[Advancement of studies on ALDH1 as a universal marker of stem cells]

Aldehyde dehydrogenase 1 (ALDH1, ALDH1A1 or RALDH1), an enzyme responsible for the oxidation of intracellular aldehydes, was shown to have a function in the early differentiation of stem cells. Its activity shows promising potential as a universal marker for the identification and isolation of normal stem cells and cancer stem cells from multiple sources in a variety of tissue types. Herein, we review the available data reporting the utilization of ALDH1 activity as a means to identify and isolate normal stem cells and cancer stem cells (CSCs), and the potential diagnostic and therapeutic implications, with a special focus on the mammary gland and breast cancer. The research opportunity in this area of interest is emphasized.