INPP4B and breast carcinoma: In contrast, however, a reduction in INPP4B expression in PTEN-null breast cancer lines has recently been argued to drive PI(3,4)P2-dependent negative feedback, reducing activation of AKT and sensitizing cell growth to PI3Kβ inhibitors, an effect suggested to result from direct PI(3,4)P2-mediated inhibition of class I PI3Ks (Reed and Shokat, 2017).