title: siRNA-induced immunostimulation through TLR7 promotes antitumoral activity against HPV-driven tumors in vivo.
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.
authors.affiliation: The University of Queensland Diamantina Institute, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
authors.forename: Norliana
authors.initials: N
authors.lastname: Khairuddin
authors.forename: Michael P
authors.initials: MP
authors.lastname: Gantier
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Blake
authors.forename: Sherry Y
authors.initials: SY
authors.lastname: Wu
authors.forename: Mark A
authors.initials: MA
authors.lastname: Behlke
authors.forename: Bryan R G
authors.initials: BR
authors.lastname: Williams
authors.forename: Nigel A J
authors.initials: NA
authors.lastname: McMillan
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005260:Female; D052162:Human papillomavirus 16 / Q000235:genetics* / Q000276:immunology; D006801:Humans; D007114:Immunization / Q000379:methods; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009856:Oncogene Proteins, Viral / Q000235:genetics; D050725:Papillomavirus E7 Proteins / Q000235:genetics; D030361:Papillomavirus Infections / Q000235:genetics / Q000276:immunology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics; D051199:Toll-Like Receptor 7 / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000276:immunology* / Q000821:virology
chemical_list: C068651:E6 protein, Human papillomavirus type 16; D008562:Membrane Glycoproteins; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D034741:RNA, Small Interfering; D012097:Repressor Proteins; C477038:Tlr7 protein, mouse; D051199:Toll-Like Receptor 7; C059731:oncogene protein E7, Human papillomavirus type 16