To assess the increased expression of MDM2 mRNA in response to CHK1i, we performed RT-qPCR analysis in seven neuroblastoma cell lines: NB-39-nu, SMS-SAN, NBLS, CHP134, SH-SY5Y, SK-N-AS, and SK-N-BE treated with 1 and 5 μM PF-477736 for 24 hours or without PF-477736. This evidence concerns the gene MDM2 and neuroblastoma.