miR-200 enhances mouse breast cancer cell colonization to form distant metastases

MicroRNA Regulation of Human Breast Cancer Stem Cells

MicroRNAs (miRNAs) are involved in virtually all biological processes, including stem cell maintenance, differentiation, and development. The dysregulation of miRNAs is associated with many human diseases including cancer. We have identified a set of miRNAs differentially expressed between human breast cancer stem cells (CSCs) and non-tumorigenic cancer cells. In addition, these miRNAs are similarly upregulated or downregulated in normal mammary stem/progenitor cells. In this review, we mainly describe the miRNAs that are dysregulated in human breast CSCs directly isolated from clinical specimens. The miRNAs and their clusters, such as the miR-200 clusters, miR-183 cluster, miR-221-222 cluster, let-7, miR-142 and miR-214, target the genes and pathways important for stem cell maintenance, such as the self-renewal gene BMI1, apoptosis, Wnt signaling, Notch signaling, and epithelial-to-mesenchymal transition. In addition, the current evidence shows that metastatic breast CSCs acquire a phenotype that is different from the CSCs in a primary site. Thus, clarifying the miRNA regulation of the metastatic breast CSCs will further advance our understanding of the roles of human breast CSCs in tumor progression.

HER2 induced EMT and tumorigenicity in breast epithelial progenitor cells is inhibited by coexpression of EGFR

The members of the epidermal growth factor receptor (EGFR) kinase family are important players in breast morphogenesis and cancer. EGFR2/HER2 and EGFR expression have a prognostic value in certain subtypes of breast cancer such as HER2-amplified, basal-like and luminal type B. Many clinically approved small molecular inhibitors and monoclonal antibodies have been designed to target HER2, EGFR or both. There is, however, still limited knowledge on how the two receptors are expressed in normal breast epithelium, what effects they have on cellular differentiation and how they participate in neoplastic transformation. D492 is a breast epithelial cell line with stem cell properties that can undergo epithelial to mesenchyme transition (EMT), generate luminal- and myoepithelial cells and form complex branching structures in three-dimensional (3D) culture. Here, we show that overexpression of HER2 in D492 (D492^HER2) resulted in EMT, loss of contact growth inhibition and increased oncogenic potential in vivo. HER2 overexpression, furthermore, inhibited endogenous EGFR expression. Re-introducing EGFR in D492^HER2 (D492^HER2/EGFR) partially reversed the mesenchymal state of the cells, as an epithelial phenotype reappeared both in 3D cultures and in vivo. The D492^HER2/EGFR xenografts grow slower than the D492^HER2 tumors, while overexpression of EGFR alone (D492^EGFR) was not oncogenic in vivo. Consistent with the EGFR-mediated epithelial phenotype, overexpression of EGFR drove the cells toward a myoepithelial phenotype in 3D culture. The effect of two clinically approved anti-HER2 and EGFR therapies, trastuzumab and cetuximab, was tested alone and in combination on D492^HER2 xenografts. While trastuzumab had a growth inhibitory effect compared with untreated control, the effect of cetuximab was limited. When administered in combination, the growth inhibitory effect of trastuzumab was less pronounced. Collectively, our data indicate that in HER2-overexpressing D492 cells, EGFR can behave as a tumor suppressor, by pushing the cells towards epithelial differentiation.

ABCG2 localizes to the nucleus and modulates CDH1 expression in lung cancer cells

Breast cancer resistance protein [BCRP/ATP-binding cassette subfamily G member 2 (ABCG2)] is a member of the ATP-binding cassette transporter family. The presence of ABCG2 on the plasma membrane in many kinds of human cancer cells contributes to multidrug resistance during chemotherapy, and it has been used as the side population marker for identifying cancer stem cells in lung cancers. We report here that, in addition to the membranous form, ABCG2 proteins are also found inside the nucleus, where they bind to the E-box of CDH1 (E-cadherin) promoter and regulate transcription of this gene. Increased expression of ABCG2 causes an increase of E-cadherin and attenuates cell migration, whereas knockdown of ABCG2 downregulates E-cadherin and enhances cell motility. In mice, xenografted A549 cells that have less ABCG2 are more likely to metastasize from the subcutaneous inoculation site to the internal organs. However, for the cancer cells that have already entered the blood circulation, an increased level of ABCG2, and correspondingly increased E-cadherin, may facilitate circulating cancer cells to colonize at a distant site and form a metastatic tumor. We propose a novel role for nuclear ABCG2 that functions as a transcription regulator and participates in modulation of cancer metastasis.

Differential membranous E-cadherin expression, cell proliferation and O-GlcNAcylation between primary and metastatic nodal lesion in colorectal cancer

INTRODUCTION

O-GlcNAcylation is an O-linked β-N-acetylglucosamine (O-GlcNAc) moiety linked to the side chain hydroxyl of a serine or threonine residue. The E-cadherin/β-catenin system, an integral component of epithelial to mesenchymal transition (EMT)/mesenchymal to epithelial transition (MET), is affected through O-GlcNAcylation. The current study examined the status of EMT/MET in both the tumor center and invasive front of the primary colorectal carcinoma (CRC) and metastatic nodal lesions, which were compared to O-GlcNAcylation expression levels in those areas. In addition, the cliniopathological significance of O-GlcNAcylation was studied

MATERIAL AND METHODS

Immunohistochemical staining for E-cadherin, β-catenin, Snail, O-GlcNAc and Ki67 was performed in 40 primary CRC tissues, 40 nonneoplastic colons, and 17 nodal metastatic lesions. Western blot was also conducted in primary CRC tissue

RESULTS

Membranous E-cadherin expression was lowest in the invasive front, but showed greater increases in metastatic nodal lesions. Moreover, its expression level was negatively correlated with that of nuclear β-catenin and Snail. The Ki67 labeling index (LI) was lowest in the invasive front, and increased in metastatic nodal lesions. Primary CRC showed higher expression of O-GlcNAcylation and O-GlcNAc-transferase (OGT) than nonneoplastic colons. O-GlcNAcylation expression decreased in metastatic nodal lesions compared to the invasive front and tumor center, and was inversely correlated with Ki67 LI. However, O-GlcNAcylation expression was only slightly changed between tumor center and invasive front. In addition, there was no correlation between its expression and the level of nuclear β-catenin, membranous E-cadherin and Snail. No significant relationship was observed between O-GlcNAcylation level and cliniopathological parameters.

CONCLUSIONS

Differential membranous E-cadherin expression, cell proliferation and O-GlcNAcylation in metastatic nodal lesion compared to primary CRC may play role in establishing its lesions; however, these findings are not sufficient to show the role of O-GlcNAcylation in the EMT/MET of CRC.

MiRNAs and Other Epigenetic Changes as Biomarkers in Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) is characterised by the lack of receptors for estrogen (ER), progesterone (PR), and human epidermal growth factor 2 (HER2). Since it cannot be treated by current endocrine therapies which target these receptors and due to its aggressive nature, it has one of the worst prognoses of all breast cancer subtypes. The only treatments remain chemo- and/or radio-therapy and surgery and because of this, novel biomarkers or treatment targets are urgently required to improve disease outcomes. MicroRNAs represent an attractive candidate for targeted therapies against TNBC, due to their natural ability to act as antisense interactors and regulators of entire gene sets involved in malignancy and their superiority over mRNA profiling to accurately classify disease. Here we review the current knowledge regarding miRNAs as biomarkers in TNBC and their potential use as therapeutic targets in this disease. Further, we review other epigenetic changes and interactions of these changes with microRNAs in this breast cancer subtype, which may lead to the discovery of new treatment targets for TNBC.

