Toxicologic evaluation of flavor ingredients added to cigarette tobacco: skin painting bioassay of cigarette smoke condensate in SENCAR mice

Four comparative two-stage SENCAR mouse skin painting bioassays were conduc ted with cigarette smoke condensate (CSC) preparations to evaluate the effe ct of common American cigarette flavoring ingredients on tumor promotion. E ach independent study employed a unique flavoring combination applied to to bacco at exaggerated levels, and in total resulted in an evaluation of 150 ingredients. Groups of 30-50 female SENCAR mice each were initiated topical ly with 50 mu g of 7,12-dimethylbenz(a)anthracene (DMBA), and promoted thri ce weekly for 26 weeks with either 10 or 20 mg of CSC from test cigarettes containing ingredient mixtures. For comparison, separate groups of mice rec eived concurrent treatment with CSC from reference cigarettes prepared with out added ingredients. Negative and positive controls were treated with ace tone or 12-0-tetradecanoyl-phorbol-13-acetate (TPA) as a promoter, respecti vely. CSC-only groups served as promotion controls. Tumors developed in >80 % of the TPA-treated mice by study week 11, with a <3% background tumor for mation in the acetone treated controls at termination. Tumor incidence in C SC-only promotion control groups was <20%, with no apparent difference betw een reference and test CSC groups. Approximately 70% of the DMBA-initiated mice promoted with 20 mg CSC developed tumors. Tumors first appeared around week 9, with about five tumors/tumor bearing animal. Tumor incidence, late ncy and multiplicity were CSC dose related, with a lower tumor incidence (a pproximately 50%), longer latency (12 weeks), and reduced tumor burden (fou r tumors/tumor bearing animal) at the 10 mg CSC dose level. While tumor inc idence, latency and multiplicity data occasionally differed between test an d comparative reference CSC groups, all effects appeared to be within norma l variation for the model system. Furthermore, none of the changes appeared to be substantial enough to conclude that the tumor promotion capacity of CSC obtained from cigarettes containing tobacco with ingredients was discer nibly different from the CSC obtained from reference cigarettes containing tobacco processed without ingredients. (C) 1999 Elsevier Science Ireland Lt d. All rights reserved.