PAK1 and neoplasm: Expression and activity of PAK1 in human breast tumors correlates with tumor grade(Holm et al., 2006; Salh, Marotta, Wagey, Sayed, & Pelech, 2002; Vadlamudi et al., 2000), and transgenic expression of active PAK1 in mouse mammary tissue is tumorigenic (R. A. Wang, Zhang, Balasenthil, Medina, & Kumar, 2006).