Extracellular vesicles released by hypoxia-induced tumor-associated fibroblasts impart chemoresistance to breast cancer cells via long noncoding RNA H19 delivery.

Recently, extracellular vesicles (EVs) have been emphasized in regulating the hypoxic tumor microenvironment of breast cancer (BC), where tumor-associated fibroblasts (TAFs) play a significant role. In this study, we describe possible molecular mechanisms behind the pro-tumoral effects of EVs, secreted by hypoxia (HP)-induced TAFs, on BC cell growth, metastasis, and chemoresistance. These mechanisms are based on long noncoding RNA H19 (H19) identified by microarray analysis. We employed an in silico approach to identify differentially expressed lncRNAs that were associated with BC. Subsequently, we explored possible downstream regulatory mechanisms. We isolated EVs from TAFs that were exposed to HP, and these EVs were denoted as HP-TAF-EVs henceforth. MTT, transwell, flow cytometry, and TUNEL assays were performed to assess the malignant phenotypes of BC cells. A paclitaxel (TAX)-resistant BC cell line was constructed, and xenograft tumor and lung metastasis models were established in nude mice for in vivo verification. Our observation revealed that lncRNA H19 was significantly overexpressed, whereas miR-497 was notably downregulated in BC. HP induced activation of TAFs and stimulated the secretion of EVs. Coculture of HP-TAF-EVs and BC cells led to an increase in TAX resistance of the latter. HP-TAF-EVs upregulated methylation of miR-497 by delivering lncRNA H19, which recruited DNMT1, thus lowering the expression of miR-497. In addition, lncRNA H19-containing HP-TAF-EVs hindered miR-497 expression, enhancing tumorigenesis and TAX resistance of BC cells in vivo. Our study presents evidence for the contribution of lncRNA H19-containing HP-TAF-EVs in the reduction of miR-497 expression through the recruitment of DNMT1, which in turn promotes the growth, metastasis, and chemoresistance of BC cells.

Long non-coding RNA FGD5 antisense RNA 1 targets Baculovirus inhibitor 5 via microRNA-497-5p to alleviate calcific aortic valve disease.

Calcific aortic valve disease (CAVD) is featured by thickening and calcification of the aortic valve. Osteoblast differentiation is a crucial step in valve calcification. Long non-coding RNAs (LncRNAs) participate in the osteogenic differentiation of mesenchymal cells. However, the character of lncRNA FGD5 antisense RNA 1 (FGD5-AS1) in CAVD is uncertain. After collection of human aortic valve tissue samples, detection of FGD5-AS1, microRNA (miR)-497-5p and Baculovirus inhibitor 5 (BIRC5) was conducted. Valve mesenchymal cells were isolated from CAVD patients and induced to differentiate to osteoblasts, and transfected with FGD5-AS1, miR-497-5p and BIRC5 plasmids. Detection of the alkaline phosphatase activity was after osteogenic induction of human aortic valve interstitial cells (hAVICs); Detection of the degree of calcium nodules and osteoblast differentiation markers (RUNX2 and OPN) was conducted. After establishment of a mouse model of CAVD, detection of the thickness of aortic valve leaflets, and the degree of calcification of the valve leaflets, and evaluation of echocardiographic parameters were implemented. Experimental data manifested in CAVD patients, lncRNAFGD5-AS1 and BIRC5 were reduced, but miR-497-5p was elevated; Enhancing lncRNA FGD5-AS1 or repressing miR-497-5p mitigated CAVD by restraining osteogenic differentiation; LncRNA FGD5-AS1 sponged miR-497-5p to target BIRC5; Repressive BIRC5 turned around the therapeutic action of elevated FGD5-AS1 or depressed miR-497-5p on hAVICs; Enhancive FGD5-AS1 in vivo was available to reduce ApoE-/- mouse CAVD induced via high cholesterol diet. All in all, lncRNAFGD5-AS1 targets BIRC5 via miR-497-5p to alleviate CAVD.

[Retracted] MicroRNA­497 inhibits cellular proliferation, migration and invasion of papillary thyroid cancer by directly targeting AKT3.

