Recent advances in epidermal biology: relevance to epidermal malignancies

Recent advances in the biology of the epidermis increase our understanding of skin cancer. Epidermal tissue culture demonstrates that cells from epidermal malignancies retain their malignant characteristics. Some epidermal tumors contain a low molecular weight keratin as a major structural protein; a low molecular weight keratin is a characteristic of fetal epidermis as well. Certain epidermal cell-surface antigens, such as the pemphigus antigen, may be absent in skin cancers. A population of long-lived skin cells may be the site for genetic alterations that eventually produces skin cancers. A population of basal "dark" cells is increased after treatment with tumor promoting agents such as phorbol esters. Two-stage (initiation, promotion) epidermal carcinogenesis can now be studied in tissue culture. Several components of the complex multilayered basement membrane zone are produced by epidermal cells. Malignancies of epidermal cells may extend beyond the basement membrane zone by disordered synthesis of the zone or by producing enzymes including collagenases that alter the zone.