Analysis of Circulating Tumor Cells Laboratory, Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, Athens, Greece.
Clin Chem. 2013 Jan;59(1):270-9. doi: 10.1373/clinchem.2012.191551. Epub 2012 Nov 7.
Detection of circulating tumor cells (CTCs) and cell-free DNA (cfDNA) in the peripheral blood of patients with solid tumors has been widely studied for the early detection of metastatic spread. We evaluated whether there was an association between the origin of cfDNA and CTCs. We investigated whether SRY (sex determining region Y)-box 17 (SOX17) promoter methylation in CTCs was associated with the methylation pattern of this gene in matched cfDNA isolated from plasma of patients with breast cancer.
We examined SOX17 methylation in 79 primary breast tumors, in 114 paired samples of DNA isolated from CTCs and cfDNA, and in 60 healthy individuals. Isolated DNA was modified by sodium bisulfite and subjected to methylation specific PCR.
The SOX17 promoter was methylated in 68 (86.0%) of 79 of primary breast tumors. In CTCs, SOX17 was methylated in 19 (34.5%) of 55 patients with early breast cancer, 27 (45.8%) of 59 patients with metastatic cancer, and 1 (4.3%) of 23 healthy individuals, whereas in matched cfDNA SOX17 was methylated in 19 (34.5%) of 55, 24 (40.7%) of 59, and 1 (2.0%) of 49 of these same groups, respectively. There was a significant correlation between SOX17 methylation in cfDNA and CTCs in patients with early breast cancer (P = 0.008), but not in patients with verified metastasis (P = 0.283).
The SOX17 promoter is highly methylated in primary breast tumors, in CTCs isolated from patients with breast cancer, and in corresponding cfDNA samples. Our findings indicate a direct connection between the presence of CTCs and cfDNA in patients with operable breast cancer, after surgical removal of the primary tumor.
在实体瘤患者的外周血中检测循环肿瘤细胞（CTCs）和无细胞 DNA（cfDNA）已被广泛研究，用于早期检测转移扩散。我们评估了 cfDNA 和 CTCs 的起源之间是否存在关联。我们研究了 CTC 中性别决定区 Y 框 17（SOX17）启动子的甲基化是否与从乳腺癌患者血浆中分离的匹配 cfDNA 中该基因的甲基化模式相关。
我们检查了 79 例原发性乳腺癌、114 例 CTCs 和 cfDNA 分离的 DNA 配对样本以及 60 例健康个体中 SOX17 的甲基化。分离的 DNA 经亚硫酸氢钠修饰，并用甲基化特异性 PCR 进行分析。
68 例（86.0%）原发性乳腺癌的 SOX17 启动子发生甲基化。在 55 例早期乳腺癌患者的 CTCs 中，SOX17 甲基化 19 例（34.5%），59 例转移性癌症患者中 27 例（45.8%），23 例健康个体中 1 例（4.3%），而在匹配的 cfDNA 中，SOX17 甲基化分别为 55 例中的 19 例（34.5%）、59 例中的 24 例（40.7%）和 49 例中的 1 例（2.0%）。在早期乳腺癌患者中，cfDNA 和 CTCs 中 SOX17 的甲基化之间存在显著相关性（P = 0.008），但在已确诊转移的患者中无相关性（P = 0.283）。
SOX17 启动子在原发性乳腺癌、从乳腺癌患者中分离的 CTCs 以及相应的 cfDNA 样本中高度甲基化。我们的发现表明，在原发性肿瘤切除后，可手术乳腺癌患者的 CTCs 和 cfDNA 之间存在直接联系。
