MYCN and neuroblastoma: Additionally, combined treatment with all-trans retinoic acid (ATRA) and 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) on human IMR32 neuroblastoma cells and mouse neuroblasts Neuro2a induced differentiation and neuron outgrowth; this was accompanied by a decreased expression of MYCN in the case of IMR32 cells.