DNMT1 and cancer: Global hypomethylation has been attributed to three main causes: (1) a lack of coordination between DNMT-1′s activity and DNA replication, (2) a selection of hypomethylated DNA patterns accompanied by the overexpression of specific oncogenes or genomic instability that facilitate the growth and expansion of cancer cells, and (3) a consequence of alterations in the organization of chromatin and the cell disorganization produced during the progression of cancer [14,15].