Because de novo DNA methyltransferase DNMT3B is often silenced in CRC cell lines and primary CRC tumors, as a consequence of aberrant DNA hypermethylation of its distal promoter33, we postulated that increased expression of miR-21 in CRC may be a consequence of DNMT3B activity, and DNMT3B is likely responsible for hypermethylation of miR-21, which usually occurs in healthy colon tissues. The gene discussed is DNMT3B; the disease is colorectal carcinoma.