Gene profiling of apoptosis induced by heat stress in U937 human lymphoma cells

Hyperthermia is widely used to treat patients with various cancers. 42.5˚C is well known as the inflection point of hyperthermia and generally up to 42˚C of hyperthermia is used in clinical cases combined with other therapies. Here, the effects of heat stress at 42 or 44˚C for 15 min on the gene expression in human lymphoma U937 cells were investigated using an Affymetrix GeneChip system. The cells were treated with heat stress (42 or 44°C for 15 min), followed by incubation for 0, 1, 3 or 6 h at 37°C. The percentage of DNA fragmentation was 8.4 ± 2.2 (mean ± SD) at 42°C for 6 h and 21.0 ± 2.0 at 44°C for 6 h. Of approximately 47,000 probe sets analyzed, many genes that were differentially expressed by a factor 2.0 or greater were identified in the cells treated with heat stress at 42 and 44°C. U937 cells, a human lymphoma cell line, were treated with heat stress (42 or 44°C for 15 min), followed by incubation for 0, 1, 3 or 6 h at 37°C. Non-treated cells served as the control. Total RNA samples were prepared from the cells. Gene expression was analyzed by an Affymetrix GeneChip® system with a Human Genome U133-plus 2.0 array for analysis of over 47,000 transcripts. Sample preparation for array hybridization was carried out as described in the manufacturer’s instruction