TGFA and thyroid gland carcinoma: By contrast, EGF and TGF-α were also found to be a potent chemotactic factors for these thyroid carcinoma cells like HB-EGF (37–39), but these growth factors are different from HB-EGF in that EGF or TGF-α binds to HER1 alone and that HB-EGF bears a heparin binding site, which binds to cell surface heparin sulfate proteoglycan, but not EGF or TGF-α.