In the apoptosis of cancer cells, various signaling pathways have been involved, including mitogen-activated protein kinase (MAPK), cyclooxygenase-2 (COX-2), Janus kinase (JAK), phosphatidylinositol 3-kinase (PI3K), signal transducer and activator of transcription (STAT3) and endoplasmic reticulum stress [53,54,55,56,57,58,59]. Here, PTGS2 is linked to cancer.