MicroRNA-503 represses epithelial–mesenchymal transition and inhibits metastasis of osteosarcoma by targeting c-myb

Regulation of the Epithelial to Mesenchymal Transition in Osteosarcoma

The epithelial to mesenchymal transition (EMT) is a cellular process that has been linked to the promotion of aggressive cellular features in many cancer types. It is characterized by the loss of the epithelial cell phenotype and a shift to a more mesenchymal phenotype and is accompanied by an associated change in cell markers. EMT is highly complex and regulated via multiple signaling pathways. While the importance of EMT is classically described for carcinomas-cancers of epithelial origin-it has also been clearly demonstrated in non-epithelial cancers, including osteosarcoma (OS), a primary bone cancer predominantly affecting children and young adults. Recent studies examining EMT in OS have highlighted regulatory roles for multiple proteins, non-coding nucleic acids, and components of the tumor micro-environment. This review serves to summarize these experimental findings, identify key families of regulatory molecules, and identify potential therapeutic targets specific to the EMT process in OS.

Transcription factor c-Myb: novel prognostic factor in osteosarcoma

The transcription factor c-Myb is an oncoprotein promoting cell proliferation and survival when aberrantly activated/expressed, thus contributing to malignant transformation. Overexpression of c-Myb has been found in leukemias, breast, colon and adenoid cystic carcinoma. Recent studies revealed its expression also in osteosarcoma cell lines and suggested its functional importance during bone development. However, the relevance of c-Myb in control of osteosarcoma progression remains unknown. A retrospective clinical study was carried out to assess a relationship between c-Myb expression in archival osteosarcoma tissues and prognosis in a cohort of high-grade osteosarcoma patients. In addition, MYB was depleted in metastatic osteosarcoma cell lines SAOS-2 LM5 and 143B and their growth, chemosensitivity, migration and metastatic activity were determined. Immunohistochemical analysis revealed that high c-Myb expression was significantly associated with poor overall survival in the cohort and metastatic progression in young patients. Increased level of c-Myb was detected in metastatic osteosarcoma cell lines and its depletion suppressed their growth, colony-forming capacity, migration and chemoresistance in vitro in a cell line-dependent manner. MYB knock-out resulted in reduced metastatic activity of both SAOS-2 LM5 and 143B cell lines in immunodeficient mice. Transcriptomic analysis revealed the c-Myb-driven functional programs enriched for genes involved in the regulation of cell growth, stress response, cell adhesion and cell differentiation/morphogenesis. Wnt signaling pathway was identified as c-Myb target in osteosarcoma cells. Taken together, we identified c-Myb as a negative prognostic factor in osteosarcoma and showed its involvement in the regulation of osteosarcoma cell growth, chemosensitivity, migration and metastatic activity.

The microRNA-424/503 cluster: A master regulator of tumorigenesis and tumor progression with paradoxical roles in cancer

MicroRNAs (miRNAs) are a group of non-coding RNAs that play a crucial role in post-transcriptional gene regulation and act as indispensable mediators in several critical biological processes, including tumorigenesis, tissue homeostasis, and regeneration. MiR-424 and miR-503 are intragenic miRNAs that are clustered on human chromosome Xq26.3. Previous studies have reported that both miRNAs are dysregulated and play crucial but paradoxical roles in tumor initiation and progression, involving different target genes and molecular pathways. Moreover, these two miRNAs are concomitantly expressed in several cancer cells, indicating a coordinating function as a cluster. In this review, the roles and regulatory mechanisms of miR-424, miR-503, and miR-424/503 cluster are summarized in different types of cancers.

miR-200 affects tamoxifen resistance in breast cancer cells through regulation of MYB

