Parp-1 deficiency does not enhance liver carcinogenesis induced by 2-amino-3-methylimidazo[4,5-f]quinoline in mice

The susceptibility of poly(ADP-ribose) polymerase-1 (Parp-1) knockout mice to 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)-induced liver carcinogenesis was analyzed. Twelve-week-old male Parp-1+/+, Parp-1+/− and Parp-1−/− mice of the C57BL/6 congenic strain were fed a diet containing IQ at a concentration of 300 ppm or a control diet for 60 weeks. Hepatocellular carcinomas were observed only in 1/19, 2/18 and 1/17 of the Parp-1−/−, Parp-1+/− and Parp-1+/+ mice, respectively. Parp-1 deficiency did not affect the susceptibility of mice to carcinogenicity of IQ, which produces bulky DNA adducts that are repaired mainly through the nucleotide excision repair pathway. This result is in sharp contrast to the increased susceptibility of Parp-1−/− mice to carcinogenesis induced by alkylating agents that produce DNA damage repaired mainly through base excision repair and DNA strand break repair pathways.