| Autor: |
Hennings H; Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland 20892., Shores R, Balaschak M, Yuspa SH |
| Jazyk: |
angličtina |
| Zdroj: |
Cancer research [Cancer Res] 1990 Feb 01; Vol. 50 (3), pp. 653-7. |
| Abstrakt: |
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. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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