Resistance to tamoxifen is a major clinical challenge. Research in recent years has identified epigenetic changes as mediated by dysregulated miRNAs that can possibly play a role in resistance to tamoxifen in breast cancer patients expressing estrogen receptor (ER). We report here elevated levels of EMT markers (vimentin and ZEB1/2) and reduced levels of EMT-regulating miR-200 (miR-200b and miR-200c) in ER-positive breast cancer cells, MCF-7, that were resistant to tamoxifen, in contrast with the naïve parental MCF-7 cells that were sensitive to tamoxifen. Further, we established regulation of c-MYB by miR-200 in our experimental model. C-MYB was up-regulated in tamoxifen resistant cells and its silencing significantly decreased resistance to tamoxifen and the EMT markers. Forced over-expression of miR-200b/c reduced c-MYB whereas reduced expression of miR-200b/c resulted in increased c-MYB We further confirmed the results in other ER-positive breast cancer cells T47D cells where forced over-expression of c-MYB resulted in induction of EMT and significantly increased resistance to tamoxifen. Thus, we identify a novel mechanism of tamoxifen resistance in breast tumor microenvironment that involves miR-200-MYB signaling.

miRNA signatures in childhood sarcomas and their clinical implications

Progresses in multimodal treatments have significantly improved the outcomes for childhood cancer. Nonetheless, for about one-third of patients with Ewing sarcoma, rhabdomyosarcoma, or osteosarcoma steady remission has remained intangible. Thus, new biomarkers to improve early diagnosis and the development of precision-targeted medicine remain imperative. Over the last decade, remarkable progress has been made in the basic understanding of miRNAs function and in interpreting the contribution of their dysregulation to cancer development and progression. On this basis, this review focuses on what has been learned about the pivotal roles of miRNAs in the regulation of key genes implicated in childhood sarcomas.

Overexpression of carbonyl reductase 1 inhibits malignant behaviors and epithelial mesenchymal transition by suppressing TGF-β signaling in uterine leiomyosarcoma cells

Carbonyl reductase 1 (CBR1) has been reported to be involved in cancer progression. Recently, we found that CBR1 overexpression inhibited malignant behaviors and the epithelial mesenchymal transition (EMT) in uterine cervical cancer. It remained unclear whether this was also the case in uterine leiomyosarcoma (uLMS), which is derived from mesenchymal cells and is a much more malignant gynecological tumor. A number of previous studies suggested that malignant behaviors are associated with EMT, even in mesenchymal malignant tumors. In the present study, we investigated whether CBR1 inhibits malignant behaviors and EMT in uLMS. We established clones of uLMS cells (SKN cells) and uterine sarcoma cells (MES-SA cells) that overexpressed CBR1. Cell proliferative, migratory and invasive activities were suppressed by CBR1 overexpression, accompanied by increases in the expressions of epithelial markers (E-cadherin and cytokeratin) and decreases in the expressions of mesenchymal markers (N-cadherin and fibronectin), suggesting that CBR1 overexpression inhibits malignant behaviors and EMT in uLMS cells. In addition, transforming growth factor-β (TGF-β) production and the subsequent signaling and phosphorylation of Smad were suppressed in the clones. To investigate the association between TGF-β and EMT, SKN cells were treated with TGF-β or a TGF-β receptor blocker (SB431542). EMT was promoted by TGF-β and inhibited by SB431542. In conclusion, this is the first study, to the best of the authors' knowledge, showing that CBR1 overexpression inhibits malignant behaviors and EMT in uLMS cells. The present study provided novel insight demonstrating that the suppressive effect of CBR1 is mediated through TGF-β signaling.

HER2 and p95HER2 differentially regulate miRNA expression in MCF-7 breast cancer cells and downregulate MYB proteins through miR-221/222 and miR-503

