Estrogen receptor α signaling regulates breast tumor-initiating cells by down-regulating miR-140 which targets the transcription factor SOX2

A High-Fat Diet Promotes Mammary Gland Myofibroblast Differentiation through MicroRNA 140 Downregulation

Human breast adipose tissue is a heterogeneous cell population consisting of mature white adipocytes, multipotent mesenchymal stem cells, committed progenitor cells, fibroblasts, endothelial cells, and immune cells. Dependent on external stimulation, adipose-derived stem cells differentiate along diverse lineages into adipocytes, chondrocytes, osteoblasts, fibroblasts, and myofibroblasts. It is currently not fully understood how a high-fat diet reprograms adipose-derived stem cells into myofibroblasts. In our study, we used mouse models of a regular diet and of high-fat-diet-induced obesity to investigate the role of dietary fat on myofibroblast differentiation in the mammary stromal microenvironment. We found that a high-fat diet promotes myofibroblast differentiation by decreasing microRNA 140 (miR-140) expression in mammary adipose tissue through a novel negative-feedback loop. Increased transforming growth factor β1 (TGF-β1) in mammary adipose tissue in obese mice activates SMAD3 signaling, causing phospho-SMAD3 to bind to the miR-140 locus and inhibit miR-140 transcription. This prevents miR-140 from targeting SMAD3 for degradation, resulting in amplified TGF-β1/SMAD3 signaling and miR-140 downregulation-dependent myofibroblast differentiation. Using tissue and coculture models, we found that myofibroblasts and the fibrotic microenvironment created by myofibroblasts impact the stemness and proliferation of normal ductal epithelial cells and early-stage breast cancer invasion and stemness.

microRNAs regulate TAL1 expression in T-cell acute lymphoblastic leukemia

The transcription factor TAL1 is a proto-oncogene whose aberrant expression in committed T-cell precursors is associated with the development of T-cell acute lymphoblastic leukemia (T-ALL). The mechanisms leading to aberrant activation of TAL1 in T-ALL patients who lack chromosomal rearrangements involving the TAL1 locus remain largely unknown. We hypothesized that TAL1 levels decrease during normal T-cell development at least in part due to miRNA-dependent silencing, in which case TAL1 over-expression in some T-ALL cases could be the consequence of deregulated miRNA expression. By performing computational prediction of miRNAs that bind to the human TAL1 mRNA we compiled a list of miRNAs that are candidates to regulate TAL1. Using a luciferase reporter system and mutagenesis assays we confirmed the miRNA-TAL1 mRNA interactions and selected candidate miRNAs: miR-101, miR-520d-5p, miR-140-5p, miR-448 and miR-485-5p. Over-expression of these microRNAs in different T-ALL cell lines consistently resulted in the down-regulation of TAL1 protein. In accordance, inhibition of miR-101 and miR-520d-5p promoted TAL1 protein expression. Importantly, we found that miR-101, miR-140-5p, miR-448 and miR-485-5p were down-regulated in T-ALL patient specimens and T-ALL cell lines. Our results show for the first time the existence of epigenetic regulation of TAL1 by specific miRNAs which may contribute, at least in part, to the ectopic expression of TAL1 in some T-ALL cases.

microRNA -140-5p inhibits colorectal cancer invasion and metastasis by targeting ADAMTS5 and IGFBP5

Background

Colorectal cancer (CRC) is one of the most common malignancies in the world. microRNA-140-5p (miR-140) has been shown to be involved in cartilage development and osteoarthritis (OA) pathogenesis. Some contradictions still exist concerning the role of miR-140 in tumor progression and metastasis, and the underlying mechanism is uncertain.

Methods

Immunohistochemistry was performed to determine the expressions of ADAMTS5 and IGFBP5 in CRC tissues. Human CRC cell lines HCT116 and RKO were transfected with miR-140 mimic, inhibitor, or small interfering RNA (siRNA) against ADAMTS5 or IGFBP5, respectively, using oligofectamine or lipofectamine 2000. Scratch-wound assay and transwell migration and invasion assays were used to evaluate the effects of miR-140 on the capabilities of migration and invasion. The levels of miR-140 and ADAMTS5 and IGFBP5 mRNA were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Western blot was performed to examine the expression of ADAMTS5 and IGFBP5 proteins.

Results

miR-140 was significantly reduced, whereas ADAMTS5 and IGFBP5 were upregulated, in the human CRC tissues compared to the corresponding normal colorectal mucosa. miR-140 downregulation and ADAMTS5 or IGFBP5 overexpression were associated with the advanced TNM stage and distant metastasis of CRC. There was a reverse correlation between miR-140 levels and ADAMTS5 and IGFBP5 expression in CRC tissues. ADAMTS5 and IGFBP5 were downregulated by miR-140 at both the protein and mRNA levels in the CRC cell lines. The gain-of- and loss-of-function studies showed that miR-140 inhibited CRC cell migratory and invasive capacities at least partially via downregulating the expression of ADAMTS5 and IGFBP5.

Conclusions

These findings suggest that miR-140 suppresses CRC progression and metastasis, possibly through downregulating ADAMTS5 and IGFBP5. miR-140 might be a potential therapeutic candidate for the treatment of CRC.

Dysregulation of the BRCA1/long non-coding RNA NEAT1 signaling axis contributes to breast tumorigenesis

Dysregulation of long non-codng RNA (lncRNA) expression has been found to contribute to tumorigenesis. However, the roles of lncRNAs in BRCA1-related breast cancer remain largely unknown. In this study, we delineate the role of the novel BRCA1/lncRNA NEAT1 signaling axis in breast tumorigenesis. BRCA1 inhibits NEAT1 expression potentially through binding to its genomic binding site upstream of the NEAT1 gene. BRCA1 deficiency in human normal/cancerous breast cells and mouse mammary glands leads to NEAT1 overexpression. Our studies show that NEAT1 upregulation resulting from BRCA1 deficiency stimulates in vitro and in vivo breast tumorigenicity. We have further identified molecular mediators downstream of the BRCA1/NEAT1 axis. NEAT1 epigenetically silences miR-129-5p expression by promoting the DNA methylation of the CpG island in the miR-129 gene. Silencing of miR-129-5p expression by NEAT1 results in upregulation of WNT4 expression, a target of miR-129-5p, which leads to activation of oncogenic WNT signaling. Our functional studies indicate that this NEAT1/miR-129-5p/WNT4 axis contributes to the tumorigenic effects of BRCA1 deficiency. Finally our in silico expression correlation analysis suggests the existence of the BRCA1/NEAT1/miR-129-5p axis in breast cancer. Our findings, taken together, suggest that the dysregulation of the BRCA1/NEAT1/miR-129-5p/WNT4 signaling axis is involved in promoting breast tumorigenesis.

