Malignant Activation of a K-ras Oncogene in Lung Carcinoma but not in Normal Tissue of the Same Patient (original) (raw)
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Activation of a human c-K-ras oncogene
Nucleic Acids Research
The human lung carcinomas PR310 and PR371 contain activated c-K-ras oncogenes. The oncogene of PR371 was found to present a mutation at codon 12 of the first coding exon which substitutes cysteine for glycine in the encoded p21 protein. We report here that the transforming gene of PR310 tumor contains a mutation in the second coding exon. An A-+T transversion at codon 61 results in the incorporation of histidine instead of glutamine in the c-K-ras gene product. By constructing c-K-ras/c-H-ras chimeric genes we show that this point mutation is sufficient to confer transforming potential to ras genes, and that a hybrid ras gene coding for a protein mutant at both codons 12 and 61 is also capable of transforming NIH3T3 cells. The relative transforming potency of p21 proteins encoded by ras genes mutant at codons 12, 61 or both has been analyzed. Our studies also show that the coding exons of ras genes, including the fourth, can be interchanged and the chimeric p21 ras proteins retain their oncogenic ability in normal rodent established cell lines.
Mechanism of activation of an N-ras oncogene of SW-1271 human lung carcinoma cells
Proceedings of the National Academy of Sciences, 1984
An N-ras-related transforming gene was detected in the human lung carcinoma cell line SW-1271 and molecularly cloned. The lesion responsible for its acquisition of transforming activity was localized to a single nucleotide transition from A to G in codon 61 of the predicted protein. This lesion in the second exon results in the substitution of arginine for glutamine at this position. These findings, together with previous studies, indicate that the activation of ras oncogenes in human tumors is most commonly due to point mutations at one of two major "hot spots" in the ras coding sequence.
Proceedings of the National Academy of Sciences, 1997
The gene-mutation-cancer hypothesis holds that mutated cellular protooncogenes, such as point-mutated proto-ras, ''play a dominant part in cancer,'' because they are sufficient to transform transfected mouse cell lines in vitro [Alberts, B., Bray, D., Lewis, J., Raff, M., Roberts, K. & Watson, J. D. (1994) Molecular Biology of the Cell (Garland, New York)].
Proceedings of the National Academy of Sciences, 1984
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 >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 43to 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.
RAS ONCOGENES IN THE DIAGNOSIS OF HUMAN TUMOURS
Abnormal activation of ras oncogenes by specific point mutations has extensively been reported to contribute to human tumorigenesis. Activating point mutations of H-ras, K-ras, N-ras and genes, are restricted to codon 12, 13 or 61 of their DNA sequences. Differential activation of the three ras genes at the transcription level has also been reported in cervical lesions, leukemias, bladder tumours, benign and malignant colorectal tumours, breast and ovarian carcinomas, hepatocellular carcinoma and in myelodysplastic tumours. Overexpression of the ras p21 protein has been detected both at the RNA and the protein level in several types of human cancers such as the squamous cell carcinomas of the head and neck, nasopharyngeal carcinomas or in bone marrow smears of children with acute leukemia. The discovery of new prognostic indicators is considered extremely important and detection of alterations in ras genes could serve as a crucial molecular marker for the early detection of human malignancies or alternatively for the discrimination between chronic non-malignant conditions and cancer. The research on ras genes in relation to human malignancies and its potential clinical significance in screening tests for early detection and accurate prognosis is reviewed and its potential application in future therapeutic treatment of human cancer is discussed.
Activation of a human c-K- ras oncogeoe
Nucleic Acids Research, 1984
The human lung carcinomas PR310 and PR371 contain activated c-K-ras oncogenes. The oncogene of PR371 was found to present a mutation at codon 12 of the first coding exon which substitutes cysteine for glycine in the encoded p21 protein. We report here that the transforming gene of PR310 tumor contains a mutation in the second coding exon. An A-+T transversion at codon 61 results in the incorporation of histidine instead of glutamine in the c-K-ras gene product. By constructing c-K-ras/c-H-ras chimeric genes we show that this point mutation is sufficient to confer transforming potential to ras genes, and that a hybrid ras gene coding for a protein mutant at both codons 12 and 61 is also capable of transforming NIH3T3 cells. The relative transforming potency of p21 proteins encoded by ras genes mutant at codons 12, 61 or both has been analyzed. Our studies also show that the coding exons of ras genes, including the fourth, can be interchanged and the chimeric p21 ras proteins retain their oncogenic ability in normal rodent established cell lines.
The role of the RAS oncogene in the formation of tumours
Journal of Cell Science, 1988
A c-Ha-ras 1 oncogene, cloned from the EJ human bladder carcinoma cell line, was inserted into a shuttle vector carrying the selectable marker gene gpt that encodes the enzyme xanthine-guanine phosphoribosyl transferase. This construct, pSV2gptEJ, was transfected into NIH 3T3 cells by the calcium phosphate precipitation method and cells that had incorporated the plasmid were selected by growth in the presence of mycophenolic acid to which gpt confers resistance. A number of transfectant clones were tested for tumorigenicity by inoculation into nude mice. The take incidence was variable and the tumours arose only after a prolonged latent period. Many inocula produced no tumours. These results were consistent with the view that the tumours arose by selective overgrowth of minority cell populations. Cell lines were derived by explantation of these tumours and were back-selected in 2-thioxanthine, a cytotoxic analogue of the xanthine-guanine phosphoribosyl transferase substrate. Five cl...