Chronic expression of p16INK4a in the epidermis induces Wnt-mediated hyperplasia and promotes tumor initiation (2)

In this study we examine the outcomes of p16INK4a activation in the adult epidermis. We found that prolonged expression of p16INK4a induces epidermal hyperplasia and dysplasia. We also found that continued p16INK4a expression increased the number of epidermal papillomas that developed after carcinogen treatment. Profling of p16INK4a- expressing cells showed elevated levels of Wnt-pathway ligands and targets, and pharmacologic or genetic Wnt inhibition suppressed p16-induced hyperplasia. In human actinic keratosis, a precursor of squamous cell carcinoma, p16-expressing cells are typically found adjacent to dividing cells, consistent with paracrine interaction. These findings reveal that in addition to its cell-autonomous role in blocking cell proliferation, p16 can induce hyperplasia through paracrine stimulation, suggesting that its activity contributes to the formation of early premalignant epidermal lesions. Expression profiles of papillomas excised from K5-rtTA/tet-p16 and tet-p16 control mice.