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Abstract: Wnt inhibitory factor-1 (WIF-1) is a secreted protein that antagonizes Wnt signaling. We recently demonstrated the importance of aberrant activation of the Wnt signaling pathway in various cancers including malignant pleural mesothelioma. In this study, we revealed downregulated WIF-1 expression in cell lines and primary tissue when compared to normal mesothelial cell lines and adjacent pleura, respectively. We observed hypermethylation in four of four mesothelioma cell lines, but not in two normal mesothelial cell lines. In primary tissue samples, we observed methylation in three paired tumor specimens compared to their adjacent normal pleura and methylation in eight of nine unpaired tumor tissue samples. Taken together, our studies suggest that WIF-1 silencing due to its promoter hypermethylation is an important mechanism underlying the constitutively activated Wnt signaling in mesothelioma. New therapies toward inhibition of the Wnt pathway through WIF-1 might be promising for the future treatment of malignant mesothelioma. [Copyright &y& Elsevier]

Abstract: Aberrant activation of Wingless-type (Wnt) signaling pathway plays a critical role in oncogenesis of various human cancers. Wnt inhibitory factor-1 (WIF-1) is a secreted antagonist of Wnt signaling and acts through direct binding to Wnt in the extracelllular space. Recently, we reported Wnt signaling in various human malignancies. In addition, we identified in lung cancer that WIF-1 is silenced due to promoter hypermethylation. In this study, we found constitutive activation of Wnt signaling and WIF-1 silencing in nasopharyngeal carcinoma (NPC) cell lines. Furthermore, by utilizing methylation-specific PCR and sequence analysis, we demonstrated that frequent hypermethylation of the WIF-1 promoter correlates with WIF-1 silencing in NPC cell lines. Our results indicate that aberrant Wnt signaling is a common event in NPC carcinogenesis linked with WIF-1 silencing in at least cell lines. Strategies targeting these molecules should be potentially promising in treating NPC. [Copyright &y& Elsevier]