Promoter hypermethylation contributes to the frequent suppression of the CDK10 gene in human nasopharyngeal carcinomas

Background

Previous studies have shown a down-regulation of the gene encoding cyclin-dependent kinase 10 (CDK10) in hepatocellular carcinomas. Here we provide evidence that down-regulation of the CDK10 gene is mediated by promoter hypermethylation in primary human nasopharyngeal carcinomas (NPC) and NPC-derived cell lines.

Methods

RT-PCR, Western blotting, methylation-specific PCR and bisulfite sequencing were performed to assess the expression and methylation status of the CDK10 gene in primary NPC samples, NPC-derived cell lines and patient-derived peripheral blood samples. The NPC-derived cell line CNE-2 was selected for treatment with a methylation inhibitor to restore CDK10 expression. In addition, cell proliferation, invasion and colony formation assays were performed to assess the inhibitory effects of ectopic CDK10 expression in CNE-2 cells.

Results

Down-regulation of CDK10 expression in primary NPC samples (23/40, 57.5 %) was found to be significantly correlated with the methylation status of its promoter CpG island (21/40, 52.5 %). Demethylation by 5-aza-dC treatment led to reactivation of the CDK10 gene in the CNE-2 cell line. Additionally, exogenous expression of CDK10 in CNE-2 cells strongly suppressed its growth, invasion and colony formation capacities. The high sensitivity (15/40, 37.5 %) and specificity (0 % false positives) of detecting CDK10 promoter hypermethylation in NPC patient-derived peripheral blood samples suggest that it could be employed as an epigenetic marker for noninvasive cancer diagnosis and recurrence screening.

Conclusion

Our findings implicate that aberrant methylation of the CDK10 gene promoter occurs frequently in NPC, and that reactivation of CDK10 might be utilized as a novel epigenetic strategy for the treatment of NPC patients.