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

Loss of microRNA-200a expression correlates with tumor progression in breast cancer

MicroRNAs (miRNAs) are 19∼22 nucleotide-long, noncoding, small RNAs, involved in post-transcriptional regulation of many target genes. The miRNA-200 family has been shown to play a crucial role in the epithelial to mesenchymal transition in human cancers. In situ hybridization (ISH) was used to investigate the expression level of miRNA-200a in breast cancers. Formalin-fixed, paraffin embedded (FFPE) tissues from normal breast, ductal carcinoma in situ (DCIS), primary cancers, and metastatic lymph nodes were achieved and constructed to tissue microarrays. MiRNA-200a expression was demonstrated in 95.2% of normal breast tissue samples and 80.4% of DCIS, whereas 178 (58.0%) of 307 breast cancers and 83.3% of metastatic lymph node samples lacked miRNA-200a expression (P < 0.001). Moreover, loss of MiRNA-200a expression correlated with high histologic grade (P = 0.017) and perinodal tumor extension (P = 0.026). However, miRNA-200a expression did not predict tumor recurrence or patient survival. In conclusion, loss of miRNA-200a is frequently observed in breast cancers, especially tumors with high grade histology. These findings suggest that miRNA-200a may play an important role in breast cancer initiation and progression. ISH can be used to detect miRNAs in FFPE sections, and should permit the validation of miRNAs as biomarkers in large clinical samples.

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.

Insights into the epithelial mesenchymal transition phenotype in cancer of unknown primary from a global microRNA profiling study

PURPOSE

We sought to study the microRNA regulation of epithelial mesenchymal transition (EMT), the acquisition of migratory, mesenchymal-like properties of epithelial cells, in cancer of unknown primary (CUP).

PATIENTS AND METHODS

We studied the global expression profile of 982 microRNAs by means of microarray technology in 68 CUP cases immunohistochemically characterised as EMT-positive (n = 5 by % of cells or n = 10 by a semiquantitative H-score) or EMT-negative.

RESULTS

EMT-suppressive miRNAs such as miR-203 and members of the miR-200 family (miR-200a,b,c and miR-141) presented a 2.45 to 3.64-fold lower expression level in the EMT-positive cases without, however, reaching statistical significance. MiR-205, a squamous tissue-specific marker, was very variable in the data set. Excluding CUP cases with squamous cell histology, miR-205, miR-203 and the miR-200 family exhibited a trend of downregulation in EMT-positive cases. A similar pattern of miRNA expression was detected when the comparison took place between EMT-positive vs EMT-negative cases according to the H-score. Moreover, miR-203, miR-205 and miR-200c were numerically downregulated in those tumours with high expression of the EMT marker N-cadherin.

CONCLUSIONS

The EMT-suppressive miR-203 and miR-200 family were consistently but non-significantly downregulated in CUP with the EMT phenotype. A larger study is warranted to further explore the role of microRNAs in CUP.

Direct repression of MYB by ZEB1 suppresses proliferation and epithelial gene expression during epithelial-to-mesenchymal transition of breast cancer cells

INTRODUCTION

Epithelial-to-mesenchymal transition (EMT) promotes cell migration and is important in metastasis. Cellular proliferation is often downregulated during EMT, and the reverse transition (MET) in metastases appears to be required for restoration of proliferation in secondary tumors. We studied the interplay between EMT and proliferation control by MYB in breast cancer cells.

METHODS

MYB, ZEB1, and CDH1 expression levels were manipulated by lentiviral small-hairpin RNA (shRNA)-mediated knockdown/overexpression, and verified with Western blotting, immunocytochemistry, and qRT-PCR. Proliferation was assessed with bromodeoxyuridine pulse labeling and flow cytometry, and sulforhodamine B assays. EMT was induced with epidermal growth factor for 9 days or by exposure to hypoxia (1% oxygen) for up to 5 days, and assessed with qRT-PCR, cell morphology, and colony morphology. Protein expression in human breast cancers was assessed with immunohistochemistry. ZEB1-MYB promoter binding and repression were determined with Chromatin Immunoprecipitation Assay and a luciferase reporter assay, respectively. Student paired t tests, Mann-Whitney, and repeated measures two-way ANOVA tests determined statistical significance (P < 0.05).

RESULTS

Parental PMC42-ET cells displayed higher expression of ZEB1 and lower expression of MYB than did the PMC42-LA epithelial variant. Knockdown of ZEB1 in PMC42-ET and MDA-MB-231 cells caused increased expression of MYB and a transition to a more epithelial phenotype, which in PMC42-ET cells was coupled with increased proliferation. Indeed, we observed an inverse relation between MYB and ZEB1 expression in two in vitro EMT cell models, in matched human breast tumors and lymph node metastases, and in human breast cancer cell lines. Knockdown of MYB in PMC42-LA cells (MYBsh-LA) led to morphologic changes and protein expression consistent with an EMT. ZEB1 expression was raised in MYBsh-LA cells and significantly repressed in MYB-overexpressing MDA-MB-231 cells, which also showed reduced random migration and a shift from mesenchymal to epithelial colony morphology in two dimensional monolayer cultures. Finally, we detected binding of ZEB1 to MYB promoter in PMC42-ET cells, and ZEB1 overexpression repressed MYB promoter activity.

CONCLUSIONS

This work identifies ZEB1 as a transcriptional repressor of MYB and suggests a reciprocal MYB-ZEB1 repressive relation, providing a mechanism through which proliferation and the epithelial phenotype may be coordinately modulated in breast cancer cells.

A p21-ZEB1 complex inhibits epithelial-mesenchymal transition through the microRNA 183-96-182 cluster

The tumor suppressor p21 acts as a cell cycle inhibitor and has also been shown to regulate gene expression by functioning as a transcription corepressor. Here, we identified p21-regulated microRNAs (miRNAs) by sequencing small RNAs from isogenic p21(+/+) and p21(-/-) cells. Three abundant miRNA clusters, miR-200b-200a-429, miR-200c-141, and miR-183-96-182, were downregulated in p21-deficient cells. Consistent with the known function of the miR-200 family and p21 in inhibition of the epithelial-mesenchymal transition (EMT), we observed EMT upon loss of p21 in multiple model systems. To explore a role of the miR-183-96-182 cluster in EMT, we identified its genome-wide targets and found that miR-183 and miR-96 repressed common targets, including SLUG, ZEB1, ITGB1, and KLF4. Reintroduction of miR-200, miR-183, or miR-96 in p21(-/-) cells inhibited EMT, cell migration, and invasion. Conversely, antagonizing miR-200 and miR-183-96-182 cluster miRNAs in p21(+/+) cells increased invasion and elevated the levels of VIM, ZEB1, and SLUG mRNAs. Furthermore, we found that p21 forms a complex with ZEB1 at the miR-183-96-182 cluster promoter to inhibit transcriptional repression of this cluster by ZEB1, suggesting a reciprocal feedback loop.

MiR-200, a new star miRNA in human cancer

MicroRNAs (miRNAs) are a set of non-coding small RNA molecules in control of gene expression at posttranscriptional/translational level. They not only play crucial roles in normal developmental progress, but also are commonly dysregulated in human diseases, including cancer. MiR-200 is a family of tumor suppressor miRNAs consisting of five members, which are significantly involved in inhibition of epithelial-to-mesenchymal transition (EMT), repression of cancer stem cells (CSCs) self-renewal and differentiation, modulation of cell division and apoptosis, and reversal of chemoresistance. In this article, we summarize the latest findings with regard to the tumor suppressor signatures of miR-200 and the regulatory mechanisms of miR-200 expression. The collected evidence supports that miR-200 is becoming a new star miRNA in study of human cancer.

