SMAD2 and thyroid gland papillary carcinoma: Although some studies in other cancers indicated that SIX1 regulates EMT processes through the TGF-β/Smad2/3 signaling pathway in papillary thyroid cancer [22], there is no direct evidence that SIX1 induces EMT via the TGF-β/Smad2/3 signaling pathway in GC.