ACTIVE CELL-DEATH INDUCED BY THE ANTIESTROGENS TAMOXIFEN AND ICI-164-384 IN HUMAN MAMMARY-CARCINOMA CELLS (MCF-7) IN CULTURE - THE ROLE OF AUTOPHAGY

Active cell death in hormone-dependent cells was studied using culture d human mammary carcinoma cells (MCF-7) treated with the anti-estrogen s (AEs) tamoxifen (TAM), 4-hydroxy-tamoxifen (OH-TAM) or ICI 164 384 ( 10(-8)-10(-5) M) as a model, The following results were obtained, (i) In untreated MCF-7 cells a wave of replication occurred in the first 5 days of culture, All three AEs caused a dose-dependent inhibition of cell replication, (ii) TAM and OH-TAM at 10(-5) Mj but not ICI 164 384 , caused lytic cell death (necrosis) within 24 h, which was not inhibi ted by estradiol (10(-9)-10(-6)M). (iii) Lower concentrations of TAM o r OH-TAM (up to 10(-6) M) or ICI 164 384 induced a more gradual appear ance of cell death beginning at day 3, This type of cell death was inh ibited by estradiol (10(-9) M), indicating its active nature, (iv) Nuc lei showed two distinct patterns of alteration: (a) apoptosis-like con densation and fragmentation of chromatin to crescent masses abutting t he nuclear envelope; (b) condensation of the chromatin to a single, py knotic mass in the center of the nucleus, detached from the nuclear en velope, Quantitative histological evaluation revealed the predominance of pyknosis, (v) Biochemical DNA analysis revealed that only a relati vely small amount of the total DNA was finally degraded into low molec ular weight fragments (20 kb send less), (vi) Active cell death, with both apoptotic and pyknotic nuclear morphology, was associated with ex tensive formation of autophagic vacuoles (AV), 3-Methyladenine, a know n inhibitor of AV formation, partially prevented cell death as detecte d by nuclear changes, (vii) ICI 164 384 was about 10 times more effect ive than TAM or OH-TAM at inhibiting DNA synthesis, but had equal pote ncy in inducing active cell death, It is concluded that AEs have anti- proliferative and anti-survival effects on MCF-7 human mammary cancer cells in culture, These two effects are under separate control because they differ by kinetics, dose dependence and sensitivity to the vario us AEs, Active cell death in MCF-7 cells seems to be initiated by auto phagy, in contrast to concepts of apoptosis, and thus corresponds to a utophagic/lysosomal or type II death as previously defined, This may b e important because of biochemical and molecular differences between t hese various subtypes of active cell death.