In addition, our data indicate that it is not necessary to take into consideration the expression level of Dnmt1 and/or PCNA since none correlation between the Dnmt1 level expression and the 5 mC number was observed in a large number of glioma and 2) since the Dnmt1/PCNA interactions can be inhibited by other events that the level expression of these proteins (such as the phosphorylation of Dnmt1, the presence of peptide/protein imitating the action of the UP peptide [17,18]. Here, PCNA is linked to central nervous system cancer.