Several Rho GTPases regulate cancer cell adhesion to ECs. (A and B) PC3 cells transfected with the indicated siRNA pools (A) or single siRNAs (B) were added to HUVECs for 15 min, and the percentage adhesion relative to control was determined. Data are expressed as the percentage of total cells analyzed. (C) DU145 cells transfected with siRNAs targeting Cdc42, Rac1, and RhoA or control siRNA (control) were added to confluent HUVECs for 30 min, and the number of cells adhering to ECs was scored. Data are presented as percentages with respect to control cells. (D) Lysates of PC3 cells transfected with indicated single siRNAs were immunoblotted as shown. Values (A–C) are means ± SEM (error bars; n ≥ 3); ***, P < 0.001; **, P < 0.01; *, P < 0.05. (E) Confocal images of PC3 cells transfected with single siRNAs as indicated. Cells were fixed and stained with DAPI (blue) and for F-actin (grayscale). Arrows indicate F-actin–rich protrusions (control, RhoA, Cdc42); arrowheads indicate an elongated tail (RhoA), cells with no F-actin-rich protrusions (Rac1), or an area of membrane retraction between F-actin–rich protrusions (Cdc42). Bar, 20 µm.