ABSTRACT
Skin carcinogenesis in mice can be accomplished using either multistage or com plete protocols (1,2). Complete carcinogenesis experimental protocols involve the administration of a single dose or repeated applications of smaller doses of a carcin ogen to an experimental animal. In the mouse skin tumorigenesis system, multiple papillomas and carcinomas can be produced on the backs of mice following a single application of as little as 600 to 800 nmol of a pure polycyclic aromatic hydrocarbon (PAH) such as 7,12-dimethylbenz[a]anthracene (DMBA) (3,4). The induction of mouse skin tumors can also be accomplished by using a multistage model that involves the processes defined operationally and mechanistically as initiation and promotion (1,2,5). Initiation is generally accomplished by topical application of a single subcarcinogenic dose of a skin carcinogen, such as DMBA. An initiating dose of a carcinogen, per se, will not lead to the development of visible tumors. Visible tumors will result only following prolonged and repeated topical applica tions of a tumor promoter, such as croton oil or its most active constituent, 12-0tetradecanoylphorbol-13-acetate (TPA), to the initiated skin (1,2). It is generally assumed that both the initiating and promoting components are present during com plete carcinogenesis experimental protocols.
