Among the 137 study subjects (95 ESCC patients and 42 controls) with available information of two gene polymorphisms (ADH1B and ALDH2), we found that plasma MMP1 was significantly associated with the presence of ESCC after adjusting for the covariates including ADH1B and ALDH2 (Supplementary Table 2). This evidence concerns the gene MMP1 and esophageal squamous cell carcinoma.