Abstract 3458: Benzo[a]pyrene (BP)-induced DNA damage is elevated in mice lacking Xeroderma pigmentosum complementation group A (Xpa) and heterozygous for the tumor suppressor gene p53

Abstract

Abstract In developing countries, esophageal cancer is the third most common cancer in men. We have employed a mouse model of esophageal cancer using DNA repair deficient mice. Unlike their wild type counterparts, C57BL/6J mice lacking Xpa and heterozygous for p53 [Xpa(−/−) p53(+/−)] have previously been shown to develop forestomach and esophageal tumors when fed BP (Hoogervorst et al., Carcinogenesis, 2003). Two methodologies were employed to examine BP-induced steady-state levels of DNA damage in esophagi of male mice fed 0 or 100 ppm BP for 4 weeks. HPLC, in conjunction with tandem mass spectrometry (HPLC-MS/MS), was used to measure 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydro-benzo[a]pyrene (BPdG) and a chemiluminiscence immunoassay (CIA), using antiserum elicited against r7,t8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE)-modified DNA was used to evaluate BP-DNA adducts. In the esophagi of Xpa(−/−) p53(+/−) mice, there were 38.7 ± 4.8 BPdG adducts/108 nucleotides (mean ± SE, n=5), as measured by HPLC-MS/MS, while in the wild type mice there were 28.0 ± 1.8 BPdG adducts/108 nucleotides (mean ± SE, n=5). Furthermore, complete loss of p53 resulted in the greatest accumulation of BPdG adducts, with 58.1 ± 8.6 BPdG adducts/108 nucleotides (n=5) in Xpa(−/−) p53(−/−) mice (p<0.05 vs. wild type mice). Esophageal BP-DNA adduct values, as measured by CIA, were 23.3 ± 1.7 adducts/108 nucleotides (n=3) in the Xpa(−/−) p53(+/−) mice, compared to 14.6 ± 3.0 adducts/108 nucleotides (n=3) in the wild type mice. Since similar adduct levels were determined using both HPLC-MS/MS and CIA, this indicates that BPdG is the major adduct resulting from BP in mouse esophagus. The higher levels of DNA damage in DNA repair-deficient p53-deficient mice, compared to their wild type counterparts, may contribute to the enhanced susceptibility of these mice to esophageal tumor induction by BP. Currently we are examining the role of chlorophyllin, a chemopreventive agent, in reducing BP-induced DNA damage levels and tumor formation in this model. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3458.