Growth Characteristics and Differentiation of Basal Cell Carcinoma In Vitro–Immunohistochemical, Gel Electrophoretic, and Ultrastructural Analysis

Abstract

Cell cultures were established from 48 solid basal cell carcinomas (BCC) and from the normal epidermis of the same patients. The growth characteristics and differentiation of BCC cells in vitro were compared with normal keratinocytes (nKC) by using immunohistochemistry, two-dimensional gel electrophoresis including immunoblots, transmission electron microscopy, and soft agar suspension culture. After isolation of the tumor tissue under a stereodissection microscope, explants were cultured on feeder layers of mitomycin-treated 3T3 cells. After 3-5 d, 73% of all explants of BCC could be successfully cultured showing spindle-shaped outgrowing cells. Compared to nKC, cultured BCC cells had a lower growth rate and showed a wider intercellular polymorphism regarding size and shape. Their labeling pattern with a wide panel of monoclonal antibodies showed significant differences from that of nKC. In particular, only weak reactions for various cytokeratins, filaggrin and vimentin depending on the BCC cell type (small, middle, large) were found. Two-dimensional gel electrophoresis revealed expression of keratins 5, 6, 14, 16, and 17 in BCC cells and of K 5, 6, 13, 14, 16, 17, and 19 in nKC. These findings were confirmed by immunoblot. On the ultrastructural level, only a few desmosomes and a lower degree of keratinization markers were detected in BCC cells; finally, when cultured in soft agar BCC cells formed colonies whereas nKC did not. Our findings indicate that cultured BCC cells may preserve in vitro some in vivo characteristics and maintain a growth and differentiation pattern that differs from cultured nKC. The culture model presented here provides further insights into the cytogenetic and histogenetic characteristics of BCC.