The Wnt‐signaling pathway is not implicated in tumorigenesis of Merkel cell carcinoma

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Abstract
Background: The Wnt‐signaling pathway, involving β‐catenin, apc, and axin, plays a critical role in numerous developmental events. Alterations in the Wnt‐signaling pathway have been detected in a wide variety of neoplasms. However, similar aberrations have not been described in Merkel cell carcinoma (MCC). The aim of this study was to determine the status of the Wnt‐signaling pathway in MCC. Methods: Twelve cases of MCC were tested for the expression of β‐catenin and mutational status of CTNNB1 (gene for β‐catenin), APC, AXIN1, and AXIN2. Genomic DNA extracted from paraffin blocks was subjected to a polymerase chain reaction/single‐strand conformation polymorphism analysis and sequencing. Results: Nuclear accumulation of β‐catenin was observed in only one case (8.3%), as determined by immunochemistry. No mutations were found in CTNNB1, APC, and AXIN2 in all cases, although silent mutations in AXIN1 were detected in three cases. Conclusions: We conclude that the Wnt‐signaling pathway does not play an important role in tumorigenesis in MCC.