TGFBR1 and lip and oral cavity carcinoma: To elucidate the role of TGFBR3 in TGF-β signaling in oral cancer cells, we determined the effect of TGFBR3 expression on phosphorylation of SMAD2/3, an activation mark of the canonical TGF- β pathway, with or without SB431542, an inhibitor of TGFBR1.