Snail1-dependent control of embryonic stem cell pluripotency and lineage commitment

Embryonic stem cells (ESCs) exhibit the dual properties of self-renewal and pluripotency as well as the ability to undergo differentiation that gives rise to all three germ layers. Wnt family members can both promote ESC maintenance and trigger differentiation while also controlling the expression of Snail1, a zinc-finger transcriptional repressor. Snail1 has been linked to events ranging from cell cycle regulation and cell survival to epithelial-mesenchymal transition (EMT) and gastrulation, but its role in self-renewal, pluripotency or lineage commitment in ESCs remains undefined. Here we demonstrate using isogenic pairs of conditional knockout mouse ESCs, that Snail1 exerts Wnt- and EMT independent control over the stem cell transcriptome without affecting self-renewal or pluripotency-associated functions. By contrast, during ESC differentiation, an endogenous Wnt-mediated burst in Snail1 expression regulates neuroectodermal fate while playing a required role in epiblast stem cell exit and the consequent lineage fate decisions that define mesoderm commitment.

The H19 Long non-coding RNA in cancer initiation, progression and metastasis - a proposed unifying theory

The imprinted oncofetal long non-coding RNA (lncRNA) H19 is expressed in the embryo, down-regulated at birth and then reappears in tumors. Its role in tumor initiation and progression has long been a subject of controversy, although accumulating data suggest that H19 is one of the major genes in cancer. It is actively involved in all stages of tumorigenesis and is expressed in almost every human cancer. In this review we delineate the various functions of H19 during the different stages in the complex process of tumor progression. H19 up-regulation allows cells to enter a "selfish" survival mode in response to stress conditions, such as destabilization of the genome and hypoxia, by accelerating their proliferation rate and increasing overall cellular resistance to stress. This response is tightly correlated with nullification, dysfunction or significant down-regulation of the master tumor suppressor gene P53. The growing evidence of H19's involvement in both proliferation and differentiation processes, together with its involvement in epithelial to mesenchymal transition (EMT) and also mesenchymal to epithelial transition (MET), has led us to conclude that some of the recent disputes and discrepancies arising from current research findings can be resolved from a viewpoint supporting the oncogenic properties of H19. According to a holistic approach, the versatile, seemingly contradictory functions of H19 are essential to, and differentially harnessed by, the tumor cell depending on its context within the process of tumor progression.

MicroRNAs in breast cancer: oncogene and tumor suppressors with clinical potential

MicroRNAs (miRs) are small single-stranded RNA molecules, which function as key negative regulators of post-transcriptional modulation in almost all biological processes. Abnormal expression of microRNAs has been observed in various types of cancer including breast cancer. Great efforts have been made to identify an association between microRNA expression profiles and breast cancer, and to understand the functional role and molecular mechanism of aberrant-expressed microRNAs. As research progressed, 'oncogenic microRNAs' and 'tumor suppressive microRNAs' became a focus of interest. The potential of candidate microRNAs from both intercellular (tissue) and extracellular (serum) sources for clinical diagnosis and prognosis was revealed, and treatments involving microRNA achieved some amazing curative effects in cancer disease models. In this review, advances from the most recent studies of microRNAs in one of the most common cancers, breast cancer, are highlighted, especially the functions of specifically selected microRNAs. We also assess the potential value of these microRNAs as diagnostic and prognostic markers, and discuss the possible development of microRNA-based therapies.

Abnormal expression of miR-1 in breast carcinoma as a potent prognostic factor

Metastatic breast cancer remains a highly lethal disease, and it is very important to evaluate the biomarkers associated with the distant metastasis. MicroRNA (miRNA) are small non‐protein coding RNA that regulate various cellular functions. Recent investigations have demonstrated the importance of some miRNA in breast cancer, but the significance of the great majority of miRNA remains largely unclear in breast cancer metastasis. Therefore, in this study, we first examined expression profiles of miRNA in stage IV breast carcinoma tissues, comparing stage I–III cases by miRNA PCR array, and identified miR‐1 as the miRNA which was the most associated with the distant metastasis. However, miR‐1 has not yet been examined in breast carcinoma tissue, and its significance remains unknown. Therefore, we further examined miR‐1 expression in breast carcinoma using in situ hybridization (ISH). miR‐1 was localized in carcinoma cells in 20% of breast carcinoma cases, but it was negligible in non‐neoplastic mammary glands or stroma. miR‐1 ISH status was significantly associated with stage, pathological T factor, lymph node metastasis, distant metastasis, histological grade, estrogen receptor, progesterone receptor and Ki‐67 in breast carcinoma. Moreover, the miR‐1 status was demonstrated using multivariate analysis as an independent worse prognostic factor for both disease‐free and breast cancer‐specific survival. These findings suggest that abnormal miR‐1 expression is associated with an aggressive phenotype of breast carcinoma and that miR‐1 status is a potent prognostic factor in human breast cancer patients.

MicroRNA heterogeneity in endometrial cancer cell lines revealed by deep sequencing

The aim of the present study was to obtain comprehensive microRNA (miRNA) profiles of type I [Ishikawa (ISK)] and type II (HEC-1B) human endometrial adenocarcinoma cell lines, utilizing the latest high-throughput sequencing techniques. RNA was extracted from ISK and HEC-1B cell lines. Sequencing results were obtained from a next-generation sequencing platform. Using the miRBase database and a series of software pipelines, miRNA expression was analyzed in the ISK and HEC-1B cell lines. It was revealed that the type and quantity of miRNAs in the two cell types varied significantly; 34 miRNAs were upregulated and 105 miRNAs were downregulated in HEC-1B cells compared with those of ISK cells. Furthermore, it was observed that the expression pattern of the miRNA (miR)-17-92 cluster differed between the two cell types, and the expression levels of the miR-200 family in ISK cells were markedly increased compared with those of HEC-1B cells. The present study therefore identified potential novel biomarkers, which may be useful in the differentiation between type I and type II endometrial cancer, and also revealed miRNA alterations that may be associated with endometrial cancer and its underlying pathogenic mechanisms.

Analysis of the miRNA-mRNA-lncRNA networks in ER+ and ER- breast cancer cell lines

Recently, rapid advances in bioinformatics analysis have expanded our understanding of the transcriptome to a genome‐wide level. miRNA–mRNA–lncRNA interactions have been shown to play critical regulatory role in cancer biology. In this study, we discussed the use of an integrated systematic approach to explore new facets of the oestrogen receptor (ER)‐regulated transcriptome. The identification of RNAs that are related to the expression status of the ER may be useful in clinical therapy and prognosis. We used a network modelling strategy. First, microarray expression profiling of mRNA, lncRNA and miRNA was performed in MCF‐7 (ER‐positive) and MDA‐MB‐231 cells (ER‐ negative). A co‐expression network was then built using co‐expression relationships of the differentially expressed mRNAs and lncRNAs. Finally, the selected miRNA–mRNA network was added to the network. The key miRNA–mRNA–lncRNA interaction can be inferred from the network. The mRNA and non‐coding RNA expression profiles of the cells with different ER phenotypes were distinct. Among the aberrantly expressed miRNAs, the expression levels of miR‐19a‐3p, miR‐19b‐3p and miR‐130a‐3p were much lower in the MCF‐7 cells, whereas that of miR‐148b‐3p was much higher. In a cluster of miR‐17‐92, the expression levels of six of seven miRNAs were lower in the MCF‐7 cells, in addition to miR‐20b in the miR‐106a‐363 cluster. However, the levels of all the miRNAs in the miR‐106a‐25 cluster were higher in the MCF‐7 cells. In the co‐expression networking, CD74 and FMNL2 gene which is involved in the immune response and metastasis, respectively, had a stronger correlation with ER. Among the aberrantly expressed lncRNAs, lncRNA‐DLEU1 was highly expressed in the MCF‐7 cells. A statistical analysis revealed that there was a co‐expression relationship between ESR1 and lncRNA‐DLEU1. In addition, miR‐19a and lncRNA‐DLEU1 are both located on the human chromosome 13q. We speculate that miR‐19a might be co‐expressed with lncRNA‐DLEU1 to co‐regulate the expression of ESR1, which influences the occurrence and development of breast cancer cells with different levels of ER expression. Our findings reveal that the status of ER is mainly due to the differences in the mRNA and ncRNA profile between the breast cancer cell lines, and highlight the importance of studying the miRNA–mRNA–lncRNA interactions to completely illustrate the intricate transcriptome.

