贲门腺癌中RASSF1A基因的甲基化状态及表达

Expression and Methylation Status of RASSF1A Gene in Gastric Cardiac Adenocarcinoma

目的研究贲门腺癌(gastric cardiac adenocarcinoma,GCA)中RASSF1A基因的甲基化状态及其蛋白表达情况。方法分别应用甲基化特异性PCR(MSP)、RT-PCR及免疫组织化学SP法检测贲门癌组织及相应癌旁组织的RASSF1A甲基化情况和mRNA水平及蛋白表达情况。结果92例贲门癌组织中有54例发生了甲基化,甲基化率为58.7%,显著高于癌旁正常组织(P<0.01)。Ⅲ期和Ⅳ期贲门癌患者中RASSF1A基因发生甲基化的比率显著高于Ⅰ期和Ⅱ期患者(P<0.05)。92例贲门癌组织中有43例RASSF1A基因蛋白表达阴性,与相应癌旁正常组织相比有显著性差异(P<0.01)。Ⅲ期和Ⅳ期贲门癌RASSF1A基因蛋白表达显著低于Ⅰ期和Ⅱ期患者(P<0.05)。发生甲基化的贲门癌组织中RASSF1A的mRNA水平的表达显著低于未发生甲基化的贲门癌组织(P<0.01)。结论RASSF1A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 and expression of RASSFIA gene in gastric cardiac adenocarcinoma（GCA）. Methods We used MSP approach, RT-PCR and immunohistochemistry method respectively to examine the methylation status of the 5＇ CpG island of RASSF1A gene and its expression at mRNA and protein levels in tumors and corresponding normal tissues. Results RASSFIA promoter was methylated in 54/92 （58.7%） tumor specimens, which was significantly higher than that in corresponding normal tissues（P〈0. 001）. Methylation frequencies of stage Ⅲ and Ⅳtumor tissues were significantly higher than those in stage Ⅰand Ⅱtumor tissues（P〈0. 05）. By immunostaining,43/92 （46.7%） tumor tissues demonstrated heterogeneous, positive immunostaining of tumor tissues. The expression of RASSF1A at mRNA levels were significantly reduced compared to matched normal tissues（P d0. 001, respectively）. Protein expressions of RASSF1A in stage Ⅲand 1V tumor tissues were significantly lower than those in stage Ⅰand Ⅱtumor tissues（P〈0. 05）. RASSF1A mRNA expressions in meth- ylation group of GCA were significantly different from those in unmethylation group（P〈0. 001）. Conclusion Epigenetic silencing of RASSF1A gene expression by promoter hypermethylation may play an important role in gastric cardiac adenocarcinoma.