Crosstalk between the vitamin D receptor (VDR) and miR-214 in regulating SuFu, a hedgehog pathway inhibitor in breast cancer cells

The vitamin D receptor (VDR), and its ligand 1α,25-dihydroxyvitamin D₃ (1,25D₃) prevent breast cancer development and progression, yet the molecular mechanisms governing this are unclear. MicroRNAs (miRNAs) on the other hand, promote or inhibit breast cancer growth. To understand how VDR regulates miRNAs, we compared miRNA expression of wild-type (WT) and VDR knockout (VDRKO) breast cancer cells by a Mouse Breast Cancer miRNA PCR array. Compared to VDR WT cells, expressions of miR-214, miR-199a-3p and miR-199a-5p of the miR-199a/miR-214 cluster were 42, 15, and 10 fold higher in VDRKO cells respectively. Overexpression of VDR in breast cancer cells reduced the miR-199a/miR-214 cluster expression by 30%. VDR status also negatively correlated with Dnm3os expression, a non-coding RNA transcript of the dynamin-3 gene encoding the miR-199a/miR-214 cluster, suggesting that VDR represses this cluster through Dnm3os. Conversely, overexpression of miR-214 in MCF-7 and T47D cells antagonized VDR mediated signaling. Furthermore, there was a positive correlation between VDR status and the expression of Suppressor of fused gene (SuFu), a hedgehog pathway inhibitor. miR-214 on the other hand suppressed SuFu protein expression. These findings suggest a crosstalk between VDR and miR-214 in regulating hedgehog signaling in breast cancer cells, providing new therapies for breast cancer.

Information-dependent enrichment analysis reveals time-dependent transcriptional regulation of the estrogen pathway of toxicity

The twenty-first century vision for toxicology involves a transition away from high-dose animal studies to in vitro and computational models (NRC in Toxicity testing in the 21st century: a vision and a strategy, The National Academies Press, Washington, DC, 2007). This transition requires mapping pathways of toxicity by understanding how in vitro systems respond to chemical perturbation. Uncovering transcription factors/signaling networks responsible for gene expression patterns is essential for defining pathways of toxicity, and ultimately, for determining the chemical modes of action through which a toxicant acts. Traditionally, transcription factor identification is achieved via chromatin immunoprecipitation studies and summarized by calculating which transcription factors are statistically associated with up- and downregulated genes. These lists are commonly determined via statistical or fold-change cutoffs, a procedure that is sensitive to statistical power and may not be as useful for determining transcription factor associations. To move away from an arbitrary statistical or fold-change-based cutoff, we developed, in the context of the Mapping the Human Toxome project, an enrichment paradigm called information-dependent enrichment analysis (IDEA) to guide identification of the transcription factor network. We used a test case of activation in MCF-7 cells by 17β estradiol (E2). Using this new approach, we established a time course for transcriptional and functional responses to E2. ERα and ERβ were associated with short-term transcriptional changes in response to E2. Sustained exposure led to recruitment of additional transcription factors and alteration of cell cycle machinery. TFAP2C and SOX2 were the transcription factors most highly correlated with dose. E2F7, E2F1, and Foxm1, which are involved in cell proliferation, were enriched only at 24 h. IDEA should be useful for identifying candidate pathways of toxicity. IDEA outperforms gene set enrichment analysis (GSEA) and provides similar results to weighted gene correlation network analysis, a platform that helps to identify genes not annotated to pathways.

SOX-mediated molecular crosstalk during the progression of tumorigenesis

SOX family transcription factor has emerged as a double-edged sword relating to tumorigenesis and metastasis. Multiple studies have revealed different expression patterns and contradictory roles of SOX factors in the tumor initiation and progression. The aberrant expression of SOX factors is regulated by copy number alteration, methylation modulation, microRNAs, transcription factors and post-translational modification. This review summarizes the role of SOX factors in molecular interactions and signaling pathways during different steps of carcinogenesis, such as CSCs stemness maintenance, EMT occurrence, cell invasion, cell proliferation and apoptosis. The Wnt signaling pathway is also shown to provide vital intermediate signaling transduction. We believe that SOX family proteins may be used as prognostic markers for human clinical therapy, and novel therapy strategies targeting SOX factors should be explored in future clinical applications.

MicroRNA-140 Inhibits Cell Proliferation in Gastric Cancer Cell Line HGC-27 by Suppressing SOX4

BACKGROUND Gastric cancer is a malignant tumor with a high morbidity and mortality. MicroRNAs are important regulators of gene expression, influencing the progression of gastric cancer. This study aimed to reveal the role of microRNA-140 (miR-140) in gastric cancer cell proliferation and its potential mechanisms. MATERIAL AND METHODS Gastric cancer tissues and cell lines BGC-823, SGC-7901, and HGC-27 were used to analyze miR-140 levels compared to normal tissues and cell line GES-1. In HGC-27 cells transfected with miR-140 mimic, we performed MTT, colony formation assay, and cell cycle assay by flow cytometry. SOX4, a predicted target of miR-140, was mutated to verify its regulation by miR-140, and was overexpressed to analyze its function in cell proliferation. Doxorubicin treatment was performed to investigate the effect of miR-140 on drug resistance. RESULTS miR-140 was down-regulated in gastric cancer tissues and cell lines, with the lowest expression level in HGC-27. miR-140 overexpression inhibited HGC-27 cell viability and colony formation and resulted in G0/G1 arrest. miR-140 suppressed SOX4 expression via binding to the 3' untranslated region, while the mutant SOX4 could not be regulated. Overexpressing SOX4 led to promoted cell viability, colony formation, and cell cycle progress. miR-140 overexpression also improved the anti-viability effects of doxorubicin, suggesting its potential in reducing the drug resistance of gastric cells. CONCLUSIONS These findings suggest that miR-140 directly inhibits SOX4, which might be one of its mechanisms in suppressing gastric cancer cell proliferation. This study provides a promising therapeutic strategy for treating gastric cancer and facilitates microRNA research in various diseases.

Forkhead Box Q1 Is a Novel Target of Breast Cancer Stem Cell Inhibition by Diallyl Trisulfide

Diallyl trisulfide (DATS), a metabolic byproduct of garlic, is known to inhibit the growth of breast cancer cells in vitro and in vivo This study demonstrates that DATS targets breast cancer stem cells (bCSC). Exposure of MCF-7 and SUM159 human breast cancer cells to pharmacological concentrations of DATS (2.5 and 5 μm) resulted in dose-dependent inhibition of bCSC, as evidenced by a mammosphere assay and flow cytometric analysis of aldehyde dehydrogenase 1 (ALDH1) activity and the CD44(high)/CD24(low)/epithelial specific antigen-positive fraction. DATS-mediated inhibition of bCSC was associated with a decrease in the protein level of FoxQ1. Overexpression of FoxQ1 in MCF-7 and SUM159 cells increased ALDH1 activity and the CD49f(+)/CD24(-) fraction. Inhibition of ALDH1 activity and/or mammosphere formation upon DATS treatment was significantly attenuated by overexpression of FoxQ1. In agreement with these results, stable knockdown of FoxQ1 using small hairpin RNA augmented bCSC inhibition by DATS. Expression profiling for cancer stem cell-related genes suggested that FoxQ1 may negatively regulate the expression of Dachshund homolog 1 (DACH1), whose expression is lost in invasive breast cancer. Chromatin immunoprecipitation confirmed recruitment of FoxQ1 at the DACH1 promoter. Moreover, inducible expression of DACH1 augmented DATS-mediated inhibition of bCSC. Expression of FoxQ1 protein was significantly higher in triple-negative breast cancer cases compared with normal mammary tissues. Moreover, an inverse association was observed between FoxQ1 and DACH1 gene expression in breast cancer cell lines and tumors. DATS administration inhibited ALDH1 activity in vivo in SUM159 xenografts. These results indicate that FoxQ1 is a novel target of bCSC inhibition by DATS.