Essential role of miR-200c in regulating self-renewal of breast cancer stem cells and their counterparts of mammary epithelium

Background

Breast cancer stem cells (BCSCs) have been reported as the origin of breast cancer and the radical cause of drug resistance, relapse and metastasis in breast cancer. BCSCs could be derived from mutated mammary epithelial stem cells (MaSCs). Therefore, comparing the molecular differences between BCSCs and MaSCs may clarify the mechanism underlying breast carcinogenesis and the targets for gene therapy. Specifically, the distinct miRNome data of BCSCs and MaSCs need to be analyzed to find out the key miRNAs and reveal their roles in regulating the stemness of BCSCs.

Methods

MUC1⁻ESA⁺ cells were isolated from normal mammary epithelial cell line MCF-10A by fluorescence-activated cell sorting (FACS) and tested for stemness by clonogenic assay and multi-potential differentiation experiments. The miRNA profiles of MaSCs, BCSCs and breast cancer MCF-7 cells were compared to obtain the candidate miRNAs that may regulate breast tumorigenesis. An miRNA consecutively upregulated from MaSCs to BCSCs to MCF-7 cells, miR-200c, was chosen to determine its role in regulating the stemness of BCSCs and MaSCs in vitro and in vivo. Based on bioinformatics, the targets of miR-200c were validated by dual-luciferase report system, western blot and rescue experiments.

Results

In a 2-D clonogenic assay, MUC1⁻ESA⁺ cells gave rise to multiple morphological colonies, including luminal colonies, myoepithelial colonies and mixed colonies. The clonogenic potential of MUC1⁻ESA⁺ (61.5 ± 3.87 %) was significantly higher than that of non-stem MCF-10A cells (53.5 ± 3.42 %) (P < 0.05). In a 3-D matrigel culture, MUC1⁻ESA⁺ cells grew into mammospheres with duct-like structures. A total of 12 miRNAs of interest were identified, 8 of which were upregulated and 4 downregulated in BCSCs compared with MaSCs. In gain- and lost-of-function assays, miR-200c was sufficient to inhibit the self-renewal of BCSCs and MaSCs in vitro and the growth of BCSCs in vivo. Furthermore, miR-200c negatively regulated programmed cell death 10 (PDCD10) in BCSCs and MaSCs. PDCD10 could rescue the tumorigenesis inhibited by miR-200c in BCSCs.

Discussion

Accumulating evidence shows that there is a milignant transformation from MaSCs into BCSCs. The underlying mechanism remains unclear. In present study, miRNA profiles between MaSCs and BCSCs were obtained. Then miRNA-200c, downregulated in both MaSCs and BCSCs, were verified as anti-oncogene, and played essential role in regulating self-renewal of both kinds of stem-like cells. These findings reveal a novel insights of breast tumorigenesis.

Conclusions

PDCD10 is a target gene of miR-200c and also a possible mechanism by which miR-200c plays a role in regulating the stemness of BCSCs and MaSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1655-5) contains supplementary material, which is available to authorized users.

Down-regualtion of miR-106b induces epithelial-mesenchymal transition but suppresses metastatic colonization by targeting Prrx1 in colorectal cancer

Accumulating evidence identified that epithelial-mesenchymal transition (EMT) is acquired during progression to metastatic, but whether it is an absolute requirement is still controversial. MiR-106b has been confirmed to promote cancer cell proliferation; however few studies are available on its functions in EMT and metastasis in colorectal cancer (CRC). In this study, we found that knocking down miR-106b induced EMT conferring migratory and invasive properties. MiR-106b knockdown induced cytoskeletal reorganization through staining intracellular F-actin. The expression of Rho GTPases (Rac1 and Cdc42) and Tiam1 was significantly enforced after miR-106b down-regulation. However, miR-106b knocking down could suppress metastatic colonization in vivo. Correspondingly, over expression of miR-106b obtained an opposite effect. We identified Prrx1 was a direct target of miR-106b through using target prediction algorithms and dual-Luciferase reporter assay. Moreover, Moreover, we also found TGF-β1 could down-regulate miR-106b, and simultaneously miR-106b also influences the expression of TGF-β1, establishing a negative feedback loop to regulate the expression of Prrx1 together. Taken together, these findings demonstrated that miR-106b knockdown could induce EMT which conferring cells migratory and invasive properties but could not accomplish distant metastatic colonization efficiently.

Selective targeting of KRAS-mutant cells by miR-126 through repression of multiple genes essential for the survival of KRAS-mutant cells

MicroRNAs (miRNAs) regulate the expression of hundreds of genes. However, identifying the critical targets within a miRNA-regulated gene network is challenging. One approach is to identify miRNAs that exert a context-dependent effect, followed by expression profiling to determine how specific targets contribute to this selective effect. In this study, we performed miRNA mimic screens in isogenic KRAS-Wild-type (WT) and KRAS-Mutant colorectal cancer (CRC) cell lines to identify miRNAs selectively targeting KRAS-Mutant cells. One of the miRNAs we identified as a selective inhibitor of the survival of multiple KRAS-Mutant CRC lines was miR-126. In KRAS-Mutant cells, miR-126 over-expression increased the G1 compartment, inhibited clonogenicity and tumorigenicity, while exerting no effect on KRAS-WT cells. Unexpectedly, the miR-126-regulated transcriptome of KRAS-WT and KRAS-Mutant cells showed no significant differences. However, by analyzing the overlap between miR-126 targets with the synthetic lethal genes identified by RNAi in KRAS-Mutant cells, we identified and validated a subset of miR-126-regulated genes selectively required for the survival and clonogenicity of KRAS-Mutant cells. Our strategy therefore identified critical target genes within the miR-126-regulated gene network. We propose that the selective effect of miR-126 on KRAS-Mutant cells could be utilized for the development of targeted therapy for KRAS mutant tumors.

Therapeutic Opportunities for Targeting microRNAs in Cancer

MicroRNAs (miRNAs) are small noncoding RNAs that can function as either powerful tumor promoters or suppressors in numerous types of cancer. The ability of miRs to target multiple genes and biological signaling pathways has created intense interest in their potential clinical utility as predictive and diagnostic biomarkers, and as innovative therapeutic agents. Recently, accumulating preclinical studies have illustrated the feasibility of slowing tumor progression by either overexpressing tumor suppressive miRNAs, or by neutralizing the activities of oncogenic miRNAs in cell- and animal-based models of cancer. Here we highlight prominent miRNAs that may represent potential therapeutic targets in human malignancies, as well as review current technologies available for inactivating or restoring miRNA activity in clinical settings.

MiR-1228 promotes breast cancer cell growth and metastasis through targeting SCAI protein

Breast cancer is the most common cancer in women around the world. However, the molecular mechanisms underlying breast cancer pathogenesis are only partially understood. Here, in this study, we found that miR-1228 was up-regulated in breast cancer cell lines and tissues. Ectopic expression of miR-1228 mimics leads to promoted cell growth, invasion and migration. Using bioinfomatic analysis and 3'UTR luciferase reporter assay, we determined SCAI can be directly targeted by miR-1228, which can down-regulate endogenous SCAI protein level. Furthermore, our findings demonstrate that SCAI was down-regulated in breast cancer cell lines and tissues. Rescue experiment demonstrated that miR-1228 promoted cell growth is attenuated by over-expression of MOAP1 and miR-1228 promoted cell invasion and migration can be attenuated by over-expression of SCAI. Taken together, this study provides evidences that miR-1228 serves as an oncogene to promote breast cancer proliferation, invasion and migration, which may become a critical therapeutic target for breast cancer treatment.

miR-200c/Bmi1 axis and epithelial-mesenchymal transition contribute to acquired resistance to BRAF inhibitor treatment

