title: Sensitivity of subpopulations of mouse skin papillomas to malignant conversion by urethane or 4-nitroquinoline N-oxide.
abstract: Papillomas induced in SENCAR mice by initiation with 7,12-dimethylbenz(a)anthracene and promotion by treatment for 10-12 weeks with 12-O-tetradecanoylphorbol-13-acetate (TPA) convert to malignancy at a low frequency. The rate of malignant conversion can be increased by either (a) promoting with TPA for a shorter duration or (b) treatment of papilloma-bearing mice with certain genotoxic chemicals, such as 4-nitroquinoline N-oxide (4-NQO) or urethane. The spontaneous conversion rate of papillomas promoted by 5 weeks of TPA exposure is severalfold higher than that of papillomas arising later during TPA promotion. Here, we compared the sensitivity to the converting agents 4-NQO and urethane of papillomas promoted by TPA for either 5, 10, or 20 weeks. In the mice promoted for 5 weeks with TPA, the already high spontaneous conversion frequency was increased 2.5 times by 4-NQO. A 2-fold increase was found after 10 weeks of TPA promotion. In contrast, no increase was seen with 4-NQO exposure begun after 20 weeks of TPA promotion. Similar results were found with urethane as converting agent. The sensitivity of the papillomas induced by short-term TPA treatment to induced conversion remains high even after a 16-week period without TPA treatment; when urethane exposure was delayed until week 21 after TPA promotion for weeks 1-5, a 2.4-fold increase in the conversion frequency was observed.
authors.affiliation: Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland 20892.
authors.forename: H
authors.initials: H
authors.lastname: Hennings
authors.forename: R
authors.initials: R
authors.lastname: Shores
authors.forename: M
authors.initials: M
authors.lastname: Balaschak
authors.forename: S H
authors.initials: SH
authors.lastname: Yuspa
mesh_terms: D015112:4-Nitroquinoline-1-oxide; D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D002277:Carcinoma / Q000139:chemically induced*; D003043:Cocarcinogenesis; D051379:Mice; D008815:Mice, Inbred Strains; D010212:Papilloma / Q000139:chemically induced* / Q000473:pathology; D012878:Skin Neoplasms / Q000139:chemically induced* / Q000473:pathology; D016019:Survival Analysis; D013755:Tetradecanoylphorbol Acetate; D013997:Time Factors; D014520:Urethane
chemical_list: D014520:Urethane; D015112:4-Nitroquinoline-1-oxide; D015127:9,10-Dimethyl-1,2-benzanthracene; D013755:Tetradecanoylphorbol Acetate