TBR1 and neoplasm: To investigate the roles of activin and TGFB1 on SMAD activation in vivo, tumor-bearing Braf and Braf/TβR1 mice were treated with EW7197 or with follistatin, a potent inhibitor of several TGFβ family ligands (primarily activin and to a lesser extent BMPs, myostatin, and possibly TGFB3 – but not TGFB1 or 2) (Nogai et al. 2008, Sepporta et al. 2013).