Wree A, Johnson C D, Font-Burgada J, Eguchi A, Povero D, Karin M, Feldstein A E
Department of Pediatrics, University of California-San Diego, La Jolla, CA, USA.
Laboratory of Gene Regulation and Signal Transduction, Departments of Pharmacology and Pathology, University of California-San Diego, La Jolla, CA, USA.
Cell Death Differ. 2015 Dec;22(12):1985-94. doi: 10.1038/cdd.2015.46. Epub 2015 Apr 24.
Liver cancer is a major health-care concern and its oncogenic mechanisms are still largely unclear. Persistent hepatocyte cell death is a common feature among various chronic liver diseases, the blocking of which presents as logical treatment. Therefore, we aimed at investigating tumor development in mice with hepatocyte-specific Bid depletion--a BH3-only Bcl-2 family member that amplifies apoptotic death signals. Hepatocyte-specific conditional Bid-knockout mice (Bid(Δhep)) were injected with 25 mg/kg diethylnitrosamine (DEN) at 14 days of age, and liver tumorigenesis was investigated 9 months later. Additionally, different models of acute liver injury were used including: acute high-dose DEN challenge, 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet and carbon tetrachloride (CCL4) injection. Bid(Δhep) mice developed significantly fewer tumors, showed smaller maximal and average tumor size and reduced tumor incidence. In the acute DEN model, 48 h post injection we observed a significant reduction in liver injury in Bid(Δhep) animals, assessed via serum transaminases and liver histopathology. Furthermore, TNF-α, IL-1ß, cJUN and IL-6 mRNA expression was reduced. These findings were accompanied by reduced compensatory hepatocyte proliferation in Bid(Δhep) mice when compared with controls by immunohistochemistry for Ki67 and proliferating cell nuclear antigen 48 h after DEN injection. In the acute CCL4 model, Bid(Δhep) mice displayed reductions in liver injury and inflammation when compared with controls. No differences in liver injury and serum bilirubin levels were detected in Bid(Δhep) and Bid(flo/flo) mice fed with DDC, which induces bile duct injury and a ductular reaction. Our study demonstrates that in DEN-induced hepatocellular carcinoma, the inhibition of hepatocyte death pathways through Bid deletion protects animals from tumorigenesis. These results suggest that reducing hepatocyte cell death, liver inflammation and compensatory proliferation has a stronger beneficial effect than the potential side effect of enhancing tumor cell survival.
肝癌是一个重大的医疗保健问题，其致癌机制在很大程度上仍不清楚。持续性肝细胞死亡是各种慢性肝病的一个共同特征，阻断这种死亡表现为一种合理的治疗方法。因此，我们旨在研究肝细胞特异性Bid缺失小鼠的肿瘤发展情况——Bid是仅含BH3结构域的Bcl-2家族成员，可放大凋亡死亡信号。在14日龄时给肝细胞特异性条件性Bid基因敲除小鼠（Bid(Δhep)）注射25mg/kg二乙基亚硝胺（DEN），9个月后研究肝脏肿瘤发生情况。此外，还使用了不同的急性肝损伤模型，包括：急性高剂量DEN攻击、3,5-二乙氧基羰基-1,4-二氢可力丁（DDC）饮食和四氯化碳（CCL4）注射。Bid(Δhep)小鼠发生的肿瘤明显较少，最大和平均肿瘤大小较小，肿瘤发生率降低。在急性DEN模型中，注射后48小时，通过血清转氨酶和肝脏组织病理学评估，我们观察到Bid(Δhep)动物的肝损伤明显减轻。此外，TNF-α、IL-1β、cJUN和IL-6 mRNA表达降低。与对照组相比，DEN注射后48小时，通过免疫组织化学检测Ki67和增殖细胞核抗原，Bid(Δhep)小鼠的代偿性肝细胞增殖减少，这些发现与之相符。在急性CCL4模型中，与对照组相比，Bid(Δhep)小鼠的肝损伤和炎症减轻。在喂食诱导胆管损伤和小胆管反应的DDC的Bid(Δhep)和Bid(flo/flo)小鼠中，未检测到肝损伤和血清胆红素水平的差异。我们的研究表明，在DEN诱导的肝细胞癌中，通过Bid缺失抑制肝细胞死亡途径可保护动物免于肿瘤发生。这些结果表明，减少肝细胞死亡、肝脏炎症和代偿性增殖比增强肿瘤细胞存活的潜在副作用具有更强的有益作用。
