K-ras gene mutation in early ductal lesions induced in a rapid production model for pancreatic carcinomas in Syrian hamsters.

The presence of K-ras gene mutation was examined in experimentally induced preneoplastic pancreatic ductal lesions. Syrian hamsters received 70 mg/kg of N-nitrosobis(2-oxopropyl)amine (BOP) followed by repeated exposure to an augmentation pressure regimen consisting of choline-deficient diet combined with DL-ethionine and L-methionine and administration of 20 mg/kg BOP. After two augmentation pressure cycles, pancreatic ductal cell hyperplasias appeared and after three cycles, atypical hyperplasias of pancreatic ductal cells and intraductal carcinomas developed. K-ras mutations were detected by single-strand conformation polymorphism analysis of polymerase chain reaction products and nucleotide sequencing. The results showed that K-ras mutation had occurred in one of 9 simple hyperplasias of pancreatic ductal epithelium, in 5 of 9 atypical hyperplasias, and in 4 of 8 intraductal carcinomas. The findings thus suggested that K-ras is activated in association with very early stage malignant transformation of pancreatic ductal cells in hamsters.