Activation of the TGFβ/SMAD Transcriptional Pathway Underlies a Novel Tumor Promoting Role of Sulfatase1 in Hepatocellular Carcinoma*

In vitro studies have proposed a tumor suppressor role for Sulfatase1 (SULF1) in hepatocellular carcinoma (HCC), however high expression in human HCC has been associated with poor prognosis. The reason underlying this paradoxical observation remains to be explored. Using a transgenic (Tg) mouse model overexpressing Sulf1 (Sulf1-Tg) we assessed the effects of SULF1 on the diethylnitrosamine (DEN) model of liver carcinogenesis. Sulf1-Tg mice show higher incidence of large and multifocal tumors with DEN injection compared to wild type (WT) mice. Lung metastases were found in 75% of Sulf1-Tg mice but not in WT mice. Immunohistochemistry (IHC), immunoblotting and reporter assays all show a significant activation of the TGFβ/SMAD transcriptional pathway by SULF1 both in vitro and in vivo. This effect of SULF1 on TGFβ/SMAD pathway is functional; overexpression of SULF1 promotes TGFβ-induced gene expression and epithelial-mesenchymal-transition (EMT), and enhances cell migration/invasiveness. Mechanistic analyses demonstrate that inactivating mutation of the catalytic site of SULF1 impairs the above actions of SULF1 and diminishes the release of TGFβ from the cell surface. And we also show that SULF1expression decreases the interaction between TGF-β1 and its HSPG sequestration receptor TGFβR3. Finally, using gene expression from human HCCs, we show that patients with high SULF1 expression have poorer recurrence-free survival (HR 4.1 (1.9–8.3); p=0.002) compared to patients with low SULF1. We also found strong correlations of SULF1 expression with TGFβ expression and with several TGFβ-related EMT genes in human HCC. CONCLUSION In summary, our study proposes a novel role of SULF1 in HCC tumor progression through augmentation of the TGFβ pathway, thus defining SULF1 as a potential biomarker for tumor progression and a novel target for drug development for HCC.