Retroviruses and Their Role in Cancer

Historically, retroviruses were first isolated and studied because they efficiently cause tumors in experimental and domestic animals (Rous, 1911; Ellerman and Bang, 1908). Work was particularly intense during the 1970s, under the “War on Cancer” and the Special Virus Cancer Program. Important discoveries from re-trovirology such as oncogenes and proto-oncogenes (Bishop, 1987) have had profound implications for understanding tumorigenesis, including for spontaneous human tumors. Retroviruses remain some of the best model systems for studying carcinogenesis in the whole organism, since they induce tumors with extremely high efficiency. The focus of this chapter will be retroviral carcinogenesis in small animal models. Major attention will be paid to nonacute retroviruses, since they induce disease through multiple steps, with analogies to non-virus-induced cancer as well.