MicroRNA-9 and breast cancer

Breast cancer is the most common cancer in women worldwide and seriously impairs patients' physical and mental health. Its incidence has been predicted to rise further. Mounting evidence indicates that microRNAs (miRNAs) play key roles in tumorigenesis and development. It is worth noting that miR-9 exerts critical functions in the initiation and progression of breast cancer, and the present research displays opposite roles of miR-9 in breast cancer. This article mainly reviews the roles of miR-9 in breast cancer progression.

miR-9 inhibition of neuronal apoptosis and expression levels of apoptosis genes Bcl-2 and Bax in depression model rats through Notch pathway

Effects of micro ribonucleic acid (miR)-9 on neuronal apoptosis and expression levels of apoptosis genes B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) in depression model rats, as well as its regulatory mechanism, were investigated. Thirty Sprague-Dawley rats were randomly divided into control group (n=10), model group (n=10) and miR-9 inhibitor group (n=10). The rat model of depression was established using the chronic stress method. The learning and memory abilities of rats were detected via water maze test, the neuronal morphology of the brain was detected using hematoxylin and eosin (H&E) staining, and the levels of serum Bcl-2 and Bax were determined using the enzyme-linked immunosorbent assay (ELISA) kits. Moreover, the neuronal apoptosis in the brain was determined through terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, and the protein levels of Notch1 and Hes1 in brain tissues were measured via western blot analysis. Compared with the control group, the rats in the model group presented significantly decreased learning and memory abilities, poor neuronal morphology of the brain, significantly higher neuronal apoptosis rate in the brain, decreased level of serum Bcl-2, increased level of serum Bax, and significantly decreased protein levels of Notch1 and Hes1 in brain tissues. Compared with the model group, the rats in miR-9 inhibitor group showed obviously improved learning and memory abilities, improved neuronal morphology of the brain, an obviously lower neuronal apoptosis rate in the brain, increased level of serum Bcl-2, decreased level of serum Bax, and obviously increased protein levels of Notch1 and Hes1 in brain tissues. In conclusion, miR-9 inhibitor can promote the neurological function recovery and inhibit the neuronal apoptosis of depression model rats through activating the Notch signaling pathway, suggesting that miR-9 can be an important therapeutic target for depression.

LncRNA KCNQ1OT1 contributes to oxygen-glucose-deprivation/reoxygenation-induced injury via sponging miR-9 in cultured neurons to regulate MMP8

Our study proposed to investigate the function of potassium voltage-gated channel sub-family Q member 1 opposite strand 1 (KCNQ1OT1) in cerebral ischemia-reperfusion (I/R) injury and the underlying mechanism. We constructed an oxygen-glucose-deprivation/reoxygenation (OGD/R) model using the primary cortical neurons to mimic the cerebral I/R injury in vitro. Small inference RNA (siRNA) was used to silencing KCNQ1OT1. Dual luciferase assay was conducted to verify the interaction between KCNQ1OT1 and miR-9 and interaction between miR-9 and MMP8. CCK8 assay and flow cytometry analysis were applied for determing the viability and apoptosis of neurons, accordingly. QPCR and Western blot were performed to determine the RNA and protein expression. Our outcomes revealed that the expression of KCNQ1OT1 in cultured neurons was notably enhanced after suffered to OGD/R. Knockdown of KCNQ1OT1 weakened OGD/R-induced injury in neurons. Moreover, depletion of KCNQ1OT1 lead to the up-regulation of miR-9 and down-regulation of MMP8. Dual luciferase target validation assays demonstrated that KCNQ1OT1 directly interact with miR-9 and MMP8 is a direct target of miR-9, suggesting that KCNQ1OT1/miR-9/MMP8 might constitute the competing endogenous RNA (ceRNA) mechanism. Knockdown of MMP8 or up-regulation of miR-9 also could weaken OGD/R-induced injury. Furthermore, cells co-transfected with si-KCNQ1OT1, miR-9 mimic and si-MMP8 could significantly abolish the injury on neurons caused by OGD/R. Taken together, our data manifested that KCNQ1OT1 possibly acts as a facilitator in cerebral I/R injury through modulating miR-9/MMP8 axis as a ceRNA.

