Corticosteroid prevention of carcinogenesis in benzo[a]pyrene or ultraviolet irradiation-treated Syrian hamster cells in vitro.

Cortisol and dexamethasone, at 10(-9)--10(-11) M, inhibit benzo[a]pyrene and ultraviolet irradiation-induced morphological transformation of hamster embryo fibroblasts without inhibiting cell proliferation in a cell culture model of carcinogenesis. Inhibition varies directly with steroid concentration and is complete at equimolar doses for these glucocorticosteroids possessing a 30-fold difference in anti-inflammatory activity. Corticosteroids are known to affect enzymes metabolizing carcinogenic polycyclic aromatic hydrocarbons (PCH) and to inhibit complete PCH and phorbol ester promotion of PCH tumorigenesis. The pleotropic anti-carcinogenic action of corticosteroids is further demonstrated by the prevention of transformation induced by ultraviolet irradiation, a carcinogen not requiring metabolic activation.