CYP4X1 is a cytochrome P450 monooxygenase that selectively catalyzes epoxidation of anandamide's arachidonoyl moiety, modulating endocannabinoid signaling through insertion of molecular oxygen with electrons provided by NADPH via cytochrome P450 reductase 1. The enzyme is predominantly expressed in trachea, aorta, and brain, where it constitutes approximately 10 ng/mg microsomal protein in neurons, choroid epithelial cells, and vascular endothelial cells 2. CYP4X1 expression is regulated by PPARα activation 1 and shows female-biased hepatic expression 3. Mechanistically, CYP4X1/sEH-dependent endocannabinoid metabolism produces 14,15-EET-EA, which upregulates PD-L1, CXCL12, and TGF-β in cancer-associated fibroblasts via GPR119 signaling, promoting immune evasion in colorectal cancer 4. In immune checkpoint inhibitor toxicity, the butyrate-PPARα-CYP4X1 axis downregulation drives M1 macrophage polarization and proinflammatory factor production 5. Clinically, CYP4X1 overexpression correlates with advanced TNM stage, lymph node metastasis, and shorter survival in colorectal cancer patients 6. Additionally, CYP4X1 polymorphisms modulate disease onset in genetic and sporadic Creutzfeldt-Jakob disease 7.