200c could specifically bind to the 3'-UTR of FN1 and significantly repress the luciferase activity (P<0.01). Both mRNA and protein expressions of FN1 were decreased significantly in GC cells when miR-200c was over expressed. The proliferation, migration and invasion of GC cells could be suppressed by over-expression of miR-200c or down-regulation of FN1. In conclusion, miR-200c was significantly down-regulated in both GC tissues and cell lines, while FN1 presented the opposite trends. Besides, miR-200c inhibited the proliferation, migration and invasion of GC cells through binding to FN1.

MicroRNA analysis of breast ductal fluid in breast cancer patients

Recent studies suggest that microRNAs show promise as excellent biomarkers for breast cancer; however there is still a high degree of variability between studies making the findings difficult to interpret. In addition to blood, ductal lavage (DL) and nipple aspirate fluids represent an excellent opportunity for biomarker detection because they can be obtained in a less invasive manner than biopsies and circumvent the limitations of evaluating blood biomarkers with regards to tissue of origin specificity. In this study, we have investigated for the first time, through a real-time PCR array, the expression of 742 miRNAs in the ductal lavage fluid collected from 22 women with unilateral breast tumors. We identified 17 differentially expressed miRNAs between tumor and paired normal samples from patients with ductal breast carcinoma. Most of these miRNAs have various roles in breast cancer tumorigenesis, invasion and metastasis, therapeutic response, or are associated with several clinical and pathological characteristics of breast tumors. Moreover, some miRNAs were also detected in other biological fluids of breast cancer patients such as serum (miR-23b, -133b, -181a, 338-3p, -625), plasma (miR-200a), and breast milk (miR-181a). A systems biology analysis of these differentially expressed miRNAs points out possible pathways and cellular processes previously described as having an important role in breast cancer such as Wnt, ErbB, MAPK, TGF-β, mTOR, PI3K-Akt, p53 signaling pathways. We also observed a difference in the miRNA expression with respect to the histological type of the tumors. In conclusion, our findings suggest that miRNA analysis of breast ductal fluid is feasible and potentially very useful for the detection of breast cancer.

Thymosin beta 4 up-regulates miR-200a expression and induces differentiation and survival of rat brain progenitor cells

Thymosin beta 4 (Tβ4), a secreted 43 amino acid peptide, promotes oligodendrogenesis, and improves neurological outcome in rat models of neurologic injury. We demonstrated that exogenous Tβ4 treatment up-regulated the expression of the miR-200a in vitro in rat brain progenitor cells and in vivo in the peri-infarct area of rats subjected to middle cerebral artery occlusion (MCAO). The up-regulation of miR-200a down-regulated the expression of the following targets in vitro and in vivo models: (i) growth factor receptor-bound protein 2 (Grb2), an adaptor protein involved in epidermal growth factor receptor (EGFR)/Grb2/Ras/MEK/ERK1/c-Jun signaling pathway, which negatively regulates the expression of myelin basic protein (MBP), a marker of mature oligodendrocyte; (ii) ERRFI-1/Mig-6, an endogenous potent kinase inhibitor of EGFR, which resulted in activation/phosphorylation of EGFR; (iii) friend of GATA 2, and phosphatase and tensin homolog deleted in chromosome 10 (PTEN), which are potent inhibitors of the phosphatidylinositol-3-kinase (PI3K)/AKT signaling pathway, and resulted in marked activation of AKT; and (iv) transcription factor, p53, which induces pro-apoptotic genes, and possibly reduced apoptosis of the progenitor cells subjected to oxygen glucose deprivation (OGD). Anti-miR-200a transfection reversed all the effects of Tβ4 treatment in vitro. Thus, Tβ4 up-regulated MBP synthesis, and inhibited OGD-induced apoptosis in a novel miR-200a dependent EGFR signaling pathway. Our findings of miR-200a-mediated protection of progenitor cells may provide a new therapeutic importance for the treatment of neurologic injury. Tβ4-induced micro-RNA-200a (miR-200a) regulates EGFR signaling pathways for MBP synthesis and apoptosis: up-regulation of miR-200a after Tβ4 treatment, increases MBP synthesis after targeting Grb2 and thereby inactivating c-Jun from inhibition of MBP synthesis; and also inhibits OGD-mediated apoptosis after targeting EGFR inhibitor (Mig-6), PI3K inhibitors (FOG2 and Pten) and an inducer (p53) of pro-apoptotic genes, for AKT activation and down-regulation of p53. These findings may contribute the therapeutic benefits for stroke and other neuronal diseases associated with demyelination disorders.

