Cloning and characterization of the promoter of human Wnt inhibitory factor-1

Abstract

Wnt inhibitory factor-1 (WIF-1) is a secreted antagonist of Wnt signaling and functions by directly binding to Wnt ligands in the extracellular space. Here we report the identification of the 5′ promoter region (∼1.5 kb) of the human WIF-1 gene. Functional analysis of this region shows that a whole fragment displays high basal promoter activity in different cell lines, while the truncated forms do not, indicating that integrity of the WIF-1 promoter region may be important for WIF-1 activity. Moreover, we found that the expression level of β-catenin in cancer cell lines correlates with the WIF-1 promoter activity, suggesting that the WIF-1 promoter may be regulated by the Wnt/β-catenin pathway and may function in a negative feedback manner. Our results also suggest that a methylated CpG island, which we observed recently in human lung cancer, lies within the functional WIF-1 promoter region and therefore bears the importance of the methylation-status of this CpG island as an important key in Wnt activation in human cancer.