miR-204 mediates post-transcriptional down-regulation of PHOX2B gene expression in neuroblastoma cells.

Neuroblastoma (NB) is a rare childhood cancer of the peripheral sympathetic nervous system and accounts for approximately 10% of all pediatric tumors. Heterozygous PHOX2B mutations have been found in association with NB development in familial, sporadic and syndromic cases. In addition, the PHOX2B gene is widely over-expressed both in tumor samples and NB cell lines. Post-transcriptional gene regulation is known to be involved in mRNA stability and, in NB, microRNAs (miRNAs) seem to be responsible for altered expression of genes driving differentiation, apoptosis, and migration. To assess the possible impact of post-transcriptional regulation in NB cell lines, we have focused on the PHOX2B mRNA stability by both in silico analysis and functional studies on its 3'untranslated region (3'UTR). PHOX2B gene expression has resulted under post-transcriptional control, as suggested by: i) instability of PHOX2B mRNA, demonstrated by short mRNA half-life levels in both IMR32 and LAN-1 cell lines, ii) role of the PHOX2B-3'UTR, confirmed by the activity of proper reporter constructs, and iii) miRNA-204, shown to enhance the PHOX2B 3'UTR mediated down-regulation of the reporter construct activity. Finally, miRNA-204 has resulted to decrease the stability of the PHOX2B mRNA at different extents in the presence of different SNP rs1063611 alleles. Therefore, post-transcriptional down-regulation of the PHOX2B gene takes place in NB cell lines and miRNA-204 participates in such a 3'UTR mediated control.