MiR-487a Promotes TGF-β1-induced EMT,the Migration and Invasion of Breast Cancer Cells by Directly Targeting MAGI2

Tumor metastasis is a complex and multistep process and its exact molecular mechanisms remain unclear. We attempted to find novel microRNAs (miRNAs) contributing to the migration and invasion of breast cancer cells. In this study, we found that the expression of miR-487a was higher in MDA-MB-231breast cancer cells with high metastasis ability than MCF-7 breast cancer cells with low metastasis ability and the treatment with transforming growth factor β1 (TGF-β1) significantly increased the expression of miR-487a in MCF-7 and MDA-MB-231 breast cancer cells. Subsequently, we found that the transfection of miR-487a inhibitor significantly decreased the expression of vimentin, a mesenchymal marker, while increased the expression of E-cadherin, an epithelial marker, in both MCF-7 cells and MDA-MB-231 cells. Also, the inactivation of miR-487a inhibited the migration and invasion of breast cancer cells. Furthermore, our findings demonstrated that miR-487a directly targeted the MAGI2 involved in the stability of PTEN. The down-regulation of miR-487a increased the expression of p-PTEN and PTEN, and reduced the expression of p-AKT in both cell lines. In addition, the results showed that NF-kappaB (p65) significantly increased the miR-487a promoter activity and expression, and TGF-β1 induced the increased miR-487a promoter activity via p65 in MCF-7 cells and MDA-MB-231 cells. Moreover, we further confirmed the expression of miR-487a was positively correlated with the lymph nodes metastasis and negatively correlated with the expression of MAGI2 in human breast cancer tissues. Overall, our results suggested that miR-487a could promote the TGF-β1-induced EMT, the migration and invasion of breast cancer cells by directly targeting MAGI2.     

Wnt pathway targeting reduces triple-negative breast cancer aggressiveness through miRNA regulation in vitro and in vivo

Triple-negative breast cancer, devoid of estrogen (ER), progesterone (PR), and human epidermal growth factor receptor 2 (HER-2) expression, is deprived of commonly used targeted therapies. MicroRNAs (miRNAs) are undergoing a revolution in terms of potentially diagnostic or therapeutic elements. Combining computational approaches, we enriched miRNA binding motifs of Wnt pathway-associated upregulated genes. Our in-depth bioinformatics, in vitro and in vivo analyses indicated that miR-381 targets main genes of the Wnt signaling pathway including CTNNB1, RhoA, ROCK1, and c-MYC genes. The expression level of miR-381 and target genes was assessed by quantitative real-time polymerase chain reaction (RT-qPCR) in MCF-7, MDA-MB-231, and MCF-10A as well as 20 breast cancer samples and normal tissues. Luciferase reporter assay was performed. Lentiviral particles containing miR-381 were used to evaluate the effect of miR-381 restoration on cell proliferation, migration, and invasion of the invasive triple-negative MDA-MB-231 cell line and also in a mouse model of breast cancer. The expression of miR-381 was lower than that of normal cells, especially in TNBC cell line and breast tissues. Luciferase assay results confirmed that miR-381 targets all the predicted 3′-untranslated regions (3′-UTRs). Upon miR-381 overexpression, the expression of target genes declined, and the migration and invasion potential of miR-381-receiving MDA-MB-231 cells decreased. In a mouse model of triple-negative breast cancer, miR-381 re-expression inhibited the invasion of cancer cells to lung and liver and prolonged the survival time of cancer cell-bearing mice. Therefore, miR-381 is a regulator of Wnt signaling and its re-expression provides a potentially effective strategy for inhibition of TNBC.     

