Aging, Skin and Cancer
There’s a very interesting paper in this month’s issue of the journal Developmental Cell, based on research conducted at the Oregon Health & Science University in Portland, Baylor College of Medicine in Houston and Leiden in the Netherlands.
The investigators have found a pathway through which a gene’s over-expression causes stem cells in the skin to switch from creating hair follicles to creating sebaceous glands. This discovery may not only provide us with new ways of treating hair loss and oily skin, but it may help us to prevent and treat some cancers.
Skin cells turn over very quickly: just think how fast a graze gets covered over. Epidermal stem cells give rise to the outer layer of the skin that serves as a barrier for the body, as well as generating the follicles that produce hairs and sebaceous glands. These glands produce oils to lubricate the skin. In aged skin, a protein called Smad7 is overproduced, which triggers hair loss and sebaceous gland growth.
This is the first study definitively to link Smad7 over-expression and the pathological changes that occur in aged skin.
Here’s the twist: Smad7 shuts down signaling of another group of genes called Wnt. It binds to a Wnt signaling protein known as Beta-catenin and degrades it with an enzyme called Smurf2. (I don’t known why they decided to call it’s call it Smurf: it looks like ponderous chemical humor to me!) Wnt signaling is critical for organ development, but if Wnt signaling is too active, it also causes cancer.
Enhanced Beta-catenin signaling contributes to many types of cancer, including colon, lung and brain. Perhaps inducing over-expression of Smad7 or delivery of Smad7 directly to tumor cells would provide a therapeutic approach because of the boost in Beta-catenin degradation.
And finally, impaired Beta-catenin signaling contributes to neurodegeneration, such as that found in Alzheimer’s and Parkinson’s diseases, retinal degeneration, some bone density defects and aging. For these diseases, blocking Smad7-mediated Beta-catenin degradation may offer a therapeutic approach.