SUMOylation of XRCC1 activated by poly (ADP-ribosyl)ation regulates DNA repair.

XRCC1 is an essential scaffold protein for base excision repair (BER) and helps to maintain genomic stability. XRCC1 has been indicated as a substrate for small ubiquitin-like modifier modification (SUMOylation); however, how XRCC1 SUMOylation is regulated in cells and how SUMOylated XRCC1 regulates BER activity are not well understood. Here, we show that SUMOylation of XRCC1 is regulated in cells under methyl-methanesulfonate (MMS) treatment and facilitates BER. Poly(ADP-ribose) polymerase 1 (PARP1) is activated by MMS immediately and synthesizes poly(ADP-ribose) (PAR), which in turn promotes recruitment of SUMO E3 TOPORS to XRCC1 and facilitates XRCC1 SUMOylation. A SUMOylation-defective mutant of XRCC1 had lower binding activity for DNA polymerase beta (POLB) and was linked to a lower capacity for repair of MMS-induced DNA damages. Our study therefore identified a pathway in which DNA damage-induced poly(ADP-ribosyl)ation (PARylation) promotes SUMOylation of XRCC1, which leads to more efficient recruitment of POLB to complete BER.

FGFR2 regulates Mre11 expression and double-strand break repair via the MEK-ERK-POU1F1 pathway in breast tumorigenesis.

The association between breast cancer risk and genetic variants of fibroblast growth factor receptor 2 (FGFR2) has been identified and repeatedly confirmed; however, the mechanism underlying FGFR2 in breast tumorigenesis remains obscure. Given that breast tumorigenesis is particularly related to DNA double-strand-break-repair (DSBR), we examined the hypothesis that FGFR2 is involved in DSBR. Our results show that expression of Mre11, a vital exonuclease in DSBR, is downregulated by FGFR2, which is further linked to decreased DSBR. Analysis of the Mre11 promoter revealed that POU1F1 mediates FGFR2-induced Mre11 downregulation. Furthermore, ERK, downstream of FGFR2, directly interacts with and phosphorylates POU1F1, increasing POU1F1 binding capacity to the Mre11 promoter and repressing Mre11 expression, which consequently affects DSBR and sensitizes breast cancer cells to chemotherapeutic treatments. The importance of the FGFR2-Mre11-DSBR link in cancer progression is suggested by the finding that genotypes of FGFR2 and Mre11 are associated with survival of breast cancer patients and that FGFR2 expression correlates with cancer prognosis specifically in patients receiving chemotherapy. This study yields important insight into the role of FGFR2 in breast tumorigenesis and may facilitate development of a useful therapeutic approach for breast cancer.

A novel estrogen receptor-microRNA 190a-PAR-1-pathway regulates breast cancer progression, a finding initially suggested by genome-wide analysis of loci associated with lymph-node metastasis.

To identify microRNAs that are important in regulating breast cancer progression, the present study used data for the 199 961 single-nucleotide polymorphisms (SNPs) in 837 breast cancer patients genotyped in a recent genome-wide association study to identify loci associated with lymph node metastasis (LNM). SNPs tagging the 15q22.2 locus showed a significant association with LNM and miR-190a was found to be the only microRNA in this region. The role of miR-190a in LNM was supported by the findings that increased miR-190a expression inhibited cell migration and invasiveness and that the target of miR-190a was protease-activated-receptor 1 (PAR-1), which is a metastasis promoting protein in several cancers. In addition, the promoter region of miR-190a was defined and found to contain half of an estrogen response element, suggesting that miR-190a is regulated by estrogen receptor (ER) signaling. This was confirmed by the findings that miR-190a expression was activated by 17ß-estradiol and that ERα bound directly to this promoter. The importance of this ERα-miR190a-PAR-1 link in breast tumorigenesis is suggested by the findings of (i) an association between genetic polymorphism of the miR-190a-containing region and LNM that is modified by SNPs of PAR-1 and is particularly significant in ERα-positive patients and (ii) a combined effect of ERα and miR-190a expression on tumor grade/cancer stage. More importantly, the level of miR-190a expression in primary breast carcinomas correlated with overall survival. These findings suggest a novel pathway in which ERα signaling regulates miR-190a expression, causing inhibition of PAR-1 expression, correlated with inhibition of cancer metastasis.

