One such candidate is Phosphatidylinositol-3,4,5-trisphosphate RAC Exchanger 2 (PREX2),a 183-kDa protein known to inhibit PTEN phosphatase activity, stimulate PI3K signaling,and suspected to regulate the small GTPase RAC1 (Fineet al., 2009; Cerami et al., 2012).Using whole-genome sequencing of 25 metastatic tumors, Berger and colleagues identifiedPREX2 as being a highly mutated gene in melanoma. The gene discussed is PREX2; the disease is melanoma.