Evaluation of microRNA-9 and -192 expression levels as biomarkers in patients suffering from breast cancer

Given the global outbreak of breast cancer and its debilitating effect on women's health, it is not surprising that tremendous efforts have been made with an aim of shedding more light on the mechanisms involved in the pathogenesis of this type of cancer. Among the long list of risk factors associated with this malignancy, recently, the role of microRNAs (miRNAs or miRs) has turned into a hotspot for breast cancer investigations. miRNAs approximately 20 nucleotides in length and are located in either an exon or an intron, playing a role in the regulation of gene expression. In the present study, we extracted RNA from both the serum and cancerous tissue of breast cancer patients and after synthesizing the cDNA, we performed quantitative PCR to determine the expression levels of miR-9 and miR-192. The resulting data revealed that while the mRNA expression level of miR-9 was significantly decreased in the breast cancer tissues, there was no noticeable change in the expression level of this miRNA in the serum samples. Likewise, we found that the marked downregulation of miR-192 was only restricted to the cancerous tissues, but was not found in the serum of patients. Based on the meaningful downregulation of the expression of miR-9 and miR-192, this study provides a plausible framework for these miRNAs as effective biomarkers for breast cancer patients.

CircPLEKHM3 acts as a tumor suppressor through regulation of the miR-9/BRCA1/DNAJB6/KLF4/AKT1 axis in ovarian cancer

BACKGROUND

Emerging evidence has shown that circular RNAs (circRNAs) play essential roles in cancer biology and are potential biomarkers and targets for cancer therapy. However, the expression and function of circRNAs in ovarian carcinogenesis and its progression remain elusive.

METHODS

RNA sequencing was performed to reveal circRNA expression profiles in ovarian cancerous and normal tissues. Single-molecule RNA in-situ hybridization was used to quantify circPLEKHM3 expression in tumor tissues. Cell-based in-vitro and in-vivo assays were subsequently conducted to support the clinical findings.

RESULTS

CircPLEKHM3 was identified as one of the most significantly down-regulated circRNAs in ovarian cancer tissues compared with normal tissues. Its expression was further decreased in peritoneal metastatic ovarian carcinomas compared to primary ovarian carcinomas. Patients with lower circPLEKHM3 tend to have a worse prognosis. Functionally, circPLEKHM3 overexpression inhibited cell growth, migration and epithelial-mesenchymal transition, whereas its knockdown exerted an opposite role. Further analyses showed that circPLEKHM3 sponged miR-9 to regulate the endogenous expression of BRCA1, DNAJB6 and KLF4, and consequently inactivate AKT1 signaling. In addition, AKT inhibitor MK-2206 could block the tumor-promoting effect of circPLEKHM3 depletion, and potentiate Taxol-induced growth inhibition of ovarian cancer cells.

CONCLUSIONS

Our findings demonstrated that circPLEKHM3 functions as a tumor suppressor in ovarian cancer cells by targeting the miR-9/BRCA1/DNAJB6/KLF4/AKT1 axis and may be used as a prognostic indicator and therapeutic target in ovarian cancer patients. The new strategy for treating ovarian cancer by a combination therapy of Taxol with MK-2206 is worth further investigation, especially in ovarian cancer patients with loss of circPLEKHM3 expression.

MicroRNA-9 exerts antitumor effects on hepatocellular carcinoma progression by targeting HMGA2

Accumulating evidence has demonstrated that the aberrant expression of microRNAs (miRs or miRNAs) may contribute to the initiation and progression of various types of human cancer and may also constitute biomarkers for cancer diagnosis and therapy. However, the specific function of miR‐9 in hepatocellular carcinoma (HCC) remains unclear, and the mechanisms that underlie HCC are incompletely understood. Here, we report that miR‐9 expression was significantly decreased in clinical tumor tissue samples, as well as in a cohort of HCC cell lines. In addition, it was demonstrated that overexpression of miR‐9 suppressed the proliferative and migratory capacity of HCC cells and impaired cell cycle progression. Furthermore, high mobility group AT‐hook 2 (HMGA2) was verified as a downstream target gene of miR‐9 using a luciferase reporter assay. Quantitative RT‐PCR and western blotting implicated HMGA2 in the miR‐9‐mediated reduction of HCC cell growth. In vivo, transfection with miR‐9 mimics down‐regulated the expression of HMGA2, thus leading to a dramatic reduction in tumor growth in a mouse xenograft model. These results suggest that miR‐9 may exert critical antitumor effects on HCC by directly targeting HMGA2, and the miR9/HMGA2 signaling pathway may be of use for the diagnosis and prognosis of patients with HCC.

