Epigenetics of SFRP1: The Dual Roles in Human Cancers

Secreted frizzled-related protein 1 (SFRP1) is a gene that belongs to the secreted glycoprotein SFRP family. SFRP1 has been classified as a tumor suppressor gene due to the loss of expression in various human cancers, which is mainly attributed by epigenetic inactivation via DNA methylation or transcriptional silencing by microRNAs. Epigenetic silencing of SFRP1 may cause dysregulation of cell proliferation, migration, and invasion, which lead to cancer cells formation, disease progression, poor prognosis, and treatment resistance. Hence, restoration of SFRP1 expression via demethylating drugs or over-expression experiments opens the possibility for new cancer therapy approach. While the role of SFRP1 as a tumor suppressor gene is well-established, some studies also reported the possible oncogenic properties of SFRP1 in cancers. In this review, we discussed in great detail the dual roles of SFRP1 in cancers-as tumor suppressor and tumor promoter. The epigenetic regulation of SFRP1 expression will also be underscored with additional emphasis on the potentials of SFRP1 in modulating responses toward chemotherapeutic and epigenetic-modifying drugs, which may encourage the development of novel drugs for cancer treatment. We also present findings from clinical trials and patents involving SFRP1 to illustrate its clinical utility, extensiveness of each research area, and progression toward commercialization. Lastly, this review provides directions for future research to advance SFRP1 as a promising cancer biomarker.

Deregulation of Frizzled Receptors in Hepatocellular Carcinoma

G protein-coupled receptors (GPCRs) have a substantial role in tumorigenesis and are described as a “cancer driver”. Aberrant expression or activation of GPCRs leads to the deregulation of downstream signaling pathways, thereby promoting cancer progression. In hepatocellular carcinoma (HCC), the Wnt signaling pathway is frequently activated and it is associated with an aggressive HCC phenotype. Frizzled (FZD) receptors, a family member of GPCRs, are known to mediate Wnt signaling. Accumulating findings have revealed the deregulation of FZD receptors in HCC and their functional roles have been implicated in HCC progression. Given the important role of FZD receptors in HCC, we summarize here the expression pattern of FZD receptors in HCC and their corresponding functional roles during HCC progression. We also further review and highlight the potential targeting of FZD receptors as an alternative therapeutic strategy in HCC.

Sulfatide epigenetically regulates miR-223 and promotes the migration of human hepatocellular carcinoma cells

BACKGROUND & AIMS

The biological relevance and regulation mechanism of aberrant miR-223 expression in human hepatocellular carcinoma (HCC) remain unknown. Our aim was to investigate miR-223 regulation in HCC.

METHODS

miR-223 and integrin αV dysregulation were verified in 57 HCC specimens. Immunohistochemical analysis of integrin αV and sulfatide levels was performed on another cohort of 103 HCC samples. Epigenetic analysis was used to explore the effect of sulfatide on miR-223 transcription. Orthotopic growth, and intrahepatic and pulmonary metastasis of tumors derived from SMMC-7721 cells expressing miR-223 or cerebroside sulfotransferase were monitored in mice.

RESULTS

miR-223 was reduced in HCC specimens and highly metastatic cell lines. Enhanced miR-223 expression had a negative effect on integrin αV-mediated cell migration. In vivo assays of metastasis in an orthotopically implanted model demonstrated that miR-223 effectively inhibited HCC metastasis. Further analysis demonstrated that integrin αV is negatively regulated by miR-223. Moreover, the integrin αV subunit was significantly positively correlated with highly expressed sulfatide in 103 HCC specimens. Intriguingly, miR-223 expression was suppressed by sulfatide in HCC in association with reduced recruitment of acetylated histone H3 and C/EBPα to the pre-miR-223 gene promoter, where monocytic leukemia zinc finger (MOZ) protein, a MYST-type histone acetyltransferase, lost its attachment. The expression of histone deacetylases, HDAC9 and HDAC10, were greatly stimulated by sulfatide and their recruitment to miR-223 gene promoter was enhanced.

CONCLUSIONS

Downregulation of miR-223 in HCC is associated with the epigenetic regulation by highly expressed sulfatide and involved in tumor metastasis.