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Resistance of human cells to tumorigenesis induced by cloned transforming genes
Abstract:
The transformation of human cells was examined by transfection of cloned oncogenic DNAs derived from the tumor virus simian virus 40 and from the human bladder carcinoma cell line EJ into diploid fibroblasts derived from foreskin (FS-2 cells). The simian virus 40 DNA was found to induce a morphologically transformed phenotype, leading to easily detectable focus formation. Tumor antigen was produced, but the transformed cells were not tumorigenic in the nude mouse. The EJ gene, a mutant form of the cellular c-Ha-ras gene, actively transforms NIH/3T3 mouse cells and CHEF/18 hamster cells but is inactive in FS-2 cells. Morphological transformation, focus formation, and tumorigenicity in nude mice were not induced when EJ DNA was transfected into FS-2 cells by using the selectable vector pSVgptEJ. The intactness of the transfected EJ DNA was established by restriction fragment analysis. This result raises the question of what role, if any, the mutated gene derived from the EJ cells played in the origin of the EJ bladder carcinoma.
Insights
Simian virus 40 DNA transformed human fibroblasts, but the EJ gene did not. This suggests the mutated EJ gene may not play a role in bladder carcinoma origin.
Area of Science:
- Oncogenic DNA transfection
- Cellular transformation studies
- Cancer genetics
Background:
- Investigating the genetic basis of human bladder carcinoma.
- Understanding the role of oncogenes in cellular transformation.
- Utilizing human fibroblasts (FS-2 cells) as a model system.
Purpose of the Study:
- To examine the transforming potential of Simian virus 40 (SV40) DNA and the EJ gene in human fibroblasts.
- To determine if the EJ gene, a mutated c-Ha-ras, contributes to cellular transformation and tumorigenicity in human cells.
- To elucidate the role of specific oncogenic DNA in the development of human bladder carcinoma.
Main Methods:
- Transfection of cloned oncogenic DNAs (SV40 and EJ gene) into human foreskin fibroblasts (FS-2 cells).
- Assessment of morphological transformation, focus formation, and tumor antigen production.
- Evaluation of tumorigenicity in nude mice following DNA transfection.
- Confirmation of transfected EJ DNA integrity using restriction fragment analysis.
Main Results:
- SV40 DNA induced morphological transformation and tumor antigen production in FS-2 cells, but these cells were not tumorigenic.
- The EJ gene, known to transform other cell types, failed to induce transformation or tumorigenicity in FS-2 cells.
- Transfection of the EJ gene into FS-2 cells using a selectable vector did not result in morphological transformation, focus formation, or tumorigenicity.
- Restriction fragment analysis confirmed the integrity of the transfected EJ DNA.
Conclusions:
- SV40 DNA possesses transforming capabilities in human fibroblasts.
- The mutated EJ gene, despite transforming other cell lines, is inactive in human foreskin fibroblasts (FS-2 cells).
- The findings question the direct role of the mutated EJ gene in the origin of the EJ bladder carcinoma, suggesting other factors may be involved.