The role of insulin-like growth factor binding protein-3 in the breast cancer cell response to DNA-damaging agents

Oncogene. 2014 Jan 2;33(1):85-96. doi: 10.1038/onc.2012.538. Epub 2012 Nov 26.

Abstract

Following exposure to radiation and chemotherapeutic agents, the epidermal growth factor receptor (EGFR) can modulate the repair of DNA double-strand breaks (DSB) by forming protein complexes that include the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs). This is one of the key mechanism by which tumors become resistant to DNA-damaging therapies. Our previous studies have shown that insulin-like growth factor binding protein-3 (IGFBP-3) is a substrate for DNA-PKcs, and can transactivate EGFR. We therefore questioned whether IGFBP-3 might interact with the EGFR-DNA-PK complex that regulates the DNA damage response. The aim of this study was to delineate the role of IGFBP-3 in the response of breast cancer cells to DSB-inducing chemotherapeutic agents. In the estrogen receptor-negative breast cancer cell lines MDA-MB-468 and Hs578T, which express IGFBP-3 highly, nuclear localization of EGFR and IGFBP-3 was enhanced by treatment with cytotoxic drugs etoposide or doxorubicin and reduced by the EGFR kinase inhibitor gefitinib. Enhanced association among IGFBP-3, EGFR and DNA-PKcs, following the exposure to DNA-damaging drugs was supported by both co-immunoprecipitation analysis and direct visualization by proximity ligation assay. The activation of DNA-PKcs at Ser2056, DNA repair as measured by a nonhomologous end-joining assay, and the increase in EGFR and DNA-PKcs interaction induced by DNA-damaging agents, were all decreased by IGFBP-3 silencing, suggesting that IGFBP-3 has an obligatory role in the DNA repair response to DNA-damaging therapy. In conclusion, IGFBP-3 co-translocation to the nucleus of breast cancer cells and its formation of a complex with DNA-PKcs and EGFR in response to DNA damage shows its potential involvement in the regulation of DNA repair. This suggests the possibility of a therapeutic approach for sensitizing breast cancer to chemo- or radiotherapy by targeting the DNA repair function of IGFBP-3.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus
  • Antineoplastic Agents / pharmacology*
  • Breast Neoplasms
  • Cell Line, Tumor
  • Cell Nucleus / metabolism
  • Cell Survival / drug effects
  • DNA Damage*
  • DNA Repair
  • DNA-Activated Protein Kinase / metabolism
  • Doxorubicin / pharmacology
  • ErbB Receptors / antagonists & inhibitors
  • ErbB Receptors / metabolism
  • Etoposide / pharmacology*
  • Female
  • Gefitinib
  • Humans
  • Insulin-Like Growth Factor Binding Protein 3 / physiology*
  • Membrane Microdomains / metabolism
  • Phosphorylation
  • Protein Kinase Inhibitors / pharmacology
  • Protein Processing, Post-Translational
  • Quinazolines / pharmacology

Substances

  • Antineoplastic Agents
  • IGFBP3 protein, human
  • Insulin-Like Growth Factor Binding Protein 3
  • Protein Kinase Inhibitors
  • Quinazolines
  • Etoposide
  • Doxorubicin
  • EGFR protein, human
  • ErbB Receptors
  • DNA-Activated Protein Kinase
  • Gefitinib