CDKN2A and breast cancer: Manel Esteller et al. [28] summarized the relationship between gene methylation and various types of cancer, such as bladder cancer, cervical cancer, melanoma and glioma, with p16 methylation as a trait; high levels of p14 and APC methylation are common in gastrointestinal cancer (such as colon cancer and stomach cancer), while GSTP1 demonstrates high methylation levels in breast cancer and prostate cancer.