DNMT1 and neoplasm: The promoters of these genes become demethylated also in many tumor cells, opening up the possibility that passive demethylation, due to silencing of Dnmt1, is involved in determining the diffuse genome-wide hypomethylation which has been associated with chromatin decondensation [8], genomic instability [14], apoptosis [15], cancer [4], [6], [7], [16], disruption of nucleolar architecture [17], aberrant telomere elongation [18], loss of imprinting during preimplantation development [19], [20], and even mitotic catastrophe [21].