RNA interference-mediated silencing of Foxo3 in antigen-presenting cells as a strategy for the enhancement of DNA vaccine potency.
The transcription factor Forkhead box O3 (Foxo3) has a critical role in suppressing the expansion of antigen-specific effector T-cell populations; hence, Foxo3 is a potential target for enhancing the antitumor immunity of cancer vaccines. In this report, we evaluated the potential of RNA interference (RNAi)-mediated silencing of Foxo3 in antigen-presenting cells as an adjuvant for HER2/neu DNA cancer vaccines. Bicistronic plasmids expressing the N-terminal extracellular domain of human HER-2/neu and the Foxo3 short hairpin RNA (hN'-neu-Foxo3 shRNA) or the scrambled control (hN'-neu-scramble shRNA) were subcutaneously injected into mice by gene gun administration to elicit antitumor immunity against p185neu-overexpressing MBT-2 bladder tumor cells. We found that mice treated with hN'-neu-Foxo3 shRNA showed greater reductions in tumor growth and longer survival times than mice treated with hN'-neu-scramble shRNA, indicating that the silencing of Foxo3 enhanced the antitumor efficacy of the HER-2/neu cancer vaccine. Cytotoxicity analyses further revealed that the Foxo3 shRNA-enhanced antitumor effect was associated with significant increases in the number of functional CD8(+) T cells and in the levels of cytotoxic T lymphocytes activity. Interleukin-6 was induced by hN'-neu-Foxo3 shRNA treatment but did not have a critical role in the antitumor effect of the hN'-neu-Foxo3 shRNA vaccine. Moreover, in vivo lymphocyte depletion analyses confirmed that the antitumor efficacy of the hN'-neu-Foxo3 shRNA vaccine depended on functional CD8(+) T cells. Finally, Foxo3 suppression was shown to markedly improve the effect of the HER-2/neu DNA vaccine in limiting the growth and lung metastases of MBT-2 cells. Overall, these results support RNAi-mediated silencing of Foxo3 as an effective strategy to enhance the therapeutic antitumor effect of HER-2/neu DNA vaccines against p185neu-positive tumors.
Institute of Biomedical Sciences, College of Life Science, National Chung Hsing University, Taichung, Taiwan.
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Wang
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Chang
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Yen
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Tu
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Chu
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Peng
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Chen
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Lan
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Lin
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism*; D019470:Biolistics; D019496:Cancer Vaccines / Q000276:immunology*; D002460:Cell Line; D002522:Chlorocebus aethiops; D003713:Dendritic Cells / Q000276:immunology; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics*; D018734:Genes, erbB-2; D005822:Genetic Vectors; D006801:Humans; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology; D001749:Urinary Bladder Neoplasms / Q000517:prevention & control; D019444:Vaccines, DNA / Q000276:immunology*
D019496:Cancer Vaccines; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C474033:FoxO3 protein, mouse; D034741:RNA, Small Interfering; D019444:Vaccines, DNA