EFFECTS OF K-RAS GENE-MUTATIONS IN THE DEVELOPMENT OF LUNG LESIONS INDUCED BY -(N-METHYL-N-NITROSAMINO)-1-(3-PYRIDYL)-1-BUTANONE IN A J MICE/

The relationship between the development of peripheral lung lesions in duced by tobacco-specific 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl) (NN K) and K-ras gene mutation in A/J mice, and the correlations between h istological alterations and the course of lung lesion development afte r NNK treatment and K-ras gene mutation were investigated. The acquisi tion of a selective growth advantage by the lung lesions with mutation s was also examined using immunohistochemical labeling with bromodeoxy uridine. Thirty female 5 weeks old A/J mice were each injected intrape ritoneally with a single dose of NNK (100 mg/kg body weight) and subdi vided into 6 groups according to the time after NNK treatment. The lun g lesions were characterized histologically as alveolar/bronchiolar hy perplasia, adenoma and adenocarcinoma, and point mutations In codons 1 2 and 61 of the K-ras gene were detected by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) and dideoxy se quencing methods. K-ras gene mutations were identified in 7 (58.3%) of 12 hyperplasias, 42 (75.0%) of 56 adenomas and 3 (75.0%) of 4 adenoca rcinomas. The most frequent K-ras gene mutation was a G-to-A transitio n at the second base of codon 12 and this accounted for 86.5% of all t he mutations detected. Neither the frequency of activation of this gen e nor the specific mutation was affected by the time after NNK treatme nt and there was no positive correlation between the proliferative act ivity of lung lesions and the presence of K-ras gene mutations. Thus, K-ras gene mutation is closely associated with the development of NNK- induced peripheral lung lesions in A/J mice, but it plays no role in t he selective growth advantage of these lesions.