BMP9 inhibits the bone metastasis of breast cancer cells by downregulating CCN2 (connective tissue growth factor,CTGF) expression

Bone morphogenetic proteins (BMPs), which belong to the transforming growth factor-β superfamily, regulate a wide range of cellular responses including cell proliferation, differentiation, adhesion, migration, and apoptosis. BMP9, the latest BMP to be discovered, is reportedly expressed in a variety of human carcinoma cell lines, but the role of BMP9 in breast cancer has not been fully clarified. In a previous study, BMP9 was found to inhibit the growth, migration, and invasiveness of MDA-MB-231 breast cancer cells. In the current study, the effect of BMP9 on the bone metastasis of breast cancer cells was investigated. After absent or low expression of BMP9 was detected in the MDA-MB-231 breast cancer cells and breast non-tumor adjacent tissues using Western blot and immunohistochemistry, In our previous study, BMP9 could inhibit the proliferation and invasiveness of breast cancer cells MDA-MB-231 in vitro and in vivo. This paper shows that BMP9 inhibit the bone metastasis of breast cancer cells by activating the BMP/Smad signaling pathway and downregulating connective tissue growth factor (CTGF); however, when CTGF expression was maintained, the inhibitory effect of BMP9 on the MDA-MB-231 cells was abolished. Together, these observations indicate that BMP9 is an important mediator of breast cancer bone metastasis and a potential therapeutic target for treating this deadly disease.     

MiR-5047在乳腺癌细胞增殖迁移中的作用及表达调控*

探讨miR-5047在乳腺癌细胞中的表达及其在乳腺癌细胞增殖和迁移中的作用,并明确地西他滨在miR-5047表达调控中的作用。通过实时荧光定量PCR(qRT-PCR)检测人乳腺癌细胞系和正常乳腺上皮细胞MCF10A中miR-5047的表达水平;将miR-5047模拟物(mimic),阴性对照(NC)分别转染至MDA-MB-231和MCF7细胞,经平板克隆实验、MTT实验、划痕愈合实验检测乳腺癌细胞的增殖和迁移能力,通过qRT-PCR和Western blot检测相关基因表达及蛋白水平。使用浓度5 μmol/L和10 μmol/L的地西他滨分别处理MDA-MB-231和MCF-7细胞,经qRT-PCR检测不同浓度和处理时间条件下地西他滨对miR-5047表达的影响。同时,通过形态观察和Western blot检测地西他滨对乳腺癌细胞上皮间质转化的影响。与正常乳腺上皮细胞MCF-10A相比,miR-5047在乳腺癌细胞中表达均显著下调。miR-5047过表达可显著抑制乳腺癌细胞的增殖和迁移,促进上皮细胞标志物E-cadherin的表达,抑制间质细胞标志物Vimentin的表达。不同浓度地西他滨处理MDA-MB-231和MCF7细胞后,miR-5047表达均增强,且10 μmol/L作用48 h效果最显著。地西他滨可诱导MDA-MB-231细胞向上皮样转变。miR-5047在乳腺癌细胞系中表达显著下调,过表达miR-5047可抑制乳腺癌细胞的增殖和迁移,地西他滨可促进乳腺癌细胞中miR-5047的表达,并诱导细胞向上皮样转变。     

Role of ornithine decarboxylase in breast cancer

Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis that decarboxylates ornithine to putrescine, has become a promising target for cancer research. The aim of this study is to investigate the role of ODC in breast cancer. We detected expression of ODC in breast cancer tissues and four breast cancer cell lines, and transfected breast cancer cells with an adenoviral vector carrying antisense ODC (rAd-ODC/Ex3as) and examined their growth and migration. ODC was overexpressed in breast cancer tissues and cell lines compared with non-tumor tissues and normal breast epithelial cells, and there was a positive correlation between the level of ODC mRNA and the staging of tumors. The expression of ODC correlated with cyclin D1, a cell cycle protein, in synchronized breast cancer MDA-MB-231 cells. Gene transfection of rAd-ODC/Ex3as markedly down-regulated expression of ODC and cyclin D1, resulting in suppression of proliferation and cell cycle arrest at G₀–G₁ phase, and the inhibition of colony formation, an anchorage-independent growth pattern, and the migratory ability of MDA-MB-231 cells. rAd-ODC/Ex3as also markedly reduced the concentration of putrescine, but not spermidine or spermine, in MDA-MB-231 cells. The results suggested that the ODC gene might act as a prognostic factor for breast cancer and it could be a promising therapeutic target.     

