ABSTRACT: Hepatocyte dedifferentiation is a major source of hepatocellular carcinoma (HCC), but its mechanisms are unknown. We explored the p73 expression in HCC tumors and studied the effects of transcriptionally active p73 (TAp73) in HCC cells. Expression profiles of p73 and patient clinical data were collected from the Genomic Data Commons (GDC) data portal and the TSVdb database, respectively. Global gene expression profiles were determined by pan-genomic 54K microarrays. The Gene Set Enrichment Analysis was used to identify TAp73-regulated gene sets. The effects of TAp73 were analyzed in monolayer cell culture, 3D-tumoroid and xenograft models in zebrafish using western blot, flow cytometry, fluorescence imaging, real-time polymerase chain reaction (RT-PCR), immunohistochemistry and morphological examination. TAp73 was significantly upregulated in HCC, and its high expression indicated poor patient survival. The induced expression of TAp73 caused landscape expression changes including genes involved in growth signaling, cell cycle, stress response, immunity, metabolism and development. HCC cells overexpressing TAp73 had lost hepatocyte lineage biomarkers including ALB, CYP3A4, AFP, HNF4α. In contrast, TAp73 upregulated genes promoting cholangiocyte lineage such as YAP, JAG1 and ZO-1, accompanied with an increase in metastatic ability. Our findings strongly suggest that TAp73 is a major promoter of malignant dedifferentiation of HCC cells Hepatocellular carcinoma (HCC) is a highly complex and heterogeneous type of cancer. Hepatocyte dedifferentiation is one of the important steps in the development of HCC. However, its molecular mechanisms are not well known. In this study, we report that TAp73 which is the major transcriptionally active form of p73 is overexpressed in HCC. Mechanically, TAp73 suppresses the expression of the hepatocyte markers including CYP3A4, AFP, ALB, HNF4a, while increasing the expression of several cholangiocyte markers in HCC cell lines. In conclusion, this report reveals a pro-oncogenic role for TAp73 in liver cancer.
