Hepatitis B virus X protein upregulates HSP90alpha expression via activation of c-Myc in human hepatocarcinoma cell line, HepG2.
Hepatitis B virus X protein upregulates HSP90alpha expression via activation of c-Myc in human hepatocarcinoma cell line, HepG2.
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DOI：
10.1186/1743-422x-7-45
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发表时间：
2010-02-20
期刊：
影响因子：
4.8
通讯作者：
Liang Z
中科院分区：
文献类型：
--
作者：
Li W;Miao X;Qi Z;Zeng W;Liang J;Liang Z
乙型肝炎病毒X蛋白（HBx）在肝细胞癌（HCC）的发展中发挥着重要作用，然而，其对肿瘤侵袭和转移的贡献尚未确定。热休克蛋白90α（HSP90α）亚型是一种ATP依赖性分子伴侣，可维持癌细胞中客户癌蛋白的活性构象，在HCC中大量表达，特别是在乙型肝炎病毒（HBV）相关肿瘤中，可能参与肿瘤进展。通过蛋白质印迹分析测定 HBx 转染的 HepG2 细胞中 HSP90α、细胞外信号调节激酶 1/2 (ERK1/2)、磷酸化 ERK1/2 (p-ERK1/2) 和 c-Myc 的水平。通过 ELISA 测定证明内源性 ERK 活性。通过电泳迁移率变动分析 (EMSA) 评估 HBx 对 c-Myc 介导的 HSP90 α 启动子反式激活的调节。通过启动子测定分析c-Myc介导的HSP90α转录。用针对 c-Myc 的特异性小干扰 RNA (siRNA) 转染表达 HBx 的细胞。采用Transwell细胞侵袭实验评估细胞的体外侵袭能力。 HBx 在转录水平诱导 HSP90α 表达。 c-Myc抑制剂10058-F4处理后，HBx的诱导作用受到抑制。此外，HSP90α启动子的荧光素酶活性分析表明，HBx直接参与c-Myc介导的HSP90α转录激活。此外，HBx 通过激活 Ras/Raf/ERK1/2 级联诱导 c-Myc 表达，进而导致 c-Myc 介导的 HSP90α 启动子激活，随后上调 HSP90α 表达。 HBx 转染细胞中 HSP90α 的过度表达可增强肿瘤细胞的侵袭。 HBx 转染细胞中 siRNA 介导的 c-Myc 敲低显着抑制体外 HSP90α 表达和细胞侵袭。这些结果证明了HBx通过上调HSP90α的机制促进肿瘤细胞侵袭的能力，并为HBx的作用机制及其参与HCC肿瘤转移和复发提供了新的见解。
The Hepatitis B Virus X protein (HBx) plays a major role in hepatocellular carcinoma (HCC) development, however, its contribution to tumor invasion and metastasis has not been established so far. Heat shock protein 90 alpha (HSP90alpha) isoform is an ATP-dependent molecular chaperone that maintains the active conformation of client oncoproteins in cancer cells, which is abundantly expressed in HCC, especially in hepatitis B virus (HBV)-related tumors, might be involved in tumor progression. The levels of HSP90alpha, extracellular signal-regulated kinase 1/2 (ERK1/2), phosphorylated ERK1/2 (p-ERK1/2) and c-Myc in HBx-transfected HepG2 cells were determined by western blots analysis. The endogenous ERKs activity was demonstrated by ELISA assay. The regulation of c-Myc-mediated HSP90 alpha promoter transactivation by HBx was evaluated through electrophoretic mobility shift analysis (EMSA). The c-Myc-mediated HSP90alpha transcription was analysed by promoter assay. The HBx-expressing cells were transfected with specific small interference RNA (siRNA) against c-Myc. The in vitro invasion potentials of cells were evaluated by Transwell cell invasion assay. HBx induces HSP90alpha expression at the transcription level. The induction effect of HBx was inhibited after treatment with c-Myc inhibitor, 10058-F4. In addition, the luciferase activity of the HSP90alpha promoter analysis revealed that the HBx is directly involved in the c-Myc-mediated transcriptional activation of HSP90alpha. Furthermore, HBx induces c-Myc expression by activation of Ras/Raf/ERK1/2 cascades, which in turn results in activation of the c-Myc-mediated HSP90alpha promoter and subsequently up-regulation of the HSP90alpha expression. Overexpression of HSP90alpha in HBx-transfected cells enhances tumor cells invasion. siRNA-mediated c-Myc knockdown in HBx-transfected cells significantly suppressed HSP90alpha expression and cells invasion in vitro. These results demonstrate the ability of HBx to promote tumor cells invasion by a mechanism involving the up-regulation of HSP90alpha and provide new insights into the mechanism of action of HBx and its involvement in tumor metastasis and recurrence of HCC.