贲门腺癌中转化生长因子βⅡ型受体基因启动子区高甲基化及其与TGF-β1表达的相关性分析

Promoter methylation of transforming growth factor(TGF) beta receptor type Ⅱ gene and the expression of TGF-β1 in gastric cardia adenocarcinoma:a correlation analysis

目的:探讨贲门腺癌中转化生长因子-βⅡ型受体(transforming growth factor-beta receptor type 2,TGFBR2)基因启动子区的甲基化状态及其与TGF-β1蛋白表达之间的相关性。方法:分别应用甲基化特异性PCR(methylation-specific PCR,MSP)、RT-PCR和免疫组织化学法检测贲门腺癌组织及相应癌旁组织中TGFBR2基因启动子区甲基化情况、TGFBR2 mRNA和蛋白表达情况,并应用免疫组织化学法检测相应组织中TGF-β1的蛋白表达情况。结果:TGFBR2基因在贲门腺癌组织中甲基化率为47.3%(52/110),显著高于癌旁正常组织(P<0.01);Ⅲ期和Ⅳ期贲门癌患者中TGFBR2基因发生甲基化的比率显著高于Ⅰ期和Ⅱ期患者(P<0.05);TGFBR2基因在高、中、低分化的贲门癌组织中甲基化率差异亦有统计学意义(P<0.05)。贲门癌组织中TGFBR2 mRNA及蛋白表达显著低于癌旁正常组织(P<0.05)且与其甲基化状态之间有明显的相关性(P<0.01)。TGF-β1在贲门癌组织中的表达(65.5%)明显升高,与相应癌旁正常组织相比差异有统计学意义(P<0.01),且随着肿瘤分期的增高和肿瘤分化程度的降低,TGF-β1的阳性表达率明显升高(P<0.05)。TGFBR2和TGF-β1蛋白在贲门腺癌中的表达呈明显的负相关(P<0.05)。结论:TGFBR2受体基因启动子区的高甲基化及其TGF-β1的过表达可能均参与了贲门腺癌的发生发展过程。TGFBR2基因启动子区发生甲基化导致的基因沉默可能是贲门腺癌发生的机制之一。

Objective:To investigate the promoter methylation status of transforming growth factor beta receptor type 2 gene(TGFBR2) in gastric cardia adenocarcinoma(GCA) and its correlation with TGF-β1 protein expression.Methods:The methylation-specific PCR(MSP),RT-PCR,and immunohistochemistry methods were used to examine the methylation status of the 5'-CpG island,mRNA transcription,and protein expression of TGFBR2 in GCA tissues and adjacent normal tissues,respectively.Immunohistochemistry method was used to detect the protein expression of TGF-β1 in tumors and corresponding normal tissues.Results:TGFBR2 gene was methylated in 52/110(47.3%) tumor specimens,which was significantly higher than that in corresponding normal tissues(P<0.01).The methylation frequencies of TGFBR2 in stages Ⅲ and Ⅳ tumor tissues were significantly higher than those in stagesⅠandⅡtumor tissues(P<0.05) and the methylation frequencies in the high,moderate,and low differentiation groups were significantly different(P<0.05).TGFBR2 mRNA and protein expressions in tumor tissues were significantly lower than those in corresponding normal tissues and were correlated with its methylation status(P<0.01).The positive immunostaining of TGF-β1 was greatly increased(65.5%,72/110) in GCA tissues,which was significantly higher than that in corresponding normal tissues(P<0.01).The positive protein expression of TGF-β1 was significantly increased with the increase in the GCA stage and decrease in GCA differentiation(P<0.05).The protein expression of TGFBR2 was inversely correlated with TGF-β1 expression in GCA(P<0.05).Conclusion:Promoter hypermethylation of TGFBR2 and the over expression of TGF-β1 protein may play important roles in the initiation and progression of GCA.Gene silencing induced by promoter hypermethylation of TGFBR2 may be one of the mechanisms for the initiation of GCA.