Nagata Hiromitsu, Hatano Etsuro, Tada Masaharu, Murata Miki, Kitamura Koji, Asechi Hiroyuki, Narita Masato, Yanagida Atsuko, Tamaki Nobuyuki, Yagi Shintaro, Ikai Iwao, Matsuzaki Koichi, Uemoto Shinji
Department of Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Hepatology. 2009 Jun;49(6):1944-53. doi: 10.1002/hep.22860.
Transforming growth factor beta (TGF-beta) signaling involves both tumor-suppression and oncogenesis. TGF-beta activates the TGF-beta type I receptor (TbetaRI) and c-Jun N-terminal kinase (JNK), which differentially phosphorylate the mediator Smad3 to become COOH-terminally phosphorylated Smad3 (pSmad3C) and linker-phosphorylated Smad3 (pSmad3L). TbetaRI-dependent pSmad3C transmits a tumor-suppressive TGF-beta signal, while JNK-dependent pSmad3L promotes carcinogenesis in human chronic liver disorders. The aim of this study is to elucidate how SP600125, a JNK inhibitor, affected rat hepatocellular carcinoma (HCC) development, while focusing on the domain-specific phosphorylation of Smad3. The rats received subcutaneous injections of either SP600125 or vehicle 11 times weekly together with 100 ppm N-diethylnitrosamine (DEN) administration for 56 days and were sacrificed in order to evaluate HCC development 28 days after the last DEN administration. The number of tumor nodules greater than 3 mm in diameter and the liver weight/body weight ratio were significantly lower in the SP600125-treated rats than those in the vehicle-treated rats (7.9 +/- 0.8 versus 17.7 +/- 0.9: P < 0.001; 6.3 +/- 1.2 versus 7.1 +/- 0.2%: P < 0.05). SP600125 significantly prolonged the median survival time in rats with DEN-induced HCC (113 versus 97 days: log-rank P = 0.0018). JNK/pSmad3L/c-Myc was enhanced in the rat hepatocytes exposed to DEN. However, TbetaRI/pSmad3C/p21(WAF1) was impaired as DEN-induced HCC developed and progressed. The specific inhibition of JNK activity by SP600125 suppressed pSmad3L/c-Myc in the damaged hepatocytes and enhanced pSmad3C/p21(WAF1), acting as a tumor suppressor in normal hepatocytes.
Administration of SP600125 to DEN-treated rats shifted hepatocytic Smad3-mediated signal from oncogenesis to tumor suppression, thus suggesting that JNK could be a therapeutic target of human HCC development and progression.
转化生长因子β（TGF-β）信号传导涉及肿瘤抑制和肿瘤发生。TGF-β激活TGF-βI型受体（TβRI）和c-Jun氨基末端激酶（JNK），它们使介质Smad3发生不同程度的磷酸化，分别成为羧基末端磷酸化的Smad3（pSmad3C）和连接区磷酸化的Smad3（pSmad3L）。TβRI依赖性pSmad3C传递肿瘤抑制性TGF-β信号，而JNK依赖性pSmad3L在人类慢性肝脏疾病中促进致癌作用。本研究的目的是阐明JNK抑制剂SP600125如何影响大鼠肝细胞癌（HCC）的发展，同时关注Smad3的结构域特异性磷酸化。大鼠每周皮下注射11次SP600125或溶剂，同时给予100 ppm N-二乙基亚硝胺（DEN），持续56天，并在最后一次给予DEN后28天处死，以评估HCC的发展情况。SP600125治疗组大鼠直径大于3 mm的肿瘤结节数量和肝重/体重比显著低于溶剂治疗组大鼠（7.9±0.8对17.7±0.9：P<0.001；6.3±1.2对7.1±0.2%：P<0.05）。SP600125显著延长了DEN诱导的HCC大鼠的中位生存时间（113天对97天：对数秩检验P=0.0018）。暴露于DEN的大鼠肝细胞中JNK/pSmad3L/c-Myc增强。然而，随着DEN诱导的HCC的发生和发展，TβRI/pSmad3C/p21（WAF1）受损。SP600125对JNK活性的特异性抑制抑制了受损肝细胞中的pSmad3L/c-Myc，并增强了pSmad3C/p21（WAF1），后者在正常肝细胞中起肿瘤抑制作用。
对DEN处理的大鼠给予SP600125可使肝细胞Smad3介导的信号从肿瘤发生转变为肿瘤抑制，因此表明JNK可能是人类HCC发生和发展的治疗靶点。
