In this study, we observed that although STAG2 was down-regulated in thyroid cancers and knocking down STAG2 in BRAF-mutant thyroid cancer cells caused a conspicuous up-regulation of phosphorylated ERK (p-ERK), it virtually had no effect on malignant phenotypes of these cells and their response to MEK inhibitor. The gene discussed is BRAF; the disease is thyroid gland carcinoma.