When GREB1 protein expression was examined in cancer cell lines using an anti-GREB1 antibody (#1) that recognizes the N-terminal region of GREB1 (Supplementary Fig. S1B), full-length GREB1 (216 kDa) was detected only in HepG2 (hepatoblastoma) and MCF7 (breast cancer) but not in melanoma cell lines (Fig. 1C, left blot). Here, GREB1 is linked to melanoma.