Treatment of cancer micrometastasis using a multicomponent chain-like nanoparticle

While potent cytotoxic agents are available to oncologists, the clinical utility of these agents is limited due to their non-specific distribution in the body and toxicity to normal tissues leading to use of suboptimal doses for eradication of metastatic disease. Furthermore, treatment of micrometastases is impeded by several biobarriers, including their small size and high dispersion to organs, making them nearly inaccessible to drugs. To circumvent these limitations in treating metastatic disease, we developed a multicomponent, flexible chain-like nanoparticle (termed nanochain) that possesses a unique ability to gain access to and be deposited at micrometastatic sites. Moreover, coupling nanochain particles to radiofrequency (RF)-triggered cargo delivery facilitated widespread delivery of drug into hard-to-reach cancer cells. Collectively, these features synergistically facilitate effective treatment and ultimately eradication of micrometastatic disease using a low dose of a cytotoxic drug.

Direct targeting of SUZ12/ROCK2 by miR-200b/c inhibits cholangiocarcinoma tumourigenesis and metastasis

Background:

The multidrug resistance and distant metastasis of cholangiocarcinoma result in high postoperative recurrence and low long-term survival rates. It has been demonstrated that the ectopic expression of miR-200 suppresses the multidrug resistance and metastasis of cancer. However, the expression and function of miR-200 in cholangiocarcinoma has not yet been described.

Methods:

In this study, we identified dysregulated microRNAs (miRNAs, miR) in cholangiocarcinoma tissue by microarray analysis, and subsequent real-time PCR and northern blot analyses validated the expression of candidate miR. We performed functional analyses and investigated the relationship between miR-200b/c expression and the properties of cholangiocarcinoma cells. A dual luciferase assay was applied to examine the effect of miRNAs on the 3′-UTR of target genes, and we demonstrated the function of the target gene by siRNA transfection identifying the downstream pathway via western blotting.

Results:

We found significantly downregulated expression of four miR-200 family members (miR-200a/b/c/429) and then confirmed that ectopic miR-200b/200c inhibits the migration and invasion of cholangiocarcinoma cells both in vitro and in vivo. We found that miR-200b/c influenced the tumourigenesis of cholangiocarcinoma cells including their tumour-initiating capacity, sphere formation, and drug resistance. We further found that miR-200b/c regulated migration and invasion capacities by directly targeting rho-kinase 2 and regulated tumorigenic properties by directly targeting SUZ12 (a subunit of a polycomb repressor complex).

Conclusion:

Our study shows that miR-200b/c has a critical role in the regulation of the tumorigenic and metastatic capacity of cholangiocarcinoma and reveals the probable underlying mechanisms.

The roles of HLH transcription factors in epithelial mesenchymal transition and multiple molecular mechanisms

Epithelial-to-mesenchymal transition (EMT) is presently recognized as an important event and the initiating stage for tumor invasion and metastasis. Several EMT inducers have been identified, among which the big family of helix-loop-helix (HLH) transcription factors are rising as a novel and promising family of proteins in EMT mediation, such as Twist1, Twist2, E47, and HIFs, etc. Due to the variety and complexities of HLH members, the pathways and mechanisms they employ to promote EMT are also complex and characteristic. In this review, we will discuss the roles of various HLH proteins in the regulation and sustenance of the EMT and multiple cellular mechanisms, attempting to provide a novel and broadened view towards the link between HLH proteins and EMT.

Microenvironmental regulation of cancer metastasis by miRNAs

miRNAs are a class of small, non-coding RNAs that regulate cancer progression, especially the processes of invasion and metastasis. Although earlier studies in metastasis primarily focused on the impact that miRNAs have on the intrinsic properties of cancer cells, recent reports reveal that miRNAs also shape interactions between cancer cells and their associated stroma. In this review, we discuss current known mechanisms by which miRNAs execute their microenvironmental regulation of cancer metastasis, including regulating expression of cell membrane-bound and secreted proteins or directly transmitting mature miRNAs between different cell types. The significance of miRNA-mediated tumor-stroma interactions in regulating metastasis suggests that miRNAs may be a potential therapeutic target.

NF-κB-mediated inflammation leading to EMT via miR-200c is involved in cell transformation induced by cigarette smoke extract

Cigarette smoking constitutes a major human health hazard because it is the most important risk factor for lung cancer. Although evidence for smoking-induced lung cancer in humans is strong, the molecular mechanisms by which smoking causes cancer remain to be established. In this investigation, we evaluated the roles of inflammation and the epithelial-mesenchymal transition (EMT) in cigarette smoke extract (CSE)-induced transformation of human bronchial epithelial (HBE) cells. The results showed that chronic exposure to CSE induced EMT and transformation of these cells. Activation of nuclear factor-κB (NF-κB) by CSE increased levels of the proinflammatory interleukin-6 (IL-6), and acute and chronic exposures to CSE caused decreases in miR-200c levels. By blocking NF-κB with Bay11-7082 and IL-6 with anti-IL-6 antibody and enhancement of IL-6 with human recombinant IL-6, we found that the NF-κB signal pathway was involved in CSE-induced increases of IL-6, which suppressed miR-200c expression and promoted EMT. Moreover, IL-6 was necessary for maintenance of CSE-induced transformation and for malignant progression of HBE cells. Finally, blocking of NF-κB with Bay11-7082 prevented CSE-induced EMT and malignant transformation due to decreases of E-cadherin and miR-200c and elevations of IL-6, N-cadherin, and vimentin. Thus, we have defined a link between inflammation and EMT, processes involved in the malignant transformation of cells caused by CSE. This link, mediated through miRNAs, establishes a mechanism for CSE-induced lung carcinogenesis.

Dynamics and regulation of epithelial adherens junctions: recent discoveries and controversies

Adherens junctions (AJs) are evolutionarily conserved plasma-membrane structures that mediate cell-cell adhesions in multicellular organisms. They are organized by several types of adhesive integral membrane proteins, most notably cadherins and nectins that are clustered and stabilized by a number of cytoplasmic scaffolds. AJs are key regulators of tissue architecture and dynamics via control of cell proliferation, polarity, shape, motility, and survival. They are absolutely critical for normal tissue morphogenesis and their disruption results in pathological abnormalities in different tissues. Although the field of adherens-junction research dramatically progressed in recent years, a number of important questions remain controversial and poorly understood. This review outlines basic principles that regulate organization of AJs in mammalian epithelia and discusses recent advances and standing controversies in the field. A special attention is paid to the regulation of AJs by vesicle trafficking and the intracellular cytoskeleton as well as roles and mechanisms of adherens-junction disruption during tumor progression and tissue inflammation.

Ensemble classifier based on context specific miRNA regulation modules: a new method for cancer outcome prediction

Background

Many calssifiers which are constructed with chosen gene markers have been proposed to forecast the prognosis of patients who suffer from breast cancer. However, few of them has been applied in clinical practice because of the bad generalization, which results from the situation that markers selected by one method are very different from those obtained by anohter mothod, and thus such markers always lack discriminative capability in the other data sets.

Methods

In this work, a new ensemble classifier, on the basis of context specific miRNA regulation modules, has been proposed to forecast the metastasis risk of cancer sufferers. First, we defined all of the miRNAs which regulate the same context as a module that contains miRNAs and their regulating context, and applied the CoMi (Context-specific miRNA activity) score in order to illustrate a miRNA's effect which happened in a particular background; then the miRNA regulation modules with distinguising abilities were detected and each of them was responsible for building a weak classifier separately; at last, by using majority voting strategy, we integrated all weak classifiers to establish an ensembled one that was applied to forecast the prognosis of patients who suffer from cancer.

