INPP4B and breast cancer: Although INPP4B functions as a tumor suppressor in triple negative breast cancer by suppressing PI(3,4)P2-mediated AKT activation [21,56,57], INPP4B mRNA and protein expression are up-regulated in primary human PIK3CA-mutant ER+ breast cancers, enhancing tumor cell proliferation and growth via activation of Wnt/β-catenin signaling or SGK3 activation [25,26].