Wnt拮抗因子SFRP2在胃癌中的甲基化和异常表达

Methylation and aberrant expression of Wnt antagonist SFRP2 in gastric cancer

目的:检测Wnt拮抗因子分泌型Frizzled相关蛋白2(SFRP2)在胃癌中的甲基化和表达状态,探讨SFRP2在胃癌发病机制中的作用。方法:采用甲基化特异性PCR(MSP)检测SFRP2在胃癌中的甲基化状态,采用即时定量PCR检测SFRP2在胃癌组织标本及其癌旁正常组织中的表达。采用逆转录PCR(RT-PCR)和Western blotting检测SFRP2在胃癌细胞系中的表达。结果:在胃癌组织中,有26例(65%)检出SFRP2甲基化,在其相应的癌旁组织中,有3例(7.5%)检出SFRP2甲基化。SFRP2在胃癌组织中的甲基化频率显著高于癌旁正常组织(χ2=28.614,P<0.01)。SFRP2mRNA在胃癌组织中表达显著低于癌旁正常组织(P<0.01)。在胃癌细胞系SGC-7901、AGS和NCI-N87中,SFRP2在AGS和NCI-N87发生甲基化,表达消失,而在SGC-7901中未发生甲基化,存在表达。使用去甲基化试剂5-氮杂-2-脱氧胞苷酸(DAC)处理AGS和NCI-N87后,SFRP2重新出现表达。结论:SFRP2在胃癌中存在表达下调,其主要由SFRP2发生甲基化所致。结果提示,SFRP2甲基化及表达下调参与了部分胃癌的发病过程。

AIM ： To determine the methylation and expression of Wnt antagonist secreted Frizzled - related protein -2 （SFRP2） in gastric cancer and to explore the role of SFRP2 in gastric carcinogenesis. METHODS： Methylation status of SFRP2 was detected by methylation - specific PCR （MSP）. Real - time PCR was used to determine the expression of SFRP2 in gastric cancers and matched cancer adjacent normal tissues. SFRP2 expression in gastric cancer cell lines was determined by reverse -transcriptional PCR （RT- PCR） and Western blotting. RESULTS： SFRP2 methylatian was found in 26 （65%） gastric cancers and in 3 （7.5%） matched cancer adjacent normal tissues. The frequency of methylation for SFRP2 was significantly higher in gastric cancers than that in matched normal tissues （χ^2 = 28. 614, P 〈 0. 01 ）. Level of SFRP2 expression in gastric cancers was significantly lower than that in matched normal tissues （ P 〈 0. O1 ）. SFRF2 was methylated and not expressed in gastric cell line AGS and NCI - N87. However, SFRF2 was expressed and not methylated in gastric cell line SGC - 7901. After AGS and NCI - N87 were treated with demethylating agent 5 - aza - 2＇ - deoxycytidine （DAC）, SFRP2 expression was restored in these two cell lines. CONCLUSION： SFRP2 is dowmregulated in gastric cancer, which is caused by SFRP2 methylation. The results suggest that methylation and aberrant expression of SFRP2 play a role in gastric carcinogenesis.