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Albeit the majority of eukaryotic genomes can be pervasively transcribed to a diverse population of lncRNAs and various subtypes of lncRNA are discovered. However, the genome‐wide study of miRNA‐derived lncRNAs is still lacking. Here, it is reported that over 800 miRNA gene‐originated lncRNAs (molncRNAs) are generated from miRNA loci. One of them, molnc‐301b from miR‐301b and miR‐130b, functions as an "RNA decoy" to facilitate dissociation of the chromatin remodeling protein SMARCA5 from chromatin and thereby sequester transcription and mRNA translation. Specifically, molnc‐301b attenuates erythropoiesis by mitigating the transcription of erythropoietic and translation‐associated genes, such as GATA1 and FOS. In addition, a useful and powerful CRISPR screen platform to characterize the biological functions of molncRNAs at large‐scale and single‐cell levels is established and 29 functional molncRNAs in hematopoietic cells are identified. Collectively, the focus is on miRNA‐derived lncRNAs, deciphering their landscape during normal hematopoiesis, and comprehensively evaluating their potential roles. [ABSTRACT FROM AUTHOR]

The 5p and 3p arms of microRNA (miRNA) are typically generated from the same precursor, and one arm influences protein output, while the other has a short half‐life. However, a few miR‐5p/3p pairs have been reported to co‐exist in cancer cells. Here, we performed a genome‐wide analysis of miRNA expression in gastric cancer (GC) cells to systematically investigate the co‐expression profile of miR‐5p/3p in gastric tumorigenesis. We discovered that only 41 miR‐5p/3p pairs out of 1749 analyzed miRNA were co‐expressed. Specifically, abnormal expression of miR‐369‐5p and miR‐369‐3p was correlated with GC progression. Importantly, both in vitro and in vivo assays revealed that miR‐369‐5p and miR‐369‐3p exhibited tumor‐suppressive roles by regulating jun proto‐oncogene and v‐akt murine thymoma viral oncogene homolog 1 function in GC cells, respectively. Moreover, we observed that miR‐369 was inactivated in GC tissues due to DNA methylation. We also showed that inhibition of miR‐369‐5p/3p attenuated the effect of azacitidine (AZA) treatment on suppressing cell growth and invasion. These results suggest that the therapeutic efficacy of AZA in GC is at least partly attributable to miR‐369 activation. Overall, our findings provide convincing evidence that both the 5p and 3p arms of miRNA co‐expressed in GC and DNA methylation‐induced miR‐369 signaling contribute to GC progression. [ABSTRACT FROM AUTHOR]

MiR‐130b and SAM and SH3 domain containing 1 (SASH1) play an important role in many types of human cancers. The aim of our research was to study their interactions in the process of the proliferation and aggressiveness of oesophageal squamous cell carcinoma (ESCC) cells. Microarray analysis was done to screen the differentially expressed genes in the ESCC tissues. miR‐130b and SASH1 mRNA levels in the ESCC tissues and cells were detected by qRT‐PCR. Dual luciferase reporter system was used to verify the target relationship between miR‐130b and SASH1. The effects of miR‐130b on SASH1 expression were explored by western blot in KYSE30 and TE1 cell lines. CCK‐8 assay, flow cytometry, Transwell, and wound healing assays were conducted to explore the effects of miR‐130b and SASH1 in vitro. In addition, in vivo experiments were conducted to study the roles of miR‐130b and SASH1. miR‐130b was highly expressed, while SASH1 was the opposite in both the ESCC tissues and cells. The expression of SASH1 was inhibited by the direct binding of miR‐130b. The inhibition of miR‐130b reduced the proliferation and aggressiveness of ESCC cells, while it also induced apoptosis and cell cycle arrest in the ESCC cells by suppressing SASH1. The in vivo assay suggested that the overexpression of miR‐130b promoted the growth of ESCC tumours. MiR‐130b was up‐regulated in the ESCC tumour tissues and cells, acting as a tumour promoter. A stimulating effect was demonstrated on ESCC cell growth and aggressiveness by suppressing SASH1, which is an anti‐oncogene. [ABSTRACT FROM AUTHOR]

