Expression of Rap1GAP and its methylation status in papillary thyroid carcinoma / 中华内分泌代谢杂志

ABSTRACT

The expression of Rap1 GAP protein was detected in 69 cases of papillary thyroid carcinoma and adjacent normal thyroid tissues with immunohistochemistry method.Methylation of Rapl GAP gene was analyzed by methylation-specific-PCR (MSP) in these tissues.The immunohistochemistry results indicated that the Rap1GAP protein was down-regulated in tumor tissues of 54 ( 78％ ) cases compared with normal thyroid tissues.Statistical analysis demonstrated that the decreased level of Rap1 GAP protein expression was significantly correlated with the tumor stage T according to American Joint Committee on Cancer ( AJCC,P =0.043 ).The MSP results demonstrated that 46 cases of Rap1GAP gene methylation were detected in 54 cases with down-regulated expression of Rap1GAP (66.7％),but only 1 case of methylation was found in 15 cases without obvious change of Rap1GAP expression (6.67％),showing significant difference ( P＜0.01 ).There was no methylation in normal thyroid tissues.These results suggest that raised methylation of promoter region may contribute to the low expression of Rap1GAP protein in papillary thyroid carcinoma.