Department of Gastroenterology and Hepatology, University Medical Center Hamburg-Eppendorf, Martinistr. 52, D-20246 Hamburg, Germany.
Mol Cancer Res. 2011 Sep;9(9):1222-31. doi: 10.1158/1541-7786.MCR-10-0474. Epub 2011 Aug 1.
Hepatocarcinogenesis is a multistep process driving the progressive transformation of normal liver cells into highly malignant derivatives. Unlimited proliferation and telomere maintenance have been recognized as prerequisites for the development of liver cancer. Moreover, recent studies identified illegitimate β-catenin signaling as relevant hit in a considerable subset of patients. To further investigate the currently not well-understood malignant evolution driven by telomerase and β-catenin, we monitored cytogenetic and phenotypic alterations in untransformed telomerase-immortalized human fetal hepatocytes following forced activation of β-catenin signaling. As expected, constitutive activation of β-catenin signaling significantly enhanced proliferation with decreasing serum dependence. Previously intact contact inhibition was almost completely eliminated. Interestingly, after several passages in cell culture, immortalized clones with dominant-positive β-catenin signaling acquired additional chromosomal aberrations, in particular translocations, anchorage-independent growth capabilities, and formed tumors in athymic nude mice. In further support for the driving role of β-catenin during hepatocarcinogenesis, improved colony growth in soft agar and accelerated tumor formation was also confirmed in Huh7 cells following stable expression of the constitutively active S33Y β-catenin mutant. Telomerase inhibition showed that short-term expansion of transformed clones was not telomerase dependent. Finally, cancer pathway profiling in derived tumors revealed upregulation of characteristic genes associated with invasion and angiogenesis. In conclusion, illegitimate activation of β-catenin signaling enhances the transformation from immortalization to malignant growth in human fetal hepatocytes. Our data functionally confirm a permissive role for β-catenin signaling in the initial phase of hepatocarcinogenesis.
肝癌发生是一个多步骤的过程，驱动着正常肝细胞向高度恶性的衍生物进行渐进性转化。无限增殖和端粒维持已被认为是肝癌发展的前提条件。此外，最近的研究发现，β-连环蛋白信号的异常激活在相当一部分患者中是相关的靶点。为了进一步研究端粒酶和β-连环蛋白驱动的目前尚未完全了解的恶性演变，我们在强制激活β-连环蛋白信号后，监测未转化的端粒酶永生化人胎肝细胞中的细胞遗传学和表型改变。正如预期的那样，β-连环蛋白信号的组成性激活显著增强了增殖能力，同时降低了对血清的依赖性。以前完整的接触抑制几乎完全消除。有趣的是，在细胞培养中经过几个传代后，具有显性阳性β-连环蛋白信号的永生化克隆获得了额外的染色体异常，特别是易位、锚定非依赖性生长能力，并在免疫缺陷裸鼠中形成肿瘤。进一步支持β-连环蛋白在肝癌发生中的驱动作用，在 Huh7 细胞中稳定表达组成性激活的 S33Y β-连环蛋白突变后，也证实了软琼脂中集落生长的改善和肿瘤形成的加速。端粒酶抑制表明，转化克隆的短期扩增不依赖于端粒酶。最后，在衍生肿瘤中的癌症途径分析显示，与侵袭和血管生成相关的特征基因上调。总之，β-连环蛋白信号的异常激活增强了人胎肝细胞从永生化向恶性生长的转化。我们的数据功能上证实了β-连环蛋白信号在肝癌发生的初始阶段的许可作用。
