Abstract 4081: Podoplanin expression in Kupffer cells and platelet deposition on the hepatic sinusoidal cells in the liver of transgenic mice with a hepatocyte-specific human BRAFV600E mutation

In hepatocarcinogenesis induced by diethylnitrosamine (DEN) treatment in neonatal B6C3F1 mice, the BrafV637E mutation, corresponding to the human BRAFV600E mutation, plays a pivotal role. We produced the transgenic mice expressing human BRAFV600E mutation specifically in hepatocytes by using the albumin-cre method. The Alb-Cre/BRAFV600E transgenic mice showed the enlarged liver whose weight was five times as large as that of normal mice, and the liver entirely consisted of small basophilic hepatocytes resembling the DEN-induced preneoplastic hepatocytes. Although these transgenic mice were healthy after birth, they spontaneously died showing renal and pulmonary diseases. In the transgenic mice, the liver showed thrombopoietin (TPO) overexpression, which is associated with eventual megakaryocytosis/thrombocytosis, and platelets were found activated in the peripheral blood and deposited in hepatic sinusoids. Simultaneous staining for CD61/CD31 or CD61/F4-80 revealed that platelets were sparsely adhered to liver sinusoidal endothelial cells (LSEC) and densely adhered to and incorporated into Kupffer cells. Because the interaction of podoplanin with C-type lectin receptor 2 (CLEC-2) on platelet membranes is an important mechanism to reciprocally activate platelets and the podoplanin-expressing cells, we investigated whether podoplanin is expressed in any of the hepatic cell components in the transgenic mice. Simultaneous staining for podoplanin and F4-80 revealed that podoplanin was expressed in some of the Kupffer cells, indicating that the platelet activation occurred via the interaction of podoplanin on Kupffer cell membrans with C-type lectin receptor 2 (CLEC-2) on the platelet membrane. Additionally, glomerulonephropathy and interstitial pneumonia associated with platelet deposition were observed. Because platelets contribute growth/survival of hepatocytes by activating hepatic sinusoidal cells and directly hepatocytes via releasing various factors, interaction of platelets with hepatic sinusoidal cells was considered to promote the growth/survival of BRAF mutated hepatocytes. Furthermore, podoplanin expression in part of Kupffer cells in the transgenic mice was an important mechanism for platelet activation in the transgenic mice. On the other hand, the aberrant platelet activation was thought to cause glomerulonephropathy and interstitial pneumonia and led to spontaneous death in some of the transgenic mice. Citation Format: Hiroki Tanaka, Kie Horioka, Masahiro Yamamoto, Asari Masaru, Katsuhiro Okuda, Seiji Ohtani, Kosuke Yamazaki, Keiko Shimizu, Katsuhiro Ogawa. Podoplanin expression in Kupffer cells and platelet deposition on the hepatic sinusoidal cells in the liver of transgenic mice with a hepatocyte-specific human BRAFV600E mutation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4081.