The HER2 oncogene and its truncated form p95HER2 play central roles in breast cancer. Here, we show that although HER2 and p95HER2 generally elicit qualitatively similar changes in miRNA profile in MCF-7 breast cancer cells, a subset of changes are distinct and p95HER2 shifts the miRNA profile towards the basal breast cancer subtype. High-throughput miRNA profiling was carried out 15, 36 and 60 h after HER2 or p95HER2 expression and central hits validated by RT-qPCR. miRNAs strongly regulated by p95HER2 yet not by HER2, included miR-221, miR-222, miR-503, miR-29a, miR-149, miR-196 and miR-361. Estrogen receptor-α (ESR1) expression was essentially ablated by p95HER2 expression, in a manner recapitulated by miR-221/-222 mimics. c-Myb family transcription factors MYB and MYBL1, but not MYBL2, were downregulated by p95HER2 and by miR-503 or miR-221/-222 mimics. MYBL1 3′UTR inhibition by miR-221/222 was lost by deletion of a single putative miR-221/222 binding sites. p95HER2 expression, or knockdown of either MYB protein, elicited upregulation of tissue inhibitor of matrix metalloprotease-2 (TIMP2). miR-221/222 and -503 mimics increased, and TIMP2 knockdown decreased, cell migration and invasion. A similar pathway was operational in T47D- and SKBr-3 cells. This work reveals important differences between HER2- and p95HER2- mediated miRNA changes in breast cancer cells, provides novel mechanistic insight into regulation of MYB family transcription factors by p95HER2, and points to a role for a miR-221/222– MYB family–TIMP2 axis in regulation of motility in breast cancer cells.

Long Noncoding RNA miR210HG Sponges miR-503 to Facilitate Osteosarcoma Cell Invasion and Metastasis

Long noncoding RNAs (lncRNAs) have been illustrated to function as important regulator in carcinogenesis and cancer progression. However, roles of lncRNA miR210HG (miR210 host gene) in osteosarcoma remain unclear. In this study, miR210HG expression level was significantly upregulated in 55 cases of osteosarcoma tissue samples compared to adjacent normal tissue. Besides, the aberrantly enhanced miR210HG expression predicted poor prognosis and lower survival rate. In vitro, miR210HG knockdown suppressed the osteosarcoma cell proliferation, invasion, and epithelial-mesenchymal transition-related marker (N-cadherin and vimentin) expression. In vivo, miR210HG silencing decreased the tumor growth. miR-503 was verified to be the target miRNA of miR210HG using bioinformatics online program and luciferase assay. Furthermore, miR-503 could reverse the role of miR210HG on osteosarcoma cells. In conclusion, our study indicates that miR210HG sponges miR-503 to facilitate osteosarcoma cell invasion and metastasis, revealing the oncogenic role of miR210HG on osteosarcoma cells.

MicroRNA-138 directly targets TNFAIP8 and acts as a tumor suppressor in osteosarcoma

MicroRNAs (miRs) have a critical role in the development and malignant progression of osteosarcoma (OS), but the underlying mechanisms have largely remained elusive. The present study aimed to explore the regulatory role of miR-138 in OS growth and metastasis and investigated the associated mechanisms. Reverse-transcription quantitative polymerase chain reaction and western blot analysis were performed to examine the miR-138 and protein expression levels in OS and normal bone tissues and cell lines. An MTT assay and a Transwell assay were used to assess cell proliferation and invasion. Flow cytometry was used to analyze the cell cycle and determine the apoptotic rate. A luciferase reporter assay was used to confirm the targeting association between miR-138 and tumor necrosis factor-α-induced protein 8 (TNFAIP8). It was found that miR-138 was downregulated in OS tissues and cell lines. Overexpression of miR-138 decreased the proliferation, cell cycle progression and invasion of OS cells, while inducing cell apoptosis. TNFAIP8 was then identified as a novel target of miR-138. Similarly to the effects of miR-138 overexpression, inhibition of TNFAIP8 also inhibited OS cell proliferation, cell cycle progression and invasion, and induced cell apoptosis. In addition, miR-138 overexpression as well as downregulation of TNFAIP8 reduced OS cell invasion via inhibition of matrix metalloproteinase-2 and −9 expression. Taken together, the results of the present study demonstrated that miR-138 directly targets TNFAIP8 and acts as a tumor suppressor in OS, suggesting that the miR-138/TNFAIP8 interaction may become a promising therapeutic target for OS.

