血浆APC和DCC基因启动子甲基化测定在肺癌早期诊断中的应用

Clinical utility of plasma APC and DCC genes promoter hypermethylation in the early diagnosis of lung cancer

目的:检测肺癌患者血浆游离DNA中腺瘤样结肠息肉易感基因(adenomatous polyposis coli,APC)和结直肠癌缺失基因(deleted in colorectal carcinoma,DCC)启动子甲基化状态并分析其在肺癌诊断中的意义。方法:应用甲基化特异性PCR(methylation specific PCR,MSP)法,检测70例肺癌患者、40例肺良性病变患者和30例健康志愿者血浆APC和DCC两个基因启动子区甲基化状态。同时测定血清癌胚抗原,并与血浆APC和DCC基因甲基化测定结果进行比较。结果:(1)肺癌患者血浆标本中APC、DCC基因启动子甲基化阳性检出率分别为25.71%(18/70)、35.71%(25/70),接近于血清癌胚抗原的阳性率(37.14%);肺良性病变患者血浆中APC、DCC基因启动子甲基化阳性率分别为2.50%(1/40)、7.50%(3/40);健康志愿者血浆中这两个基因未检测出甲基化;3组间两基因甲基化阳性率间的差异有统计学意义(P均<0.05);(2)APC和DCC两个基因甲基化联合检测诊断肺癌的灵敏度为51.43%,特异度为90.00%;血浆APC、DCC基因甲基化和血清癌胚抗原三项联合检测可明显提高肺癌诊断的灵敏度(68.57%),但特异度轻微下降(82.50%);(3)APC和DCC基因启动子甲基化与肺癌患者年龄、性别、吸烟指数、组织学类型、分化程度、临床分期及淋巴结转移无明显相关性(P>0.05)。结论:外周血浆中APC、DCC基因甲基化有望成为诊断肺癌的肿瘤标志物,在肺癌早期诊断中具有潜在的应用价值。

Objective: To evaluate clinical utility of the genes promoter hypermethylation of adenomatous polyposis coli( APC) and deleted in colorectal carcinoma( DCC) in plasma for the early diagnosis of lung cancer. Methods: A methylation specific PCR( MSP) was used to detect the status of APC and DCC promoter hypermethylation in plasma DNA from 70 lung cancer patients,40 benign lung disease patients and30 healthy volunteers. Serum carcinoembryonic antigen( CEA) was detected simultaneously and compared with the plasma APC and DCC genes methylation. Results:( 1) The positive rates of plasma APC and DCC genes promoter methylation in lung cancer patients were 25. 71%( 18 /70) and 35. 71%( 25 /70),respectively,which were similar to the positive rate of serum CEA( 37. 14%). Whereas the positive rates of APC and DCC genes methylation in plasma of benign lung disease patients were 2. 50%( 1 /40) and 7. 50%( 3 /40),respectively. The two genes methylation in plasma was not found in healthy volunteers. There was a significant difference between patients with lung cancer and patients with benign lung disease in plasma APC and DCC genes promoter methylation( P < 0. 05);( 2) Combination of plasma APC and DCC genes methylation raised sensitivity to 51. 43%,with 90. 00% specificity for the diagnosis of lung cancer. Com-bined use of APC,DCC and CEA achieved sensitivity of 68. 57%,with slight decrease of specificity( 82. 50%);( 3) APC and DCC genes promoter methylation in lung cancer patients were not associated with the age,sex,smoking index,pathological types,the degree of tumor differentiation,clinical staging and lymph metastasis of patients with lung cancer. Conclusion: Plasma APC and DCC genes methylation might be two potential candidates as tumor markers of lung cancer. The detections of the two genes methylation may be a complementary tool for the early diagnosis of lung cancer.