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Isolation of transforming sequences of two human lung carcinomas: structural and functional analysis of the activated
Abstract:
Human lung tumors PR310 and PR371 maintained in nude mice contain activated c-K-ras oncogenes detectable by the ability of their DNAs to induce the morphological transformation of NIH 3T3 mouse fibroblasts. Using phage libraries constructed with DNA from NIH 3T3 mouse fibroblast transformants, we have isolated human sequences that span greater than 40 kilobase pairs of the c-K-ras oncogene. Based on the conservation of these human sequences in mouse fibroblast transformants, we conclude that the transforming ability of the oncogene activated in these tumors resides within a 43- to 46-kilobase-pair DNA region. No clear differences were observed between the structures of the PR310 and PR371 cloned oncogene sequences. Nucleotide sequence analysis in concert with DNA transfection experiments suggests that the PR371 oncogene has been activated by a single base change in the first exon, which results in the substitution of cysteine for glycine in position 12 of the predicted amino acid sequence. The genetic alteration responsible for the transforming activity of the PR310 oncogene, however, does not reside in the first exon. These results indicate that the activation of the c-K-ras oncogene in human lung cancer can occur by different mutational events.
Insights
Human lung tumors harbor activated c-K-ras oncogenes. Different mutations activate this oncogene in lung cancer, highlighting diverse genetic alterations in tumor development.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Human lung tumors PR310 and PR371 contain activated c-K-ras oncogenes.
- These oncogenes can induce morphological transformation in NIH 3T3 mouse fibroblasts.
Purpose of the Study:
- To isolate and characterize the activated c-K-ras oncogenes from human lung tumors.
- To identify the specific genetic alterations responsible for oncogene activation in lung cancer.
Main Methods:
- Construction of phage libraries using DNA from NIH 3T3 transformants.
- Isolation of human c-K-ras oncogene sequences.
- Nucleotide sequence analysis and DNA transfection experiments.
Main Results:
- Human sequences spanning over 40 kilobase pairs of the c-K-ras oncogene were isolated.
- The transforming ability resides within a 43- to 46-kilobase-pair DNA region.
- PR371 oncogene activation resulted from a single base change in the first exon (Gly12 to Cys).
- PR310 oncogene's genetic alteration was not in the first exon.
Conclusions:
- The c-K-ras oncogene in human lung cancer can be activated by distinct mutational events.
- Different genetic alterations contribute to the activation of c-K-ras in lung tumorigenesis.