Increased susceptibility of poly(ADP-ribose) polymerase-1 knockout mice tonitrosamine carcinogenicity

The involvement of poly(ADP-ribose) polymerase-1 (Parp-1), one of the poly( ADP-ribose) polymerase family proteins, in genomic stability, DNA repair an d cell death triggered by DNA damage has been well documented. However, the potential role of Parp-1 in carcinogenesis has not been well evaluated. In this study the carcinogenic activity of N-nitrosobis(2-hydroxypropyl)amine (BHP) was studied in Parp-1(-/-) mice, generated by disrupting Parp-1 gene exon 1, Parp-1(-/-) and Parp-1(+/+) male mice received 0, 250 and 500 p.p. m. BHP in their drinking water for 20 weeks and were then killed. The perce ntage of animals bearing hemangiomas and hemangiosarcomas in the liver and numbers of tumors per mouse were markedly higher in the Parp-1(-/-) groups given 250 or 500 p.p.m. BHP than in their Parp-1(+/+) counterparts. Hemangi osarcomas developed only in Parp-1(-/-) mice. In the lung the numbers of ad enomas per mouse were increased in Parp-1(-/-) mice given BHP at 250 and 50 0 p.p.m. (P < 0.01) compared with the Parp-1(+/+) case. The results show th at susceptibility to BHP is significantly elevated in Parp-1(-/-) mice, thu s providing direct evidence that Parp-1 is relevant to carcinogenesis.