Resistance to BRAF inhibitors (BRAFi) is one of the major challenges for targeted therapies for BRAF-mutant melanomas. However, little is known about the role of microRNAs in conferring BRAFi resistance. Herein, we demonstrate that miR-200c expression is significantly reduced whereas miR-200c target genes including Bmi1, Zeb2, Tubb3, ABCG5, and MDR1 are significantly increased in melanomas that acquired BRAFi resistance compared to pretreatment tumor biopsies. Similar changes were observed in BRAFi-resistant melanoma cell lines. Overexpression of miR-200c or knock-down of Bmi1 in resistant melanoma cells restores their sensitivities to BRAFi, leading to deactivation of the PI3K/AKT and MAPK signaling cascades, and acquisition of epithelial-mesenchymal transition-like phenotypes, including upregulation of E-cadherin, downregulation of N-cadherin, and ABCG5 and MDR1 expression. Conversely, knock-down of miR-200c or overexpression of Bmi1 in BRAFi-sensitive melanoma cells activates the PI3K/AKT and MAPK pathways, upregulates N-cadherin, ABCG5, and MDR1 expression, and downregulates E-cadherin expression, leading to BRAFi resistance. Together, our data identify miR-200c as a critical signaling node in BRAFi-resistant melanomas impacting the MAPK and PI3K/AKT pathways, suggesting miR-200c as a potential therapeutic target for overcoming acquired BRAFi resistance.

MicroRNA-200c-141 and ∆Np63 are required for breast epithelial differentiation and branching morphogenesis

The epithelial compartment of the breast contains two lineages, the luminal- and the myoepithelial cells. D492 is a breast epithelial cell line with stem cell properties that forms branching epithelial structures in 3D culture with both luminal- and myoepithelial differentiation. We have recently shown that D492 undergo epithelial to mesenchymal transition (EMT) when co-cultured with endothelial cells. This 3D co-culture model allows critical analysis of breast epithelial lineage development and EMT. In this study, we compared the microRNA (miR) expression profiles for D492 and its mesenchymal-derivative D492M. Suppression of the miR-200 family in D492M was among the most profound changes observed. Exogenous expression of miR-200c-141 in D492M reversed the EMT phenotype resulting in gain of luminal but not myoepithelial differentiation. In contrast, forced expression of ∆Np63 in D492M restored the myoepithelial phenotype only. Co-expression of miR-200c-141 and ∆Np63 in D492M restored the branching morphogenesis in 3D culture underlining the requirement for both luminal and myoepithelial elements for obtaining full branching morphogenesis in breast epithelium. Introduction of a miR-200c-141 construct in both D492 and D492M resulted in resistance to endothelial induced EMT. In conclusion, our data suggests that expression of miR-200c-141 and ∆Np63 in D492M can reverse EMT resulting in luminal- and myoepithelial differentiation, respectively, demonstrating the importance of these molecules in epithelial integrity in the human breast.

The emerging molecular machinery and therapeutic targets of metastasis

Metastasis is a 100-year-old research topic. Technological advances during the past few decades have led to significant progress in our understanding of metastatic disease. However, metastasis remains the leading cause of cancer-related mortalities. The lack of appropriate clinical trials for metastasis preventive drugs and incomplete understanding of the molecular machinery are major obstacles in metastasis prevention and treatment. Numerous processes, factors, and signaling pathways are involved in regulating metastasis. Here we discuss recent progress in metastasis research, including epithelial-mesenchymal plasticity, cancer stem cells, emerging molecular determinants and therapeutic targets, and the link between metastasis and therapy resistance.

Circulating miR-200c and miR-141 and outcomes in patients with breast cancer

Background

The deregulation of microRNAs in both tumours and blood has led to the search for microRNAs to indicate the presence of cancer and predict prognosis. We hypothesize the deregulation of miR-200c/miR-141 in the whole blood can identify breast cancer (BC), and could be developed into a prognostic signature.

Methods

The expression of miR-200c and miR-141 were examined in bloods (57 stage I-IV BC patients and 20 age-matched controls) by quantitative reverse-transcription PCR. The associations of circulating microRNAs with clinic and pathological characteristics were analysed. Their effects on survival were analysed by the Kaplan-Meier method and Cox regressions.

Results

MiR-200c was down regulated (P < 0.0001) in the blood of BC patients, yielded an area under the ROC curve of 0.79 (90% sensitivity, 70.2% specificity) in discriminating BC from controls. Circulating miR-141 was not discriminating. MiR-200c and miR-141 in the blood of BC patients were inversely correlated (P = 0.019). The miR-200c levels were numerically higher in stage IV and tumours with lower MIB-1. MiR-141 was significantly higher in the blood of patients with stage I-III, lymph node metastasis, and HER2 negative tumours. High blood expression of miR-200c and/or low expression of miR-141 was associated with unfavourable overall survival (hazard ratio, 3.89; [95% CI: 1.28-11.85]) and progression-free survival (3.79 [1.41–10.16]) independent of age, stage and hormonal receptors.

Conclusions

Circulating miR-200c and miR-141 were deregulated in BC comparing with controls. Furthermore, miR-200c and miR-141 were independent prognostic factors and associated with distinct outcomes of BC patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1238-5) contains supplementary material, which is available to authorized users.

miR-200a inhibits tumor proliferation by targeting AP-2γ in neuroblastoma cells

BACKGROUND

MicroRNA-200a (miR-200a) has been reported to regulate tumour progression in several tumours but little is known about its role in neuroblastoma. Our aim was to investigate the potential role and mechanism of miR-200a in neuroblastomas.

MATERIALS AND METHODS

Expression levels of miR-200a in tissues were determined using RT-PCR. The effect of miR-200a and shAP-2γ on cell viability was evaluated using MTS assays, and target protein expression was determined using Western blotting and RT-PCR. Luciferase reporter plasmids were constructed to confirm direct targeting. RESULTS were reported as mean±S.E.M and differences were tested for significance using the 2-tailed Students t-test.

RESULTS

We determined that miR-200a expression was significantly lower in neuroblastoma tumors than the adjacent non-cancer tissue. Over-expression of miR-200 are reduced cell viability in neuroblastoma cells and inhibited tumor growth in mouse xenografts. We identified AP-2γ as a novel target for miR-200a in neuroblastoma cells. Thus miR-200a targets the 3'UTR of AP-2γ and inhibits its mRNA and protein expression. Furthermore, our result showed that shRNA knockdown of AP-2γ in neuroblastoma cells results in significant inhibit of cell proliferation and tumor growth in vitro, supporting an oncogenic role of AP-2γ in neuroblastoma.

CONCLUSIONS

Our study revealed that miR-200a is a candidate tumor suppressor in neuroblastoma, through direct targeting of AP-2γ. These findings re-enforce the proposal of AP-2γ as a therapeutic target in neuroblastoma.

Regulation of miRNA processing and miRNA mediated gene repression in cancer

The majority of human protein-coding genes are predicted to be targets of miRNA-mediated post-transcriptional regulation. The widespread influence of miRNAs is illustrated by their essential roles in all biological processes. Regulated miRNA expression is essential for maintaining cellular differentiation; therefore alterations in miRNA expression patterns are associated with several diseases, including various cancers. High-throughput sequencing technologies revealed low level expressing miRNA isoforms, termed isomiRs. IsomiRs may differ in sequence, length, target preference and expression patterns from their parental miRNA and can arise from differences in miRNA biosynthesis, RNA editing, or SNPs inherent to the miRNA gene. The association between isomiR expression and disease progression is largely unknown. Misregulated miRNA expression is thought to contribute to the formation and/or progression of cancer. However, due to the diversity of targeted transcripts, miRNAs can function as both tumor-suppressor genes and oncogenes as defined by cellular context. Despite this, miRNA profiling studies concluded that the differential expression of particular miRNAs in diseased tissue could aid the diagnosis and treatment of some cancers.

