[Recent knowledge of the biochemical significance of proto-oncogenes, their activation and development of tumors].

In each cytoblast of mammals about 30 protooncogenes are present which during the embryonic, the fetal and the postnatal development, respectively, in certain cell types may temporarily or permanently be used for the formation of certain proteins. A part of these proteins is of importance for the furthering of the division (DNA-replication) and the differentiation of the cells. According to the qualities in the proteins formed by protooncogenes the protein kinases, the GTP binding proteins and the DNA binding proteins are differentiated. Under the influence of carcinogens and of cocarcinogens several protooncogenes are changed in their structure and displaced, respectively, within certain chromosomes. Thus they are transduced into oncogenes and evoke an increased formation of transforming proteins which initiate a dysregulation of the transcription in the nucleus. Several aspects of the activation of protooncogenes, of the development of tumours as well as of the origination of tumours by recessive mutation are described.