Human Papillomaviruses and Non-melanoma Skin Cancer

Human papillomaviruses (HPVs) infect the squamous epithelium and can induce benign and malignant lesions. To date, more than 200 different HPV types have been identified and classified into five genera, α, β, γ, μ, and ν. While high-risk α mucosal HPVs have a well-established role in cervical carcinoma and a significant percentage of other anogenital tract and oral carcinomas, the biology of the cutaneous β HPVs and their contribution to non-melanoma skin cancer (NMSC) has been less studied. Although the association of β HPV infection with NMSC in patients with a rare, genetically determined condition, epidermodysplasia verruciformis has been well established, the role of β HPV infection with NMSC in the normal population remains controversial. In stark contrast to α HPV-associated cancers, the presence of the β HPV genome does not appear to be mandatory for the maintenance of the malignant phenotype. Moreover, the mechanism of action of the β HPV E6 and E7 oncoproteins differs from the β HPV oncoproteins.