Evaluation of Tumor Cell Response to Hyperthermia with Bioluminescent Imaging.

BACKGROUND Hyperthermia is used in combination with radiotherapy and/or chemotherapy in the treatment of various types of cancer. Currently, the tumor cell response to hyperthermia is determined largely based on the size reduction of tumor mass, which is insensitive. METHODS We tested the feasibility of bioluminescent imaging (BLI) in evaluation of the tumor cell response to hyperthermia by exposing luciferase-expressing MDA-MB-231-luc human breast cancer cells to high temperature (43 °C) for 10 minutes to 2 hours. The tumor cells were the imaged and the light signal generated by the tumor cells was quantified with BLI. To validate its usefulness, the light signal intensity was comparatively analyzed with the tumor cell clonogenicity and cell viability, which were measured with classic clonogenic and MTT assays. RESULTS The light signal intensity determined by BLI was closely correlated with the absolute number of viable cells as well as the cell viability measured with the traditional MTT assay under normal culture condition. Relative to the clonogenicity of tumor cells after exposure to hyperthermia, however, BLI underestimated, while MTT assay overestimated the cell viability. Difference in the interpretation of tumor cell clonogenic ability following hyperthermia with BLI, MTT dye, and clonogenic assay may be due to the different mechanisms of the three measurements as well as the fact that hyperthermia can induce cell damage at levels of both transient and permanent. CONCLUSIONS BLI is sensitive, convenient, and potentially valuable in the evaluation and monitoring of tumor cell response to treatments including hyperthermia.