microRNAs In Gastric Cancer Research Articles

The cross talk between long, non-coding RNAs and microRNAs in gastric cancer.

Gastric cancer is one of the most common malignant diseases and remains the second leading cause of cancer-related mortality worldwide. Although great effort has been made during the past decades to facilitate the early detection and treatment of gastric cancer, the prognosis is not yet satisfactory and the underlying molecular mechanisms of gastric cancer pathogenesis are not fully understood. Meanwhile, non-coding RNAs have been established as key players in regulating various biological and pathological processes, such as cell-cycle progression, chromatin remodeling, gene transcription, and posttranscriptional processing. Furthermore, numerous studies have also revealed a complicated interplay among different species of non-coding RNAs; therefore, the cross-regulation between long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) has begun to emerge. This lncRNA-miRNA cross talk, which has attracted increasing attention in recent years, is involved in a great number of human diseases including gastric cancer. In this review, we summarize the latest research progress of the interactions between lncRNAs and miRNAs, highlighting their influences on the development and progression of gastric cancer to provide novel approaches for cancer diagnosis and treatment.

PRL-3 promotes gastric cancer migration and invasion through a NF-κB-HIF-1α-miR-210 axis.

Phosphatase of regenerating liver-3 (PRL-3) has been implicated in controlling cancer cell invasiveness. Deregulated expression of PRL-3 is involved in cancer progression and predicts poor overall survival. Recent studies have revealed critical roles for microRNAs in various cellular processes, including tumorigenic development. In this study, we aimed to explore the linkage between PRL-3 and microRNAs in gastric cancer. We found that PRL-3 transcript levels were positively correlated with miR-210 levels in gastric cancer tissues. In gastric cancer cells, PRL-3 upregulated miR-210 expression in a HIF-1α-dependent fashion under normoxia and hypoxia. In addition, PRL-3 activated NF-κB signaling and promoted HIF-1α expression through modulating phosphorylation of p65. NF-κB signaling, HIF-1α, and miR-210 partially contributed to PRL-3-induced migration and invasion. Furthermore, the levels of PRL-3, HIF-1α, and miR-210 transcripts inversely affected the overall survival of gastric cancer patients. Our work identified the existence of a PRL-3-NF-κB-HIF-1α-miR-210 axis, thus providing new insight into the role of PRL-3 in promoting gastric cancer invasiveness. PRL-3 regulates microRNA in gastric cancer. PRL-3 elevates hsa-miR-210 by upregulating HIF-1α. PRL-3 activates a NF-κB-HIF-1α-miR-210 axis by enhancing the phosphorylation of p65. PRL-3 promotes cell migration and invasion via the NF-κB-HIF-1α-miR-210 axis. High levels of PRL-3 and miR-210 are related with poor OS in gastric cancer.

Epigenetically silenced microRNAs in gastric cancer: Functional analysis and identification of their target genes.

microRNAs (miRNAs), which are small non‑coding RNA molecules, can participate in diverse biological functions and act as oncogenes or tumor suppressors by inhibiting target gene expression. The alteration of miRNA expression is observed in many types of human cancers and has been implicated in carcinogenesis. Since miRNAs have been known to be downregulated in most cancer types, there is growing evidence that several miRNAs are downregulated by DNA hypermethylation. Here, we determined that MIR219.2, MIR663b and MIR1237 were transcriptionally silenced by DNA hypermethylation in human gastric cancer cell lines. Moreover, we demonstrated the functional roles of these epigenetically silenced miRNAs by ectopically expressing them in gastric cancer cells, which caused the suppression of growth and proliferation. In addition, wound closure, cell migration, and invasion were significantly reduced in AGS cells following transfection with MIR219.2, MIR663b or MIR1237 mimics. Notably, epithelial-to-mesenchymal transition (EMT)-associated proteins were decreased in response to ectopic expression of these miRNAs, supporting the notion that these miRNAs have a tumor-suppressive effect in gastric cancer. We finally predicted the targets of these miRNAs and identified several candidate genes, the expression levels of which were significantly downregulated by ectopic expression of MIR219.2, MIR663b or MIR1237 mimics in the gastric cancer cell lines. Our study provides strong evidence that these miRNAs are transcriptionally regulated by DNA methylation in gastric cancer and have tumor-suppressive roles by decreasing the mesenchymal traits in cancer as well as by targeting cancer-associated genes.

Role of microRNAs in gastric cancer.

