In Vivo Targeting of Intratumor Regulatory T Cells Using PEG-Modified Single-Walled Carbon Nanotubes

Bioconjugate Chemistry (Impact Factor: 4.82). 05/2013; 24(6). DOI: 10.1021/bc400070q
Source: PubMed

ABSTRACT Recent evidence regarding the role of regulatory T cells (Treg) in tumor development has suggested that the manipulation of Treg function selectively in the tumor microenvironment would be a desirable immunotherapy approach. Targeting intra-tumor immune populations would reduce side effects on peripheral healthy cells and increase anti-tumor efficacy of immunotherapies. However, no current approaches are available which enable selective in vivo targeting of intra-tumor Treg or other immune cell subpopulations. Herein, we investigated the ability of ligands against Treg-specific receptors to drive selective internalization of PEG-modified single-walled carbon nanotubes (PEG-SWCNTs) into Treg residing in the tumor microenvironment. We focused our attention on the glucocorticoid-induced TNFR-related receptor (GITR), as it showed higher over-expression on intra-tumor vs. peripheral (i.e. splenic) Treg compared to other reported Treg-specific markers (folate receptor 4, CD103 and CD39). Ex vivo investigations showed that the Treg targeting efficiency and selectivity of PEG-SWCNTs depended on incubation time, dose, number of ligands per nanotube and targeted surface marker. In vivo investigations showed that PEG-SWCNTs armed with GITR ligands targeted Treg residing in a B16 melanoma more efficiently then intra-tumor non-Treg or splenic Treg. The latter result was achieved by exploiting a combination of passive tumor targeting due to enhanced tumor vascular permeability, naturally increased intra-tumor Treg vs. effector T cell (Teff) ratio and active targeting of markers that are enriched in intra-tumor vs. splenic Treg. We also found that PEG-SWCNTs loaded with GITR ligands were internalized by Treg through receptor-mediated endocytosis and transported into the cytoplasm and nucleus ex vivo and in vivo. This is the first example of intra-tumor immune cell targeting and we hope it will pave the way to innovative immunotherapies against cancer.

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May 29, 2014