The Oncopig hepatocellular carcinoma model: An innovative large animal platform for evaluating treatment effects.

619 Background: Hepatocellular carcinoma (HCC) is an aggressive disease associated with poor prognosis and limited treatment options. Systemic therapies for advanced HCC include sorafenib, lenvatinib, and atezolizumab plus bevacizumab. However, given the limited efficacy of systemic treatment options, novel treatment approaches including combination of systemic and locoregional therapies (LRTs) is required to improve patient outcomes. These approaches require advanced large animal models to prove effectiveness. Pigs represent an ideal platform that provide both regulatory acceptable and clinically relevant large animal cancer models due to their similar physiology, size, genetics, immunity, and metabolism in relation to humans. The Oncopig HCC model is an ideal tool for testing LRT and other oncolytic based treatments. Methods: The Oncopig cancer model develops tumors following induced expression of KRAS G12D and TP53 R167H driver mutations utilizing an adenoviral vector encoding Cre recombinase (AdCre). Oncopig HCC cell lines were developed by isolating hepatocytes from Oncopig liver biopsies and transformed in vitro via exposure to AdCre. Transgene expression and hepatocyte cell origin were validated by RT-PCR and arginase-1 staining, respectively. Comparison of in vitro Oncopig, human, and murine HCC cell line phenotypes (proliferation, migration, and chemotherapeutic response) was performed. Oncopig HCC tumor formation was performed via autologous intrahepatic injection of Oncopig HCC cells. Tumor formation was evaluated using ultrasound and CT imaging. Results: Oncopig and human HCC cell lines displayed similar cell cycle lengths and migration rates. Oncopig HCC cells were consistently more predictive of human HCC responses than murine cells when treated with standard chemotherapeutic agents (doxorubicin, cisplatin, mitomycin C, and sorafenib). Importantly, consistent with human HCC, Oncopig HCC cells were non-responsive to 5-fluorouracil, while murine HCC cells were responsive. Intrahepatic injection of Oncopig HCC cells resulted in tumors visible on ultrasound and CT scan within 2-4 weeks. Resulting tumors were consistent with human tumors on imaging. Histological analysis of tumor biopsies confirmed the identity of the resulting masses as HCC tumors based on positive arginase-1 and KRAS G12D staining. Conclusions: The Oncopig HCC model may be more predictive of human HCC chemotherapeutic responses than currently employed murine models. Tumors develop rapidly (within 2-4 weeks) and are readily identified on ultrasound and CT imaging, making this an ideal model for evaluation of novel therapeutic approaches. Further exploration and development of additional tumor models including further translational characterization will be important for broader utility.