miR-9 regulates melanocytes adhesion and migration during vitiligo repigmentation induced by UVB treatment

The decreased adhesion ability of melanocytes to the neighboring keratinocytes prompts melanocytes to lose from the epidermis, comprising the critical step in vitiligo pathogenesis. The repigmentation process involves the migration of melanocytes to the lesional area. This study aims to investigate the role and mechanism of microRNA (miR)-9 in the adhesion and migration of melanocytes during vitiligo repigmentation induced by UVB treatment. The HaCaT keratinocytes were used to mimic lesional condition and the PIG1 melanocytes as perilesional condition. Human lesional vitiligo specimens showed increased miR-9 and decreased adhesion molecules such as E-cadherin and β1 integrin. Furthermore, UVB exposure upregulated IL-10, E-cadherin, and β1 integrin, downregulated miR-9 in HaCaT cells. Moreover, the increased IL-10 by UVB exposure decreased miR-9 level by inducing miR-9 methylation via methyltransferase DNMT3A in HaCaT cells. Additionally, miR-9 targeted and inhibited E-cadherin and β1 integrin in HaCaT cells, and suppressed migration of PIG1 cells to UVB-exposed HaCaT cells. In conclusion, miR-9 was suppressed by IL-10 and inhibited migration of PIG1 cells to HaCaT cells during UVB-mediated vitiligo repigmentation.

miR-9: From function to therapeutic potential in cancer

Malignant neoplasms are regarded as the main cause of death around the world; hence, many research studies were conducted to further perceive molecular mechanisms, treatment, and cancer prognosis. Cancer is known as a major factor for health-related problems in the world. The main challenges associated with these diseases are prompt diagnosis, disease remission classification and treatment status forecast. Therefore, progressing in such areas by developing new and optimized methods with the help of minimally invasive biological markers such as circular microRNAs (miRNAs) can be considered important. miRNA interactions with target genes have specified their role in development, apoptosis, differentiation, and proliferation and also, confirm direct miRNA function in cancer. Different miRNAs expression levels in various types of malignant neoplasms have been observed to be associated with prognosis of various carcinomas. miR-9 seems to implement opposite practices in different tissues or under various cancer incidences by influencing different genes. Aberrant miR-9 levels have been observed in many cancer types. Therefore, we intended to investigate the precise role of miR-9 in patients with malignant neoplasms. To this end, in this study, we attempted to examine different studies to clarify the overall role of miR-9 as a prognostic marker in several human tumors. The presented data in this study can help us to find the novel therapeutic avenues for treatment of human cancers.

LncRNA SRA1 is down-regulated in HPV-negative cervical squamous cell carcinoma and regulates cancer cell behaviors

LncRNA SRA1 plays important roles in several types of human diseases. The present study aimed to explore the role of SRA1 in cervical squamous cell carcinoma (CSCC). In the present study, we showed that plasma SRA1 was down-regulated in human papillomavirus (HPV)-negative CSCC patients but not in HPV-positive CSCC patients compared with healthy females. Down-regulated SRA1 distinguished HPV-negative CSCC patients from HPV-positive CSCC patients and healthy females. In HPV-negative CSCC patients, miR-9 was up-regulated and inversely correlated with SRA1. In HPV-negative CSCC cells, SRA1 overexpression caused the down-regulated miR-9, while miR-9 overexpression failed to affect SRA1. Moreover, SRA1 overexpression caused decreased, while miR-9 overexpression caused increased proliferation, migration and invasion rates of cancer cells. In addition, miR-9 overexpression attenuated the effects of SRA1 overexpression. Therefore, SRA1 is down-regulated in HPV-negative CSCC and regulates cancer cell behaviors possibly by down-regulating miR-9.

