Zinc(II) ion mediates tamoxifen-induced autophagy and cell death in MCF-7 breast cancer cell line.
Treatment of MCF-7 cells with tamoxifen induced vacuole formation and cell death. Levels of the autophagy marker, microtubule-associated protein light chain 3 (LC3)-II also increased, and GFP-LC3 accumulated in and around vacuoles in MCF-7 cells exposed to tamoxifen, indicating that autophagy is involved in tamoxifen-induced changes. Live-cell confocal microscopy with FluoZin-3 staining and transmission electron microscopy with autometallographic staining revealed that labile zinc(II) ion (Zn(2+)) accumulated in most acidic LC3(+) autophagic vacuoles (AVs). Chelation of Zn(2+) with N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN) blocked the increase in phospho-Erk and LC3-II levels, and attenuated AV formation and cell death. Conversely, the addition of ZnCl(2) markedly potentiated tamoxifen-induced extracellular signal-regulated kinase (Erk) activation, autophagy and cell death, indicating that Zn(2+) has an important role in these events. Tamoxifen-induced death was accompanied by increased oxidative stress and lysosomal membrane permeabilization (LMP) represented as release of lysosomal cathepsins into cytosol. Treatment with the antioxidant N-acetyl-L-cysteine (NAC) blunted the increase in Zn(2+) levels and reduced LC3-II conversion, cathepsin D release and cell death induced by tamoxifen. And cathepsin inhibitors attenuated cell death, indicating that LMP contributes to tamoxifen-induced cell death. Moreover, TPEN blocked tamoxifen-induced cathepsin D release and increase in oxidative stress. The present results indicate that Zn(2+) contributes to tamoxifen-induced autophagic cell death via increase in oxidative stress and induction of LMP.
Institute for Innovative Cancer Research, College of Medicine, University of Ulsan, Asan Medical Center, Seoul, 138-736, Korea.
Jung Jin
JJ
Hwang
Ha Na
HN
Kim
Jean
J
Kim
Dong-Hyung
DH
Cho
Mi Joung
MJ
Kim
Yong-Sook
YS
Kim
Yunha
Y
Kim
Sung-Jin
SJ
Park
Jae-Young
JY
Koh
D001343:Autophagy / Q000187:drug effects* / Q000502:physiology; D001943:Breast Neoplasms / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D005260:Female; D006801:Humans; D008247:Lysosomes / Q000502:physiology; D018384:Oxidative Stress / Q000502:physiology; D010539:Permeability; D011083:Polycyclic Compounds; D013629:Tamoxifen / Q000494:pharmacology*; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism; D019287:Zinc Sulfate / Q000494:pharmacology*
D002614:Chelating Agents; D005029:Ethylenediamines; C451182:FluoZin-3; D011083:Polycyclic Compounds; D013629:Tamoxifen; D019287:Zinc Sulfate; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine