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EFFECT OF IMMUNOSUPPRESSIVE AGENTS AND SUNSCREENS ON UV CARCINOGENESIS IN THE HAIRLESS MOUSE
Author(s) -
Reeve Vivienne E,
Greenoak GE,
Gallagher CH,
Canfield PJ,
Wilkinson FJ
Publication year - 1985
Publication title -
australian journal of experimental biology and medical science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.999
H-Index - 104
eISSN - 1440-1711
pISSN - 0004-945X
DOI - 10.1038/icb.1985.69
Subject(s) - hairless , azathioprine , cyclophosphamide , carcinogenesis , skin cancer , pharmacology , chemistry , cancer research , ratón , immunology , biology , dermatology , medicine , cancer , chemotherapy , pathology , biochemistry , disease
Summary The effect of two immunosuppressive agents, azathioprine and cyclophosphamide, with and without UVB sunscreen protection on UV‐induced skin carcinogenesis was studied in the albino hairless mouse. In a daily treatment regime spanning 9 weeks, groups of mice were immunosuppressed with either drug, and were exposed to minimally erythemal doses of a light source simulating the UV portion of the solar spectrum. The accumulated UV exposure alone induced skin tumours in 77% of mice. Azathioprine, but not cyclophosphamide, significantly enhanced the incidence of UV tumorigenesis. Photoprotection by topical application of one of two commonly used UVB sunscreens, 2‐ethyl‐hexyl‐p‐methoxycinnamate (2‐EHMC) or octyl‐N‐dimethyl‐p‐aminobenzoate (o‐PABA), reduced the UV tumour incidence to zero in immunologically normal mice and to 8‐15% in immunosuppressed mice. Unexpressed latent tumour initiations were revealed in all sunscreen‐protected groups by the subsequent application of a tumour promoter, croton oil. In immunologically normal mice 2‐EHMC had allowed initiations in 39% of UV‐irradiated mice, and o‐PABA in 16‐5%. However, in UV‐irradiated mice immunosuppressed with azathioprine there had been initiations in 78% of mice protected with 2‐EHMC and 65% of mice protected with o‐PABA. Photoprotected mice immunosuppressed with cyclophosphamide did not show the same increase in UV‐initiations (22% with 2‐EHMC, 23% with o‐PABA). These results provide evidence that azathioprine increases the susceptibility of the skin to UV carcinogenesis. However, UVB sunscreens afford effective protection from overt tumour expression in the absence of a tumour promoter.