In a variety of cancers, including lung cancer (Moreb et al., 2008; Wei et al., 2015), breast cancer (Douville et al., 2009), and colorectal cancer (Chen et al., 2015), the enzyme aldehyde dehydrogenase 3B1 (ALDH3B1), which catalyzes the oxidation of aldehydes to the appropriate carboxylic acids, has been discovered to be important cancer stem cell marker. The gene discussed is ALDH3B1; the disease is colorectal cancer.