Following the publication of this paper, it was drawn to the Editors' attention by a concerned reader that certain of the data shown for the cell migration and invasion assays in Figs. 2C and 5C were strikingly similar to data appearing in different form in other articles by different authors. Owing to the fact that the contentious data in the above article had already been published elsewhere, or were already under consideration for publication, prior to its submission to Molecular Medicine Reports, the Editor has decided that this paper should be retracted from the Journal. The authors were asked for an explanation to account for these concerns, but the Editorial Office did not receive a satisfactory reply. The Editor apologizes to the readership for any inconvenience caused. [Molecular Medicine Reports 16: 5815­5822, 2017; DOI: 10.3892/mmr.2017.7345].

microRNA-497-mediated Smurf2/YY1/HIF2α axis in tumor growth and metastasis of esophageal squamous cell carcinoma.

Aberrant expression of microRNA-497 (miR-497) is associated with tumor progression, but the molecular mechanisms in tumorigenesis remain largely unknown. Here, we report that miR-497 expression is downregulated in esophageal squamous cell carcinoma (ESCC) clinical samples. Consistently, upregulation of miR-497 inhibits ESCC cell malignant properties and tumor growth in vivo. Importantly, we uncovered that miR-497 upregulation suppressed ESCC cell growth and tumor growth by inhibiting Smurf2. Mechanistically, we showed that Smurf2 was a target of miR-497, and mediated YY1 expression to elevate HIF2α expression, thereby enhancing the malignancy of ESCC cells. Together, our study uncovered the role of the miR-497-mediated Smurf2/YY1/HIF2α axis in tumor growth and metastasis, which might provide potential therapeutic targets for human ESCC.

microRNA-497 prevents pancreatic cancer stem cell gemcitabine resistance, migration, and invasion by directly targeting nuclear factor kappa B 1.

OBJECTIVES: Cancer stem cells (CSCs) comprise a small population of cells in cancerous tumors and play a critical role in tumor resistance to chemotherapy. miRNAs have been reported to enhance the sensitivity of pancreatic cancer to chemotherapy. However, the underlying molecular mechanism requires better understanding. METHODS: Cell viability and proliferation were examined with CCK8 assays. Quantitative real-time polymerase chain reaction was executed to assess mRNA expression. StarBase database was used to select the target genes of miRNA, which were further affirmed by dual luciferase assay. Transwell assay was used to analyze cell invasion and migration. RESULTS: We proved that miR-497 could be obviously downregulated in pancreatic cancer tissues and CSCs from Aspc-1 and Bxpc-3 cells. In addition, inhibition of miR-497 evidently accelerated pancreatic CSC gemcitabine resistance, migration and invasion. Moreover, we revealed that nuclear factor kappa B 1 (NFκB1) was prominently upregulated in pancreatic cancer tissues and pancreatic CSCs, and NFκB1 was also identified as a direct target of miR-497. Furthermore, we demonstrated that overexpression of NFκB1 could also notably promote the viability, migration, and invasion of gemcitabine-treated pancreatic CSCs, but this effect could be partially abolished by miR-497 overexpression. CONCLUSIONS: Those findings suggest that miR-497 overexpression could suppress gemcitabine resistance and the metastasis of pancreatic CSCs and non-CSCs by directly targeting NFκB1.

Longitude Variation of the microRNA-497/FGF-23 Axis during Treatment and Its Linkage with Neoadjuvant/Adjuvant Trastuzumab-Induced Cardiotoxicity in HER2-Positive Breast Cancer Patients.

