DDX1 and retinoblastoma: DEAD box 1 (DDX1) was first identified by differential screening of a retinoblastoma cDNAlibrary, and subsequently found to be amplified and overexpressed in a subset ofretinoblastoma and neuroblastoma tumours and cell lines8, 9, 10, 11, 12.DDX1 expression is ubiquitous, with proliferating cells and cells derived fromneuroectodermal tissues expressing the highest levels of DDX18, 13.