Fig. 2. (A) IGF-I induces membrane ruffling in separating MCF-7/IGF-IR/WT cells. Phase-contrast images of serum-starved MCF-7/IGF-IR/WT cells before and after stimulation with 50 ng/ml IGF-I for indicated times. The thin arrows show examples of apical ruffles. Thick arrows indicate nascent gaps at the sites of cell-cell detachment. Bar, 10 µm. (B) Inhibition of membrane ruffling and cell motility in dead-kinase expressing cells. Phase-contrast images of MCF-7/IGF-IR/WT (a,b) and MCF-7/IGF-IR/DK (d,e) cells. Cells were serum-starved (a,d) or stimulated with 50 ng/ml IGF-I for 60 minutes (b,e). Examples of sporadic lateral ruffles in serum-starved cells are indicated by arrows in a and d. As MCF-7/IGF-IR/WT cells moved apart, they extended long, fine cytoplasmic processes with the lamellipodia at the ends (arrows in b). Bar, 10 µm. (c,f) Quantification of cells with ruffles at free edges and over the cell apex, and migratory cells observed during time-lapse filming in MCF-7/IGF-IR/WT (c) and MCF-7/IGF-IR/DK (f) cells. Cells were incubated overnight in serum-free medium (SFM) and then stimulated with 50 ng/ml IGF-I (IGF-I).