Results

After comparing, the results on the cohorts containing over 1,000 samples showed that the proposed ensemble classifier is superior to other three classifiers based on miRNA expression profiles, mRNA expression profiles and CoMi activity patterns respectively. Significantly, our method outperforms the representative works. Moreover, the detected modules from different data sets show great stability (with p-value of 6.40e-08). For investigating the biological significance of those selected modules, case studies have been done by us and the results suggested that our method do help to reveal latent mechanism in metastasis of breast cancer.

Conclusions

One context specific miRNA regulation module can uncover one critical biological process and its involved miRNAs that are related to the cancer outcome, and several modules together can help to study the biological mechanism in cancer metastasis, thus the classifer based on ensembling multiple classifers which were built with different context specific miRNA regulation modules has showed promising performances in terms with both prediction accuracy and generalization.

MiR-200 can repress breast cancer metastasis through ZEB1-independent but moesin-dependent pathways

The microRNA-200 (miR-200) family has a critical role in regulating epithelial-mesenchymal transition and cancer cell invasion through inhibition of the E-cadherin transcriptional repressors ZEB1 and ZEB2. Recent studies have indicated that the miR-200 family may exert their effects at distinct stages in the metastatic process, with an overall effect of enhancing metastasis in a syngeneic mouse breast cancer model. We find in a xenograft orthotopic model of breast cancer metastasis that ectopic expression of members of the miR-200b/200c/429, but not the miR-141/200a, functional groups limits tumour cell invasion and metastasis. Despite modulation of the ZEB1-E-cadherin axis, restoration of ZEB1 in miR-200b-expressing cells was not able to alter metastatic potential suggesting that other targets contribute to this process. Instead, we found that miR-200b repressed several actin-associated genes, with the knockdown of the ezrin-radixin-moesin family member moesin alone phenocopying the repression of cell invasion by miR-200b. Moesin was verified to be directly targeted by miR-200b, and restoration of moesin in miR-200b-expressing cells was sufficient to alleviate metastatic repression. In breast cancer cell lines and patient samples, the expression of moesin significantly inversely correlated with miR-200 expression, and high levels of moesin were associated with poor relapse-free survival. These findings highlight the context-dependent effects of miR-200 in breast cancer metastasis and demonstrate the existence of a moesin-dependent pathway, distinct from the ZEB1-E-cadherin axis, through which miR-200 can regulate tumour cell plasticity and metastasis.

Downregulation of miR-145 contributes to lung adenocarcinoma cell growth to form brain metastases

The development of metastases involves the dissociation of cells from the primary tumor, penetrating the basement membrane, invasion and exiting from the vasculature to seed, and finally colonizing in distant tissues. The formation of brain metastasis (BM) in lung adenocarcinoma remains poorly understood. We examined the differential microRNA (miRNA) expression profiles of 5 primary and 3 brain metastatic lung adenocarcinoma samples by Agilent miRNA Microarrays. Five upregulated miRNAs (miRs-9*, -1471, 718, 3656, 720) and 3 downregulated miRNAs (miRs-214, -145 and -23a) were detected. The 4 most significantly deregulated miRNAs (miR-145, miR-214, miR-9* and miR-1471) were validated in the additional 43 samples (35 primary and 8 brain metastatic lung adenocarcinoma samples) using TaqMan quantitative PCR. By functional assay, we found that the expression of miR-145 can regulate the ability of proliferation of A549 and SPC-A1 cells in vitro, but is not related to lymph node metastasis, migration and invasion. These results suggest that miR-145 may have a cell type-specific function and play important roles in the process of BM from lung adenocarcinoma.

MicroRNAs and liver cancer associated with iron overload: Therapeutic targets unravelled

Primary liver cancer is a global disease that is on the increase. Hepatocellular carcinoma (HCC) accounts for most primary liver cancers and has a notably low survival rate, largely attributable to late diagnosis, resistance to treatment, tumour recurrence and metastasis. MicroRNAs (miRNAs/miRs) are regulatory RNAs that modulate protein synthesis. miRNAs are involved in several biological and pathological processes including the development and progression of HCC. Given the poor outcomes with current HCC treatments, miRNAs represent an important new target for therapeutic intervention. Several studies have demonstrated their role in HCC development and progression. While many risk factors underlie the development of HCC, one process commonly altered is iron homeostasis. Iron overload occurs in several liver diseases associated with the development of HCC including Hepatitis C infection and the importance of miRNAs in iron homeostasis and hepatic iron overload is well characterised. Aberrant miRNA expression in hepatic fibrosis and injury response have been reported, as have dysregulated miRNA expression patterns affecting cell cycle progression, evasion of apoptosis, invasion and metastasis. In 2009, miR-26a delivery was shown to prevent HCC progression, highlighting its therapeutic potential. Several studies have since investigated the clinical potential of other miRNAs with one drug, Miravirsen, currently in phase II clinical trials. miRNAs also have potential as biomarkers for the diagnosis of HCC and to evaluate treatment efficacy. Ongoing studies and clinical trials suggest miRNA-based treatments and diagnostic methods will have novel clinical applications for HCC in the coming years, yielding improved HCC survival rates and patient outcomes.

On-command drug release from nanochains inhibits growth of breast tumors

PURPOSE

To evaluate the ability of radiofrequency (RF)-triggered drug release from a multicomponent chain-shaped nanoparticle to inhibit the growth of an aggressive breast tumor.

METHODS

A two-step solid phase chemistry was employed to synthesize doxorubicin-loaded nanochains, which were composed of three iron oxide nanospheres and one doxorubicin-loaded liposome assembled in a 100-nm-long linear nanochain. The nanochains were tested in the 4T1-LUC-GFP orthotopic mouse model, which is a highly aggressive breast cancer model. The 4T1-LUC-GFP cell line stably expresses firefly luciferase, which allowed the non-invasive in vivo imaging of tumor response to the treatment using bioluminescence imaging (BLI).

RESULTS

Longitudinal BLI imaging showed that a single nanochain treatment followed by application of RF resulted in an at least 100-fold lower BLI signal compared to the groups treated with nanochains (without RF) or free doxorubicin followed by RF. A statistically significant increase in survival time of the nanochain-treated animals followed by RF (64.3 days) was observed when compared to the nanochain-treated group without RF (35.7 days), free doxorubicin-treated group followed by RF (38.5 days), and the untreated group (30.5 days; n=5 animals per group).

CONCLUSIONS

These studies showed that the combination of RF and nanochains has the potential to effectively treat highly aggressive cancers and prolong survival.

Identification of p130Cas/ErbB2-dependent invasive signatures in transformed mammary epithelial cells

Understanding transcriptional changes during cancer progression is of crucial importance to develop new and more efficacious diagnostic and therapeutic approaches. It is well known that ErbB2 is overexpressed in about 25% of human invasive breast cancers. We have previously demonstrated that p130Cas overexpression synergizes with ErbB2 in mammary cell transformation and promotes ErbB2-dependent invasion in three-dimensional (3D) cultures of human mammary epithelial cells. Here, by comparing coding and non-coding gene expression profiles, we define the invasive signatures associated with concomitant p130Cas overexpression and ErbB2 activation in 3D cultures of mammary epithelial cells. Specifically, we have found that genes involved in amino acids synthesis (CBS, PHGDH), cell motility, migration (ITPKA, PRDM1), and angiogenesis (HEY1) are upregulated, while genes involved in inflammatory response (SAA1, S100A7) are downregulated. In parallel, we have shown that the expression of specific miRNAs is altered. Among these, miR-200b, miR-222, miR-221, miR-R210, and miR-424 are upregulated, while miR-27a, miR-27b, and miR-23b are downregulated. Overall, this study presents, for the first time, the gene expression changes underlying the invasive behavior following p130Cas overexpression in an ErbB2 transformed mammary cell model.

