DNMT1 and neoplasm: Direct modifications of the structure of DNMT1 or interference with its interactions in the DNMT1/PCNA/UHRF complex, in several human cell lines, resulted in global DNA hypomethylation, a characteristic of almost all human tumour cells [148,149], hypomethylation of a variety of TSGs and oncogenes, as well as hypermethylation of several TSGs [148].