Epithelial-stromal interactions in basal cell cancer: the PDGF system

Abstract

A proposed progenitor cell for basal cell carcinoma is a stem cell located in the bulge of the hair follicle. Previous investigations have shown that basal cell carcinoma has a specific stroma requirement for its growth. Likewise the development of a normal hair follicle requires the inductive force of a specialized structure with condensed mesenchyme that eventually forms the dermal hair papilla. Investigations in mouse embryos also strongly indicate that induction/growth of skin structures is dependent on platelet-derived growth factor (PDGF) α-receptor expression in the mesenchyme. We therefore investigated the expression of PDGF A and B chain and PDGF α and β receptors in basal cell carcinoma and in normal skin by immunohistochemistry and in situ hybridization. α and β receptors were found in the specific stroma components of basal cell carcinoma, dermal hair papilla, and sweat glands, but not in the epithelial structures. The A and B chains, on the other hand, were mainly found in basal cell carcinoma cells, in hair matrix, and in sweat gland epithelium. This "appositional" expression of PDGF/PDGF receptor closely resembles that found in epithelial/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. © 1994.