A feedback regulatory loop involving p53/miR-200 and growth hormone endocrine axis controls embryo size of zebrafish

In vertebrates, growth hormone/insulin-like growth factor (GH/IGF) axis signaling plays a critical role in regulating somatic growth. Understanding the direct upstream regulators of GH/IGF axis remains a major challenge. Our studies of the zebrafish reveal that the conserved miR-200 family members are critical regulators of embryo size by targeting several GH/IGF axis genes, including GH, GHRa, GHRb and IGF2a. Overexpression of miR-200s led to cell cycle arrest in the G1 phase and induced apoptotic responses during embryo development, thereby inhibiting somatic growth of zebrafish embryos. Intriguingly, GH induced expression of both p53 and miR-200s, and miR-200s is a potential p53 transcriptional target, thus forming a negative feedback loop. Significantly, the up-regulation of miR-200s associated with GH activation is abolished in embryos with p53 mutation. By integrating these studies, we conclude that p53/miR-200 and GH/IGF signaling pathway form a negative regulatory loop to control embryo size, that provide critical insights into the long-standing puzzle of how body growth is determined during early development of teleosts.

Roles for miRNAs in endocrine resistance in breast cancer

Therapies targeting estrogen receptor alpha (ERα), including selective ER modulators such as tamoxifen, selective ER downregulators such as fulvestrant (ICI 182 780), and aromatase inhibitors such as letrozole, are successfully used in treating breast cancer patients whose initial tumor expresses ERα. Unfortunately, the effectiveness of endocrine therapies is limited by acquired resistance. The role of microRNAs (miRNAs) in the progression of endocrine-resistant breast cancer is of keen interest in developing biomarkers and therapies to counter metastatic disease. This review focuses on miRNAs implicated as disruptors of antiestrogen therapies, their bona fide gene targets and associated pathways promoting endocrine resistance.

MicroRNA-200 promotes lung cancer cell growth through FOG2-independent AKT activation

MicroRNA-200 (miR-200) has emerged as a regulator of the PI3K/AKT pathway and cancer cell growth. It was reported that miR-200 can activate PI3K/AKT by targeting FOG2 (friend of GATA 2), which directly binds to the p85α regulatory subunit of PI3K. We found that miR-200 was elevated in early stage lung adenocarcinomas when compared with normal lung tissues, and the expression of miR-200 promoted the tumor spheroid growth of lung adenocarcinoma cells. We show that AKT activation was essential for such oncogenic action of miR-200. However, depletion of FOG2 had little effect on AKT activation. By performing a reverse-phase protein array, we found that miR-200 not only activated AKT but also concomitantly inactivated S6K and increased IRS-1, an S6K substrate that is increased on S6K inactivation. Depletion of IRS-1 partially inhibited the miR-200-dependent AKT activation. Taken together, our results suggest that miR-200 may activate AKT in lung adenocarcinoma cells through a FOG2-independent mechanism involving IRS-1. Our findings also provide evidence that increased miR-200 expression may contribute to early lung tumorigenesis and that AKT inhibitors may be useful for the treatment of miR-200-dependent tumor cell growth.

Tumor suppressive microRNA-200a inhibits renal cell carcinoma development by directly targeting TGFB2

A large body of evidence indicates that microRNAs play a critical role in tumor initiation and progression by negatively regulating oncogenes or tumor suppressor genes. Here, we report that the expression of miR-200a was notably downregulated in 45 renal cell carcinoma (RCC) samples. Restoration of miR-200a suppressed cell proliferation, migration, and invasion in two RCC cell lines. Furthermore, we used an epithelial-to-mesenchymal transition PCR array to explore the putative target genes of miR-200a. By performing quantitative real-time PCR, ELISA, and luciferase reporter assays, transforming growth factor beta2 (TGFB2) was validated as a direct target gene of miR-200a. Moreover, siRNA-mediated knockdown of TGFB2 partially phenocopied the effect of miR-200a overexpression. These results suggest that miR-200a suppresses RCC development via directly targeting TGFB2, indicating that miR-200a may present a novel target for diagnostic and therapeutic strategies in RCC.