Phosphorylation of DARPP-32 regulates breast cancer cell migration downstream of the receptor tyrosine kinase DDR1

Cell migration plays a central role in processes such as development, wound healing and cancer metastasis. Here we describe a novel interaction between DDR1, a receptor tyrosine kinase activated by collagen, and the phosphoprotein DARPP-32 in mammary epithelial cells. DARPP-32 expression was readily detected in non-transformed mammary cell lines, but was strongly reduced or even absent in breast tumor cell lines, such as MCF7. Transfection of MCF7 cells with DARPP-32 resulted in severely impaired cell migration, while DARPP-32 transfection into the DDR1-deficient breast cancer cell line MDA-MB-231 did not alter migration. Co-expression of both DDR1 and DARPP-32 in MDA-MB-231 cells inhibited migration, thereby supporting a critical role of the DDR1/DARPP-32 complex in motility. Mutational substitution of the phosphorylation sites Thr-34 or Thr-75 on DARPP-32 revealed that phosphorylation of Thr-34 is necessary for the ability of DARPP-32 to impair breast tumor cell migration. Thus, DARPP-32 signaling downstream of DDR1 is a potential new target for effective anti-metastatic breast cancer therapy.     

Evaluation of exosomal miR-9 and miR-155 targeting PTEN and DUSP14 in highly metastatic breast cancer and their effect on low metastatic cells

Breast cancer is one of the most prevalent cancers in women. Triple-negative breast cancer consists 15% to 20% of breast cancer cases and has a poor prognosis. Cancerous transformation has several causes one of which is dysregulation of microRNAs (miRNAs) expression. Exosomes can transfer miRNAs to neighboring and distant cells. Thus, exosomal miRNAs can transfer cancerous phenotype to distant cells. We used gene expression omnibus (GEO) datasets and miRNA target prediction tools to find overexpressed miRNA in breast cancer cells and their target genes, respectively. Exosomes were extracted from MDA-MB-231 and MCF-7 cells and characterized. Overexpression of the miRNAs of MDA-MB-231 cells and their exosomes were analyzed using quantitative Real-time PCR. The target genes expression was also evaluated in the cell lines. Luciferase assay was performed to confirm the miRNAs: mRNAs interactions. Finally, MCF-7 cells were treated with MDA-MB-231 cells’ exosomes. The target genes expression was evaluated in the recipient cells. GSE60714 results indicated that miR-9 and miR-155 were among the overexpressed miRNAs in highly metastatic triple negative breast cancer cells and their exosomes. Bioinformatic studies showed that these two miRNAs target PTEN and DUSP14 tumor suppressor genes. Quantitative Real-time PCR confirmed the overexpression of the miRNAs and downregulation of their targets. Luciferase assay confirmed that the miRNAs target PTEN and DUSP14. Treatment of MCF-7 cells with MDA-MB-231 cells’ exosomes resulted in target genes downregulation in MCF-7 cells. We found that miR-9 and miR-155 were enriched in metastatic breast cancer exosomes. Therefore, exosomal miRNAs can transfer from cancer cells to other cells and can suppress their target genes in the recipient cells.     

MicroRNA-224 targets RKIP to control cell invasion and expression of metastasis genes in human breast cancer cells

The Raf kinase inhibitor protein (RKIP) is a tumor suppressor that protects against metastasis and genomic instability. RKIP is downregulated in many types of tumors, although the mechanism for this remains unknown. MicroRNAs silence target genes via translational inhibition or target mRNA degradation, and are thus important regulators of gene expression. In the current study, we found that miR-224 expression is significantly upregulated in breast cancer cell lines, and especially in highly invasive MDA-MB-231 cells, compared to human normal breast epithelial cells. In addition, miR-224 inhibits RKIP gene expression by directly targeting its 3'-untranslated region (3'-UTR). Moreover, metastasis, as assayed by Transwell migration, 3D growth in Matrigel, and wound healing, was enhanced by ectopic expression of miR-224 and inhibited by miR-224 downregulation. Promotion of metastasis in response to miR-224 downregulation was associated with derepression of the stroma-associated RKIP target genes, CXCR4, MMP1, and OPN, which are involved in breast tumor metastasis to the bone. Taken together, our data indicate that miR-224 play an important role in metastasis of human breast cancer cells to the bone by directly suppressing the RKIP tumor suppressor.     

