RADIATION-INDUCED MICRONUCLEI FORMATION IN HUMAN BREAST-CANCER CELLS - DEPENDENCE ON SERUM AND CELL-CYCLE DISTRIBUTION

Micronuclei (MN) formation was defined as a form of radiation-induced damage in MCF-7 cells. MN appeared post-mitosis and were scored in bi- nucleated cells of cytochalasin B treated cultures. MN were surrounded by an envelope composed of inner and outer membranes, and contained f ragmented chromosomes. However, typical features of apoptosis, such as chromatin margination or condensation were not observed. Reducing ser um concentration resulted in a decreased MN formation, suggesting that serum factors directly affected MN formation and/or that serum deplet ion decreased the availability of radiation sensitive MN-forming cells for mitosis. Irradiation of G(1) and S phase enriched populations rev ealed that S phase cells were more prone to MN formation than G(1) cel ls. Radiation-induced chromosomal aberration can therefore be modulate d by altering serum level and cell cycle distribution. (C) 1997 Academ ic Press.