Over the past decade, immunotherapy has emerged as a promising new form of cancer treatment with the potential to eradicate tumor metastasis. However, its curative potential is in general limited by the existence of negative feedback mechanisms that control dendritic cells (DCs) and T-cell activation. For clinically effective immunity, there is a need of inhibiting the expression of these immune suppressors. This could enhance the activation of DCs, T cells, and natural killer cells, and might be beneficial for cancer immunotherapy. Among the immune inhibitory molecules expressed by DCs is indoleamine 2,3-dioxygenase (IDO), an enzyme that conveys immunosuppressive effects by degrading tryptophan, an essential amino acid required for T-cell proliferation and survival. Depletion of tryptophan by IDO-positive DCs induces T-cell apoptosis and the conversion of naïve CD4+ T cells into regulatory T cells that further suppress antitumor immunity. Herein, we describe a protocol for in vitro synthesis of small interfering RNA against IDO and other immunosuppressive factors such as interleukin-10 and programmed cell death-1 ligands in order to reverse immune suppression mediated by DCs. Vaccination with IDO-silenced DC vaccines enhanced immune responses and antitumor immunity in cancer patients.
siRNA IDO Immunosuppression DC vaccine Immunotherapy
This is a preview of subscription content, log in to check access.
Springer Nature is developing a new tool to find and evaluate Protocols. Learn more
Hoos A, Britten CM, Huber C, O’Donnell-Tormey J (2011) A methodological framework to enhance the clinical success of cancer immunotherapy. Nat Biotechnol 29:867–870PubMedCrossRefGoogle Scholar
Munn DH, Sharma MD, Lee JR, Jhaver KG, Johnson TS et al (2002) Potential regulatory function of human dendritic cells expressing indoleamine 2,3-dioxygenase. Science 297:1867–1870PubMedCrossRefGoogle Scholar
Hwu P, Du MX, Lapointe R, Do M, Taylor M-W, Young HA (2000) Indoleamine 2,3-dioxygenase production by human dendritic cells results in the inhibition of T cell proliferation. J Immunol 164:3596–3599PubMedCrossRefGoogle Scholar
Munn DH, Sharma MD, Hou D (2004) Expression of indoleamine 2,3-dioxygenase by plasmacytoid dendritic cells in draining-draining lymph nodes. J Clin Invest 114:280–290PubMedCrossRefPubMedCentralGoogle Scholar
Jonuleit H, Schmitt E, Stenbrink K, Enk AH (2001) Dendritic cells as a tool to induce anergic and regulatory T cells. Trends Immunol 22:394–400PubMedCrossRefGoogle Scholar
Flatekval GF, Sioud M (2009) Modulation of dendritic cell function and maturation with mono- and bifunctional small interfering RNAs targeting indoleamine 2,3-dioxygenase. Immunology 128:e837–e848PubMedCrossRefPubMedCentralGoogle Scholar
Sioud M, Saebøe-Larssen S, Hetland TE, Kaern J, Mobergslien A, Kvalheim G (2013) Silencing of indoleamine 2,3-dioxygenase enhances dendritic cell immunogenicity and antitumour immunity in cancer patients. Int J Oncol 43:280–288PubMedGoogle Scholar