CircRNA circ-ATAD1 Is Upregulated in Cervical Squamous Cell Carcinoma and Regulates Cell Proliferation and Apoptosis by Suppressing the Maturation of miR-218

The oncogenic function of circ-ATAD1 has been characterized in gastric cancer, while its role in cervical squamous cell carcinoma (CSCC) is unclear. This study explored the role of circ-ATAD1 in CSCC. To evaluate the differential expression of circ-ATAD1, mature miR-218, and premature miR-218 in CSCC, a total of 62 CSCC patients were subjected to biopsies to collect CSCC and paired normal tissues. Gene expression levels were quantified by RT-qPCRs. Nuclear fractionation assay was performed to analyze the subcellular location of circ-ATAD1. CSCC cells were used to perform cell transfections to explore the crosstalk between circ-ATAD1 and miR-218. The roles of circ-ATAD1 and miR-218 in CSCC cell behaviors were explored by BrdU assay, Transwell assay, cell apoptosis assay, and cell stemness assay. CSCC tissues exhibited upregulated expression of circ-ATAD1, which was localized to both nucleus and cytoplasm. Mature miR-218 was downregulated in CSCC tissues and was inversely correlated with circ-ATAD1, while premature miR-218 was not differentially expressed in CSCC. Upregulation of circ-ATAD1 in CSCC cells decreased the expression levels of mature miR-218, but not that of premature miR-218. In addition, overexpression of circ-ATAD1 increased cell proliferation and decreased cell apoptosis, while overexpression of miR-218 decreased cell proliferation and increased cell apoptosis, and it also attenuated the effects of overexpression of circ-ATAD1 on cell proliferation. However, CSCC cell invasion, migration, and stemness were not affected by circ-ATAD1 and miR-218. Circ-ATAD1 is upregulated in CSCC and may regulate cell proliferation and apoptosis by suppressing the maturation of miR-218.