Oncogenic Viruses, Cellular Transformation and Human Cancers

It has been a century since the initial discovery of the possible link between viruses and tumors. During the past century, extensive studies have been conducted to understand the relationship between viruses and cancers. The early studies were focused on tumor viruses that do not cause cancers in their natural hosts. These studies provided the basis for the subsequent studies on the six known human oncogenic viruses. These human oncogenic viruses, which include hepatitis B virus, hepatitis C virus, human papillomavirus, Epstein-Barr virus, Kaposi’s sarcoma-associated herpesvirus, and human T-cell leukemia virus 1 are associated with nearly 20% of the human cancer cases. In this chapter, we review the historical aspects of oncogenic virus research, human oncogenic viruses, and the molecular mechanisms of cellular transformation by viruses.