Viruses and human cancer.

Epstein-Barr virus (EBV), hepatitis B virus (HBV), HTLV-I and some human papillomaviruses (HPVs) appear to contribute to the development of a large proportion of certain human cancers. Although the epidemiological evidence linking infection with these viruses to malignancies is generally convincing, only for the HPVs have experimental systems indicated a clear role for some of the HPV encoded genes in tumour cell growth. In these cases, molecular analysis is revealing the mechanisms by which the virally encoded oncogenes function to perturb the normal regulation of cell growth. For HTLV-I, EBV and HBV the mechanism by which the viruses contribute to tumour cell growth is obscure, even though much has been learned about cell transformation in culture by these viruses. A detailed understanding of the mechanism of oncogenesis will be required to design therapeutic drugs for the treatment of these cancers. Prophylactic vaccination resulting in prevention of infection may be an effective approach to reduce the incidence of some of these common cancers.