Identification of genes responsive to mild hyperthermia in human leukemia U937 cells

The rationale underlying hyperthermia is the fact that temperatures over 42.5˚C are highly cytotoxic to tumor cells. On the other hand, although mild hyperthermia at a range from 39 to 41˚C alone did not induce cytotoxicity in tumor cells, mild hyperthermia is reported to show a synergism with radiotherapy and anti-cancer drugs. Here, the effects of mild hyperthermia (41˚C for 30 min) on the gene expression in human lymphoma U937 cells were investigated using by an Affymetrix GeneChip system. Although the cells treated with the mild hyperthermia did not induce apoptosis, a significant increase in protein levels of heat shock proteins, Hsp40 and Hsp70, was observed following activation of heat shock factor-1. At 3 h post-treatment, 938 probe sets that were differentially expressed by >1.5-fold were identified. Keywords: mild hyperthermia, gene expression, Human lymphoma U937 cell U937 cells, a human lymphoma cell line, were treated with mild hyperthermia (41˚C for 30 min) and followed by incubation for 3 h at 37°C. Non-treated cells were served as control. Total RNA samples were prepared from the cells. Gene expression was analyzed by an Affymetrix GeneChip® system with Human Expression Array U133A which was spotted with 22,283 probe sets. Sample preparation for array hybridization was carried out as described in the manufacture’s instructions.