Objective: Autophagy is a form Of physiological programmed cell death Which is, observable after hormonal withdrawal. In this study, the FM3A murine breast tumor cell line was treated with epirubicin alone and with medroxyprogesterone, acetate: (MPA) or tamoxifen, to determine if structural and kinetic signs, of autophagy may also Occur in an enhanced manner during epirubicin sensitization via hormonal, agents. Methods: One-week soft agar colony growth, 96-hour values of plating and pulse thymidine, labeling and electron microscopical examinations were performed following treatment with MPA and tamoxifen alone: or with epirubicin. Results. Tamoxifen. induced signs of autophagy, which was enhanced. when it was combined with M PA. Epirubicin also induced autophagy of secretory granules, which coalesced to form an intracytoplasmic lumen. Combining MPA with epirubicin enhanced the, formation of apoptotic blebs and chromatin fragmentation. When epirubicin was combined with tamoxifen, peculiar nuclear structures were formed. Conclusions: Hormonal agents may modulate anthracycline activity towards specific patterns in eliciting cell death, via autophagy and/or as yet unknown nucleolus-specific interactions. Copyright (C) 2002 S. Karger AG, Basel.