PREX2, previously recognized as an oncogene in diverse cancers, such as melanoma [14, 29], hepatocellular carcinoma [16], lung carcinoma [30], and pancreatic ductal adenocarcinoma [17], is a GEF regulating Rac activity under activated PI3K and G-coupled receptor signaling [31]. The gene discussed is PREX2; the disease is hepatocellular carcinoma.