siRNA-induced immunostimulation through TLR7 promotes antitumoral activity against HPV-driven tumors in vivo

Immunol Cell Biol. 2012 Feb;90(2):187-96. doi: 10.1038/icb.2011.19. Epub 2011 Mar 22.

Abstract

Oncogene-specific downregulation mediated by RNA interference (RNAi) is a promising avenue for cancer therapy. In addition to specific gene silencing, in vivo RNAi treatment with short interfering RNAs (siRNAs) can initiate immune activation through innate immune receptors including Toll-like receptors, (TLRs) 7 and 8. Two recent studies have shown that activation of innate immunity by addition of tri-phosphate motifs to oncogene-specific siRNAs, or by co-treatment with CpG oligos, can potentiate siRNA antitumor effects. To date, there are no reports on applying such approach against human papillomavirus (HPV)-driven cancers. Here, we characterized the antitumor effects of non-modified siRNAs that can target a specific oncogene and/or recruit the innate immune system against HPV-driven tumors. Following the characterization of silencing efficacy and TLR7 immunostimulatory potential of 15 siRNAs targeting the HPV type 16 E6/E7 oncogenes, we identified a bifunctional siRNA sequence that displayed both potent gene silencing and active immunostimulation effect. In vivo systemic administration of this siRNA resulted in reduced growth of established TC-1 tumors in C57BL/6 mice. Ablation of TLR7 recruitment via 2'O-methyl modification of the oligo backbone reduced these antitumor effects. Further, a highly immunostimulatory, but non-HPV targeting siRNA was also able to exert antitumoral effects although for less prolonged time compared with the bifunctional siRNA. Collectively, our work demonstrates for the first time that siRNA-induced immunostimulation can have antitumoral effects against HPV-driven tumors in vivo, even independent of gene silencing efficacy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Female
  • Human papillomavirus 16 / genetics*
  • Human papillomavirus 16 / immunology
  • Humans
  • Immunization / methods
  • Male
  • Membrane Glycoproteins / genetics*
  • Membrane Glycoproteins / immunology
  • Membrane Glycoproteins / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Oncogene Proteins, Viral / genetics
  • Papillomavirus E7 Proteins / genetics
  • Papillomavirus Infections / genetics
  • Papillomavirus Infections / immunology
  • RNA Interference
  • RNA, Small Interfering / administration & dosage*
  • RNA, Small Interfering / genetics
  • Repressor Proteins / genetics
  • Toll-Like Receptor 7 / genetics*
  • Toll-Like Receptor 7 / immunology
  • Toll-Like Receptor 7 / metabolism
  • Uterine Cervical Neoplasms / genetics
  • Uterine Cervical Neoplasms / immunology*
  • Uterine Cervical Neoplasms / virology

Substances

  • E6 protein, Human papillomavirus type 16
  • Membrane Glycoproteins
  • Oncogene Proteins, Viral
  • Papillomavirus E7 Proteins
  • RNA, Small Interfering
  • Repressor Proteins
  • Tlr7 protein, mouse
  • Toll-Like Receptor 7
  • oncogene protein E7, Human papillomavirus type 16