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Tamoxifen Subcellular Localization; Observation of Cell-Specific Cytotoxicity Enhancement by Inhibition of Mitochondrial ETC Complexes I and III

Authors

  • Theodossis Athanassios Theodossiou,

    Corresponding author
    1. Institute of Physical Chemistry, NCSR “Demokritos,” Patriarchou Gregoriou & Neapoleos, Attiki, Greece
      Corresponding author email: theo@chem.demokritos.gr (Theodossis Athanassios Theodossiou)
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  • Konstantina Yannakopoulou,

    1. Institute of Physical Chemistry, NCSR “Demokritos,” Patriarchou Gregoriou & Neapoleos, Attiki, Greece
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  • Chrysie Aggelidou,

    1. Institute of Physical Chemistry, NCSR “Demokritos,” Patriarchou Gregoriou & Neapoleos, Attiki, Greece
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  • John Stephen Hothersall

    1. Department of Pharmacology, Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, SP, Brazil
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Corresponding author email: theo@chem.demokritos.gr (Theodossis Athanassios Theodossiou)

ABSTRACT

Recently, a nongenomic cytotoxic component of the chemotherapeutic agent tamoxifen (TAM) has been identified that predominantly triggers mitochondrial events. The present study delineates the intracellular fate of TAM and studies its interaction with a spectrum of cell homeostasis modulators primarily relevant to mitochondria. The subcellular localization of TAM was assessed by confocal fluorescence microscopy. The effect of the modulators on TAM cytotoxicity was assessed by standard MTT assays. Our findings show that in estrogen receptor positive MCF7 breast adenocarcinoma cells and DU145 human prostate cancer cells, TAM largely accumulates in the mitochondria and endoplasmic reticulum, but not lysosomes. Our results further demonstrate that in MCF7, but not in DU145 cells, mitochondrial electron transport chain complex I and III inhibitors exacerbate TAM toxicity with an order of potency of myxothiazol ≥ stigmatellin > rotenone > antimycin A, suggesting a cell-specific cytotoxic interplay between mitochondrial complex I and III function and TAM action.

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