DNMT1 and cancer: This supposition is based on two lines of evidence: first, despite being DNMT1-deficient, a colon adenocarcinoma cell line was shown to be capable of retaining 80% of its methylation level while replicating, which implies that DNMT3 may perform a function in the maintenance of methylation [30]; secondly, forced DNMT1 overexpression in cancer cell lines does, indeed, induce de novo methylation [31].