Micro RNAs play important roles in controlling the embryonic stem cell ( ESC) state. Although much is known about micro RNAs maintaining ESC state, micro RNAs that are responsible for promoting ESC differentiation are less reported. Here, by screening 40 micro RNAs pre-selected by their expression patterns and predicted targets in Dgcr8-null ESCs, we identify 14 novel differentiation-associated micro RNAs. Among them, miR-27a and miR-24, restrained by c-Myc in ESC, exert their roles of silencing self-renewal through directly targeting several important pluripotency-associated factors, such as Oct4, Foxo1 and Smads. CRISPR/Cas9-mediated knockout of all miR-27/24 in ESCs leads to serious deficiency in ESC differentiation in vitro and in vivo. Moreover, depleting of them in mouse embryonic fibroblasts can evidently promote somatic cell reprogramming. Altogether, our findings uncover the essential role of miR-27 and miR-24 in ESC differentiation and also demonstrate novel micro RNAs responsible for ESC differentiation. [ABSTRACT FROM AUTHOR]

Background: MicroRNAs act as tumor suppressors or oncogenes. The pathological roles of miRNAs in gastric tumorigenesis are largely unknown. Although miR-10b was identified as an miRNA deregulator expressed in gastric cancer (GC), there also exists some debate on whether miR-10b is acting as tumor suppressor or oncogene in GC. Methods: Quantitative RT-PCR was employed to investigate the level of miR-10b in GC tissues and matched adjacent normal tissues ( n = 100). In vitro cell proliferation, apoptosis assays, cell migration, and invasion assays were performed to elucidate the biological effects of miR-10b. Because silencing of miRNA by promoter CpG island methylation may be an important mechanism in tumorigenesis, GC cells were treated with 5-aza-2′-deoxycytidine and trichostatin A, and expression changes of miR-10b were subsequently examined by quantitative RT-PCR. Furthermore, the methylation status of the CpG island upstream of miR-10b was analyzed by methylation-specific PCR in GC tissues ( n = 29). Results: We showed here that miR-10b was significantly downregulated in GC cell lines and tissues as demonstrated by quantitative real-time PCR. Overexpression of miR-10b in MGC-803 and HGC-27 dramatically suppressed cell proliferation, migration, invasion, and induced apoptosis. Moreover, we demonstrated that T-cell lymphoma invasion and metastasis (Tiam1) was a target of miR-10b. Furthermore, 5-aza-2′-deoxycytidine and trichostain A increased miR-10b expression, and the methylation level was high in the CpG islands upstream of miR-10b gene. Conclusions: Taken together, these findings suggest that miR-10b may function as a novel tumor suppressor and is partially silenced by DNA hypermethylation in GC. [ABSTRACT FROM AUTHOR]

Background: MicroRNAs act as posttranscriptional regulators of gene expression in many biological processes. Their deregulations occur commonly in gastric cancer (GC). Although DNA methylation constitutes an important mechanism for microRNA deregulation in cancer, this field largely remains unexplored. Methodology/Principal Findings: Total RNA was extracted from the tissues of 100 patients with GC and four gastric cancer cell lines. The expression levels of miR-10a were determined by real-time PCR with specific TaqMan probes. Moreover, a functional analysis of miR-10a in regulating cell proliferation, migration and invasion was performed. Subsequently, quantitative methylation-specific PCR (qMSP) was used to detect the DNA methylation status in the CpG islands upstream of miR-10a. In this study, we found that the expression of miR-10a in GC cells was lower than that in normal cells, which was due to the hypermethylation of the CpG islands upstream of miR-10a. We also validated the slightly lower expression of miR-10a in GC tissues than their adjacent non-neoplastic tissues in 100 GC patients and confirmed the hypermethylation of CpG islands upstream of miR-10a in some patients. Furthermore, re-introduction of miR-10a into GC cells was able to inhibit cell proliferation, migration and invasion. Bioinformatic and immunoblot analysis indicated that the tumor suppressor roles of miR-10a in GC cells were possibly through targeting HOXA1. Conclusions/Significance: Our data indicate that miR-10a acts as a tumor suppressor in GC cells and is partially silenced by DNA hypermethylation in GC, suggesting that miR-10a may serve as a potential diagnostic or therapeutic target of GC. [ABSTRACT FROM AUTHOR]

