Since the PTC cell line (SNU790, SNU790-CXCR4) did not form a tumour mass in nude mice (Supplementary Fig. 15), we used the anaplastic thyroid cancer cell line (HTH83; BRAF wild type and HRASQ61R+/−)22, which exhibited higher CXCR4 expression (Supplementary Fig. 7). Here, CXCR4 is linked to thyroid gland undifferentiated (anaplastic) carcinoma.