Sox2: regulation of expression and contribution to brain tumors

Tumors of the CNS are composed of a complex mixture of neoplastic cells, in addition to vascular, inflammatory and stromal components. Similar to most other tumors, brain tumors contain a heterogeneous population of cells that are found at different stages of differentiation. The cancer stem cell hypothesis suggests that all tumors are composed of subpopulation of cells with stem-like properties, which are capable of self-renewal, display resistance to therapy and lead to tumor recurrence. One of the most important transcription factors that regulate cancer stem cell properties is SOX2. In this review, we focus on SOX2 and the complex network of signaling molecules and transcription factors that regulate its expression and function in brain tumor initiating cells. We also highlight important findings in the literature about the role of SOX2 in glioblastoma and medulloblastoma, where it has been more extensively studied.

MicroRNA-140-5p and SMURF1 regulate pulmonary arterial hypertension

Loss of the growth-suppressive effects of bone morphogenetic protein (BMP) signaling has been demonstrated to promote pulmonary arterial endothelial cell dysfunction and induce pulmonary arterial smooth muscle cell (PASMC) proliferation, leading to the development of pulmonary arterial hypertension (PAH). MicroRNAs (miRs) mediate higher order regulation of cellular function through coordinated modulation of mRNA targets; however, miR expression is altered by disease development and drug therapy. Here, we examined treatment-naive patients and experimental models of PAH and identified a reduction in the levels of miR-140-5p. Inhibition of miR-140-5p promoted PASMC proliferation and migration in vitro. In rat models of PAH, nebulized delivery of miR-140-5p mimic prevented the development of PAH and attenuated the progression of established PAH. Network and pathway analysis identified SMAD-specific E3 ubiquitin protein ligase 1 (SMURF1) as a key miR-140-5p target and regulator of BMP signaling. Evaluation of human tissue revealed that SMURF1 is increased in patients with PAH. miR-140-5p mimic or SMURF1 knockdown in PASMCs altered BMP signaling, further supporting these factors as regulators of BMP signaling. Finally, Smurf1 deletion protected mice from PAH, demonstrating a critical role in disease development. Together, these studies identify both miR-140-5p and SMURF1 as key regulators of disease pathology and as potential therapeutic targets for the treatment of PAH.

Circadian disruption and breast cancer: an epigenetic link?

Breast cancer is already the most common malignancy affecting women worldwide, and evidence is mounting that breast cancer induced by circadian disruption (CD) is a warranted concern. Numerous studies have investigated various aspects of the circadian clock in relation to breast cancer, and evidence from these studies indicates that melatonin and the core clock genes can play a crucial role in breast cancer development. Even though epigenetics has been increasingly recognized as a key player in the etiology of breast cancer and linked to circadian rhythms, and there is evidence of overlap between epigenetic deregulation and breast cancer induced by circadian disruption, only a handful of studies have directly investigated the role of epigenetics in CD-induced breast cancer. This review explores the circadian clock and breast cancer, and the growing role of epigenetics in breast cancer development and circadian rhythms. We also summarize the current knowledge and next steps for the investigation of the epigenetic link in CD-induced breast cancer.

Sexual dimorphism in cancer

The incidence of many types of cancer arising in organs with non-reproductive functions is significantly higher in male populations than in female populations, with associated differences in survival. Occupational and/or behavioural factors are well-known underlying determinants. However, cellular and molecular differences between the two sexes are also likely to be important. In this Opinion article, we focus on the complex interplay that sex hormones and sex chromosomes can have in intrinsic control of cancer-initiating cell populations, the tumour microenvironment and systemic determinants of cancer development, such as the immune system and metabolism. A better appreciation of these differences between the two sexes could be of substantial value for cancer prevention as well as treatment.

Circulating microRNAs in follicular fluid, powerful tools to explore in vitro fertilization process

Circulating or “extracellular” microRNAs (miRNAs) detected in biological fluids, could be used as potential diagnostic and prognostic biomarkers of several disease, such as cancer, gynecological and pregnancy disorders. However, their contributions in female infertility and in vitro fertilization (IVF) remain unknown. This study investigated the expression profiles of five circulating miRNAs (let-7b, miR-29a, miR-30a, miR-140 and miR-320a) in human follicular fluid from 91 women with normal ovarian reserve and 30 with polycystic ovary syndrome (PCOS) and their ability to predict IVF outcomes. The combination of FF miR-30a, miR-140 and let-7b expression levels discriminated between PCOS and normal ovarian reserve with a specificity of 83.8% and a sensitivity of 70% (area under the ROC curve, AUC = 0.83 [0.73–0.92]; p < 0.0001). FF samples related to low number of mature oocytes (≤2) contained significant less miR-320a levels than those related to a number of mature oocytes >2 (p = 0.04). Moreover, FF let-7b predicted the development of expanded blastocysts with 70% sensitivity and 64.3% specificity (AUC = 0.67 [0.54–0.79]; p = 0.02) and FF miR-29a potential to predict clinical pregnancy outcome reached 0.68 [0.55–0.79] with a sensitivity of 83.3% and a specificity of 53.5% (p = 0.01). Therefore, these miRNAs could provide new helpful biomarkers to facilitate personalized medical care during IVF.

Non-coding RNAs in Mammary Gland Development and Disease

Non-coding RNAs (ncRNAs) are untranslated RNA molecules that function to regulate the expression of numerous genes and associated biochemical pathways and cellular functions. NcRNAs include small interfering RNAs (siRNAs), microRNAs (miRNAs), PIWI-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs) and long non-coding RNAs (lncRNAs). They participate in the regulation of all developmental processes and are frequently aberrantly expressed or functionally defective in disease. This Chapter will focus on the role of ncRNAs, in particular miRNAs and lncRNAs, in mammary gland development and disease.

