Interaction of long noncoding RNA MEG3 with miRNAs: A reciprocal regulation

The competitive endogenous RNA (ceRNA) hypothesis suggests that a long noncoding RNA (lncRNA) can function as sinks for pools of microRNAs (miRNAs); thereby, in the presence of ceRNA, messenger RNAs (mRNAs) targeted by specific miRNAs can liberate and translate to protein. Maternally expressed gene 3 (MEG3) is a lncRNA, which its expression has been detected in various normal tissues, while it is lost or downregulated in human tumors. The MEG3 is an imprinted gene which, is methylated and suppressed by DNA methyltransferases (DNMTs) family. Also, miRNAs are involved in the regulation of MEG3 gene expression. Interestingly, the lncRNA MEG3 (lnc-MEG3), as a ceRNA affects various cell processes such as proliferation, apoptosis, and angiogenesis by sponging miRNAs. These miRNAs, in turn, regulate different mRNAs in different pathways. This review focuses on the interaction between lnc-MEG3 and experimentally validated miRNAs. In addition, the discussion supplemented by some data obtained from mirPath (v.3) and TarBase (v.8) databanks to provide more details about the pathways affected by this ceRNA.     

Long noncoding RNA lnc-ABCA12-3 promotes cell migration,invasion, and proliferation by regulating fibronectin 1 in esophageal squamous cell carcinoma

Long noncoding RNAs (lncRNAs) have been shown to play important roles in human cancers, including esophageal squamous cell carcinoma (ESCC). We previously demonstrated that a novel lncRNA, lnc-ABCA12-3, was overexpressed in ESCC tissues. However, the exact function of lnc-ABCA12-3 is unknown. In the current study, we aimed to evaluate the expression of lnc-ABCA12-3 in ESCC and to explore the potential mechanism of lnc-ABCA12-3 in cell migration, invasion, and proliferation. We showed that lnc-ABCA12-3 was upregulated in ESCC tumor tissues and cell lines. The increased expression of lnc-ABCA12-3 was positively associated with advanced tumor-node-metastasis stages and poor prognosis. The knockdown of lnc-ABCA12-3 inhibited the cell migration, invasion, and proliferation abilities of KYSE-510 and Eca-109 cells. We also found that fibronectin 1 (FN1) was upregulated in ESCC tumor tissues. The expression of FN1 messenger RNA was positively correlated with the expression of lnc-ABCA12-3 in ESCC tumor tissues. After lnc-ABCA12-3 knockdown, the expression of FN1 was downregulated. In addition, the overexpression of FN1 restored the abilities of cell migration, invasion and proliferation in Eca-109 cells. Further studies indicated that lnc-ABCA12-3 acted as a competing endogenous RNA for miR-200b-3p to regulate FN1 expression. In conclusion, these results suggest that lnc-ABCA12-3 is a novel oncogene in tumorigenesis and that its high expression is related to a poor prognosis for patients with ESCC. lnc-ABCA12-3 promotes cell migration, invasion, and proliferation via the regulation of FN1 in ESCC. Our data suggest that lnc-ABCA12-3 might serve as a potential prognostic biomarker and therapeutic target for ESCC.     

Retracted: Deletion of long noncoding RNA EFNA3 aggravates hypoxia-induced injury in PC-12 cells by upregulation of miR-101a