MiR-9 promotes multiple myeloma progression by regulating TRIM56/NF-κB pathway

miR-9 has been reported to play a pivotal role in multiple human cancers by acting as an oncogene or tumor suppressor. In this study, we explored the possible role and molecular mechanism of miR-9 in multiple myeloma (MM). The miR-9 expression was examined by quantitative real-time polymerase chain reaction assay. Transfection with miR-9-mimics, miR-9-inhibitor, pcDNA-TRIM56, or si-TRIM56 into cells was used to change the expression levels of miR-9 and TRIM56. Western blot analysis was used to detect the expression of TRIM56, p65, p-p65, IκBα, and p-IκBα. The potential target of miR-9 was confirmed by luciferase reporter assay. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay, colony formation assay, and flow cytometry were used to assess the abilities of cell proliferation and apoptosis. miR-9 was upregulated in MM patients and cell lines, and miR-9 overexpression promoted proliferation and repressed apoptosis in MM cell lines. TRIM56 was confirmed as a target of miR-9. Moreover, TRIM56 reversed miR-9-mediated pro-proliferation and anti-apoptosis effect on MM cell lines. Furthermore, nuclear factor-κB (NF-κB) pathway was involved in miR-9/TRIM56-mediated regulation on MM cell lines. miR-9 promoted the development and progression of MM by regulating TRIM56/NF-κB pathway, thereby providing a potential microRNA-based target for MM therapy.

MiR-9 promotes the phenotypic switch of vascular smooth muscle cells by targeting KLF5

Background/aim

Diabetic vascular smooth muscle cells (VSMCs) are characterized by increased proliferation and migration. Small noncoding microRNAs (miRNAs) have been considered critical modulators of the VSMC phenotypic switch after an environmental stimulus. However, microRNA in high glucose-induced proinflammation and its atherogenic effect is still ambiguous.

Materials and methods

The technique of qRT-PCR was used to examine the expression of miR-9 in VSMCs. The downstream signaling protein relative to miR-9 regulation, Krüppel-like factor 5, and some marker genes of contractile VSMCs were analyzed by western blotting and qRT-PCR. Luciferase reporter assay was used to detect the expression of KLF5, which is regulated by miR-9. To examine the function of a miR-9 inhibitor in VSMC proliferation and migration, VSMC proliferation and migration assays were performed.

Results

Reduced transcriptional levels of miR-9 and expression of specific genes of contractile VSMCs were observed in the SMC cell line C-12511 treated with high glucose and SMCs, which were isolated from db/db mice. Moreover, the activity of KLF5 3′-UTR was dramatically reduced by a miR-9 mimic and increased by a miR-9 inhibitor. The proliferation and migration of SMCs were reduced by the miR-9 mimic.

Conclusion

miR-9 inhibits the proliferation and migration of SMC by targeting KLF5 in db/db mice.

Inhibition of miR-9 attenuates fibroblast proliferation in human hyperplastic scar by regulating TGF-β1

Healing of damaged tissue results in scar development, which can be difficult to manage. The present study was performed to determine the effects of inhibition of the microRNA (miR), miR-9, on the proliferation of fibroblasts in human hyperplastic scar (HS) formation. Samples of HS tissue and normal tissue were isolated from 20 patients, and the fibroblasts were transfected with small-interfering RNA (siRNA) for transforming growth factor beta 1 (TGF-β1), miR-9 mimic, and miR-9 inhibition. TGF-β1 protein and mRNA expression were examined in the fibroblasts and HS tissue samples by Western blotting and RT-PCR, respectively. Moreover, the effects of miR-9 inhibitor and mimic on cell proliferation and apoptosis were also examined in the HS tissue. Protein and mRNA expression levels of TGF-β1 were increased in the HS tissue compared to adjacent normal tissues. The levels of TGF-β1 mRNA and protein expression were reduced in siRNA-transfected cells. The miR-9 and TGF-β1 mRNA expression levels were reduced in the miR-9 inhibitor treatment group compared to both the negative control (NC) and control groups. Reduced levels of miR-9 and TGF-β1 mRNA expression were observed in the miR-9 inhibitor treatment group compared to the NC and control groups. Moreover, miR-9 inhibitor increased the percentage of apoptotic cells and decreased cell proliferation compared to the NC and control groups. In conclusion, this study showed that miR-9 plays an important role in the proliferation of fibroblasts by regulating TGF-β1 expression in HS tissue.