Initiation of the ATM-Chk2 DNA damage response through the base excision repair pathway.

The DNA damage response (DDR) is activated by various genotoxic stresses. Base lesions, which are structurally simple and predominantly fixed by base excision repair (BER), can trigger the ataxia telangiectasia mutated (ATM)-checkpoint kinase 2 (Chk2) pathway, a DDR component. How these lesions trigger DDR remains unclear. Here we show that, for alkylation damage, methylpurine-DNA glycosylase (MPG) and apurinic/apyrimidinic endonuclease 1, both of which function early in BER, are required for ATM-Chk2-dependent DDR. In addition, other DNA glycosylases, including uracil-DNA glycosylase and 8-oxoguanine glycosylase, which are involved in repairing deaminated bases and oxidative damage, also induced DDR. The early steps of BER therefore play a vital role in modulating the ATM-Chk2 DDR in response to base lesions, facilitating downstream BER processing for repair, in which the formation of a single-strand break was shown to play a critical role. Moreover, MPG knockdown rescued cell lethality, its overexpression led to cell death triggered by DNA damage and, more interestingly, higher MPG expression in breast and ovarian cancers corresponded with a greater probability of relapse-free survival after chemotherapy, underscoring the importance of glycosylase-dependent DDR. This study highlights the crosstalk between BER and DDR that contributes to maintaining genomic integrity and may have clinical applications in cancer therapy.

Functional variants at the 21q22.3 locus involved in breast cancer progression identified by screening of genome-wide estrogen response elements.

INTRODUCTION: Estrogen forms a complex with the estrogen receptor (ER) that binds to estrogen response elements (EREs) in the regulatory region of estrogen-responsive genes and regulates their transcription. Sequence variants in the regulatory regions have the potential to affect the transcription factor-regulatory sequence interaction, resulting in altered expression of target genes. This study explored the association between single-nucleotide polymorphisms (SNPs) within the ERE-associated sequences and breast cancer progression. METHODS: The ERE-associated sequences throughout the whole genome that have been demonstrated to bind ERα in vivo were blasted against online information from SNP data sets and 54 SNPs located adjacent to estrogen-responsive genes were selected for genotyping in two independent cohorts of breast cancer patients: 779 patients in the initial screening stage and another 888 in the validation stage. Deaths due to breast cancer or recurrence of breast cancer were defined as the respective events of interest, and the hazard ratios of individual SNPs were estimated based on the Cox proportional hazards model. Furthermore, functional assays were performed, and information from publicly available genomic data and bioinformatics platforms were used to provide additional evidence for the associations identified in the association analyses. RESULTS: The SNPs at 21q22.3 ERE were significantly associated with overall survival and disease-free survival of patients. Furthermore, these 21q22.3 SNPs (rs2839494 and rs1078272) could affect the binding of this ERE-associated sequence to ERα or Rad21 (an ERα coactivator), respectively, which resulted in a difference in ERα-activated expression of the reporter gene. CONCLUSION: These findings support the idea that functional variants in the ERα-regulating sequence at 21q22.3 are important in determining breast cancer progression.

Co-modulated behavior and effects of differentially expressed miRNA in colorectal cancer.

