ASCL2 expression contributes to gastric tumor migration and invasion by downregulating miR223 and inducing EMT

Achaete-scute homolog 2 (ASCL2), a basic helix-loop-helix transcription factor, serves an essential role in the maintenance of adult intestinal stem cells and the growth of gastric cancer (GC). However, the function of ASCL2 in the metastasis of GC is poorly understood. The present study aimed to evaluate the effect of ASCL2 expression on gastric tumor metastasis. ASCL2 protein expression was detected in 32 cases of gastric metastasis and its relevant primary tumors using western blotting and immunohistochemistry. The data suggested that the expression of ASCL2 was highest in metastatic tumors, among adjacent normal tissues, primary gastric tumors and gastric metastatic tumors. Furthermore, ASCL2-overexpressing GC cell lines MKN1-ASCL2 and SNU16-ASCL2 were established. An in vitro assay suggested that microRNA 223 (miR223) expression was downregulated following ASCL2 overexpression, and that the expression of the epithelium-associated protein E-cadherin was significantly decreased, while a series of mesenchyme-associated proteins, including zinc finger E-box-binding homeobox 1 (Zeb-1), twist-related protein 1, integrin, vimentin, 72 kDa type IV collagenase and matrix metalloproteinase-9 were upregulated in ASCL2-overexpressing cells. Overexpression of miR223 attenuated the epithelial-mesenchymal transition (EMT)-promoting effect induced by ASCL2 expression. In addition, the results of the chromatin immunoprecipitation and luciferase reporter gene assays indicated that ASCL2 was able to interact with the promoter of pre-miR223, and to inhibit the maturation of miR223, which may interact with the 3′ untranslated region of Zeb-1 and inhibit EMT in tumor cells. The results of the present study demonstrated that ASCL2 was able to downregulate the expression level of miR223, contribute to EMT and promote gastric tumor metastasis, which indicated that ASCL2 may serve as a therapeutic target in the treatment of GC.