Cell lines and transfection

A human cervical epithelial cell line (HCvEpCs) and Hela, SiHa and C33A CC cell lines were obtained from the American Type Culture Collection (Manassas, VA, USA). Cells were grown in Dulbecco's Modified Eagle's medium (DMEM) supplemented with 10% heat-inactivated fetal bovine serum (FBS; Gibco; Thermo Fisher Scientific, Inc., Waltham, MA, USA) at 37°C in an atmosphere containing 5% CO₂. SiHa cells were seeded in 96-well plates at a density of 2×10⁵ cells/well and grown to 70% confluence. Cells were then transfected with negative control miRNA (miR-NC), miR-218 mimics or miR-218 inhibitor using Lipofectamine^® 2000 (Invitrogen; Thermo Fisher Scientific, Inc.). Subsequently, the transfected cells were incubated for a further 72 h. The miR-218 sequences transfected were 5′-TGCATGGTTAGATCAAGCACAAGGG-3′ and 5′-CTCGTCTTATTTCCGTGACTGTTTT-3′.