Purpose: MicroRNA-497 (miR-497) is previously reported to target fibroblast growth factor 23 (FGF-23) and regulates cardiac injury, while their value in predicting drug-induced cardiotoxicity is not reported. Thus, the current study aimed to investigate the correlation of miR-497/FGF-23 with neoadjuvant/adjuvant trastuzumab-induced cardiotoxicity in human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients. Methods: A total of 97 HER2-positive surgical breast cancer patients who received neoadjuvant/adjuvant trastuzumab contained regimens were enrolled; then, their peripheral blood mononuclear cells (PBMC) and serum were collected at baseline, after neoadjuvant treatment, at 3 months (M3), 6 months (M6), 9 months (M9), and 12 months (M12) after surgery. The PBMC was used for miR-497 measurements, and the serum was used for FGF-23 measurements. The cardiotoxicity events and incidence were recorded. Results: A total of 24 (24.7%) patients occurred cardiotoxicity during the treatment period. MiR-497 decreased from baseline (median: 0.955) to M12 after surgery (median: 0.602) (p < 0.001), while FGF-23 increased from baseline (median: 0.390 ng/mL) to M12 after surgery (median: 0.566 ng/mL) (p < 0.001); besides, the miR-497/FGF-23 axis greatly reduced from baseline (median: 2.545) to M12 after surgery (median: 1.222) (p < 0.001). At most time points, miR-497 was negatively related to FGF-23 (all p < 0.05). Notably, the miR-497/FGF-23 axis at all time points (including baseline, postneoadjuvant treatment, M3, M6, M9, and M12) was related to a lower risk of cardiotoxicity (all p < 0.05). Furthermore, the miR-497/FGF-23 axis was also positively correlated with the left ventricular ejection fraction (LVEF) at all time points (all p < 0.01). Conclusion: The MiR-497/FGF-23 axis serves as a potential indicator predicting trastuzumab-induced cardiotoxicity in HER2-positive breast cancer patients.

DNA methyltransferase 1 inhibits microRNA-497 and elevates GPRC5A expression to promote chemotherapy resistance and metastasis in breast cancer.

BACKGROUND: Abnormal DNA methylation of tumor suppressor gene promoter has been found in breast cancer. Therefore, the current study set out to explore how DNA methyltransferase 1 (DNMT1) affects breast cancer through mediating miR-497/GPRC5A axis. METHODS: After loss and gain-of-function approaches were conducted in MCF-7/ADR and MCF-7 cells, cell viability, IC50 value, invasion, migration and apoptosis were measured, respectively. In addition, drug resistance, metastasis and apoptosis-related protein expression were examined using immunoblotting. ChIP and dual-luciferase reporter gene assays were carried out to validate relationship among DNMT1, miR-497, and GPRC5RA. Subcutaneous xenograft tumor model in nude mice was established to detect effects of DNMT1 on growth and metastasis of breast cancer in vivo. RESULTS: It was found that DNMT1 was notably increased, while miR-497 was poorly-expressed in breast cancer. Highly-expressed DNMT1 could promote chemotherapy resistance and metastasis of breast cancer. Meanwhile, DNMT1 modified methylation of CpG island in miR-497 promoter region, thereby repressing miR-497 level. In addition, miR-497 targeted GPRC5A expression to curb chemotherapy resistance and metastasis of breast cancer cells. Lastly, in vivo experiments showed that knockdown of DNMT1 could suppress breast cancer growth and metastasis. CONCLUSIONS: Collectively, our findings indicated that DNMT1 may inhibit miR-497 and boost the expression of GPRC5A through methylation, thus augmenting breast cancer chemotherapy resistance and metastasis, which provides novel mechanistic insight into the unrecognized roles of DNMT1 in breast cancer.

Knockdown of long non­coding RNA DDX11­AS1 inhibits the proliferation, migration and paclitaxel resistance of breast cancer cells by upregulating microRNA­497 expression.

