IGF2-AS affects the prognosis and metastasis of gastric adenocarcinoma via acting as a ceRNA of miR-503 to regulate SHOX2

Disorder of long non-coding RNAs (LncRNAs) is found in various types of cancers and demonstrated to be associated with tumor occurrence and development. Our study found that lncRNA insulin growth factor 2 antisense (IGF2-AS) is up-regulated in gastric adenocarcinoma (GAC) tissues and correlated with poor prognosis in patients with GAC. Cell counting kit-8 (CCK8), colony formation, wound healing and transwell assays revealed that knockdown of IGF2-AS in BGC823 and SGC7901 cells significantly suppressed cell proliferation, migration and invasion. While, overexpression of IGF2-AS in AGS and MGC803 cells exhibited the opposite effects. RNA-FISH and subcellular fractionation assay found that most IGF2-AS was distributed in the cytoplasm, suggesting that IGF2-AS functioned as a potential ceRNA. RNA binding protein immunoprecipitation (RIP) assays further confirmed this assumption. By informatics prediction and luciferase reporter assay, we found that IGF2-AS functioned as an efficient miR-503 sponge and the level of miR-503 showed an inverse correlation with IGF2-AS. Short stature homeobox 2 (SHOX2) is predicted and verified as a target of miR-503. Moreover, IGF2-AS expression exhibited a negative correlation with miR-503 and a positive correlation with IGF2-AS. Subsequent rescue assay revealed that down-regulation of miR-503 or restoration of SHOX2 canceled IGF2-AS depletion-induced depression in proliferation and motility of BGC823 and SGC7901 cells. Meanwhile, up-regulation of miR-503 or down-regulation of SHOX2 decreased IGF2-AS overexpression induced promotion in proliferation and motility of AGS and MGC803 cells. In vivo tumorigenicity assay showed that knockdown of IGF2-AS significantly reduced tumor volume. Taken together, our results demonstrated that IGF2-AS takes important regulatory parts in GAC development by functioning as a ceRNA to regulate SHOX2 via sponging miR-503.