[Cancers, oncogenesis and oncogenes].

The carcinogenic transformation depends on the presence of particular genes, the oncogenes, which are, as a matter of fact, normal cellular genes. The oncogenic retro-viruses are mosaic genomes, transducing oncogenes in the infected cells. These genes are expressed: the product has an activity of protein kinase. The expression is increased in the transformed cells, because the oncogenes are either linked to strong viral promoters in the oncogenic viruses, or translocated in the vicinity of immunoglobulin genes in the case of Burkitt lymphoma. Moreover, there is some modifications (punctual mutations or deletions) of the primary sequence of the protein.