AHRR and lung cancer: Low methylation of specific CpG sites in AHRR (aryl-hydrocarbon receptor repressor) and F2RL3 (factor II receptor-like 3) has been associated with an increased risk of chronic diseases and lung cancer, as well as with the total mortality rate [11, 16, 19, 25], and could be used as biological markers for tobacco smoking [26, 27].