In vivo delivery of siRNA to immune cells by conjugation to a TLR9 agonist enhances antitumor immune responses

Nat Biotechnol. 2009 Oct;27(10):925-32. doi: 10.1038/nbt.1564. Epub 2009 Sep 13.


Efficient delivery of small interfering (si)RNA to specific cell populations in vivo remains a formidable challenge to its successful therapeutic application. We show that siRNA synthetically linked to a CpG oligonucleotide agonist of toll-like receptor (TLR)9 targets and silences genes in TLR9(+) myeloid cells and B cells, both of which are key components of the tumor microenvironment. When a CpG-conjugated siRNA that targets the immune suppressor gene Stat3 is injected in mice either locally at the tumor site or intravenously, it enters tumor-associated dendritic cells, macrophages and B cells. Silencing of Stat3 leads to activation of tumor-associated immune cells and ultimately to potent antitumor immune responses. Our findings demonstrate the potential of TLR agonist-siRNA conjugates for targeted gene silencing coupled with TLR stimulation and immune activation in the tumor microenvironment.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • B-Lymphocytes / physiology
  • Cell Line, Tumor
  • Chemokines / metabolism
  • DNA, Recombinant / genetics
  • Dendritic Cells / physiology
  • Flow Cytometry
  • Gene Silencing
  • Gene Transfer Techniques*
  • Immunity, Innate / drug effects
  • Macrophages / physiology
  • Mice
  • Myeloid Cells / physiology
  • Neoplasms / genetics
  • Neoplasms / immunology
  • Oligodeoxyribonucleotides / administration & dosage*
  • Oligodeoxyribonucleotides / chemistry
  • Oligodeoxyribonucleotides / genetics
  • Oligodeoxyribonucleotides / pharmacokinetics
  • RNA, Small Interfering / administration & dosage*
  • RNA, Small Interfering / chemistry
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / pharmacokinetics
  • STAT3 Transcription Factor / genetics*
  • Toll-Like Receptor 9 / agonists*


  • Chemokines
  • DNA, Recombinant
  • Oligodeoxyribonucleotides
  • RNA, Small Interfering
  • STAT3 Transcription Factor
  • Stat3 protein, mouse
  • Tlr9 protein, mouse
  • Toll-Like Receptor 9