The effects of anti-inflammatory agents on skin tumor initiation and aryl hydrocarbon hydroxylase.

The effects of various clinically used anti-inflammatory agents on mouse skin tumorigenesis and aryl hydrocarbon hydroxylase (AHH) were investigated. Oxyphenbutazone, a nonsteroidal anti-inflammatory agent, inhibited 3-methylcholanthrene (MC) tumor initiation but was less effective than the steroidal anti-inflammatory agent, dexamethasone. Oxyphenbutazone was not found to induce AHH activity in mouse epidermis, whereas indomethacin and Seclazone had a slight inducing effect. When these agents were added directly to the in vitro AHH assay, they did not inhibit AHH activity. However, additional experiments have shown a decreased epidermally mediated covalent binding of MC to DNA in vitro when the epidermal homogenates were isolated from mice pretreated with either dexamethasone or oxyphenbutazone and MC at 3 or 12 hr before killing.