MicroRNA 140 Promotes Expression of Long Noncoding RNA NEAT1 in Adipogenesis

More than 40% of the U.S. population are clinically obese and suffer from metabolic syndrome with an increased risk of postmenopausal estrogen receptor-positive breast cancer. Adipocytes are the primary component of adipose tissue and are formed through adipogenesis from precursor mesenchymal stem cells. While the major molecular pathways of adipogenesis are understood, little is known about the noncoding RNA signaling networks involved in adipogenesis. Using adipocyte-derived stem cells (ADSCs) isolated from wild-type and microRNA 140 (miR-140) knockout mice, we identify a novel miR-140/long noncoding RNA (lncRNA) NEAT1 signaling network necessary for adipogenesis. miR-140 knockout ADSCs have dramatically decreased adipogenic capabilities associated with downregulation of NEAT1 expression. We identified a miR-140 binding site in NEAT1 and found that mature miR-140 in the nucleus can physically interact with NEAT1, leading to increased NEAT1 expression. We demonstrated that reexpression of NEAT1 in miR-140 knockout ADSCs is sufficient to restore their ability to undergo differentiation. Our results reveal an exciting new noncoding RNA signaling network that regulates adipogenesis and that is a potential new target in the prevention or treatment of obesity.

miRNAs regulated by estrogens, tamoxifen, and endocrine disruptors and their downstream gene targets

MicroRNAs (miRNAs) are short (22 nucleotides), single-stranded, non-coding RNAs that form complimentary base-pairs with the 3' untranslated region of target mRNAs within the RNA-induced silencing complex (RISC) and block translation and/or stimulate mRNA transcript degradation. The non-coding miRBase (release 21, June 2014) reports that human genome contains ∼ 2588 mature miRNAs which regulate ∼ 60% of human protein-coding mRNAs. Dysregulation of miRNA expression has been implicated in estrogen-related diseases including breast cancer and endometrial cancer. The mechanism for estrogen regulation of miRNA expression and the role of estrogen-regulated miRNAs in normal homeostasis, reproduction, lactation, and in cancer is an area of great research and clinical interest. Estrogens regulate miRNA transcription through estrogen receptors α and β in a tissue-specific and cell-dependent manner. This review focuses primarily on the regulation of miRNA expression by ligand-activated ERs and their bona fide gene targets and includes miRNA regulation by tamoxifen and endocrine disrupting chemicals (EDCs) in breast cancer and cell lines.

Recurrence and metastasis of breast cancer is influenced by ovarian hormone's effect on breast cancer stem cells

Cancer stem cells (CSCs) have recently attracted great interest because of their emerging role in initiation, progression and metastasis, combined with their intrinsic resistance to chemotherapy and radiation therapy. CSCs and its interaction with hormones in breast cancer are currently being investigated with the aim of uncovering the molecular mechanisms by which they evade conventional treatment regimens. In this review, we discuss recent experimental data and new perspectives in the area of steroid hormones and their cross-talk with breast CSCs. We have covered literature associated with biomarkers, hormone receptors and hormone responsive signaling pathways in breast CSC. In addition, we also discuss the role of miRNAs in hormone mediated regulation of breast CSCs.

Role of miR-140 in embryonic bone development and cancer

Bone is increasingly viewed as an endocrine organ with key biological functions. The skeleton produces hormones and cytokines, such as FGF23 and osteocalcin, which regulate an extensive list of homoeostatic functions. Some of these functions include glucose metabolism, male fertility, blood cell production and calcium/phosphate metabolism. Many of the genes regulating these functions are specific to bone cells. Some of these genes can be wrongly expressed by other malfunctioning cells, driving the generation of disease. The miRNAs are a class of non-coding RNA molecules that are powerful regulators of gene expression by suppressing and fine-tuning target mRNAs. Expression of one such miRNA, miR-140, is ubiquitous in chondrocyte cells during embryonic bone development. Activity in cells found in the adult breast, colon and lung tissue can silence genes required for tumour suppression. The realization that the same miRNA can be both normal and detrimental, depending on the cell, tissue and time point, provides a captivating twist to the study of whole-organism functional genomics. With the recent interest in miRNAs in bone biology and RNA-based therapeutics on the horizon, we present a review on the role of miR-140 in the molecular events that govern bone formation in the embryo. Cellular pathways involving miR-140 may be reactivated or inhibited when treating skeletal injury or disorder in adulthood. These pathways may also provide a novel model system when studying cancer biology of other cells and tissues.

MiR-140-3p suppressed cell growth and invasion by downregulating the expression of ATP8A1 in non-small cell lung cancer

MicroRNAs (miRNAs) as a class of small noncoding RNA molecules regulate the expression of targeted gene. The dysregulation of microRNAs is reported to be involved in carcinogenesis and tumor progression. Here, we identified miR-140-3p as a downregulated microRNA in most cancer tissues including lung cancer tissues, compared with their normal counterparts. MiR-140-3p was observed to perform its tumor suppressor function via its inhibition on cell growth, migration and invasion but its induction of cell apoptosis. Furthermore, the growth of non-small-cell lung cancer (NSCLC) cells in nude mouse models were suppressed by overexpression of miR-140-3p. ATP8A1 was demonstrated as a novel direct target of miR-140-3p using a luciferase assay. The increased level of intracellular ATP8A1 protein attenuated the inhibitor role of miR-140-3p in the growth and mobility of NSCLC cell. A regulation mechanism of miR-140-3p for the development and progression of NSCLC through downregulating the ATP8A1 expression was first discovered in the present study.

Roles of sex-determining region Y-box 2 in cell pluripotency and tumor-related signaling pathways

The sex-determining region Y-box 2 (SOX2) gene, a member of the Sry-like high-mobility group box (SOX) gene family, encodes the transcription factor Sox2, which significantly contributes to the regulation of cell pluripotency. Sox2 is closely associated with early embryonic development, neural differentiation and other biological processes. An inreasing number of recent studies suggest that Sox2 exerts a positive effect on malignant tumors. According to these results, Sox2 is expected to become a novel target for cancer therapy by unveiling the mechanism through which it affects the biological behavior of tumors. Therefore, it is crucial to elucidate the detailed association of Sox2 with malignant tumors. The aim of this study was to review the role of Sox2 in pluripotency maintenance, early embryonic development and neural differentiation, as well as investigate the detailed mechanism through which Sox2 regulates cancer stem cells and tumorigenesis.

The roles of ncRNAs and histone-modifiers in regulating breast cancer stem cells

Cancer stem cells (CSCs), a subpopulation of cancer cells with ability of initiating tumorigenesis, exist in many kinds of tumors including breast cancer. Cancer stem cells contribute to treatment resistance and relapse. Conventional treatments only kill differentiated cancer cells, but spare CSCs. Combining conventional treatments with therapeutic drugs targeting to CSCs will eradicate cancer cells more efficiently. Studying the molecular mechanisms of CSCs regulation is essential for developing new therapeutic strategies. Growing evidences showed CSCs are regulated by non-coding RNA (ncRNA) including microRNAs and long non-coding RNAs (lncRNAs), and histone-modifiers, such as let-7, miR-93, miR-100, HOTAIR, Bmi-1 and EZH2. Herein we review the roles of microRNAs, lncRNAs and histone-modifiers especially Polycomb family proteins in regulating breast cancer stem cells (BCSCs).

