Matrigel basement membrane matrix

Transfected A549 and H1299 cells were inoculated in the 500 μl medium in the upper chamber of 24-well transwell plates (Corning, USA) containing 8 µm pore at a density of 1 × 10⁵ cells/well. For the invasion assay, the upper chamber was precoated with 150 μL/cm² Matrigel Basement Membrane Matrix (Solarbio, China). Besides, 1 mL medium with 15% FBS (Solarbio, China) was supplied in the lower chamber and the cells were incubated for 48 h. The upper chamber was supplied with serum-free RPMI-1640 (Procell, China). The cells that remained at the upper surface of the membrane were removed, and the migrated or invaded cells below the membrane were fixed with 4% paraformaldehyde (Solarbio, China) for 0.5 h and stained using 10% crystal violet (Solarbio, China) for 0.5 h then observed using CKX53 microscope (Olympus, Japan).

For the invasion assay, Transwell chambers (Corning, New York, USA) lined with Matrigel basement membrane matrix (Solarbio, Beijing, China) were used. The cells were inoculated at a density of 2.5 × 10⁵ cells/ml in the upper chamber without serum. The upper chamber was then placed in the lower chamber containing 20% fetal bovine serum medium and incubated at 37 °C in a 5% CO₂ incubator. After 24 h, the upper chamber was taken out, and the cells were fixed with 4% paraformaldehyde and then stained with 0.1% crystal violet solution. The results were observed under a microscope, and photographs were taken after drying the chambers. The migration assay followed the same procedure, except the Matrigel basement membrane matrix was not added.