Mechanisms of retrovirus-induced oncogenesis.

Retroviruses are implicated in a series of human and animal tumours such as leukaemias, mammary tumours or skin cancer. The mechanism that they use to induce tumour formation varies. Insertional mutagenesis is a common mechanism in rodent, feline and avian retroviruses, where the retrovirus integrates into the host genome and affects the transcription of the neighbouring genes. Cloning of these affected genes led to identification of a series of oncogenes that play a significant role in the induction of human neoplasms. Retrovirus insertion also serves as a model to identify collaborating oncogenes. Human retroviruses use different, more complex mechanisms contributing to oncogenesis. Studies of the propagation and induction mechanisms used by retroviruses have given insight to the understanding of oncogenesis.