EPITHELIAL-STROMAL INTERACTIONS IN BASAL-CELL CANCER - THE PDGF SYSTEM

A proposed progenitor cell for basal cell carcinoma is a stem cell loc ated in the bulge of the hair follicle. Previous investigations have s hown that basal cell carcinoma has a specific stroma requirement for i ts growth. Likewise the development of a normal hair follicle requires the inductive force of a specialized structure with condensed mesench yme that eventually forms the dermal hair papilla. Investigations in m ouse embryos also strongly indicate that induction/growth of skin stru ctures is dependent on platelet-derived growth factor (PDGF) alpha-rec eptor expression in the mesenchyme. We therefore investigated the expr ession of PDGF A and B chain and PDGF alpha and beta receptors in basa l cell carcinoma and in normal skin by immunohistochemistry and in sit u hybridization. Alpha and beta receptors were found in the specific s troma components of basal cell carcinoma, dermal hair papilla, and swe at glands, but not in the epithelial structures. The A and B chains, o n the other hand, were mainly found in basal cell carcinoma cells, in hair matrix, and in sweat gland epithelium. This ''appositional'' expr ession of PDGF/PDGF receptor closely resembles that found in epithelia l/mesenchymal structures during normal development. The findings also suggest that PDGF receptor expression is one of the characteristics of the specific stroma that is necessary for basal cell carcinoma growth .