ENEA Research Center Casaccia, Laboratory of Radiation Biology and Biomedicine, Casaccia, Rome, Italy.
Cell Cycle. 2011 Dec 1;10(23):4149-61. doi: 10.4161/cc.10.23.18346.
Advanced breast cancer cells acquire metastatic properties in response to TGFβ. We show here that the expression of c-Myb increases in TGFβ-treated ER (+) breast cancer cells by protein stabilization, transcription activation and release from miR200-dependent down-regulation. In particular, we mapped 2 sites for miR200b, miR200c and miR429 binding in the 3' UTR of the human c-myb gene. These microRNAs decreased the expression of c-Myb when transfected in MCF-7 cells. In addition, luciferase activity from a vector containing the 3' UTR of the c-myb gene was inhibited by miR200s through a binding-dependent mechanism. siRNA- and shRNA-mediated down-regulation was used to investigate the role of c-Myb for the effects induced by TGFβ in ER(+) breast cancer MCF-7 and ZR-75.1 cells. Transfection with c-Myb siRNAs blocked the increase of Slug (SNAI2) and Bcl-2 expression and reversed the decrease in E-cadherin expression induced by TGF-β treatment. Conversely, c-Myb down-regulation decreased invasion and anchorage-independent growth of breast cancer cells expressing a constitutively active TGFβ receptor I. Finally, apoptosis induced by etoposide increased in c-Myb-silenced TGFβ-treated ER(+) cell lines. In summary, exposure of ER(+) breast cancer cells to TGFβ induces an increase of c-Myb expression which is required for expression of EMT-associated markers, in vitro invasion and anchorage-independent growth. Furthermore, our findings suggest a potentially detrimental effect of TGFβ and c-Myb co-expression in breast cancer.
晚期乳腺癌细胞在 TGFβ 的作用下获得转移特性。我们在这里表明，c-Myb 的表达在 TGFβ 处理的 ER（+）乳腺癌细胞中通过蛋白稳定、转录激活和 miR200 依赖性下调而增加。特别是，我们在人 c-myb 基因的 3'UTR 中映射了 2 个 miR200b、miR200c 和 miR429 结合的位点。这些 microRNAs 在 MCF-7 细胞中转染时降低了 c-Myb 的表达。此外，含有 c-myb 基因 3'UTR 的载体的荧光素酶活性通过结合依赖性机制被 miR200s 抑制。siRNA 和 shRNA 介导的下调用于研究 c-Myb 在 ER（+）乳腺癌 MCF-7 和 ZR-75.1 细胞中 TGFβ 诱导的作用的作用。c-Myb siRNAs 的转染阻断了 Slug（SNAI2）和 Bcl-2 表达的增加，并逆转了 TGF-β 处理诱导的 E-钙粘蛋白表达的减少。相反，c-Myb 的下调降低了表达组成型激活 TGFβ 受体 I 的乳腺癌细胞的侵袭和非锚定依赖性生长。最后，c-Myb 沉默的 TGFβ 处理的 ER（+）细胞系中依托泊苷诱导的细胞凋亡增加。总之，ER（+）乳腺癌细胞暴露于 TGFβ 会诱导 c-Myb 表达增加，这是 EMT 相关标志物表达、体外侵袭和非锚定依赖性生长所必需的。此外，我们的研究结果表明 TGFβ 和 c-Myb 共表达在乳腺癌中可能具有潜在的有害作用。