BACKGROUND: MicroRNAs (miRNAs) are short noncoding RNAs (approximately 22 nucleotides in length) that play important roles in colorectal cancer (CRC) progression through silencing gene expression. Numerous dysregulated miRNAs simultaneously participate in the process of colon cancer development. However, the detailed mechanisms and biological functions of co-expressed miRNA in colorectal carcinogenesis have yet to be fully elucidated. RESULTS: The objective of this study was to identify the dysfunctional miRNAs and their target mRNAs using a wet-lab experimental and dry-lab bioinformatics approach. The differentially expressed miRNA candidates were identified from 2 miRNA profiles, and were confirmed in CRC clinical samples using reported target genes of dysfunctional miRNAs to perform functional pathway enrichment analysis. Potential target gene candidates were predicted by an in silico search, and their expression levels between normal and colorectal tumor tissues were further analyzed using real-time polymerase chain reaction (RT-PCR). CONCLUSION: Fifteen dysfunctional miRNAs were engaged in metastasis-associated pathways through comodulating 7 target genes, which were identified by using a multi-step approach. The roles of these candidate genes are worth further exploration in the progression of colon cancer, and could potentially be targets in future therapy.

Aberrant expression of miR-196a in gastric cancers and correlation with recurrence.

MicroRNAs (miRNAs) are short noncoding RNAs (~22 nt) that play important roles in the pathogenesis of human diseases by negatively regulating gene expression. Here, we examined the relationship between miR-196a and gastric cancer.By the analysis of 72 gastric cancer samples, we found that the expression level of miR-196a microRNA significantly increased in primary gastric cancer tissues versus adjacent normal tissues. In addition, extracellular miR-196a detected in conditioned medium was strongly correlated with its cellular expression status and increased circulating miR-196a in patient serum was associated with gastric cancer disease status and relapse. Furthermore, ectopic expression of miR-196a microRNA promoted the epithelial-mesenchymal transition and migration/invasion capabilities of transfected cells, suggesting its oncogenic potential in gastric cancer progression. Altogether, our data demonstrate that miR-196a exerts an oncogenic role in gastric cancer and miR-196a may be a novel biomarker for detecting gastric cancer and for monitoring disease recurrence.

Transcriptional regulation of miR-196b by ETS2 in gastric cancer cells.

E26 transformation-specific sequence (ETS)-2 is a transcriptional modulator located on chromosome 21, alterations in its expression have been implicated with a reduced incidence of solid tumors in Down syndrome patients. MicroRNAs (miRNAs) are thought to participate in diverse biological functions; however, the regulation of miRNAs is not well characterized. Recently, we reported that miR-196b is highly expressed in gastric cancers. Herein, we demonstrate that miR-196b expression was significantly repressed by ETS2 during gastric cancer oncogenesis. We demonstrate that knockdown of endogenous ETS2 expression increases miR-196b expression. A genomic region between -751 and -824 bp upstream of the miR-196b transcriptional start site was found to be critical for the repression activity. This putative regulatory promoter region contains three potential ETS2-binding motifs. Mutations within the ETS2 binding sites blocked the repression activity of ETS2. Furthermore, knockdown of ETS2 or overexpression of miR-196b significantly induced migration and invasion in gastric cancer cells. In addition, alterations in ETS2 and miR-196b expression in gastric cancer cell lines affected the expression of epithelial-mesenchymal transition-related genes. The levels of vimentin, matrix metalloproteinase (MMP)-2 and MMP9 were drastically induced, but levels of E-cadherin were decreased in shETS2- or miR-196b-transfected cells. Our data indicate that ETS2 plays a key role in controlling the expression of miR-196b, and miR-196b may mediate the tumor suppressor effects of ETS2. We demonstrated that miR-196b was transcriptionally regulated by ETS2 and there was an inverse expression profile between miR-196b and ETS2 in clinical samples. This finding could be beneficial for the development of effective cancer diagnostic and alternative therapeutic strategies.

Comprehensive analysis of microRNAs in breast cancer.

