Induced neuroblastoma cell differentiation, associated with transient HES-1 activity and reduced HASH-1 expression, is inhibited by Notch1

Neuroblastoma is a childhood tumor that originates from the sympathetic ner vous system. The tumor cells have embryonic features, presumably as a conse quence of an impaired capacity to respond to signals and transcriptional co ntrol mechanisms operating during normal differentiation. Two basic helix-l oop-helix transcription factors, human achaete-scute homologue-1 (HASH-1) a nd hairy/enhancer of split homologue-1 (HES-1), are crucial for proper deve lopment of some neuronal cells. Here, their potential roles during sympathe tic differentiation of human neuroblastoma cells have been investigated. In all tested protocols for induction of differentiation of SH-SY5Y and SK-N- BE(2) neuroblastoma cells, HASH-1 expression was rapidly decreased with a c oncomitant, often transient, increase in HES-1 expression. In gel mobility shift assays, using extracts from neuroblastoma cells, HES-1 bound to an ol igonucleotide corresponding to a sequence in the HASH-1 promoter including the so-called N-box, suggesting that the transiently increased HES-1 activi ty in differentiating neuroblastoma cells is involved in down-regulation of HASH-1. Constitutive expression of the intracellular domain of Notch 1, wh ich activates the HES-1 promoter in SH-SY5Y cells, inhibited spontaneous an d induced morphological differentiation of these neuroblastoma cells. Our d ata show that functional sympathetic neuronal differentiation of neuroblast oma cells is associated with transient activation of HES-1 and down-regulat ion of HASH-I expression. Int. J. Cancer 88:401-410, 2000. (C) 2000 Wiley-L iss, Inc.