Cigarette smoke treatment induces molecular changes in p53, mdm2 and p19ARF proteins in C57BL/6 mouse lungs in vivo

R Serpi, MSc a, M Turpeinen, MB a, K Vähäkangas, MD a, b

a Department of Pharmacology and Toxicology, University of Oulu, Oulu, Finland b Department of Pharmacology and Toxicology, University of Kuopio, Kuopio, Finland.

AIM: Cigarette smoke is the main cause of lung cancer. Benzo(a)pyrene in cigarette smoke is activated within the body and binds to DNA. BPDE-DNA adducts induce the p53 protein. Mdm2 protein that binds to p53 is essential in the degradation of p53. We studied whether cigarette smoke induces detectable effects on p53 and related proteins in vivo. METHODS: Male C57BL/6 mice were treated for 31 days in a smoking chamber with smoke from commercial cigarettes containing 12 mg tar and 0.9 mg nicotine per cigarette. For BPDE-DNA, DNA from the tissues was isolated and the adducts measured by synchronous fluorescence spectrophotometry. p53, mdm2 and p19ARF proteins were studied by immunoblotting using CM5, H-221 and PC435 antibodies, respectively. RESULTS: Of lungs, skin and liver, detectable effects were found only in the lungs. Exposure of mice to cigarette smoke in vivo induced the formation of BPDE-DNA adducts, and an increase of p53 and a decrease of mdm2 proteins. There were also implications that cigarette smoke causes an induction of p19ARF. CONCLUSIONS: Results support the tumor suppressor function of p53 in cigarette smoke-induced lung cancer and the role of mdm2 protein in the induction of p53 protein in lung tissue. It is possible that BPDE-DNA adducts induce the p53 protein by causing a decrease in mdm2 protein through an induction of p19ARF.

KEY WORDS: Key words p53, p19^(ARF), smoke exposure, BPDE-DNA adducts.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Carcinogenesis.