BACKGROUND: MicroRNAs (miRNAs) are short noncoding RNAs (approximately 22 nucleotides in length) that play important roles in breast cancer progression by downregulating gene expression. The detailed mechanisms and biological functions of miRNA molecules in breast carcinogenesis have yet to be fully elucidated. This study used bioinformatics and experimental approaches to conduct detailed analysis of the dysregulated miRNAs, arm selection preferences, 3' end modifications, and position shifts in isoforms of miRNAs (isomiRs) in breast cancer. METHODS: Next-generation sequencing (NGS) data on breast cancer was obtained from the NCBI Sequence Read Archive (SRA). The miRNA expression profiles and isomiRs in normal breast and breast tumor tissues were determined by mapping the clean reads back to human miRNAs. Differences in miRNA expression and pre-miRNA 5p/3p arm usage between normal and breast tumor tissues were further investigated using stem-loop reverse transcription and real-time polymerase chain reaction. RESULTS: The analysis identified and confirmed the aberrant expression of 22 miRNAs in breast cancer. Results from pathway enrichment analysis further indicated that the aberrantly expressed miRNAs play important roles in breast carcinogenesis by regulating the mitogen-activated protein kinase (MAPK) signaling pathway. Data also indicated that the position shifts in isomiRs and 3' end modifications were consistent in breast tumor and adjacent normal tissues, and that 5p/3p arm usage of some miRNAs displayed significant preferences in breast cancer. CONCLUSIONS: Expression pattern and arm selection of miRNAs are significantly varied in breast cancers through analyzing NGS data and experimental approach. These miRNA candidates have high potential to play critical roles in the progression of breast cancer and could potentially provide as targets for future therapy.

Interrogation of rabbit miRNAs and their isomiRs.

Rabbit (Oryctolagus cuniculus) is the only lagomorph animal of which the genome has been sequenced. Establishing a rabbit miRNA resource will benefit subsequent functional genomic studies in mammals. We have generated small RNA sequence reads with SOLiD and Solexa platforms to identify rabbit miRNAs, where we identified 464 pre-miRNAs and 886 mature miRNAs. The brain and heart miRNA libraries were used for further in-depth analysis of isomiR distributions. There are several intriguing findings. First, several rabbit pre-miRNAs form highly conserved clusters. Second, there is a preference in selecting one strand as mature miRNA, resulting in an arm selection preference. Third, we analyzed the isomiR expression and validated the expression of isomiR types in different rabbit tissues. Moreover, we further performed additional small RNA libraries and defined miRNAs differentially expressed between brain and heart. We conclude also that isomiR distribution profiles could vary between brain and heart tissues.

Genetic variation in the genome-wide predicted estrogen response element-related sequences is associated with breast cancer development.

INTRODUCTION: Estrogen forms a complex with the estrogen receptor (ER) that binds to estrogen response elements (EREs) in the promoter region of estrogen-responsive genes, regulates their transcription, and consequently mediates physiological or tumorigenic effects. Thus, sequence variants in EREs have the potential to affect the estrogen-ER-ERE interaction. In this study, we examined the hypothesis that genetic variations of EREs are associated with breast cancer development. METHODS: This case-control study involved 815 patients of Asian descent with incident breast cancer and 821 healthy female controls. A total of 13,737 ERE sites in the whole genome predicted by a genome-wide computational algorithm were blasted with single-nucleotide polymorphism (SNP) sequences. Twenty-one SNPs located within 2,000 bp upstream or within introns 1 and 2 of putative genes and with a minor allele frequency greater than 5% were identified and genotyped. Frequencies of SNPs were compared between cases and controls to identify SNPs associated with cancer susceptibility. RESULTS: A significant combined effect of rs12539530, an ERE SNP in intron 2 of NRCAM which codes for a cell adhesion molecule, and SNPs of ESR1, the gene coding for ER, on breast cancer risk was found. Interestingly, this combined effect was more significant in women who had experienced a longer period of lifetime estrogen exposure, supporting a hormonal etiology of this SNP in breast tumorigenesis. CONCLUSIONS: Our findings provide support for a role of genetic variation in ERE-ESR1 in determining susceptibility of breast cancer development.

Epigenetic regulation of miR-34b and miR-129 expression in gastric cancer.

