Tiam1 expression correlates with motility, but not Rac activation, in human breast cancer cell lines. (a) Lysates were collected from a panel of human breast cancer cell lines and examined with Western blot for expression of Tiam1, Vav, Rac1, Cdc42, and α-tubulin (loading control). Lysates were also examined with affinity precipitation assays for levels of activated Rac1 (Rac1-GTP) and Cdc42 (Cdc42-GTP). Cell lines are ordered from highest motility on the left to lowest motility on the right. (b) The indicated cell lines were examined with Western blot by using a Tiam1 antibody (c-16) in the presence (upper panel) or absence (second panel) of blocking peptide, as described in Materials and Methods. All blots shown are representative of at least three independent experiments.