Normal mucosae of low-risk individuals (healthy people without past exposure to lifestyle risk factors) had FGF5 methylation levels of 0.6–2.6%, those of intermediate-risk individuals (healthy people with the lifestyle risk factors) had levels of 2.6–6.1%, and those of high-risk individuals (ESCC patients with past exposure to lifestyle risk factors) had methylation levels of 4.2–9.4% (Fig. 5A,B). Here, FGF5 is linked to esophageal squamous cell carcinoma.