Viral Carcinogenesis

Abstract

The connection of viruses with cancer is not surprising, since the biology of viruses is rooted deeply in the life of the cells they parasitize. This is shown, for instance, by the process of bacterial lysogeny. In this process, the DNA of a temperate bacteriophage enters the cell, becomes integrated in its genetic material, and becomes equivalent to a set of cellular genes. Whereas most of the integrated viral genes are inactive, some express their functions and thus cause changes of attributes of the cell, which persist and are transmitted to all the descendants of the parasitized cell. The result is almost as if some genes of the cells were changed by a mutagenic agent. For the investigator interested in the mechanism of viral carcinogenesis, the changes of the genetic properties of a cell caused by a virus are much more interesting than those caused by a mutagenic agent. The reason is simple: since a mutagenic agent can affect any one of the several million cellular genes, it is almost impossible to trace the phenotypic change it produces in the cell to the gene responsible for it. In contrast, a virus brings into the cell a small number of genes and it is therefore far simpler to identify the particular viral gene responsible for a cellular change.