FOLLOW UP ON SYSTEMIC INFLUENCE OF PARTIAL PRE-IRRADIATION ON UV-TUMORIGENESIS

Abstract— In a previous paper we presented experimental data which showed that partial pre-irradiation of a mouse enhanced subsequent UV-tumorigenesis in formerly unexposed skin areas: a systemic effect. In those experiments pre-irradiation was carried out up to the point where tumors started to appear in the pre-irradiated skin areas. Here we present the results of an experiment in which pre-irradiation was discontinued long before the appearance of tumors. The systemic effect induced by the pre-irradiation remained detectable, though-it was weaker than in the previous experiment. It is suspected that the observed systemic effect affects the initiation of tumors rather than the growth. A discussion is presented on how changes in initiation may best be detected, which may also prove to be useful for the design of other comparative studies on UV-tumorigenesis.