Abstract 2894: Intracellular gap formation of the liver sinusoidal endothelial cells facilitates the liver metastasis ability of cancer cells
Authors: Hoang Truong Huu , Sato-Matsubara Misako , Hideto Yuasa , Matsubara Tsutomu , Urushima Hayato , Le Thuy Thi Thanh , Daikoku Atsuko , Okina Yoshinori , Yoshizato Katsutoshi , Kawada Norifumi , Tamori Akihiro 
Published: July 2021

Abstract
Engraftment of cancer cells to liver pre-metastatic niches and their subsequent growth requires complex interaction with liver sinusoidal endothelial cells (LSECs). Intracellular gap formation of LSECs results from the destruction of the fenestration under histopathological conditions, but their role in liver metastasis is not fully understood. Therefore, this study aims to clarify the molecular function of the gap formation in liver metastasis. To study gap formation, acetaminophen (APAP) and thioacetamide (TAA) were used to pretreat C57BL/6 wild-type mice by intraperitoneal injection. Then, 2 x 106 mouse hepatoma Hepa1-6 cells and colon cancer Colon-26 cells were intrasplenically injected in both treated and non-treated groups. Mice were sacrificed after 18 hours and 72 hours of injection to observe the cancer cell invasion in the hepatic sinusoidal lumen and to count the number of cancer cell engraftment in the liver, respectively. Hepa1-6 cells and isolated primary mouse LSECs were co-cultured for 18 hours to observe the phenomenon in vitro. Quantitative-PCR, Hematoxylin & Eosin, immunofluorescence staining, scanning electron microscope (SEM), transmission electron microscope (TEM), and 3 dimensions tomographic reconstruction image (3D-TRI) were conducted to analyze the data. After 72 hours of injection, the number of cancer cells engrafted into the liver was significantly increased in the APAP-injected group compared to the control (p&lt;0.05). In the TAA model, defenestration of LSECs appeared in the fibrotic area whereas gap formation appeared in the non-fibrotic area, cancer cells dominantly engrafted into the non-fibrotic area. In vitro, LSECs co-cultured with Hepa1-6 increased mRNA levels of matrix metalloproteinase-9 (30-fold) and intercellular adhesion molecule 1 (1.5-fold) and depolymerization of F-actin. Simultaneously, the number of fenestrae and gap formation in LSECs was significantly increased compared to monoculture. Both in vivo-, in vitro- SEM and TEM images clearly showed that Hepa1-6 cells induced the gap formation in LSECs and their protrusions extended to the gaps. Furthermore, 3D-TRI reconstructed the image of cancer cells that broke through the LSEC wall and intracellularly invaded the hepatocyte. Our study demonstrated that the formation of intracellular gaps in LSECs promotes the invasion of cancer cells into the liver. This new insight may lead to novel strategies to prevent liver metastasis.
Citation Format: Truong Huu Hoang, Misako Sato-Matsubara, Yuasa Hideto, Tsutomu Matsubara, Hayato Urushima, Thuy Thi Thanh Le, Atsuko Daikoku, Yoshinori Okina, Katsutoshi Yoshizato, Norifumi Kawada, Akihiro Tamori. Intracellular gap formation of the liver sinusoidal endothelial cells facilitates the liver metastasis ability of cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2894.