ALDH2 and breast cancer: This protein encoded by gene ALDH2(Aldehyde dehydrogenase 2 family member) is classified within the aldehyde dehydrogenase protein family, which plays a key role as the second enzyme in the primary oxidative pathway of alcohol metabolism [44].Ugai T et al. [45] found that functional ALDH2 polymorphisms are correlated to the BC risks, and Lys/Lys genotypes confer susceptibility to BC risk in Asian women, especially for ER-positive, PR-positive, and HER2-negative tumor types.