Department of Legal Medicine, Asahikawa Medical University, Asahikawa, Japan.
Department of Molecular Cancer Science, School of Medicine, Yamagata University, Yamagata, Japan.
Cancer Sci. 2019 Sep;110(9):2748-2759. doi: 10.1111/cas.14130. Epub 2019 Jul 30.
In hepatocarcinogenesis induced by diethylnitrosamine (DEN) in B6C3F1 mice, the BrafV637E mutation, corresponding to the human BRAFV600E mutation, plays a pivotal role. The livers of transgenic mice with a hepatocyte-specific human BRAFV600E mutation weighed 4.5 times more than that of normal mice and consisted entirely of hepatocytes, resembling DEN-induced preneoplastic hepatocytes. However, these transgenic mice spontaneously died 7 wk after birth, therefore this study aimed to clarify the causes of death. In the transgenic mice, the liver showed thrombopoietin (TPO) overexpression, which is associated with eventual megakaryocytosis and thrombocytosis, and activated platelets were deposited in hepatic sinusoids. TPO was also overexpressed in the DEN-induced hepatic tumors, and sinusoidal platelet deposition was observed in the hepatic tumors of humans and mice. Podoplanin was expressed in some of the Kupffer cells in the liver of the transgenic mice, indicating that platelet activation occurred via the interaction of podoplanin with C-type lectin receptor 2 (CLEC-2) on the platelet membrane. Additionally, erythrocyte dyscrasia and glomerulonephropathy/interstitial pneumonia associated with platelet deposition were observed. In the transgenic mice, aspirin (Asp) administration prevented platelet activation, reduced the liver/body weight ratio, decreased the platelet deposition in the liver, kidney, and lung, and prevented erythrocyte dyscrasia and ameliorated the renal/pulmonary changes. Thrombopoietin overproduction by BRAFV600E-mutated hepatocytes may contribute to hepatocyte proliferation via thrombocytosis, platelet activation, and the interaction of platelets with hepatic sinusoidal cells, while hematologic, renal, and pulmonary disorders due to aberrant platelet activation may lead to spontaneous death in the transgenic mice.
在二乙基亚硝胺（DEN）诱导的 B6C3F1 小鼠肝癌发生过程中，BrafV637E 突变（对应于人类 BRAFV600E 突变）发挥关键作用。具有肝细胞特异性人类 BRAFV600E 突变的转基因小鼠的肝脏重量是正常小鼠的 4.5 倍，并且完全由肝细胞组成，类似于 DEN 诱导的前瘤性肝细胞。然而，这些转基因小鼠在出生后 7 周自发死亡，因此本研究旨在阐明死亡原因。在转基因小鼠中，肝脏表现出血小板生成素（TPO）过度表达，这与最终的巨核细胞增多症和血小板增多症有关，并且激活的血小板沉积在肝窦。TPO 在 DEN 诱导的肝肿瘤中也过度表达，并且在人类和小鼠的肝肿瘤中观察到窦状血小板沉积。在转基因小鼠的肝脏中，一些枯否细胞表达 podoplanin，表明血小板通过 podoplanin 与血小板膜上的 C 型凝集素受体 2（CLEC-2）相互作用而被激活。此外，还观察到红细胞异常和与血小板沉积相关的肾小球肾炎/间质性肺炎。在转基因小鼠中，阿司匹林（Asp）给药可预防血小板激活，降低肝/体重比，减少肝、肾和肺中的血小板沉积，并预防红细胞异常和改善肾脏/肺部变化。BRAFV600E 突变的肝细胞过度产生 TPO 可能通过血小板增多症、血小板激活以及血小板与肝窦细胞的相互作用促进肝细胞增殖，而由于异常血小板激活导致的血液学、肾脏和肺部疾病可能导致转基因小鼠自发死亡。
