HPV and skin carcinogenesis.

Epidemiological and biological studies provide several lines of evidence for the involvement of cutaneous beta human papillomaviruses (HPVs), together with ultraviolet (UV) radiation, in the development of cutaneous squamous cell carcinoma. These viruses appear to act with a hit-and-run mechanism, being necessary at an early stage of carcinogenesis and being dispensable for the maintenance of the malignant phenotype. Studies in experimental models show that beta HPVs, mainly via the E6 and E7 oncoproteins, are able to promote proliferation and to circumvent cellular stresses induced by UV radiation. These findings support a model of skin carcinogenesis in which beta HPV-infected keratinocytes remain alive despite the accumulation of UV-induced DNA mutations. In this manner, these cells become highly susceptible to progression towards malignancy. Thus, UV radiation is the main driver of skin cancer development, while beta HPVs act as facilitators of the accumulation of UV-induced DNA mutations.