Inhibition of cyclin-dependent kinase 1-induced cell death in neuroblastoma cells through the microRNA-34a-MYCN-survivin pathway.

BACKGROUND: Neuroblastoma is the most common pediatric solid extracranial malignancy. Increased expression of MYCN, a member of Myc family, is associated with a poor prognosis in patients with neuroblastoma. Cyclin-dependent kinase 1 (CDK1) is known to be critical to the survival of Myc-overexpressing neoplasms. In this study, we investigated the effects of CDK1 inhibition on the viability of neuroblastoma cells and the underlying molecular mechanisms.
METHODS: We assessed the effects of CDK1 inhibitors on the viability of neuroblastoma cells and explored MYCN-associated mechanisms by using real-time reverse-transcription polymerase chain reaction, chromatin immunoprecipitation, and micro-RNA quantification.
RESULTS: CDK1 inhibitors induced cytotoxicity and apoptosis and decreased expression of MYCN and survivin in neuroblastoma cells. Knockdown of MYCN mRNA expression caused significant cell death and transcomplementation of MYCN increased cell viability in neuroblastoma cells treated with CDK1 inhibitors. Furthermore, MYCN mRNA was inhibited by CDK1 inhibitor at the posttranscriptional level. The expression of survivin was also responsive to the change of MYCN levels, and according to the chromatin immunoprecipitation assay, MYCN bound the promoter region of the survivin gene. CDK1 inhibition caused elevation of microRNA-34a (miR-34a), and anti-miR-34a not only restored the expression of MYCN but also increased cell survival of neuroblastoma cells treated with CDK1 inhibitor.
CONCLUSION: CDK1 inhibition-induced cell death was dependent, although not completely, on the decreased level of MYCN- and miR-34a-mediated, CDK1 inhibition-induced down-regulation of MYCN, which thereby decreased the transcriptional activation of MYCN on the survivin promoter. We propose that CDK1 inhibition-induced cell death of neuroblastoma cells occurs through the miR-34a-MYCN-survivin pathway.