Department of Biology, Sbarro Health Research Organization, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122, USA.
Cancer Res. 2011 May 15;71(10):3701-8. doi: 10.1158/0008-5472.CAN-10-3951. Epub 2011 Apr 4.
Hepatitis B virus (HBV) is a major etiologic agent of chronic liver disease and hepatocellular carcinoma (HCC). HBV-encoded X antigen, HBx, and pathways implicated in the self-renewal of stem cells contribute to HCC, but it is not clear whether HBx expression promotes "stemness." Thus, experiments were designed to test the hypothesis that HBx triggers malignant transformation by promoting properties that are characteristic of cancer stem cells (CSC). To test this hypothesis, HepG2 cells were stably transduced with HBx and then assayed for phenotypic and molecular characteristics of "stemness." The relationship between HBx and "stemness"-associated markers was also evaluated by immunohistochemical staining of liver and tumor tissue sections from HBV-infected patients. The results showed that Oct-4, Nanog, Klf-4, β-catenin, and epithelial cell adhesion molecule (EpCAM) were activated by HBx in vitro and in vivo. EpCAM was detected in the nuclei of human HCC cells from infected patients. HBx promotes "stemness" by activating β-catenin and epigenetic upregulation of miR-181, both of which target EpCAM. HBx expression was also associated with depressed levels of E-cadherin. Moreover, HBx stimulated cell migration, growth in soft agar, and spheroid formation. This work is the first to propose that HBV promotes "stemness" in the pathogenesis of HCC. HBx-associated upregulated expression of multiple "stemness" markers supports the hypothesis that HBx contributes to hepatocarcinogenesis, at least in part, by promoting changes in gene expression that are characteristics of CSCs.
乙型肝炎病毒 (HBV) 是慢性肝病和肝细胞癌 (HCC) 的主要病因。HBV 编码的 X 抗原（HBx）和涉及干细胞自我更新的途径有助于 HCC 的发生，但尚不清楚 HBx 表达是否促进“干性”。因此，设计实验来检验假设，即 HBx 通过促进与癌症干细胞 (CSC) 特征相关的特性来引发恶性转化。为了检验这一假设，用 HBx 稳定转导 HepG2 细胞，然后检测“干性”的表型和分子特征。还通过对 HBV 感染患者的肝和肿瘤组织切片进行免疫组织化学染色，评估 HBx 与“干性”相关标志物之间的关系。结果表明，Oct-4、Nanog、Klf-4、β-catenin 和上皮细胞黏附分子 (EpCAM) 在体外和体内均被 HBx 激活。EpCAM 存在于感染患者的人 HCC 细胞的核中。HBx 通过激活β-catenin 和 miR-181 的表观遗传上调来促进“干性”，这两者均靶向 EpCAM。HBx 的表达也与 E-钙黏蛋白水平降低有关。此外，HBx 刺激细胞迁移、软琼脂生长和球体形成。这项工作首次提出 HBV 在 HCC 的发病机制中促进“干性”。HBx 相关的多个“干性”标志物的上调表达支持假设，即 HBx 通过促进与 CSCs 特征相关的基因表达变化，至少部分地促进肝癌的发生。
