We then isolated established neuroblastoma tumors of nf1a+/+;nf1b+/+;MYCN and nf1a-/-;nf1b+/+;MYCN zebrafish to examine expression of key genes involved in control of the cell cycle, including ccna1, ccna2, ccnb1, ccnd1, ccnd2, ccnd3, ccne, cdk2, cdk4, cdk6 and e2f1. The gene discussed is E2F1; the disease is neuroblastoma.