Although gastric cancer (GC) is one of the leading causes of cancer-related death, major therapeutic advances have not been made, and patients with GC still face poor outcomes. The prognosis of GC also remains poor because the molecular mechanisms of GC progression are incompletely understood. MicroRNAs (miRNAs) are noncoding RNAs that are associated with gastric carcinogenesis. Studies investigating the regulation of gene expression by miRNAs have made considerable progress in recent years, and abnormalities in miRNA expression have been shown to be associated with the occurrence and progression of GC. miRNAs contribute to gastric carcinogenesis by altering the expression of oncogenes and tumor suppressors, affecting cell proliferation, apoptosis, motility, and invasion. Moreover, a number of miRNAs have been shown to be associated with tumor type, tumor stage, and patient survival and therefore may be developed as novel diagnostic or prognostic markers. In this review, we discuss the involvement of miRNAs in GC and the mechanisms through which they regulate gene expression and biological functions. Then, we review recent research on the involvement of miRNAs in GC prognosis, their potential use in chemotherapy, and their effects on Helicobacter pylori infections in GC. A greater understanding of the roles of miRNAs in gastric carcinogenesis could provide insights into the mechanisms of tumor development and could help to identify novel therapeutic targets.

Epigenetic Regulation of microRNAs in Gastric Cancer

Gastric cancer is one of the most common cancers and accounts for a large proportion of cancer-related deaths in the world, while the pathogenesis of it is still not clear. Epigenetic changes have been found to participate in the development and progression of gastric cancer. Epigenetic changes involve methylation of cytosines in DNA, modifications of histone, chromatin remodeling, and alterations in the expression of microRNAs. MicroRNAs, a family of small non-coding RNAs, have been demonstrated to participate in many fundamental biological processes including the carcinogenesis of gastric cancer. Previous studies have shown that the downregulation of microRNAs are often caused by the methylation in the CpG islands of microRNA promoters. Here, we have summarized the functions and molecular mechanisms of gastric cancer related methylated microRNAs in gastric carcinogenesis. We further envisage the clinical application of microRNA methylation in the early diagnosis, treatment and prognosis assessment of gastric cancer.

MicroRNAs in Gastric Cancer: From Benchtop to Bedside

Gastric carcinogenesis represents a stepwise progression from chronic inflammation to invasive adenocarcinomas and distant metastasis. It has been widely accepted that these pathologic changes are contributed by aberrant activation or inactivation of protein-coding proto-oncogenes and tumor suppressor genes. However, recent discoveries in microRNA research have reshaped our understanding of the role of non-protein-coding genes in carcinogenesis. MicroRNAs (miRNAs) are a family of 18-25-nucleotide small RNAs that negatively regulate gene expression at the post-transcriptional level during various crucial cell processes such as apoptosis, differentiation and development. Changes in miRNA expression profiles have been observed in a variety of human tumors, including gastric cancer. Further studies demonstrated that miRNAs may function as tumor suppressors and oncogenes. These findings have shown great potential of miRNAs as a novel class of therapeutic targets. In addition, it was found that some miRNAs were directly involved in patients with gastric cancer, including prognosis prediction, treatment selection, and in the search for unknown primary sites. MiRNAs have also been proved to be detectable in serum and plasma. In this review, we summarize the function of miRNAs in gastric cancer. Furthermore, we describe the pathophysiological roles of these miRNAs and their clinical potential as diagnostic biomarkers and therapeutic targets.

Progression of microRNA in gastric cancer

Recently,many studies find that microRNA plays a key role in the development,diagnosis,treatment and prevention of gastric cancer.It is confirmed that miR-451 can be used as a useful biomarker for the screening of gastric cancer.Studies also show that miR-203 and miR-21 may become diagnostic markers of gastric cancer.MicroRNA can play the role of oncogenes,and also can play the role of tumor suppressor gene,such as miR-141 plays the role of tumor suppressor gene through inhibition of the positive fibroblast growth factor receptor 2 gene expression. Key words: Gastric neoplasms; MicroRNAs

Oncogenic miR-544 is an Important Molecular Target in Gastric Cancer

MicroRNAs (miRNAs) and promoter hypermethylation are vital epigenetic mechanisms for transcriptional inactivation of tumor suppressor. IRX1 is a newly identified tumor suppressor gene and hypermethylation involves the decreased expression in gastric cancer. However, the microRNA regulatory mechanism on IRX1 expression is still unclear. In this study, we report an IRX1-targeting miRNA-544, which directly targets 3'-UTR of IRX1 gene by luciferase reporter assay. miR-544 suppresses the protein expression of IRX1 gene by Western blot and immunocytochemistry. Ectopic expression of miR-544 promotes cell proliferation and cell cycle progression significantly in vitro on gastric cancer cells. The study suggests that miR-544 is an oncogenic microRNA in gastric cancer. Over expression of miR-544 contributes to the inactivation and low-expression of IRX1 in gastric cancer. These findings are helpful for clarifying the molecular mechanisms involved in gastric carcinogenesis and indicate that miR-544 is a key regulator in switching cell cycle on or off. miR-544 may be a potential molecular target in miRNA-based strategy on gastric cancer.

