No abstract

Neuroblastoma is a sympathetic nervous system tumour whose degree of malignancy, prognosis and therapy resistance has been associated with the amplification of MYCN oncogene. However, the molecular pathway responsible for such resistance is unknown. To contribute addressing this issue, in this study, we have compared the vulnerability of four human neuroblastoma cell lines differentially amplifying MYCN, namely SK-N-BE-2 and IMR-32 (MYCN-amplified cells) and SH-SY5Y and SK-N-SH (MCYN-non-amplified cells), to H 2 O 2 -mediated apoptotic death. We found that the high resistance of the MYCN-amplified neuroblastoma cells against oxidative damage can be accounted for by their greater expression of both the mRNA and protein of the catalytic subunit of glutamate-cysteine ligase (GCL cat ), the ratelimiting step in GSH biosynthesis. Furthermore, we found that MYCN directly binds to an E-box containing GCL cat promoter and that over-expression of MYCN in MYCN-non-amplified cells stimulated GCL cat expression and provided resistance to oxidative damage; whereas knock down of MYCN in MYCNamplified cells decreased GCL cat expression and sensitized them to oxidative damage. Finally, GCL cat knock down enhanced the vulnerability of MYCN-amplified cells to oxidative damage. These results demonstrate that regulation of GCL cat by MYCN accounts for the survival of neuroblastoma cells against oxidative damage, and suggest that GCL should be considered a potential therapeutic target for the treatment of MYCN-amplified neuroblastoma.