Long noncoding RNAs (lncRNAs) have been reported to be involved in several neurological pathogenesis conditions including cerebral ischemia. In the current study, the functions of lncRNA EFNA3 on hypoxia-injured rat adrenal pheochromocytoma (PC-12) cells and the underlying molecular mechanism were studied. The expression of lncRNA EFNA3 was silenced by short hairpin RNA transfection, after which the cells were subjected with hypoxia. Cell viability, migration, invasion, and apoptosis were, respectively, determined by trypan blue staining, Transwell assay, annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) double-staining, and Western blot analysis. The cross regulation between lncRNA EFNA3 and miR-101a, as well as between miR-101a and Rho associated coiled-coil containing protein kinase 2 (ROCK2) were detected by performing quantitative real-time polymerase chain reaction, RNA pull-down, RNA immunoprecipitation, luciferase activity assay, and Western blot analysis. Studies showed that lncRNA EFNA3 was highly expressed in response to hypoxia. Deletion of lncRNA EFNA3 significantly aggravated hypoxia-induced injury in PC-12 cells, as the impairment of cell viability, migration, and invasion, and the inducement of apoptosis. LncRNA EFNA3 worked as a sponging molecule for miR-101a and miR-101a suppression-protected PC-12 cells against hypoxia-induced injury even when lncRNA EFNA3 was silenced. ROCK2 was a target gene of miR-101a. ROCK2 overexpression exhibited neuroprotective activities. Besides, ROCK2 overexpression activated Wnt/β-catenin pathway whereas it deactivated JAK/STAT pathway upon hypoxia. Our study suggests that deletion of lncRNA EFNA3 aggravates hypoxia-induced injury in PC-12 cells by upregulating miR-101a, which further targets ROCK2.     

CircSLC7A2 protects against osteoarthritis through inhibition of the miR‐4498/TIMP3 axis

ObjectivesCircular RNAs (circRNAs) are noncoding RNAs that compete against other endogenous RNA species, such as microRNAs, and have been implicated in many diseases. In this study, we investigated the role of a new circRNA (circSLC7A2) in osteoarthritis (OA).Materials and MethodsThe relative expression of circSLC7A2 was significantly lower in OA tissues than it was in matched controls, as shown by real‐time quantitative polymerase chain reaction (RT‐qPCR). Western blotting, RT‐qPCR and immunofluorescence experiments were employed to evaluate the roles of circSLC7A2, miR‐4498 and TIMP3. The in vivo role and mechanism of circSLC7A2 were also conformed in a mouse model.ResultscircSLC7A2 was decreased in OA model and the circularization of circSLC7A2 was regulated by FUS. Loss of circSLC7A2 reduced the sponge of miR‐4498 and further inhibited the expression of TIMP3, subsequently leading to an inflammatory response. We further determined that miR‐4498 inhibitor reversed circSLC7A2‐knockdown‐induced OA phenotypes. Intra‐articular injection of circSLC7A2 alleviated in vivo OA progression in a mouse model of anterior cruciate ligament transection (ACLT).ConclusionsThe circSLC7A2/miR‐4498/TIMP3 axis of chondrocytes catabolism and anabolism plays a critical role in OA development. Our results suggest that circSLC7A2 may serve as a new therapeutic target for osteoarthritis.     

Long noncoding RNA LINC00958 regulates cell sensitivity to radiotherapy through RRM2 by binding to microRNA-5095 in cervical cancer

Long noncoding RNAs (lncRNAs) have been implicated in the regulation of resistance to radiotherapy in cervical cancer, which is a type of gynecological disease with high mortality in women around the world. Hence, our purpose is to delineate the involvement of LINC00958 in regulating cell sensitivity to radiotherapy in cervical cancer. LINC00958 expression in cervical cancer was assayed, followed by verification of the relationship among LINC00958, microRNA-5095 (miR-5095) and ribonucleotide reductase subunit M2 (RRM2). Hela cells were transduced with up-/downregulation of miR-5095 or RRM2, or LINC00958 silencing, respectively, and then treated with or without a 6 Gy dose of X-ray irradiation. Then the cell proliferation, apoptosis, survival fraction rate, as well as sensitivity to radiotherapy, were assessed. Finally, xenograft tumor in nude mice was established by transplanting Hela cells transfected with sh-LINC00958 and irradiated with 6 Gy of X-ray. High expression of LINC00958 was revealed in The Cancer Genome Atlas and Gene Expression Profiling Interactive Analysis, as well as in radiation-resistant patients, which was associated with lower sensitivity to radiotherapy in cervical cancer. Moreover, cervical cancer patients with higher LINC00958 expression exhibited a shorter overall survival according to Kaplan–Meier analysis. In addition, LINC00958 could regulate the expression of RRM2 by competing for miR-5095. A combination of radiotherapy with LINC00958 silencing, RRM2 downregulation or miR-5095 overexpression was found to inhibit cervical cancer cell proliferation and tumor growth, while promoting cell apoptosis both in vitro and in vivo. Collectively, our results suggest that LINC00958 could regulate RRM2 by competing to miR-5095, which regulates cell sensitivity to radiotherapy in cervical cancer.     

