The guanine nucleotide exchange factor, Tiam1, specifically activates the Rho-like GTPase Rac (Michiels et al, 1995) and Tiam1-Rac signaling affects cell migration (Hordijk et al, 1997; Sander et al, 1998), invasion (Michiels et al, 1995; Keely et al, 1997; Engers et al, 2001), and metastasis (Habets et al, 1994) of tumour cells. The gene discussed is AKT1; the disease is neoplasm.