Differential Regulation of a Fibroblast Growth Factor–Binding Protein during Skin Carcinogenesis and Wound Healing1

The initiation of premalignant lesions is associated with subtle cellular and gene expression changes. Here we describe a severe combined immunodeficient mouse xenograft model with human adult skin and compare chemical carcinogenesis and wound healing. We focus on a secreted binding protein for fibroblast growth factors (FGF-BP) that enhances the activity of locally stored FGFs and is expressed at high levels in human epithelial cancers. Carcinogen treatment of murine skin induced papilloma within 6 weeks, where-as the human skin grafts displayed no obvious macroscopic alterations. Microscopic studies of the human skin, however, showed p53-positive keratino-cytes in the epidermis, increased angiogenesis in the dermis of the treated skin, enhanced proliferation of keratinocytes in the basal layer, and an increase of FGF-BP protein and mRNA expression. In contrast, after surgical wounding of human skin grafts or of mouse skin, FGF-BP expression was upregulated within a few hours and returned to control levels after 2 days with wound closure. Enhanced motility of cultured keratinocytes and dermal fibroblasts by FGF-BP supports a role in wound healing. We conclude that adult human skin xenografts can be used to identify early molecular events during malig-nant transformation as well as transient changes during wound healing