MicroRNA-503 suppresses cell proliferation and invasion in osteosarcoma via targeting insulin-like growth factor 1 receptor

MicroRNAs (miRs) are a class of small non-coding RNAs and have key roles in various cancer types. Recently, miR-503 has been reported to act as a tumor suppressor in osteosarcoma. However, the detailed mechanism of the regulatory role of miR-503 in osteosarcoma cell proliferation and invasion has largely remained elusive. The present study found that miR-503 was significantly downregulated in osteosarcoma tissues compared to that in matched adjacent non-tumorous tissues. In addition, the expression of miR-503 in osteosarcoma of T3-T4 stage was significantly lower when compared with that in T1-T2 stage samples. miR-503 was also downregulated in osteosarcoma cell lines (Saos-2, MG63, U2OS and SW1353), when compared with that in the normal osteoblast cell line hFOB. Overexpression of miR-503 significantly inhibited the proliferation and invasion of U2OS cells and decreased the protein levels of insulin-like growth factor 1 receptor (IGF-1R), which was further identified as a novel target of miR-503 by a luciferase reporter assay. Moreover, overexpression of IGF-1R eliminated the suppressive effects of miR-503 on the proliferation and invasion of U2OS cells, suggesting that miR-503 inhibits osteosarcoma cell proliferation and invasion by directly targeting IGF-1R. Furthermore, IGF-1R was significantly upregulated in osteosarcoma tissues compared with that in adjacent non-tumor tissues, as well as in osteosarcoma cell lines compared with that in hFOB cells. In addition, the expression levels of IGF-1R were inversely correlated to the miR-503 levels in osteosarcoma tissues, suggesting that the increased IGF-1R expression may be caused by the reduced expression of miR-503. In conclusion, the present study demonstrated that miR-503 suppresses cell proliferation and invasion in osteosarcoma via targeting IGF-1R and thus highlights the importance of miR-503/IGF-1R signaling in the malignant progression of osteosarcoma.

Downregulation of miR-503 Promotes ESCC Cell Proliferation, Migration, and Invasion by Targeting Cyclin D1

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive cancers in China, but the underlying molecular mechanism of ESCC is still unclear. Involvement of microRNAs has been demonstrated in cancer initiation and progression. Despite the reported function of miR-503 in several human cancers, its detailed anti-oncogenic role and clinical significance in ESCC remain undefined. In this study, we examined miR-503 expression by qPCR and found the downregulation of miR-503 expression in ESCC tissue relative to adjacent normal tissues. Further investigation in the effect of miR-503 on ESCC cell proliferation, migration, and invasion showed that enhanced expression of miR-503 inhibited ESCC aggressive phenotype and overexpression of CCND1 reversed the effect of miR-503-mediated ESCC cell aggressive phenotype. Our study further identified CCND1 as the target gene of miR-503. Thus, miR-503 functions as a tumor suppressor and has an important role in ESCC by targeting CCND1.

MiR-503 Promotes Bone Formation in Distraction Osteogenesis through Suppressing Smurf1 Expression

Distraction osteogenesis (DO) is a unique technique for promoting bone formation in clinical practice. However the underlying mechanism remains elusive. As epigenetic mediators, microRNAs have been reported to play important roles in regulating osteogenesis. In this study, after successfully established the DO model of rats, a microRNA microarray was performed to find molecular targets for DO. Total 100 microRNAs were identified as differently expressed, with miR-503 being one of the most significantly up-regulated miRNAs in DO. The further investigation also showed that miR-503 was upregulated during osteogenesis in mesenchymal stem cells of rats, and overexpression of miR-503 significantly promoted osteogenesis in vitro and accelerated mineralization in DO process in vivo. By using bioinformatic investigations and luciferase activities, we successfully demonstrated that Smurf1, a negative regulator of osteogenesis, was a real target of miR-503. Furthermore, Smurf1 knockdown promoted osteogenesis and antagomir-503 abolished the promotive effect, suggesting that miR-503 mediated osteogenic differentiation via suppressing Smurf1 expression. To sum up, these findings indicated that miR-503 promoted osteogenesis and accelerated bone formation, which may shed light on the development for a potential therapeutic target for bone repair.