The Regulatory Role of MicroRNAs in EMT and Cancer

The epithelial to mesenchymal transition (EMT) is a powerful process in tumor invasion, metastasis, and tumorigenesis and describes the molecular reprogramming and phenotypic changes that are characterized by a transition from polarized immotile epithelial cells to motile mesenchymal cells. It is now well known that miRNAs are important regulators of malignant transformation and metastasis. The aberrant expression of the miR-200 family in cancer and its involvement in the initiation and progression of malignant transformation has been well demonstrated. The metastasis suppressive role of the miR-200 members is strongly associated with a pathologic EMT. This review describes the most recent advances regarding the influence of miRNAs in EMT and the control they exert in major signaling pathways in various cancers. The ability of the autocrine TGF-β/ZEB/miR-200 signaling regulatory network to control cell plasticity between the epithelial and mesenchymal state is further discussed. Various miRNAs are reported to directly target EMT transcription factors and components of the cell architecture, as well as miRNAs that are able to reverse the EMT process by targeting the Notch and Wnt signaling pathways. The link between cancer stem cells and EMT is also reported and the most recent developments regarding clinical trials that are currently using anti-miRNA constructs are further discussed.

miR-200 promotes the mesenchymal to epithelial transition by suppressing multiple members of the Zeb2 and Snail1 transcriptional repressor complexes

The miR-200 family promotes the epithelial state by suppressing the Zeb1/Zeb2 epithelial gene transcriptional repressors. To identify other miR-200-regulated genes, we isolated mRNAs bound to transfected biotinylated miR-200c in mouse breast cancer cells. In all, 520 mRNAs were significantly enriched in miR-200c binding at least twofold. Putative miR-200-regulated genes included Zeb2, enriched 3.5-fold in the pull down. However, Zeb2 knockdown does not fully recapitulate miR-200c overexpression, suggesting that regulating other miR-200 targets contributes to miR-200's enhancement of epithelial gene expression. Candidate genes were highly enriched for miR-200c seed pairing in their 3'UTR and coding sequence and for genes that were downregulated by miR-200c overexpression. Epidermal growth factor receptor and downstream MAPK signaling pathways were the most enriched pathways. Genes whose products mediate transforming growth factor (TGF)-β signaling were also significantly overrepresented, and miR-200 counteracted the suppressive effects of TGF-β and bone morphogenic protein 2 (BMP-2) on epithelial gene expression. miR-200c regulated the 3'UTRs of 12 of 14 putative miR-200c-binding mRNAs tested. The extent of mRNA binding to miR-200c strongly correlated with gene suppression. Twelve targets of miR-200c (Crtap, Fhod1, Smad2, Map3k1, Tob1, Ywhag/14-3-3γ, Ywhab/14-3-3β, Smad5, Zfp36, Xbp1, Mapk12, Snail1) were experimentally validated by identifying their 3'UTR miR-200 recognition elements. Smad2 and Smad5 form a complex with Zeb2 and Ywhab/14-3-3β and Ywhag/14-3-3γ form a complex with Snail1. These complexes that repress transcription assemble on epithelial gene promoters. miR-200 overexpression induced RNA polymerase II localization and reduced Zeb2 and Snail1 binding to epithelial gene promoters. Expression of miR-200-resistant Smad5 modestly, but significantly, reduced epithelial gene induction by miR-200. miR-200 expression and Zeb2 knockdown are known to inhibit cell invasion in in vitro assays. Knockdown of each of three novel miR-200 target genes identified here, Smad5, Ywhag and Crtap, also profoundly suppressed cell invasion. Thus, miR-200 suppresses TGF-β/BMP signaling, promotes epithelial gene expression and suppresses cell invasion by regulating a network of genes.

Expression of miR-200c in claudin-low breast cancer alters stem cell functionality, enhances chemosensitivity and reduces metastatic potential

Claudin-low tumors are a highly aggressive breast cancer subtype with no targeted treatments and a clinically documented resistance to chemotherapy. They are significantly enriched in cancer stem cells (CSCs), which makes claudin-low tumor models particularly attractive for studying CSC behavior and developing novel approaches to minimize CSC therapy resistance. One proposed mechanism by which CSCs arise is via an epithelial-mesenchymal transition (EMT), and reversal of this process may provide a potential therapeutic approach for increasing tumor chemosensitivity. Therefore, we investigated the role of known EMT regulators, miR-200 family of microRNAs in controlling the epithelial state, stem-like properties, and therapeutic response in an in vivo primary, syngeneic p53^null claudin-low tumor model that is normally deficient in miR-200 expression. Using an inducible lentiviral approach, we expressed the miR-200c cluster in this model and found that it changed the epithelial state, and consequently, impeded CSC behavior in these mesenchymal tumors. Moreover, these state changes were accompanied by a decrease in proliferation and an increase in the differentiation status. miR-200c expression also forced a significant reorganization of tumor architecture, affecting important cellular processes involved in cell-cell contact, cell adhesion, and motility. Accordingly, induced miR200c expression significantly enhanced the chemosensitivity and decreased the metastatic potential of this p53^null claudin-low tumor model. Collectively, our data suggest that miR-200c expression in claudin-low tumors offers a potential therapeutic application to disrupt the EMT program on multiple fronts in this mesenchymal tumor subtype, by altering tumor growth, chemosensitivity, and metastatic potential in vivo.

A summary for molecular regulations of miRNAs in breast cancer

BACKGROUND

Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer-related death among women worldwide. MicroRNAs (miRNAs) are naturally-occurring, non-coding small RNA molecules that can modulate protein coding-genes, which makes it contributing to nearly all the physiological and pathological processes. Progression of breast cancer and resistance to endocrine therapies have been attributed to the possibility of hormone-responsive miRNAs involved in the regulation of certain signaling pathways.

METHODOLOGY

This review introduces better understanding of miRNAs to provide promising advances for treatment. miRNAs have multiple targets, and they were found to regulate different signaling pathways; consequently it is important to characterize their mechanisms of action and their cellular targets in order to introduce miRNAs as novel and promising therapies.

RESULTS

This review summarizes the molecular mechanisms of miRNAs in TGF-beta signaling, apoptosis, metastasis, cell cycle, ER-signaling, and drug resistance.

CONCLUSION

Finally, miRNAs will be introduced as promising molecules to be used in the fight against breast cancer and its developed drug resistance.

Epigenetic modulation and repression of miR-200b by cancer-associated fibroblasts contribute to cancer invasion and peritoneal dissemination in gastric cancer

Cancer-associated fibroblasts (CAFs) have recently been linked to the invasion and metastasis of gastric cancer. In addition, the microRNA (miR)-200 family plays a central role in the regulation of the epithelial-mesenchymal transition process during cancer metastasis, and aberrant DNA methylation is one of the key mechanisms underlying regulation of the miR-200 family. In this study, we clarified whether epigenetic changes of miR-200b by CAFs stimulate cancer invasion and peritoneal dissemination in gastric cancer. We evaluated the relationship between miR-200b and CAFs using a coculture model. In addition, we established a peritoneal metastasis mouse model and investigated the expression and methylation status of miR-200b. We also investigated the expression and methylation status of miR-200b and CAFs expression in primary gastric cancer samples. CAFs (CAF-37 and CAF-50) contributed to epigenetic changes of miR-200b, reduced miR-200b expression and promoted tumor invasion and migration in NUGC3 and OCUM-2M cells in coculture. In the model mice, epigenetic changes of miR-200b were observed in the inoculated high-frequency peritoneal dissemination cells. In the 173 gastric cancer samples, the low miR-200b expression group demonstrated a significantly poorer prognosis compared with the high miR-200b expression group and was associated with peritoneal metastasis. In addition, downregulation of miR-200b in cancer cells was significantly correlated with alpha-smooth muscle actin expression. Our data provide evidence that CAFs reduce miR-200b expression and promote tumor invasion through epigenetic changes of miR-200b in gastric cancer. Thus, CAFs might be a therapeutic target for inhibition of gastric cancer.

miR-200-containing extracellular vesicles promote breast cancer cell metastasis

Metastasis is associated with poor prognosis in breast cancer patients. Not all cancer cells within a tumor are capable of metastasizing. The microRNA-200 (miR-200) family, which regulates the mesenchymal-to-epithelial transition, is enriched in the serum of patients with metastatic cancers. Ectopic expression of miR-200 can confer metastatic ability to poorly metastatic tumor cells in some settings. Here, we investigated whether metastatic capability could be transferred between metastatic and nonmetastatic cancer cells via extracellular vesicles. miR-200 was secreted in extracellular vesicles from metastatic murine and human breast cancer cell lines, and miR-200 levels were increased in sera of mice bearing metastatic tumors. In culture, murine and human metastatic breast cancer cell extracellular vesicles transferred miR-200 microRNAs to nonmetastatic cells, altering gene expression and promoting mesenchymal-to-epithelial transition. In murine cancer and human xenograft models, miR-200-expressing tumors and extracellular vesicles from these tumors promoted metastasis of otherwise weakly metastatic cells either nearby or at distant sites and conferred to these cells the ability to colonize distant tissues in a miR-200-dependent manner. Together, our results demonstrate that metastatic capability can be transferred by the uptake of extracellular vesicles.