Drug resistance is a major problem to overcome in the treatment of cancer; therefore, identifying therapeutic targets for drug resistance is a point of focus in the field of cancer research. Long non­coding RNAs (lncRNAs) and microRNAs (miRs) not only affect gene expression regulation during cell proliferation, but also have several potential roles in the drug resistance of malignant tumors. Reverse transcription­quantitative PCR was used to detect the expression levels of DDX11 antisense RNA 1 (DDX11­AS1) and miR­497 in MCF­7 and MDA­MB­231 cells. Cell transfection techniques were used to interfere with the expression levels of DDX11­AS1 and miR­497. Cell Counting Kit­8 and MTT assays were used to detect cell viability. A colony formation assay was used to detect cell proliferation. Wound­healing and Transwell assays were performed to measure the levels of cell migration and invasion. Western blotting was used to analyze the expression levels of migration­associated proteins, and immunofluorescence and western blotting were used to determine the expression levels of the epithelial­mesenchymal transition­related proteins E­cadherin and N­cadherin, respectively. A luciferase reporter gene assay was used to verify the targeted binding of DDX11­AS1 and miR­497. The present study demonstrated that the expression levels of lncRNA DDX11­AS1 were markedly increased in paclitaxel (PTX)­resistant breast cancer cell lines. By contrast, knockdown of DDX11­AS1 expression inhibited PTX resistance of breast cancer cells, and suppressed the proliferation, invasion and migration of breast cancer cells, which was achieved via upregulation of miR­497 expression. In conclusion, knockdown of lncRNA DDX11­AS1 could inhibit the proliferation, migration and PTX resistance of breast cancer cells by upregulating miR­497 expression.

Circular RNA VMA21 ameliorates lung injury in septic rat via targeting microRNA-497-5p/CD2-associated protein axis.

Sepsis was characterized via an acute inflammatory response to infection, often accompanying by multiple organ failure, particularly lung damage. Circular RNA (circRNA) played an important role in the pathology of a variety of diseases. However, the role of circRNA in sepsis-induced lung injury (LI) remained unknown. This study was to explore the expression and role of circVMA21 in sepsis LI and the possible molecular mechanism. The results manifested circVMA21 and CD2-associated protein (CD2AP) were down-regulated in lung tissue and lipopolysaccharide (LPS)-treated BEAS-2B, while microRNA (miR)-497-5p was up-regulated. A large number of deaths in rats after surgery of 72 h were caused via cecal ligation-perforation surgery, W/D value and Bax positive cells were increased, LI was caused, cell apoptosis, tumor necrosis factor-α, Interleukin (IL)-1ß and IL-6 expression were promoted and Bcl-2 positive cells were decreased. Overexpression of circVMA21 ameliorated these phenomena. In addition, LPS-induced apoptosis and inflammation of BEAS-2B cells was improved via overexpression of circVMA21, while overexpression of miR-497-5P was opposite. Apoptosis, inflammation, and oxidative damage of BEAS-2B cells were aggravated via knockdown of circVMA21, but it was reversed by knockdown of miR-497-5p or overexpression of CD2AP. Mechanistically, CircVMA21 mediated CD2AP expression through competitive adsorption of miR-497-5p. In conclusion, this work showed circVMA21 improved LI in sepsis rats by targeting miR-497-5p/CD2AP axis, suggesting that circVMA21 may be a novel therapeutic target for sepsis-induced LI.

[Retracted] Long intergenic non­protein coding RNA 152 promotes multiple myeloma progression by negatively regulating microRNA­497.

Following the publication of this paper, an interested reader drew the authors' attention to the fact that several of the tumour images shown in Fig. 6B were strikingly similar to images that had appeared in another paper by different authors published at around the same time. The authors also admitted that the in vivo experiments reported in this study had been performed by a third party. Consequently, owing to a lack of confidence in the presented data, the authors requested that this paper be retracted from the Journal. The Editor was in agreement that the paper should be retracted. All authors agree with the retraction of this article, and the Editor apologizes to the readership for any inconvenience caused. [the original article was published in Oncology Reports 40: 3763­3771, 2018; DOI: 10.3892/or.2018.6721].

Expression and Diagnostic Value of miR-497 and miR-1246 in Hepatocellular Carcinoma.