MicroRNA control of epithelial-mesenchymal transition and metastasis

The great majority of cancer deaths are due to metastasis, which remains a poorly understood pathological process. The formation of a metastasis reflects a succession of complex steps leading to the macroscopic outgrowth of disseminated tumor cells at the secondary site. In the past 5 years, certain microRNAs (miRNAs) have been shown to regulate either a single step or multiple steps of metastasis, doing so by downregulating the expression of their target genes. In this review, we discuss recent studies on the functions and molecular mechanisms of miRNAs in regulating epithelial-mesenchymal transition (EMT) and cancer metastasis.

HMGA2 is a driver of tumor metastasis

The non-histone chromatin-binding protein HMGA2 is expressed predominantly in the mesenchyme before its differentiation, but it is also expressed in tumors of epithelial origin. Ectopic expression of HMGA2 in epithelial cells induces epithelial-mesenchymal transition (EMT), which has been implicated in the acquisition of metastatic characters in tumor cells. However, little is known about in vivo modulation of HMGA2 and its effector functions in tumor metastasis. Here, we report that HMGA2 loss of function in a mouse model of cancer reduces tumor multiplicity. HMGA2-positive cells were identified at the invasive front of human and mouse tumors. In addition, in a mouse allograft model, HMGA2 overexpression converted nonmetastatic 4TO7 breast cancer cells to metastatic cells that homed specifically to liver. Interestingly, expression of HMGA2 enhanced TGFβ signaling by activating expression of the TGFβ type II receptor, which also localized to the invasive front of tumors. Together our results argued that HMGA2 plays a critical role in EMT by activating the TGFβ signaling pathway, thereby inducing invasion and metastasis of human epithelial cancers.

The microRNA-200 family targets multiple non-small cell lung cancer prognostic markers in H1299 cells and BEAS-2B cells

Lung cancer remains the leading cause of cancer-related mortality for both men and women. Tumor recurrence and metastasis is the major cause of lung cancer treatment failure and death. The microRNA‑200 (miR-200) family is a powerful regulator of the epithelial-mesenchymal transition (EMT) process, which is essential in tumor metastasis. Nevertheless, miR-200 family target genes that promote metastasis in non-small cell lung cancer (NSCLC) remain largely unknown. Here, we sought to investigate whether the microRNA-200 family regulates our previously identified NSCLC prognostic marker genes associated with metastasis, as potential molecular targets. Novel miRNA targets were predicted using bioinformatics tools based on correlation analyses of miRNA and mRNA expression in 57 squamous cell lung cancer tumor samples. The predicted target genes were validated with quantitative RT-PCR assays and western blot analysis following re-expression of miR-200a, -200b and -200c in the metastatic NSCLC H1299 cell line. The results show that restoring miR-200a or miR-200c in H1299 cells induces downregulation of DLC1, ATRX and HFE. Reinforced miR-200b expression results in downregulation of DLC1, HNRNPA3 and HFE. Additionally, miR-200 family downregulates HNRNPR3, HFE and ATRX in BEAS-2B immortalized lung epithelial cells in quantitative RT-PCR and western blot assays. The miR-200 family and these potential targets are functionally involved in canonical pathways of immune response, molecular mechanisms of cancer, metastasis signaling, cell-cell communication, proliferation and DNA repair in Ingenuity pathway analysis (IPA). These results indicate that re-expression of miR-200 downregulates our previously identified NSCLC prognostic biomarkers in metastatic NSCLC cells. These results provide new insights into miR-200 regulation in lung cancer metastasis and consequent clinical outcome, and may provide a potential basis for innovative therapeutic approaches for the treatment of this deadly disease.

Mmu-microRNA-200a overexpression leads to implantation defect by targeting phosphatase and tensin homolog in mouse uterus

Successful mouse embryo implantation requires a receptive uterus and an activated blastocyst. A large number of genes, cytokines, and other factors are involved in the process. MicroRNAs (miRNAs) regulate the expression of many genes, and previous studies have investigated the relationship between miRNA expression and embryo implantation. In this study, we show that mmu-microRNA-200a (mmu-miR-200a) is expressed in a spatiatemporal manner during implantation in mouse uterus and found that phosphatase and tensin homolog (PTEN), SON, and programmed cell death 4 (Pdcd4) are the target genes of mmu-miR-200a by bioinformatics analysis. In vitro gain and loss of function experiments confirm that PTEN, a critical gene for cell proliferation and apoptosis, is the target gene of mmu-miR-200a. Our experiments also show that injection of the uterine horn with mmu-miR-200a lentivirus leads to a decreased implantation rate. Collectively, our results suggest that mmu-miR-200a affects embryo implantation by regulating PTEN protein expression. Thus, clarifying the physiological functions of uterine miRNAs will help to elucidate the embryo implantation process and may even contribute to curing infertility and inventing new contraceptives.

Overexpressions of microRNA-9 and microRNA-200c in human breast cancers are associated with lymph node metastasis

PURPOSE

The aim of this study was to investigate the relationship between the expressions of microRNA-9 (miR-9) and microRNA-200c (miR-200c) in human breast cancers and clinicopathological features.

METHODS

We investigated the expressions of miR-9 and miR-200c in 68 patients with breast cancers using the quantitative reverse transcription-polymerase chain reaction method, and assessed the E-cadherin status using the immunohistochemistry method.

RESULTS

The relative expression levels of miR-9 and miR-200c in breast cancer patients with lymph node metastasis were higher than that of patients without lymph node metastasis. The expression of miR-9 correlated inversely with E-cadherin expression.

CONCLUSIONS

The results showed that higher expressions of miR-9 and miR-200c in human breast cancers were associated with lymph node metastasis. This study indicated that the elevation of miR-9 and miR-200c in human breast cancers can induce an invasive phenotype and may serve as a molecular diagnostic marker for patients with breast cancer.

Reduced expression of miR-200 family members contributes to antiestrogen resistance in LY2 human breast cancer cells

INTRODUCTION

The role of miRNAs in acquired endocrine-resistant breast cancer is not fully understood. One hallmark of tumor progression is epithelial-to-mesenchymal transition (EMT), characterized by a loss of cell adhesion resulting from reduced E-cadherin and increased cell mobility. miR-200 family members regulate EMT by suppressing expression of transcriptional repressors ZEB1/2. Previously we reported that the expression of miR-200a, miR-200b, and miR-200c was lower in LY2 endocrine-resistant, mesenchymal breast cancer cells compared to parental, endocrine sensitive, epithelial MCF-7 breast cancer cells. Here we investigated the regulation of miR-200 family members and their role in endocrine-sensitivity in breast cancer cells.

