The long noncoding RNA, TINCR, functions as a competing endogenous RNA to regulate PDK1 expression by sponging miR-375 in gastric cancer

BACKGROUND: Accumulating evidence indicates that the long noncoding RNA, TINCR, plays a critical role in cancer progression and metastasis. However, the overall biological role and mechanisms of TINCR that were involved in human gastric cancer (GC) progression remain largely unknown. METHODS: TINCR expression was measured in 56 paired tumor and adjacent nontumor tissue samples by real-time polymerase chain reaction (PCR). Insights of the mechanism of competitive endogenous RNAs (ceRNAs) were gained from bioinformatic analysis, luciferase assays. The effects of TINCR and miR-375 on GC cell apoptosis and proliferation were studied by RNA interference approaches in vitro and in vivo. The correlation of TINCR and PDK1 was identified by real-time PCR and Western blot analysis. RESULTS: Our results showed that miR-375 level decreased and TINCR level increased in tumor tissues. In addition, TINCR was a target of miR-375 and inhibited its expression in GC cells. Furthermore, the low expression of TINCR increased cell apoptosis and inhibited the proliferation of GC cells, while the downregulation of miR-375 reversed the function. In particular, TINCR could negatively regulate the miR-375 expression and increased the PDK1 expression in GC cells. Finally, tumor growth suppression was retarded with miR-375 downregulated in TINCR knockdown of GC cell xenografts. CONCLUSION: The long noncoding RNA TINCR functions as a competing endogenous RNA to regulate PDK1 expression by sponging miR-375 in GC. The ceRNA regulatory network of TINCR/miR-375/PDK1 allows us to better understand the pathogenesis of GC and facilitate the development of long noncoding RNA (lncRNA)-directed diagnostics in GC.