Tumorigenicity of nitropolycyclic aromatic hydrocarbons in the neonatal B6C3F1 mouse bioassay and characterization of ras mutations in liver tumors from treated mice

The nitropolycyclic aromatic hydrocarbons (nitro-PAHs) 1-, 2-, and 3-nitrobenzo[a]pyrene, 1- and 3-nitrobenzo[e]pyrene, 2-and 3-nitrofluoranthene, 9-nitrodibenz[a,c]anthracene, and two of the parent PAHs fluoranthene and dibenz[a, c]anthracene were tested for tumorigenicity in the neonatal male B6C3F(1) mouse. 6-Nitrochrysene was used as a positive control. Mice were administered three intraperitoneal injections of test agent (400 nmol total) on 1, 8, and 15 days after birth and evaluated for liver and lung tumors at 12 months of age. 2-Nitrobenzo[a]pyrene and 6-nitrochrysene induced a high incidence of liver tumors (91-100%), while the remaining test compounds did not induce tumors at a rate significantly higher than the solvent control. 6-Nitrochrysene was the only test agent to produce a significant increase in the frequency of lung tumors. K- and H-ras mutations were analyzed in liver tumors of treated mice and mainly occurred at the first base of K-ras codon 13, resulting in GGC --> CGC transversion. Since most of the tested nitro-PAHs are mutagens in vitro, the results of this study indicate that the in vitro mutagenicity of these compounds does not correlate with their tumorigenicity in the neonatal B6C3F(1) mouse bioassay, Also, the results indicate that liver tumors from mice treated with nitro-PAHs possess ms mutations typical of PAHs and their derivatives. (C) 1999 Published by Elsevier Science Ireland Ltd.