CDKN2A and cervical squamous intraepithelial neoplasia: Multiple studies have demonstrated that the ascending methylation level of the CpG island (CGI) in the promoter region of cell cycle-related genes, such as cyclin-dependent kinase inhibitor 2A (CDKN2A) and alternate reading frame protein product (p14ARF), particularly in the DNA repair fragments impairs tumor suppression, ultimately causing CIN [31].