Division of Molecular Genome Analysis, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Oncogene. 2012 Sep 13;31(37):4150-63. doi: 10.1038/onc.2011.571. Epub 2011 Dec 12.
MicroRNAs (miRNAs) as modulators of gene expression have been described to display both tumor-promoting and tumor-suppressive functions. Although their role has been studied in different tumor types, little is known about how they regulate nuclear factor κB (NF-κB) signaling in breast cancer. Here, we performed an unbiased whole genome miRNA (miRome) screen to identify novel modulators of NF-κB pathway in breast cancer. The screen identified 13 miRNA families whose members induced consistent effects on NF-κB activity. Among those, the miR-520/373 family inhibited NF-κB signaling through direct targeting of RELA and thus strongly reduced expression and secretion of the pro-inflammatory cytokines interleukin (IL)-6 and IL-8. With a combination of in vitro and in vivo approaches, we propose a metastasis-suppressive role of miR-520/373 family. miR-520c and miR-373 abrogated both in vitro cell invasion and in vivo intravasation of highly invasive MDA-MB-231 cells. However, knockdown of RELA did not affect their metastatic ability. mRNA profiling of MDA-MB-231 cells on overexpression of miR-520/373 members revealed a strong downregulation of transforming growth factor-β (TGF-β) signaling. Mechanistically, the metastasis-suppressive role of miR-520/373 can be attributed to direct suppression of TGFBR2, as the silencing of TGFBR2 phenocopied the effects of miR-520/373 overexpression on suppression of Smad-dependent expression of the metastasis-promoting genes parathyroid hormone-related protein, plasminogen activator inhibitor-1 and angiopoietin-like 4 as well as tumor cell invasion, in vitro and in vivo. A negative correlation between miR-520c and TGFBR2 expression was observed in estrogen receptor negative (ER(-)) breast cancer patients but not in the ER positive (ER(+)) subtype. Remarkably, decreased expression of miR-520c correlated with lymph node metastasis specifically in ER(-) tumors. Taken together, our findings reveal that miR-520/373 family has a tumor-suppressive role in ER(-) breast cancer by acting as a link between the NF-κB and TGF-β pathways and may thus contribute to the interplay of tumor progression, metastasis and inflammation.
微小 RNA（miRNA）作为基因表达的调节剂，被描述为具有促进肿瘤和抑制肿瘤的双重功能。尽管它们在不同的肿瘤类型中的作用已经被研究，但关于它们如何调节乳腺癌中的核因子 κB（NF-κB）信号通路知之甚少。在这里，我们进行了一项无偏见的全基因组 miRNA（miRome）筛选，以鉴定乳腺癌中 NF-κB 通路的新型调节剂。该筛选鉴定出了 13 个 miRNA 家族，它们的成员对 NF-κB 活性产生一致的影响。其中，miR-520/373 家族通过直接靶向 RELA 抑制 NF-κB 信号，从而强烈降低促炎细胞因子白细胞介素（IL）-6 和 IL-8 的表达和分泌。通过体外和体内方法的结合，我们提出 miR-520/373 家族具有抑制转移的作用。miR-520c 和 miR-373 消除了高度侵袭性 MDA-MB-231 细胞的体外细胞侵袭和体内血管内渗。然而，RELA 的敲低并不影响它们的转移能力。MDA-MB-231 细胞中 miR-520/373 成员过表达的 mRNA 谱显示 TGF-β 信号强烈下调。从机制上讲，miR-520/373 的转移抑制作用可归因于对 TGFBR2 的直接抑制，因为 TGFBR2 的沉默模拟了 miR-520/373 过表达对促转移基因甲状旁腺激素相关蛋白、纤溶酶原激活物抑制剂-1 和血管生成素样 4 以及肿瘤细胞侵袭的 Smad 依赖性表达的抑制作用，无论是在体外还是在体内。在雌激素受体阴性（ER(-)）乳腺癌患者中观察到 miR-520c 与 TGFBR2 表达之间存在负相关，但在 ER 阳性（ER(+)）亚型中则没有。值得注意的是，miR-520c 的表达降低与淋巴结转移特异性相关，特别是在 ER(-)肿瘤中。总之，我们的研究结果表明，miR-520/373 家族在 ER(-)乳腺癌中具有肿瘤抑制作用，作为 NF-κB 和 TGF-β 通路之间的联系，可能有助于肿瘤进展、转移和炎症的相互作用。
