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Clonal variation of cadmium response in human tumor cell lines
Abstract:
Subpopulations of human tumor-derived cell lines A101D, A204, and A549 were screened for Cd2+ cytotoxic response. Three of six A549, two of seven A101D, and four of seven A204 subpopulations were found to differ significantly from the parental line. A variant subpopulation of A101D (T3) was shown by flow cytometry to be comprised of cells having two distinct DNA histograms. One histogram, type 1, resembles that of normal human fibroblasts. The other, type 2, represents cells with one-third more DNA. Early passage T3 clonal populations were comprised primarily of type 1 cells. With passage, type 1 cells decreased relative to type 2 so that by passage 47 the culture was predominantly type 2. Correspondingly, the A101D T3 subpopulation became more Cd2+ sensitive with time in culture. Subclones having only type 1 DNA histograms were found to be Cd2+ resistant relative to subclones with type 2 histograms, and treatment of A101D T3 cultures having approximately equal amounts of type 1 and 2 cells with 2 microM Cd2+ resulted in the selection of type 1 cells. The enhanced Cd2+ resistance phenotype shown by A101D T3 type 1 cells correlated with reduced Cd2+ uptake and is not attributable to enhanced metallothionein synthesis.
Insights
Subpopulations of A101D cells exhibit varying responses to cadmium (Cd2+). Type 1 cells are Cd2+ resistant due to reduced uptake, not metallothionein synthesis.
Area of Science:
- Cell Biology
- Toxicology
- Cancer Research
Background:
- Tumor-derived cell lines are valuable models for studying cellular responses.
- Cadmium (Cd2+) is a toxic heavy metal with known cytotoxic effects.
- Cellular subpopulations can exhibit distinct phenotypic characteristics and responses.
Purpose of the Study:
- To screen human tumor-derived cell line subpopulations for differential cytotoxic responses to cadmium (Cd2+).
- To characterize the heterogeneity of Cd2+ sensitivity within cell line subpopulations.
- To investigate the mechanisms underlying Cd2+ resistance in specific cell subpopulations.
Main Methods:
- Screening of multiple subpopulations from A101D, A204, and A549 cell lines for Cd2+ cytotoxic response.
- Flow cytometry analysis to determine DNA content and cell cycle distribution (DNA histograms).
- Assessment of Cd2+ sensitivity, Cd2+ uptake, and metallothionein synthesis in selected subpopulations and subclones.
Main Results:
- Significant differences in Cd2+ sensitivity were observed among subpopulations of A101D, A204, and A549 cell lines.
- A variant A101D subpopulation (T3) displayed two distinct cell populations based on DNA content (Type 1 and Type 2).
- Type 1 cells (fibroblast-like DNA content) were Cd2+ resistant, showing reduced Cd2+ uptake, while Type 2 cells (increased DNA content) were more sensitive; this resistance was not due to metallothionein.
Conclusions:
- Cellular heterogeneity within tumor-derived cell lines contributes to differential Cd2+ cytotoxic responses.
- Cd2+ resistance in A101D T3 Type 1 cells is linked to reduced Cd2+ uptake.
- The observed Cd2+ resistance phenotype is independent of metallothionein synthesis, suggesting alternative resistance mechanisms.