Expression and amplification of the N-myc gene in primary retinoblastoma

Abstract

Retinoblastoma, the most common intraocular tumour of childhood, probably arises from embryonal cells and occurs in hereditary and non-hereditary forms¹. Recent evidence suggests that this retinoblastoma (Rb) susceptibility gene located at chromosome 13q14 is actually recessive^2–4. Knudson has proposed that the tumour is caused by two mutational events⁵. This idea was extended by Comings⁶, who suggested that dominantly inherited tumours may resuit from loss or inactivation of both alleles of regulatory or suppressor genes that, when active, prevent the expression of a structural transforming gene(s) (possibly an oncogene) normally active only during embryogenesis. Despite circumstantial evidence^3,4,7,8for this hypothesis, no activated oncogene^9–14 has been identified. We now report that (1) the N-myc gene is amplified 10–200-fold in two primary retinoblastomas and a retinoblastoma cell line Y79 and (2) expression of N-myc gene is highly elevated in most of the retinoblastomas examined. This finding suggests that N-myc gene may have a primary role in the turaorigenesis of retinoblastoma.