MicroRNAs (miRNAs) are small noncoding RNAs that play fundamental roles in diverse biological and pathological processes by targeting the expression of specific genes. Here, we identified 38 methylation-associated miRNAs, the expression of which could be epigenetically restored by cotreatment with 5-aza-2'-deoxycytidine and trichostatin A. Among these 38 miRNAs, we further analyzed miR-34b, miR-127-3p, miR-129-3p and miR-409 because CpG islands are predicted adjacent to them. The methylation-silenced expression of these miRNAs could be reactivated in gastric cancer cells by treatment with demethylating drugs in a time-dependent manner. Analysis of the methylation status of these miRNAs showed that the upstream CpG-rich regions of mir-34b and mir-129-2 are frequently methylated in gastric cancer tissues compared to adjacent normal tissues, and their methylation status correlated inversely with their expression patterns. The expression of miR-34b and miR-129-3p was downregulated by DNA hypermethylation in primary gastric cancers, and the low expression was associated with poor clinicopathological features. In summary, our study shows that tumor-specific methylation silences miR-34b and miR-129 in gastric cancer cells.

Identification of homologous microRNAs in 56 animal genomes.

MicroRNAs (miRNAs) are endogenous non-protein-coding RNAs of approximately 22 nucleotides. Thousands of miRNA genes have been identified (computationally and/or experimentally) in a variety of organisms, which suggests that miRNA genes have been widely shared and distributed among species. Here, we used unique miRNA sequence patterns to scan the genome sequences of 56 bilaterian animal species for locating candidate miRNAs first. The regions centered surrounding these candidate miRNAs were then extracted for folding and calculating the features of their secondary structure. Using a support vector machine (SVM) as a classifier combined with these features, we identified an additional 13,091 orthologous or paralogous candidate pre-miRNAs, as well as their corresponding candidate mature miRNAs. Stem-loop RT-PCR and deep sequencing methods were used to experimentally validate the prediction results in human, medaka and rabbit. Our prediction pipeline allows the rapid and effective discovery of homologous miRNAs in a large number of genomes.

Epigenetic regulation of miR-196b expression in gastric cancer.

MicroRNAs (miRNAs) are short noncoding RNAs that play important roles in cellular processes and disease pathogenesis via the control of specific targeted gene expression. The miR-196s miRNA is encoded at three paralogous loci in three HOX clusters and acts as an oncogenic miRNA in cancer progression. Recent studies have demonstrated that the expression of miR-196b increases cell proliferation and survival in leukemic cells. Here, we used a sequential methylation analysis to reveal that the methylation status correlated well with miR-196b expression in different cell lines. Treatment with the demethylating drug 5-Aza-dC reactivated miR-196b transcription in methylation-silenced cells. Using in vitro methylation approach, we further provide evidences that promoter hypermethylation represses miR-196b transcriptional activation tightly in human cancer cell lines. We also demonstrate that the expression of miR-196b is significantly elevated in gastric cancer and that hypomethylation status of miR-196b CpG islands frequently is observed in primary gastric tumors. Our results provide important information on miR-196s regulation and demonstrate that abnormal DNA hypomethylation induces overexpression of miR-196b in gastric cancer.

Discovery and characterization of medaka miRNA genes by next generation sequencing platform.