PTB-AS, a Novel Natural Antisense Transcript, Promotes Glioma Progression by Improving PTBP1 mRNA Stability with SND1

Glioma, the most common primary malignancy in the brain, has high recurrence and lethality rates, and thus, elucidation of the molecular mechanisms of this incurable disease is urgently needed. Poly-pyrimidine tract binding protein (PTBP1, also known as hnRNP I), an RNA-binding protein, has various mechanisms to promote gliomagenesis. However, the mechanisms regulating PTBP1 expression are unclear. Herein, we report a novel natural antisense noncoding RNA, PTB-AS, whose expression correlated positively with PTBP1 mRNA. We found that PTB-AS significantly promoted the proliferation and migration in vivo and in vitro of glioma cells. PTB-AS substantially increased the PTBP1 level by directly binding to its 3' UTR and stabilizing the mRNA. Furthermore, staphylococcal nuclease domain-containing 1 (SND1) dramatically increased the binding capacity between PTB-AS and PTBP1 mRNA. Mechanistically, PTB-AS could mask the binding site of miR-9 in the PTBP1-3' UTR; miR-9 negatively regulates PTBP1. To summarize, we revealed that PTB-AS, which maintains the PTBP1 level through extended base pairing to the PTBP1 3' UTR with the assistance of SND1, could significantly promote gliomagenesis.

Expression of miR-9 and miR-200c, ZEB1, ZEB2 and E-cadherin in Non-Small Cell Lung Cancers in Iran

MicroRNAs (miRNAs) exert a critical influence on physiological and pathological processes through post-transcriptional modification of their mRNA targets. They play important roles in tumorigenesis and are considered to be potential diagnostic and prognostic biomarkers with various cancers. MiR-200c and miR-9 are regulatory elements that can have dual impacts as oncogenes and/or tumor suppressor genes. MiR-200c regulates two transcription factors, ZEB1 and ZEB2, while miR-9 is a regulatory factor for the E-cadherin protein which has a critical function in cell-cell junctions and is inhibited by two transcription factors ZEB1 and ZEB2. In this study, expression levels of miR-200c and miR-9, ZEB-1, ZEB-2 and E-cadherin were assessed in 30 non-small cell lung cancers (NSCLCs) by real-time qPCR. MiR-9 was down-regulated significantly in tumor tissues compared to normal adjacent tissues, while there was no significant change in expression level of miR-200c. On the other hand, ZEB1 demonstrated significant increase and ZEB2a decrease at the mRNA level. These results indicate roles for miR-9 and ZEB1 in genesis of lung cancer, although clinico-pathological associations were not evident. Further studies are necessary to assess implications for treatment of lung cancer.

Myeloid leukemia with high EVI1 expression is sensitive to 5-aza-2'-deoxycytidine by targeting miR-9

PURPOSE

High expression of ecotropic viral integration site 1 (EVI1) has been associated with a poor prognosis in leukemia patients, but the underlying mechanism remains unclear. Aberrant expression of microRNAs plays critical roles in leukemia development. MiR-9 is a putative potential target of EVI1. We have investigated the regulating mechanism of miR-9 by EVI1 in leukemia cells.

METHODS

We first examined the relationship between miR-9 and EVI1 expression levels in nine leukemia cell lines by RT-PCR. Then we forced high expression of EVI1 in UoCM1 and K562 cells to confirm the downregulation of miR-9 by EVI1. Methylation of the miR-9 promoter region was detected by DNA bisulfite sequencing. We treated the EVI1-overexpressing cells with the hypomethylating agent 5-aza-2'-deoxycytidine (5-AZA) to reverse EVI1-induced hypermethylation of miR-9.

RESULTS

EVI1 and miR-9 expression was negative related. Forced expression of EVI1 downregulated miR-9 by inducing hypermethylation of the miR-9 promoter. 5-AZA reversed high EVI1-induced hypermethylation of the miR-9 promoter and restored the expression of miR-9. 5-AZA induced extensive apoptosis and inhibited proliferation through cell cycle arrest in EVI1-overexpressing leukemia cells.

CONCLUSIONS

Our results suggest that EVI1 may be involved in leukemia cell proliferation and apoptosis via the regulation of miR-9 promoter methylation. 5-AZA may represent a promising therapeutic option for EVI1-high leukemia patients.

