A Novel Cancer Therapy by Skin Delivery of Indoleamine 2,3-Dioxygenase siRNA

Abstract

Purpose: Indoleamine 2,3-dioxygenase (IDO), an enzyme that degrades tryptophan, is a negative immune regulatory molecule of dendritic cells. IDO-expressing dendritic cells suppress Tcell responses and may be immunosuppressive in vivo.We hypothesized that silencing the IDO expression in skin dendritic cells in vivo could elicit antitumor activity in tumor-draining lymph nodes. Experimental Design: The efficiency of IDO-specific small interfering RNA (siRNA) was evaluated in vitro and in vivo. The therapeutic effect was evaluated in MBT-2 murine bladder tumor model and CT-26 colon tumor models. Results: IDO expression was down-regulated in CD11c-positive lymphocytes after IDO siRNA treatment. In vivo skin administration of IDO siRNA inhibited tumor growth and prolonged survival in both tumor models. The number of infiltrated T cells and neutrophils increased at tumor sites, which are correlated with therapeutic efficacy. TheTcells may be mainly responsible for the immunologic rejection because the effect was abolished by depletion of CD8-positive T cells. Adoptive transfer of CD11c-positive dendritic cells from vaccinated mice delayed tumor progression. The cancer therapeutic effect was reproducibly observed with another IDO siRNA targeting at different site, suggesting the effect was not due to off-target effect. In a neu-overexpressing MBT-2 tumor model, IDO siRNA enhanced the therapeutic efficacy of Her2/Neu DNA vaccine. Down-regulation of IDO2, an IDO homologue, with siRNA also generated antitumor immunity in vivo. Conclusions: Antitumor immunity can be effectively elicited by physical delivery of siRNAs targeting immunoregulatory genes in skin dendritic cells in vivo, as shown by IDO and IDO2 in this report.

RNA interference-mediated silencing of Foxo3 in antigen-presenting cells as a strategy for the enhancement of DNA vaccine potency

“…4 To this end, the antitumor efficacy of DNA vaccines can be enhanced when administered via gene gun in conjunction with short hairpin RNAs (shRNAs) that target key proapoptotic proteins including Bax, Bak or Fas ligand; [5][6][7] immunosuppressive cytokines such as interleukin (IL)-10; 8 or immunoregulatory proteins such as indoleamine 2,3-dioxygenase. 9 Consequently, these lines of evidence support the notion that gene gun administration represents an efficient method for the in vivo delivery of shRNAs into professional APCs to modulate the antitumor immunity elicited by DNA vaccines.…”

Selective inhibition of IDO1 effectively regulates mediators of antitumor immunity

“…This has been primarily supported by studies involving 1MT, 8,9 but also by experiments using biochemical and genetic approaches such as siRNA and IDO1-null mice. [45][46][47] More recent studies suggest that the L-1MT isomer selectively inhibits the IDO1 enzyme and blocks trp to kyn conversion in vitro, whereas D-1MT, which is more selective for IDO2, shows better in vivo activity than L-1MT in mouse models. However, IDO2, unlike IDO1, was recently found to be ineffective Ϯ SEM (n ϭ 9-11 mice/group) are shown from the initiation of dosing (ϳ 90-120 mm 3 ).…”

Skin delivery of short hairpin RNA of indoleamine 2,3 dioxygenase induces antitumor immunity against orthotopic and metastatic liver cancer

“…Previously, we have delivered short hairpin RNA (shRNA) of IDO by skin administration to delay tumor progression in multiple subcutaneous tumor models, (25) suggesting that the strategy might be useful in treating liver cancer. This gene gun approach provides a proof of concept that we can manipulate immune responses against cancer without ex vivo manipulation of dendritic cells.…”

“…Indoleamine 2,3-dioxygenase shRNA and scramble IDO shRNA have been described previously. (25) Plasmid DNA was purified using the Endofree Qiagen Plasmid Mega Kits (Qiagen, Chatsworth, CA, USA) and was resuspended in sterile water at a concentration of 1 lg ⁄ lL.…”

“…Tumor-bearing mice were bombarded with 10 lg of plasmid DNA (20 lL of sterile water) through a low-pressure gene gun (BioWare Technologies Co. Ltd, Taipei, Taiwan) at 50 psi of helium gas pressure. (25) The subcutaneous and orthotopic tumorbearing mice were bombarded once a week, whereas the metastatic tumor-bearing mice were bombarded twice a week.…”