Nuclear factor-erythroid 2 (NF-E2)-related factor 2 (Nrf2), a transcription factor that regulates inducible expression of detoxifying enzymes, is critical in preventing N-nitrosobutyl(4-hydroxybutyl)amine (BBN)-induced urinary bladder carcinogenesis. To explore whether Nrf2 and the tumor suppressor p53 cooperatively act in tumor prevention, we investigated the susceptibility of Nrf2-/-::p53+/- mice to BBN-induced urinary bladder carcinogenesis. The incidence of BBN-induced urinary bladder carcinoma was 63.0% in Nrf2-/- mice (P = 0.115), 75.8% in p53+/- mice (P < 0.01) and 89.6% in Nrf2-/-::p53+/- mice (P < 0.01) compared with 37.9% in wild-type. Higher incidence of carcinoma was observed in Nrf2-/-::p53+/- mice when compared with either Nrf2-/- (P < 0.01) or p53+/- mice (P = 0.382). Similarly, muscular invasive carcinoma incidence was higher in Nrf2-/-::p53+/- mice (62.0%) than either wild-type (6.9%, P < 0.01), p53+/- (38.0%, P = 0.110) or Nrf2-/- mice (3.7%, P < 0.01). Furthermore, urinary concentrations of N-nitrosobutyl(3-carboxypropyl)amine, a proximate carcinogen of BBN, were only increased when Nrf2 but not p53 was disrupted. These results demonstrate that tumor susceptibility is synergistically exacerbated in Nrf2-/-::p53+/- mice due to poor detoxification and accelerated proliferation in comparison with either single mutant alone. BBN administration increased p53-mediated expression of p21, Mdm2 and Bax, and the inducible expression of p21 was significantly enhanced in Nrf2-/- mice. Conversely, modest increases in NAD(P)H dehydrogenase, quinone 1 (NQO1) and uridine diphosphate (UDP) glucuronosyltransferase 1A6 (UGT1A6) expression were observed in p53+/- compared with those of wild-type mice after BBN exposure. These results thus reveal potential interactions between p53 and Nrf2 and their gene batteries, and indicate that both factors cooperatively contribute to tumor prevention.
ASJC Scopus subject areas
- Cancer Research