Background & Aims: Gastric cancer is the most frequent gastrointestinal tumor in adults and is the most lethal form of human cancer. Despite of the improvements in treatments, the underlying mechanism of gastric carcinogenesis is not well known. To define novel modulators that regulate susceptibility to tumorgenesis, we focused on miR-219-2-3p. Methods: Quantitative RT-PCR was employed to investigate the level of miR-219-2-3p in gastric cancer (GC) tissues (n = 113) and their matched adjacent normal tissues (n = 113). In vitro cell proliferation, apoptosis assays, cell migration, and invasion assays were performed to elucidate biological effects of miR-219-2-3p. Since silencing of miRNA by promoter CpG island methylation may be an important mechanism in tumorgenesis, GC cells were treated with 5-aza-2′-deoxycytidine and trichostatin A, and expression changes of miR-219-2-3p were subsequently examined by quantitative RT-PCR. Finally, the methylation status of CpG island upstream of miR-219-2-3p was analyzed by methylation-specific PCR in GC tissues (n = 22). Results: miR-219-2-3p was down-regulated in GC and cell lines. In addition, the experiments documented the lower expression of miR-219-2-3p in GC specimens with higher grade and later stage tumors. Meanwhile, miR-219-2-3p exerted antiproliferative, proapoptotic, and antimetastatic roles and reduced levels of p-ERK1/2 in GC cells. Furthermore, 5-aza-2′-deoxycytidine and trichostatin A increased the expression (∼2 fold) of miR-219-2-3p in GC cells. By methylation-specific PCR, DNA methylation in the upstream region of miR-219-2-3p was detected in both adjacent normal tissues and cancer tissues. As expected, the methylation level was considerably higher in the miR-219-2-3p down-regulated group than up-regulated group. Conclusions: miR-219-2-3p is potentially involved in gastric cancer progression and metastasis by regulating ERK1/2-related signal pathways, which may provide a novel therapeutic strategy for treatment of gastric cancer. Methylation mechanism may be involved in modulating the expression level of miR-219-2-3p in gastric cancer. [ABSTRACT FROM AUTHOR]

Strand-selection is the final step of microRNA biogenesis in which functional mature miRNAs are generated from one or both arms of precursor. The preference of strand-selection is diverse during development and tissue formation, however, its pathological effect is still unknown. Here we find that two miRNA arms from the same precursor, miR-574-5p and miR-574-3p, are inversely expressed and play exactly opposite roles in gastric cancer progression. Higher-5p with lower-3p expression pattern is significantly correlated with higher TNM stages and poor prognosis of gastric cancer patients. The increase of miR-574-5p/-3p ratio, named miR-574 arm-imbalance is partially due to the dynamic expression of their highly complementary targets in gastric carcinogenesis, moreover, the arm-imbalance of miR-574 is in turn involved and further promotes gastric cancer progression. Our results indicate that miR-574 arm-imbalance contribute to gastric cancer progression and re-modification of the miR-574-targets homeostasis may represent a promising strategy for gastric cancer therapy. Functional miRNAs derived from the 5p or 3p arm of some miRNA duplexes have opposite roles in cancer progression. Here, the authors show that oncogenic miR-574-5p has greater preference in aggressive gastric cancer as compared with miR-574-3p and this arm preference is partly dependent on complementary targets mediated miRNA decay. [ABSTRACT FROM AUTHOR]

MicroRNAs have been involved in RNA silencing and post-transcriptional regulation of gene expression and also play important roles in tumorigenesis and tumor progression. MiR-193b was previously reported to act as tumor suppressor in diverse cancers. However, little is known about the expression, function and mechanism of miR-193b in gastric cancer (GC). In this study, we investigated the expression of miR-193b in 50 GC cases and found that miR-193b was significantly reduced in GC tissues compared with the adjacent normal gastric tissues. Moreover, lower-level of miR-193b was also associated with a more aggressive GC phenotype. We further demonstrated that miR-193b can inhibit the proliferation, migration and invasion of HGC-27 and MGC-803 GC cells. Further mechanism study indicated that CCND1 was a direct target of miR-193b in GC. Overexpression of miR-193b inhibited the expression of CCND1, and knock-down of CCND1 inhibited the proliferation of GC cells, suggesting that miR-193b exerted its anti-tumorigenic role in GC cells through targeting CCND1 gene. [ABSTRACT FROM AUTHOR]