Prostanoids, including PGD2, PGE2, PGF2α, PGI2, and TXA2, activate nine GPCRs, namely PTGDR1, PTGDR2, PTGER1, PTGER2, PTGER3, PTGER4, PTGFR, PTGIR, and TBXA2R. PTGDR1 downregulation by DNA hypermethylation is correlated with colorectal cancer development [26, 27]. This evidence concerns the gene PTGER3 and colorectal cancer.