A cautionary note on cosmetics containing ingredients that increase aquaporin-3 expression.

Aquaporin-3 (AQP3) is a membrane transport protein that facilitates water and glycerol transport across cell plasma membranes in the basal layer of keratinocytes in normal skin. Motivated by a relation between AQP3 expression and skin water content, several companies have marketed cosmetics containing ingredients that increase AQP3 expression. However, caution seems warranted in targeting AQP3 to increase skin moisturization based on a recently discovered association in mice between epidermal AQP3 expression and skin tumor formation.