Hou Jing, Zhou Zhirui, Chen Xingxing, Zhao Ruping, Yang Zhaozhi, Wei Na, Ni Qing, Feng Yan, Yu Xiaoli, Ma Jinli, Guo Xiaomao
Department of Breast Surgery, Guizhou Provincial People's Hospital, Guiyang 550002, China.
Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai 200032, China.
Oncotarget. 2016 Jul 19;7(29):45186-45198. doi: 10.18632/oncotarget.9870.
Growing evidence has demonstrated that human epidermal growth factor receptor 2 (HER2) is involved in the radiation response to breast cancer. However, the underlying mechanism remains elusive. Therefore, we investigated if HER2 overexpression is associated with radiosensitivity of breast cancer. We constructed breast cancer cell lines differing in HER2 expression by transducing HER2 cDNA or short hairpin RNA against HER2. We then assessed the radiosensitivity and investigated the potential mechanism by using cell proliferation assay, cell adhesion assays, anoikis assays, colony formation assays, and western blotting analyses. We found that HER2 introduction in breast cancer cell lines MCF-7 (low HER2 expression) and MDA-MB-231 (HER2 is not expressed) promoted cell proliferation and invasion and enhanced cell adhesion and resistance to anoikis. Moreover, HER2 reduced radiosensitivity in these two cells compared with the corresponding control. The opposite results were observed when HER2 was silenced in breast cancer cell lines ZR-7530 and SK-BR-3 (both cells with high expression of HER2) using HER2 shRNA. In addition, animal experiment results showed HER2 could enhance the radioresistance of xenograft tumors. Further studies showed HER2 promoted the phosphorylation of focal adhesion kinase (Fak) and thereby up-regulated the expression of proteins associated with the epithelial-to-mesenchymal transition such as Claudin-1, ZO-1, and ZEB-1. The inhibition of Fak activity using the Fak inhibitor (PF-562281) restored the radiosensitivity in HER2-overexpressing cells. In conclusion, HER2 reduces the radiosensitivity of breast cancer by activating Fak in vitro and in vivo. Fak might be a potential target for the radiosensitization of HER2-overexpressed breast cancer.
越来越多的证据表明，人类表皮生长因子受体2（HER2）参与乳腺癌的放射反应。然而，其潜在机制仍不清楚。因此，我们研究了HER2过表达是否与乳腺癌的放射敏感性相关。我们通过转导HER2 cDNA或针对HER2的短发夹RNA构建了HER2表达不同的乳腺癌细胞系。然后，我们使用细胞增殖试验、细胞黏附试验、失巢凋亡试验、集落形成试验和蛋白质印迹分析评估放射敏感性并研究潜在机制。我们发现，在乳腺癌细胞系MCF-7（HER2低表达）和MDA-MB-231（不表达HER2）中引入HER2可促进细胞增殖和侵袭，并增强细胞黏附及对失巢凋亡的抗性。此外，与相应对照相比，HER2降低了这两种细胞的放射敏感性。当使用HER2 shRNA在乳腺癌细胞系ZR-7530和SK-BR-3（均为HER2高表达细胞）中沉默HER2时，观察到相反的结果。此外，动物实验结果表明HER2可增强异种移植肿瘤的放射抗性。进一步研究表明，HER2促进粘着斑激酶（Fak）的磷酸化，从而上调与上皮-间质转化相关的蛋白质如Claudin-1、ZO-1和ZEB-1的表达。使用Fak抑制剂（PF-562281）抑制Fak活性可恢复HER2过表达细胞的放射敏感性。总之，HER2在体外和体内通过激活Fak降低乳腺癌的放射敏感性。Fak可能是HER2过表达乳腺癌放射增敏的潜在靶点。