Clinical application of microRNA in gastric cancer in Eastern Asian area

Recent research has shown that microRNA (miRNA), which is involved in almost every step of gastric carcinogenesis, has broad prospective application in diagnosis and therapy of gastric carcinoma. Eastern Asia (South Korea, Japan and China) has the highest incidence of gastric cancer in the world. There were 988,000 new cases of gastric cancer worldwide and 736,000 deaths in 2008. Approximately 60% of the cases of gastric cancer are found in East Asia (mainly China). We herein provide a brief review of the clinical applications of miRNA, which include the following aspects: (1) miRNA may serve as a potential new generation of tumor markers; (2) a complete miRNA expression profile is highly specific, can reflect the evolutionary lineage and differentiation of tumors, and be used to carry out diversity analysis; (3) detecting specific miRNA expression in peripheral blood will become a new method for diagnosis of gastric cancer; (4) miRNA can predict prognosis of gastric cancer; (5) miRNA has predictive value in determining chemotherapy and radiotherapy resistance; and (6) miRNA could be a type of innovative drug. Finally, we focus on assessing the value of miRNA from laboratory to clinical application and the challenges it faces in East Asia.

Aberrant expression of microRNAs in gastric cancer and biological significance of miR-574-3p

The discovery of microRNAs (miRNAs) provides a new and powerful tool for studying the mechanisms, diagnosis and treatments of cancer. In this study, we employed AFFX miRNA expression chips to search for miRNAs that may be aberrantly expressed in gastric cancer tissues and to investigate the potential roles that miRNAs may play in the development and progression of gastric cancer. 14 miRNAs were found to be down-regulated and 2 miRNAs up-regulated in gastric cancer tissues compared to the normal gastric tissues. Among the aberrantly expressed miRNAs, miR-574-3p was selected to further study its expression features and functional roles. Interestingly, the reduced expression of miR-574-3p occurred mainly in the early stages of gastric cancer or in cancers with high level of differentiation, suggesting that it can be used as a marker for a mild case of gastric cancer. Functional study revealed that cell proliferation, migration and invasion were significantly inhibited in miR-574-3p-transfected gastric cancer SGC7901 cells. Computational prediction and experimental validation suggest that Cullin2 may be one of the targets of miR-574-3p. Overall our study suggests that the aberrantly expressed miRNAs may play regulatory and functional roles in the development and progression of gastric cancer.

MicroRNA-7 functions as an anti-metastatic microRNA in gastric cancer by targeting insulin-like growth factor-1 receptor

Metastasis is a major clinical obstacle in the treatment of gastric cancer (GC) and it accounts for the majority of cancer-related mortality. MicroRNAs have recently emerged as regulators of metastasis by acting on multiple signaling pathways. In this study, we found that miR-7 is significantly downregulated in highly metastatic GC cell lines and metastatic tissues. Both gain-of-function and loss-of-function experiments showed that increased miR-7 expression significantly reduced GC cell migration and invasion, whereas decreased miR-7 expression dramatically enhanced cell migration and invasion. In vivo metastasis assays also demonstrated that overexpression of miR-7 markedly inhibited GC metastasis. Moreover, the insulin-like growth factor-1 receptor (IGF1R) oncogene, which is often mutated or amplified in human cancers and functions as an important regulator of cell growth and tumor invasion, was identified as a direct target of miR-7. Silencing of IGF1R using small interefering RNA (siRNA) recapitulated the anti-metastatic function of miR-7, whereas restoring the IGF1R expression attenuated the function of miR-7 in GC cells. Furthermore, we found that suppression of Snail by miR-7, through targeting IGF1R, increased E-cadherin expression and partially reversed the epithelial-mesenchymal transition (EMT). Finally, analyses of miR-7 and IGF1R levels in human primary GC with matched lymph node metastasis tissue arrays revealed that miR-7 is inversely correlated with IGF1R expression. The present study provides insight into the specific biological behavior of miR-7 in EMT and tumor metastasis. Targeting this novel miR-7/IGF1R/Snail axis would be helpful as a therapeutic approach to block GC metastasis.