Oestrogen-related receptor alpha mediates chemotherapy resistance of osteosarcoma cells via regulation of ABCB1

Chemotherapy resistance is one of the major challenges for the treatment of osteosarcoma (OS). The potential roles of oestrogenic signals in the chemoresistance of OS cells were investigated. As compare to the parental cells, the doxorubicin and cisplatin (CDDP) resistant OS cells had greater levels of oestrogen-related receptors alpha (ERRα). Targeted inhibition of ERRα by its specific siRNAs or inverse agonist XCT-790 can restore the sensitivity of OS resistant cells to chemotherapy. This might be due to that si-ERRα can decrease the expression of P-glycoprotein (P-gp, encoded by ABCB1), one important ABC membrane transporter for drug efflux. XCT-790 can decrease the transcription and mRNA stability of ABCB1, while had no effect on protein stability of P-gp. ERRα can bind to the transcription factor of SP3 to increase the transcription of ABCB1. Furthermore, XCT-790 treatment decreased the expression of miR-9, which can bind to the 3'UTR of ABCB1 and trigger its decay. Collectively, we found that ERRα can regulate the chemoresistance of OS cells via regulating the transcription and mRNA stability of ABCB1. Targeted inhibition of ERRα might be a potential approach for OS therapy.

MiR-9 promotes tumorigenesis and angiogenesis and is activated by MYC and OCT4 in human glioma

BACKGROUND

Glioma, characterized by its undesirable prognosis and poor survival rate, is a serious threat to human health and lives. MicroRNA-9 (miR-9) is implicated in the regulation of multiple tumors, while the mechanisms underlying its aberrant expression and functional alterations in human glioma are still controversial.

METHODS

Expressions of miR-9 were measured in GEO database, patient specimens and glioma cell lines. Gain- and loss-of-function assays were applied to identify the effects of miR-9 on glioma cells and HUVECs in vitro and in vivo. Potential targets of miR-9 were predicted by bioinformatics and further verified via in vitro experiments. Transcriptional regulation of miR-9 by MYC and OCT4 was determined in glioma cells.

RESULTS

MiR-9 was frequently up-regulated in glioma specimens and cells, and could significantly enhance proliferation, migration and invasion of glioma cells. In addition, miR-9 could be secreted from glioma cells via exosomes and was then absorbed by vascular endothelial cells, leading to an increase in angiogenesis. COL18A1, THBS2, PTCH1 and PHD3 were verified as the direct targets of miR-9, which could elucidate the miR-9-induced malignant phenotypes in glioma cells. MYC and OCT4 were able to bind to the promoter region of miR-9 to trigger its transcription.

CONCLUSIONS

Our results highlight that miR-9 is pivotal for glioma pathogenesis and can be treated as a potential therapeutic target for glioma.

Long non-coding RNA SNHG7 promotes the fracture repair through negative modulation of miR-9

Fracture is the most common disease in the orthopedics. Long non-coding small nucleolar RNA host gene 7 (SNHG7) has been confirmed to enhance cell proliferation and decrease cell apoptosis in many cancers. However, the role of SNHG7 in skeletal fracture remains largely to be elucidated. In the current study, we observed SNHG7 was down-regulated in femoral neck fracture tissues. In addition, SNHG7 knockdown inhibited proliferation and migration, induced apoptosis, reduced activity in osteoblast cells in vitro. Bioinformatics analysis revealed SNHG7 acts as a molecular sponge for miR-9 and MiR-9 directly targets with 3'-UTR of TGFBR2. Furthermore, SNHG7 knockdown repressed the TGF-β signaling pathway. Taken together, this study manifested SNHG7 promotes bone repair in femoral neck fracture, and may serve as a potential target for enhancing bone formation.

miR-9 knockdown inhibits hypoxia-induced cardiomyocyte apoptosis by targeting Yap1

AIMS

Aberrantly expressed miRNAs are demonstrated to be involved in the development of congenital heart disease (CHD). miR-9 was proposed to be upregulated in cardiac tissues from CHD cases. However, the role of miR-9 in hypoxia-induced cardiomyocytes and the potential mechanism are far from being addressed.

MAIN METHODS

qRT-PCR and western blot analysis were performed to detect miR-9 and Yes-associated protein 1 (Yap1) expressions in hypoxic H9c2 cells. CCK-8, flow cytometry analysis, caspase-3/7 activity assay were applied to evaluate cell proliferation, apoptosis, and caspase-3/7 activity, respectively. The interaction between miR-9 and Yap1 was explored by luciferase reporter assay, qRT-PCR and western blot.

KEY FINDINGS

miR-9 was upregulated and Yap1 was downregulated in H9c2 cells in response to hypoxia in a time-dependent manner. Knockdown of miR-9 promoted cell proliferation, and inhibited apoptosis and caspase-3/7 activity in hypoxic H9c2 cells, while miR-9 overexpression exerted the opposite effects on hypoxic H9c2 cells. In addition, Yap1 was a direct target of miR-9 in H9c2 cells. Yap1 knockdown suppressed cell proliferation and promoted apoptosis in hypoxia-exposed H9c2 cells. Yap1 knockdown attenuated the effect of anti-miR-9 on cell proliferation and apoptosis in hypoxia-exposed H9c2 cells.

