MicroRNA-21 promotes the cell proliferation, invasion and migration abilities in ovarian epithelial carcinomas through inhibiting the expression of PTEN protein

Ovarian cancer, especially epithelial ovarian cancer (EOC), which accounts for 90% of ovarian cancer, continues to be the leading cause of death among gynecological malignancies. However, the factors associated with its malignant biological behavior are still poorly understood. Accumulating evidence suggests that microRNAs (miRNAs), regulating diverse biological processes, may play an important role in tumorigenesis and development. miR-21 has been frequently observed to be aberrantly overexpressed in various tumors. Using real-time PCR, we confirmed that miR-21 was significantly overexpressed in human EOC tissues and cell lines. The overexpression of miR-21 correlated with histological differentiation, clinicopathological stage, and lymph node metastasis, and we showed that knockdown of miR-21 by an inhibitor caused a significant reduction in cell proliferation and decrease in cell migration and invasion abilities. Furthermore, we demonstrated that knockdown of miR-21 significantly increased the expression of PTEN, a known tumor suppressor in ovarian cancer. Collectively, our findings suggest miR-21 may be important in the initiation and progression of EOC as an oncomiR, likely through regulating PTEN.     

Chronic Helicobacter pylori infection induces an apoptosis-resistant phenotype associated with decreased expression of p27(kip1)

Helicobacter pylori infection is associated with the development of gastric cancer. In short-term coculture with AGS gastric cells, H. pylori inhibits cell cycle progression and induces dose-dependent apoptosis. Based on the concept that an imbalance between proliferation and apoptosis may contribute to the emergence of gastric cancer, we chronically exposed AGS cells to H. pylori as a model of chronic exposure in humans. The AGS derivatives selected by this process were stably resistant not only to H. pylori-induced apoptosis but also to apoptosis induced by other enteric bacteria and by several toxic agents including radiation and cancer chemotherapy. Like the parental AGS cells, the derivatives underwent G(1)/S-phase cell cycle inhibition in response to H. pylori. The AGS derivatives displayed a marked decrease in cellular levels of the cell cycle control protein p27(kip1). We found a similar decrease in epithelial cell p27(kip1) expression in gastric biopsy specimens from H. pylori-infected patients. These findings are consistent with observations that link decreases in the p27(kip1) level to increased susceptibility to cancer in mice with p27(kip1) deleted and to a poor prognosis of gastric cancer in humans. This is the first demonstration that bacterial infection can lead to apoptosis resistance and to cross-resistance to other inducers of apoptosis such as bacteria, chemotherapeutic agents, and radiation. The development of apoptosis resistance and downmodulation of p27(kip1) may contribute to the increased risk for gastric cancer observed in humans chronically exposed to H. pylori.     

MiR-211 inhibits cell proliferation and invasion of gastric cancer by down-regulating SOX4

Introduction: Previous studies have shown that the dysregulation of miRNAs are frequently associated with cancer progression. Deregulation of miR-211 has been observed in various types of human cancers. However, its biological function in gastric cancer (GC) is still unknown. Methods: The expression of miR-211 in GC was detected by using quantitative real-time PCR (qRT-PCR). The miR-211 mimics and inhibitor were designed and transfected into BGC-823 cells. Then, we explore the probable biological function of miR-211 in gastric cancer cell proliferation and invasion in vitro. A luciferase reporter assay and western blot were performed to confirm the target gene of miR-211. Results: MiR-211 was significantly down-regulated in GC. Over-expression of miR-211 inhibited gastric cancer cell proliferation and invasion in vitro, conversely, down-regulated expression of miR-211 promoted gastric cancer cell proliferation and invasion. In addition, the sex-determining region Y-related high mobility group box 4 (SOX4) is identified as a target of miR-211 in GC cells, and SOX4 expression levels was inversely correlated with miR-211. Furthermore, knockdown of Sox4 inhibited the proliferation and invasion in GC cells. Conclusion: miR-211 could inhibit GC cell proliferation and invasion partially by down-regulating SOX4. MiR-211 might be a potential therapeutic target for GC treatment in the future.     

miR-338-3p inhibits the proliferation and migration of gastric cancer cells by targeting ADAM17