Special delivery: microRNA-200-containing extracellular vesicles provide metastatic message to distal tumor cells

An emerging view is that breast cancer is a systemic disease that utilizes intrinsic and extrinsic tumor cell processes to support both primary tumor growth and metastatic dissemination into distal tissue. Delineation of factors involved in these processes should facilitate a better understanding for both assessing and preventing disease relapse. In this issue of the JCI, Le et al. investigate whether intrinsic properties of metastatic breast cancer cell growth can be regulated through an extrinsic process--contact with tumor cell-derived extracellular vesicles containing microRNAs of the miR-200 family. The authors provide compelling evidence that miR-200s within extracellular vesicles secreted from highly metastatic tumor cells can be internalized by weakly metastatic cells. Thus, internalization and delivery of this metastatic "donor" cell-derived message provide plausible mechanisms by which oncogenic and regulatory factors confer the capability of tumor growth at metastatic lesions. This study provides a strong rationale for detailed assessment of the prognostic and predictive value of circulating extracellular vesicle-bound miR-200s in breast cancer progression and treatment.

Regulation of cancer metastasis by cell-free miRNAs

MicroRNAs (miRNAs) are integral molecules in the regulation of numerous physiological cellular processes that have emerged as critical players in cancer initiation and metastatic progression, both by promoting and suppressing metastasis. Recently, cell-free miRNAs shed from cancer cells into circulation have been reported in cancer patients, raising hope for development of novel biomarkers that can be routinely measured in easily accessible samples. In fact, establishing miRNA expression in the circulation likely has advantages over determination in primary tumor tissue, further augmenting the potential applications of miRNA detection in oncological practice. In addition, secretion of miRNAs impacting distant cell signaling or promoting the formation of a niche that sustains a distant tumor microenvironment allows for new treatment approaches to thwart cancer progression.

MicroRNA-200b targets protein kinase Cα and suppresses triple-negative breast cancer metastasis

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with poor prognosis and lacks effective targeted therapies. The microRNA-200 (miR-200) family is found to inhibit or promote breast cancer metastasis; however, the underlying mechanism is not well understood. This study was performed to investigate the effect and mechanism of miR-200b on TNBC metastasis and identify targets for developing more efficient treatment for TNBC. We found that miR-200 family expression levels are significantly lower in highly migratory TNBC cells and metastatic TNBC tumors than other types of breast cancer cells and tumors. Ectopically expressing a single member (miR-200b) of the miR-200 family drastically reduces TNBC cell migration and inhibits tumor metastasis in an orthotopic mouse mammary xenograft tumor model. We identified protein kinase Cα (PKCα) as a new direct target of miR-200b and found that PKCα protein levels are inversely correlated with miR-200b levels in 12 kinds of breast cancer cells. Inhibiting PKCα activity or knocking down PKCα levels significantly reduces TNBC cell migration. In contrast, forced expression of PKCα impairs the inhibitory effect of miR-200b on cell migration and tumor metastasis. Further mechanistic studies revealed that PKCα downregulation by miR-200b results in a significant decrease of Rac1 activation in TNBC cells. These results show that loss of miR-200b expression plays a crucial role in TNBC aggressiveness and that miR-200b suppresses TNBC cell migration and tumor metastasis by targeting PKCα. Our findings suggest that miR-200b and PKCα may serve as promising therapeutic targets for metastatic TNBC.

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

Cancer is a multistep disease that begins with malignant cell transformation and frequently culminates in metastasis. MicroRNAs (miRNAs) are small regulatory 21-25 nt RNA molecules and are frequently deregulated in cancer. miR-200a is a member of the miR-200 family, which are known inhibitors of the epithelial-to-mesenchymal transition. As such, the tumor-suppressive role of miR-200a in oncogenesis has been well documented; however, recent studies have found a proliferative role for this miRNA as well as a prometastatic role in the later steps of cancer progression. Little is known about the role of this miRNA in the early stages of cancer, namely, malignant cell transformation. Here, we show that miR-200a alone transforms an immortalized rat epithelial cell line, and miR-200a cooperates with Ras to enhance malignant transformation of an immortalized human epithelial cell line. Furthermore, miR-200a induces cell transformation and tumorigenesis in immunocompromised mice by cooperating with a Ras mutant that activates only the RalGEF effector pathway, but not Ras mutants activating PI3K or Raf effector pathways. This transformative ability is in accordance with miR-200a targeting Fog2 and p53 to activate Akt and directly repress p53 protein levels, respectively. These results demonstrate an oncogenic role for miR-200a and provide a specific cellular context where miR-200a acts as an oncomiR rather than a tumor suppressor by cooperating with an oncogene in malignant cell transformation.

Functional Role of the microRNA-200 Family in Breast Morphogenesis and Neoplasia

Branching epithelial morphogenesis is closely linked to epithelial-to-mesenchymal transition (EMT), a process important in normal development and cancer progression. The miR-200 family regulates epithelial morphogenesis and EMT through a negative feedback loop with the ZEB1 and ZEB2 transcription factors. miR-200 inhibits expression of ZEB1/2 mRNA, which in turn can down-regulate the miR-200 family that further results in down-regulation of E-cadherin and induction of a mesenchymal phenotype. Recent studies show that the expression of miR-200 genes is high during late pregnancy and lactation, thereby indicating that these miRs are important for breast epithelial morphogenesis and differentiation. miR-200 genes have been studied intensively in relation to breast cancer progression and metastasis, where it has been shown that miR-200 members are down-regulated in basal-like breast cancer where the EMT phenotype is prominent. There is growing evidence that the miR-200 family is up-regulated in distal breast metastasis indicating that these miRs are important for colonization of metastatic breast cancer cells through induction of mesenchymal to epithelial transition. The dual role of miR-200 in primary and metastatic breast cancer is of interest for future therapeutic interventions, making it important to understand its role and interacting partners in more detail.

Distinct pattern of chromosomal alterations and pathways in tongue and cheek squamous cell carcinoma

BACKGROUND

The purpose of this study was to investigate the cause of behavioral difference between tongue and cheek squamous cell carcinomas (SCCs) by verifying the copy number alterations (CNAs).

METHODS

Array comparative genomic hybridization (aCGH) was used to profile unique deletions and amplifications that are involved with tongue and cheek SCC, respectively. This was followed by pathway analysis relating to CNA genes from both sites.

RESULTS

The most frequently amplified regions in tongue SCC were 4p16.3, 11q13.4, and 13q34; whereas the most frequently deleted region was 19p12. For cheek SCC, the most frequently amplified region was identified on chromosome 9p24.1-9p23; whereas the most common deleted region was located on chromosome 8p23.1. Further analysis revealed that the most significant unique pathway related to tongue and cheek SCCs was the cytoskeleton remodeling and immune response effect on the macrophage differentiation pathway.

