Department of Oncology, Beijing Hospital, National Center of Gerontology, Beijing, China.
Department of Bioengineering and Therapeutic Sciences and Liver Center, University of California, San Francisco, CA.
Hepatology. 2019 Dec;70(6):2003-2017. doi: 10.1002/hep.30556. Epub 2019 Apr 11.
Inactivating mutations of axis inhibition protein 1 (AXIN1), a negative regulator of the Wnt/β-Catenin cascade, are among the common genetic events in human hepatocellular carcinoma (HCC), affecting approximately 10% of cases. In the present manuscript, we sought to define the genetic crosstalk between Axin1 mutants and Wnt/β-catenin as well as Notch signaling cascades along hepatocarcinogenesis. We discovered that c-MET activation and AXIN1 mutations occur concomitantly in ~3%-5% of human HCC samples. Subsequently, we generated a murine HCC model by means of CRISPR/Cas9-based gene deletion of Axin1 (sgAxin1) in combination with transposon-based expression of c-Met in the mouse liver (c-Met/sgAxin1). Global gene expression analysis of mouse normal liver, HCCs induced by c-Met/sgAxin1, and HCCs induced by c-Met/∆N90-β-Catenin revealed activation of the Wnt/β-Catenin and Notch signaling in c-Met/sgAxin1 HCCs. However, only a few of the canonical Wnt/β-Catenin target genes were induced in c-Met/sgAxin1 HCC when compared with corresponding lesions from c-Met/∆N90-β-Catenin mice. To study whether endogenous β-Catenin is required for c-Met/sgAxin1-driven HCC development, we expressed c-Met/sgAxin1 in liver-specific Ctnnb1 null mice, which completely prevented HCC development. Consistently, in AXIN1 mutant or null human HCC cell lines, silencing of β-Catenin strongly inhibited cell proliferation. In striking contrast, blocking the Notch cascade through expression of either the dominant negative form of the recombinant signal-binding protein for immunoglobulin kappa J region (RBP-J) or the ablation of Notch2 did not significantly affect c-Met/sgAxin1-driven hepatocarcinogenesis. Conclusion: We demonstrated here that loss of Axin1 cooperates with c-Met to induce HCC in mice, in a β-Catenin signaling-dependent but Notch cascade-independent way.
轴抑制蛋白 1（AXIN1）的失活突变是人类肝细胞癌（HCC）中常见的遗传事件之一，约影响 10%的病例。在本手稿中，我们试图定义 Axin1 突变体与 Wnt/β-catenin 以及沿肝癌发生的 Notch 信号级联之间的遗传串扰。我们发现，c-MET 激活和 AXIN1 突变同时发生在约 3%-5%的人类 HCC 样本中。随后，我们通过 CRISPR/Cas9 基于基因缺失 Axin1（sgAxin1）与转座子表达 c-Met 在小鼠肝脏（c-Met/sgAxin1）相结合，生成了一种小鼠 HCC 模型。对小鼠正常肝脏、c-Met/sgAxin1 诱导的 HCC 和 c-Met/∆N90-β-Catenin 诱导的 HCC 的全基因表达分析显示，Wnt/β-catenin 和 Notch 信号在 c-Met/sgAxin1 HCC 中被激活。然而，与 c-Met/∆N90-β-Catenin 小鼠的相应病变相比，c-Met/sgAxin1 HCC 中仅有少数经典 Wnt/β-catenin 靶基因被诱导。为了研究内源性β-catenin 是否是 c-Met/sgAxin1 驱动的 HCC 发展所必需的，我们在肝脏特异性 Ctnnb1 缺失小鼠中表达 c-Met/sgAxin1，这完全阻止了 HCC 的发展。一致地，在 AXIN1 突变或缺失的人类 HCC 细胞系中，β-catenin 的沉默强烈抑制细胞增殖。相比之下，通过表达重组信号结合蛋白免疫球蛋白 κ J 区（RBP-J）的显性负形式或 Notch2 的缺失来阻断 Notch 级联，并不显著影响 c-Met/sgAxin1 驱动的肝癌发生。结论：我们在这里证明，AXIN1 的缺失与 c-Met 协同作用，在小鼠中诱导 HCC 的发生，这是一种依赖于β-catenin 信号但不依赖于 Notch 级联的方式。