BACKGROUND: MicroRNAs (miRNAs) are endogenous non-protein-coding RNA genes which exist in a wide variety of organisms, including animals, plants, virus and even unicellular organisms. Medaka (Oryzias latipes) is a useful model organism among vertebrate animals. However, no medaka miRNAs have been investigated systematically. It is beneficial to conduct a genome-wide miRNA discovery study using the next generation sequencing (NGS) technology, which has emerged as a powerful sequencing tool for high-throughput analysis. RESULTS: In this study, we adopted ABI SOLiD platform to generate small RNA sequence reads from medaka tissues, followed by mapping these sequence reads back to medaka genome. The mapped genomic loci were considered as candidate miRNAs and further processed by a support vector machine (SVM) classifier. As result, we identified 599 novel medaka pre-miRNAs, many of which were found to encode more than one isomiRs. Besides, additional minor miRNAs (also called miRNA star) can be also detected with the improvement of sequencing depth. These quantifiable isomiRs and minor miRNAs enable us to further characterize medaka miRNA genes in many aspects. First of all, many medaka candidate pre-miRNAs position close to each other, forming many miRNA clusters, some of which are also conserved across other vertebrate animals. Secondly, during miRNA maturation, there is an arm selection preference of mature miRNAs within precursors. We observed the differences on arm selection preference between our candidate pre-miRNAs and their orthologous ones. We classified these differences into three categories based on the distribution of NGS reads. Finally, we also investigated the relationship between conservation status and expression level of miRNA genes. We concluded that the evolutionally conserved miRNAs were usually the most abundant ones. CONCLUSIONS: Medaka is a widely used model animal and usually involved in many biomedical studies, including the ones on development biology. Identifying and characterizing medaka miRNA genes would benefit the studies using medaka as a model organism.

Association studies of up to 1.2 million individuals yield new insights into the genetic etiology of tobacco and alcohol use.

Tobacco and alcohol use are leading causes of mortality that influence risk for many complex diseases and disorders1. They are heritable2,3 and etiologically related4,5 behaviors that have been resistant to gene discovery efforts6-11. In sample sizes up to 1.2 million individuals, we discovered 566 genetic variants in 406 loci associated with multiple stages of tobacco use (initiation, cessation, and heaviness) as well as alcohol use, with 150 loci evidencing pleiotropic association. Smoking phenotypes were positively genetically correlated with many health conditions, whereas alcohol use was negatively correlated with these conditions, such that increased genetic risk for alcohol use is associated with lower disease risk. We report evidence for the involvement of many systems in tobacco and alcohol use, including genes involved in nicotinic, dopaminergic, and glutamatergic neurotransmission. The results provide a solid starting point to evaluate the effects of these loci in model organisms and more precise substance use measures.

B-Myb Induces APOBEC3B Expression Leading to Somatic Mutation in Multiple Cancers.

The key signature of cancer genomes is the accumulation of DNA mutations, the most abundant of which is the cytosine-to-thymine (C-to-T) transition that results from cytosine deamination. Analysis of The Cancer Genome Atlas (TCGA) database has demonstrated that this transition is caused mainly by upregulation of the cytosine deaminase APOBEC3B (A3B), but the mechanism has not been completely characterized. We found that B-Myb (encoded by MYBL2) binds the A3B promoter, causing transactivation, and this is responsible for the C-to-T transitions and DNA hypermutation in breast cancer cells. Analysis of TCGA database yielded similar results, supporting that MYBL2 and A3B are upregulated and putatively promote C-to-T transitions in multiple cancer types. Moreover, blockade of EGF receptor with afatinib attenuated B-Myb-A3B signaling, suggesting a clinically relevant means of suppressing mutagenesis. Our results suggest that B-Myb-A3B contributes to DNA damage and could be targeted by inhibiting EGF receptor.

An efficient strategy to identify early TPA-responsive genes during differentiation of HL-60 cells.

We have adopted a special experimental strategy to identify early responsive genes during 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced macrophage-like differentiation of human myeloid leukemia cells (HL-60). This was performed in cells that were synchronized by nocodazole and treated with TPA in the presence of a protein synthesis inhibitor, cycloheximide, to prevent activation of secondary targets and therefore increase the probability of early transcripts in total RNA pool. The expression alteration was analyzed by microarray and the selection criteria of candidate genes were adjusted by real-time PCR validation to increase its reliability. Finally, 56 genes were identified as early TPA-responsive genes in this multiscreening step approach. Furthermore, upregulation of three candidate genes (NFIL3, SKIL, and JMJD3) was shown to be dosage and time dependent with TPA treatment and was found to be directly regulated by TPA through PKC-dependent signaling. These results revealed that our screenings provide a useful and efficient approach to identify early TPA-responsive genes and these genes might involve the regulation of TPA-induced differentiation program of HL-60 cells as primary

Foxo3a-mediated overexpression of microRNA-622 suppresses tumor metastasis by repressing hypoxia-inducible factor-1α in ERK-responsive lung cancer.

