The 1984 Walter Hubert lecture. Activation of transforming genes in neoplasms.

Cellular oncogenes have been identified by the biological activity of tumour DNAs in transfection assays and/or by homology to the transforming genes of retroviruses. In some tumours, the biological activity, organization or expression of these genes is altered, suggesting that such alterations contribute to the development of neoplastic disease. Experiments leading to the identification of cellular oncogenes are reviewed and our current understanding of the mechanisms by which they induce transformation of cells in culture and may contribute to the pathogenesis of neoplasms in vivo is discussed.