Department of Biology and Biochemistry, Center for Nuclear Receptors and Cell Signaling, University of Houston, Houston, TX 77204, USA.
Carcinogenesis. 2012 Aug;33(8):1502-11. doi: 10.1093/carcin/bgs161. Epub 2012 May 4.
MicroRNAs (miRNAs) play pivotal roles in stem cell biology, differentiation and oncogenesis and are of high interest as potential breast cancer therapeutics. However, their expression and function during normal mammary differentiation and in breast cancer remain to be elucidated. In order to identify which miRNAs are involved in mammary differentiation, we thoroughly investigated miRNA expression during functional differentiation of undifferentiated, stem cell-like, murine mammary cells using two different large-scale approaches followed by qPCR. Significant changes in expression of 21 miRNAs were observed in repeated rounds of mammary cell differentiation. The majority, including the miR-200 family and known tumor suppressor miRNAs, was upregulated during differentiation. Only four miRNAs, including oncomiR miR-17, were downregulated. Pathway analysis indicated complex interactions between regulated miRNA clusters and major pathways involved in differentiation, proliferation and stem cell maintenance. Comparisons with human breast cancer tumors showed the gene profile from the undifferentiated, stem-like stage clustered with that of poor-prognosis breast cancer. A common nominator in these groups was the E2F pathway, which was overrepresented among genes targeted by the differentiation-induced miRNAs. A subset of miRNAs could further discriminate between human non-cancer and breast cancer cell lines, and miR-200a/miR-200b, miR-146b and miR-148a were specifically downregulated in triple-negative breast cancer cells. We show that miR-200a/miR-200b can inhibit epithelial-mesenchymal transition (EMT)-characteristic morphological changes in undifferentiated, non-tumorigenic mammary cells. Our studies propose EphA2 as a novel and important target gene for miR-200a. In conclusion, we present evidentiary data on how miRNAs are involved in mammary cell differentiation and indicate their related roles in breast cancer.
微小 RNA（miRNAs）在干细胞生物学、分化和肿瘤发生中发挥着关键作用，作为潜在的乳腺癌治疗方法具有很高的研究价值。然而，它们在正常乳腺分化和乳腺癌中的表达和功能仍有待阐明。为了确定哪些 miRNAs 参与乳腺分化，我们使用两种不同的大规模方法，在重复的乳腺细胞分化过程中，对未分化的、干细胞样的、鼠类乳腺细胞的 miRNA 表达进行了彻底的研究，然后用 qPCR 进行验证。在多次乳腺细胞分化过程中，观察到 21 个 miRNA 的表达发生了显著变化。大多数 miRNA（包括 miR-200 家族和已知的肿瘤抑制 miRNA）在分化过程中上调。只有 4 个 miRNA（包括致癌 miRNA miR-17）下调。通路分析表明，调控 miRNA 簇与分化、增殖和干细胞维持的主要通路之间存在复杂的相互作用。与人类乳腺癌肿瘤的比较表明，未分化、类干细胞阶段的基因谱与预后不良的乳腺癌肿瘤聚类。这些组的一个共同因素是 E2F 通路，该通路在分化诱导的 miRNA 靶向的基因中过度表达。一组 miRNA 可以进一步区分人类非癌和乳腺癌细胞系，miR-200a/miR-200b、miR-146b 和 miR-148a 在三阴性乳腺癌细胞中特异性下调。我们表明，miR-200a/miR-200b 可以抑制未分化、非肿瘤性乳腺细胞的上皮-间充质转化（EMT）特征性形态变化。我们的研究提出 EphA2 是 miR-200a 的一个新的重要靶基因。总之，我们提供了证据，表明 miRNAs 参与了乳腺细胞分化，并表明它们在乳腺癌中的相关作用。
