It has been reported that the levels of some prostaglandin receptors, such as IP (PGI2 receptor) and DP (PGD2 receptor), were reduced in CRC cells and the downregulation of one of them, DP2, has been related to differentiation of healthy epithelium to tumor (Gustafsson et al., 2007). The gene discussed is PTGDR; the disease is colorectal carcinoma.