Prevention of photocarcinogenesis and UV‐induced immunosuppression in mice by topical tannic acid

Abstract

Topical application of tannic acid, a phenolic antioxidant derived from plants, was found to inhibit the cutaneous carcinogenesis and the immunosuppression induced by ultraviolet B (UVB) irradiation with no visible toxicity. BALB/cAnNTacfBR mice were treated with 200 μg of tannic acid three times weekly for two weeks before UV treatments began and throughout the experiment. UVB irradiation consisted of five 30‐minute exposures per week to banks of six FS40 Westinghouse sunlamps. In the photocarcinogenesis study, mice received a total dose of approximately 1.09 × 10⁶ J/m². Skin cancer incidence in UV‐irradiated mice was 75% at 26 weeks after the first UV exposure; tannic acid reduced this to 42%. Immunosuppression induced by UVB irradiation normally prevents the host from rejecting antigenic syngeneic UV‐induced tumors. Immunosuppression in these experiments was measured by a passive transfer assay. Tumor challenges grew to an average of 88 ± 20, 36 ± 11, and 20 + 8 mm² in naive recipients of splenocytes from UVB‐irradiated mice, nonirradiated control mice, and UVB‐irradiated mice treated with tannic acid, respectively. Thus topical tannic acid treatment prevented the transfer of enhanced tumor susceptibility with splenocytes from UVB‐irradiated mice.