title: Cytotoxicity of hepatocellular carcinoma cells to hyperthermic and ablative temperature exposures: in vitro studies and mathematical modelling.
abstract: OBJECTIVE
  Image-guided ablative therapies use temperatures greater than 45 °C to kill abnormal cells. There is limited published data of cell survival after ablative temperature exposures, which is of importance to predict ablation zone dimensions. The objective of this study was to determine and mathematically model survival of hepatocellular carcinoma cells following ablative temperature exposures (45-60 °C).
  
  
  METHODS
  Hepatocellular carcinoma (HCC) cell lines were plated in 96-well plates, and heated between 45 and 60 °C for 0-32 min. Heating was applied by a rapid media exchange with heated Hank's balanced salt solution (HBSS) in a temperature-controlled water bath. Cell viability was determined by MTS assay. Survival data was modelled by the Arrhenius model, and the thermal isoeffective dose (TID) model where kinetic parameters were determined via non-linear optimisation.
  
  
  RESULTS
  Results suggest that the thermal dose based on cumulative equivalent minutes and parameters as used for hyperthermia exposures (<43 °C) is not applicable for ablative exposures. We found R = 0.72 for temperatures between 45-60°C for the TID model. The Arrhenius parameters were frequency factor A = 3.25E43 1/s, and activation energy Ea = 281 kJ/mol. These parameters correlate well with a prior study in the same cell line, and with threshold temperatures for necrosis from in vivo studies.
  
  
  CONCLUSIONS
  Our results suggest that standard TID model kinetic parameters based on hyperthermia studies, often also used at ablation temperatures, are not applicable at these higher temperatures for HCC cells.
authors.affiliation: Department of Radiology and Imaging Sciences, Clinical Center, Center for Interventional Oncology, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Goutham
authors.initials: G
authors.lastname: Reddy
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Dreher
authors.forename: Christian
authors.initials: C
authors.lastname: Rossmann
authors.forename: Bradford J
authors.initials: BJ
authors.lastname: Wood
authors.forename: Dieter
authors.initials: D
authors.lastname: Haemmerich
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000628:therapy*; D002470:Cell Survival; D056945:Hep G2 Cells; D006358:Hot Temperature; D006801:Humans; D006979:Hyperthermia, Induced; D008113:Liver Neoplasms / Q000628:therapy*; D008954:Models, Biological