Abstract 173: Frequent concomitant epigenetic silencing of the SFRPs and SOX1, Wnt/β-catenin regulators, in human hepatocellular carcinoma

Abstract

Abstract Oncogenic activation of the Wnt/β-catenin signaling pathway is common in hepatocellular carcinoma (HCC). The secreted frizzled-related proteins (SFRPs) function as negative regulators of Wnt signaling and have important implications for carcinogenesis. Recently, we have shown that SFRPs are frequently downregulated through promoter hypermethylation in HCC cell lines and clinical HCC tissues. Furthermore, we have demonstrated that restoration of SFRPs could attenuate Wnt signaling in HCC cells with β-catenin point mutation, decrease abnormal accumulation of free β-catenin in the nucleus, and then suppress cell growth. Sox1 encodes a transcription factor involved in the regulation of embryonic development and cell fate determination. Structurally related to TCF/LEFs, several members of the Sox family, including Sox17, Sox3, Sox7, and Sox9, have also been implicated in repressing β-catenin activity by a mechanism that is not well understood. In this study, we found that the Sox1 was severely down-regulated by quantitative reverse transcription polymerase chain reaction (QRT-PCR). Next, we employed bisulfite modification and methylation-specific PCR (MS-PCR) to analyze the feature of Sox1 promoter methylation in the HCC cell lines and found that the majority of the tested cell lines exhibited hypermethylation. Meanwhile, we also examined sixty primary HCC surgical samples and adjacent nonturmorous liver tissues from Taiwan Liver Cancer Network (TLCN). These results showed that aberrant promoter methylation of SOX1 were found in 32 of 60 HCCs (53.3%), in 13 of 50 cirrhotic livers (26%), and in one of 30 normal control tissues (3.3%). Concomitantly, SFRPs was epigenetically inactivated in HCC cell lines and most of all the tumors with methylated SOX1. A significant correlation between the methylation of both genes was found (p >0.05). Furthermore, overexpression of SOX-1 in HCC cells could suppress TCF-dependent transcriptional activity and suppress colony formation. Taken together, our data suggest that SOX1 is a negative modulator of Wnt/β-catenin signaling, and that SOX1 silencing due to promoter hypermethylation is an early event during tumorigenesis and may contribute to aberrant activation of Wnt signaling in HCC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 173.