Long noncoding RNA POU3F3 promotes cancer cell proliferation in prostate carcinoma by upregulating rho-associated protein kinase 1

Long noncoding RNAs (lncRNAs) POU3F3 is overexpressed in esophageal squamous-cell carcinomas, while its role in other human cancers is unclear. In this study we found that POU3F3 and rho-associated protein kinase 1 (ROCK1) were both increased in tumor tissues than in adjacent healthy tissues of patients with prostate carcinoma. Expression levels of POU3F3 increased with increase in the diameter of tumor but were not significantly affected by lymph node metastasis or distant metastasis. Expression levels of POU3F3 and ROCK1 were positive correlated in tumor tissues but not in adjacent healthy tissues. POU3F3 and ROCK1 overexpression promoted, while ROCK1 knockdown inhibited the proliferation of prostate carcinoma cells. ROCK1 knockdown reduced the enhancing effect of POU3F3 overexpression on cancer cell proliferation. POU3F3 overexpression led to ROCK1 overexpression in prostate carcinoma cells, while ROCK1 overexpression did not significantly affect POU3F3 expression. Therefore, lncRNA POU3F3 may promote cancer cell proliferation in prostate carcinoma by upregulating ROCK1.     

LncRNA MEG3 inhibits rheumatoid arthritis through miR‐141 and inactivation of AKT/mTOR signalling pathway

Rheumatoid arthritis (RA) is a chronic inflammation mediated by autoimmune responses. MEG3, a kind of long noncoding RNA (lncRNA), participates in cell proliferation in cancer tissues. However, the correlation between MEG3 and RA is yet unclear. Therefore, to clarify how MEG3 works in RA, we performed a series of experiments using RA samples. We found that MEG3 was downregulated in the fibroblast‐like synoviocytes of RA patients (RA‐FLS), in comparison with healthy subjects. MEG3 was also down‐regulated evidently in lipopolysaccharide (LPS)‐treated chondrocyte. As part of our experiments, MEG3 was overexpressed in chondrocyte by transfection with lentivirus containing sequences encoding MEG3. In addition, in presence of LPS, reductions were identified not only in the cell proliferation, but also in the generation of interleukin‐23 (IL‐23), which, however were reversed in the lentivirus (containing MEG3‐encoding sequences)‐transfected chondrocytes. Up‐regulated MEG3 resulted in an increase the level of Ki67. Moreover, MEG3 was negatively correlated with miR‐141, and miR‐141 was up‐regulated in LPS‐treated chondrocyte. Inhibitory effects of MEG3 overexpression, mentioned above, were partially abolished by overexpressed miR‐141. Further, animal experiment also showed the inhibitory effect of MEG3 in overexpression on the AKT/mTOR signaling pathway. In‐vivoexperiments also showed that cell proliferation was facilitated by MEG3 overexpression with inhibited inflammation. In summary, the protective role of MEG3 in RA was proved to be exerted by the increase in the rate of proliferation, which might correlate to the regulatory role of miR‐141 and AKT/mTOR signal pathway, suggesting that MEG3 holds great promise as a therapeutic strategy for RA.     

