SGK3 and cancer: Nevertheless, some recent reports have indicated that INPP4B acts as an oncogenic driver by activating SGK3 in several kinds of cancer cells.13, 15, 24 As a member of a serine/threonine protein kinase family, SGK3 is highly homologous to and shares substrate specificity to the protein kinase B (PKB)/AKT family.25 Tessier et al25 reported that the main product of INPP4B, PI(3)P, can bind to a Phox homology domain of SGK3, thereby targeting the protein to endosomes, where PI3K and PDK1 phosphorylate SGK3 at two regulatory sites (Thr‐320 and Ser‐486).