"Hit and run" transformation leading to carcinogenesis.

Subgenomic fragments of herpes simplex virus and cytomegalovirus have been shown to transform rodent cells to a neoplastic phenotype in vitro. The transfected DNA does not persist long term in the transformed cells, and viral proteins, although transiently expressed, cannot be detected in the established cell lines. There is evidence that the transforming DNA fragments have mutagenic properties. It has not been established that the effects found in rodent cells can be observed in human cells. Although, the concept of "hit-and-run" transformation has been controversial for many years, it remains the only plausible explanation for the observations of neoplastic transformation, following in vitro transfection of herpesvirus and cytomegalovirus DNAs, which have been made by multiple laboratories over more than two decades.