Smad4表达异常与结直肠癌的相关性研究

目的 探讨结直肠组织Smad4 mRNA及其蛋白表达水平变化、Smad4基因CpG岛异常甲基化与结直肠癌及其临床病理特征的关联性.方法 应用RT-PCR方法及测序、半定量RT-PCR方法、甲基化特异性PCR(MSP)技术和免疫组织化学方法,各自检测43例患者的结直肠癌组织、癌旁组织及30例结直肠腺瘤组织、12例健康人结肠黏膜组织.结果 43例结直肠癌组织中有25例(58.14%)Smad4 mRNA检测到阳性表达,其阳性表达率(58.14%)及表达水平(0.73±0.25)均低于相应的癌旁组织(88.37%,0.95±0.29)、腺瘤组织(90.63%,1.01±0.37)和健康人黏膜组织(100.00%,1.18±0.33),差异均有统计学意义(P＜0.05).Smad4基因启动子甲基化阳性率结直肠癌组织(60.53%)明显高于癌旁组织(27.03%)、腺瘤组织(25.00%)和健康人黏膜组织(16.67%),差异均有统计学意义(P＜0.05).Smad4蛋白表达的阳性率结直肠癌组织(44.19%)明显低于癌旁组织(81.40%)、腺瘤组织(87.50%)和健康人黏膜组织(91.67%),差异均有统计学意义(P＜0.05),并随着浸润深度加深和淋巴结转移,阳性率也随之下降.结论 Smad4的低表达与结直肠癌的发展、生物学行为和预后可能有关,可作为重要的生物学标志及病期评估的标志之一.

Low expression of Smad4 in colorectal cancer

Objective To determine the correlation between Smad4 mRNA,protein expression,abnormal methylation of CpG islands of Smad4 and colorectal cancer.Methods The expression of Smad4 in 43 cases of colorectal cancer and its adjacent tissue.30 cases of colorectal adenoma and 12 normal colon mucosa were analyzed by RT-PCR,sequencing,semi-quantitative RT-PCR,methylation-specific PCR(MSP)and immunohistochemistry.Results The mRNA expression of Smad4 was detected in 25 cases of colorectal cancer(58.14%),with expression levels at 0.73±0.25,which was significantly lower than those in corresponding adjacent tissues(88.37%,0.95±0.29),eolorectal adenoma(90.63%,1.01±0.37)and normal mucosa(100.00%,1.18 ±0.33)(P＜0.05).The positive rates of Smad4 gone promoter methylation in colorectal caner(60.53%)was significantly higher than that in other tissues(27.03%,25.00%and 16.67%,respectively,P＜0.05).The expression of Smad4 protein was significantly lower in colorectal cancer(44.19%)than that in other tissues(81.40%,87.50%,91.67%,respectively,P＜0.05),which was correlated with tumor invasion and lymph node metastasis.Conclusion Down-regulation of Smad4 expression may be associated with the development,the biological behavior and prognosis of colorectal cancer,and it can be an important biological marker in evaluation of disease progression.