Browne Eva P, Dinc Signem E, Punska Elizabeth C, Agus Sami, Vitrinel Ayca, Erdag Gulay Ciler, Anderton Douglas L, Arcaro Kathleen F, Yilmaz Bayram
Department of Veterinary & Animal Science, University of Massachusetts Amherst, Amherst, MA, USA.
Department of Physiology, Faculty of Medicine, Yeditepe University, Istanbul, Turkey.
J Hum Lact. 2014 Nov;30(4):450-7. doi: 10.1177/0890334414548224. Epub 2014 Aug 27.
Breast cancer is the most frequently diagnosed cancer among Turkish women and both the incidence and associated mortality appear to be increasing. Of particular concern is the percentage of young women diagnosed with breast cancer; roughly 20% of all breast cancer diagnoses in Turkey are in women younger than 40 years. Increased DNA methylation in the promoter region of tumor suppressor genes is a promising molecular biomarker, and human milk provides exfoliated breast epithelial cells appropriate for DNA methylation analyses. Comparisons between DNA methylation patterns in epithelial (epithelial-enriched) and nonepithelial (epithelial-depleted) cell fractions from breast milk have not been reported previously.
In the present study, we examined promoter methylation of 3 tumor suppressor genes in epithelial-enriched and epithelial-depleted cell fractions isolated from breast milk of 43 Turkish women.
Percentage methylation in the promoter region of Rass association domain family 1 (RASSF1), secreted frizzle related protein 1 (SFRP1), and glutathione-S-transferase class pi 1 was determined by pyrosequencing of the epithelial-enriched and epithelial-depleted cell fractions.
Pyrosequencing identified a few subjects with significantly increased methylation in 1 or more genes. There was little correlation between the 2 cell fractions within individuals; only 1 woman had increased methylation for 1 gene (SFRP1) in both her enriched and depleted cell fractions. Methylation was positively associated with age for SFRP1 (epithelial-depleted fraction) and with body mass index for RASSF1 (epithelial-enriched cell fraction), respectively.
Overall, results show that the methylation signals vary between different cell types in breast milk and suggest that breast milk can be used to assess DNA methylation patterns associated with increased breast cancer risk.
乳腺癌是土耳其女性中最常被诊断出的癌症，其发病率和相关死亡率似乎都在上升。尤其令人担忧的是被诊断出患有乳腺癌的年轻女性比例；在土耳其，所有乳腺癌诊断病例中约20%是40岁以下的女性。肿瘤抑制基因启动子区域DNA甲基化增加是一种很有前景的分子生物标志物，而人乳提供了适合进行DNA甲基化分析的脱落乳腺上皮细胞。此前尚未报道过人乳中上皮（富含上皮细胞）和非上皮（缺乏上皮细胞）细胞组分的DNA甲基化模式之间的比较。
在本研究中，我们检测了从43名土耳其女性的母乳中分离出的富含上皮细胞和缺乏上皮细胞的细胞组分中3种肿瘤抑制基因的启动子甲基化情况。
通过对富含上皮细胞和缺乏上皮细胞的细胞组分进行焦磷酸测序，测定Ras关联结构域家族1（RASSF1）、分泌型卷曲相关蛋白1（SFRP1）和谷胱甘肽-S-转移酶π1启动子区域的甲基化百分比。
焦磷酸测序发现少数受试者中1个或更多基因的甲基化显著增加。个体内的两种细胞组分之间几乎没有相关性；只有1名女性在其富含上皮细胞和缺乏上皮细胞的细胞组分中，有1个基因（SFRP1）的甲基化都增加。SFRP1（缺乏上皮细胞的组分）的甲基化与年龄呈正相关，RASSF1（富含上皮细胞的组分）的甲基化与体重指数呈正相关。
总体而言，结果表明母乳中不同细胞类型的甲基化信号存在差异，并提示母乳可用于评估与乳腺癌风险增加相关的DNA甲基化模式。
