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.
Hwang
Jung Jin
JJ
Institute for Innovative Cancer Research, College of Medicine, University of Ulsan, Asan Medical Center, Seoul, 138-736, Korea.
Kim
Ha Na
HN
Kim
Jean
J
Cho
Dong-Hyung
DH
Kim
Mi Joung
MJ
Kim
Yong-Sook
YS
Kim
Yunha
Y
Park
Sung-Jin
SJ
Koh
Jae-Young
JY
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