Prostaglandin E2 (PGE2)—a major metabolite derived from arachidonic acid (AA) via the cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1) pathway—is ubiquitously overexpressed in colorectal cancer and functions as a key immunosuppressive mediator. The gene discussed is PTGS2; the disease is colorectal cancer.