Inhibition of Ultraviolet Radiation-Induced Skin Tumors in Hairless Mice by Topical Application of the Sunscreen 2-Ethyl Hexyl-P-Methoxycinnamate

Abstract

This study used simulated solar ultraviolet radiation (UVR) exposure of hairless mice to produce skin tumors and 12-o-tetradecanoyl-phorbol-13-acetate (TPA) to increase the likelihood of tumor expression. We evaluated the protection afforded by several concentrations of a sunscreen ingredient (by measuring reduction of “promotable” effects initiated by UVR); the data show that 2-ethyl hexyl-p-methoxycinnamate (2-EHMC) provided protection against photocarcinogenesis (the level of protection increasing with concentration of sunscreen). A second sample of 2-EHMC (drawn from a different production batch) also suppressed photocarcinogenesis but less effectively than the first sample. The study was also useful for evaluating whether the test agents could act as initiators in the two-stage process of tumorigenesis. The data show that repeated applications of TPA did not promote tumor growth in skin pretreated with any sunscreen ingredients alone (i.e., either sample of 2-EHMC in the absence of UVR).