Unlike what we had previously observed in Ogr1−/− mice, B16-F10-shOgr1 tumors did not show altered growth compared with WT tumors (Fig. 1A, B) and a high expression of Ogr1 in B16-F10 cells increased the tumor malignancy to some extent (Supplementary Fig. 1E, F) further indicating that Ogr1 expression in host cells may be functionally critical in tumor regression models. This evidence concerns the gene GPR68 and neoplasm.