Correlation of expression of microRNA miR-21 with prognostic characteristics in gastric cancer.

e14629 Background: MicroRNAs may play an important role in earlt stage gastric cancer. Methods: We studied the expression of MicroRNAs in gastric cancer to understand the expression characteristics of one of the key MicroRNAs miR-21 using 65 cases of early-stage gastric cancer identified from our cancer center records between October 2007 and March 2010. First, we used an MicroRNA array (miRCURY LNA Array) that contained 1,348 known probes and compared the expression profile of these MicroRNAs in six cases of gastric cancer specimen with their surrounding normal tissues. We then studied the expression of miR-21 and correlated it with the histologic characteristics of the 65 cases by RT-PCR. Results: The expression of seven MicroRNAs (miR-374b*, miRPlus-E1212, miR-338-5p, miR-297, miR-21, miR-135b, and miR-18a) was significantly up-regulated, while nine MicroRNAs (miR-29b-2*, miR-1260, miRPlus-E1241, miR-S1-5p, miR-148a, miR-29c, miR-647, miR-196b*, ebv-miR-BART5) significantly down-regulated. Because miR-21 was highly overexpressed in gastric cancer compared to its normal surrounding tissue, we next studied if the expression of miR-21 in sixty-five cases of gastric cancer was associated with clinical and histologic characteristics of early stage gastric cancer. We found that the increased expression of miR-21 was correlated with poorly differentiated histology (high grade), T3-4 stage and nodal involvement. The average level of miR-21 expression was two to five folds higher in the cases that are poorly differentiated, T3-4 stage, or with lymph node involvement compared to the cases that were well or moderately differentiated, T1-2 stage or with negative nodal involvement. The high-grade gastric cancers were associated with the highest level of miR-21 compared to the surrounding normal tissues. These results suggest that miR-21 is a potential biological marker indicative of the aggressiveness nature of this malignancy. Conclusions: Our results demonstrate that expression of several MicroRNAs may play important roles in the development and progression of gastric cancer and the increased expression of miR-21 is associated with poor prognostic characteristics.

Abstract 4141: The role of microRNA in gastric cancer

Abstract Objectives: To expore miRNA expression pattern in gastric cancer and investigate the role of miRNAs in the tumorigenesis of gastric cancer. Methods: We globally analyzed the miRNA expression profile in 9 gastric cancer cell lines and 6 normal gastric mucosa and the tumor tissues and its corespending adjacent normal tisuues of 30 patients through miRNA microarray. The differential expression of miRNAs from miRNA microarray were confirmed by qRT-PCR. Then, we extended our assay to sixty paired gastric cancer tissues and the relationship between miR-126 expression level and clinicopatholoic variables was explored. The specific miR-126 precursor or miR-126 expression vector were transfected into gastric cancer cell line SGC-7901 to up-regulate miR-126 expression and its biological effects on SGC-7901 cells were investigated. Finally, the target gene of miR-126 was predicted by bioimformatic method and validated by luciferase reportor system. Results: found that 17 miRNAs were up-regulated in gastric cancer cell lines and 146 miRNAs were down-regulated compared with normal gastric mucosa. Then we performed quantitative real-time PCR of 15 up-regulated miRNAs and 26 logRatio < –5.0 down-regulated miRNAs in gastric cancer cell lines and gastric cancer tissues for further analysis. The coincidence of microarray data and qPCR results was in an acceptable range and 15 miRNAs were finally selected. These candidate miRNAs were associated with gastric cancer clinicopathology in different degree. Meanwhile, high expression of hsa-miR-93 and hsa-miR-409-3p were found to predict poor survival (median, 16 months vs 40 months, LogRank p < 0.05). we show that miR-126 is significantly down-regulated in gastric cancer tissues and associated with clinicopathological features such as tumor size, lymph node metastasis, local invasion and TNM stage. Ectopic expression of miR-126 in SGC-7901 gastic cancer cells potently inhibits cell growth by inducing cell cycle arrest at G1 phase, migration and invasion in vitro and tumorigenicity in vivo. Mechanistically, we identify adaptor protein Crk as a target of miR-126. Taken together, our findings demonstrate miR-126 may function as a tumor suppressor in gastric cancer through regulation of genes such as Crk. Conclusions: These findings may suggest vital roles of miRNAs in huamn gastric cancer, and provide clues for understanding the molecular basis of miRNAs in various biological processes. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4141. doi:1538-7445.AM2012-4141