OBJECTIVE: Serum microRNAs (miRNAs) may serve as biomarkers in various cancers. Our study aims to explore the roles of miR-497 and miR-1246 in hepatocellular carcinoma (HCC). METHODS: The expression levels of miR-497 and miR-1246 were measured by RT-PCR. A correlation analysis was conducted between the expression levels of miR-497 and miR-1246 and clinicopathological characteristics of patients. The receiver operating characteristic (ROC) curve was applied to evaluate the diagnostic efficacy in HCC. In addition, bioinformatics tools were also utilized to predict the potential targets of miR-497 and miR-1246. RESULTS: The expression level of miR-497 in HCC was significantly down-regulated compared with the control group while the miR-1246 revealed a significantly higher expression level in HCC. There was a significant correlation demonstrated between the expression levels of miR-497 and miR-1246 in preoperative serum of HCC and the differentiation degree, Tumor Node Metastasis (TNM) classification, and metastasis. The expression levels of serum miR-497 and miR-1246 were significantly associated with the diagnosis, prognosis, and overall survival rate of patients with HCC. Moreover, the potential target genes of miR-497 in HCC include ARL2, UBE2Q1, PHF19, APLN, CHEK1, CASK, SUCO, CCNE1, and KIF23. The low expression of these nine genes is associated with a better prognosis of HCC patients. AUTS2 is a novel target gene of miR-1246, and its low expression is significantly related to the low overall survival rate of HCC patients. CONCLUSIONS: miR-497 and miR-1246 are possibly involved in the progression of HCC by regulating target genes, respectively, and could serve as biomarkers in HCC.

The Role of Serum miR-497 on the Predictive Index of Early Diagnosis and Poor Prognosis of Atherosclerosis Cerebral Infarction.

BACKGROUND: Serum miR-497 can be used as a predictive index of the early diagnosis and poor prognosis of atherosclerosis cerebral infarction (ATCI). METHODS: Overall, 135 ATCI patients, treated in The Second Affiliated Hospital of Nantong University, Nantong 226001, P.R.China from Apr 2012 to Jan 2015, were included in ATCI group. Whereas, 77 patients with non-atherosclerosis cerebral infarction were put in the control group. RT-qPCR was performed for detecting serum miR-497 expression, whose relationship with the patients' clinicopathological parameters was analyzed. Receiver operating characteristic (ROC) curves were plotted to evaluate values of serum miR-497 for diagnosing ATCI patients and their 3-year and 5-year overall survival rates (OSRs). Cox regression analysis was conducted on prognostic factors of ATCI patients. RESULTS: miR-497 remarkably rose in the serum of ATCI patients, and was correlated with histories of hypertension, smoking and diabetes mellitus (DM). Its areas under curves (AUCs) for diagnosing these pathological parameters were 0.803, 0.817 and 0.819, respectively. Its expression was higher in the serum of the patients with recurrence and poor prognoses. Its AUCs for predicting the two conditions were 0.924 and 0.937, respectively. The 3- and 5-year OSRs of patients with low expression were remarkably higher than those of patients with high expression. CONCLUSION: miR-497 and histories of hypertension, smoking and DM were independent prognostic factors affecting the 3-year OSR of ATCI patients. miR-497 expression rises in ATCI patients, so this miR is expected to become a serum diagnostic marker for ATCI.

miR-497 inhibits proliferation and invasion in triple-negative breast cancer cells via YAP1.

MicroRNA (miR)-497 has been reported as a tumor suppressor in various cancer types. Nonetheless, the regulation of triple-negative breast cancer (TNBC) by miR-497 remains poorly understood. The present study aimed to investigate the potential function and mechanism of miR-497 in TNBC. A total of 36 TNBC and matched non-cancerous tissue samples were collected for analysis. Reverse transcription-quantitative PCR was performed to detect the miR-497 levels in TNBC tissue. The association between miR-497 expression, clinical characteristics and survival was then analyzed. To investigate the role of miR-497 in TNBC, MTT, colony formation, Transwell invasion, cell cycle and cell apoptosis assays were conducted following transfection of miR-497 mimics into the MDA-MB-231 and MDA-MB-468 cell lines. Luciferase reporter assays and western blot analysis were used to confirm the regulation of a putative target of miR-497. The results indicated that the expression of miR-497 was downregulated in the TNBC specimens. Further analysis demonstrated that the expression of miR-497 was downregulated in patients with advanced TNBC stages and that low miR-497 was associated with poor prognosis in patients with TNBC. Transfection of miR-497 mimics inhibited TNBC cell proliferation and increased cell apoptosis in MDA-MB-231 and MDA-MB-468 cells. Moreover, cell migration was inhibited following overexpression of miR-497, which also led to the arrest of the breast cancer cells in the G0/G1 phase of the cell cycle. Yes-associated protein 1 (YAP1), a critical molecule in the Hippo pathway, was identified as a target of miR-497. Notably, the protein and mRNA expression levels of YAP1 in MDA-MB-231 and MDA-MB-468 cells were downregulated following overexpression of miR-497. Overall, the findings of the present study indicated that miR-497 inhibited TNBC cell proliferation and migration and induced cell apoptosis by negatively regulating YAP1 expression. Thus, targeting miR-497 may represent a potential strategy for the treatment of TNBC.

