Background: Gastric cancer (GC) remains a huge challenge to the heathy of human beings, largely due to lacking of effective therapeutic measures. Though an oncogenic role for circular RNAs (circRNAs) circ_0067997 in the progression of GC has been described recently, the molecular modulatory mechanism of it still remains to be further explored. The aim of present study is to examine the molecular network of circ_0067997 in GC.
Methods: qRT-PCR was carried out to determine the mRNA levels of circ_0067997, miR-615-5p and AKT1 in cisplatin (DDP)-insensitive or sensitive GC tumor tissues and cells, while the correlations among the contents of these molecules were determined by statistical analysis. The expression of circ_0067997 was manipulated by short-hairpin RNA and lentiviral-mediated approaches, while that of miR-615-5p was achieved by the application of its inhibitor or mimic. The in vivo action of circ_0067997 on tumor formation was determined by measuring tumor weight/volume/size and analyzing tumor apoptosis through TUNEL staining in mouse xenograft model and, while the in vitro effects of this circRNA and its target miR-615-5p on the cell survival and death were separately evaluated by CCK-8 assay and flow cytometry. Additionally, luciferase reporter assays were executed to determine the sequentially regulatory relationships of circ_0067997, miR-615-5p, and AKT1.
Results: Our data demonstrated that the level of circ_0067997 level was increased in DDP-insensitive GC tissues and cell line, while miR-615-5p presented the opposite results. Moreover, the relationships between circ_0067997 and miR-615-5p levels, circ_0067997 and AKT1 contents presented negative and positive correlations in clinic samples, respectively. Importantly, circ_0067997 was found to repress miR-615-5p expression, consequently leading to increased growth while reduced apoptosis of GC cells in the presence of DDP. Furthermore, the validated sequential regulation was circ_0067997 modulating miR-615-5p adjusting AKT1.
Conclusions: This study demonstrated that circ_0067997 functioned as a sponge of miR-615-5p to target AKT1 expression, thereby enhancing the growth and restricting the apoptosis of DDP-insensitive GC cells. These new findings offered a valuable target for the detection and management of GC.
Keywords: Cell proliferation and apoptosis; Circ_0067997; Cisplatin (DDP); gastric cancer; miR-615-5p/AKT1 axis.