In addition, the immunoreactivity of cytokeratin 19 (Ck19), a marker of biliary lineage cells, was significantly decreased in pten;tp53 cKO fish (Fig. 4e), suggesting that the absence of biliary ducts in liver tumours excluded the origin of biliary lineage cells, consistent with the symptoms of HCC in humans. The gene discussed is TP53; the disease is hepatocellular carcinoma.