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A Swiss 3T3 variant cell line resistant to the effects of tumor promoters cannot be transformed by src
M Nori1, L K Shawver, M J Weber
1Department of Microbiology, University of Virginia School of Medicine, Charlottesville 22908.
Abstract:
To study the relationship between oncogenesis by v-src and normal cellular signalling pathways, we determined the effects of v-src on 3T3-TNR9 cells, a Swiss 3T3 variant which does not respond mitogenically to tumor promoters such as 12-O-tetradecanoyl-phorbol-13-acetate (TPA). We found that src was unable to transform these variant cells, whether the oncogene was introduced by infection with a murine retrovirus vector or by transfection with plasmid DNA. 3T3-TNR9 cells were not inherently resistant to transformation, since infection with similar recombinant retroviruses containing either v-ras or v-abl did induce transformation. Further analysis of Swiss 3T3 and 3T3-TNR9 cell populations infected with the v-src-containing retrovirus revealed that although the amount of v-src DNA in each was approximately the same, the level of the v-src message and protein and the overall level of phosphotyrosine expressed in the infected variants was much less than in infected parental cells. Cotransfection experiments using separate v-src and neo plasmids revealed a decrease in the number of G418-resistant colonies when transfections of TNR9 cells occurred in the presence of the src-containing plasmid, suggesting a growth inhibitory effect of v-src on 3T3-TNR9 cells, as has also been found for TPA itself. Since v-src cannot transform this variant cell line, which does not respond mitogenically to the protein kinase C agonist TPA, we suggest that src makes use of the protein kinase C pathway as part of its signalling activities.
Insights
The oncogene v-src could not transform 3T3-TNR9 cells, which lack response to 12-O-tetradecanoyl-phorbol-13-acetate (TPA). This suggests v-src utilizes the protein kinase C pathway for its signalling activities in cell transformation.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- The oncogene v-src plays a crucial role in cell transformation and oncogenesis.
- Understanding the signalling pathways utilized by v-src is essential for deciphering its oncogenic potential.
- Swiss 3T3 cells and their variants, like 3T3-TNR9, are widely used models for studying cellular responses to growth factors and tumor promoters.
Purpose of the Study:
- To investigate the relationship between v-src-mediated oncogenesis and normal cellular signalling pathways.
- To determine the effects of v-src on 3T3-TNR9 cells, a variant unresponsive to mitogenic stimuli like 12-O-tetradecanoyl-phorbol-13-acetate (TPA).
Main Methods:
- Introduction of v-src oncogene into 3T3-TNR9 cells via retroviral infection and plasmid DNA transfection.
- Transformation assays using v-src, v-ras, and v-abl oncogenes.
- Analysis of v-src DNA, message, protein levels, and phosphotyrosine expression.
- Cotransfection experiments with v-src and neo plasmids to assess growth inhibition.
Main Results:
- v-src failed to transform 3T3-TNR9 cells, unlike v-ras and v-abl.
- Infected 3T3-TNR9 cells exhibited lower levels of v-src expression and phosphotyrosine compared to infected parental Swiss 3T3 cells.
- v-src demonstrated a growth inhibitory effect on 3T3-TNR9 cells, similar to TPA.
Conclusions:
- v-src cannot transform 3T3-TNR9 cells, indicating a reliance on TPA-responsive signalling pathways.
- The findings suggest that v-src utilizes the protein kinase C pathway as part of its signalling mechanisms for transformation.
- This study provides insights into the specific cellular pathways engaged by v-src during oncogenesis.