Direct activation of TGF‐β1 transcription by androgen and androgen receptor complex in Huh7 human hepatoma cells and its tumor in nude mice

Abstract

Importance of androgen for promotion of hepatocelullar carcinoma (HCC) has long been supported by clinical and experimental evidences. However, mechanisms involved in the carcinogenesis have not yet been fully elucidated. Moreover, unbalanced expression of TGF-b1 during tumor progression results in prooncogenic rather than growth inhibition. To investigate the effect of androgen on transcriptional regulation of TGF-b1, we isolated rat TGF-b1 promoter, based on our previous report (GenBank AF249327), and examined regulation of its promoter activity by dihydrotestosterone in Huh7, LNCaP, and PC3 cells. Several putative transcription factor-binding sites were found, but no TATA box. When the full-length (À4784 to þ68) and variously deleted promoter DNAs were evaluated, the promoter region spanning from À2732 to À1203 showed the highest activity towards dihydrotestosterone in a dose-dependent manner in both Huh7 and PC3 cells with androgen receptor (AR) expression. Putative androgen response sequence half site (5 0 -TGTCCT-3 0 ) was identified to be located within À1932 to À1927, proved by mutant (5 0 -AGACCT-3 0 ) analysis and chromatin immunoprecipitation (ChIP) assay. AR mediated upregulation of TGF-b1 expression was confirmed by HCC developed in nude mice with AR-overexpressed Huh7-cells. This work presents in vivo and in vitro evidences of activation of TGF-b1 expression by androgen and AR, and implicates the modulation of hepatocarcinogenesis by AR through the regulation of TGF-b1 expression.

Hepatitis C Virus Core Protein Augments Androgen Receptor-Mediated Signaling

“…1A). Our results are in agreement with the recent reports that differential AR expression occurs in hepatocytes (51,61). Since Huh-7 and IHH cell lines support HCV growth (21,55), we chose to use these two cell lines for subsequent studies.…”

“…Binding of androgen to the ligand-binding domain induces conformational change in AR and leads to the shuttling of receptor from the cytoplasm to the nucleus, where it forms a homodimer and is recruited to the AR element (ARE). ARE is present in the regulatory elements on the target genes such as vascular endothelial growth factor (VEGF) and transforming growth factor ␤1 and regulates the growth and proliferation of hepatocytes (6,51).…”

Overexpression of the androgen receptor in human hepatoma cells and its effect on fatty acid metabolism

“…In patients with HCC, the alterations in lipid and lipoprotein metabolism can be clearly observed (30). AR has been demonstrated to be associated with hepatocarcinogenesis and HCC development (1,3,(5)(6)(7)9,10). The present study revealed that AR could serve a role in hepatocarcinogenesis via the regulation of hepatocellular fatty acid metabolism.…”

“…AR is a transcription factor activated via ligand-dependent and ligand-independent mechanisms (8). Cytochrome P450, transforming growth factor β1, vascular endothelial growth factor A and heat shock protein family A member 5 are target genes of ARs in the liver (3,7,9,10). Crosstalk between ARs and liver X receptor (nuclear receptor subfamily 1 group H member 2) has also been implicated in maintaining cholesterol homeostasis (11).…”

Androgen Receptor and Hepatocellular Carcinoma

“…ARE is present in regulatory elements on target genes such as vascular endothelial growth factor (VEGF) and transforming growth factor beta-1, and regulates the growth and proliferation of hepatocytes [11,12]. Sorafenib, a molecular-targeted agent that inhibits tumor cell proliferation and angiogenesis by inhibiting Raf serine-threonine kinase (MAPKK kinase, MAPKKK), and VEGF, platelet-derived growth factor beta (PDGF), fms-related tyrosine kinase 3 (FLT3), and v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (C-Kit) receptor tyrosine kinase, was approved for treatment of advanced HCC in Europe, USA, Japan and other countries [13,14].…”