WIF1 Suppresses the Generation of Suprabasal Cells in Acanthotic Skin and Growth of Basal Cell Carcinomas upon Forced Overexpression

We analyzed the role of WIF1 in normal and acanthotic epidermis of 12-O-tetradecanoylphorbol-13-acetate (TPA) or all-trans-retinoic acid (ATRA)-treated and basal cell carcinoma (BCC)-bearing mice. WIF1 protein is located in the follicular infundibulum and interfollicular epidermis (IFE) in murine back skin. Within the hyperplastic epidermis of TPA- or ATRA-treated or BCC-bearing murine skin, WIF1 and Keratin 10 overlap in Ki67(-) suprabasal layers, while basal epidermal layers expressing Ki67, and BCCs expressing Wif1 mRNA, are free of WIF1 protein. This is similar in human skin, with the exception that WIF1 protein is found in single Ki67(-) basal epidermal cells in normal skin and additionally in Ki67(+) cells in acanthotic skin. Wif1-deficiency enhances acanthosis of the murine BCC-associated epidermis, which is accompanied by an increase of Ki67(+) and of Sca1(+) basal cells. WIF1 overexpression in allografted BCC-derived keratinocytes prevents growth and keratinization, involving enhanced phosphorylation of protein kinase C and extracellular signal-regulated kinase 1 and arguably factors secreted by the in vivo environment. In summary, WIF1 protein marks suprabasal layers in the normal IFE. It is also present in the epidermis overlaying BCCs where it diminishes proliferation of basal cells and production of differentiating suprabasal cells. In addition, WIF1 can prevent proliferation and keratinization of BCC-related keratinocytes.