ALDH2 and esophageal squamous cell carcinoma: Since 2009, there have been 2 genome-wide association (GWA) studies reporting functional variants that were significantly associated with susceptibility to esophageal cancer in the Japanese population.24,25 The first GWA study identified 4q21-23 and 12q24 as susceptibility loci, in which 2 functional variants in ADH1B and ALDH2 showed significant associations with ESCC risk (Table 3).24ADH1B and ALDH2 are crucial in the metabolism of alcohol.