MTHFR and esophageal squamous cell carcinoma: For example, after adjusting for the aforementioned seven potential confounders, the combinations of ALDH 2 2*2/1*2 and MTHFR TT/TC genotypes were associated with significantly increased risks for BCH, ESCD, and ESCC compared to patients with the 1*1 ALDH 2 and CC MTHFR C677T genotype.