Background: MicroRNAs (miRNA) have been documented playing a critical role in cancer progression. Although miR-338-3p has been implicated in several cancers, its role in gastric cancer is still unknown. The aim of our study was to investigate the role of miR-338-3p in gastric cancer progression. Methods: Expression levels of miR-338-3p in gastric cancer cell lines and tissues were determined by quantitative real-time PCR (qRT-PCR). The effect of miR-338-3p on proliferation was evaluated by MTT assay, cell migration and invasion were evaluated by transwell migration and invasion assays. Furthermore, luciferase reporter assay was conducted to confirm the target gene of miR-338-3p, and the results were validated in gastric cancer cells. Results: In the present study, we found that miR-338-3p was down-regulated in both gastric cancer cell lines and tissues. Enforced expression of miR-338-3p inhibited proliferation, migration and invasion of gastric cancer cells in vitro. Moreover, we identified A disintegrin and metalloproteinase 17 (ADAM17) gene as potential target of miR-338-3p. Importantly, ADAM17 rescued the miR-338-3p mediated inhibition of cell proliferation, migration and invasion. Conclusions: Our study suggested that miR-338-3p is significantly decreased in gastric cancer, and inhibits cell proliferation, migration and invasion partially via the downregulation of ADAM17. Thus, miR-338-3p may represent a potential therapeutic target for gastric cancer intervention.     

Circ-EIF4G3 promotes the development of gastric cancer by sponging miR-335

BackgroundCircular RNAs (circRNAs), a new group of endogenous non-coding RNAs, plays a crucial role in various types of carcinomas. However, there is still limited information on the involvement of circular RNAs in the setting of gastric cancer (GC). In the present study, we aimed to investigate circ-EIF4G3 status in clinical GC patient samples and explored the malignant biological behaviors.MaterialsThe expression of circ-EIF4G3 was determined by quantitative real time polymerase chain reaction (qRT-PCR). Microarray was performed to detect si-circ-EIF4G3 and unprocessed BGC-823 cells to find a cluster of differently expressed microRNAs (miRNAs) and bioinformatic tools including circinteractome, GO, NHGR1_GWAS, KEGG analyses were used in follow-up analysis. Luciferase reporter, RNA pull down and fluorescence in situ hybridization (FISH) assays were employed to explore the interaction between circ-EIF4G3 and miR-335. SiRNA-mediated knockdown of circ-EIF4G3, proliferation, migration and invasion in vitro were used to evaluate the function of circ-EIF4G3.ResultsAn increase level in the circ-EIF4G3 expression was associated with higher TNM stage and lymphatic metastasis. In vitro assays of the GC cell lines AGS and BGC-823 demonstrated that knockdown of circ-EIF4G3 inhibited cell proliferation, invasion and migration significantly. In addition, circ-EIF4G3 was identified as a sponge of miR-335, further promoting the proliferation, invasion and migration of GC cells.ConclusionOur study demonstrates that circ-EIF4G3 promotes the proliferation, invasion and migration of gastric cancer via sponging miR-335.     

Helicobacter pylori adherence to gastric epithelial cells: a role for non-adhesin virulence genes

Helicobacter pylori is a major aetiological agent in gastroduodenal disorders and adherence of the bacteria to the gastric mucosa is one of the initial stages of infection. Although a number of specific adhesins has been identified, other H. pylori virulence factors may play a role in adherence to gastric epithelial cells directly or through interaction with other adhesins. This study assessed the effect of 16 H. pylori virulence factors on the adherence of the bacteria to gastric AGS cells and on gastric epithelial cell cycle distribution. Defined isogenic H. pylori SS1 mutants were used. After co-incubation of gastric AGS cells and bacteria, adherence of H. pylori to AGS cells was visualised by immunofluorescence microscopy and quantified by flow cytometry. Cell cycle phase distribution was analysed by flow cytometry with propidium iodide staining. Mutants were tested for their ability to adhere to AGS cells and compared with the wild-type SS1 strain. Mutations in genes in the cag pathogenicity island showed that cagP and cagE mutants adhered less than the wild-type strain to AGS cells, whereas a cagF mutant showed no reduction in adherence. Mutations in genes involved in flagellar biosynthesis showed that the adherence ability of fliQ, fliM and fliS mutants was reduced, but a flhB mutant possessed wild-type levels of adherence. Mutations in genes coding for the urease (ureB) and phospholipase (pldA) enzymes did not affect adherence, but mutation of the tlyA gene encoding an H. pylori haemolysin resulted in a reduced adherence. A fliQ mutant, with reduced adherence to AGS cells, was less able to induce AGS cell apoptosis than SS1. The ability to induce G0G1 cell cycle arrest was also abolished in the fliQ mutant. However, an increased cell number in S phase was observed when AGS cells were exposed to the fliQ mutant compared with SS1, suggesting that unattached bacteria may still be able to stimulate cell proliferation. In addition to known adhesins, other bacterial virulence factors such as CagE, CagP, FliQ, FliM, FliS and TlyA appear to play a role in H. pylori adherence to gastric epithelial cells. Mutations in these genes may affect H. pylori pathogenicity by reducing either the ability of the bacteria to attach to gastric epithelial cells or the intensity of bacteria-host cell interactions.     

