Background/Aim: Gastric cancer is one of the most common malignant tumors, and its complex pathogenesis has not been fully elucidated. Circular RNAs (circRNAs) are involved in various biological processes and human diseases. However, their exact functional roles and mechanisms of action remain largely unclear. We previously discovered the differential expression of non-coding RNAs (ncRNAs) during the malignant transformation of human gastric epithelial cells. In this study, we investigated the functional roles of a significantly up-regulated circRNA (hsa_circ_0000592) in gastric cancer. Methods:N-methyl-N′-nitro-N-nitrosoguanidine (MNNG)-induced malignant-transformed gastric epithelial cells (GES-1-T) and normal gastric epithelial cells (GES-1-N) were analyzed by high-throughput circRNA sequencing. The top 15 up-regulated circRNAs in high-throughput sequencing results were further confirmed by qRT-PCR in different gastric epithelial cell lines. The function of the most significant circRNA (hsa_circ_0000592) was investigated by using RNA interference (RNAi) assays, fluorescence in situ hybridization analysis (FISH), and bioinformatics prediction methods. Results: A total of 1509 genes were up-regulated and 3142 genes were down-regulated in GES-1-T cells when compared with GES-1-N cells. When compared with GES-1-N cells, hsa_circ_0000592 was obviously up-regulated in GES-1-T cells, as well as in other gastric cancer cell lines. The silencing of hsa_circ_0000592 mRNA led to a decrease in cell proliferation, cell cycle arrest at the G0/G1 phase, an increased rate of apoptosis, and a reduction in cell migration. Furthermore, FISH showed that hsa_circ_0000592 was mainly located in the cytoplasm, and a bioinformatics analysis suggested that hsa_circ_0000592 might function by sponging multiple miRNAs, and most notably four conserved miRNAs, including miR-139-3p, miR-200, miR-367-3p, and miR-33a-3p. Conclusion: This study is the first to identify hsa_circ_0000592 as a novel circRNA with a critical role in MNNG-induced gastric cancer. Due to the essential role of hsa_circ_0000592 in gastric carcinoma cells, it may be considered as a potential biomarker for use in diagnosing gastric carcinoma. Our findings provide a new insight into the function of circRNAs in environmental carcinogen-induced gastric cancer.

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Background Accumulating evidences have shown that circular RNAs (circRNAs) play important roles in regulating the pathogenesis of cancer. However, the role of circRNAs in gastric cancer (GC) remains largely unclear. Methods In this study, we identified a novel upregulated circRNA, hsa_circ_0001829, in chemically induced malignant transformed human gastric epithelial cells using RNA-seq. Subsequent qRT-PCR and ISH assays were performed to detect the expression level of hsa_circ_0001829 in GC cell lines and tissues. Functional roles of hsa_circ_0001829 in GC were then explored by loss- and gain-of- function assays. Bioinformatic prediction and luciferase assay were used to investigate potential mechanisms of hsa_circ_0001829. Finally, the mice xenograft and metastasis models were constructed to assess the function of hsa_circ_0001829 in vivo. Results We found that hsa_circ_0001829 was significantly upregulated in GC tissues and cell lines. Loss- and gain-of- function assays showed that hsa_circ_0001829 promotes GC cells proliferation, migration and invasion, and the affected cell cycle progression and apoptosis rates may account for the effect of hsa_circ_0001829 on GC proliferation. In addition, bioinformatic prediction and luciferase assay showed that hsa_circ_0001829 acts as a molecular sponge for miR-155-5p and that SMAD2 was a target gene of miR-155-5p; moreover, hsa_circ_0001829 sponges miR-155-5p to regulate SMAD2 expression and hsa_circ_0001829 promotes GC progression through the miR-155-5p–SMAD2 pathway. Finally, suppression of hsa_circ_0001829 expression inhibited tumor growth and aggressiveness in vivo. Conclusion Taken together, our findings firstly demonstrated a novel oncogenic role of hsa_circ_0001829 in GC progression through miR-155-5p–SMAD2 axis, and our study may offer novel biomarkers and therapeutic targets for GC.

A method for the simultaneous determination of glyoxalate and oxalate by capillary zone electrophoresis (CZE) was developed. The influences of type, concentration and pH of the running buffer, and the applied voltage on separation were investigated. Glyoxalate and oxalate were separated within 11 min under the conditions of 20 mmol/L borax-5.5 mmol/L potassium hydrogen phthalate (pH 9.0), applied voltage of 20 kV, and detected wavelength of 212 nm. The calibration curves of glyoxalate and oxalate showed good linearity in the ranges of 0.8 -20 g/L and 1.2-20 g/L, respectively. The correlation coefficients were 0.999 3 and 0.997 5, respectively. The limits of detection for glyoxalate and oxalate were 0.2 and 0.4 g/L (S/N = 3), respectively. The average recoveries at three spiked levels were 98.3%-102.5% with acceptable relative standard deviations of 0.35%-0.61%. This method is simple, low cost and high performance. The method was successfully used for the determination of glyoxalate and oxalate in real samples, and the assay results were satisfactory.

Background: Accumulating evidences have shown that circular RNAs (circRNAs) play important roles in regulating the pathogenesis of cancer. However, the role of circRNAs in gastric cancer (GC) remains largely unclear. Methods: In this study, we identified a novel upregulated circRNA, hsa_circ_0001829, in chemically induced malignant transformed human gastric epithelial cells using RNA-seq. Subsequent qRT-PCR was performed to detect the expression level of hsa_circ_0001829 in GC cell lines and tissues. Functional roles of hsa_circ_0001829 in GC were then explored by loss- and gain-of- function assays. Bioinformatic prediction and luciferase assay were used to investigate potential mechanisms of hsa_circ_0001829. Finally, the mice xenograft models were constructed to assess the function of hsa_circ_0001829 in vivo.Results: We found that hsa_circ_0001829 was significantly upregulated in GC tissues and cell lines. Loss- and gain-of- function assays showed that hsa_circ_0001829 promotes GC cells proliferation, migration and invasion, and the affected cell cycle progression and apoptosis rates may account for the effect of hsa_circ_0001829 on GC proliferation. In addition, bioinformatic prediction and luciferase assay showed that hsa_circ_0001829 acts as a molecular sponge for miR-155-5p and that SMAD2 was a target gene of miR-155-5p; moreover, hsa_circ_0001829 sponges miR-155-5p to regulate SMAD2 expression and hsa_circ_0001829 promotes GC progression through the miR-155-5p–SMAD2 pathway. Finally, suppression of hsa_circ_0001829 expression inhibited subcutaneous tumor growth in vivo. Conclusion: Taken together, our findings firstly demonstrated a novel oncogenic role of hsa_circ_0001829 in GC progression, which is through miR-155-5p–SMAD2 axis, and our study may offer novel biomarkers and therapeutic targets for GC.