Abstract 1564: Establishment and characterization of an orthotopic mouse model for human uveal melanoma hepatic metastasis.

Background: The survival of patients with metastatic uveal melanoma remains poor due to lack of effective treatment. Uveal melanoma patients preferentially develop hepatic metastasis, which is the major cause of death. Therefore, a suitable animal model of hepatic metastasis with human uveal melanoma is critical for the investigation of its biological behavior and designing an effective therapy. Methods: Human hepatic metastatic uveal melanoma cell line (UM001), established in our laboratory, and NOD scid gamma mice (NSG mice) were used for orthotopic hepatic metastasis model. The UM001 cell line has typical characters of human melanoma, including a GNAQ mutation and expression of IGF-1 receptors. 1.00 -1.25 x 106 of UM001 cells in 15-20μl suspension of RPMI1640 medium were implanted using 27G needles under the capsule of the liver through a 1.5 cm abdominal incision. After the development of liver tumors, the NSG mice were sacrificed and investigated the behavior of the tumor cells in the liver both macro- and microscopically. Immunohistochemical analysis was performed to confirm the expression of human melanoma markers (HMB45 and Melan-A), IGF-1R. Tumor specimens were also stained for mouse CD31 (constituent of the endothelial intercellular junction of the vessels) and human laminin (major basement component of the vessels) to investigate neovascularization and vasculogenic mimicry patterns in the tumor. In addition, we performed Western blot analysis and immunohistochemistry to investigate the activation of PI3K-Akt and MAPK signaling pathways. Results: We achieved 91% (10/11cases) success rate of tumor formation using the method described in the present report. UM001 cells formed localized macroscopic nodules in the mouse liver within 4 weeks and then developed intrahepatic and peritoneal metastases within 12 weeks after implantation. Immunohistochemical analysis showed the expression of melanoma markers, IGF-1R, neovascularization positive for mouse CD31, vasculogenic mimicry patterns composed of human laminin in the hepatic tumors. In addition, activation of phosphorylated Akt and Erk1/2 in the hepatic tumor specimens was also noted. Conclusion: This orthotopic mouse model of human uveal melanoma liver metastasis showed similar histological findings as those observed in human liver. Moreover, PI3K-Akt and MAPK signaling pathway are activated in the hepatic tumor tissue. Taken together, this model is a useful tool to investigate the biological behavior of metastatic uveal melanoma in vivo, and to test novel therapies for the treatment of human uveal melanoma metastasizing to liver. Citation Format: Shinji Ozaki, Makoto Yoshida, Mizue Terai, Senthamil Selvan, Michael J. Mastrangelo, Takami Sato. Establishment and characterization of an orthotopic mouse model for human uveal melanoma hepatic metastasis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1564. doi:10.1158/1538-7445.AM2013-1564