Long noncoding RNA MNX1-AS1 contributes to lung cancer progression through the miR-527/BRF2 pathway

Lung cancer belongs to a leading popular and malignant cancer around the world. However, the root mechanism underlying lung cancer progression remains unclear. Recently, long noncoding RNA (lncRNA) has been identified as important for tumorigenesis. LncRNA MNX1-AS1 is proven to regulate colon adenocarcinoma, cervical cancer, glioblastoma, and ovarian cancer. Whether MNX1-AS1 participates in lung cancer needs investigation. In our research, we found that MNX1-AS1 was dramatically upregulated in lung cancer. MNX1-AS1 upregulation indicated poor prognosis in lung cancer patients. Functionally, MNX1-AS1 promoted lung cancer progression through regulating proliferation, migration, and invasion. Mechanistically, MNX1-AS1 was found to locate in the cytoplasm and interact with miR-527. Through inhibiting miR-527 availability, MNX1-AS1 facilitated BRF2 expression. Restoration of BRF2 rescued defects of proliferation, migration, and invasion caused by MNX1-AS1 knockdown. Taken together, our study found a novel signaling pathway, namely MNX1-AS1/miR-527/BRF2 axis, involved in lung cancer progression.     

The expression of long noncoding RNA CRCAL-3 in colorectal cancer and its impacts on cell proliferation and migration

Long noncoding RNAs (lncRNAs) have been implicated in colorectal cancer (CRC). And lncRNA RP11-138J23.1 (CRCAL-3) was previously reported as a candidate regulator of CRC development. But its regulating functions have not been fully elucidated. Here, we analyzed RNA sequencing data from the Cancer Genome Atlas (TCGA) and 253 CRC patients treated in our hospital to assess expression dysregulation of CRCAL-3, and the correlation between CRCAL-3 expression and disease progression. Further, polymerase chain reaction (PCR) assay on different cell lines and knockdown experiments by small interfering RNA were performed to assess functions of CRCAL-3 in proliferation and migration of CRC cells. As a result, analyses on TCGA datasets showed an upregulated CRCAL-3 expression in 14 solid tumors, including CRC. PCR assay on 253 cases of CRC tissue and 114 cases of normal adjacent tissue confirmed this expression upregulation. Also, CRCAL-3 expression was exhibited by survival analyses on the 253 CRC patients, to have a negative correlation with patients' overall and progression-free survivals. PCR assay on different cell lines showed that CRC cells expressed a higher level of CRCAL-3, compared with normal colonic epithelial cells. In vitro knockdown of CRCAL-3 resulted in an obvious retardation of proliferation and migration in two CRC cell lines (HCT116 and DLD-1). Moreover, CRCAL-3 knockdown was observed in xenograft models to repress cell proliferation and enhance cisplatin sensitivity. Taking these results together, CRCAL-3 emerged as a biomarker for early diagnosis, prognosis prediction, and individualized treatment of CRC.     

Puerarin protects PC12 cells against beta-amyloid-induced cell injury

beta-Amyloid protein (Abeta), a major protein component of brain senile plaques in Alzheimer's disease, is known to be directly responsible for the production of reactive oxygen species (ROS) and induction of apoptosis. In this study, the protective effect of puerarin, an isoflavone purified from the radix of the Chinese herb Pueraria lobata, on Abeta-induced rat pheochromocytoma (PC12) cultures was investigated. Although exposure of PC12 cells to 50 microM Abeta25-35 caused significant viability loss and apoptotic rate increase, pretreatment of the cells with puerarin for 24h reduced the viability loss and apoptotic rate. Puerarin (1 microM) significantly inhibited Abeta25-35-induced apoptosis of PC12 cells. Preincubation of the cell with puerarin also restored the ROS and mitochondrial membrane potential levels that had been altered as a result of Abeta25-35 treatment. Puerarin was also found to increase the Bcl-2/Bax ratio and reduce caspase-3 activation. These results suggest that puerarin could attenuate Abeta25-35-induced PC12 cell injure and apoptosis and could also promote the survival of PC12 cells. Therefore, puerarin may act as an intracellular ROS scavenger, and its antioxidant properties may protect against Abeta25-35-induced cell injury.     