Decreased gastric proliferation of foveolar epithelial cells after the eradication of Helicobacter pylori.

Increased epithelial cell proliferation is associated with an increased risk of gastric carcinoma. Helicobacter pylori infection is an established risk factor for gastric cancer and the organism has recently been classified as a group I carcinogen by an IARC working group. In this study, we describe differences in gastric epithelial cell proliferation between a H. pylori eradicated group (n = 21) and a not eradicated group (n = 8) after anti-H. pylori eradication therapy to show that increased cell proliferation is associated with H. pylori infection. H. pylori infection was determined by rapid urease test and immunohistochemical method with anti-H. pylori polyclonal antibody. Gastric epithelial cell proliferation was assessed using immunohistochemical method using Ki-67 monoclonal antibody. Ki-67 positive cells in H. pylori associated chronic active gastritis were observed in the glandular neck and the upper portion of foveolar epithelium. Patients who cleared their H. pylori infections showed a significant decrease of Ki-67 labeling index after therapy (0.73 +/- 0.10 vs. 0.48 +/- 0.08, p < 0.01). By contrast, Ki-67 labeling index before and after treatment in patients who remained positive for H. pylori showed no significant difference (0.78 +/- 0.08 vs 0.74 +/- 0.10, p > 0.05). These results indicate that H. pylori infection increases the proliferation of gastric foveolar epithelium, which is reduced by the eradication therapy. We suggest that anti-H. pylori eradication therapy can prevent mucosal cell proliferation to be closely associated with gastric carcinogenesis.     

EZH2 promotes gastric cancer cells proliferation by repressing p21 expression

EZH2 is a core component of the polycomb repressive complex 2 (PRC2), which catalyzes trimethylation of histone H3 lysine 27 (H3K27me3) and promotes carcinogenesis by epigenetically silencing many tumor suppressor genes. Increased EZH2 expression is a marker of advanced and metastatic in many cancers, including lung, prostate and breast cancer, and it has been considered as a potential novel therapeutic target. However, the clinical significance and molecular mechanisms of EZH2 controlling gastric cancer cell proliferation and invasion are not well documented. In this study, immunohistochemical analysis was conducted to investigate the EZH2 expression in gastric cancer. We found that EZH2 levels were increased in gastric cancer tissues compared with adjacent normal tissues. Moreover, patients with high levels of EZH2 expression had a relatively poor prognosis. Furthermore, knockdown of EZH2 expression by siRNA could impair cell proliferation and invasion both in vitro and vivo. Finally, we found that EZH2 influences gastric cancer cells proliferation partly through regulating p21 expression. Our findings present that EZH2 over-expression can be identified as a poor prognostic biomarker in gastric cancer.     

Exosomal miR-155-5p promotes proliferation and migration of gastric cancer cells by inhibiting TP53INP1 expression

Exosomal microRNA (miRNA) secreted by tumor cells plays an important biological role in tumorigenesis and development. We aimed to explore the effects of exosomal miR-155-5p in gastric cancer (GC) and understand its mechanism of action in GC progression. We isolated exosomes from the human gastric mucosal epithelial cell line GES-1 and gastric cancer cell line AGS, and then identified them according to their surface markers by flow cytometry. Later, we detected the miR-155-5p expression levels in tissues and isolated exosomes using RT-qPCR. Bioinformatics analysis showed that miR-155-5p directly binds to the 3' untranslated region (3'-UTR) of tumor protein p53-induced nuclear protein 1 (TP53INP1) mRNA. We also investigated whether the miR-155-5p-rich exosomes caused changes in cell cycle, proliferation, and migration in AGS cells. In this study, we found that the levels of miR-155-5p were significantly increased in GC tissues and AGS cells, and that the TP53INP1 protein level was downregulated in GC tissues using IHC and IFC. TP53INP1 was found to be directly regulated by miR-155-5p following a dual luciferase-based reporter assay. After co-culturing with the isolated miR-155-5p-rich exosomes, the proliferation and migration capabilities of AGS cells were enhanced. Thus, our results reveal that exosomal miR-155-5p acts as an oncogene by targeting TP53INP1 mRNA in human gastric cancer.     

