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Time-temperature relationships for step-down heating in normal and thermotolerant cells
J van Rijn1, J van den Berg, F A Wiegant
1Department of Radiation Oncology, Free University Hospital, Amsterdam, The Netherlands.
Summary
Step-down heating (SDH) significantly reduces thermotolerance by sensitizing cells to heat. SDH alters heat response kinetics, decreasing activation energies and impacting thermotolerance induction and expression differently in normal versus thermotolerant cells.
Area of Science:
- Cellular biology
- Hyperthermia research
- Cancer therapy
Background:
- Thermotolerance, a protective response to heat stress, can limit the efficacy of hyperthermia treatments.
- Step-down heating (SDH) is a technique investigated for its potential to overcome thermotolerance.
- Understanding the kinetics of heat response is crucial for optimizing hyperthermia protocols.
Purpose of the Study:
- To investigate the effects of step-down heating (SDH) on thermotolerance induction and expression in normal and thermotolerant H35 cells.
- To compare the dose-effect relationships of SDH in cells with and without pre-existing thermotolerance.
- To determine the time-temperature relationships and activation energies associated with SDH in different cellular states.
Main Methods:
- H35 cells, both normal and thermotolerant, were subjected to SDH, involving a sensitizing treatment (ST) followed by a test treatment (TT) at lower temperatures.
- Dose-effect relationships were established by plotting the surviving fraction after ST against the D0 (thermal dose) of the TT.
- Arrhenius plots were used to analyze the time-temperature relationships and activation energies for SDH effects.
Main Results:
- SDH significantly reduced thermotolerance induction and expression.
- Non-thermotolerant cells showed a weaker dose-effect relationship at 42.5°C but strong inhibition of thermotolerance at 41°C after specific ST doses.
- Thermotolerant cells exhibited a higher degree of thermosensitization across a broader range of ST doses compared to non-thermotolerant cells.
- SDH shifted inflection points in Arrhenius plots and generally decreased activation energies for heat response.
Conclusions:
- SDH is effective in reducing thermotolerance, with varying impacts depending on cell state (thermotolerant vs. normal) and test temperature.
- The dose-effect relationships and kinetic parameters (activation energies) of heat response are significantly altered by SDH.
- SDH demonstrates potential for enhancing hyperthermia efficacy by overcoming cellular thermotolerance, though its precise application requires careful consideration of temperature and cell status.