Historic milestones in cancer virology.

Abstract

T HIS ARTICLE deals with the development of cancer virology as an important scientific discipline for understanding not only the relationship between viruses and human cancer but also for probing the molecular biology of eukaryotic cells. The term “tumor virus” or “oncogenic virus” is used to describe those viruses that are able to transform cells in culture from a normal into a malignant-like phenotype, or that are able to induce tumors when inoculated into experimental animals. These viruses form two classes, the DNA tumor viruses and the retroviruses, which have DNA and RNA respectively as their genetic material. Although some retroviruses have no known oncogenic properties, these are classified as tumor viruses for the purposes of this article because they share many other properties with tumor viruses. Table 1 lists the groups of known DNA tumor viruses. The major groups are (1) the papovaviruses, which include the well-studied simian virus 40 (SV40), polyomavirus, and the less well-studied human BK virus (BKV) and JV virus (JCV); (2) papillomaviruses, which include 5-l 0 human papillomaviruses (HPV) and a variety of animal papillomaviruses (papillomaviruses are usually classified under the papovavirus group); (3) the adenoviruses (Ad), of which there are 35 human serotypes (31 recognized) forming 5 distinct groups and a large variety of animal types; and (4) the herpesviruses, which include human herpes simplex types 1 and 2 (HSV-1, HSV-2), cytomegalovirus (CMV), and the Epstein-Barr virus (EBV), as well as a variety of animal herpesviruses. The polyoma-type papovaviruses and papillomaviruses have circular superhelical DNA genomes of 3 x lo6 and 5 x lo6 daltons, respectively. The Ads and herpesviruses have linear duplex DNA genomes of 20-25 x IO6 and about l-l .5 x lo* daltons, respectively. Table 2 lists the different retroviruses. Retroviruses have been associated with virtually every species except definitively with man, and can be categorized according to several criteria. First, retroviruses may be endogenous, i.e., a normal component of the genetic material of an animal, or they may be infectious exogenous viruses