粪便DNA中X染色体连锁凋亡抑制蛋白相关因子1基因启动子甲基化状态在结直肠癌筛查中的应用研究

Application of stool DNA X-linked apoptosis inhibitory factor 1 gene promoter methylation in screening colorectal cancer

目的以粪便DNA中x染色体连锁凋亡抑制蛋白相关因子（XAF）1基因启动子区域的甲基化状态为靶目标，建立新的有效的筛查结直肠癌的方法。方法收集需做肠镜检查患者自然排泄粪便，经肠镜或病理学检查确诊后，分为3组，结直肠正常组45例，结直肠腺瘤组30例，结直肠腺癌组24例。使用QIAampDNAStoolMiniKit自粪便抽提人DNA。应用甲基化特异性的PCR（MSP）检测粪便DNA中XAFl基因启动子区域甲基化状态。结果经genomic—DNAPCR，证实所提取DNA均含有人基因组DNA。经MSP检测，正常组存在高甲基化15例，阳性率33．33％；腺瘤组18例，阳性率60．00％；腺癌组15例，阳性率62．50％，腺瘤组、腺癌组与正常组比较差异有统计学意义（P〈0．05），但腺瘤组与腺癌组差异无统计学意义（P〉0．05）。结论使用Qiagen试剂盒抽提粪便中人DNA的方法比较稳定。以粪便DNA中XAFl基因启动子区域甲基化状态为靶目标进行结直肠肿瘤的早期诊断，敏感度、特异度较高，但尚需要大样本研究进一步验证。

Objective To establish the methodology for efficient screening of colorectal cancer （CRC） via detection of stool DNA methylation of X- linked apoptosis inhibitory factor （XAF） 1 gene promoter. Methods Stool specimens were obtained from patients who underwent enteroscopy followed by allocation to normal control group （n------~5） , colorectal adenoma group （n=30） and colorectal adenocarcinoma group （n=24） , based on enteroscopic and pathological diagnosis. The methylation-specific PCR （MSP） technique was employed to detect methylation in promoter region of XAF1 gene extracted from stool DNA. Results Human geneome DNA was obtained from all the extracted DNA specimens. Methylation, based on MSP technique, was up-regulated in 15 cases of normal controls （positive rate： 33.3% ） and 18 cases of colorectal adenoma （positive rate： 60.0% ）（P〈0.05） and 15 cases of colorectal adenocarcinoma （positive rate： 62.5% ） （P〈0.05 as compared with normal controls）. However, the difference between patients with colorectal adenocareinoma and adenoma was not significant （P〉0.05）. Condusions The QIAamp DNA Stool Mini Kit provides efficient and stable purification of human DNA from stool samples. Detection of stool DNA methylation status of XAF1 gene promoter may provide high sensitivity and specificity in screening colorectal neoplasms, but fruther study is still needed to verify.