Dhanasekaran Renumathy, Nakamura Ikuo, Hu Chunling, Chen Gang, Oseini Abdul M, Seven Elif Sezin, Miamen Alexander G, Moser Catherine D, Zhou Wei, van Kuppevelt Toin H, van Deursen Jan M, Mounajjed Taofic, Fernandez-Zapico Martin E, Roberts Lewis R
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN.
Hepatology. 2015 Apr;61(4):1269-83. doi: 10.1002/hep.27658. Epub 2015 Feb 13.
In vitro studies have proposed a tumor suppressor role for sulfatase 1 (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 model of liver carcinogenesis. Sulf1-Tg mice show a higher incidence of large and multifocal tumors with diethylnitrosamine injection compared to wild-type mice. Lung metastases were found in 75% of Sulf1-Tg mice but not in wild-type mice. Immunohistochemistry, immunoblotting, and reporter assays all show a significant activation of the transforming growth factor-β (TGF-β)/SMAD transcriptional pathway by SULF1 both in vitro and in vivo. This effect of SULF1 on the TGF-β/SMAD pathway is functional; overexpression of SULF1 promotes TGF-β-induced gene expression and epithelial-mesenchymal transition 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 TGF-β from the cell surface. We also show that SULF1 expression decreases the interaction between TGF-β1 and its heparan sulfate proteoglycan sequestration receptor, TGFβR3. Finally, using gene expression from human HCCs, we show that patients with high SULF1 expression have poorer recurrence-free survival (hazard ratio 4.1, 95% confidence interval 1.9-8.3; P = 0.002) compared to patients with low SULF1. We also found strong correlations of SULF1 expression with TGF-β expression and with several TGF-β-related epithelial-mesenchymal transition genes in human HCC.
Our study proposes a novel role of SULF1 in HCC tumor progression through augmentation of the TGF-β pathway, thus defining SULF1 as a potential biomarker for tumor progression and a novel target for drug development for HCC.
体外研究表明硫酸酯酶1（SULF1）在肝细胞癌（HCC）中具有肿瘤抑制作用；然而，SULF1在人类HCC中的高表达却与预后不良相关。这一矛盾观察结果背后的原因仍有待探索。我们利用过表达Sulf1的转基因（Tg）小鼠模型（Sulf1-Tg），评估了SULF1对二乙基亚硝胺诱导的肝癌发生模型的影响。与野生型小鼠相比，注射二乙基亚硝胺后，Sulf1-Tg小鼠出现大的多灶性肿瘤的发生率更高。75%的Sulf1-Tg小鼠发生了肺转移，而野生型小鼠未出现肺转移。免疫组织化学、免疫印迹和报告基因检测均显示，SULF1在体外和体内均能显著激活转化生长因子-β（TGF-β）/SMAD转录通路。SULF1对TGF-β/SMAD通路的这种作用具有功能性；SULF1的过表达促进TGF-β诱导的基因表达和上皮-间质转化，并增强细胞迁移/侵袭能力。机制分析表明，SULF1催化位点的失活突变会损害SULF1的上述作用，并减少TGF-β从细胞表面的释放。我们还发现，SULF1的表达降低了TGF-β1与其硫酸乙酰肝素蛋白聚糖隔离受体TGFβR3之间的相互作用。最后，利用人类HCC的基因表达数据，我们发现，与SULF1低表达的患者相比，SULF1高表达的患者无复发生存期更差（风险比4.1，95%置信区间1.9 - 8.3；P = 0.002）。我们还发现，在人类HCC中，SULF1的表达与TGF-β的表达以及几个与TGF-β相关的上皮-间质转化基因之间存在很强的相关性。
我们的研究提出SULF1在HCC肿瘤进展中通过增强TGF-β通路发挥新作用，从而将SULF1定义为肿瘤进展的潜在生物标志物和HCC药物开发的新靶点。
