Division of Biostatistics and Epidemiology, University of Massachusetts, Amherst, MA, USA.
Epigenetics. 2012 Nov;7(11):1258-67. doi: 10.4161/epi.22220. Epub 2012 Sep 17.
Tumors are capable of shedding DNA into the blood stream. This shed DNA may be recovered from serum or plasma. The objective of this study was to evaluate whether pyrosequencing promoter DNA in a panel of 12 breast cancer-related genes (APC, BRCA1, CCND2, CDH1, ESR1, GSTP1, HIN1, P16, RARβ, RASSF1, SFRP1 and TWIST) to measure the degree of methylation would lead to a useful serum-based marker of breast cancer. Serum was obtained from women who were about to undergo a breast biopsy or mastectomy at three hospitals from 1977 to 1987 in Grand Rapids, MI USA. We compared the methylation status of 12 genes in serum DNA obtained from three groups of postmenopausal women (mean age at blood collection: 63.0 y; SD 9.9; range 35-91): breast cancer cases with lymph node-positive disease (n = 241); breast cancer cases with lymph node-negative disease (n = 63); and benign breast disease control subjects (n = 234). Overall, median levels of promoter methylation were low, typically below 5%, for all genes in all study groups. For all genes, median levels of methylation were higher (by 3.3 to 47.6%) in lymph node-positive breast cancer cases than in the controls. Comparing mean methylation level between lymph-node positive cases and controls, the most statistically significant findings, after adjustment of the false-positive rate (q-value), were for TWIST (p = 0.04), SFRP1 (p = 0.16), ESR1 (p = 0.17), P16 (p = 0.19) and APC (p = 0.19). For two of these four genes (TWIST, P16), the median methylation level was also highest in lymph-node positive cases, intermediate in lymph node-negative cases and lowest in the controls. The percent of study subjects with mean methylation scores ≥ 5% was higher among lymph node-positive cases than controls for ten genes, and significantly higher for HIN1 and TWIST (22.0 vs. 12.2%, p = 0.04 and 37.9 vs. 24.5%, p = 0.004, respectively). Despite relatively consistent variation in methylation patterns among groups, these modest differences did not provide sufficient ability to distinguish between cases and controls in a clinical setting.
肿瘤能够将 DNA 释放入血液中。这些脱落的 DNA 可以从血清或血浆中回收。本研究的目的是评估在一组 12 个乳腺癌相关基因（APC、BRCA1、CCND2、CDH1、ESR1、GSTP1、HIN1、P16、RARβ、RASSF1、SFRP1 和 TWIST）中对启动子 DNA 进行焦磷酸测序以测量甲基化程度是否会导致有用的基于血清的乳腺癌标志物。血清取自 1977 年至 1987 年在美国密歇根州大急流城的三家医院接受乳房活检或乳房切除术的女性。我们比较了三组绝经后女性（采血时的平均年龄：63.0 岁；标准差 9.9；范围 35-91）血清 DNA 中 12 个基因的甲基化状态：淋巴结阳性疾病的乳腺癌病例（n=241）；淋巴结阴性疾病的乳腺癌病例（n=63）；良性乳腺疾病对照受试者（n=234）。总体而言，所有基因在所有研究组中的启动子甲基化水平均较低，通常低于 5%。对于所有基因，淋巴结阳性乳腺癌病例的甲基化水平中位数（高 3.3%至 47.6%）高于对照组。比较淋巴结阳性病例和对照组之间的平均甲基化水平，在调整假阳性率（q 值）后，最具统计学意义的发现是 TWIST（p=0.04）、SFRP1（p=0.16）、ESR1（p=0.17）、P16（p=0.19）和 APC（p=0.19）。在这四个基因中的两个（TWIST、P16）中，淋巴结阳性病例的中位甲基化水平也最高，淋巴结阴性病例的中位甲基化水平居中，对照组的中位甲基化水平最低。十个基因中，淋巴结阳性病例的平均甲基化评分≥5%的研究对象百分比高于对照组，HIN1 和 TWIST 显著更高（22.0%比 12.2%，p=0.04 和 37.9%比 24.5%，p=0.004）。尽管各组的甲基化模式存在相对一致的变化，但这些微小差异在临床环境中不足以区分病例和对照组。