Metastatic spread of cancer cells portends a poor prognosis and mortality for lung cancer patients. Hypoxia-inducible factor-1α (HIF-1α) enhances tumor cell motility by activating the epithelial-to-mesenchymal transition (EMT), which is considered a prerequisite for metastasis. Recent studies of microRNA involvement in cancer invasion and metastasis have highlighted the role of such RNAs in tumor development. However, little work has been done to identify tumor suppressor microRNAs that target HIF-1α to down-modulate the EMT and thereby counteract the aggressiveness and metastasis of lung cancer cells. Here, we identified the 3'-untranslated region of HIF-1α mRNA as a target of miR-622 and established that miR-622-mediated down-modulation of HIF-1α correlates with decreased levels of mesenchymal proteins, including Snail, ß-catenin, and vimentin. Functional analyses revealed that increased miR-622 expression inhibited lung cancer cell migration and invasion in vitro. miR-622 also inhibited the genesis of metastatic lung nodules as demonstrated in a lung cancer xenograft model in which nude mice were transplanted with A549 cells expressing miR-622. Mechanistic analyses showed that overexpression of EGF decreased the miR-622 level in A549 cells, and this reduction could be rescued by administrating U0126, an inhibitor of ERK. Moreover, miR-622 overexpression mediated by the transcription factor FOXO3a decreased the invasiveness of lung tumor cells by inhibiting HIF-1α via inactivation of ERK signaling in U0126-treated A549 cells. These findings highlight the pivotal role of the FOXO3a/miR-622 axis in inhibiting HIF-1α to interfere with tumor metastasis, and this information may contribute to development of novel therapeutic strategies for treating aggressive lung cancer.

Emerging role of microRNAs in modulating endothelin-1 expression in gastric cancer.

Endothelin-1 (ET-1) is a small 21-amino acid peptide that is known to exert diverse biological effects on a wide variety of tissues and cell types through its own receptors. The ET-1-ETRA axis is frequently dysfunctional in numerous types of carcinomas, and contributes to the promotion of cell growth and migration. microRNAs (miRNAs) are small non-coding RNAs that play a critical role in carcinogenesis through mRNA degradation or the translational inhibition of cancer-associated protein-coding genes. However, the role of ET-1 and the relationship between ET-1 and miRNAs in gastric cancer remain unknown. Results of the analysis of the database of The Cancer Genome Atlas (TCGA) revealed that ET-1 is significantly overexpressed in gastric cancer cells when compared with its expression in adjacent normal cells. Exogenous ET-1 significantly enhanced gastric cancer cell proliferation, implying that ET-1 plays an oncogenic role in gastric cancer carcinogenesis. Using a luciferase reporter assay we showed that 18 miRNA candidates had a significant silencing effect on ET-1 expression by up to 20% in HEK293T cells. Among them, 5 miRNAs (miR-1, miR-101, miR-125A, miR-144 and let-7c) were shown to be involved in ET-1 silencing through post-transcriptional modulation in gastric cancer. Our data also revealed that DNA hypermethylation contributes to the silenced miR-1 expression in gastric cancer cells. The ectopic expression of miR-1 significantly inhibited AGS cell proliferation by suppressing ET-1 expression. Overall, our study revealed that ET-1 overexpression may be due to DNA hypermethylation resulting in the silencing of miR-1 expression in gastric cancer cells. In addition, we identified several miRNAs as potential modulators for ET-1 in gastric cancer, which may be used as targets for gastric cancer therapy.