A role for INPP4B in lysosomal functions is further supported by the observation that elevated expression of INPP4B in PIK3CA-mutant ER+ breast cancer cells induce formation of late endosomes and lysosomes, increase cargo trafficking toward lysosomes, and promote endosomal sequestration and lysosomal degradation of key signaling proteins (28). The gene discussed is PIK3CA; the disease is breast carcinoma.