First, we confirmed that COX2 activity can change the expression of some of the genes we have identified as COX2-target or effector genes in human cancer (Stamatakis et al., 2015; Jiménez-Martínez et al., 2019; Jiménez-Segovia et al., 2019; Hidalgo-Estévez et al., 2020), namely, Ptge2, Ptges, Dusp10, Pmepa1, Inhba, Il15, and Nfkbia. There was also a tendency for Klf4, Tacstd2, Nfat5, Tgfb1, and Il15ra to be upregulated with COX2 overexpression in CT26 cells, as it happened in HT29 human cells, but without reaching statistical significance. This evidence concerns the gene PTGS2 and cancer.