Immunohistochemical analyses confirmed that the level of HIF-1α protein at the edges of DAPI-positive viable regions correlated with that of bioluminescent intensity in the irradiated HeLa/5HREp-ODD-Luc xenografts (Figure 1C and D, left graph), indicating that the HIF-1α level is mainly responsible for the postirradiation HIF-1 activity in the tumour xenograft. This evidence concerns the gene HIF1A and neoplasm.