Abstract 623: Feasibility of surgical orthotopic implantation for establishment of patient-derived liver metastatic uveal melanoma xenograft model in NSG mouse

The prognosis of metastatic uveal melanoma (UM) is extremely poor. Approximately 90% of patients with metastatic UM die from hepatic metastasis. Controlling hepatic metastases has been a rational approach to extend survival. This raises an urgent need to develop a novel mouse model for further investigation. Patient-derived tumor xenograft (PDX) mouse model provides potential benefit through a personalized medicine approach. This model may be useful for predictions of clinical outcomes, drug efficacy and biomarker identification. Most PDX models, including UM PDX models, are made by ectopic subcutaneous implantation. Subcutaneous PDX models have some obstacles in translational research due to differences in anatomic microenvironment from tumor origin, low engraftment rate, and slow tumor growth. Our goal was to develop an orthotopic PDX model of liver metastatic UM which would overcome these difficulties. In developing our model, we first compared the differences in growth in a liver with a subcutaneous site using two UM cell lines (UM001 and UM004) in NSG mice, to ascertain which site is a more suitable tumor microenvironment. Second, we investigated the feasibility of surgical orthotopic implantation (SOI) of tumor masses to develop a practical liver tumor xenograft mouse model with UM cell lines in 20 mice. Finally, we tried to establish an orthotopic PDX mouse model of liver metastatic UM in 5 mice. We also evaluated concordance for tumor characteristics between pre-implant and post-implant tumors. Our results showed that the liver was a more suitable microenvironment to grow the two UM cell lines compared to the subcutaneous site. UM001 engrafted in the liver, whereas it did not engraft in the subcutaneous site. UM004 displayed more rapid growth in the liver compared to the subcutaneous site. A new SOI of tumor chunk was created to develop a practical liver tumor xenograft model. Donor tumors, which were generated in the liver after injecting UM cell lines, were surgically transplanted into the liver of recipient mice. The new SOI was successfully performed in all 20 mice without adverse events. Recipient mice formed tumors in the liver after SOI. For comparison, the tumor chunks of UM cell lines were also implanted subcutaneously, in which we were able to show that the growth was more rapid in the liver. Both donor and recipient tumors had matching tumor characteristics in histological and proteomic analysis. We established an orthotopic PDX mouse model of liver metastatic UM with a new SOI method. The success rate of engraftment was 80% (4/5) within 6 months. Tumor characteristics of both patient9s original tumors and xenograft mouse tumors matched in histological, genomic and proteomic analysis. This new SOI method can establish a patient-derived liver metastatic uveal melanoma xenograft model in NSG mouse at a highly successful rate. Citation Format: Ken Kageyama, Masahiro Ohara, Kengo Saito, Shinji Ozaki, Mizue Terai, Andrew E. Aplin, Michael J. Mastrangelo, Takami Sato. Feasibility of surgical orthotopic implantation for establishment of patient-derived liver metastatic uveal melanoma xenograft model in NSG mouse. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 623.