TGFB1 and thyroid cancer: To determine whether the TGFβ/SMAD pathway is activated in BRAFV600E-driven PTC in vivo, we performed pSMAD Western blots in tumor lysates from TPO-Cre/LSL-BrafV600E mice, which develop thyroid cancers with high penetrance by 5 weeks of age (Franco et al. 2011).