As a first step, we chose to study DOCK4 and DOCK9 among a large family of GEFs, given that DOCK4 and DOCK9 have been demonstrated to respectively activate Rac1 and Cdc42 [27,28,29,30] and that mutations in DOCK4 [31,32,33,34,35] and DOCK9/Zizimin1 [36] have been found in a number of cancers. The gene discussed is CDC42; the disease is cancer.