Results from recent studies suggest that aberrant microRNA expression is common in numerous cancers. Although miR-338-3p has been implicated in hepatocellular carcinoma, its role in gastric cancer is unknown. To this end, we report that miR-338-3p is downregulated in both gastric cancer tissue and cell lines. Forced expression of miR-338-3p inhibited cell proliferation and clonogenicity and induced a G 1 -S arrest as well as apoptosis in gastric cancer cells. Furthermore, P-Rex2a (PREX2) was identified as a direct target of miR-338-3p, and silencing P-Rex2a resulted in the same biologic effects of miR-338-3p expression in gastric cancer cells. Furthermore, both enforced expression of miR-338-3p or silencing of P-Rex2a resulted in activation of PTEN, leading to a decline in AKT phosphorylation. Also, miR-338-3p markedly inhibited the in vivo tumorigenicity in a nude mouse xenograft model system. These results demonstrate that miR-338-3p affects gastric cancer progression through PTEN-AKT signaling by targeting P-Rex2a in gastric cancer cells, which posits miR-338-3p as a novel strategy for gastric cancer treatment.

Background. It has been reported that circRNAs are differentially expressed in a wide range of cancers and could be used as a new biomarker for diagnosis. However, the correlation between circRNAs and gastric cancer (GC) it is still unclear. Materials and Methods. In this study, by using real-time quantitative reverse transcription-polymerase chain reactions (qRT-PCRs), we detected the expression level of hsa_circ_0001649 in tissue and serum samples from GC patients. Results. We found that hsa_circ_0001649 expression was significantly downregulated in GC tissue compared with their paired paracancerous histological normal tissues (PCHNTs) (P < 0.01). We next analyzed the expression level of hsa_circ_0001649 in serum samples between preoperative and postoperative GC patients. We found that its level in serum was significantly upregulated after surgery (P < 0.01). The area under the receiver operating characteristic (ROC) curve was 0.834. Moreover, the expression level of hsa_circ_0001649 was significantly correlated with pathological differentiation (P = 0.039). Conclusion. Our test suggested that hsa_circ_0001649 was significantly downregulated in GC and may become a novel potential biomarker in the diagnosis of GC.