Role of viruses in the development of squamous cell cancer and melanoma

In this chapter, the evidence for the role of human papilloma virus (HPV) in the pathogenesis of squamous cell cancer of the skin will be reviewed. Considerable dispute exists questioning the etiological role of HPV. This is due to the low copy number ofHPV DNA in skin cancers and additional cofactors such as UV exposure, immunosuppression, light skin color and hyperproliferative skin disease as well as the genetic background of the host. These additional cofactors are probably required because of the weak transforming activity of cutaneous HPV types in contrast to high-risk genital HPV strains. On a different note, the involvement of viruses in the etiology of melanoma has only recently been suggested. Melanoma-associated retrovirus (MelARV) has been detected in mice and men and was shown to subvert immunosurveillance besides insertional mutagenesis. The state of the art of viral participation in melanomagenesis will be discussed.