ALDH1A1(Aldehyde dehydrogenase family 1 member A1 ),also named as ALDC,ALDH1 and PUMB1,belongs to the aldehyde dehydrogenase family. The ALDH1A1 gene encodes a liver cytosolic isoform of acetaldehyde dehydrogenase,an enzyme involved in the major pathway of alcohol metabolism after alcohol dehydrogenase. ALDH1A1 plays a critical role in protection against oxidative stress-induced cytotoxicity in lens epithelial cells. And it is important for multiple biological activities including drug resistance,cell differentiation,and oxidative stress response. As a novel cancer stem cell marker,ALDH1A1 can be used for tumors whose corresponding normal tissues express ALDH1A1 in relatively restricted or limited levels such as breast,lung,ovarian or colon cancer.