CircDOCK1 suppresses cell apoptosis via inhibition of miR­196a­5p by targeting BIRC3 in OSCC.

Oral squamous cell carcinoma (OSCC) is the most frequent oral cancer in the world, accounting for more than 90% of all oral cancer diagnosis. Circular RNAs (circRNAs) are large types of non-coding RNAs, demonstrating a great capacity of regulating the expression of genes. However, most of the functions of circRNAs are still unknown. Recent research revealed that circRNAs could serve as a miRNA-sponge, consequently regulating the expression of target genes indirectly, including oncogenes. In this study, we built an apoptotic model with TNF-α, and then we confirmed a circRNA associated with the apoptosis of OSCC cells, circDOCK1 by comparing the expression profile of circRNAs in an apoptotic model with that in untreated OSCC cells. We ascertained the presence of circDOCK1 with qRT­PCR and circRNA sequencing. The knockdown of the expression of circDOCK1 led to the increase of apoptosis. Utilizing multiple bioinformatics methods, we predicted the interactions among circRNAs, miRNAs and genes, and built the circDOCK1/miR­196a­5p/BIRC3 axis. Both the silencing of circDOCK1 with small interfering RNA and the upregulation of the expression of miR­196a­5p with mimics led OSCC cells to increase apoptosis and decrease BIRC3 formation. We further confirmed this outcome by comparing the expression of circDOCK1, miR­196a­5p and BIRC3 in oral squamous carcinoma tissue with those in para­carcinoma tissue, and examining the expression profile of circRNAs in oral squamous carcinoma tissue and para­carcinoma tissue with microarray. Our results demonstrated that circDOCK1 regulated BIRC3 expression by functioning as a competing endogenous RNA (ceRNA) and participated in the process of OSCC apoptosis. Thus, we propose that circDOCK1 could represent a novel potential biomarker and therapeutic target of OSCC.