RESULTS

miR-200 family expression was progressively reduced in a breast cancer cell line model of advancing endocrine/tamoxifen (TAM) resistance. Concomitant with miR-200 decrease, there was an increase in ZEB1 mRNA expression. Overexpression of miR-200b or miR-200c in LY2 cells altered cell morphology to a more epithelial appearance and inhibited cell migration. Further, miR-200b and miR-200c overexpression sensitized LY2 cells to growth inhibition by estrogen receptor (ER) antagonists TAM and fulvestrant. Knockdown of ZEB1 in LY2 cells recapitulated the effect of miR-200b and miR-200c overexpression resulting in inhibition of LY2 cell proliferation by TAM and fulvestrant, but not the aromatase inhibitor exemestane. Demethylating agent 5-aza-2'-deoxycytidine (5-aza-dC) in combination with histone deacetylase inhibitor trichostatin A (TSA) increased miR-200b and miR-200c in LY2 cells. Concomitant with the increase in miR-200b and miR-200c, ZEB1 expression was decreased and cells appeared more epithelial in morphology and were sensitized to TAM and fulvestrant inhibition. Likewise, knockdown of ZEB1 increased antiestrogen sensitivity of LY2 cells resulting in inhibition of cell proliferation.

CONCLUSIONS

Our data indicate that reduced miRNA-200b and miR-200c expression contributes to endocrine resistance in breast cancer cells and that the reduced expression of these miR-200 family members in endocrine-resistant cells can be reversed by 5-aza-dC+TSA.

Identification of miR-221 and -222 as important regulators in genotype IV swine hepatitis E virus ORF3-expressing HEK 293 cells

Hepatitis E virus (HEV) has emerged as an important cause of epidemic and sporadic acute viral hepatitis worldwide, which is a major public health challenge. A better understanding of the interaction between the virus and the host cell would be very helpful for its therapy. Swine HEV (SHEV) open reading frame 3 (ORF3) is a regulatory protein that alters the activity of selected transcription factors and cytoplasmic signaling pathways. MicroRNAs (miRNAs) are potent post-transcriptional regulators of protein-coding genes and represent an interesting lead to study SHEV infection and to identify new therapeutic targets. To explore how SHEV ORF3 affects miRNAs in host cells, we used miRNA array analysis to compare the expression patterns of miRNAs in stable cell lines that expressed or did not express SHEV ORF3. We found a significant down-regulation of miR-221 and -222 in ORF3 expressing human embryonic kidney 293 cell line. Among the 116 candidate targets genes of miR-221 and -222 that we detected in silico, we demonstrated that the expression of the cyclin-dependent kinase inhibitor 1B, also named p27(kip1), was directly regulated by these miRNAs. We hypothesize that SHEV ORF3-induced miR-221/222 downregulation enhances p27(kip1) expression in HEK293 cells. This provides new avenues for future exploration of the precise roles of miRNAs in SHEV infection.

MicroRNAs regulate both epithelial-to-mesenchymal transition and cancer stem cells

Concepts and experimental models derived from basic research have been successfully applied to the field of molecular oncology, tremendously increasing our knowledge of the nature and the progression of tumors. The process of epithelial-to-mesenchymal transition, the cancer stem cell hypothesis, and their functional association and interdependence represent some of the most significant examples. The molecular determinants underlying the plasticity of cancers are currently the object of extensive research efforts, and a substantial body of evidence suggests that these models can be connected by the regulatory role of microRNAs, small noncoding RNA molecules with a fundamental role in many cellular functions. This review will highlight and discuss this link and its possible implications for the fight against cancer.

Sequential inductions of the ZEB1 transcription factor caused by mutation of Rb and then Ras proteins are required for tumor initiation and progression

Rb1 restricts cell cycle progression, and it imposes cell contact inhibition to suppress tumor outgrowth. It also triggers oncogene-induced senescence to block Ras mutation. Loss of the Rb1 pathway, which is a hallmark of cancer cells, then provides a permissive environment for Ras mutation, and Ras is sufficient for invasive tumor formation in Rb1 family mutant mouse embryo fibroblasts (MEFs). These results demonstrate that sequential mutation of the Rb1 and Ras pathways comprises a tumor initiation axis. Both Rb1 and Ras regulate expression of the transcription factor ZEB1, thereby linking tumor initiation to the subsequent invasion and metastasis, which is induced by ZEB1. ZEB1 acts in a negative feedback loop to block expression of miR-200, which is thought to facilitate tumor invasion and metastasis. However, ZEB1 also represses cyclin-dependent kinase (cdk) inhibitors to control the cell cycle; its mutation in MEFs leads to induction of these inhibitors and premature senescence. Here, we provide evidence for two sequential inductions of ZEB1 during Ras transformation of MEFs. Rb1 constitutively represses cdk inhibitors, and induction of ZEB1 when the Rb1 pathway is lost is required to maintain this repression, allowing for the classic immortalization and loss of cell contact inhibition seen when the Rb1 pathway is lost. In vivo, we show that this induction of ZEB1 is required for Ras-initiated tumor formation. ZEB1 is then further induced by Ras, beyond the level seen with Rb1 mutation, and this Ras superinduction is required to reach a threshold of ZEB1 sufficient for repression of miR-200 and tumor invasion.

Down-regulation of the miRNA-200 family at the invasive front of colorectal cancers with degraded basement membrane indicates EMT is involved in cancer progression

Cancer progression is a complex series of events thought to incorporate the reversible developmental process of epithelial-to-mesenchymal transition (EMT). In vitro, the microRNA-200 family maintains the epithelial phenotype by posttranscriptionally inhibiting the E-cadherin repressors, ZEB1 and ZEB2. Here, we used in situ hybridization and immunohistochemistry to assess expression of miR-200 and EMT biomarkers in formalin-fixed paraffin-embedded human colorectal adenocarcinomas. In addition, laser capture microdissection and quantitative real-time polymerase chain reaction were employed to quantify levels of miR-200 in the normal epithelium, tumor core, invasive front, and stroma. We find that miR-200 is downregulated at the invasive front of colorectal adenocarcinomas that have destroyed and invaded beyond the basement membrane. However, regional lymph node metastases and vascular carcinoma deposits show strong expression of miR-200, suggesting this family of miRNAs is involved in the recapitulation of the primary tumor phenotype at metastatic sites. In contrast, adenomas and adenocarcinomas with intact basement membranes showed uniform miR-200 expression from the tumor core to the tumor-host interface. Taken together, these data support the involvement of EMT and mesenchymal-to-epithelial transition (MET) in the metastasis cascade and show that miR-200 is downregulated in the initial stages of stromal invasion but is restored at metastatic sites.

GATA3 suppresses metastasis and modulates the tumour microenvironment by regulating microRNA-29b expression

Despite advances in our understanding of breast cancer, patients with metastatic disease have poor prognoses. GATA3 is a transcription factor that specifies and maintains mammary luminal epithelial cell fate, and its expression is lost in breast cancer, correlating with a worse prognosis in human patients. Here, we show that GATA3 promotes differentiation, suppresses metastasis and alters the tumour microenvironment in breast cancer by inducing microRNA-29b (miR-29b) expression. Accordingly, miR-29b is enriched in luminal breast cancers and loss of miR-29b, even in GATA3-expressing cells, increases metastasis and promotes a mesenchymal phenotype. Mechanistically, miR-29b inhibits metastasis by targeting a network of pro-metastatic regulators involved in angiogenesis, collagen remodelling and proteolysis, including VEGFA, ANGPTL4, PDGF, LOX and MMP9, and targeting ITGA6, ITGB1 and TGFB, thereby indirectly affecting differentiation and epithelial plasticity. The discovery that a GATA3-miR-29b axis regulates the tumour microenvironment and inhibits metastasis opens up possibilities for therapeutic intervention in breast cancer.

