More recently, increasing evidence supports the suggestion that dysregulated epigenetic control through DNA methylation is important for radio‐resistance of cancer cells.13 The early interest in the effects of DNA methylation dating back to 2002, Kim et al14 found that aberrant methylation of multiple CpG dinucleotides of the ataxia telangiectasia mutated (ATM) gene led to radio‐resistance in a human colorectal tumor cell line. Here, ATM is linked to cancer.