MicroRNA-125b induces metastasis by targeting STARD13 in MCF-7 and MDA-MB-231 breast cancer cells

MicroRNAs (miRNAs) are a class of small noncoding RNAs that regulate gene expression by targeting mRNAs to trigger either translation repression or mRNA degradation. miR-125b is down-regulated in human breast cancer cells compared with the normal ones except highly metastatic tumor cells MDA-MB-231. However, few functional studies were designed to investigate metastatic potential of miR-125b. In this study, the effects of miR-125b on metastasis in human breast cancer cells were studied, and the targets of miR-125b were also explored. Transwell migration assay, cell wound healing assay, adhesion assay and nude mice model of metastasis were utilized to investigate the effects of miR-125b on metastasis potential in vitro and in vivo. In addition, it was implied STARD13 (DLC2) was a direct target of miR-125b by Target-Scan analysis, luciferase reporter assay and western blot. Furthermore, activation of STARD13 was identified responsible for metastasis induced by miR-125b through a siRNA targeting STARD13. qRT-PCR, immunofluorescent assay and western blot was used to observe the variation of Vimentin and α-SMA in breast cancer cells. In summary, our study provided new insights into the function of miR-125b during the metastasis of breat cancer cells and also suggested the role of miR-125b in pro-metastasis by targeting STARD13.     

MicroRNA-335 suppresses the proliferation,migration, and invasion of breast cancer cells by targeting EphA4

MicroRNAs (miRNAs) are small noncoding RNAs that exert their functions by targeting specific mRNA sequences. Many studies have demonstrated that miRNAs are crucial for cancer progression, during which they can act as either oncogenes or tumor suppressors. Previous research has shown that miR-335 is downregulated in breast cancer, and it has been shown to be a breast cancer suppressor. In addition, emerging evidence indicates that erythropoietin-producing hepatocellular A4 (EphA4) is implicated in cancer cell proliferation, migration, and invasion. However, little is known about the relationship between miR-335 and EphA4 in breast cancer. In the present study, we used bioinformatic and biochemical analyses to demonstrate that EphA4 is a direct downstream target of miR-335 in human breast cancer MCF-7 and MDA-MB-23 cells and revealed that miR-335 negatively regulates the expression of EphA4 in these cells. Further investigation revealed that miR-335 overexpression inhibits MCF-7 and MDA-MB-231 cell proliferation and that this inhibition is attenuated by EphA4 coexpression. Similarly, miR-335 overexpression also inhibited growth and downregulated EphA4 expression in tumors in nude mice. Moreover, our results demonstrated that miR-335 overexpression suppresses migration and invasion in MCF-7 and MDA-MB-231 cells, an effect that was reversed by EphA4 overexpression. These findings confirmed that EphA4 is a direct target gene of miR-335 and that miR-335 suppresses breast cancer cell proliferation and motility in part by directly inhibiting EphA4 expression.     

miR-29b regulates migration of human breast cancer cells

microRNAs (miRNAs) are short non-coding RNAs that regulate gene expression by targeting mRNAs, inhibiting the expression of the associated proteins. Although a role for aberrant miRNA expression in cancer has been postulated, the pathophysiologic role and relevance of aberrantly expressed miRNAs in tumor biology has not been established. We evaluated the expression pattern of miRNAs in human breast cancer cells by qPCR, finding out an up-regulated miRNA miR-29b and studying its biological effect by migration assay. We defined a target gene PTEN by bioinformatics approach and western blot. In breast cancer cell line MDA-MB-231 cell, which migrate faster than MCF-7, we observed that miR-29b was highly over-expressed. Inhibition of miR-29b in cultured cells increased the expression of the phosphatase and tensin homolog (PTEN) tumor suppressor, promoting apoptosis, decreasing migration, and decreasing invasion. In contrast, enhanced miR-29b expression by transfection with pre-miR-29b decreased the expression of PTEN and impaired apoptosis, increasing tumor cell migration and invasion. Moreover, PTEN was shown to be a direct target of miR-29b and was also shown to contribute to the miR-29b-mediated effects on cell invasion. Modulation of miR-29b altered the role of PTEN involved in cell migration and invasion. Aberrant expression of miR-29b, which modulates PTEN expression, can contribute to migration, invasion, and anti-apoptosis.     

