CREB1 and malignant colon neoplasm: PGE2 increases cyclic adenosine monophosphate (cAMP) and intracellular Ca2+ levels through EP1 and EP2 receptors, activating PKA, which mediates CRTC1 signaling by promoting the transcriptional enhancement of tumor-promoting genes in human colon cancer cells through CREB and AP1 [10].