Abstract 2304: MicroRNA-7 functions as antimetastic microRNA in gastric cancer by targeting insulin-like growth factor 1 receptor

Abstract Metastasis is a major clinical obstacle in the treatment of gastric cancer (GC) and accounts for the majority of cancer-related mortality. MicroRNAs (miRNAs) have been recently emerged as regulators of metastasis through acting on multiple signaling pathways. In this study, we found that miR-7 is significantly down-regulated in high-metastatic GC cell lines and metastatic tissues. Both gain-of-function and loss-of-function studies showed that increased miR-7 expression significantly reduced migration and invasion of GC cells, while decreased miR-7 expression dramatically enhanced cell migration and invasion. In vivo metastasis assays also shown that overexpression of miR-7 remarkably inhibits GC metastasis. Moreover, the IGF1R oncogene, which is often mutated or amplified in human cancers and has been shown to function as an important regulator of cell growth and tumor invasion, was identified as a direct target of miR-7. RNA interference silencing of IGF1R recapitulated the antimetastic function of miR-7, whereas restoration of IGF1R expression attenuated the function of miR-7 in GC cells. Furthermore, we found that suppression of Snail by miR-7 through targeting IGF1R increased E-cadherin expression and partly reversed the epithelial-mesenchymal transition (EMT). Finally, analyses of the miR-7 and IGF1R level in human primary GC with matched lymph node metastasis tissue arrays revealed that miR-7 is inversely related to the increase of IGF1R expression. The present study provides an insight into the specific biological behavior of miR-7 in EMT and tumor metastasis. This novel miR-7/IGF1R/Snail axis would be helpful in the therapeutic application to block GC metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2304. doi:1538-7445.AM2012-2304

Abstract 2034: Tumor suppressive activity of Smad3 by regulation of microRNAs in gastric cancer

Abstract Loss of the tumor suppressive effect of transforming growth factor-β (TGF-β) has been commonly found at later stages in carcinogenic progression. It was recently found that Smad3 expression is lost in more than a third of cancers and the introduction of Smad3 into Smad3 null gastric cancer cell line restores TGF-β-mediated growth inhibitory and tumor suppressive activity. Interestingly, expression of Smad3 induced the expression of E-cadherin. Since there is accumulating evidence that microRNAs (miRNAs) regulate transcriptional repressors of E-cadherin such as ZEB1 and ZEB2, thus affecting the expression of E-cadherin, we aimed to compare miRNA profiles of Smad3-negative gastric cell line (SNU484-LPCX) and Smad3-overexpressed one (SNU484-Smad3). To investigate global changes of miRNA profiles associated with Smad3 restoration, we applied massively parallel sequencing (MPS) to miRNA profiling. Using this approach, we identified more than 150 known miRNAs, and at least 10 miRNAs including miR200 show statistical significance in expression between two cell lines. To further confirm these findings, we applied qRT-PCR analysis of selected miRNAs and mRNAs. Using Smad3 specific siRNAs, we also proved that Smad3 is involved in the E-cadherin expression through the regulation of specific miRNAs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2034.

MicroRNA profiling of human gastric cancer

MicroRNAs are a group of small non-coding RNAs that modulate gene expression. The de-regulation of microRNA expression has been found in several types of cancer. To study the role of microRNAs in gastric cancer (GC), we analyzed the expression profile of 847 microRNAs in GC from Chinese patients. Total RNA was used for hybridization on the miRCURY LNA Array (v. 11.0), which contains probes specific for 847 human microRNAs. The results from the miRNA microarray analysis were validated by real-time RT-PCR. A total of 24 miRNAs with a more than 2-fold change were differentially expressed between normal gastric tissue and GC. Of these, 22 miRNAs (miR-223, miR-106b, miR-147, miR-34a, miR-130b*, miR-106a, miR-18a, miR-17, miR-98, miR-616*, miR-181a-2*, miR-185, miR-1259, miR-601, miR-196a*, miR-221*, miR-302f, miR-340*, miR-337-3p, miR-520c-3p, miR-575 and miR-138) were significantly up-regulated in GC (P<0.05), whereas only miR-638 and miR-378 were significantly down-regulated in GC (P<0.05) compared to normal gastric tissue. The expression of miR-185 and miR-638, as measured by miRNA microarray analysis, was in agreement with the expression level of these microRNAs found by real-time RT-PCR in the same samples. Our results show that microRNAs are de-regulated in GC, suggesting the involvement of these genes in the development and progression of gastric cancer.