title: Phosphorothioate modification of the TLR9 ligand CpG ODN inhibits poly(I:C)-induced apoptosis of hepatocellular carcinoma by entry blockade.
abstract: Toll-like receptors (TLRs) play a crucial role in the innate immune response and subsequent induction of adaptive immune responses. Recently, it has been noted that TLRs on tumor cells are involved in tumor development, and several TLR agonists, such as the TLR3 agonist poly(I:C) and the TLR9 agonist CpG ODN, are being developed as vaccine adjuvants and cancer immunotherapeutics. In this study, we investigated whether combining poly(I:C) with a TLR9 agonist CpG ODN would result in a stronger anti-tumor effect on hepatocellular carcinoma cells (HCCs). Surprisingly, we found that simultaneous transfection of poly(I:C) and ODN M362 exhibited a lower pro-apoptotic effect on HCCs than transfection with poly(I:C) alone. Simultaneous co-transfection was accompanied by down-regulation of poly(I:C)-related innate receptors, pro-inflammatory cytokines and apoptotic genes induced by poly(I:C), indicating that ODN M362 blocked the activation of poly(I:C)-triggered intrinsic immune responses and cellular apoptosis. Further studies indicated that these effects were partly due to the phosphorothioate-modification of CpG ODN, which blocked the entry of poly(I:C) into tumor cells. This entry blockade was avoided by administering poly(I:C) after CpG ODN. Moreover, poly(I:C)-mediated pro-apoptotic effects were enhanced in vitro and in vivo by pre-treating HCC cells with CpG ODN. Our findings thus suggest that when combining poly(I:C) and CpG ODN for cancer therapy, these agents should be used in an alternating rather than simultaneous manner to avoid the blocking effect of phosphorothioate-modified TLR9 ligands.
authors.affiliation: Institute of Immunopharmacology & Immunotherapy, School of Pharmaceutical Sciences, Shandong University, China.
authors.forename: Yuyi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Institute of Immunopharmacology & Immunotherapy, School of Pharmaceutical Sciences, Shandong University, China.
authors.forename: Ang
authors.initials: A
authors.lastname: Lin
authors.affiliation: Institute of Immunopharmacology & Immunotherapy, School of Pharmaceutical Sciences, Shandong University, China.
authors.forename: Qiangjun
authors.initials: Q
authors.lastname: Sui
authors.affiliation: Institute of Immunopharmacology & Immunotherapy, School of Pharmaceutical Sciences, Shandong University, China.
authors.forename: Cai
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Institute of Immunopharmacology & Immunotherapy, School of Pharmaceutical Sciences, Shandong University, China.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Tian
authors.affiliation: Institute of Immunopharmacology & Immunotherapy, School of Pharmaceutical Sciences, Shandong University, China. Electronic address: zhangj65@sdu.edu.cn.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001692:Biological Transport; D019496:Cancer Vaccines / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056945:Hep G2 Cells; D006801:Humans; D008024:Ligands; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D008819:Mice, Nude; D009838:Oligodeoxyribonucleotides / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology; D054735:Phosphorothioate Oligonucleotides / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology; D011070:Poly I-C / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D013997:Time Factors; D051217:Toll-Like Receptor 9 / Q000819:agonists* / Q000378:metabolism; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
chemical_list: D019496:Cancer Vaccines; D008024:Ligands; D009838:Oligodeoxyribonucleotides; D054735:Phosphorothioate Oligonucleotides; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9; D011070:Poly I-C; C588272:ODN M362
keywords: CpG; Phosphorothioate; Poly(I:C); TLR; Tumor