Common gene expression patterns responsive to mild temperature hyperthermia in normal human fibroblastic cells.

PURPOSE: Heat stress induces complex cellular responses, and its detailed molecular mechanisms still remain to be clarified. The objective of this study was to investigate the molecular mechanisms underlying cellular responses to mild hyperthermia (MHT) in normal human fibroblastic (NHF) cells. MATERIALS AND METHODS: Cells were treated with MHT (41°C, 30 min) and then cultured at 37°C. Gene expression was determined by the GeneChip® system and bioinformatics tools. RESULTS: Treatment of the NHF cell lines, Hs68 and OUMS-36, with MHT did not affect the cell viability or cell cycle. In contrast, many probe sets were differentially expressed by >1.5-fold in both cell lines after MHT treatment. Of the 1,196 commonly and differentially expressed probe sets analysed by k-means clustering, three gene clusters, Up-I, Down-I and Down-II, were observed. Interestingly, two gene networks were obtained from the up-regulated genes in cluster Up-I. The gene network E contained DDIT3 and HSPA5 and was mainly associated with the biological process of endoplasmic reticulum stress, while the network S contained HBEGF and LIF and was associated with the biological process of cell survival. Eighteen genes were validated by quantitative real-time polymerase chain reaction, consistent with the microarray data, in four kinds of NHF cells. CONCLUSIONS: Common genes that were differentially expressed and/or acted within a gene network in response to MHT in NHF cells were identified. These findings provide the molecular basis for a further understanding of the mechanisms of the MHT response in NHF cells.

Gene networks involved in apoptosis induced by hyperthermia in human lymphoma U937 cells.

To define the molecular mechanisms that mediate hyperthermia-induced apoptosis, we performed microarray and computational gene expression analyses. U937 cells, a human myelomonocytic lymphoma cell line, were treated with hyperthermia at 42 degrees C for 90 min and cultured at 37 degrees C. Apoptotic cells ( approximately 15%) were seen 6 h after hyperthermic treatment, and elevated expression of heat shock proteins (HSPs) including Hsp27, Hsp40, and Hsp70 was detected, following the activation of heat shock factor-1. Of the 54,675 probe sets analyzed, 1334 were upregulated and 4214 were downregulated by >2.0-fold in the cells treated with hyperthermia. A non-hierarchical gene clustering algorithm, K-means clustering, demonstrated 10 gene clusters. The gene network U1 or U2 that was obtained from up-regulated genes in cluster I or IX contained HSPA1B, DNAJB1, HSPH1, and TXN or PML, LYN, and DUSP1, and were mainly associated with cellular compromise, and cellular function and maintenance or death, and cancer, respectively. In the decreased gene cluster II, the gene network D1 including CCNE1 and CEBPE was associated with the cell cycle and cellular growth and proliferation. These findings will provide a basis for understanding the detailed molecular mechanisms of apoptosis induced by hyperthermia at 42 degrees C in cells.