Indeed, both LY294002 and rapamycin significantly enhanced entinostat-mediated effects on cell viability (Supplementary Figure 5E, F), suggesting that HDAC1–3 inhibitors, but not HDAC8 inhibitors, cooperate with PI3K/mTOR inhibitors in our neuroblastoma MYCN-driven model. Here, PIK3CA is linked to neuroblastoma.