NRF2/miR-140 signaling confers radioprotection to human lung fibroblasts

Breast and lung cancer patients who are treated with radiotherapy often have severe side effects, including radiation-induced lung damage and secondary cancers. Activation of the NRF2 pathway is a well-known mechanism that protects cells against radiation induced oxidative stress, but its role in radiation-induced lung damage is not well understood. Using human lung fibroblasts (HLFs) we found that ionizing radiation (IR) leads to BRCA1-dependent activation of NRF2 through the inhibition of KEAP1 function, promoting the nuclear accumulation of NRF2, and activating critical radioprotective mechanisms. We discovered that NRF2 directly binds to the miR-140 promoter and increases its expression in response to IR treatment. Gain and loss of function studies further showed the ability of miR-140 to regulate lung fibroblast self-renewal upon irradiation, a potential mechanism to contribute to the regulation of DNA repair. We verified our in vitro findings using primary lung fibroblast cultures from wild type and Nrf2 (KO) mice. Using these models we showed that IR induces overexpression of Brca1, Nrf2 and miR-140 in lung tissue after irradiation. These data reveal a novel radioprotective mechanism in which IR promotes NRF2 nuclear translocation and subsequent activation of miR-140 transcription in HLFs.

Fibroblast Growth Factor 9 Regulation by MicroRNAs Controls Lung Development and Links DICER1 Loss to the Pathogenesis of Pleuropulmonary Blastoma

Pleuropulmonary Blastoma (PPB) is the primary neoplastic manifestation of a pediatric cancer predisposition syndrome that is associated with several diseases including cystic nephroma, Wilms tumor, neuroblastoma, rhabdomyosarcoma, medulloblastoma, and ovarian Sertoli-Leydig cell tumor. The primary pathology of PPB, epithelial cysts with stromal hyperplasia and risk for progression to a complex primitive sarcoma, is associated with familial heterozygosity and lesion-associated epithelial loss-of-heterozygosity of DICER1. It has been hypothesized that loss of heterozygosity of DICER1 in lung epithelium is a non-cell autonomous etiology of PPB and a critical pathway that regulates lung development; however, there are no known direct targets of epithelial microRNAs (miRNAs) in the lung. Fibroblast Growth Factor 9 (FGF9) is expressed in the mesothelium and epithelium during lung development and primarily functions to regulate lung mesenchyme; however, there are no known mechanisms that regulate FGF9 expression during lung development. Using mouse genetics and molecular phenotyping of human PPB tissue, we show that FGF9 is overexpressed in lung epithelium in the initial multicystic stage of Type I PPB and that in mice lacking epithelial Dicer1, or induced to overexpress epithelial Fgf9, increased Fgf9 expression results in pulmonary mesenchymal hyperplasia and a multicystic architecture that is histologically and molecularly indistinguishable from Type I PPB. We further show that miR-140 is expressed in lung epithelium, regulates epithelial Fgf9 expression, and regulates pseudoglandular stages of lung development. These studies identify an essential miRNA-FGF9 pathway for lung development and a non-cell autonomous signaling mechanism that contributes to the mesenchymal hyperplasia that is characteristic of Type I PPB.

Targeting exosomes from preadipocytes inhibits preadipocyte to cancer stem cell signaling in early-stage breast cancer

The tumor microenvironment plays a critical role in regulating breast tumor progression. Signaling between preadipocytes and breast cancer cells has been found to promote breast tumor formation and metastasis. Exosomes secreted from preadipocytes are important components of the cancer stem cell niche. Mouse preadipocytes (3T3L1) are treated with the natural antitumor compound shikonin (SK) and exosomes derived from mouse preadipocytes are co-cultured with MCF10DCIS cells. We examine how preadipocyte-derived exosomes can regulate early-stage breast cancer via regulating stem cell renewal, cell migration, and tumor formation. We identify a critical miR-140/SOX2/SOX9 axis that regulates differentiation, stemness, and migration in the tumor microenvironment. Next, we find that the natural antitumor compound SK can inhibit preadipocyte signaling inhibiting nearby ductal carcinoma in situ (DCIS) cells. Through co-culture experiments, we find that SK-treated preadipocytes secrete exosomes with high levels of miR-140, which can impact nearby DCIS cells through targeting SOX9 signaling. Finally, we find that preadipocyte-derived exosomes promote tumorigenesis in vivo, providing strong support for the importance of exosomal signaling in the tumor microenvironment. Our data also show that targeting the tumor microenvironment may assist in blocking tumor progression.

Epigenetic Regulation of miRNAs and Breast Cancer Stem Cells

MicroRNAs have emerged as important targets of chemopreventive strategies in breast cancer. We have found that miRNAs are dysregulated at an early stage in breast cancer, in non-malignant Ductal Carcinoma In Situ. Many dietary chemoprevention agents can act by epigenetically activating miRNA-signaling pathways involved in tumor cell proliferation and invasive progression. In addition, many miRNAs activated via chemopreventive strategies target cancer stem cell signaling and prevent tumor progression or relapse. Specifically, we have found that miRNAs regulate DCIS stem cells, which may play important roles in breast cancer progression to invasive disease. We have shown that chemopreventive agents can directly inhibit DCIS stem cells and block tumor formation in vivo, via activation of tumor suppressor miRNAs.

Roles of microRNA-140 in stem cell-associated early stage breast cancer

An increasing body of evidence supports a stepwise model for progression of breast cancer from ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC). Due to the high level of DCIS heterogeneity, we cannot currently predict which patients are at highest risk for disease recurrence or progression. The mechanisms of progression are still largely unknown, however cancer stem cell populations in DCIS lesions may serve as malignant precursor cells intimately involved in progression. While genetic and epigenetic alterations found in DCIS are often shared by IDC, mRNA and miRNA expression profiles are significantly altered. Therapeutic targeting of cancer stem cell pathways and differentially expressed miRNA could have significant clinical benefit. As tumor grade increases, miRNA-140 is progressively downregulated. miR-140 plays an important tumor suppressive role in the Wnt, SOX2 and SOX9 stem cell regulator pathways. Downregulation of miR-140 removes inhibition of these pathways, leading to higher cancer stem cell populations and breast cancer progression. miR-140 downregulation is mediated through both an estrogen response element in the miR-140 promoter region and differential methylation of CpG islands. These mechanisms are novel targets for epigenetic therapy to activate tumor suppressor signaling via miR-140. Additionally, we briefly explored the emerging role of exosomes in mediating intercellular miR-140 signaling. The purpose of this review is to examine the cancer stem cell signaling pathways involved in breast cancer progression, and the role of dysregulation of miR-140 in regulating DCIS to IDC transition.

Profiling gene promoter occupancy of Sox2 in two phenotypically distinct breast cancer cell subsets using chromatin immunoprecipitation and genome-wide promoter microarrays

Introduction

Aberrant expression of the embryonic stem cell marker Sox2 has been reported in breast cancer (BC). We previously identified two phenotypically distinct BC cell subsets separated based on their differential response to a Sox2 transcription activity reporter, namely the reporter-unresponsive (RU) and the more tumorigenic reporter-responsive (RR) cells. We hypothesized that Sox2, as a transcription factor, contributes to their phenotypic differences by mediating differential gene expression in these two cell subsets.

