ZIP7-mediated intracellular zinc transport contributes to aberrant growth factor signaling in antihormone-resistant breast cancer Cells

Endocrinology. 2008 Oct;149(10):4912-20. doi: 10.1210/en.2008-0351. Epub 2008 Jun 26.


Antiestrogens such as tamoxifen are the mainstay of treatment for estrogen receptor-positive breast cancer. However, their effectiveness is limited by the development of endocrine resistance, allowing tumor regrowth and progression. Importantly, in vitro MCF7 cell models of acquired tamoxifen resistance (TamR cells) display an aggressive, invasive phenotype in which activation of epithelial growth factor receptor/IGF-I receptor/Src signaling plays a critical role. In this study, we report that TamR cells have increased levels of zinc and zinc transporter, ZIP7 [solute carrier family 39 (zinc transporter) member 7, also known as SLC39A7], resulting in an enhanced response to exogenous zinc, which is manifested as a greatly increased growth factor receptor activation, leading to increased growth and invasion. Removal of ZIP7, using small interfering RNA, destroys this activation of epithelial growth factor receptor/IGF-I receptor/Src signaling by reducing intracellular zinc levels. Similarly, it also blocks the activation of HER2, -3, and -4. These data suggest that intracellular zinc levels may be a critical factor in determining growth factor responses and that the targeting of zinc transporters may have novel therapeutic implications. We show that ZIP7 is a critical component in the redistribution of zinc from intracellular stores to the cytoplasm and, as such, is essential for the zinc-induced inhibition of phosphatases, which leads to activation of growth factor receptors. Removal of ZIP7 therefore offers a means through which zinc-induced activation of growth factor receptors may be effectively suppressed and provides a mechanism of targeting multiple growth factor pathways, increasing tumor kill, and preventing further development of resistance in breast cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / metabolism*
  • Breast Neoplasms / pathology
  • CSK Tyrosine-Protein Kinase
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm / physiology
  • ErbB Receptors / metabolism
  • Estrogen Receptor Modulators / pharmacology
  • Humans
  • Intercellular Signaling Peptides and Proteins / metabolism*
  • Protein-Tyrosine Kinases / metabolism
  • RNA, Small Interfering
  • Receptor, ErbB-2 / metabolism
  • Receptor, ErbB-4
  • Receptor, IGF Type 1 / metabolism
  • Signal Transduction / physiology*
  • Zinc / metabolism*
  • Zinc / pharmacology
  • src-Family Kinases


  • Cation Transport Proteins
  • Estrogen Receptor Modulators
  • Intercellular Signaling Peptides and Proteins
  • RNA, Small Interfering
  • SLC39A7 protein, human
  • ERBB2 protein, human
  • ERBB4 protein, human
  • ErbB Receptors
  • Protein-Tyrosine Kinases
  • Receptor, ErbB-2
  • Receptor, ErbB-4
  • Receptor, IGF Type 1
  • CSK Tyrosine-Protein Kinase
  • src-Family Kinases
  • CSK protein, human
  • Zinc