BPIFB1 inhibits NPC cell migration and invasion in vitro. (A) BPIFB1 expression in 5-8F, HNE2, and HONE1 cells transfected with the BPIFB1-Flag vector was measured by qPCR and western blot using the anti-Flag antibody. (B) Wound healing assays were performed to measure the cell migration ability of 5-8F, HNE2, and HONE1 cells transfected with the BPIFB1-Flag vector or empty vector. The picture shows the scratch width at 0, 24, and 48 h. (C) A transwell assay was performed to detect the BPIFB1-specific invasion ability of 5-8F, HNE2, and HONE1 cells. Cells were transfected with BPIFB1-Flag or empty vector. The graph summarises data from three independent experiments. *P<0.05; **P<0.01; ***P<0.001. Scale bars=200 μm. (D) BPIFB1 re-expression inhibited the invasive progression of spheroids in a 3D cell culture model. Images of spheroids formed by 5-8F cells in Matrigel (left). The black arrows indicate the scattered protrusions formed on the spheroid surface. Scale bars=50 μm. Quantification of two spheroid types in NC and BPIFB1-overexpressing cells (right).