Methods

We used chromatin immunoprecipitation and a human genome-wide promoter microarray (ChIP-chip) to determine the promoter occupancies of Sox2 in the MCF7 RU and RR breast cancer cell populations. We validated our findings with conventional chromatin immunoprecipitation, quantitative reverse transcription polymerase chain reaction (qPCR), and western blotting using cell lines, and also performed qPCR using patient RU and RR samples.

Results

We found a largely mutually exclusive profile of gene promoters bound by Sox2 between RU and RR cells derived from MCF7 (1830 and 456 genes, respectively, with only 62 overlapping genes). Sox2 was bound to stem cell- and cancer-associated genes in RR cells. Using quantitative RT-PCR, we confirmed that 15 such genes, including PROM1 (CD133), BMI1, GPR49 (LGR5), and MUC15, were expressed significantly higher in RR cells. Using siRNA knockdown or enforced expression of Sox2, we found that Sox2 directly contributes to the higher expression of these genes in RR cells. Mucin-15, a novel Sox2 downstream target in BC, contributes to the mammosphere formation of BC cells. Parallel findings were observed in the RU and RR cells derived from patient samples.

Conclusions

In conclusion, our data supports the model that the Sox2 induces differential gene expression in the two distinct cell subsets in BC, and contributes to their phenotypic differences.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-014-0470-2) contains supplementary material, which is available to authorized users.

The many faces of estrogen signaling

Estrogens have long been known as important regulators of the female reproductive functions; however, our understanding of the role estrogens play in the human body has changed significantly over the past years. It is now commonly accepted that estrogens and androgens have important functions in both female and male physiology and pathology. This is in part due to the local synthesis and action of estrogens that broadens the role of estrogen signaling beyond that of the endocrine system. Furthermore, there are several different mechanisms through which the three estrogen receptors (ERs), ERα, ERβ and G protein-coupled estrogen receptor 1 (GPER1) are able to regulate target gene transcription. ERα and ERβ are mostly associated with the direct and indirect genomic signaling pathways that result in target gene expression. Membrane-bound GPER1 is on the other hand responsible for the rapid non-genomic actions of estrogens that activate various protein-kinase cascades. Estrogen signaling is also tightly connected with another important regulatory entity, i.e. epigenetic mechanisms. Posttranslational histone modifications, microRNAs (miRNAs) and DNA methylation have been shown to influence gene expression of ERs as well as being regulated by estrogen signaling. Moreover, several coregulators of estrogen signaling also exhibit chromatin-modifying activities further underlining the importance of epigenetic mechanisms in estrogen signaling. This review wishes to highlight the newer aspects of estrogen signaling that exceed its classical endocrine regulatory role, especially emphasizing its tight intertwinement with epigenetic mechanisms.

NRF2/long noncoding RNA ROR signaling regulates mammary stem cell expansion and protects against estrogen genotoxicity

Long noncoding RNAs (lncRNAs) have emerged as key regulators of gene expression in embryonic stem cell (ESC) self-renewal and differentiation. In ESCs, lncRNAs are regulated at the genetic level via transcription factor binding to lncRNA gene promoters. Here we demonstrate that the key cytoprotective transcription factor NRF2 controls lncRNA expression in mammary stem cells. By profiling lncRNAs in wild-type and NRF2 knockdown mammary stem cells, we demonstrate that the lncRNA ROR, a regulator of embryonic stem cell pluripotency, is overexpressed upon NRF2 knockdown. We performed promoter analyses and examined predicted NRF2 binding elements in the ROR promoter using luciferase reporter constructs of a ROR promoter deletion series. Our studies revealed that NRF2 binds to two specific NRF2 response elements flanking the ROR promoter and that these two NRF2 response elements are equally important to suppress ROR transcription. In addition, we identified associated H3K27me3 chromatin modification and EZH2 binding at the ROR promoter that was dependent on NRF2 binding. We observed that NRF2 knockdown or ROR overexpression leads to increased stem cell self-renewal in mammary stem cells. Furthermore, we demonstrate Nrf2 regulation of the mammary stem cell population in vivo. These observations provide further evidence for the critical role of NRF2 in maintaining normal stem cell subpopulations in mammary epithelium.

Epigenetic reprogramming in breast cancer: from new targets to new therapies

Breast cancer is the most commonly diagnosed cancer and the second leading cause of cancer death among women in the United States. Recently, interest has grown in the role of epigenetics in breast cancer development and progression. Epigenetic changes such as DNA methylation, histone modifications, and abnormal expression of non-coding RNAs emerged as novel biomarkers in breast cancer diagnosis, therapy, and prevention. This review focuses on the most recent mechanistic findings underlying epigenetic changes in breast cancer development and their role as predictors of breast cancer risk. The rapid progress in our understanding of epigenetic findings in breast cancer has opened new avenues for potential therapeutic approaches via identification of epigenetic targets. We highlight the development of novel epigenetically targeted drugs, relevant clinical trials in breast cancer patients, and recent approaches combining epigenetic agents with chemotherapy and/or endocrine therapy that may incrementally improve long-term outcomes in appropriately selected breast cancer patients. Biomarkers of response are needed, however, to identify patient subsets that are most likely to benefit from epigenetic treatment strategies.

Targeting breast cancer initiating cells: advances in breast cancer research and therapy

Over the past 10 years there have been significant advances in our understanding of breast cancer and the important roles that breast cancer initiating cells (CICs) play in the development and resistance of breast cancer. Breast CICs endowed with self-renewing and tumor-initiating capacities are believed to be responsible for the relapses which often occur after various breast cancer therapies. In this review, we will summarize some of the key developments in breast CICs which will include discussion of some of the key genes implicated: estrogen receptor (ER), HER2, BRCA1, TP53, PIK3CA, RB, P16INK1 and various miRs as well some drugs which are showing promise in targeting CICs. In addition, the concept of combined therapies will be discussed. Basic and clinical research is resulting in novel approaches to improve breast cancer therapy by targeting the breast CICs.

Increased expression of the pluripotency markers sex-determining region Y-box 2 and Nanog homeobox in ovarian endometriosis

BACKGROUND

The precise etiology of endometriosis is not fully understood; the involvement of stem cells theory is a new hypothesis. Related studies mainly focus on stemness-related genes, and pluripotency markers may play a role in the etiology of endometriosis. We aimed to analyze the transcription pluripotency factors sex-determining region Y-box 2 (SOX2), Nanog homeobox (NANOG), and octamer-binding protein 4 (OCT4) in the endometrium of reproductive-age women with and without ovarian endometriosis.

