In acute promyelocytic leukemia (APL), PI3K/Akt signaling is constitutively activated, and cells that are exposed to all-trans retinoic acid (ATRA) seem to be very sensitive to class I PI3K, p110beta, or p110delta inhibitors, and to rapamycin [83,106]. The gene discussed is PIK3CD; the disease is acute promyelocytic leukemia.