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Determinants of cisplatin sensitivity in non-malignant non-drug-selected human T cell lines
M Dabholkar1, R Parker, E Reed
1Medicine Branch, National Cancer Institute, Bethesda, MD 20892.
Abstract:
We have studied molecular mechanisms of cisplatin sensitivity and resistance in 3 non-malignant, non-drug-selected human T lymphocyte cell lines. HuT 78, H9, and MOLT-4 cells were assessed for sensitivity to cisplatin, DNA damage levels following defined drug exposures, drug accumulation, and DNA repair efficiency as measured by adduct removal from cellular DNA and by host-cell reactivation of cisplatin-modified plasmid DNA. Based on 3-day continuous drug exposures, the IC50 values for the cell lines were: HuT 78, 0.83 microM; H9, 0.45 microM; and MOLT-4, 0.33 microM. These cells retained this order with respect to DNA repair capability, whether measured by platinum-DNA adduct removal from cellular DNA or by host-cell reactivation assays. DNA repair values measured by these two assays were directly related to one another with a linear correlation coefficient of 0.993. At sublethal cisplatin doses the more resistant cells showed the highest levels of drug uptake. When drug uptake levels were 'corrected' for drug-induced cell kill, there were equal levels of DNA repair efficiency for a given level of drug uptake. Absolute levels of cisplatin-DNA adduct repair increased with increasing drug dose. However, at supralethal doses of drug, efficient DNA repair could be overcome in all 3 cell lines with percentage-adduct-removal dropping from a 60-80% range to a less than 30% range. We conclude that in non-malignant non-drug-selected human T cells, DNA repair appears to be the primary determinant of cisplatin sensitivity/resistance and that enhanced DNA repair may be a biologic compensatory mechanism for cells that cannot prevent cellular uptake of DNA-damaging agents.
Insights
DNA repair efficiency is the main factor determining cisplatin sensitivity in human T cells. Enhanced DNA repair may compensate for high drug uptake, but can be overwhelmed by high cisplatin doses.
Area of Science:
- Molecular Biology
- Cell Biology
- Pharmacology
Background:
- Cisplatin is a widely used chemotherapy drug.
- Understanding cisplatin resistance mechanisms is crucial for improving cancer treatment.
- Non-malignant T lymphocytes offer a model to study intrinsic cellular responses to drugs.
Purpose of the Study:
- To investigate the molecular mechanisms underlying cisplatin sensitivity and resistance in human T lymphocytes.
- To determine the role of DNA repair, drug accumulation, and DNA damage in cellular response to cisplatin.
Main Methods:
- Assessed cisplatin sensitivity using IC50 values in three human T lymphocyte cell lines (HuT 78, H9, MOLT-4).
- Measured DNA damage levels, drug accumulation, and DNA repair efficiency via adduct removal and host-cell reactivation assays.
- Correlated DNA repair capacity with drug sensitivity and uptake.
Main Results:
- Cell lines exhibited varying sensitivity to cisplatin, with IC50 values ranging from 0.33 to 0.83 microM.
- DNA repair capability, measured by two independent assays, directly correlated with cisplatin resistance (R=0.993).
- Higher drug uptake was observed in more resistant cells at sublethal doses, but DNA repair efficiency was similar when corrected for cell kill.
Conclusions:
- DNA repair efficiency is the primary determinant of cisplatin sensitivity/resistance in these non-malignant human T cells.
- Enhanced DNA repair may serve as a compensatory mechanism for cells with higher drug uptake.
- Efficient DNA repair can be overcome by supralethal doses of cisplatin, leading to significant DNA damage.
