The β4 integrin regulates cell migration. Related to Fig. 3. (A) Flow cytometry of cell surface β4 integrin in WT, PD-L1^KO, and PD-L1^KO-PD-L1-EGFP MDA-MB-231 cells. (B) Immunoblotting shows integrin β4 protein expression in WT and PD-L1^KO 4T1 cells. α-Tubulin was used as loading control. The same α-tubulin immunoblot is shown in Fig. 1 A. (C) Schematic of the design to generate dox-inducible β4 4T1-β4-tdTomato cells. tGFP, turbo GFP; mCMV, murine cytomegalovirus promoter. (D) Flow cytometry of cell surface β4-tdTomato in WT and 4T1-β4-tdTomato cells. (E) Flow cytometry of cell surface β4-tdTomato (x-axis) and tGFP (y-axis) in 4T1-β4-tdTomato cells that were treated with doxycycline for different days. (F) Representative images of dox-inducible shβ4 4T1-β4-tdTomato cells show β4-tdTomato (red) and tGFP (green) distribution without dox treatment (left, No Dox) or with dox treatment for 3 days at 2 µg/ml (right, Dox). Scale bar: 10 μm. (G) Flow cytometry of cell surface PD-L1 in 4T1-β4-tdTomato cells (No Dox, red) or with dox treatment for 3 days at 2 µg/ml (DOX, green). (H) Flow cytometry of cell surface β4 integrin in WT MDA-MB-231 cells treated with siCtrl or siRNAs against β4 integrin (siβ4-1 and siβ4-2) for 3 days. (I) Trans-well migration assays comparing cell migration in siCtrl and siβ4 MDA-MB-231. Data are shown as means ± SD from three independent experiments. Statistical significance was determined by two-sided unpaired t test.  *, 0.05 > P ≥ 0.01. Source data are available for this figure: SourceData FS3.