Fig 1: ß1-integrin is required for sustained c-Met-dependent ERK1/2 phosphorylation in detached cells, c-Met-dependent in vivo tumorigenesis and invasion.(a–d) Western blots for: (a) tubulin and phospho-ERK1/2 in ß1A and GD25 (ß1-/-) cells, stimulated with HGF for 0, 15 and 120 min; (b) Phospho-c-Met (Y1234-355), c-Met, phospho-ERK1/2, ERK 1/2 and tubulin in M1268T c-Met-expressing NIH3T3; (c) phospho-c-Met (Y1234-355), GFP (c-Met-GFP: p195, precursor; p170, mature ß chain), ß1-integrin, phospho-ERK1/2 and tubulin in c-Met-GFP cells incubated with tetracycline (Tet) for 0 or 16 h; (d) ß1-integrin, phospho-ERK1/2, and tubulin in A549 cells, stimulated without (-) or with (+) HGF for 120 min in suspension; (b–d) All cells were transfected with control (Cont) or ß1-integrin (ß1) (human cells: oligo 1, Qiagen; mouse cells: oligo 3, Dharmacon) siRNA. Graphs represent phospho-ERK1/2/tubulin ratios (means±s.e.m.), normalized to appropriate controls: (a,d) no HGF; (b,c) siRNA control (Cont), obtained by densitometric analysis (n=3 to 6). (e) Tumour growth curves, over time, of M1268T c-Met-expressing NIH3T3 cells, transfected with control (Cont) or ß1-integrin (ß1) siRNA. Data are mean tumour volume (mm3)±s.e.m. of n=5 mice per group. (f) Pictures of the lungs of mice dissected 21 days after injection into the tail vein with either control (Cont) (n=4) or ß1-integrin (ß1) (n=5) siRNA-transfected M1268T c-Met-expressing NIH3T3 cells. Graph represents the mean number of macroscopic tumours per mouse±s.e.m. (g) Mean number±s.e.m. of disseminated WT and M1268T c-Met-expressing NIH3T3 cells per zebrafish embryo 24 h after injection. Cells were transfected with control (Cont) or ß1-integrin (ß1) siRNA (n=3, average of 25 embryos per condition per experiment). t-Test, * P<0.05; **P<0.01; ***P<0.001.