Mammalian cell sensitivity to hyperthermia in various cell lines: a new universal and predictive description.

Introduction: The Cumulative Equivalent Minute at 43 °C (CEM43) thermal dose model has been empirically derived more than 30 years ago and still serves as a benchmark for hyperthermia protocols despite the advent of regulatory network models. However, CEM43 suffers from several limitations regarding its inability to predict the effect of complex time varying profiles (thermotolerance, step-down heating), to predict synergistic effects with drug treatments or to explain the specificity of a cell line in thermal resistance.Objective: Define a new generic predictive tool for thermal injury based on regulatory network models. Identify the biological parameters that account for the thermal resistance.Materials: Comparative study of cell survival upon hyperthermia collected from literature (17 sets in 11 publications that cover 14 different cell lines from 8 different tissues).Results: A dynamical model describes accurately cell survival according to the amplitude and duration of exposure but also molecular chaperone expression level. In the case of square shape hyperthermia, approximated analytical expression of the cell survival is derived from the dynamical model and compared to CEM43 description. The molecular chaperone expression level defines the thermal resistance of a given cell line and can be estimated from a single experimental result through an easy-to-use graphical tool.Conclusion: The tools offered here can be useful for designing treatments combining hyperthermia and chemotherapy targeting molecular chaperones, but also for designing personalized hyperthermic treatment by prior biochemical screening of molecular chaperones. These tools could advantageously replace the description of CEM43.