The Role of CpG24 Hyper-Methylation on the Down-Regulation of Rap1Gap in Papillary Thyroid Cancer | Insight Medical Publishing

Background: Thyroid tumors may arise following hypermethylation in the regulatory region of suppressor genes such as Rap1Gap. In this study, we aimed to investigate the gene expression of Rap1Gap and DNA methylation pattern of CpG24 in Iranian patients with papillary thyroid cancer (PTC). Materials and methods: The study was done on 132 individuals who had undergone thyroidectomy. Rap1Gap mRNA expression was examined by an optimized two-step real-time quantitative PCR assay. DNA methylation pattern of CpG24 was examined using the methylation-specific PCR (MSP). B-CPAP and SW1736 cell lines were treated with 5-aza-2,-deoxycytidine (5-Aza) in an attempt to demethylate the CpG24 in the regulatory region of the target gene. Results: The results of qRT-PCR indicated a no significant decrease of Rap1Gap gene expression level in PTC individuals compared with control group (fold change: 0.98; p=0.99). CpG24 was hyper-methylated in 82.3% of individuals with PTC, in 79.1% of benign nodules and only in 14% of normal thyroid tissues (p<0.001). The modest CpG24 de-methylation was achieved by 15 μM of 5-Aza in both cell lines. Conclusion: It is concluded that aberrant DNA methylation in the CpG24 region, independent of Rap1Gap gene expression, could be determined as an epigenetic marker for papillary thyroid cancer.