PTGS2 and cancer: COX-2 is overexpressed in many types of cancer leading to the formation of excess of PGE2 [153], and the autocrine COX-2/PGE2 pathway can confer tumor cell resistance to apoptosis by different ways, including the up-regulation of the β-catenin and Ras/Raf/MEK/ERK signaling pathways [154].