Prostanoids bind to a family of 8 GPCRs to exert their biological effects. The prostanoid PGE2 causes pain, vasodilation, immunosuppression of T cells, bone resorption and promotion of carcinogenesis. Four related GPCRs, EP1, EP2, EP3 and EP4, each bind PGE2, but the different G protein coupling of each receptor leads to distinct biological effects. EP2 couples primarily to Gs to increase intracellular cAMP levels. Mice deficient in EP2 receptor showed impaired ovulation and fertilization in addition to salt-sensitive hypertension. It has been shown that EP2 receptors are also involved in cancer-associated immunodeficiency. Thus, genetic knockout of the EP2 receptor reduced tumor growth and prolonged survival in mice that had undergone isograft injection of MC26 or Lewis lung carcinoma cells.