Fluocinolone acetonide (FA) is one of the most potent synthetic glucocorticoids and is known to possess an anti-tumor promoting activity. An attempt was made to evaluate this activity by estimating tumor promoting activity. Unexpectedly, when 10 micrograms of FA was applied alone or after a single application of a subcarcinogenic dose of 3-methylcholanthrene to mouse skin, results suggested that FA itself may be a tumor promoter or a complete carcinogen. Other glucocorticoids tested, e.g. dexamethasone, hydrocortisone and prednisolone, also revealed similar effects but were less potent than FA. To verify the possibility that glucocorticoid is a complete carcinogen or a tumor promoter, a tumor incidence experiment was performed for 24 weeks. As a result it was found that FA possesses a tumor promoting activity at some dose levels but no tumor initiating activity.

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