Oncopig soft-tissue sarcomas recapitulate key transcriptional features of human sarcomas

K.M. Schachtschneider, Y. Liu, S. Makelainen, O. Madsen, L.A. Rund, M.A.M. Groenen, R.M. Schwind, R.C. Gaba, L.B. Schook
American Association for Cancer Research Annual Meeting, April 2017, Washington D.C.

Human soft-tissue sarcomas (STS) are rare, aggressive mesenchymal tumors with a late stage 5-year survival rate (50-60%) that has for decades remained unchanged. Research into STS treatment is hampered by the limited human STS cell line availability and the large number of STS subtypes. Therefore, there is a need to develop STS cell lines and animal models representative of diverse human STS subtypes. Pigs represent ideal human disease models due to their similar size, anatomy, metabolism, genetics, and epigenetics compared to humans. In this regard, porcine cancer models provide the opportunity to produce STS cell lines and in vivo tumors similar to those clinically observed in humans. The Oncopig encodes Cre recombinase inducible porcine transgenes encoding KRASG12D and TP53R167H, allowing the Oncopig to model a number of human sarcomas in an inducible and temporal manner. However, comparative analysis is required to determine to what extend the Oncopig STS model mimics human STS on a molecular level. The purpose of this study was to identify similarities between Oncopig and human STS transcriptional profiles to validate the Oncopig model as a viable model for human STS. Towards this end, Oncopig fibroblasts were isolated from ear notches of 4 Oncopigs and cultured in vitro. Following confirmation of their mesenchymal origin (positive vimentin immunostaining), Oncopig fibroblasts were transformed via Cre recombinase exposure, resulting in the formation of Oncopig STS cell lines. Oncopig STS tumors were produced in vivo through intramuscular injection of adenovirus encoding Cre in 2 Oncopigs (2 sites/Oncopig), resulting in the formation of 4 tumors detectable by 10 days post injection. The mesenchymal origin of the resulting tumors was confirmed through histological characterization. Genome-wide expression of Oncopig STS cell lines and tumors was profiled via RNA-seq. Reproducible Oncopig STS cell line and tumor expression profiles were observed, and Oncopig STS cell lines also displayed high temporal reproducibility. Differential expression analysis was performed by comparing Oncopig STS cell lines and tumors to untransformed fibroblasts and skeletal muscle, respectively. A total of 3,360 and 7,652 differentially expressed genes were identified in the Oncopig STS cell lines and tumors, respectively. Commonly identified alterations in human STS gene expression and pathway regulation were identified in Oncopig STS, including altered TP53 signaling, activation of Wnt signaling, and evidence of epigenetic reprogramming. Furthermore, master regulators of Oncopig STS gene expression were identified, including FOSL1, which was previously identified as a potential therapeutic target for human STS. These results demonstrate the Oncopig STS model’s ability to mimic human STS on a transcriptomic level, making the Oncopig a valuable resource for sarcoma research and cell line development.