Bone marrow mesenchymal stem cell-derived extracellular vesicles containing miR-497-5p inhibit RSPO2 and accelerate OPLL.

AIMS: Muscle and adipose tissue-derived mesenchymal stem cells presented high osteogenic potentials, which modulate osteoblast function through releasing extracellular vesicles (EVs) containing miRNAs. Herein, this study evaluated the function of bone marrow mesenchymal stem cell-derived extracellular vesicles (BMSC-EVs) delivering miR-497-5p in ossification of the posterior longitudinal ligament (OPLL). MAIN METHODS: The expression level of miR-497-5p was validated in ossified posterior longitudinal ligament (PLL) tissues and BMSC-EVs. The uptake of BMSC-EVs by ligament fibroblasts was observed by immunofluorescence. miR-497-5p was overexpressed or downregulated to assess its role in osteogenic differentiation of ligament fibroblasts. Further, an OPLL rat model was established to substantiate the effect of BMSC-EVs enriched with miR-497-5p on OPLL. KEY FINDINGS: Ossified PLL tissues presented with high miR-497-5p expression. PLL fibroblasts were identified to endocytose BMSC-EVs. BMSC-EVs could upregulate miR-497-5p and shuttle it to ligament fibroblasts to accelerate the osteogenic differentiation. miR-497-5p targeted and inversely regulated RSPO2. Then, RSPO2 overexpression activated Wnt/ß-catenin pathway and repressed the osteogenic differentiation of ligament fibroblasts. In vivo experiments further showed that miR-497-5p-containing BMSC-EVs enhanced OPLL through diminishing RSPO2 and inactivating Wnt/ß-catenin pathway. SIGNIFICANCE: BMSC-EVs could deliver miR-497-5p to ligament fibroblasts and modulate RSPO2-mediated Wnt/ß-catenin pathway, thereby accelerating OPLL.

Downregulation of miR-497-5p prevents liver ischemia-reperfusion injury in association with MED1/TIMP-2 axis and the NF-κB pathway.

Liver ischemia-reperfusion (I/R) injury is a common clinical pathological phenomenon, which is accompanied by the occurrence in liver transplantation. However, the underlying mechanism is not yet fully understood. MicroRNAs (miRNAs) play an important role in liver I/R injury. Therefore, the study of miRNAs function will contribute a new biological marker diagnosis of liver I/R injury. This study aims to evaluate effects of miR-497-5p in liver I/R injury in mice. The related regulatory factors of miR-497-5p in liver I/R injury were predicted by bioinformatics analysis. Vascular occlusion was performed to establish the liver I/R injury animal models. Hypoxia/reoxygenation (H/R) was performed to establish the in vitro models. Hematoxylin-eosin (HE) staining was conducted to assess liver injury. The inflammatory factors were evaluated by enzyme-linked immunosorbent assay (ELISA). Flow cytometry was adopted to assess the cell apoptosis. The expression of miR-497b-5p was increased in liver I/R injury. Knockdown of miR-497b-5p inhibited the production of inflammatory factors and cell apoptosis. Overexpression of mediator complex subunit 1 (MED1) and tissue inhibitor of metalloproteinase 2 (TIMP2) inhibited cell apoptosis to alleviate liver I/R injury. miR-497b-5p could activate the nuclear factor kappa-B (NF-κB) pathway by inhibiting the MED1/TIMP-2 axis to promote liver I/R injury. This study may provide a new strategy for the treatment of liver I/R injury.

