PTGS2 and digestive system cancer: The phosphorylation of RXRα was associated with colon carcinogenesis; however, inhibition of this phosphorylation and inducing the heterodimerization of unphosphorylated RXR–PPARγ in the presence of their ligands, 9-cisRA, and ciglitazone, synergistically suppressed cell growth and induced apoptosis by reducing COX-2 and c-Jun at both protein and RNA level [124].