CONCLUSION

This study has showed the different genetic profiles and biological pathways between tongue and cheek SCCs. © 2013 Wiley Periodicals, Inc. Head Neck 36: 1268-1278, 2014.

miRNA expression in anaplastic thyroid carcinomas

Anaplastic thyroid carcinoma (ATC) is the most lethal form of thyroid neoplasia and represents an end stage of thyroid tumor progression. No effective treatment exists so far. In this study, we analyzed the miRNA expression profiles of 11 ATC by microarrays and their relationship with the mRNA expression profiles of the same 11 ATC samples. ATC show distinct miRNA expression profiles compared to other less aggressive thyroid tumor types. ATC show 18 commonly deregulated miRNA compared to normal thyroid tissue (17 downregulated and 1 upregulated miRNA). First, the analysis of a combined approach of the mRNA gene expression and of the bioinformatically predicted mRNA targets of the deregulated miRNA suggested a role for these regulations in the epithelial to mesenchymal transition (EMT) process in ATC. Second, the direct interaction between one of the upregulated mRNA target, the LOX gene which is an EMT key player, and a downregulated miRNA, the miR-29a, was experimentally validated by a luciferase assay in HEK cell. Third, we confirmed that the ATC tissue is composed of about 50% of tumor associated macrophages (TAM) and suggested, by taking into account our data and published data, their most likely direct or paracrine intercommunication between them and the thyroid tumor cells, amplifying the tumor aggressiveness. Finally, we demonstrated by in situ hybridization a specific thyrocyte localization of 3 of the deregulated miRNA: let-7g, miR-29a and miR-30e and we pointed out the importance of identifying the cell type localization before drawing any conclusion on the physiopathological role of a given gene.

miR-141 and miR-200c as markers of overall survival in early stage non-small cell lung cancer adenocarcinoma

Background

Several treatments in non-small cell lung cancer (NSCLC) are histology-dependent, and the need for histology-related markers is increasing. MicroRNAs (miRNAs) are promising molecular markers in multiple cancers and show differences in expression depending on histological subtype. The miRNA family miR-200 has been associated with the regulation of epithelial-mesenchymal (EMT)/mesenchymal-epithelial transition (MET). EMT involves profound phenotypic changes that include the loss of cell-cell adhesion, the loss of cell polarity, and the acquisition of migratory and invasive properties that facilitates metastasis. A dual role for the miR-200 family in the prognosis of several tumors has been related to tumor cell origin. However, the prognostic role and function of miR-200 family in early-stage NSCLC adenocarcinoma and squamous cell carcinoma (SCC) have not been well established.

Methods

miRNA expression was determined using TaqMan assays in 155 tumors from resected NSCLC patients. Functional studies were conducted in three NSCLC cell lines: H23, A-549 and HCC-44.

Results

High miR-200c expression was associated with shorter overall survival (OS) in the entire cohort (p = 0.024). High miR-200c (p = 0.0004) and miR-141 (p = 0.009) expression correlated with shorter OS in adenocarcinoma – but not in SCC. In the multivariate analysis, a risk score based on miR-141 and miR-200c expression emerged as an independent prognostic factor for OS in the entire cohort (OR, 2.787; p = 0.033) and in adenocarcinoma patients (OR, 10.649; p = 0.002). Functional analyses showed that miR-200c, was related to mesenchymal-epithelial transition (MET) and affected cell migration and E-cadherin levels, while overexpression of miR-141 reduced KLF6 protein levels and produced an increase of secretion of VEGFA in vitro (H23, p = 0.04; A-549, p = 0.03; HCC-44, p = 0.02) and was associated with higher blood microvessel density in patient tumor samples (p<0.001).

Conclusion

High miR-141 and miR-200c expression are associated with shorter OS in NSCLC patients with adenocarcinoma through MET and angiogenesis.

Cellular migration and invasion uncoupled: increased migration is not an inexorable consequence of epithelial-to-mesenchymal transition

Metastatic dissemination requires carcinoma cells to detach from the primary tumor and invade through the basement membrane. To acquire these characteristics, epithelial tumor cells undergo epithelial-to-mesenchymal transitions (EMT), whereby cells lose polarity and E-cadherin-mediated cell-cell adhesion. Post-EMT cells have also been shown, or assumed, to be more migratory; however, there have been contradictory reports on an immortalized human mammary epithelial cell line (HMLE) that underwent EMT. In the context of carcinoma-associated EMT, it is not yet clear whether the change in migration and invasion must be positively correlated during EMT or whether enhanced migration is a necessary consequence of having undergone EMT. Here, we report that pre-EMT rat prostate cancer (PC) and HMLE cells are more migratory than their post-EMT counterparts. To determine a mechanism for increased epithelial cell migration, gene expression analysis was performed and revealed an increase in epidermal growth factor receptor (EGFR) expression in pre-EMT cells. Indeed, inhibition of EGFR in PC epithelial cells slowed migration. Importantly, while post-EMT PC and HMLE cell lines are less migratory, both remain invasive in vitro and, for PC cells, in vivo. Our study demonstrates that enhanced migration is not a phenotypic requirement of EMT, and migration and invasion can be uncoupled during carcinoma-associated EMT.

Towards a molecular basis of oligometastatic disease: potential role of micro-RNAs

Oligometastasis is a cancer disease state characterized by a limited number of metastatic tumors involving single or few organs and with biological properties that make them potentially amenable to locoregional antitumor therapy. Current clinical data show that they are potentially curable with surgical resection or/and radiotherapy. Yet, mechanisms of progression from primary tumor to oligometastasis, rather than to polymetastases, is lacking in detail. In the current review we focus on the role of micro-RNAs in the regulation of metastases development and the role they may play in the differentiation of oligometastatic from polymetastatic progression. We also discuss the analyses of metastatic samples from oligo-and polymetastatic patients, which suggest that oligometastasis is a distinct biologic entity regulated in part by micro-RNAs. In addition, a review of the known functions of oligometastatic-specific micro-RNAs suggest that they regulate multiple steps in the metastatic cascade, including epithelial–mesenchymal transition, tumor invasion, intravasation, distant vascular extravasation and proliferation in a distant organ. Understanding the role of micro-RNAs and their target genes in oligometastatic disease may allow for the development of targeted therapies to effectively conrol the spread of metastases.

Epigenetic silencing of microRNA-203 is required for EMT and cancer stem cell properties

The epithelial-mesenchymal transition (EMT) imparts metastatic competence on otherwise non-metastatic cancer cells through decreased inter-cellular adhesions, increased migratory capacity, stem cell properties and anoikis and chemotherapy resistance. In this study, we profiled changes in microRNA expression during EMT in conjunction with changes in DNA methylation at microRNA promoters to discover essential mediators of EMT-imparted stemness properties. MicroRNA-203 (miR-203) expression is repressed following EMT induced by multiple different stimuli and in established claudin-low cell lines as well as the CD44hi/CD24lo stem cell-enriched fraction. Expression of miR-203 in mesenchymal cells compromises migratory and invasive capacity in vitro, and tumor initiation and metastasis in vivo. Unexpectedly, miR-203 expression affects the sphere-forming capacity of neighboring cells by indirectly enhancing expression of DKK1, a secreted inhibitor of Wnt signaling and stemness resulting in suppression of β-catenin protein levels. Our data suggest that restoring miR-203 expression levels may inhibit metastasis and combat deregulated Wnt signaling.

miR-141-3p inhibits human stromal (mesenchymal) stem cell proliferation and differentiation

Wnt signaling determines human stromal (mesenchymal) stem cell (hMSC) differentiation fate into the osteoblast or adipocyte lineage. microRNAs (miRNAs) are small RNA molecules of 21-25 nucleotides that regulate many aspects of osteoblast biology. Thus, we examined miRNAs regulated by Wnt signaling in hMSC. We identified miRNA (miR)-141-3p as a Wnt target which in turn inhibited Wnt signaling. Moreover, miR-141-3p inhibited hMSC proliferation by arresting cells at the G1 phase of the cell cycle. miR-141-3p inhibited osteoblast differentiation of hMSC as evidenced by reduced alkaline phosphatase activity, gene expression and in vitro mineralized matrix formation. Bioinformatic studies, Western blot analysis and 3'UTR reporter assay demonstrated that cell division cycle 25A (CDC25A) is a direct target of miR-141-3p. siRNA-mediated knock-down of CDC25A inhibited hMSC proliferation and osteoblast differentiation. In summary, miR-141-3p acts as a negative regulator of hMSC proliferation and osteoblast differentiation. Targeting miR-141-3p could be used as an anabolic therapy of low bone mass diseases, e.g. osteoporosis.