Long noncoding RNA HOXA-AS2 regulates the expression of SCN3A by sponging miR-106a in breast cancer

Breast cancer is the most commonly diagnosed cancer that affects women worldwide. This study aimed to investigate the competing endogenous RNAs (ceRNAs) mechanism in breast cancer. Microarray data were downloaded from the University of California Santa Cruz (UCSC) Xena database. The limma package was used to screen the differentially expressed messenger RNAs (DEMs) and differentially expressed long noncoding RNAs (DELs). Subsequently, functional analysis was performed using DAVID tool. After constructing the protein-protein interaction (PPI) network, we identified the major gene modules using the Cytoscape software. Univariate survival analysis in the survival package was performed. Finally, the ceRNA regulatory network was constructed to identify the critical genes. A total of 1380 DEMs and 345 DELs were identified in breast cancer samples compared with normal samples. Functional enrichment analysis showed that DEMs were mainly involved in cell division, and cell cycle. We screened four major gene modules and identified the hub nodes in these functional modules. Several DEMs (including FABP7, C4BPA, and LAMB3) and three long noncoding RNAs (lncRNAs) (LINC00092, SLC26A4.AS1, and COLCA1) exhibited significant correlation with patients' survival outcomes. In the ceRNA network, the lncRNA HOXA-AS2 regulated the expression level of SCN3A by interacting with hsa-miR-106a-5p. Thus, our study investigated the ceRNA mechanism in breast cancer. The results showed that lncRNA HOXA-AS2 might modulate the expression of SCN3A by sponging miR-106a in breast cancer.     

Long noncoding RNA SBF2-AS1 promotes colorectal cancer proliferation and invasion by inhibiting miR-619-5p activity and facilitating HDAC3 expression

Evidence, demonstrating long noncoding RNAs (lncRNAs) as critical players in cancer, remains to increase. lncRNA SBF2-AS1 was reported to be involved in several cancers, such as hepatocellular carcinoma. However, the role of SBF2-AS1 in colorectal cancer (CRC) is unknown. We showed lncRNA SBF2-AS1 expression was growing in CRC samples, especially in advanced cases. Accordingly, SBF2-AS1 possesses higher expression in CRC cell lines than in normal cell line. Moreover, SBF2-AS1 high expression indicated a low survival rate. Functionally, SBF2-AS1 knockdown suppressed the proliferation, migration, and invasion of CRC cells. In terms of mechanism, SBF2-AS1 upregulation restrained the activity of miR-619-5p and led to overexpression of HDAC3. Importantly, downregulation of miR-619-5p or HDAC3 overexpression reversed SBF2-AS1-silencing-caused suppression on proliferation and metastasis. Summarily, our findings elucidated a crucial role of SBF2-AS1 as a miR-619-5p sponge, shedding novel light on lncRNA-related prognostics.     

Long noncoding RNA FOXD2-AS1 promotes glioma cell cycle progression and proliferation through the FOXD2-AS1/miR-31/CDK1 pathway

Long noncoding RNAs (lncRNAs) are vital mediators involved in cancer progression. Previous studies confirmed that FOXD2 adjacent opposite strand RNA 1 (FOXD2-AS1) is upregulated in tumor diseases. The potential influence of FOXD2-AS1 in glioma progression, however, remains unknown. In this paper, FOXD2-AS1 was found to be upregulated in glioma tissues. Its level was linked with glioma stage. Moreover, glioma patients expressing high level of FOXD2-AS1 suffered worse prognosis. Biological functions of FOXD2-AS1 in glioma cells were analyzed through integrative bioinformatics and TCGA RNA sequencing data analysis. Pathway enrichment analysis uncovered that FOXD2-AS1 was mainly linked with cell cycle regulation in both low-grade glioma and glioblastoma. Further experiments demonstrated that silence of FOXD2-AS1 inhibited proliferation, arrested cell cycle and downregulated cyclin-dependent kinase 1 (CDK1) in human glioma cells. Dual-luciferase reporter assay confirmed that FOXD2-AS1 upregulated CDK1 by sponging miR-31. Rescue assays were performed and confirmed the regulatory loop FOXD2-AS1/miR-31/CDK1 in glioma. Collectively, our results indicated that the FOXD2-AS1/miR-31/CDK1 axis influenced glioma progression, providing a potential new target for glioma patients.