Helicobacter pylori infection and the development of gastric cancer

BACKGROUND: Although many studies have found an association between Helicobacter pylori infection and the development of gastric cancer, many aspects of this relation remain uncertain. METHODS: We prospectively studied 1526 Japanese patients who had duodenal ulcers, gastric ulcers, gastric hyperplasia, or nonulcer dyspepsia at the time of enrollment; 1246 had H. pylori infection and 280 did not. The mean follow-up was 7.8 years (range, 1.0 to 10.6). Patients underwent endoscopy with biopsy at enrollment and then between one and three years after enrollment. H. pylori infection was assessed by histologic examination, serologic testing, and rapid urease tests and was defined by a positive result on any of these tests. RESULTS: Gastric cancers developed in 36 (2.9 percent) of the infected and none of the uninfected patients. There were 23 intestinal-type and 13 diffuse-type cancers. Among the patients with H. pylori infection, those with severe gastric atrophy, corpus-predominant gastritis, and intestinal metaplasia were at significantly higher risk for gastric cancer. We detected gastric cancers in 21 (4.7 percent) of the 445 patients with nonulcer dyspepsia, 10 (3.4 percent) of the 297 with gastric ulcers, 5 (2.2 percent) of the 229 with gastric hyperplastic polyps, and none of the 275 with duodenal ulcers. CONCLUSIONS: Gastric cancer develops in persons infected with H. pylori but not in uninfected persons. Those with histologic findings of severe gastric atrophy, corpus-predominant gastritis, or intestinal metaplasia are at increased risk. Persons with H. pylori infection and nonulcer dyspepsia, gastric ulcers, or gastric hyperplastic polyps are also at risk, but those with duodenal ulcers are not.     

A frequent somatic mutation in CD274 3'-UTR leads to protein over-expression in gastric cancer by disrupting miR-570 binding

Inhibitory costimulatory molecule CD274 expresses in various cancers and contributes to cancer immune evasion by inhibiting T cell activation and proliferation, yet the regulatory mechanisms for CD274 overexpression in cancers are poorly understood. In this study, we discovered a novel mechanism of CD274 expression regulated by miR-570. A guanine-to-cytosine mutation at the 3'-UTR of CD274 mRNA led to CD274 overexpression by disrupting the miR-570 binding. The mutations were widely observed in cancers by sequencing of 276 gastrointestinal cancers (esophageal, gastric, colorectal, hepatocellular, and pancreatic cancers). This mutation was significantly associated with CD274 overexpression in gastric cancer (P = 1.44×10(-10)) and with the pathological features including differentiation grade, depth of tumor invasion, lymph node metastasis, and tumor-node-metastases (TNM) stage. These findings suggest a novel regulatory mechanism for CD274 overexpression in gastric cancer mediated by miR-570 and a somatic mutation in CD274 3'-UTR, and provide a new insight to gastric carcinogenesis.     

LncRNA SNHG14 promotes the progression of cervical cancer by regulating miR-206/YWHAZ

Accumulating evidence suggests that lncRNAs play key roles in many cancers. It has been reported that long non‐coding RNA SNHG14 promotes cell proliferation and metastasis in multiple cancers. However, the role and underlying molecular mechanism of SNHG14 in cervical cancer (CC) remain largely unclear. In this study, we discovered that the relative expression of SNHG14 was significantly upregulated in CC tissues and cells, and associated with the overall survival of CC patients. Moreover, knockdown of SNHG14 significantly inhibited cell proliferation, migration and invasion, and promoted cell apoptosis in CC. Molecular mechanism explorations revealed that SNHG14 acted as a sponge of miR-206 and that YWHAZ was a downstream target gene of miR-206 in CC. Spearman’s correlation analysis uncovered a significantly negative correlation between SNHG14 (or YWHAZ) and miR-206 expression, while a significantly positive correlation between SNHG14 and YWHAZ expression in CC tissues. We also found that the effect of SNHG14 knockdown on the CC progression could be partly rescued by overexpression of YWHAZ at the same time. Our findings revealed that SNHG14 acted as a sponge of miR-206 to regulate the expression of YWHAZ in CC, hinting the promising therapeutic target role of SNHG4 for CC patients.