The oncopig cancer model as a validated model for human hepatocellular carcinoma

K.A. Darfour-Oduro, A.K. De, L.A. Rund, R.C. Gaba, C.E. Ray, R.M. Schwind, K.M. Schachtschneider, K.B. Singh, L.B. Schook
American Association for Cancer Research Annual Meeting, April 16-20, 2016, New Orleans, LA

Human hepatocellular carcinoma (HCC) is the fifth most common cancer globally and is the third most common cause of cancer-related deaths worldwide, accounting for more than 600,000 deaths each year. While the information gained from human clinical trials may enhance the efficacy of HCC treatment, such trials provide limited capability for investigation into the processes contributing to procedural effectiveness and disease progression. Immunological, genetic and physiological differences between rodents and humans represent major limitations for the use of rodent based cancer models in HCC studies. Pigs represent an attractive model given that they share many genetic, anatomical, and physiological similarities with humans. In a previous study, we demonstrated the functionality of a porcine inducible model of cancer (Oncopig; Schook et. al., 2015). In order to develop and validate the Oncopig HCC model, we established primary (control) hepatocyte cultures from 3 individual Oncopigs and transformed them with Cre recombinase (HepCre). Within a week the activated cells began to proliferate, taking on transformed morphologic characteristics. Transcriptional analysis confirmed both the primary and transformed cells expressed hepatocyte specific marker genes (albumin, HNF4 and G6P). The Cre treated cell lines also expressed oncogenic P53R167H and KrasG12D. Each of the three transformed cell lines were then injected into the livers of SCID mice to verify tumorigenicity. SCID mice (9/9) developed tumors that recapitulated several morphological similarities with human HCC including cellular arrangement and marked pleomorphism. The primary hepatocytes expressed cytokeratin and the HepCre cell lines expressed both cytokeratin and vimentin, indicative of an epithelial-mesenchymal transition, which is a common tumor progression signal observed in human HCC and other highly proliferative carcinomas. Alpha-fetoprotein is often found in the serum of HCC patients and was measurable in the medium of porcine HepCre cells but not primary hepatocytes. Oncopig HCC cells were polygonal with eosinophilic granular cytoplasm as observed in human HCC. Principal component analysis of gene expression data showed clear separation between the primary hepatocytes and HepCre cells. Differential expression analysis revealed upregulation of proto-oncogenes and downregulation of tumor supressor genes in the HepCre cells, as well as enrichment of several pathways that are concordantly dysregulated in human HCC, including the TP53 pathway, fatty acid metabolism pathway and complement and coagulation cascade pathway. These data demonstrate the utility of the Oncopig model in terms of relevance to human HCC and therefore aid in improved detection, treatment, biomarker discovery for liver tumors and other unmet clinical needs.