Invasion Assay for Lung Cancer Cells

The invasion of transfected A549 and H1975 cells was detected using Matrigel (BD Biosciences, Franklin Lakes, NJ, USA) coated 24-well invasion chambers (8 µM pore size; Corning, Beijing, China) [26 (link)]. The upper chamber contained serum-free RPMI 1640 medium and 1 × 10⁵ A549 and H1975 cells, and the lower chamber was filled with full RPMI 1640 medium containing 10% FBS (Gibco). Afterward, the chambers were maintained for 48 h at 37°C in 5% CO₂. Then, the cells that were attached to the lower surface of the filter membrane were removed by a cotton swab, and the invaded cells were fixed and stained with crystal violet for cell counting. The digital photographs were seized by an Olympus microscope (CX41) at five non-overlapped fields that were selected arbitrarily. Finally, the average number of the invaded LUAD cells was calculated.