Efficient suppression of secretory clusterin levels by polymer-siRNA nanocomplexes enhances ionizing radiation lethality in human MCF-7 breast cancer cells in vitro

Damon Sutton, Saejeong Kim, Xintao Shuai, Konstantin Leskov, Joao T. Marques, Bryan R G Williams, David A. Boothman, Jinming Gao

Research output: Contribution to journalArticle

43 Scopus citations


Small interfering RNA molecules (siRNA) hold great promise to specifically target cytoprotective factors to enhance cancer therapy. Like antisense RNA strategies, however, the use of siRNA is limited because of in vivo instability. As a first step to overcome delivery issues, a series of graft copolymers of polyethylene glycol and polyethylenimine (PEI-g-PEG) were synthesized and investigated as nontoxic carriers for delivery of siRNA targeting the signaling peptide of secretory clusterin (sCLU), a prosurvival factor that protects cells from ionizing radiation (IR) injury, as well as chemotherapeutic agents. Three copolymers with different PEG grafting densities were tested for their abilities to bind and form nanocomplexes with siRNA. A copolymer composed of 10 PEG grafts (2 kDa each) per PEI polymer (2k10 copolymer) gave the highest binding affinity to siRNA by ethidium bromide exclusion assays, and had the smallest nanocomplex size (115 ± 13 nm diameter). In human breast cancer MCF-7 cells, 2k10-siRNA-sCLU nanocomplexes suppressed both basal as well as IR-induced sCLU protein expression, which led to an over 3-fold increase in IR-induced lethality over 2k10-siRNA scrambled controls. In summary, this study demonstrates the proof-of-principle in using nanoparticle-mediated delivery of specific siRNAs to enhance the lethality of IR exposure in vitro, opening the door for siRNA-mediated knockdown of specific cytoprotective factors, such as DNA repair, anti-apoptotic, free radical scavenging, and many other proteins.

Original languageEnglish (US)
Pages (from-to)155-162
Number of pages8
JournalInternational Journal of Nanomedicine
Issue number2
StatePublished - Dec 1 2006



  • Cancer radiotherapy
  • Nanomedicine
  • Polyethylenimine
  • Secretory clusterin
  • siRNA delivery

ASJC Scopus subject areas

  • Biophysics
  • Bioengineering
  • Biomaterials
  • Pharmaceutical Science
  • Drug Discovery
  • Organic Chemistry

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