LncRNA POT1-AS1 accelerates the progression of gastric cancer by serving as a competing endogenous RNA of microRNA-497-5p to increase PDK3 expression.

BACKGROUND: Gastric cancer (GC) is the most common malignant tumor of the digestive system. Although progress has been reported in terms of treatment, it is still the second leading cause of cancer-related death. Long non-coding RNAs have been shown to play a key role in human cancers in recent investigations. However, the role of POT1-AS1 in GC is still unclear. METHODS: The relative POT1-AS1 level in GC tissues and paracancerous tissues was detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The biological function of POT1-AS1 was studied by CCK8 and Transwell assays in vitro experiments. Moreover, the downstream target genes of POT1-AS1 were predicted by bioinformatics. RESULTS: In this study, high POT1-AS1 expression in GC cells was confirmed, and its elevated expression was linked to patients' negative clinicopathological characteristics, as well as shorter disease-free survival (DFS) and overall survival (OS). POT1-AS1 was shown to serve as a competing endogenous RNA (ceRNA) by sponging miR-497-5p to increase PDK3 expression. The impact of POT1-AS1 silencing on GC malignant phenotypes could be reversed by suppressing miR-497-5p or restoring PDK3, according to rescue experiments. CONCLUSIONS: In brief, POT1-AS1 acted as an oncogenic lncRNA in GC, facilitating GC development by affecting the miR-497-5p/PDK3 axis, implying that the POT1-AS1/miR-497-5p/PDK3 axis is a useful target in anticancer therapy.

Regulation of microRNA-497 expression in human cancer.

MicroRNAs (miRNAs/miRs) are a type of non-coding single-stranded RNA, with a length of ~22 nt, which are encoded by endogenous genes and are involved in the post-transcriptional regulation of gene expression in animals and plants. Studies have demonstrated that miRNAs play an important role in the occurrence, development, metastasis, diagnosis and treatment of cancer. In recent years, miR-497 has been identified as one of the key miRNAs in a variety of cancer types and has been shown to be downregulated in a variety of solid tumors. However, the regulation of miR-497 expression involves a complex network, which is affected by several factors. The aim of the present review was to summarize the mechanism of regulation of miR-497 expression at the pre-transcriptional and transcriptional levels in cancer, as well as the role of miR-497 expression imbalance in cancer diagnosis, treatment and prognosis. The regulatory mechanisms of miR-497 expression may aid in our understanding of the causes of miR-497 expression imbalance and provide a reference value for further research on the diagnosis and treatment of cancer.

Methylation-Mediated Silencing of MicroRNA-497 Promotes Breast Cancer Progression Through Up-Regulation of Mucin1.

BACKGROUND: Potential anti-tumor effects of microRNA-497 (miR-497) have been highlighted in various malignancies including breast cancer. However, little is known about the function of miR-497 and its putative target mucin1 (MUC1) in breast cancer. The present study explored how miR-497 regulates breast cancer progression in a MUC1-dependent manner. METHODS: Expression of miR-497 and MUC1 was determined in breast cancer tissues and cells. Methylation specific polymerase chain reaction was used to measure the methylation status of CpG islands of miR-497 promoter, while chromatin immunoprecipitation assay was used to detect recruitment of methyltransferase to the promoter region of miR-497. Alteration in expression of miR-497 (overexpression) and MUC1 (up- and down-regulation) was performed to examine their roles in breast cancer biology in vitro and in vivo. The binding affinity between miR-497 and MUC1 was investigated through a bioinformatics database and dual luciferase reporter gene assay. RESULTS: MiR-497 was down-regulated and MUC1 was up-regulated in breast cancer tissues and cell lines. Besides, methylation induced a down-regulation of miR-497 in breast cancer. The bioinformatics analysis and dual luciferase reporter gene assay indicated that miR-497 targeted MUC1. Overexpression of miR-497 inhibited breast cancer cell proliferation and invasion and promoted the apoptosis of breast cancer cells by down-regulating MUC1. The inhibitory action of miR-497 on tumor growth was validated in vivo. CONCLUSION: In conclusion, miR-497 down-regulated MUC1 expression and subsequently suppressed breast cancer progression, highlighting miR-497 to be a potential biomarker and therapeutic target for breast cancer therapy.

