PTGS2 and cancer: Synchronous activation of Wnt and Ras signaling cascades in a variety of transgenic mouse models of cancers, including colon [18], intestine [19], and liver [20], converge to up-regulate numerous genes (e.g., cyclooxygenase-2, c-myc and interleukin-8) [21,22,23], which promote tumorigenesis.