P-cadherin functional role is dependent on E-cadherin cellular context: a proof of concept using the breast cancer model

P-cadherin overexpression is associated with worse breast cancer survival, being a poor prognostic marker as well as a putative therapeutic target for the aggressive triple-negative and basal-like carcinomas (TNBCs). Previously, we have shown that P-cadherin promotes breast cancer invasion of cells where membrane E-cadherin was maintained; however, it suppresses invasion in models without endogenous cadherins, like melanomas. Here, we investigated if P-cadherin expression would interfere with the normal adhesion complex and which were the cellular/molecular consequences, constituting, in this way, a new mechanism by which E-cadherin invasive-suppressor function was disrupted. Using breast TNBC models, we demonstrated, for the first time, that P-cadherin co-localizes with E-cadherin, promoting cell invasion due to the disruption caused in the interaction between E-cadherin and cytoplasmic catenins. P-cadherin also induces cell migration and survival, modifying the expression profile of cells expressing wild-type E-cadherin and contributing to alter their cellular behaviour. Additionally, E- and P-cadherin co-expressing cells significantly enhanced in vivo tumour growth, compared with cells expressing only E- or only P-cadherin. Finally, we still found that co-expression of both molecules was significantly correlated with high-grade breast carcinomas, biologically aggressive, and with poor patient survival, being a strong prognostic factor in this disease. Our results show a role for E- and P-cadherin co-expression in breast cancer progression and highlight the potential benefit of targeting P-cadherin in the aggressive tumours expressing high levels of this protein.

Role of deregulated microRNAs in breast cancer progression using FFPE tissue

MicroRNAs (miRNAs) contribute to cancer initiation and progression by silencing the expression of their target genes, causing either mRNA molecule degradation or translational inhibition. Intraductal epithelial proliferations of the breast are histologically and clinically classified into normal, atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC). To better understand the progression of ductal breast cancer development, we attempt to identify deregulated miRNAs in this process using Formalin-Fixed, Paraffin-Embedded (FFPE) tissues from breast cancer patients. Following tissue microdissection, we obtained 8 normal, 4 ADH, 6 DCIS and 7 IDC samples, which were subject to RNA isolation and miRNA expression profiling analysis. We found that miR-21, miR-200b/c, miR-141, and miR-183 were consistently up-regulated in ADH, DCIS and IDC compared to normal, while miR-557 was uniquely down-regulated in DCIS. Interestingly, the most significant miRNA deregulations occurred during the transition from normal to ADH. However, the data did not reveal a step-wise miRNA alteration among discrete steps along tumor progression, which is in accordance with previous reports of mRNA profiling of different stages of breast cancer. Furthermore, the expression of MSH2 and SMAD7, two important molecules involving TGF-β pathway, was restored following miR-21 knockdown in both MCF-7 and Hs578T breast cancer cells. In this study, we have not only identified a number of potential candidate miRNAs for breast cancer, but also found that deregulation of miRNA expression during breast tumorigenesis might be an early event since it occurred significantly during normal to ADH transition. Consequently, we have demonstrated the feasibility of miRNA expression profiling analysis using archived FFPE tissues, typically with rich clinical information, as a means of miRNA biomarker discovery.

MicroRNA-200a promotes anoikis resistance and metastasis by targeting YAP1 in human breast cancer

PURPOSE

The process of metastases involves the dissociation of cells from the primary tumor, penetration into the basement membrane, invasion, and exiting from the vasculature to seed and colonize distant tissues. miR-200a is involved in this multistep metastatic cascade. This study aimed to test the hypothesis that miR-200a promotes metastasis through increased anoikis resistance in breast cancer.

EXPERIMENTAL DESIGN

Breast cancer cells transfected with mimic or inhibitor for miR-200a were assayed for anoikis in vitro. miR-200a expression was assessed by quantitative real-time PCR (qRT-PCR). Luciferase assays, colony formation assays, and animal studies were conducted to identify the targets of miR-200a and the mechanism by which it promotes anoikis resistance.

RESULTS

We found that overexpression of miR-200a promotes whereas inhibition of miR-200a suppresses anoikis resistance in breast cancer cells. We identified Yes-associated protein 1 (YAP1) as a novel target of miR-200a. Our data showed that targeting of YAP1 by miR-200a resulted in decreased expression of proapoptotic proteins, which leads to anoikis resistance. Overexpression of miR-200a protected tumor cells from anoikis and promoted metastases in vivo. Furthermore, knockdown of YAP1 phenocopied the effects of miR-200a overexpression, whereas restoration of YAP1 in miR-200a overexpressed breast cancer cells reversed the effects of miR-200a on anoikis and metastasis. Remarkably, we found that YAP1 expression was inversely correlated with miR-200a expression in breast cancer clinical specimens, and miR-200a expression was associated with distant metastasis in patients with breast cancer.

CONCLUSIONS

Our data suggest that miR-200a functions as anoikis suppressor and contributes to metastasis in breast cancer.

Role of microRNAs in breast cancer

MicroRNAs (miRNAs) are a class of post-transcriptional gene regulators with critical functions in normal cellular processes as well as disease processes. They are small molecules with 18~23 nucleotides in length. Since their early discovery in 1993, a large number of miRNAs have been characterized and analyzed to understand their pivotal role and their impact in a myriad of biological processes. Substantial research on miRNA highlights the involvement of these tiny RNAs in the etiopathogenesis of a variety of human diseases such as cancer, neuro-degenerative disorders, diabetes, cardiac hypertrophy and respiratory diseases. In this review, we update on recent advances of the emerging role of miRNAs in breast cancer and their clinical implications.

Grhl2 determines the epithelial phenotype of breast cancers and promotes tumor progression

Until now the essential transcription factor that determines the epithelial phenotype of breast cancer has not been identified and its role in epithelial-to-mesenchymal transition (EMT) and tumor progression remain unclear. Here, by analyzing large expression profiles of human breast cancer cells, we found an extraordinary correlation between the expression of Grainyhead transcription factor Grhl2 and epithelial marker E-cadherin. Knockdown of Grhl2 expression by shRNA in human mammary epithelial cell MCF10A leads to down-regulation of E-cadherin and EMT. Grhl2 is down-regulated in disseminated cancer cells that have undergone EMT, and over-expression of Grhl2 is sufficient to induce epithelial gene expression. Large clinical datasets reveal that expression of Grhl2 is significantly associated with poor relapse free survival and increased risk of metastasis in breast cancer patients. In mouse models, over-expression of Grhl2 significantly promotes tumor growth and metastasis. Further testing of several Grhl2 regulated genes leads to the same conclusions that the tumorigenic and metastatic potentials of tumor cells are linked to epithelial phenotype but not mesenchymal phenotype. In conclusion, our findings indicate that Grhl2 plays an essential role in the determination of epithelial phenotype of breast cancers, EMT and tumor progression.

Metastatic colonization requires the repression of the epithelial-mesenchymal transition inducer Prrx1

The epithelial-mesenchymal transition (EMT) is required in the embryo for the formation of tissues for which cells originate far from their final destination. Carcinoma cells hijack this program for tumor dissemination. The relevance of the EMT in cancer is still debated because it is unclear how these migratory cells colonize distant tissues to form macrometastases. We show that the homeobox factor Prrx1 is an EMT inducer conferring migratory and invasive properties. The loss of Prrx1 is required for cancer cells to metastasize in vivo, which revert to the epithelial phenotype concomitant with the acquisition of stem cell properties. Thus, unlike the classical EMT transcription factors, Prrx1 uncouples EMT and stemness, and is a biomarker associated with patient survival and lack of metastasis.

