To explore the role of TGFB1 on thyroid-differentiated gene expression in thyroid tumors, we first tested the TGFB1-neutralizing MAB 1D11 and the TGFBR1 (TβR1) kinase inhibitor SD-208 in cell lines derived from mouse BRAFV600E-PTCs, where both effectively blocked the TGFB1-induced SMAD2/3 phosphorylation (Supplementary Fig. 1A). Here, TGFBR1 is linked to thyroid tumor.