We show that anaplastic thyroid carcinoma exhibits an elevated expression of EZH2, and its inhibition through either CRISPR/Cas9-induced EZH2 gene editing or with EPZ6438 inhibitor improves thyroid follicular-cell differentiation and induces mesenchymal–epithelial transition. The gene discussed is EZH2; the disease is thyroid gland undifferentiated (anaplastic) carcinoma.