METHODS

We recruited 26 women with laparoscopy-diagnosed ovarian endometriosis (endometriosis group) and 16 disease-free women (control group) to the study. Endometrial and endometriotic samples were collected. SOX2, NANOG, and OCT4 expression were analyzed with quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry.

RESULTS

Compared to the control group, SOX2 mRNA and protein expression was significantly higher in the eutopic endometrium of participants in the endometriosis group. In the endometriosis group, SOX2 and NANOG mRNA and protein expression were significantly increased in ectopic endometrium compared with eutopic endometrium; there was a trend towards lower OCT4 mRNA expression and higher OCT4 protein expression in ectopic endometrium.

CONCLUSIONS

The transcription pluripotency factors SOX2 and NANOG were overexpression in ovarian endometriosis, their role in pathogenesis of endometriosis should be further studied.

Downregulation of miR-638 promotes invasion and proliferation by regulating SOX2 and induces EMT in NSCLC

Aberrant expression of microRNAs has been shown to regulate the biological processes of lung cancer cells. However, the role of miR-638 in the development of NSCLC is still unclear. In this study, low miR-638 and high SOX2 were shown to be associated with tumor size and metastasis of NSCLC patients. Downregulated miR-638 could promote cell invasion and proliferation, while high miR-638 expression reversed the effect. Furthermore, miR-638 could regulate SOX2 by directly binding to its 3'-UTR. Silencing of SOX2 by siRNA partially abolished the enhancement of cell invasion and proliferation induced by downregulated miR-638. Aberrant miR-638 expression could modulate the expression levels of markers of epithelial-to-mesenchymal transition. Our results indicate that miR-638 may play a pivotal role in the development of NSCLC.

Clinical significance of miR-140-5p and miR-193b expression in patients with breast cancer and relationship to IGFBP5

The functional role of IGFBP5 in breast cancer is complicated. Experimental and bioinformatics studies have shown that IGFBP5 is targeted by miR-140-5p and miR-193b, although this has not yet been proven in clinical samples. The aim of this study was to evaluate the expression of miR-140-5p and miR-193b in breast cancer and adjacent normal tissue and assess its correlation with IGFBP5 and the clinicopathological characteristics of the tumors. IGFBP5 protein expression was analyzed immunohistochemically and IGFBP5, miR-140 and miR-193b mRNA expression levels were analyzed with real-time RT-PCR. Tumor tissue had higher miR-140-5p expression than adjacent normal tissue (p = 0.015). Samples with no immunohistochemical staining for IGFBP5 showed increased miR-140-5p expression (p = 0.009). miR-140-5p expression was elevated in invasive ductal carcinomas (p = 0.002), whereas basal-like tumors had decreased expression of miR-140-5p compared to other tumors (p = 0.008). Lymph node-positive samples showed an approximately 13-fold increase in miR-140-5p expression compared to lymph node-negative tissue (p = 0.049). These findings suggest that miR-140-5p, but not miR-193b, could be an important determinant of IGFBP5 expression and clinical phenotype in breast cancer patients. Further studies are needed to clarify the expressional regulation of IGFBP5 by miR-140-5p.

A systematic in silico mining of the mechanistic implications and therapeutic potentials of estrogen receptor (ER)-α in breast cancer

Estrogen receptor (ER)-α has long been a potential target in ER-α-positive breast cancer therapeutics. In this study, we integrated ER-α-related bioinformatic data at different levels to systematically explore the mechanistic and therapeutic implications of ER-α. Firstly, we identified ER-α-interacting proteins and target genes of ER-α-regulating microRNAs (miRNAs), and analyzed their functional gene ontology (GO) annotations of those ER-α-associated proteins. In addition, we predicted ten consensus miRNAs that could target ER-α, and screened candidate traditional Chinese medicine (TCM) compounds that might hit diverse conformations of ER-α ligand binding domain (LBD). These findings may help to uncover the mechanistic implications of ER-α in breast cancer at a systematic level, and provide clues of miRNAs- and small molecule modulators- based strategies for future ER-α-positive breast cancer therapeutics.

Estrogen regulates the tumour suppressor MiRNA-30c and its target gene, MTA-1, in endometrial cancer

MicroRNA-30c (miR-30c) has been reported to be a tumour suppressor in endometrial cancer (EC). We demonstrate that miR-30c is down-regulated in EC tissue and is highly expressed in estrogen receptor (ER)-negative HEC-1-B cells. MiR-30c directly inhibits MTA-1 expression and functions as a tumour suppressor via the miR-30c-MTA-1 signalling pathway. Furthermore, miR-30c is decreased upon E2 treatment in both ER-positive Ishikawa and ER-negative HEC-1-B cells. Taken together, our results suggest that miR-30c is an important deregulated miRNA in EC and might serve as a potential biomarker and novel therapeutic target for EC.

miR-625 down-regulation promotes proliferation and invasion in esophageal cancer by targeting Sox2

miR-625 has been reported to exhibit abnormal expression in esophageal cancer (EC), but the mechanism and functions of miR-625 in esophageal cancer remain unclear. miR-625 down-regulation and Sox2 up-regulation were validated by qRT-PCR in 158 EC samples. Low expression of miR-625 promotes cell proliferation and invasion, while high expression of miR-625 has the opposite effect. Sox2, a target gene of miR-625, was examined by luciferase assay and western blot. Our data suggest that miR-625 may regulate the biological processes of EC via controlling Sox2 expression.

Role of SOX2 in the etiology of embryonal carcinoma, based on analysis of the NCCIT and NT2 cell lines

The transcription factor SOX2, associated with amongst others OCT3/4, is essential for maintenance of pluripotency and self-renewal of embryonic stem cells. SOX2 is highly expressed in embryonal carcinoma (EC), the stem cell component of malignant nonseminomatous germ cell tumors, referred to as germ cell cancer (GCC). In fact, OCT3/4 together with SOX2 is an informative diagnostic tool for EC in a clinical setting. Several studies support the hypothesis that SOX2 is a relevant oncogenic factor in various cancers and recently, SOX2 has been suggested as a putative therapeutic target for early stage EC. We demonstrate the presence of genomic amplification of SOX2 in an EC cell line, NCCIT, using array comparative genome hybridization and fluorescence in situ hybridization. Down-regulation of SOX2 by targeted siRNA provokes NCCIT cells towards apoptosis, while inhibition of OCT3/4 expression induced differentiation, with retained SOX2 levels. Mice pluripotent xenografts from NCCIT (N-NCCIT and N2-NCCIT) show a consistent SOX2 expression, in spite of loss of the expression of OCT3/4, and differentiation, with retained presence of genomic amplification. No SOX2 amplification has been identified in primary pure and mixed EC in vivo patient samples so far. The data presented in this study are based on a single EC cell line with a SOX2 amplification, with NT2 as control EC cell line, showing no profound induction of apoptosis upon SOX2 downregulation. The findings are of relevance to identify mechanisms involved in the pathogenesis of EC tumors, and support the model of SOX2-oncogene dependency of EC, which however, does not exclude induction of differentiation. This finding is likely related to the presence of wild type p53 in GCC, resulting in expression of downstream target genes, amongst others miR-34a, miR-145 and SOX2, associated to the unique sensitivity of GCC to DNA damaging agents.

