Loss of epidermal hypoxia-inducible factor-1α blocks UVB-induced tumorigenesis by affecting DNA repair capacity and oxidative stress.

Hypoxia-inducible factor-1α (HIF-1α) is constitutively expressed in mouse and human epidermis. It plays a crucial role in skin physiology including the response of keratinocytes to ultraviolet (UV) radiation. However, little information is available about its role in photocarcinogenesis. Using a multistage model of UVB radiation-induced skin cancer, we show that the knockout of Hif-1α in the epidermis prevents tumorigenesis, but at the same time triggers the formation of hyperkeratotic plaques. Our results indicate that the absence of oncogenic transformation in Hif-1α-ablated mice is related to increased DNA repair in keratinocytes, while the formation of hyperkeratotic plaques is caused by an increase in the levels of reactive oxygen species. Indeed, impairing the DNA repair machinery by ablating xeroderma pigmentosum C restored the UVB-induced neoplastic transformation of Hif-1α-ablated keratinocytes, while the development of hyperkeratotic plaques was blocked by chronic antioxidant treatment. We conclude that HIF-1α plays a pro-carcinogenic role in UVB-induced tumorigenesis.