Abstract 4378: Discovery and characterization of two novel drivers of hepatocellular carcinoma

Liver cancer is globally the sixth most commonly diagnosed and the third most deadly cancer. Hepatocellular carcinoma (HCC) is the most common form of the disease and a difficult cancer to treat due to inadequately understood pathways involved in tumorigenesis and progression. To obtain a better understanding of key HCC driver mutations, we performed a forward genetic screen using Sleeping Beauty transposon mutagenesis in a damaged liver microenvironment. Briefly, T2Onc3; Rosa26-SB11^lsl/lsl;Alb-Cre mice were treated with carbon tetrachloride (CCl₄) during ongoing transposition. We then sequenced the resulting liver tumors using linker mediated PCR (LM-PCR) and Illumina sequencing. We analyzed the sequenced data using gene-centric common insertion site (gCIS) analysis that allowed us to determine common insertion sites across tumors. These common insertion sites are referred to as candidate driver mutations.

This screen demonstrated the role of Glioma associated protein-2 (Gli2) and Fidgetin (Fign) as candidate driver mutations in a significant subset of HCC tumors (20% and 10% respectively). Gli2 is a key member of the Hedgehog signaling pathway, acting as a transcription factor for genes promoting cell proliferation. Fign is a relatively uncharacterized protein in the AAA-ATPase family with the ability to sever microtubules in vitro. We validated Gli2 as a driver of HCC by generating a hepatocyte specific Gli2-overexpression mouse model using hydrodynamic tail vein injection of Gli2 cDNA into FAH-/- mice. Mice underwent rapid tumorigenesis, regardless of CCl₄ treatment, demonstrating that Gli2 is a strong oncogene. Additionally we have demonstrated that overexpression of Fign drives cell proliferation and promotes stabilization of the primary cilium in hepatocytes, a novel finding that provides insight into the mechanism of Fign-driven HCC.

The discovery of two novel HCC candidate driver mutations, validation of Gli2 as a bona fide HCC oncogene, and mechanistic insight into these commonly mutated genes in HCC will allow for future research into understanding HCC tumorigenesis and potential therapeutic options.

Citation Format: Charlotte R. Feddersen, Adam J. Dupuy. Discovery and characterization of two novel drivers of hepatocellular carcinoma. [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 4378.