Objective. An ideal sample source is critical for more reliable and sensitive early detection of nucleic acid changes associated with breast cancer. Breast milk (BM) is a good noninvasive origin for genetic testing of early breast cancer, but cells in BM are easily disintegrated. So we investigate here whether cell-free nucleic acid (cfNA) exists in BM in a more stable form and whether the quality of BM cfNA is good enough for genetic testing. Methods. A self-designed qRT-PCR method was used to measure the existence and abundance of cfDNA. Quality of cfDNA and cfRNA were detected by capillary electrophoresis. Whole genome bisulfite sequencing and miRNA sequencing were used to explore the sources of cfDNA and cell-free miRNA in BM. The copy number analysis and -test based on whole genome sequencing data were used to determine the integrity of genetic information in BM cfNA. Results. We found that cell-free DNA and miRNA exist in the studied breast milk samples in a stable form that can tolerate incubation of BM at room temperature for at least 7 days. These cell-free nucleic acids come mainly from breast-derived cells and contain genetic information as good integrity as in BM cells. We further listed some candidate miRNAs as potential biomarkers for research of early breast cancer screening by analysis of previous reports and our data. Conclusions. Our results suggest that cfDNA and cell-free miRNA in BM might be new noninvasive sample sources for finding early alterations of nucleic acid associated with the initiation and progression of breast cancer.

中文翻译：

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在母乳中使用无细胞 DNA 和 miRNA 筛查早期乳腺癌的潜力。

客观。理想的样品来源对于更可靠、更灵敏地早期检测与乳腺癌相关的核酸变化至关重要。母乳 (BM) 是早期乳腺癌基因检测的良好无创来源，但 BM 中的细胞很容易分解。因此，我们在此调查是否以更稳定的形式存在于 BM 中的无细胞核酸 (cfNA) 以及 BM cfNA 的质量是否足以进行基因检测。方法。使用自行设计的 qRT-PCR 方法测量 cfDNA 的存在和丰度。通过毛细管电泳检测cfDNA和cfRNA的质量。全基因组亚硫酸氢盐测序和 miRNA 测序用于探索 BM 中 cfDNA 和无细胞 miRNA 的来源。拷贝数分析和-基于全基因组测序数据的测试用于确定BM cfNA中遗传信息的完整性。结果。我们发现所研究的母乳样品中以稳定形式存在的无细胞 DNA 和 miRNA 可以耐受 BM 在室温下孵育至少 7 天。这些无细胞核酸主要来自乳腺来源的细胞，并包含与 BM 细胞一样完整的遗传信息。通过分析之前的报告和我们的数据，我们进一步列出了一些候选 miRNA 作为早期乳腺癌筛查研究的潜在生物标志物。结论. 我们的研究结果表明，BM 中的 cfDNA 和无细胞 miRNA 可能是新的非侵入性样本来源，用于发现与乳腺癌发生和进展相关的核酸的早期改变。