Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China.
Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR, China.
Clin Chem. 2018 Aug;64(8):1239-1249. doi: 10.1373/clinchem.2018.290304. Epub 2018 Jun 14.
Measurement of DNA derived from different tissues in the circulating DNA pool can provide important information regarding the presence of many pathological conditions. However, existing methods involving genome-wide bisulfite sequencing are relatively expensive and may present challenges for large-scale analysis.
Through identifying differentially methylated regions in the liver and colon compared with other tissues, we identified 2 markers and developed corresponding droplet digital PCR assays. Plasma concentrations of liver-derived and colon-derived DNA were measured for 13 liver transplant recipients, 40 liver cancer patients, and 62 colorectal cancer (CRC) patients (27 with and 35 without liver metastases).
In liver transplant recipients, the fractional concentration of liver-derived DNA measured using the liver-specific methylation marker and donor-specific alleles showed good correlation (Pearson = 0.99). In liver cancer patients, the concentration of liver-derived DNA correlated positively with the maximal dimension of the tumor (Spearman = 0.74). In CRC patients with and without liver metastasis, the plasma concentrations of colon-derived DNA (median, 138 copies/mL and 4 copies/mL, respectively) were increased compared with the 30 healthy controls (26 had undetectable concentrations). The absolute concentration of liver-derived DNA provided a better differentiation between CRC patients with and without liver metastasis compared with the fractional concentration (area under ROC curve, 0.85 vs 0.75).
Quantitative analysis of plasma DNA with tissue-specific methylation patterns using droplet digital PCR is applicable for the investigation of cancers and assessing organ transplantation. This approach is useful for differentiating patients with and without metastases to other organs.
循环 DNA 池中的不同组织来源的 DNA 测量可提供有关许多病理状况存在的重要信息。然而，涉及全基因组亚硫酸氢盐测序的现有方法相对昂贵，并且可能对大规模分析提出挑战。
通过比较肝脏和结肠与其他组织，我们鉴定出 2 个标记物，并开发了相应的液滴数字 PCR 检测。对 13 例肝移植受者、40 例肝癌患者和 62 例结直肠癌（CRC）患者（27 例伴肝转移和 35 例无肝转移）进行了肝源性和结肠源性 DNA 的血浆浓度测量。
在肝移植受者中，使用肝特异性甲基化标记物和供体特异性等位基因测量的肝源性 DNA 的分数浓度具有良好的相关性（Pearson = 0.99）。在肝癌患者中，肝源性 DNA 的浓度与肿瘤的最大直径呈正相关（Spearman = 0.74）。在伴有和不伴有肝转移的 CRC 患者中，结肠源性 DNA 的血浆浓度（中位数分别为 138 拷贝/mL 和 4 拷贝/mL）与 30 例健康对照者相比均升高（26 例为不可检测浓度）。与分数浓度相比，肝源性 DNA 的绝对浓度在区分伴有和不伴有肝转移的 CRC 患者方面提供了更好的区分（ROC 曲线下面积，0.85 与 0.75）。
使用液滴数字 PCR 对具有组织特异性甲基化模式的血浆 DNA 进行定量分析适用于癌症的研究和评估器官移植。这种方法对于区分伴有和不伴有其他器官转移的患者是有用的。
