Locke Imogen, Kote-Jarai Zsofia, Fackler Mary Jo, Bancroft Elizabeth, Osin Peter, Nerurkar Ashutosh, Izatt Louise, Pichert Gabriella, Gui Gerald P H, Eeles Rosalind A
Translational Cancer Genetics Team, Institute of Cancer Research, 15 Cotswold Road, Sutton, Surrey SM2 5NG, UK.
Breast Cancer Res. 2007;9(1):R20. doi: 10.1186/bcr1657.
Female germline BRCA gene mutation carriers are at increased risk for developing breast cancer. The purpose of our study was to establish whether healthy BRCA mutation carriers demonstrate an increased frequency of aberrant gene promoter hypermethylation in ductal lavage (DL) fluid, compared with predictive genetic test negative controls, that might serve as a surrogate marker of BRCA1/2 mutation status and/or breast cancer risk.
The pattern of CpG island hypermethylation within the promoter region of a panel of four genes (RAR-beta, HIN-1, Twist and Cyclin D2) was assessed by methylation-specific polymerase chain reaction using free DNA extracted from DL fluid.
Fifty-one DL samples from 24 healthy women of known BRCA mutation status (7 BRCA1 mutation carriers, 12 BRCA2 mutation carriers and 5 controls) were available for methylation analysis. Eight of 19 (42.1%) BRCA mutation carriers were found to have at least one hypermethylated gene in the four-gene panel. Two BRCA mutation carriers, in whom aberrant methylation was found, also had duct epithelial cell atypia identified. No hypermethylation was found in DL samples from 5 negative controls (p = 0.13).
We found substantial levels of aberrant methylation, with the use of a four-gene panel, in the fluid from the breasts of healthy BRCA mutation carriers compared with controls. Methylation analysis of free DNA in DL fluid may offer a useful surrogate marker for BRCA1/2 mutation status and/or breast cancer risk. Further studies are required for the evaluation of the specificity and predictive value of aberrant methylation in DL fluid for future breast cancer development in BRCA1/2 mutation carriers.
女性生殖系BRCA基因突变携带者患乳腺癌的风险增加。我们研究的目的是确定与预测性基因检测阴性对照相比，健康的BRCA基因突变携带者在导管灌洗（DL）液中异常基因启动子高甲基化的频率是否增加，这可能作为BRCA1/2突变状态和/或乳腺癌风险的替代标志物。
使用从DL液中提取的游离DNA，通过甲基化特异性聚合酶链反应评估一组四个基因（RAR-β、HIN-1、Twist和细胞周期蛋白D2）启动子区域内的CpG岛高甲基化模式。
来自24名已知BRCA突变状态的健康女性（7名BRCA1突变携带者、12名BRCA2突变携带者和5名对照）的51份DL样本可用于甲基化分析。在19名（42.1%）BRCA突变携带者中，有8名在四基因组中发现至少有一个基因高甲基化。两名发现异常甲基化的BRCA突变携带者也被鉴定出有导管上皮细胞异型性。在5名阴性对照的DL样本中未发现高甲基化（p = 0.13）。
我们发现，与对照组相比，健康的BRCA基因突变携带者乳房中的液体在使用四基因组时存在大量异常甲基化。DL液中游离DNA的甲基化分析可能为BRCA1/2突变状态和/或乳腺癌风险提供一个有用的替代标志物。需要进一步研究来评估DL液中异常甲基化对BRCA1/2突变携带者未来患乳腺癌的特异性和预测价值。
