Anti-angiogenic action of hyperthermia by suppressing gene expression and production of tumour-derived vascular endothelial growth factor in vivo and in vitro

Vascular endothelial growth factor is an important angiogenic factor for tumour progression because it increases endothelial-cell proliferation and remodels extracellular matrix in blood vessels. We demonstrated that hyperthermia at 42°C, termed heat shock, suppressed the gene expression and production of vascular endothelial growth factor in human fibrosarcoma HT-1080 cells and inhibited its in vitro angiogenic action on human umbilical vein endothelial cells. The gene expression of alternative splicing variants for vascular endothelial growth factor, VEGF(121), VEGF(165) and VEGF(189), was constitutively detected in HT-1080 cells, but the VEGF(189) transcript was less abundant than VEGF(121) and VEGF(165). When HT-1080 cells were treated with heat shock at 42°C for 4 h and then maintained at 37°C for another 24 h, the gene expression of all vascular endothelial growth factor variants was suppressed. In addition, HT-1080 cells were found to produce abundant VEGF(165), but much less VEGF(121), both of which were inhibited by heat shock. Furthermore, the level of vascular endothelial growth factor in sera from six cancer patients was significantly diminished 2–3 weeks after completion of whole-body hyperthermia at 42°C (49.9±36.5 pg ml(−1), P<0.01) as compared with that prior to the treatment (177.0±77.5 pg ml(−1)). On the other hand, HT-1080 cell-conditioned medium showed vascular endothelial growth factor-dependent cell proliferative activity and the augmentation of pro-matrix metalloproteinase-1 production in human umbilical vein endothelial cells. The augmentation of endothelial-cell proliferation and pro-matrix metalloproteinase-1 production was poor when human umbilical vein endothelial cells were treated with conditioned medium from heat-shocked HT-1080 cells. These results suggest that hyperthermia acts as an anti-angiogenic strategy by suppressing the expression of tumour-derived vascular endothelial growth factor production and thereby inhibiting endothelial-cell proliferation and extracellular matrix remodelling in blood vessels. British Journal of Cancer (2002) 86, 1597–1603. DOI: 10.1038/sj/bjc/6600268 www.bjcancer.com © 2002 Cancer Research UK