Interferon regulatory factor 4 binding protein (IBP, a Rho-family guanine nucleotide exchange factor for Rho family GTPases, including Rac1, RhoA and Cdc42 [89]) can mediate Rac1, RhoA and Cdc42 activation in breast cancer cells to regulate actin cytoskeleton rearrangement and MMP production. The gene discussed is RAC1; the disease is breast carcinoma.