Retinoids, derivatives of vitamin A (retinol), decrease signaling via the major pathways that promote CRC progression, such as Wnt/β-catenin signaling, K-ras mutations, phosphatidylinositol-3-kinase/Akt, cyclooxygenase-2 overexpression, peroxisome proliferator-activated receptor γ activation, and loss of p53 function35. This evidence concerns the gene PTGS2 and colorectal carcinoma.