Dose-dependent effect of radiation on VEGF protein expression. VEGF protein levels in LLC-conditioned medium are shown after radiation exposure. LLCs were plated in six-well plates at 25% confluence, allowed to attach overnight, and then irradiated with 0, 5, 10, or 20 Gy. Conditioned medium was collected every 24 hours and VEGF levels were normalized to cell number. Data are presented as mean plus standard error . Abbreviations: LLC = Lewis lung carcinoma; VEGF = vascular endothelial growth factor. Reprinted with permission from Gorski DH, Beckett MA, Jaskowiak NT, et al. Blockage of the vascular endothelial growth factor stress response increases the antitumor effects of ionizing radiation. Cancer Res 1999;59:3374-3378; Figure 1B.