GPR68 and neoplasm: ii) In contrast to the promoting role of OGR1 in tumor proliferation, OGR1 has been demonstrated to be a tumor metastasis suppressor gene in prostate cancer (Singh et al., 2007) and ovarian cancer (Ren and Zhang, 2011) OGR1 expression was lower in distant metastatic lesions than in primary tumors (LaTulippe et al., 2002).