TNF and neoplasm: These processes are correlated with the up‐regulation of angiogenesis factors such as hypoxia‐inducible factor‐1 (HIF‐α), vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF‐α), interleukin‐1β (IL‐1 β), prostaglandin E2 (PEG2), cyclooxygenase‐2 (COX‐2), survivin and matrix metalloproteinases in PDT‐treated tumors.150, 151, 152 These molecules may be related to tumor recurrence.