It should be noted that although CYP2S1 is classified into the CYP2 family based on its amino acid sequence identity,19 it exhibits typical features of CYP1 family members such as induced by dioxin via AHR.10,20 Thus, we suppose that BRAFV600E regulates CYP2S1 expression in thyroid cancer cells probably by AHR. The gene discussed is AHR; the disease is thyroid cancer.