Regulation of iron homeostasis by microRNAs

Iron homeostasis is maintained at the cellular and systemic levels to assure adequate iron supply while preventing iron overload. The identification of genes mutated in patients with iron-related disorders or animal models with imbalances of iron homeostasis gave insight into the molecular mechanisms underlying processes critical for balancing iron levels, such as iron uptake, storage, export, and monitoring of available iron. MicroRNAs control genes involved in some of these processes adding an additional level of complexity to the regulation of iron metabolism. This review summarizes recent advances how miRNAs regulate iron homeostasis.

A systematic screen reveals MicroRNA clusters that significantly regulate four major signaling pathways

MicroRNAs (miRNAs) are encoded in the genome as individual miRNA genes or as gene clusters transcribed as polycistronic units. About 50% of all miRNAs are estimated to be co-expressed with neighboring miRNAs. Recent studies have begun to illuminate the importance of the clustering of miRNAs from an evolutionary, as well as a functional standpoint. Many miRNA clusters coordinately regulate multiple members of cellular signaling pathways or protein interaction networks. This cooperative method of targeting could produce effects on an overall process that are much more dramatic than the smaller effects often associated with regulation by an individual miRNA. In this study, we screened 366 human miRNA minigenes to determine their effects on the major signaling pathways culminating in AP-1, NF-κB, c-Myc, or p53 transcriptional activity. By stratifying these data into miRNA clusters, this systematic screen provides experimental evidence for the combined effects of clustered miRNAs on these signaling pathways. We also verify p53 as a direct target of miR-200a. This study is the first to provide a panoramic view of miRNA clusters' effects on cellular pathways.

Imaging metastasis using an integrin-targeting chain-shaped nanoparticle

While the enhanced permeability and retention effect may promote the preferential accumulation of nanoparticles into well-vascularized primary tumors, it is ineffective in the case of metastases hidden within a large population of normal cells. Due to their small size, high dispersion to organs, and low vascularization, metastatic tumors are less accessible to targeted nanoparticles. To tackle these challenges, we designed a nanoparticle for vascular targeting based on an α(v)β(3) integrin-targeted nanochain particle composed of four iron oxide nanospheres chemically linked in a linear assembly. The chain-shaped nanoparticles enabled enhanced "sensing" of the tumor-associated remodeling of the vascular bed, offering increased likelihood of specific recognition of metastatic tumors. Compared to spherical nanoparticles, the chain-shaped nanoparticles resulted in superior targeting of α(v)β(3) integrin due to geometrically enhanced multivalent docking. We performed multimodal in vivo imaging (fluorescence molecular tomography and magnetic resonance imaging) in a non-invasive and quantitative manner, which showed that the nanoparticles targeted metastases in the liver and lungs with high specificity in a highly aggressive breast tumor model in mice.

The role of microRNAs in breast cancer migration, invasion and metastasis

MicroRNAs (miRNAs) are a major class of small, noncoding RNA molecules that regulate gene expression by targeting mRNAs to trigger either translational repression or mRNA degradation. They have recently been more widely investigated due to their potential role as targets for cancer therapy. Many miRNAs have been implicated in several human cancers, including breast cancer. miRNAs are known to regulate cell cycle and development, and thus may serve as useful targets for exploration in anticancer therapeutics. The link between altered miRNA signatures and breast cancer development and metastasis can be observed either through the loss of tumor suppressor miRNAs, such as let-7s, miR-30a/31/34a/125s/200s/203/205/206/342 or the overexpression of oncogenic miRNAs, such as miR-10b/21/135a/155/221/222/224/373/520c in breast cancer cells. Some of these miRNAs have also been validated in tumor specimens of breast cancer patients, underscoring their potential roles in diagnostics, as well as targets for novel therapeutics for breast cancer. In this review article, we will provide an overview and update of our current understanding of the mode of action of several of these well characterized miRNAs in breast cancer models. Therefore, better understanding of the gene networks orchestrated by these miRNAs may help exploit the full potential of miRNAs in regards to cancer diagnosis, treatment, and therapeutics.

MiR-101 is involved in human breast carcinogenesis by targeting Stathmin1

Background

MicroRNA-101 (miR-101) expression is negatively associated with tumor growth and blood vessel formation in several solid epithelial cancers. However, the role of miR-101 in human breast cancer remains elusive.

Results

MiR-101 was significantly decreased in different subtypes of human breast cancer tissues compared with that in adjacent normal breast tissues (P<0.01). Up-regulation of miR-101 inhibited cell proliferation, migration and invasion, and promoted cell apoptosis in ER alpha-positive and ER alpha-negative breast cancer cells and normal breast cells. Down-regulation of miR-101 displayed opposite effects on cell growth and metastasis. Further investigation revealed a significant inverse correlation between the expression of miR-101 and Stathmin1 (Stmn1), and miR-101 could bind to the 3′-untranslated region (UTR) of Stmn1 to inhibit Stmn1 translation. The inhibition of cell growth and metastasis induced by up-regulation of miR-101 was partially restored by overexpresson of Stmn1. Knockdown of Stmn1 attenuates the down-regulation of miR-101-mediated enhancement of cell growth and metastasis. More importantly, in vivo analysis found that Stmn1 mRNA and protein level in different subtypes of human breast cancer tissues, contrary to the down-regulation of miR-101, were significantly elevated.

Conclusions

This study demonstrates that down-regulation of miR-101 in different subtypes of human breast cancer tissues is linked to the increase of cellular proliferation and invasiveness via targeting Stmn1, which highlights novel regulatory mechanism in breast cancer and may provide valuable clues for the future clinical diagnosis of breast cancer.

EMT-activating transcription factors in cancer: beyond EMT and tumor invasiveness

Cancer is a complex multistep process involving genetic and epigenetic changes that eventually result in the activation of oncogenic pathways and/or inactivation of tumor suppressor signals. During cancer progression, cancer cells acquire a number of hallmarks that promote tumor growth and invasion. A crucial mechanism by which carcinoma cells enhance their invasive capacity is the dissolution of intercellular adhesions and the acquisition of a more motile mesenchymal phenotype as part of an epithelial-to-mesenchymal transition (EMT). Although many transcription factors can trigger it, the full molecular reprogramming occurring during an EMT is mainly orchestrated by three major groups of transcription factors: the ZEB, Snail and Twist families. Upregulated expression of these EMT-activating transcription factors (EMT-ATFs) promotes tumor invasiveness in cell lines and xenograft mice models and has been associated with poor clinical prognosis in human cancers. Evidence accumulated in the last few years indicates that EMT-ATFs also regulate an expanding set of cancer cell capabilities beyond tumor invasion. Thus, EMT-ATFs have been shown to cooperate in oncogenic transformation, regulate cancer cell stemness, override safeguard programs against cancer like apoptosis and senescence, determine resistance to chemotherapy and promote tumor angiogenesis. This article reviews the expanding portfolio of functions played by EMT-ATFs in cancer progression.

Control by a hair's breadth: the role of microRNAs in the skin

MicroRNAs have continued to attract enormous interest in the scientific community ever since their discovery. Their allure stems from their unique role in posttranscriptional gene expression control as well as their potential application as therapeutic targets in various disease pathologies. While much is known concerning their general biological function, such as their interaction with RNA-induced silencing complexes, many important questions still remain unanswered, especially regarding their functions in the skin. In this review, we summarize our current knowledge of the role of microRNAs in the skin in order to shine new light on our understanding of cutaneous biology and emphasize the significance of these small, single-stranded RNA molecules in the largest organ of the human body. Key events in epidermal and hair follicle biology, including differentiation, proliferation, and pigmentation, all involve microRNAs. We explore the role of microRNAs in several cutaneous processes, such as appendage formation, wound-healing, epithelial-mesenchymal transition, carcinogenesis, immune response, and aging. In addition, we discuss current trends in research and offer suggestions for future studies.

