CDKN2A and lung cancer: Researchers have recently suggested the use of aberrant CpG island methylation for early detection of lung cancer, and tumor‐suppressor genes are considered a molecular marker system in the promoter region for early identification of lung cancer, for example, cyclin‐dependent kinase inhibitor 2A (p16INK4A), O6‐methylguanine‐DNA methyltransferase (MGMT), and retinoic acid receptor beta (RARB).76