Identification of intracellular pathways through which TGF-β1 upregulates URG-4/URGCP gene expression in hepatoma cells

AimsUp-regulated gene 4 (URG-4/URGCP) was strongly expressed in Hepatitis B infected liver and correlated with HBxAG (Hepatitis B x Antigen) protein and found to promote hepatocellular cancer. Transforming growth factor (TGF-β1) is a multifunctional protein that effects cell proliferation, growth inhibition, differentiation and other functions. However, the mechanism of URG-4/URGCP regulation by TGF-β1 and its significance in cancer progression remains largely unknown.Main methodsThe effect of TGF-β1 on URG-4/URGCP gene was determined using REAL TIME PCR at mRNA level and Western blotting/immunofluorescence at protein level. Transient transfection assays were carried out to find out which site of promoter is upregulated by TGF-β1.Key FindingsWe report the upregulation of URG-4/URGCP gene expression by TGF-β1 in hepatoma cells along with prostate cancer cells, PC3. Transient transfection assays showed that the − 109 to + 63 promoter region contained the minimal TGF-β1 response elements. TGF-β1 markedly stimulated the URG-4/URGCP mRNA and protein that was blocked by MEK1 [MAPK (Mitogen-Activated Protein Kinase)/ERK (extracellular signal-regulated kinase) kinase 1] inhibitor, PD98059 and PI3K inhibitor, wortmannin.SignificanceThese studies show for the first time that TGF-β1 upregulates the expression of URG-4/URGCP in human hepatocytes and identifies the signaling pathways underlying this response.