sFRP-4

The expression and levels of secreted frizzled-related proteins (sFRPs), important Wnt signalling antagonists, have been reported to be reduced in various cancers, and are associated with disease progression and poor prognosis. During tumour development, all sFRP (1, 2, 3, 4, and 5) genes are hypermethylated, causing transcriptional silencing. sFRPs have an ability to sensitize tumour cells to chemotherapeutic drugs, enhancing cell death. Reduced Wnt signalling is associated with loss of cancer stem cell (CSC) viability. We investigated the possible involvement of methylation-mediated silencing of the sFRP gene family in CSCs derived from breast, prostate, and ovarian tumour cell lines. Real-time RT-PCR studies indicated that loss or downregulation of sFRP (1-5) expression in tumours is associated with promoter hypermethylation. Additionally, CSCs derived from all tumour cell lines with sFRP (1-5) promotor hypermethylation expressed sFRP (1-5) mRNA after treatment with 5-Azacytidine (5-Aza), especially sFRP4, implying that DNA methylation is the predominant epigenetic mechanism for sFRP (1-5) silencing. Furthermore, post-translational modification (PTM) in total and histone proteins was observed post 5-Aza and sFRP4 treatment. Protein levels of Wnt downstream signalling components (GSK3β, active β-catenin, and phospho β-catenin) and epigenetic factors of histones (acetyl histone H3, and H3K27me3) affecting PTM were analysed. Our findings suggest that downregulation of sFRP4 expression in endocrine-related cancers can be attributed to aberrant promoter hypermethylation in conjugation with histone modification, and indicate the important role of methylation-induced gene silencing of sFRP4 in survival and proliferation of CSCs derived from these cancers.

Expression of the Wnt modulator secreted frizzled related protein 4 (Sfrp4) is upregulated after heart ischemic injury. We show that intramuscular administration of recombinant Sfrp4 to rat heart ischemic injury and recanalization models prevents further deterioration of cardiac function after the ischemic injury. The effect of Sfrp4 persisted for at least 20 weeks when Sfrp4 was administered in a slow release system (Sfrp4-polyhedra) to both acute and subacute ischemic models. The histology of the dissected heart showed that the cardiac wall was thicker and the area of acellular scarring was smaller in Sfrp4-treated hearts than in controls. Increased amounts of both the inactive serine 9-phosphorylated form of glycogen synthase kinase (GSK)-3β and the active form of β-catenin were observed by immunohistology 3 days after lateral anterior descendant ligation in control, but not in Sfrp4-treated hearts. All together, we show that administration of Sfrp4 interferes with canonical Wnt signaling that could mediate the formation of acellular scar and consequently contributes to the prevention of aggravation of cardiac function.