Application of the ATP-bioluminescence assay to thermosensitivity testing for head and neck cancer

We investigated the usefulness of the ATP assay as a thermosensitivity test in comparison with a colony-forming assay (CFA). The intracellular ATP levels in KB cells were markedly decreased after exposure to hyperthermia (43 degrees C for 1 h), reaching less than half that in the control cells in 12-18 h, and recovering gradually thereafter. The effect of hyperthermia assessed by the ATP assay closely correlated to that assessed by CFA, not only when KB cells were heated at 42, 43, and 44 degrees C but also in the conditions where L, KB and IMC-3 cell lines were heated at 43 degrees C. Findings showed that the ATP assay can be performed easily and more quickly than CFA for evaluating cell viability after heating. We also investigated heterogeneous responses to hyperthermia in cells from fresh surgical specimens of tumors. Thus, this rapid and reliable test was found to be useful for predicting the outcome of hyperthermia as a clinical treatment.