TUMOR MULTIPLICITY, DNA-ADDUCTS AND K-RAS MUTATION PATTERN OF 5-METHYLCHRYSENE IN STRAIN A J MOUSE LUNG/

This study was undertaken to evaluate the carcinogenic potential of 5- methylchrysene (5-MeC) in strain A/J mouse lung and to correlate the 5 -MeC-DNA adduct profile in lung tissue with the mutation spectrum in t he K-ras gene of lung tumors. Strain A/J mice received a single i.p. i njection of 5-MeC at doses of 10, 50, 100 and 200 mg/kg and after 24, 48 and 72 h their lungs were collected for DNA adduct analysis. Eight months later, lungs from the remaining mice were harvested and the lun g tumors counted and collected for subsequent mutational analysis of t he K-ras gene. 5-MeC was found to be a potent lung carcinogen in strai n A/J mice, inducing more than 100 tumors/mouse at a concentration of 200 mg/kg. Six 5-MeC-DNA adducts were observed; one adduct comigrated with the standard Nz-deoxyguanosine adduct of 5-MeC-diol-epoxide I [1R ,2S,3S-trihydroxy-4R-(N-2-deoxyguanosyl-3' -phosphate)-1,2,3,4-tetrahy dro-5-methyl-chrysene], derived from the bay-region diol-epoxide of 5- MeC. DNAs isolated from 5-MeC-induced lung tumors were evaluated for a ctivating mutations in the K-ras gene by polymerase chain reaction-sin gle strand conformation polymorphism and direct DNA sequencing analysi s. Mutations were detected in 44 of 49 (90%) 5-MeC-induced tumors and the mutations were GGT-->TGT (50%), GGT-->GTT (23%) and GGT-->CGT (27% ) in codon 12 of the gene. These results suggest that the N-2-deoxygua nosine adduct of 5-MeC-diol-epoxide I may be one of the promutagenic a dducts of 5-MeC in strain A/J mouse lung.