Role of hepatoma-derived growth factor in promoting de novo lipogenesis and tumorigenesis in hepatocellular carcinoma.

Although identified as a growth factor, the mechanism by which hepatoma-derived growth factor (HDGF) promotes cancer development remains unclear. We found that nuclear but not cytoplasmic HDGF is closely associated with prognosis of hepatocellular carcinoma (HCC). RNA-sequencing analysis further demonstrated that the nuclear role of HDGF involved regulation of transcription of lipid metabolism genes. HDGF-induced expression of lipogenic genes was mainly associated with activation of sterol regulatory element binding protein (SREBP) transcription factor. Coexpression of SREBP-1 and nuclear HDGF predicts poor prognosis for HCC. In addition, by changing the first amino acid of the PWWP domain from proline to alanine, the type of PWWP domain changed from P- to A-type, resulting in inability to induce SREBP-1-mediated gene transcription. The type of PWWP domain affects the recruitment of the C-terminal binding protein-1 transcriptional repressor on the promoter of the lipogenic gene. Our data indicate that HDGF acts as a coactivator of SREBP1-mediated transcription of lipogenic genes. The PWWP domain is crucial for HDGF to promote lipogenesis. Moreover, transcriptional regulation of nuclear HDGF plays important roles in the development of HCC.