SIGNIFICANCE

miR-9 knockdown inhibited hypoxia-induced cardiomyocyte apoptosis by targeting Yap1. Our study provided a novel insight into the mechanism of the adaptation of cardiomyocytes to chronic hypoxia.

The microRNAs let-7 and miR-9 down-regulate the axon-guidance genes Ntn1 and Dcc during peripheral nerve regeneration

Axon guidance helps growing neural axons to follow precise paths to reach their target locations. It is a critical step for both the formation and regeneration of neuronal circuitry. Netrin-1 (Ntn1) and its receptor, deleted in colorectal carcinoma (Dcc) are essential factors for axon guidance, but their regulation in this process is incompletely understood. In this study, using quantitative real-time RT-PCR (qRT-PCR) and biochemical and reporter gene assays, we found that the Ntn1 and Dcc genes are both robustly up-regulated in the sciatic nerve stump after peripheral nerve injury. Moreover, we found that the microRNA (miR) let-7 directly targets the Ntn1 transcript by binding to its 3'-untranslated region (3'-UTR), represses Ntn1 expression, and reduces the secretion of Ntn1 protein in Schwann cells. We also identified miR-9 as the regulatory miRNA that directly targets Dcc and found that miR-9 down-regulates Dcc expression and suppresses the migration ability of Schwann cells by regulating Dcc abundance. Functional examination in dorsal root ganglion neurons disclosed that let-7 and miR-9 decrease the protein levels of Ntn1 and Dcc in these neurons, respectively, and reduce axon outgrowth. Moreover, we identified a potential regulatory network comprising let-7, miR-9, Ntn1, Dcc, and related molecules, including the RNA-binding protein Lin-28 homolog A (Lin28), SRC proto-oncogene nonreceptor tyrosine kinase (Src), and the transcription factor NF-κB. In summary, our findings reveal that the miRs let-7 and miR-9 are involved in regulating neuron pathfinding and extend our understanding of the regulatory pathways active during peripheral nerve regeneration.

Structural Differences between Pri-miRNA Paralogs Promote Alternative Drosha Cleavage and Expand Target Repertoires

MicroRNA (miRNA) processing begins with Drosha cleavage, the fidelity of which is critical for downstream processing and mature miRNA target specificity. To understand how pri-miRNA sequence and structure influence Drosha cleavage, we studied the maturation of three pri-miR-9 paralogs, which encode the same mature miRNA but differ in the surrounding scaffold. We show that pri-miR-9-1 has a unique Drosha cleavage profile due to its distorted and flexible stem structure. Cleavage of pri-miR-9-1, but not pri-miR-9-2 or pri-miR-9-3, generates an alternative miR-9 with a shifted seed sequence that expands the scope of its target RNAs. Analyses of low-grade glioma patient samples indicate that the alternative-miR-9 has a potential role in tumor progression. Furthermore, we provide evidence that distortion of pri-miRNA stems induced by asymmetric internal loops correlates with Drosha cleavage at non-canonical sites. Our studies reveal that pri-miRNA paralogs can have distinct functions via differential Drosha processing.

Down-regulation of miR-9 promotes epithelial mesenchymal transition via regulating anoctamin-1 (ANO1) in CRC cells

MicroRNA-9 (miR-9) has been reported to play a suppressive or promoting role according to cancer type. In this study, we investigated the effects of anoctamin-1 (ANO1) and miR-9 on colorectal cancer (CRC) cell proliferation, migration, and invasion and determined the underlying molecular mechanisms. Thirty-two paired CRC tissues and adjacent normal tissues were analyzed for ANO1 expression using quantitative real-time PCR (qRT-PCR). HCT116 cells were transiently transfected with miR-9 mimic, miR-9 inhibitor, or si-ANO1. Cell proliferation was determined by MTT, and flow cytometric analysis, while cell migration and invasion were assayed by trans-well migration and invasion assay in HCT116 cells. ANO1 was validated as a target of miR-9 using luciferase reporter assay and bioinformatics algorithms. We found that ANO1 expression was up-regulated in CRC tissues compared with adjacent normal tissues. ANO1 expression was associated with advanced tumor stage and lymph node metastasis, and there was an inverse relationship between miR-9 and ANO1 mRNA expression in CRC specimens, but no significant difference was found between miR-9 and ANO1 expression. ANO1 is a direct target of miR-9, and overexpression of miR-9 suppressed both mRNA and protein expression of ANO1 and inhibited cell proliferation, migration, and invasion of HCT116 cells. We also showed that overexpression of miR-9 suppressed expression of p-AKT, cyclin D1, and p-ERK in HCT116 cells. We conclude that miR-9 inhibits CRC cell proliferation, migration, and invasion by directly targeting ANO1, and miR-9/ANO1 could be a potential therapeutic target for CRC.

