GPR68 and neoplasm: As Ogr1 can be detected in a variety of tumor tissues in addition to host cells, we also use lentiviral vectors carrying shRNA or Ogr1-overexpressing lentiviruses to generate Ogr1-knockdown or Ogr1-highB16-F10 cells, respectively (Supplementary Fig. 1C, D), to assess the role of Ogr1 in B16-F10 cells in tumor progression.