Peng Cong, Liu Hua Ying, Zhou Ming, Zhang Li Ming, Li Xiao Ling, Shen Shou Rong, Li Gui Yuan
Cancer Research Institute, Central South University, Changsha, Hunan, China.
Mol Cell Biochem. 2007 Sep;303(1-2):141-9. doi: 10.1007/s11010-007-9466-x. Epub 2007 Apr 26.
BRD7 is a novel gene which involved NPC in our lab. Our previous studies showed that BRD7 was expressed at high level in normal nasopharyngeal epithelial tissues, but at low level in nasopharyngeal carcinoma biopsies and cell lines. In these papers, we found that ectopic expression of BRD7 can decrease cell proliferation and capability to form colonies in soft agar. FCM (Flow cytometry) assay indicated that the cell cycle progression from G1 to S phase was inhibited and the expression of cyclinD1 was significantly decreased after being transfected with BRD7 in HNE1 cells (NPC cells). To further investigate the molecular mechanism of BRD7 suppression of NPC cells growth, the cDNA microarray was performed to detect difference in gene expression profile induced by BRD7. The results indicated that 21 genes expression were changed after being transfected with BRD7 and the differentially expressed gene including alpha-catenin, cyclinD1, E2F3 was confirmed by western-blot. Next, we found that even though no obvious changes of the total expression of beta-catenin were observed, the accumulation of beta-catenin in nucleus was blocked. In addition, it was found that the expression of beta-catenin was up-regulated in the complex composed of beta-catenin and alpha-catenin in HNE1 cells induction of BRD7. So, we concluded that over-expression of BRD7 increased the expression of alpha-catenin which "hold" beta-catenin in the complex and inhibited its accumulating in nucleus. At last, we demonstrated the c-jun, p-MEK, and p-ERK1/2 expression were down-regulated, and the Ap-1 promoter activity was inactive after being transfected with BRD7. We also found that over-expression of BRD7 can inactivate the c-jun and p-ERK1/2 after being treated with EGF in HNE1 cells. These results indicated that BRD7 played a negative role in ERK1/2 pathway. Taken together, our present results provide new insights for BRD7 function to inhibit NPC cells growth through negative regulating beta-catenin and ERK1/2 pathways.
BRD7是我们实验室发现的一个与鼻咽癌相关的新基因。我们之前的研究表明，BRD7在正常鼻咽上皮组织中高表达，而在鼻咽癌活检组织和细胞系中低表达。在这些研究中，我们发现BRD7的异位表达可降低细胞增殖及在软琼脂中形成集落的能力。流式细胞术（FCM）检测表明，在HNE1细胞（鼻咽癌细胞）中转入BRD7后，细胞周期从G1期到S期的进程受到抑制，细胞周期蛋白D1的表达显著降低。为进一步研究BRD7抑制鼻咽癌细胞生长的分子机制，我们进行了cDNA微阵列检测以分析BRD7诱导的基因表达谱差异。结果显示，转入BRD7后有21个基因的表达发生改变，其中包括α-连环蛋白、细胞周期蛋白D1、E2F3等差异表达基因，这些结果通过蛋白质免疫印迹法得到了证实。接下来，我们发现尽管β-连环蛋白的总表达量没有明显变化，但β-连环蛋白在细胞核中的积累受到了阻断。此外，我们还发现在BRD7诱导的HNE1细胞中，由β-连环蛋白和α-连环蛋白组成的复合物中β-连环蛋白的表达上调。因此，我们得出结论，BRD7的过表达增加了α-连环蛋白的表达，α-连环蛋白在复合物中“结合”β-连环蛋白并抑制其在细胞核中的积累。最后，我们证明了转入BRD7后，c-jun、磷酸化MEK（p-MEK）和磷酸化ERK1/2（p-ERK1/2）的表达下调，且Ap-1启动子活性降低。我们还发现，在HNE1细胞中用表皮生长因子（EGF）处理后，BRD7的过表达可使c-jun和p-ERK1/2失活。这些结果表明，BRD7在ERK1/2信号通路中发挥负性作用。综上所述，我们目前的研究结果为BRD7通过负向调节β-连环蛋白和ERK1/2信号通路抑制鼻咽癌细胞生长的功能提供了新的见解。
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