WWOX基因在贲门腺癌中的异常甲基化及其表达

目的:探讨贲门腺癌(gastric cardia adenocarcinoma,GCA)中WWOX( WW domain-containing oxidoreductase)基因启动子区及第1外显子区的甲基化状态及其对表达的影响,并分析贲门腺癌中WWOX与Smad4(mothers against decapentaplegic homolog 4)蛋白表达之间的关系.方法:分别应用甲基化特异性PCR和免疫组织化学法检测贲门腺癌组织及其相应癌旁组织中WWOX基因的甲基化和蛋白的表达情况:应用免疫组织化学法检测贲门腺癌组织及其相应癌旁组织中Smad4蛋白的表达.结果:贲门腺癌组织中WWOX基因启动子区(- 382～- 41 bp)及第1外显子区(- 27～+344 bp)的甲基化率26.4％ (33/125)和23.2％ (29/125)]显著高于其相应的癌旁常组织(0％和0％)(P＜0.01),并与贲门腺癌TNM分期和上消化系统肿瘤家族史有关(P＜0.05).贲门腺癌组织中WWOX蛋白的表达阳性率显著低于相应癌旁组织(P＜0.01),WWOX蛋白的表达与WWOX启动子区和第1外显子区甲基化状态之间呈负相关(r=-0.216,r=-0.255,P＜0.05).贲门腺癌组织中Smad4蛋白表达的阳性率(47.2％)显著低于相应癌旁组织(94.4％)(P＜0.01),且与WWOX在贲门腺癌中的表达呈明显的正相关(r=0.622,P＜0.01).结论:WWOX基因启动子区及第1外显子区的高甲基化导致的基因表达下调可能在贲门腺癌中发挥重要作用.

Aberrant methylation and expression of WWOX gene in gastric cardia adenocarcinoma

Objective: To investigate the methylation of promoter and exon 1 regions of WW domain-containing oxidoreductase (WWOX) gene and the expression of WWOX gene in gastric cardia adenocarcinoma(GCA), and to evaluate the correlation between the expressions of WWOX protein and mothers against decapentaplegic homolog 4 (Smad4) protein. Methods: The methylation of WWOX gene in GCA tissues and the adjacent normal tissues was detected by methylation-specific polymerase chain reaction, and the expressions of WWOX and Smad4 proteins were determined by immunohistochemistry method. Results: The methylation rates of promoter (-382 to -41 bp) and exon 1 (-27 to +344 bp) regions of WWOX gene were 26.4% (33/125) and 23.2% (29/125) in GCA tissues, respectively, which were significantly higher than those in the adjacent normal tissues (0% and 0%) (P < 0.01). The methylation frequency of WWOX gene was associated with TNM stage and family history of upper gastrointestinal cancers (P < 0.05). The positive rate of WWOX protein in GCA tissues was lower than that in the adjacent normal tissues (P < 0.01). The expression of WWOX protein was negatively associated with the methylation status of promoter and exon 1 regions of WWOX gene (r = -0.216, r = -0.255; P < 0.05). The positive rate of Smad4 protein in GCA tissues (47.2%) was lower than that in the adjacent normal tissues (94.4%) (P < 0.01), and the expression of Smad4 protein was positively associated with the expression of WWOX protein in GCA tissues (r = 0.622, P < 0.01). Conclusion: Decreased expression of WWOX gene induced by hypermethylation of promoter and exon 1 regions may play an important role in the development of GCA.