Fig. 1

The changes of DNA methylation between young normal cells and aging cancer cells. There is the comparison and discussion between young normal cells and aging cancer cells. In young normal cells, the low methylation and unmethylated CpGs are the preserve of the promoter of tumor suppressor gene (TSG), which spawns the expression of TSG in the wake of producing young normal cells. However, the genome and intergenic regions make it to the higher methylation comparing to the promoter to keep them stable. By contrast, the promoter of TSG was highly methylated in aging cancer cells, obviously resulting in the transcriptional repression as well as loss of TSG expression. What is more, the genome and intergenic regions will be at the opposite stage of hypomethylation in aging cancer cells, which is responsible for the transcriptional activation and genomic instability, oncogenes’ expression holding one example. As a consequence, these abnormal DNA methylations give birth to tumorigenesis finally