Circulating miR-200c as a diagnostic and prognostic biomarker for gastric cancer

Background

MicroRNAs are aberrantly expressed and correlate with tumourigenesis and the progression of solid tumours. The miR-200 family determines the epithelial phenotype of cancer cells and regulates invasiveness and migration. Thus, we hypothesised that the quantitative detection of the miR-200 family as epithelial-specific microRNAs in the blood could be a useful clinical biomarker for gastric cancer (GC).

Methods

We initially validated the expression levels of miR-200a, 200b, 200c and 141 in GC cell lines (n = 2) and blood from healthy controls (n = 19) using real-time quantitative reverse transcription PCR (qRT-PCR). The microarray expression profiles of the miR-200 family in 160 paired samples of non-tumour gastric mucosae and GC were downloaded through ArrayExpress and analysed. MiR-200c was selected for clinical validation. The qRT-PCR prospective assessment of miR-200c was performed using 67 blood samples (52 stage I-IV GC patients and 15 controls); the area under the receiver operating characteristic curve (AUC-ROC) was estimated. The Kaplan-Meier and Breslow-Wilcoxon tests were used to assess the correlation of miR-200c with overall and progression-free survival (OS and PFS). Multivariate analyses were performed using the Cox model.

Results

The miR-200c blood expression levels in GC patients were significantly higher than in normal controls (p = 0.018). The AUC-ROC was 0.715 (p = 0.012). The sensitivity, specificity and accuracy rates of 65.4%, 100% and 73.1%, respectively, were observed. The levels of miR-200c in the blood above the cutoff defined by the ROC curve was found in 17.6% of stage I-II GC patients, 20.6% of stage III patients and 67.7% of stage IV patients (p < 0.001). The miR-200c expression levels were not associated with clinical or pathological characteristics or recent surgical procedures. There was a correlation (p = 0.016) with the number of lymph node metastases and the increased expression levels of miR-200c in blood were significantly associated with a poor OS (median OS, 9 vs 24 months; p = 0.016) and PFS (median PFS, 4 vs 11 months; p = 0.044). Multivariate analyses confirmed that the upregulation of miR-200c in the blood was associated with OS (HR = 2.24; p = 0.028) and PFS (HR = 2.27; p = 0.028), independent of clinical covariates.

Conclusions

These data suggest that increased miR-200c levels are detected in the blood of gastric cancer patients. MiR-200c has the potential to be a predictor of progression and survival.

Circulating miRNAs as surrogate markers for circulating tumor cells and prognostic markers in metastatic breast cancer

PURPOSE

The use of circulating tumor cells (CTC) as a prognostic marker in metastatic breast cancer (MBC) has been well established. However, their efficacy and accuracy are still under scrutiny mainly because of methods of their enrichment and identification. We hypothesized that circulating miRNAs can predict the CTC status of patients with MBC, and tested for the same. Furthermore, we aimed at establishing a panel of circulating miRNAs capable of differentiating MBC cases from healthy controls.

EXPERIMENTAL DESIGN

Circulating miRNAs from plasma of CTC-positive and CTC-negative patients with MBC, and healthy controls, were profiled by TaqMan Human MicroRNA arrays. Candidates from the initial screen were validated in an extended cohort of 269 individuals (61 CTC-positive, 72 CTC-negative, 60 CTC-low MBC cases, and 76 controls).

RESULTS

CTC-positive had significantly higher levels of miR-141, miR-200a, miR-200b, miR-200c, miR-203, miR-210, miR-375, and miR-801 than CTC-negative MBC and controls (P < 0.00001), whereas miR-768-3p was present in lower amounts in MBC cases (P < 0.05). miR-200b was singled out as the best marker for distinguishing CTC-positive from CTC-negative patients (AUC 0.88). We identified combinations of miRNAs for differentiating MBC cases from controls (AUC 0.95 for CTC-positive; AUC 0.78 for CTC-negative). Combinations of miRNAs and miR-200b alone were found to be promising prognostic marker for progression-free and overall survival.

CONCLUSION

This is the first study to document the capacity of circulating miRNAs to indicate CTC status and their potential as prognostic markers in patients with MBC.

Distinct roles of AKT isoforms in regulating β1-integrin activity, migration, and invasion in prostate cancer

On the basis of an RNA interference screen, we identify AKT1 and AKT2 as inhibitors of β1-integrin activity and invasion in prostate cancer. AKT1 siRNA induces β-integrin activity and up-regulation of RTKs known to function in cooperation with integrins. In contrast, AKT2 siRNA up-regulates microRNA-200, which increases integrin activity.

AKT1 and AKT2 kinases have been shown to play opposite roles in breast cancer migration and invasion. In this study, an RNA interference screen for integrin activity inhibitors identified AKT1 as an inhibitor of β1-integrin activity in prostate cancer. Validation experiments investigating all three AKT isoforms demonstrated that, unlike in breast cancer, both AKT1 and AKT2 function as negative regulators of cell migration and invasion in PC3 prostate cancer cells. Down-regulation of AKT1 and AKT2, but not AKT3, induced activation of cell surface β1-integrins and enhanced adhesion, migration, and invasion. Silencing of AKT1 and AKT2 also resulted in increased focal adhesion size. Importantly, the mechanisms involved in integrin activity regulation were distinct for the two AKT isoforms. Silencing of AKT1 relieved feedback suppression of the expression and activity of several receptor tyrosine kinases, including EGFR and MET, with established cross-talk with β1-integrins. Silencing of AKT2, on the other hand, induced up-regulation of the microRNA-200 (miR-200) family, and overexpression of miR-200 was sufficient to induce integrin activity and cell migration in PC3 cells. Taken together, these data define an inhibitory role for both AKT1 and AKT2 in prostate cancer migration and invasion and highlight the cell type–specific actions of AKT kinases in the regulation of cell motility.

CXCR7 expression is associated with disease-free and disease-specific survival in cervical cancer patients

BACKGROUND

The CXC chemokine receptor (CXCR)7 is involved in tumour development and metastases formation. The aim of the present study was to determine protein expression of CXCR7, its putative co-receptors epidermal growth factor receptor (EGFR) and CXCR4, its predominant ligand CXCL12, their co-dependency and their association with survival in cervical cancer patients.

METHODS

CXC chemokine receptor 7, EGFR, CXCR4 and CXCL12 expression were determined immunohistochemically in 103 paraffin-embedded, cervical cancers. Subsequently, associations with patient characteristics were assessed and survival analyses were performed.

RESULTS

CXC chemokine receptor 7 was expressed by 43% of tumour specimens, in a large majority of cases together with either EGFR or CXCR4 (double positive), or both (triple positive). The CXCR7 expression was associated with tumour size (P=0.013), lymph node metastasis (P=0.001) and EGFR expression (P=0.009). CXC chemokine receptor 7 was independently associated with disease-free survival (hazard ratio (HR)=4.3, 95% confidence intervals (CI) 1.7-11.0, P=0.002), and strongly associated with disease-specific survival (HR=3.9, 95% CI 1.5-10.2, P=0.005).

CONCLUSION

CXC chemokine receptor 7 expression predicts poor disease-free and disease-specific survival in cervical cancer patients, and might be a promising new therapeutic marker. In a large majority of cases, CXCR7 is co-expressed with CXCR4 and/or EGFR, supporting the hypothesis that these receptors assist in CXCR7 signal transduction.