3, 4-dihydroxyphenylacetic acid (DOPAC) is a neuronal metabolite of dopamine (DA). DA undergoes monoamine oxidase-catalyzed oxidative deamination to 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is metabolized primarily to 3,4-dihydroxyphenylacetic acid (DOPAC) via aldehyde dehydrogenase, ALDH2. DOPAC exhibits the antiproliferative effect in colon cancer cells. In addition, DOPAC enhances not only the total ALDH activity but also the gene expression of ALDH1A1, ALDH2, and ALDH3A1 in a concentration-dependent manner. The pretreatment of DOPAC completely protects the cells from the acetaldehyde-induced cytotoxicity, thus DOPAC acts as a potential ALDH inducer to prevent the alcohol-induced abnormal reaction.