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Effects of ouabain on NIH/3T3 cells transformed with retroviral oncogenes and on human tumor cell lines
P Tagliaferri1, K Yanagihara, F Ciardiello
1Laboratory of Tumor Immunology and Biology, National Cancer Institute, Bethesda, MD 20892.
Abstract:
Both murine and human cell lines transformed by the v-Ki-ras gene have been shown to be much more sensitive to the toxic effects of the cardiac glycoside ouabain than their respective controls. This differential toxicity has previously been used in the isolation of flat revertant clones from populations of Kirsten murine sarcoma virus transformed NIH/3T3 cells. Here, we have undertaken a further characterization of this phenomenon in murine and human tumor cells. Two different techniques, a 51Cr-release assay and a quantitative Crystal violet elution assay, have been employed to compare the sensitivities to ouabain of normal and v-Ki-ras-transformed NIH/3T3 cells. In each assay, ras-transformed NIH/3T3 cell lines displayed an increased sensitivity to ouabain as compared to the parental NIH/3T3 cell line, both in dose-response and in time-course experiments. In a separate study, ouabain was also able to inhibit the growth in semi-solid medium of 2 v-Ki-ras-transformed NIH/3T3 cell lines (DT and K-NIH) in a dose-dependent fashion. The same concentrations of ouabain were effective in both the 51Cr-release and Crystal violet assays. To address the question of whether increased sensitivity to ouabain is a specific result of transformation with the ras oncogene or is a common event which accompanies transformation by other oncogenes, we have screened a variety of transformed NIH/3T3 derivatives. All of these lines displayed an increased sensitivity to ouabain when compared to the parental NIH/3T3 cell line.
Insights
Ras oncogene transformation increases sensitivity to ouabain in both murine and human cells. This heightened sensitivity to the cardiac glycoside ouabain was observed across various cell types and experimental assays.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- v-Ki-ras gene transformation confers increased sensitivity to ouabain in murine and human cell lines.
- This differential toxicity has been utilized for isolating specific cell clones.
Purpose of the Study:
- To further characterize the phenomenon of ouabain hypersensitivity in ras-transformed cells.
- To investigate if this increased sensitivity is specific to ras oncogene transformation or a general effect of oncogenic transformation.
Main Methods:
- Utilized 51Cr-release and Crystal violet elution assays to compare ouabain sensitivity in normal and v-Ki-ras-transformed NIH/3T3 cells.
- Assessed ouabain's effect on the growth of transformed cells in semi-solid medium.
- Screened various NIH/3T3 cell derivatives transformed by different oncogenes.
Main Results:
- Ras-transformed NIH/3T3 cell lines showed significantly increased sensitivity to ouabain compared to parental cells in both dose-response and time-course experiments.
- Ouabain effectively inhibited the growth of v-Ki-ras-transformed NIH/3T3 cell lines in semi-solid medium.
- All tested NIH/3T3 cell lines transformed by various oncogenes exhibited enhanced sensitivity to ouabain.
Conclusions:
- Transformation by the ras oncogene specifically enhances cellular sensitivity to ouabain.
- Increased ouabain sensitivity is a common characteristic of NIH/3T3 cells transformed by different oncogenes, suggesting a broader implication in cancer biology.