SULF1 - Role in Cancer - Hepatocellular Carcinoma

Hepatocellular Carcinoma

Cancer cell lines with downregulation of Sulf1 were investigated in the same fashion as ovarian cancer. Nine of 11 hepatocellular carcinoma (HCC) cell lines displayed either absent or severely reduced levels of Sulf1 mRNA. Less than half of HCC tumor samples showed loss of heterozygosity (LOH), and DNA methylation inhibition treatment of Sulf1 absent HCC cell lines reactivated the expression of Sulf1, indicating hypermethylation may be partly responsible for its downregulation. As in ovarian cancer, loss of Sulf1 largely contributed to decreased HPSG sulfation in HCC. In addition, Sulf1 expression is required to suppress sustained activation of ERK1/2 and c-met by the heparin binding growth factors (HB-GF), fibroblast growth factor (FGF) and hepatocyte growth factor (HGF), thereby decreasing cell proliferation. In extension, Sulf1 mediated HCC cell apoptotic sensitivity to cisplatin and staurosporine. As a review, HGF, or scatter factor, activates its receptor c-Met which activates mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) and PI3K signaling that are ultimately responsible for expression of proangiogenic factors, interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF). The HGF/c-Met axis mediates the invasive growth phenotype necessary for metastasis through coordination of cell motility and degradation of extracellular matrix (ECM).

In vivo studies on HCC found Sulf1 overexpressing HCC xenografts displayed delayed tumor growth in mice, and the mechanism involves inhibition of histone deacetylase (HDAC). Sulf1 enhances acetylation of Histone H4 by inhibiting HDAC, which subsequently inhibits the activation of the MAPK and Akt pathways ultimately decreasing HCC tumorogenesis.

Sulf2’s role in HCC contrasted with Sulf1. Sulf2 was upregulated in a majority of HCCs and HCC cell lines, and Sulf2 knockdown eliminated migration and proliferation. Sulf2 also upregulated glypican-3, which is commonly overexpressed in HCC, by increasing ERK, AKT activation through enhanced FGF2 signaling. GPC3 is important in Sulf2-enhanced FGF signaling in vitro, so glypican-3 may mediate its own upregulation through Sulf2. Given that Sulf1 and Sulf2 have redundant functions, Sulf2 contrasting function in HCC was unexpected.