PTGS2 and esophageal cancer: Cytokines secreted during inflammation, such as interleukin-1 (IL-1) and tumor necrosis factor-α (TNF-α), as well as reactive oxygen species (ROS), could activate cyclooxygenase 2 (COX-2), which contributed to the development, metastasis, and neo-angiogenesis of esophageal cancer 32.