Adenosine arrests breast cancer cell motility by A3 receptor stimulation

In neutrophils, adenosine triphosphate (ATP) release and autocrine purinergic signaling regulate coordinated cell motility during chemotaxis. Here, we studied whether similar mechanisms regulate the motility of breast cancer cells. While neutrophils and benign human mammary epithelial cells (HMEC) form a single leading edge, MDA-MB-231 breast cancer cells possess multiple leading edges enriched with A3 adenosine receptors. Compared to HMEC, MDA-MB-231 cells overexpress the ectonucleotidases ENPP1 and CD73, which convert extracellular ATP released by the cells to adenosine that stimulates A3 receptors and promotes cell migration with frequent directional changes. However, exogenous adenosine added to breast cancer cells or the A3 receptor agonist IB-MECA dose-dependently arrested cell motility by simultaneous stimulation of multiple leading edges, doubling cell surface areas and significantly reducing migration velocity by up to 75 %. We conclude that MDA-MB-231 cells, HMEC, and neutrophils differ in the purinergic signaling mechanisms that regulate their motility patterns and that the subcellular distribution of A3 adenosine receptors in MDA-MB-231 breast cancer cells contributes to dysfunctional cell motility. These findings imply that purinergic signaling mechanisms may be potential therapeutic targets to interfere with the motility of breast cancer cells in order to reduce the spread of cancer cells and the risk of metastasis.     

An actin-binding protein ESPN is an independent prognosticator and regulates cell growth for esophageal squamous cell carcinoma

Breast cancer has been the first death cause of cancer in women all over the world. Metastasis is believed to be the most important process for treating breast cancer. There is evidence that lncRNA MEG3 functions as a tumor suppressor in breast cancer metastasis. However, upstream regulation of MEG3 in breast cancer remain elusive. Therefore, it is critical to elucidate the underlying mechanism upstream MEG3 to regulate breast cancer metastasis. We employed RT-qPCR and Western blot to examine expression level of miR-506, DNMT1, SP1, SP3 and MEG3. Besides, methylation-specific PCR was used to determine the methylation level of MEG3 promoter. Wound healing assay and transwell invasion assay were utilized to measure migration and invasion ability of breast cancer cells, respectively. SP was upregulated while miR-506 and MEG3 were downregulated in breast tumor tissue compared to adjacent normal breast tissues. In addition, we found that miR-506 regulated DNMT1 expression in an SP1/SP3-dependent manner, which reduced methylation level of MEG3 promoter and upregulated MEG3 expression. SP3 knockdown or miR-506 mimic suppressed migration and invasion of MCF-7 and MDA-MB-231 cells whereas overexpression of SP3 compromised miR-506-inhibited migration and invasion. Our data reveal a novel axis of miR-506/SP3/SP1/DNMT1/MEG3 in regulating migration and invasion of breast cancer cell lines, which provide rationales for developing effective therapies to treating metastatic breast cancers.     

Suppressive effect of exogenous miR-16 and miR-34a on tumorigenesis of breast cancer cells