Sex-determining region Y-box protein 3 induces epithelial-mesenchymal transition in osteosarcoma cells via transcriptional activation of Snail1

Background

The transcription factor sex-determining region Y-box protein 3 (SOX3) plays important roles in various types of cancer. However, its expression and function have not yet been elucidated in osteosarcoma (OS).

Methods

The expression levels of SOX3 in OS tissues and OS cell lines were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis. The effects of SOX3 expression on OS cell biological traits were investigated by overexpressing and downregulating SOX3 protein. The expression of epithelial-mesenchymal transition (EMT) markers and transcription factors associated with EMT (EMT-TFs), were detected simultaneously. The mechanism underlying SOX3-mediated Snail1 expression was further investigated.

Results

SOX3 was upregulated in human OS tissues. SOX3 overexpression promoted the EMT, migration and invasion in OS cells. The downregulation of SOX3 resulted in opposing effects. Furthermore, SOX3 upregulation enhanced the expression of the transcriptional repressor Snail1 by binding to its promoter region. Additionally, a positive correlation among the expression of SOX3, Snail1, and E-cadherin was demonstrated in human OS tissues.

Conclusions

SOX3 promotes migration, invasiveness, and EMT in OS cells via transcriptional activation of Snail1 expression, suggesting that SOX3 is a novel regulator of EMT in OS and may serve as a therapeutic target for the treatment of OS metastasis.

Role of miRNAs in human cancer metastasis: Implications for therapeutic intervention

Metastasis is the spread and growth of localized cancer to new locations in the body and is considered the main cause of cancer-related deaths. Metastatic cancer cells display distinct genomic and epigenomic profiles and almost universally an aggressive pathophysiology. A better understanding of the molecular mechanisms and regulation of metastasis, including how metastatic tumors grow and survive in the nascent niche and the interactions of the emergent metastatic cancer cells within the local microenvironment may provide tools to design strategies to restrict metastatic dissemination. Aberrant microRNAs (miRNA) expression has been reported in metastatic cancer cells. MicroRNAs are known to regulate divergent and/or convergent metastatic gene pathways including activation of reprogramming switches during metastasis. An in-depth understanding of role of miRNAs in the metastatic cascade may lead to the identification of novel targets for anti-metastatic therapeutics as well as potential candidate miRNAs for cancer treatment. This review primarily focuses on the role of miRNAs in the mechanisms of cancer metastasis as well as implications for metastatic cancer treatment.

Correlations Between Hector Battifora Mesothelial-1 (HBME-1) Expression and Clinical Pathological Characteristics and Prognosis of Osteosarcoma Patients

Background

The aim of this study was to investigate the correlation between Hector Battifora mesothelial-1 (HBME-1) expression and the clinical pathological characteristics and prognosis of osteosarcoma (OS).

Material/Methods

HBME-1 expression was assessed using immunohistochemistry in OS tissues (n=152), osteochondroma tissues (n=91), and normal bone tissues (n=74). We carried out a follow-up lasting 8–60 months to investigate HBME-1 expression and its correlations with the clinical pathological characteristics and prognosis of OS.

Results

HBME-1 was highly expressed in OS tissues compared with osteochondroma tissues and normal bone tissues, and was highly expressed in osteochondroma tissues compared with normal bone tissues (all P<0.05). HBME-1 expression was correlated with clinical stages, postoperative recurrence, metastasis, and 5-year survival (all P<0.05). The area under the receiver operating characteristics curve of HBME-1 expression was 0.864, with sensitivity of 80.92%, specificity of 91.89%, and accuracy of 84.51%. The survival rate was lower in the HBME-1 positive expression group than the HBME-1 negative expression group (P<0.05). Clinical stages, metastasis, and HBME-1 expression were independent risk factors for the survival of patients with OS (all P<0.05).

Conclusions

HBME-1 expression was correlated with the occurrence and development of OS. HBME-1 positive expression was a risk factor for the prognosis of OS.