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A human oncogene of the RAS superfamily unmasked by expression cDNA cloning
1Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Abstract:
As an approach to identify human oncogenes, we generated an expression cDNA library from an ovarian carcinoma line. A potent transforming gene was detected by transfection analysis and identified as TC21, a recently cloned member of the RAS gene superfamily. A single point mutation substituting glutamine for leucine at position 72 was shown to be responsible for activation of transforming properties. While the cDNA clone possessed high transforming activity, the ovarian tumor genomic DNA, which contained the mutated TC21 allele, failed to induce transformed foci. Thus, expression cDNA cloning made it possible to identify and isolate a human oncogene that has evaded detection by conventional approaches.
Insights
Researchers identified TC21, a human oncogene from the RAS gene superfamily, using expression cDNA cloning. A specific mutation activated its transforming properties, enabling its discovery in ovarian cancer. This method identified an oncogene missed by conventional techniques.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Identifying human oncogenes is crucial for understanding cancer development.
- Conventional methods have limitations in detecting all oncogenes.
- Ovarian carcinoma presents a complex genetic landscape.
Purpose of the Study:
- To identify novel human oncogenes involved in ovarian carcinoma.
- To characterize the transforming properties of identified genes.
- To evaluate the efficacy of expression cDNA cloning for oncogene discovery.
Main Methods:
- Generation of an expression cDNA library from an ovarian carcinoma cell line.
- Transfection analysis to detect potent transforming genes.
- DNA sequencing to identify point mutations responsible for oncogenic activity.
Main Results:
- A potent transforming gene, TC21 (a RAS superfamily member), was identified.
- A single point mutation (L72Q) was responsible for TC21's transforming activity.
- The expression cDNA clone showed high transforming activity, but the tumor genomic DNA did not, indicating the importance of expression.
Conclusions:
- Expression cDNA cloning is a powerful approach for identifying oncogenes.
- TC21 is a newly identified human oncogene activated by a specific mutation.
- This method successfully isolated a human oncogene that evaded conventional detection methods.