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Aptamer-targeted inhibition of mTOR in T cells enhances antitumor immunity.

ABSTRACT: Recent studies have underscored the importance of memory T cells in mediating protective immunity against pathogens and cancer. Pharmacological inhibition of regulators that mediate T cell differentiation promotes the differentiation of activated CD8(+) T cells into memory cells. Nonetheless, pharmacological agents have broad targets and can induce undesirable immunosuppressive effects. Here, we tested the hypothesis that aptamer-targeted siRNA inhibition of mTOR complex 1 (mTORC1) function in CD8(+) T cells can enhance their differentiation into memory T cells and potentiate antitumor immunity more effectively than the pharmacologic inhibitor rapamycin. To specifically target activated cells, we conjugated an siRNA targeting the mTORC1 component raptor to an aptamer that binds 4-1BB, a costimulatory molecule that is expressed on CD8(+) T cells following TCR stimulation. We found that systemic administration of the 4-1BB aptamer-raptor siRNA to mice downregulated mTORC1 activity in the majority of CD8(+) T cells, leading to the generation of a potent memory response that exhibited cytotoxic effector functions and enhanced vaccine-induced protective immunity in tumor-bearing mice. In contrast, while treatment with the general mTORC1 inhibitor rapamycin also enhanced antigen-activated CD8(+) T cell persistence, the cytotoxic effector functions of the reactivated memory cells were reduced and the alloreactivity of DCs was diminished. Consistent with the immunological findings, mice treated with rapamycin, but not with 4-1BB aptamer-raptor siRNA, failed to reject a subsequent tumor challenge.

SUBMITTER: Berezhnoy A

PROVIDER: S-EPMC3871234 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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Aptamer-targeted inhibition of mTOR in T cells enhances antitumor immunity.

Berezhnoy Alexey A Castro Iris I Levay Agata A Malek Thomas R TR Gilboa Eli E

The Journal of clinical investigation 20140101 1

Recent studies have underscored the importance of memory T cells in mediating protective immunity against pathogens and cancer. Pharmacological inhibition of regulators that mediate T cell differentiation promotes the differentiation of activated CD8(+) T cells into memory cells. Nonetheless, pharmacological agents have broad targets and can induce undesirable immunosuppressive effects. Here, we tested the hypothesis that aptamer-targeted siRNA inhibition of mTOR complex 1 (mTORC1) function in C ...[more]

PMID: 24292708

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Project description:Cancer immunotherapy using monoclonal antibodies (mAbs) to immune checkpoint (e.g., PD-1) has revolutionized the cancer treatments with long-term clinical benefits and being applicable to a wide range of tumors. However, a significant fraction of cancer patients does not respond to PD-1 blockade-based monotherapy. Considering the potential of combinatorial therapies in overcoming existing limitations of cancer immunotherapy, there is an increasing need to identify small-molecule modulators of immune cells capable of augmenting the effect of PD-1 blockade, leading to better cancer treatment. Although epigenetic drugs have shown potential in combination therapy, the lack of sequence specificity is a major concern. Pyrrole–imidazole polyamide (PIP), a selective DNA-binding small molecule, can guide epigenetic modulators to enable targeted gene activation. Here, we prepared and screened a library of PIPs encompassing the distinct PIPs conjugated with P300/CBP-selective bromodomain inhibitor (BI), which acts as a P300/CBP recruiter, and identified a PIP called BI-PIP-R that can trigger the targeted induction of the peroxisome proliferator-activated receptor-gamma coactivator 1 alpha/beta (PGC-1a/b), a regulator of mitochondrial activation and biogenesis. We further improved the chemical architecture of BI-PIP-R using a tri-arginine vector for better nuclear accumulation. This designer dual-functional molecule termed EnPGC-1 that enhanced mitochondrial activation, energy metabolism, proliferation of CD8+ T cells in vitro, and, in particular, enhanced oxidative phosphorylation (OXPHOS), a feature of long-lived memory T cells. Genome-wide gene analysis also suggested that EnPGC-1 and not the control compounds can regulate of T cell activation as a major biological process. EnPGC-1 also synergized with PD-1 blockade to enhance antitumor immunity and improved the survival. Together, this study represents the first example of a programmable DNA-based epigenetic drug with the potential to overcome the existing issues in cancer immunotherapy.

Dataset Information

Aptamer-targeted inhibition of mTOR in T cells enhances antitumor immunity.

Publications

Aptamer-targeted inhibition of mTOR in T cells enhances antitumor immunity.

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