Additionally, fragments of cytokeratin (CYFRA), carcinoma embryonic antigen (CEA), immunosuppressive acidic protein (IAP), cyclooxygenase-2 (COX-2), soluble CD44, matrix metalloproteinase (MMPs), and their tissue inhibitors (TIMPs) are used as diagnostic and prognostic protein biomarkers, even though their levels fluctuate considerably depending on the cancer type and stage [40]. This evidence concerns the gene PTGS2 and cancer.