乳头状甲状腺癌抑癌基因TSHR、P16和RAS启动子甲基化研究

Study on the promoter hypermethylation of TSHR, P16, and RAS genes in human papillary thyroid carcinoma

目的研究促甲状腺激素受体（TSHR）、P16和RAS3个抑癌基因在乳头状甲状腺癌的表达，分析其启动子甲基化与肿瘤发生的关系。方法对50例乳头状甲状腺癌组织和32例对照组织（20例结节性甲状腺肿，12例甲状腺腺瘤）提取RNA后，以RT—PCR检测3个抑癌基因mRNA的表达情况，采用甲基化PCR（MSP）检测上述组织中3个抑癌基因启动子区甲基化的情况，并对3个抑癌基因甲基化和未甲基化的组织随机进行测序。结果50例乳头状甲状腺癌组织中，有34例（68．0％）TSHR基因、27例（54．0％）P16基因、30例（60．0％）RAS基因启动子发生了甲基化；32例对照组织中，有7例（21．9％）TSHR基因、5例（15．6％）P16基因、10例（31．3％）RAS基因启动子发生了甲基化；乳头状甲状腺癌组TSHR、P16、RAS基因启动子甲基化率均显著高于对照组（均P〈0．05）。TSHR、P16和RASmRNA在乳头状甲状腺癌中的表达量明显低于对照组织（0．41±0．11对0．63±0．08，0．51±0．17对0．72±0．22，0．56±0．10对0．67±0．16，均P〈0．05）。经DNA测序证实，3个抑癌基因启动子发生甲基化的其CpG岛碱基未发生改变，仍为CG；未发生甲基化的碱基由CG变为TG。结论3个抑癌基因启动子甲基化与乳头状甲状腺癌的发生和发展均相关。

Objective To study the expressions of the tumor suppressor gene TSH receptor（TSHR） ,P16, and RAS in papillary thyroid carcinoma （PTC） , and the correlation between the occurrence of tumor and the aberrant promoter hypermethylation of three tumor suppressor genes. Methods RT-PCR was used to detect the mRNA expression of three tumor suppressor genes in tissues of 50 cases of PTC,20 cases of nodular goiter,and 12 cases of thyroid adenoma. The promoter methylation status of three tumor suppressor genes was examined by methylation-specific PCR technique（MSP）. Gene sequencing was used to test if the hypermethylation existed in the promoter of three tumor suppressor genes. Results In 68.0% （34/50）TSHR gene,54.0% （27/50）P16 gene,and 60.0% （30/50） RAS gene in PTCs, hypermethylation in promoter region was detected, the respective results 21.9% （7/32）, 15.6% （5/32）, and 31.3% （ 10/32 ）were found in control tissues. The rates of the three genes with promoter hypermethylation in PTC were significantly higher than those in control tissues（ all P〈0.05 ）. The mRNA expressions of TSHR,P16,and RAS were significantly lower in PTC than those in control tissues （0.41± 0.11 vs0.63±0.08,0.51±0. 17 vs 0.72±0.22,0.56±0. 10 vs 0.67±0. 16, all P〈0.05）. The sequencing confirmed that there was CG to TG transmission in the promoters of three tumor suppressor genes. Conclusions The methylation of three tumor suppressor genes in promoter region is a common molecule event and may be involved in the genesis and development of human PTC.