Aldehyde dehydrogenase 1: Its key role in cell physiology and oral carcinogenesis

Aldehyde dehydrogenase (ALDH), an aldehyde-metabolizing enzyme, is a cytosolic antioxidant. It performs many important physiological catalytic and non-catalytic functions in mammalian cells. Apart from physiological functions, like the biosynthesis of vital molecules, this NAD(P)+ substrate-dependent enzyme superfamily is primarily involved in catalyzing the oxidation of highly reactive exogenous and endogenous aldehydes to their respective carboxylic acids. Among ALDH isoenzymes, ALDH1 has gained much attention as a prominent stem cell marker, as it is associated with the maintenance of stemness and the differentiation of normal stem cells, in addition to involvement in oncogenic functions, like cell proliferation, anti-apoptosis and the reduction of oxidative stress in cancer stem cells (CSCs). In this context, the authors review the physiological functions of ALDH1 in normal cells, normal stem cells and CSCs, along with the discussion of the putative role of ALDH1 in oral carcinogenesis by commenting on its expression in normal oral mucosa cells, oral potentially malignant disorders (OPMDs), like leukoplakia and dysplastic lesions, and oral squamous cell carcinoma (OSCC).