Dermal oncogenicity bioassays of di-sec-butoxyacetophenone and diethoxyacetophenone

Groups of 40 male C3H/HeJ mice were treated 3 times per week for their lifetime on the skin of the back with undiluted di-sec-butoxyacetophenone (DBAP), or with diethoxyacetophenone (DEAP), undiluted and as a 50% dilution in acetone. Approximate doses per application were 22.4 mg for DBAP, and 25.0 or 11.3 mg for DEAP. Two negative control groups received acetone only. Both DBAP and DEAP (undiluted) had weak tumorigenic activity. In the DBAP group, one mouse developed a squamous-cell papilloma, whereas one mouse in the high-dose DEAP group had a squamous-cell carcinoma, both tumors appearing in the treatment area. No skin tumors were observed in the other groups. Both DEAP-treated groups also had substantial incidences of hyperkeratosis, epidermal hyperplasia, and dermatitis. No significant reduction in survival was observed in the test groups. The occurrence of the skin tumors in the DBAP- and DEAP-treated groups is considered to be treatment-related and suggestive of oncogenic potential, because of the extremely low historical control incidence of skin tumors in similar studies.