Project description:To identify GC-related RNAs, we used five GC patients’ fresh tumor tissues and paired adjacent non-tumor tissues for RNA sequencing. Differential expressions of circRNAs and mRNAs were then analyzed.
Project description:MicroRNA (miRNA) sponges containing miRNA complementary binding sites constitute a potentially useful strategy for miRNA-inhibition therapeutics in cancer patients. Recently, naturally occurring circular RNAs (circRNAs) have been revealed to function as efficient microRNA sponges. We hypothesized that synthetic circRNA sponges targeting oncomiRs could be constructed and used to achieve potentially therapeutic microRNA loss of function. In this study, linear RNA molecules containing five miR-21 binding sites were transcribed in vitro. After dephosphorylation by calf intestinal phosphatase and phosphorylation by T4 polynucleotide kinase, circRNA sponges were circularized using 5’-3’ end ligation by T4 RNA ligase 1. Synthetic circular sponge stability was assayed in the presence of RNase R or fetal bovine serum. Luciferase reporter and cell proliferation assays were performed to assess competitive inhibition of miR-21 activity by circRNA sponges in NCI-N87 gastric cancer cells. Tandem Mass Tag (TMT) labeling proteomics analysis and Western blotting were performed to delineate effects of circRNA sponges on miR-21 downstream targeted proteins. Our experiments revealed that artificial circRNA sponges can be synthesized using enzymatic ligation. These synthetic circRNA sponges are more resistant than their linear RNA counterparts to nuclease degradation in vitro. They effectively suppress the activity of miR-21 on its downstream protein targets, including the important cancer protein DAXX. Finally, they also inhibit gastric cancer cell proliferation. Our results suggest that synthetic circRNA sponges represent a rapid, effective, convenient strategy to achieve loss of miRNA function in vitro, with potential future therapeutic application in vivo.
Project description:The prognosis after curative resection of gastric cancer (GC) remains unsatisfactory, and thus, the development of treatments involving alternative molecular and genetic targets is critical. Circular RNAs (circRNAs), new stars of the non-coding RNA network, have been identified as critical regulators in various cancers. Here, we aimed to determine the circRNA expression profile and investigate the functional and prognostic significance of circRNA in GC. Using next-generation sequencing profiling, we first characterized an abundant circRNA, hsa_circ_0008549, derived from the OSBPL10 gene, and named it circOSBPL10. The expression of circOSBPL10 was found via quantitative real-time RT-PCR (qRT-PCR) to be upregulated in GC tissues, and silencing of circOSBPL10 significantly inhibited gastric cancer cell growth, migration and invasion in multiple experiments. We further confirmed that miR-136-5p is a downstream target of circOSBPL10 using RNA pull-down and luciferase reporter assays. Rescue experiments confirmed that circOSBPL10 regulates biological functions in GC cells via a circOSBPL10-miR-136-5p-WNT2 axis. In vivo experiments showed that circOSBPL10 promotes tumor growth and metastasis in mice. Furthermore, the level of circOSBPL10 was observed to be a prognostic marker of the overall survival and disease-free survival of patients with GC. Taken together, our findings reveal that circOSBPL10 may serve as a new proliferation factor and prognostic marker in gastric cancer.
