Specific examples of DNA methylation role in cancers include hypermethylation of BRCA1 in breast and ovarian cancer [22,23]; DOK7 in breast cancer [22]; MYOD1 in hematological neoplasm; APC, HOX2, OTX1 genes in non-small cell lung carcinoma (NSCLC) [24]; FEN1 in breast tumor cells [25]; and hypomethylation of TKTL1 in head and neck squamous cell carcinoma [26]. The gene discussed is FEN1; the disease is non-small cell lung carcinoma.