title: ZIP7-mediated intracellular zinc transport contributes to aberrant growth factor signaling in antihormone-resistant breast cancer Cells.
abstract: 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.
authors.affiliation: Tenovus Centre for Cancer Research, Welsh School of Pharmacy, Cardiff University, Redwood Building, King Edward VIIth Avenue, Cardiff CF10 3NB, United Kingdom. taylorkm@cardiff.ac.uk
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Taylor
authors.forename: Petra
authors.initials: P
authors.lastname: Vichova
authors.forename: Nicola
authors.initials: N
authors.lastname: Jordan
authors.forename: Stephen
authors.initials: S
authors.lastname: Hiscox
authors.forename: Rhiannon
authors.initials: R
authors.lastname: Hendley
authors.forename: Robert I
authors.initials: RI
authors.lastname: Nicholson
mesh_terms: D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D000081247:CSK Tyrosine-Protein Kinase; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000502:physiology; D066246:ErbB Receptors / Q000378:metabolism; D020847:Estrogen Receptor Modulators / Q000494:pharmacology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D034741:RNA, Small Interfering; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D066247:Receptor, ErbB-4; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D015032:Zinc / Q000378:metabolism* / Q000494:pharmacology; D019061:src-Family Kinases
chemical_list: D000081247:CSK Tyrosine-Protein Kinase; D027682:Cation Transport Proteins; D066246:ErbB Receptors; D020847:Estrogen Receptor Modulators; D036341:Intercellular Signaling Peptides and Proteins; D011505:Protein-Tyrosine Kinases; D034741:RNA, Small Interfering; D018719:Erb-b2 Receptor Tyrosine Kinases; D066247:Receptor, ErbB-4; D017526:Receptor, IGF Type 1; D015032:Zinc; D019061:src-Family Kinases; C102227:SLC39A7 protein, human; C508053:ERBB2 protein, human; C587689:ERBB4 protein, human; C000631346:CSK protein, human