Increased Rac1 and RhoA activity in SW620 cells relative to SW480 cells. Detergent extracts from SW480 and SW620 cells were incubated with immobilized GST-PBD (A) or GST-RBD (C) and the bound proteins were analyzed by immunoblotting (IB) for Rac1 or RhoA, respectively (top panels). Total Rac1 and RhoA levels in the cell lysates are shown below. Tubulin is shown for comparison with RhoA. (B and D) Quantification of active Rac1 and RhoA levels, respectively, by densitometric analysis of immunoblots. The data were normalized to the amount of total Rac1 or tubulin (for RhoA) and are expressed as a fold increase relative to SW480 cells. (E) Graph showing the relative levels of RhoA in SW480 and SW620 cells. In each case, values are the average from at least three independent experiments ± S.E.M. The asterisks indicate a significant difference from SW480 cells (P < 0.05) by Student’s t-test.