Aquaporin-3 linked to cancer
Aquaporin-3 (AQP3) is a protein that facilitates the transport of moisture and glycerol. In other words, it helps keep the skin moist. Cosmetic companies have noticed the correlation between AQP3 and moisture content in the skin and market products with ingredients that boost "the expression" of AQP3.
Dr Verkman found, in an experiment on mice, a correlation between AQP3 formation in the epidermis and tumor cells. In his paper he says: "AQP expression in tumor cells has been found to increase their migration, invasiveness and metastatic potential." And this is his conclusion: "Given the relationship between epidermal AQP3 expression and tumor cell proliferation, caution seems warranted in the use of cosmetics containing ingredients that increase epidermal AQP3 expression."
So the main question for me is what are these AQP3 boosters? If we know what they are then we'll know which products to avoid. Verkman refers to a study carried out on behalf of Christian Dior that used a plant extract called extract of ajuga turkestanica as the hydrating (AQP3 boosting) agent. I have also seen references elsewhere citing retinoic acid and glycolic as AQP3 boosting. It is tempting to conclude that any product that claims it can boost moisture by increasing AQP3 activity is to be avoided.
The problem is that I have yet to come across a cosmetic that markets itself as increasing AQP3, although there are plenty that claim to hydrate. Hopefully, more information around this story will emerge in the coming days. I'll update as I come across anything that sheds some more light.
*A cautionary note on cosmetics containing ingredients that increase aquaporin-3 expression. Experimental Dermatology 2008; 00: 000–000