MicroRNA-497-5p stimulates osteoblast differentiation through HMGA2-mediated JNK signaling pathway.

BACKGROUND: Osteoporosis (OP) has the characteristics of the decline in bone mineral density and worsening of bone quality, contributing to a higher risk of fractures. Some microRNAs (miRNAs) have been validated as possible mediators of osteoblast differentiation. We herein aimed to clarify whether miR-497-5p regulates the differentiation of osteoblasts in MC3T3-E1 cells. METHODS: The expression of miR-497-5p in OP patients and controls was measured by RT-qPCR, and its expression changes during osteoblast differentiation were determined as well. The effects of miR-497-5p on the differentiation of MC3T3-E1 cells were studied using MTT, ALR staining, and ARS staining. The target gene of miR-497-5p was predicted by TargetScan, and the effects of its target gene on differentiation and the pathway involved were investigated. RESULTS: miR-497-5p expressed poorly in OP patients, and its expression was upregulated during MC3T3-E1 cell differentiation. Overexpression of miR-497-5p promoted mineralized nodule formation and the expression of RUNX2 and OCN. miR-497-5p targeted high mobility group AT-Hook 2 (HMGA2), while the upregulation of HMGA2 inhibited osteogenesis induced by miR-497-5p mimic. miR-497-5p significantly impaired the c-Jun NH2-terminal kinase (JNK) pathway, whereas HMGA2 activated this pathway. Activation of the JNK pathway inhibited the stimulative role of miR-497-5p mimic in osteogenesis. CONCLUSIONS: miR-497-5p inhibits the development of OP by promoting osteogenesis via targeting HMGA2.

NF-κB maintains the stemness of colon cancer cells by downregulating miR-195-5p/497-5p and upregulating MCM2.

BACKGROUND: Colon cancer represents one of the leading causes of gastrointestinal tumors in industrialized countries, and its incidence appears to be increasing at an alarming rate. Accumulating evidence has unveiled the contributory roles of cancer stem cells (CSCs) in tumorigenicity, recurrence, and metastases. The functions of NF-kappa B (NF-κB) activation on cancer cell survival, including colon cancer cells have encouraged us to study the role of NF-κB in the maintenance of CSCs in colon cancer. METHODS: Tumor samples and matched normal samples were obtained from 35 colon cancer cases. CSCs were isolated from human colon cancer cell lines, where the stemness of the cells was evaluated by cell viability, colony-forming, spheroid-forming, invasion, migration, and apoptosis assays. NF-κB activation was then performed in subcutaneous tumor models of CSCs by injecting lipopolysaccharides (LPS) i.p. RESULTS: We found that NF-κB activation could reduce the expression of miR-195-5p and miR-497-5p, where these two miRNAs were determined to be downregulated in colon cancer tissues, cultured colon CSCs, and LPS-injected subcutaneous tumor models. Elevation of miR-195-5p and miR-497-5p levels by their specific mimic could ablate the effects of NF-κB on the stemness of colon cancer cells in vivo and in vitro, suggesting that NF-κB could maintain the stemness of colon cancer cells by downregulating miR-195-5p/497-5p. MCM2 was validated as the target gene of miR-195-5p and miR-497-5p in cultured colon CSCs. Overexpression of MCM2 was shown to restore the stemness of colon cancer cells in the presence of miR-195-5p and miR-497-5p, suggesting that miR-195-5p and miR-497-5p could impair the stemness of colon cancer cells by targeting MCM2 in vivo and in vitro. CONCLUSIONS: Our work demonstrates that the restoration of miR-195-5p and miR-497-5p may be a therapeutic strategy for colon cancer treatment in relation to NF-κB activation.