[New knowledge on the mechanism of action of oncogenes, carcinogens and anticarcinogens].

In the development of a tumour a multistep process is existing, in which after activation of a cellular oncogen and after efficacy of a viral oncogenat first an avalanche-like increase of transforming, excluding the regulation of cell division proteins takes place. In many forms of tumours the transforming proteins possess the property of protein kinases and phosphorylize proteins situated in the area of the cell membrane. In some forms of tumours an enrichment in the area of the cell nucleus takes place. Secondarily, in the tumour cells frequently other oncogens are activated and an activation of further genes for the formation of growth factors or of proteins of the histocompatibility complex, respectively, occurs. Some transforming proteins themselves possess the properties of growth factors and of receptors, respectively, for the binding of such ones. Cocarcinogens activate the protein kinase C, e.g. the phorbol esters. Anticarcinogens influence the transcription, e.g. the vitamin A and the 1,25-dihydroxyvitamin D3. Vitamin A and analogous compounds increases the functional capacity of the immune defense.