TGFB1 and head and neck cancer: The significantly greater effect of TGF-βR1 rs334348 than of TGF-β1 rs1800470 on reducing the risk of death and recurrence in patients with smoking-related head and neck cancer in the present study may be attributed to the location of TGF-β1 rs1800470 outside the 3’ untranslated region of TGF-β1, which might constrain its role in miRNA binding activity.