PTEN and cancer: For example, hypermethylation of retinoblastoma protein (RB), phosphatase and tensin homolog (PTEN), breast cancer type 1 susceptibility protein (BRCA1), breast cancer type 2 susceptibility protein (BRCA2), O6-methylguanine-DNA methyltransferase (MGMT), cyclin-dependent kinase inhibitor 2B (CDKN2B), and Ras-association-domain-containing protein 1A (RASSF1A) are all reported in cancer, and result in the loss of ability to protect against tumorigenesis [243,244,245,246].