A genomics approach to identify susceptibilities of breast cancer cells to "fever-range" hyperthermia

Background: Preclinical and clinical studies have shown for decades that tumor cells demonstrate significantly enhanced sensitivity to "fever range" hyperthermia (increasing the intratumoral temperature to 42-45 degrees C) than normal cells, although it is unknown why cancer cells exhibit this distinctive susceptibility. Methods: To address this issue, mammary epithelial cells and three malignant breast cancer lines were subjected to hyperthermic shock and microarray, bioinformatics, and network analysis of the global transcription changes was subsequently performed. Results: Bioinformatics analysis differentiated the gene expression patterns that distinguish the heat shock response of normal cells from malignant breast cancer cells, revealing that the gene expression profiles of mammary epithelial cells are completely distinct from malignant breast cancer lines following this treatment. Using gene network analysis, we identified altered expression of transcripts involved in mitotic regulators, histones, and non-protein coding RNAs as the significant processes that differed between the hyperthermic response of mammary epithelial cells and breast cancer cells. We confirmed our data via qPCR and flow cytometric analysis to demonstrate that hyperthermia specifically disrupts the expression of key mitotic regulators and G2/M phase progression in the breast cancer cells. Conclusion: These data have identified molecular mechanisms by which breast cancer lines may exhibit enhanced susceptibility to hyperthermic shock.