Abnormal expression of proteins in Notch and Wnt pathways in human squamous cell carcinoma of the skin

• Background Members of the Notch pathway are involved in various differentiation processes. Signalling via the Wnt/ß-catenin-pathway controls transcription of genes involved in proliferation events. These two pathways are interconnected through the cytoplasmic protein Dishevelled (Dvl-1).Objectives To evaluate the expression patterns of Notch1, Dvl-1 and ß-catenin proteins in human squamous cell carcinomas of the skin.Methods 40 formalin-fixed paraffin-embedded SCCs were included in this study. Expression was detected with immunohistochemistry using avidin-biotin and DAB visualization.Results The majority of the normal epidermal cells lacked expression of Notch1, while the dysplastic and invasive tumour cells showed strong staining. Expression of Dvl-1 was observed in normal human epidermis, with a more intense staining indysplastic cells in 8 of 38 (21%) cases. Besides the expected cytoplasmic staining, 27 of 38 (71%) secs displayed nuclear staining and a potential nuclear localisation signal was identified. ß-catenin showed membranous and weak cytoplasmic staining in normal as well as tumour cells.Conclusions We have found enhanced expression of Notch1 in the majority of SCCs, indicating a disturbed differentiation process. We have also for the first time showed over-expression of Dvl-1 in dysplastic epidermal cells as well as normal staining of the nucleus. A classical nuclear localization signal is also identified in the Dvl-1 isoform A, whereas two other isoforms lack this recognition sequence.

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