[The effect of caffeine on the development of melanotic tumours in Drosophila (author's transl)].

Caffeine, added to the nutrient medium of strain cl tu48-a larvae which can develop spontaneous melanotic tumours, produces a double effect: a toxic effect and an inhibitory effect on tumorigenesis. The toxic effect manifests itself especially if young larvae are treated, and is observed as an increase in their mortality. The effect of caffeine on tumorigenesis is only seen if it is administered during the 2nd and 3rd day of the larval life. Outside of this period, or if caffeine is only applied during a part of the period, it exerts no influence on tumorigenesis. The effect on tumorigenesis consists of a decrease in the frequency of tumourous individuals. In individuals who have developed at least one tumour, caffeine does not modify the probability of the development of other tumours. Its action thus, is at the individual scale and not at that of the tumour. The time during which larvae are sensitive to caffeine indicates that the effect must intervene before the appearance of the first tumour cells.