TGFB1 and neoplasm: While there are three ligands within the TGF-β family (TGF-β1, TGF-β2, and TGF-β3) which are highly homologous and perform similar biologic functions, previous studies have shown the upregulation of TGF-β1 in HNSCC epithelia relative to normal tissue, suggesting the heightened importance of this ligand in tumor pathogenesis [27].