Department of Veterinary & Animal Science, University of Massachusetts at Amherst, MA, USA.
Epigenetics. 2010 Oct 1;5(7):645-55. doi: 10.4161/epi.5.7.12961.
Promoter methylation analysis of genes frequently silenced in breast cancer is a promising indicator of breast cancer risk, as these methylation events are thought to occur long before presentation of disease. The numerous exfoliated epithelial cells present in breast milk may provide the breast epithelial DNA needed for detailed methylation analysis and assessment of breast cancer risk. Fresh breast milk samples and health, lifestyle, and reproductive history questionnaires were collected from 111 women. Pyrosequencing analysis was conducted on DNA isolated from the exfoliated epithelial cells immunomagnetically separated from the total cell population in the breast milk of 102 women. A total of 65 CpG sites were examined in six tumor suppressor genes: PYCARD (also known as ASC or TMS1), CDH1, GSTP1, RBP1 (also known as CRBP1), SFRP1, and RASSF1. A sufficient quantity of DNA was obtained for meaningful analysis of promoter methylation; women donated an average of 86 ml of milk with a mean yield of 32,700 epithelial cells per ml. Methylation scores were in general low as expected of benign tissue, but analysis of outlier methylation scores revealed a significant relationship between breast cancer risk, as indicated by previous biopsy, and methylation score for several CpG sites in CDH1, GSTP1, SFRP1, and RBP1. Methylation of RASSF1 was positively correlated with women's age irrespective of her reproductive history. Promoter methylation patterns in DNA from breast milk epithelial cells can likely be used to assess breast cancer risk. Additional studies of women at high breast cancer risk are warranted.
在乳腺癌中经常沉默的基因启动子甲基化分析是乳腺癌风险的一个有前途的指标，因为这些甲基化事件被认为发生在疾病出现之前很久。母乳中存在大量脱落的上皮细胞，可能为详细的甲基化分析和乳腺癌风险评估提供所需的乳腺上皮细胞 DNA。从 111 名女性中收集了新鲜母乳样本和健康、生活方式和生殖史调查问卷。对从 102 名女性母乳中总细胞群体免疫磁分离出的脱落上皮细胞中分离出的 DNA 进行了焦磷酸测序分析。在六个肿瘤抑制基因中检查了 65 个 CpG 位点：PYCARD（也称为 ASC 或 TMS1）、CDH1、GSTP1、RBP1（也称为 CRBP1）、SFRP1 和 RASSF1。获得了足够数量的 DNA 用于有意义的启动子甲基化分析；女性平均捐赠了 86 毫升牛奶，平均每毫升产生 32700 个上皮细胞。如预期的良性组织一样，甲基化评分通常较低，但异常甲基化评分的分析表明，先前活检指示的乳腺癌风险与 CDH1、GSTP1、SFRP1 和 RBP1 中几个 CpG 位点的甲基化评分之间存在显著关系。RASSF1 的甲基化与女性的年龄呈正相关，而与她的生殖史无关。来自乳腺上皮细胞的 DNA 中的启动子甲基化模式可能可用于评估乳腺癌风险。需要对高乳腺癌风险的女性进行更多研究。
