OGR1 was originally cloned and characterized from human ovarian cancer tissue (it is not expressed in healthy ovarian tissue) (Xu and Casey, 1996), and its role as a proton-sensing GPCR was first described by Ludwig et al. (2003) The author observed the protons in the largest activation OGR1 at a pH of 6.8. Here, GPR68 is linked to ovarian cancer.