Examining estrogen regulation of cancer stem cells through multicolor lineage tracing

We have designed a dual-color fluorescent reporter that can track microRNA expression in vitro, which can be used for lineage tracing experiments. We have used this system to track miR-140 promoter activity in breast cancer cells and to follow the impact of estrogen signaling in cancer stem cell subpopulations.

miR-126 functions as a tumor suppressor in osteosarcoma by targeting Sox2

Osteosarcoma (OS) is the most common malignant bone tumor in children and young adults, the early symptoms and signs of which are non-specific. The discovery of microRNAs (miRNAs) provides a new avenue for the early diagnosis and treatment of OS. miR-126 has been reported to be highly expressed in vascularized tissues, and is recently widely studied in cancers. Herein, we explored the expression and significance of miR-126 in OS. Using TaqMan RT-PCR analysis, we analyzed the expression of miR-126 in 32 paired OS tumor tissues and 4 OS cell lines and found that miR-126 was consistently under-expressed in OS tissues and cell lines compared with normal bone tissues and normal osteoblast cells (NHOst), respectively. As miR-126 is significantly decreased in OS tissues and cell lines, we sought to compensate for its loss through exogenous transfection into MG-63 cells with a miR-126 mimic. Ectopic expression of miR-126 inhibited cell proliferation, migration and invasion, and induced apoptosis of MG-63 cells. Moreover, bioinformatic prediction suggested that the sex-determining region Y-box 2 (Sox2) is a target gene of miR-126. Using mRNA and protein expression analysis, luciferase assays and rescue assays, we demonstrate that restored expression of Sox2 dampened miR-126-mediated suppression of tumor progression, which suggests the important role of miR-126/Sox2 interaction in tumor progression. Taken together, our data indicate that miR-126 functions as a tumor suppressor in OS, which exerts its activity by suppressing the expression of Sox2.

A coregulatory network of NR2F1 and microRNA-140

BACKGROUND

Both nuclear receptor subfamily 2 group F member 1 (NR2F1) and microRNAs (miRNAs) have been shown to play critical roles in the developing and functional inner ear. Based on previous studies suggesting interplay between NR2F1 and miRNAs, we investigated the coregulation between NR2F1 and miRNAs to better understand the regulatory mechanisms of inner ear development and functional maturation.

RESULTS

Using a bioinformatic approach, we identified 11 potential miRNAs that might coregulate target genes with NR2F1 and analyzed their targets and potential roles in physiology and disease. We selected 6 miRNAs to analyze using quantitative real-time (qRT) -PCR and found that miR-140 is significantly down-regulated by 4.5-fold (P=0.004) in the inner ear of NR2F1 knockout (Nr2f1(-/-)) mice compared to wild-type littermates but is unchanged in the brain. Based on this, we performed chromatin-immunoprecipitation followed by qRT-PCR and confirmed that NR2F1 directly binds and regulates both miR-140 and Klf9 in vivo. Furthermore, we performed luciferase reporter assay and showed that miR-140 mimic directly regulates KLF9-3'UTR, thereby establishing and validating an example coregulatory network involving NR2F1, miR-140, and Klf9.

CONCLUSIONS

We have described and experimentally validated a novel tissue-dependent coregulatory network for NR2F1, miR-140, and Klf9 in the inner ear and we propose the existence of many such coregulatory networks important for both inner ear development and function.

Reprogramming of non-genomic estrogen signaling by the stemness factor SOX2 enhances the tumor-initiating capacity of breast cancer cells

The restoration of pluripotency circuits by the reactivation of endogenous stemness factors, such as SOX2, may provide a new paradigm in cancer development. The tumoral stem cell reprogramming hypothesis, i.e., the ability of stemness factors to redirect normal and differentiated tumor cells toward a less-differentiated and stem-like state, adds new layers of complexity to cancer biology, because the effects of such reprogramming may remain dormant until engaged later in response to (epi)genetic and/or (micro)environmental events. To test this hypothesis, we utilized an in vitro model of a SOX2-overexpressing cancer stem cell (CSC)-like cellular state that was recently developed in our laboratory by employing Yamanaka's nuclear reprogramming technology in the estrogen receptor α (ERα)-positive MCF-7 breast cancer cell line. Despite the acquisition of distinct molecular features that were compatible with a breast CSC-like cellular state, such as strong aldehyde dehydrogenase activity, as detected by ALDEFLUOR, and overexpression of the SSEA-4 and CD44 breast CSC markers, the tumor growth-initiating ability of SOX2-overexpressing CSC-like MCF-7 cells solely occurred in female nude mice supplemented with estradiol when compared with MCF-7 parental cells. Ser118 phosphorylation of estrogen receptor α (ERα), which is a pivotal integrator of the genomic and nongenomic E 2/ERα signaling pathways, drastically accumulated in nuclear speckles in the interphase nuclei of SOX2-driven CSC-like cell populations. Moreover, SOX2-positive CSC-like cells accumulated significantly higher numbers of actively dividing cells, and the highest levels of phospho-Ser118-ERα occurred when chromosomes lined up on a metaphase plate. The previously unrecognized link between E 2/ERα signaling and SOX2-driven stem cell circuitry may significantly impact our current understanding of breast cancer initiation and progression, i.e., SOX2 can promote non-genomic E 2 signaling that leads to nuclear phospho-Ser118-ERα, which ultimately exacerbates genomic ER signaling in response to E 2. Because E 2 stimulation has been recently shown to enhance breast tumor-initiating cell survival by downregulating miR-140, which targets SOX2, the establishment of a bidirectional cross-talk interaction between the stem cell self-renewal regulator, SOX2, and the local and systemic ability of E 2 to increase breast CSC activity may have profound implications for the development of new CSC-directed strategies for breast cancer prevention and therapy.

miR-140 suppresses tumor growth and metastasis of non-small cell lung cancer by targeting insulin-like growth factor 1 receptor

MicroRNAs (miRNAs) are a class of small noncoding RNA molecules that play important roles in carcinogenesis and tumor progression. In this study, we investigated the roles and mechanisms of miR-140 in human non-small cell lung cancer (NSCLC). We found that miR-140 is significantly downregulated in NSCLC tissues and cell lines. Both gain-of-function and loss-of-function studies demonstrated that miR-140 suppresses NSCLC cell proliferation, migration, and invasion in vitro. Importantly, overexpression of miR-140 effectively repressed tumor growth and metastasis in nude mouse models. Integrated analysis identified IGF1R as a direct and functional target of miR-140. Knockdown of IGF1R inhibited cell proliferation and invasion resembling that of miR-140 overexpression, while overexpression of IGF1R attenuated the function of miR-140 in NSCLC cells. Together, our results highlight the significance of miR-140 and IGF1R in the development and progression of NSCLC.