A Boyden chamber assay was used, as previously described (17 (link), 29 (link)). Briefly, cells were trypsinized, suspended in 0.1% BSA/RPMI, and seeded (2.5 × 104 cells/well) in the upper compartment of a Boyden chamber (NeuroProbe). A 12-μm-pore Matrigel-coated polycarbonate membrane was used to separate the upper and lower compartments. In the lower chamber, RPMI medium containing 10% FBS was used. After an incubation period of 16 h at 37°C, membranes were recovered and cells on the upper side of the membrane (non-migrating) were wiped off the surface. Migrating cells on the lower side of the membrane were fixed and stained with the Hema 3 Staining kit (Thermo Scientific). Migrating cells in each well were counted in five random fields by contrast microscopy using an Eclipse E200 Nikon microscopy (4X magnification) and the ImageJ/Fiji software.