Transwell assay

Matrigel™ (BD Biosciences, San Jose, CA, USA) was diluted to 1 : 7 using the basal medium without serum. Fifty microliters of Matrigel Matrix solution was added into each chamber (Corning, Lowell, MA, USA). One hundred microliters of the suspension of WT cells (2 × 10⁵ cells·mL⁻¹) from different groups was seeded into the chambers and incubated in the basal medium without serum. Five hundred microliters of medium containing 10% FBS was added to the chambers at the bottom. After 24 h, the cells were removed from the top chambers using cotton swabs. PBS was utilized to wash the inserts three times. Cells that moved below were fixed with paraformaldehyde (4%) and stained with crystal violet (1%).