Circular RNA circDNA2 upregulates expression to promote the progression of gastric cancer via miR-149-5p suppression.

Circular (circ)RNAs are widely involved in gastric cancer (GC) pathogenesis, and coiled-coil domain containing 6 () is a fused partner of multiple oncogenes; however, the underlying mechanisms of how circRNAs regulate expression in the progression and prognosis of GC remain unclear. Here, we discovered the circRNA derived from the gene locus (circDNA2) through RNA sequencing. By performing quantitative real-time PCR and fluorescence hybridization (FISH) assays with a human tissue microarray, circDNA2 was found to be highly expressed in GC tissues and associated with lymphatic invasion of GC patients. Knockdown of circDNA2 expression suppressed the proliferation of GC cells by reducing expression. Mechanistically, circDNA2 acted as a microRNA (miR)-149-5p sponge, which was confirmed to target by RNA pulldown and dual-luciferase reporter assays and rescue experiments. Both low miR-149-5p expression and high expression were related to unfavorable prognosis in GC patients. Moreover, GC patients with low miR-149-5p expression had shorter overall survival and a higher risk of chemotherapy resistance than those with high miR-149-5p expression. In summary, circDNA2 contributes to the growth and lymphatic metastasis of GC by upregulating expression by sponging miR-149-5p. The circDNA2/miR-149-5p/ axis might be developed as a therapeutic target and prognostic indicator for GC.