Liver cancer is the 3rd leading cause of cancer-related deaths worldwide, and represents a substantial and increasing health burden. As current therapeutic interventions offer limited survival improvements to patients, there is a critical need for the development of new and effective treatments. Multiple genes and molecular pathways, including RAS/MAPK signalling, are recurrently altered during oncogenic transformation. Epigenetic modifications, such as DNA and histone methylation, regulate many of these pathways fundamental to the genesis of cancer. Our study focuses on investigating the core oncogenic pathways in hepatocarcinogenesis.
Zebrafish provide a highly advantageous platform for in vivo drug discovery due to their small size, rapid maturation, optical transparency and high-throughput capabilities. We have utilised an inducible zebrafish hepatocellular carcinoma (HCC) model to identify and validate potential therapeutic targets. Upon the addition of doxycycline, an oncogenic version of kras fused to EGFP is expressed specifically in the liver. This results in hepatocyte hyperproliferation and liver enlargement. Through the application of 2-photon microscopy, the volume of normal and hyperplastic livers can be imaged in vivo and accurately quantitated.
Using this approach, we have shown that heterozygous mutations in genes participating in U12-dependent (minor class) splicing, ribosome biogenesis and nuclear pore formation significantly restrict krasG12V-mediated liver overgrowth. Since these heterozygous mutations do not affect normal liver development, these experiments suggest that drugs designed to disrupt these processes may provide a therapeutic window that could be exploited clinically to restrict the growth of cancer cells without affecting surrounding healthy cells. Accordingly, we have utilised this model to evaluate the effectiveness of numerous drug treatments. Specifically, we have demonstrated that EPZ015666, an inhibitor of the protein arginine methyltransferase, PRMT5, has potent anti-proliferative activity, reducing liver hyperplasia. This study highlights the use of the zebrafish HCC model to identify and develop novel targeted therapies against cancer.