Recent investigations have shown tumor-suppressive roles for miR-16 and miR-34a. They also share some features in regard to targeting cancer cell signaling pathways which they control. Therefore, in this study, we aimed to further scrutinize whether exogenous induction of mature miR-34a and miR-16 can collaborate in breast tumor suppression. MDA-MB-231 and SK-BR-3 human breast cancer cell lines were cultured and transfected twice with hsa-miR-16-5p and hsa-miR-34a-5p mimics individually or in combination. The cells were analyzed for apoptosis rate and cell cycle indices by flow cytometry. Also, the expression of several invasion and the epithelial-mesenchymal transition markers was evaluated at gene and protein levels by quantitative real-time polymerase chain reaction and western blot analysis, respectively. Assessment of invasiveness and migratory potential of the transfected cells was performed using three-dimensional spheroid formation and wound-healing assay, respectively. In both cell lines, miR-16 and miR-34a induced apoptosis and cell-cycle arrest and also suppressed invasion and migration. Some of these effects, like cell-cycle arrest and induction of apoptosis, were significantly higher when using both microRNAs than when using them individually for transfection of the cells. Our results are indicating that miR-16 and miR-34a can collaborate in breast tumor suppression.     

miR-188-5p suppresses cellular proliferation and migration via IL6ST: A potential noninvasive diagnostic biomarker for breast cancer

Previously, serum miR-188-5p is differentially expressed in breast cancer, but the diagnostic potential of circulating miR-188-5p as well as its regulatory mechanism in breast cancer remain uncertain. Herein, serum miR-188-5p was detected by real-time polymerase chain reaction in patients with breast cancer, breast fibroadenoma, and healthy subjects. Circulating miR-188-5p was abnormally elevated in patients with breast cancer as compared with these other two groups, and was reduced in patients with breast cancer following surgical treatment. Increased serum miR-188-5p corresponded to lymph node metastasis status and TNM stages of breast cancer. A receiver operating characteristic curve analysis of the ability to circulate miR-188-5p to distinguish between patients with breast cancer and either noncancerous patients or patients with breast fibroadenoma yielded corresponding areas under the curve of 0.894 and 8.814. miR-188-5p was downregulated in the highly malignant cancer line MDA-MB-231 relative to the less malignant MCF-7 cells. In vitro, functional analyses conducted via transfecting cells with mimics and inhibitors revealed miR-188-5p to suppress breast cancer cell proliferation and migration, which was mediated by its downstream target IL6ST. Comparison of intracellular and exosomal miR-188-5p levels indicated that miR-188-5p was selectively sorted into exosomes derived from MDA-MB-231 cells rather than those from MCF-7 cells. However, exosomal miR-188-5p levels in the serum of patients with breast cancer were reduced compared to healthy controls and did not differ relative to patients with breast fibroadenoma. In summary, miR-188-5p acts in a tumor-suppressive manner in breast cancer progression and may serve as a noninvasive early diagnostic biomarker and therapeutic target in breast cancer.     

Livin promotes progression of breast cancer through induction of epithelial–mesenchymal transition and activation of AKT signaling

The inhibitor of apoptosis proteins (IAP) are closely correlated with proliferation, apoptosis, motility, and metastasis. Livin is the most recently identified IAP, and its role in breast progression remains unknown. In our study, analyses of 50 patients with breast cancer revealed that the positive expression rate of Livin was higher in breast cancer tissues (62%) relative to that in adjacent (35%) and normal tissues (25%). Livin expression in breast cancer correlated with the clinical stage and axillary lymph node metastasis and could be used as a prognostic marker. Our in vitro experiment revealed that Livin was highly expressed in high-invasive MDA-MB-231 cells as compared to low-invasive cells (MCF-7). Suppression of Livin by short-hairpin RNA reduced the Livin expression of MDA-MB-231 cells and subsequently inhibited tumor cell growth, proliferation, and colony formation and induced tumor cell apoptosis, motility, migration, and invasion. Overexpression of Livin in MCF7 cells resulted in increased migration and invasion capabilities of the cells without affecting proliferation and apoptosis. In addition, epithelial–mesenchymal transition (EMT) was induced by Livin expression in breast cancer cell lines. The high level of phosphorylated AKT in MDA-MB-231 cells was suppressed by Livin knockdown. Further, Livin-induced migration and invasion could be abolished by either the application of the phosphoinositide-3-kinase inhibitor LY294002 or knockdown of AKT expression using small-interfering RNA. In conclusion, Livin serves as an independent prognostic indicator for breast cancer. Livin expression promotes breast cancer metastasis through the activation of AKT signaling and induction of EMT in breast cancer cells both in vitro and in vivo.