MicroRNA-200b targets protein kinase Cα and suppresses triple-negative breast cancer metastasis

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with poor prognosis and lacks effective targeted therapies. The microRNA-200 (miR-200) family is found to inhibit or promote breast cancer metastasis; however, the underlying mechanism is not well understood. This study was performed to investigate the effect and mechanism of miR-200b on TNBC metastasis and identify targets for developing more efficient treatment for TNBC. We found that miR-200 family expression levels are significantly lower in highly migratory TNBC cells and metastatic TNBC tumors than other types of breast cancer cells and tumors. Ectopically expressing a single member (miR-200b) of the miR-200 family drastically reduces TNBC cell migration and inhibits tumor metastasis in an orthotopic mouse mammary xenograft tumor model. We identified protein kinase Cα (PKCα) as a new direct target of miR-200b and found that PKCα protein levels are inversely correlated with miR-200b levels in 12 kinds of breast cancer cells. Inhibiting PKCα activity or knocking down PKCα levels significantly reduces TNBC cell migration. In contrast, forced expression of PKCα impairs the inhibitory effect of miR-200b on cell migration and tumor metastasis. Further mechanistic studies revealed that PKCα downregulation by miR-200b results in a significant decrease of Rac1 activation in TNBC cells. These results show that loss of miR-200b expression plays a crucial role in TNBC aggressiveness and that miR-200b suppresses TNBC cell migration and tumor metastasis by targeting PKCα. Our findings suggest that miR-200b and PKCα may serve as promising therapeutic targets for metastatic TNBC.

MicroRNAs related polymorphisms and genetic susceptibility to esophageal squamous cell carcinoma

Esophageal cancer (EC) is the sixth leading cause of cancer-associated death worldwide and the incidence and mortality in China are the highest. The single nucleotide polymorphisms (SNPs) related to microRNAs could lead to alteration in microRNA expression and contribute to the susceptibility of cancer. To evaluate the association between microRNA-related SNPs and EC, a case-control study including 381 patients with esophageal squamous cell carcinoma (ESCC) and 426 gender, age-matched controls was carried out to investigate the genetic susceptibility of five microRNA-related SNPs (rs2910164 in microRNA-146a, rs11614913 in microRNA-196a-2, rs7813 in GEMIN4, rs1595066 and rs16845990 in ErbB4) as well as the interactions of gene-gene and gene-environment in the development of ESCC. Variant homozygote genotype of rs11614913 in microRNA-196a-2 and rs1595066 in ErbB4 were significantly associated with reduced ESCC risk (OR(adjusted): 0.62, 95 % CI: 0.39-0.99 and OR(adjusted): 0.38, 95 % CI: 0.24-0.61). The analysis of haplotypes in ErbB4 gene showed significant increased ESCC risk in G(rs1595066)C(rs16845990) and G(rs1595066)T(rs16845990) haplotypes (OR(adjusted): 1.46, 95 % CI: 1.08-1.99 and OR(adjusted): 1.33, 95 % CI: 1.10-1.62), and inversely reduced ESCC risk in A(rs1595066)C(rs16845990) and A(rs1595066)T(rs16845990) haplotypes with OR (95 % CI) of 0.75 (0.60-0.94) and 0.65 (0.49-0.86), respectively. These findings suggest that the polymorphisms in the microRNA-related genes may affect susceptibility of ESCC in Chinese Han population and the gene-gene interactions play vital roles in the progression on esophageal cancer. Future studies with larger sample and different ethnic populations are required to support and validate our findings.

Micro-RNAs as clinical biomarkers and therapeutic targets in breast cancer: Quo vadis?

Breast cancer (BC) is the most frequent type of non skin cancer among women and a major leading cause of cancer-related deaths in Western countries. It is substantial to discover novel biomarkers with diagnostic, prognostic or predictive usefulness as well as therapeutic value for BC. Micro-RNAs (miRNAs) belong to a novel class of endogenous interfering RNAs that play a crucial role in post transcriptional gene silencing through mRNA targeting and, thus, are involved in many biological processes encompassing apoptosis, cell-cycle control, cell proliferation, DNA repair, immunity, metabolism, stress, aging, etc. MiRNAs exert their action mainly in a tumor suppressive or oncogenic manner. The specific aberrant expression patterns of miRNAs in BC that are detected with the use of high-throughput technologies reflect their key role in cancer initiation, progression, migration, invasion and metastasis. The detection of circulating extracellular miRNAs in plasma of BC patients may provide novel, non-invasive biomarkers in favor of BC diagnosis and prognosis and, at the same time, accumulating evidence has underscored the possible contribution of miRNAs as valuable biomarkers to predict response to chemotherapy or radiotherapy. Data from in vitro and in vivo studies on BC have revealed promising therapeutic approaches via miRNA delivery and miRNA inhibition. The purpose of this review is to explore the ontological role of miRNAs in BC etiopathogenesis as well as to highlight their potential, not only as non-invasive circulating biomarkers with diagnostic and prognostic significance, but also as treatment response predictors and therapeutic targets aiding BC management.

Small-sized polymeric micelles incorporating docetaxel suppress distant metastases in the clinically-relevant 4T1 mouse breast cancer model

BACKGROUND

The small size of ultra-small nanoparticles makes them suitable for lymphatic delivery, and many recent studies have examined their role in anti-metastasis therapy. However, the anti-metastatic efficacy of small-sized nanocarriers loaded with taxanes such as docetaxel has not yet been investigated in malignant breast cancer.

METHODS

We encapsulated docetaxel using poly(D,L-lactide)1300-b-(polyethylene glycol-methoxy)2000 (mPEG2000-b-PDLLA1300) to construct polymeric micelles with a mean diameter of 16.76 nm (SPM). Patient-like 4T1/4T1luc breast cancer models in Balb/c mice, with resected and unresected primary tumors, were used to compare the therapeutic efficacies of SPM and free docetaxel (Duopafei) against breast cancer metastasis using bioluminescent imaging, lung nodule examination, and histological examination.

RESULT

SPM showed similar efficacy to Duopafei in terms of growth suppression of primary tumors, but greater chemotherapeutic efficacy against breast cancer metastasis. In addition, lung tissue inflammation was decreased in the SPM-treated group, while many tumor cells and neutrophils were found in the Duopafei-treated group.

CONCLUSION

Small-sized mPEG2000-b-PDLLA1300 micelles could provide an enhanced method of docetaxel delivery in breast cancer metastasis, and may represent a valid chemotherapeutic strategy in breast cancer patients with resected primary tumors.

Tumour angiogenesis regulation by the miR-200 family

The miR-200 family is well known to inhibit the epithelial-mesenchymal transition, suggesting it may therapeutically inhibit metastatic biology. However, conflicting reports regarding the role of miR-200 in suppressing or promoting metastasis in different cancer types have left unanswered questions. Here we demonstrate a difference in clinical outcome based on miR-200's role in blocking tumour angiogenesis. We demonstrate that miR-200 inhibits angiogenesis through direct and indirect mechanisms by targeting interleukin-8 and CXCL1 secreted by the tumour endothelial and cancer cells. Using several experimental models, we demonstrate the therapeutic potential of miR-200 delivery in ovarian, lung, renal and basal-like breast cancers by inhibiting angiogenesis. Delivery of miR-200 members into the tumour endothelium resulted in marked reductions in metastasis and angiogenesis, and induced vascular normalization. The role of miR-200 in blocking cancer angiogenesis in a cancer-dependent context defines its utility as a potential therapeutic agent.

WITHDRAWN: MiR-200 family and cancer: Function, regulation and signaling

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