Cell invasion assay

The 24-well Transwell plates (8-mm pore size) were coated with 200 mg/ml Matrigel and then dried under sterile conditions overnight. WEHI-3 cells were transfected with miR-18a inhibitor or negative control and maintained at 2×10⁵ cells per ml concentration in RPMI-1640 medium in the upper chamber. The lower chamber contained RPMI-1640 medium mixed with 20% FBS. Following incubation for 48 h, the non-invasive cells in the upper chamber were wiped off using a cotton swab. The cells were then fixed in methyl alcohol for 15 min at room temperature, followed by staining with hematoxylin-eosin for 25 min. A light microscope (Olympus Corporation, Tokyo, Japan) was used for counting the cells that invaded into the lower chamber.