Expression of miR-9 in the serum of patients with acute ischemic stroke and its effect on neuronal damage

BACKGROUND

This research was aimed to measure the expression of miR-9 in serum of acute ischemic stroke (AIS) patients and explore the role of miR-9 on OGD-induced neuronal damage.

METHODS

In the present study, we measured the expression of miR-9 in serum of 65 AIS patients by real-time quantitative PCR (RT-qPCR) and the effect of miR-9 on oxygen-glucose deprivation (OGD)-induced neuronal injury was detected by CCK-8 in vitro. Western blot was used to measure the expression of protein.

RESULTS

We found that the serum level of miR-9 in 65 AIS patients was significantly higher than that in control group (no-AIS), and was positively correlated with NIHSS score (r=0.627, P<0.001), infarct volume ((r=0.576, P<0.001), serum IL-8 (r=0.376, P=0.002), TNF-α (r=0.418, P<0.001), IL-6 (r=0.545, P<0.001), and IL-1β (r=0.592, P<0.001). miR-9 expression levels were upregulated in cultured neurons with OGD treatment. The downregulation of miR-9 significantly alleviated OGD-induced neuronal injury. Dual-luciferase reporter assay demonstrated that SIRT1 was a target gene of miR-9, and miR-9 negatively regulated SIRT 1 expression and positively regulated p65 expression.

CONCLUSIONS

All in all, our data showed that downregulation of miR-9 protected neurons against OGD/R-induced injury by the SIRT1-mediated NF-kB pathway.

RETRACTED: Emodin protects hyperglycemia-induced injury in PC-12 cells by up-regulation of miR-9

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editors. Given the comments of Dr Elisabeth Bik regarding this article “… the Western blot bands in all 400+ papers are all very regularly spaced and have a smooth appearance in the shape of a dumbbell or tadpole, without any of the usual smudges or stains. All bands are placed on similar looking backgrounds, suggesting they were copy/pasted from other sources, or computer generated”, the journal requested the authors to provide the raw data. However, the authors were not able to fulfil this request and therefore the Editors decided to retract the article.

Expression of MicroRNA-9 is Associated With Overall Survival in Breast Cancer Patients

BACKGROUND

MicroRNA-9 (miR-9) was found to play an important role in a variety of different cancers and can adopt either tumor suppressor or oncogenic activity. Most studies have suggested an oncogenic role in breast cancer. We were interested in the relationship of miR-9 expression and survival in breast cancer and hypothesized that high expression of miR-9 was associated with worse prognosis in breast cancer patients.

MATERIALS AND METHODS

We utilized The Cancer Genome Atlas containing genetic and molecular data, clinical profiles, and survival information for 985 breast cancers. Survival analysis was performed comparing a group with low expression of miR-9 to a group with high expression. Expression of miR-9 was compared based on clinicopathological parameters. Gene set enrichment analysis was performed between the miR-9 high- and low-expression groups within the estrogen receptor (ER)-positive cohort.

RESULTS

Low expression of miR-9 associated significantly with improved overall survival (OS) (P = 0.003). There was no significant difference in miR-9 expression with regard to disease-free survival. Smaller and early-stage tumors were associated with lower miR-9 expression. ER-positive breast cancers had lower levels of miR-9 than ER-negative breast cancers (P < 0.001), and within the ER-positive group, miR-9 expression was significantly associated with OS (P = 0.02). Gene set enrichment analysis showed enrichment of estrogen response genes in the miR-9 low-expression group.

CONCLUSIONS

Low miR-9 expression appeared to have a protective effect and was associated with improved OS, smaller tumors, earlier stage, and ER-positive cancers due to enrichment of estrogen response genes.