Li Wenzhao, Itou Junji, Tanaka Sunao, Nishimura Tomomi, Sato Fumiaki, Toi Masakazu
Department of Breast Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
Department of Breast Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
Exp Cell Res. 2016 May 1;343(2):177-189. doi: 10.1016/j.yexcr.2016.03.023. Epub 2016 Mar 28.
Among breast cancer subtypes, basal-like breast cancer is particularly aggressive, and research on the molecules involved in its pathology might contribute to therapy. In this study, we found that expression of NKX6.1, a homeobox transcription factor, is higher in basal-like breast cancer than in other subtypes. In loss-of-function experiments on basal-like breast cancer cell lines, NKX6.1-depleted cells exhibited reduced cell growth. Because cytokine interleukin-6 (IL-6) is expressed in basal-like breast cancer, and increases cell growth, we analyzed expression levels of IL6, an IL-6 gene, and observed reduced IL6 expression in NKX6.1-depleted cells. In a reporter assay, IL6 promoter activity was reduced by loss of NKX6.1 function. A pull-down assay showed that NKX6.1 binds to the proximal region in IL6 promoter. These results indicate that NKX6.1 directly up-regulates IL6 expression. To investigate further, we established cells with forced expression of IL-6. We observed that exogenous IL-6 expression restored the reduced cell growth of NKX6.1-depleted cells. Furthermore, orthotopic xenografts showed that NKX6.1-depleted cells lost the capacity for tumor formation. We therefore conclude that NKX6.1 is a factor for IL-6-regulated growth and tumor formation in basal-like breast cancer. Our findings facilitate profound understanding of basal-like breast cancer, and the development of suitable therapy.
在乳腺癌亚型中，基底样乳腺癌具有特别强的侵袭性，对其病理过程中涉及的分子进行研究可能有助于治疗。在本研究中，我们发现同源框转录因子NKX6.1在基底样乳腺癌中的表达高于其他亚型。在对基底样乳腺癌细胞系进行的功能丧失实验中，NKX6.1缺失的细胞生长减缓。由于细胞因子白细胞介素-6（IL-6）在基底样乳腺癌中表达，并能促进细胞生长，我们分析了IL-6基因IL6的表达水平，发现NKX6.1缺失的细胞中IL6表达降低。在报告基因检测中，NKX6.1功能丧失导致IL6启动子活性降低。下拉实验表明NKX6.1与IL6启动子的近端区域结合。这些结果表明NKX6.1直接上调IL6的表达。为了进一步研究，我们建立了强制表达IL-6的细胞。我们观察到外源性IL-6表达恢复了NKX6.1缺失细胞中减缓的细胞生长。此外，原位异种移植显示NKX6.1缺失的细胞失去了肿瘤形成能力。因此，我们得出结论，NKX6.1是基底样乳腺癌中IL-6调节生长和肿瘤形成的一个因子。我们的研究结果有助于深入了解基底样乳腺癌，并推动合适治疗方法的开发。
