Matrigel invasion assay
The invasion abilities of OS cells were evaluated using Transwell
invasion chambers precoated with
50 μl of 2 mg/ml Matrigel (BD Biosciences, USA). In brief, 5 ×
104 transfected cells suspended in 200 μl of
serum-free DMEM were seeded into the upper chambers. A 600 μl volume of
DMEM supplemented with 10% FBS was used as the attractant and was added
into the lower chambers. After culture for 24 h, cells adhering to the
lower surface of the membrane were fixed with paraformaldehyde (4%) and
stained using crystal violet (0.1%), whereas cells on the upper surface
of the membrane were removed by wiping with cotton swabs. At least three
random fields of view containing cells that had migrated or invaded to
the lower surface were imaged under an inverted light microscope.