目的：通过建立血浆游离DNA中肿瘤高甲基化基因1（hypermethylated in cancer 1, HIC-1）甲基化检测技术，评估其作为体液活检诊断方法在乳腺良恶性疾病鉴别中的价值。方法：收集35份乳腺疾病患者（其25例乳腺癌，10例乳腺良性疾病）及10份健康志愿者的血液样本，分离、提取血浆中的游离DNA。采用亚硫酸氢盐测序（bisulfite sequencing PCR，BSP）法，检测HIC-1基因启动子区域-636~-424 bp中16个CpG位点的甲基化水平。结果：在检测的16个CpG位点中，以-636~-617 bp中的4个位点甲基化最为明显。其中，乳腺癌组的这4个位点平均甲基化率为22.6%，而良性乳腺疾病组为8.5%，健康对照组为8.3%，3组间的差异有统计学意义（P<0.05）。进一步绘制受试者工作特征曲线（receiver operator characteristic curve, ROC曲线）进行分析，发现以这4个位点的平均甲基化率诊断乳腺癌时，其曲线下面积（area under the cure AUC）为0.794，证实其对乳腺癌具有一定的诊断价值。结论：检测血浆游离DNA中抑癌基因HIC-1启动子区甲基化水平，在乳腺癌诊断中有一定参考价值。

Objective: To establish a detection method for gene hypermethylated in cancer 1（HIC-1） methylation in cell-free DNA in peripheral blood and to evaluate its significance in diagnosis of benign and malignant breast tumors. Methods: The cell free DNA was extracted from 45 blood samples including breast disease patients and healthy volunteers. These DNA were treated with bisulfite and using Bisulfite Sequencing PCR(BSP) method to detect the methylation level of the 16 CpG sites in HIC-1 gene promoter region -636—-424 bp. Results: Of the breast cancer group, the methylation trend was obvious among the 4 sites in -636—-617 bp. Its average methylation rate was 22.6%. Frequency of methylation of HIC-1 gene promoter region was significantly higher in 25 patients with breast cancer compared with that in 10 benign tumor samples (22.6% vs 8.5%, P<0.05) and 10 healthy control samples (22.6% vs 8.3%, P<0.05). The ROC curve analysis showed that the area under curve（AUC） was 0.794, indicating a certain diagnostic value for breast cancer. Conclusions: The detection of HIC-1 gene promoter methylation in cell-free DNA has certain clinical significance in the diagnosis of breast cancer.