Department of Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, University of Tuebingen, Wilhelmstr. 56, 72074, Tübingen, Germany.
Arch Toxicol. 2013 Aug;87(8):1595-607. doi: 10.1007/s00204-013-1030-8. Epub 2013 Mar 12.
Mouse liver tumors that harbor activating mutations in Ctnnb1, encoding β-catenin, express high levels of various cytochromes P450 (CYP), including CYP2E1 and CYP1A2. Acetaminophen (AAP) is metabolized in hepatocytes by these CYPs to the reactive intermediate N-acetyl-p-benzoquinone-imine, which is toxic to hepatocytes at high doses where depletion of glutathione occurs. We have induced liver tumors in mice by treatment with the liver carcinogen N-nitrosodiethylamine followed by chronic treatment with the tumor promoter phenobarbital. Under this protocol, ~80 % of tumors display Ctnnb1 mutations and express high levels of various CYP isoforms. Tumor-bearing animals were given a single intraperitoneal injection of 300 mg/kg body weight AAP, which was well tolerated by the animals. This dose, however, eradicated essentially all larger Ctnnb1-mutated, CYP-positive liver tumors, killing >90 % of hepatoma cells: at 2 days after AAP, large necrotic areas filled with cell debris were observed in tumors. These were infiltrated in the following days by immune cells starting from the outer parts of the damaged areas slowly closing the "wounds" left from the poisoned tumor cells. During this period, there was increased proliferation of normal hepatocytes, but some residual tumor cells were also proliferating. Our results show that a selective poisoning of Ctnnb1-mutated liver tumors by administration of AAP is possible in this experimental system. Application of an adapted protocol could be envisaged for neo-adjuvant treatment of human hepatoblastoma which are frequently mutated in CTNNB1 and often show high expression of CYP2E1.
携带编码β-连环蛋白（β-catenin）的 Ctnnb1 激活突变的小鼠肝肿瘤表达高水平的各种细胞色素 P450（CYP），包括 CYP2E1 和 CYP1A2。乙酰氨基酚（AAP）在肝细胞中被这些 CYP 代谢为反应性中间产物 N-乙酰-p-苯醌亚胺，在高剂量下会导致肝细胞中毒，此时谷胱甘肽耗竭。我们通过用肝致癌物 N-二乙基亚硝胺处理然后用肿瘤促进剂苯巴比妥进行慢性处理，在小鼠中诱导肝肿瘤。在该方案下，~80%的肿瘤显示 Ctnnb1 突变并表达高水平的各种 CYP 同工酶。携带肿瘤的动物接受单次腹腔内注射 300mg/kg 体重的 AAP，动物对此很好耐受。然而，该剂量基本上消除了所有较大的 Ctnnb1 突变、CYP 阳性肝肿瘤，杀死了>90%的肝癌细胞：在 AAP 后 2 天，在肿瘤中观察到充满细胞碎片的大坏死区域。在接下来的几天中，免疫细胞从受损区域的外部缓慢地向内浸润，逐渐封闭来自中毒肿瘤细胞的“伤口”。在此期间，正常肝细胞增殖增加，但一些残留的肿瘤细胞也在增殖。我们的结果表明，在这种实验系统中，通过给予 AAP 对 Ctnnb1 突变的肝肿瘤进行选择性中毒是可能的。适应的方案的应用可以设想用于新辅助治疗人肝母细胞瘤，其经常在 CTNNB1 中发生突变，并且经常表现出 CYP2E1 的高表达。
