However, contrary to its anti-angiogenic effects, numerous studies have reported that IR would undesirably stimulate tumor cells to up-regulate proangiogenic molecules, such as VEGF [7–10], basic fibroblast growth factor [11], matrix metalloproteinase (MMP)-2 [12, 13], MMP-9 [10, 12], urinary plasminogen activator [10], ephrin-A1 [14], prostaglandin E2 [15] and a profile of cytokines [16], which may contribute to tumor radioresistance [7, 8, 14] or tumor repopulation [15, 17]. This evidence concerns the gene MMP2 and neoplasm.