Tumor-Associated Exosomes: A Potential Therapeutic Target for Restoring Anti-Tumor T Cell Responses in Human Tumor Microenvironments

Exosomes are a subset of extracellular vesicles (EVs) that are released by cells and play a variety of physiological roles including regulation of the immune system. Exosomes are heterogeneous and present in vast numbers in tumor microenvironments. A large subset of these vesicles has been demonstrated to be immunosuppressive. In this review, we focus on the suppression of T cell function by exosomes in human tumor microenvironments. We start with a brief introduction to exosomes, with emphasis on their biogenesis, isolation and characterization. Next, we discuss the immunosuppressive effect of exosomes on T cells, reviewing in vitro studies demonstrating the role of different proteins, nucleic acids and lipids known to be associated with exosome-mediated suppression of T cell function. Here, we also discuss initial proof-of-principle studies that established the potential for rescuing T cell function by blocking or targeting exosomes. In the final section, we review different in vivo models that were utilized to study as well as target exosome-mediated immunosuppression, highlighting the Xenomimetic mouse (X-mouse) model and the Omental Tumor Xenograft (OTX) model that were featured in a recent study to evaluate the efficacy of a novel phosphatidylserine-binding molecule for targeting immunosuppressive tumor-associated exosomes.

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TSR-033, a Novel Therapeutic Antibody Targeting LAG-3, Enhances T-Cell Function and the Activity of PD-1 Blockade In Vitro and In Vivo

Molecular Cancer Therapeutics ◽

10.1158/1535-7163.mct-18-0836 ◽

2018 ◽

Vol 18 (3) ◽

pp. 632-641 ◽

Cited By ~ 14

Author(s):

Srimoyee Ghosh ◽

Geeta Sharma ◽

Jon Travers ◽

Sujatha Kumar ◽

Justin Choi ◽

...

Keyword(s):

T Cell ◽

Cell Function ◽

Therapeutic Antibody ◽

T Cell Function ◽

Antibody Targeting ◽

Novel Therapeutic

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Cholesterol Lowering Modulates T Cell Function In Vivo and In Vitro

PLoS ONE ◽

10.1371/journal.pone.0092095 ◽

2014 ◽

Vol 9 (3) ◽

pp. e92095 ◽

Cited By ~ 22

Author(s):

Kuang-Yuh Chyu ◽

Wai Man Lio ◽

Paul C. Dimayuga ◽

Jianchang Zhou ◽

Xiaoning Zhao ◽

...

Keyword(s):

T Cell ◽

Cell Function ◽

Cholesterol Lowering ◽

T Cell Function

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The Cysteine-Containing Cell-Penetrating Peptide AP Enables Efficient Macromolecule Delivery to T Cells and Controls Autoimmune Encephalomyelitis

Pharmaceutics ◽

10.3390/pharmaceutics13081134 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1134

Author(s):

Won-Ju Kim ◽

Gil-Ran Kim ◽

Hyun-Jung Cho ◽

Je-Min Choi

Keyword(s):

Drug Delivery ◽

T Cells ◽

T Cell ◽

Cell Function ◽

Fluorescent Protein ◽

Autoimmune Encephalomyelitis ◽

Optimal Sequence ◽

T Cell Function

T cells are key immune cells involved in the pathogenesis of several diseases, rendering them important therapeutic targets. Although drug delivery to T cells is the subject of continuous research, it remains challenging to deliver drugs to primary T cells. Here, we used a peptide-based drug delivery system, AP, which was previously developed as a transdermal delivery peptide, to modulate T cell function. We first identified that AP-conjugated enhanced green fluorescent protein (EGFP) was efficiently delivered to non-phagocytic human T cells. We also confirmed that a nine-amino acid sequence with one cysteine residue was the optimal sequence for protein delivery to T cells. Next, we identified the biodistribution of AP-dTomato protein in vivo after systemic administration, and transduced it to various tissues, such as the spleen, liver, intestines, and even to the brain across the blood–brain barrier. Next, to confirm AP-based T cell regulation, we synthesized the AP-conjugated cytoplasmic domain of CTLA-4, AP-ctCTLA-4 peptide. AP-ctCTLA-4 reduced IL-17A expression under Th17 differentiation conditions in vitro and ameliorated experimental autoimmune encephalomyelitis, with decreased numbers of pathogenic IL-17A+GM-CSF+ CD4 T cells. These results collectively suggest the AP peptide can be used for the successful intracellular regulation of T cell function, especially in the CNS.

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CD3 limits the efficacy of TCR gene therapy in vivo

Blood ◽

10.1182/blood-2011-04-346338 ◽

2011 ◽

Vol 118 (13) ◽

pp. 3528-3537 ◽

Cited By ~ 64

Author(s):

Maryam Ahmadi ◽

Judith W. King ◽

Shao-An Xue ◽

Cécile Voisine ◽

Angelika Holler ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Cell Function ◽

Cell Receptor ◽

Surface Expression ◽

T Cell Function ◽

Engineered T Cells ◽

Rate Limiting

Abstract The function of T-cell receptor (TCR) gene modified T cells is dependent on efficient surface expression of the introduced TCR α/β heterodimer. We tested whether endogenous CD3 chains are rate-limiting for TCR expression and antigen-specific T-cell function. We show that co-transfer of CD3 and TCR genes into primary murine T cells enhanced TCR expression and antigen-specific T-cell function in vitro. Peptide titration experiments showed that T cells expressing introduced CD3 and TCR genes recognized lower concentration of antigen than T cells expressing TCR only. In vivo imaging revealed that TCR+CD3 gene modified T cells infiltrated tumors faster and in larger numbers, which resulted in more rapid tumor elimination compared with T cells modified by TCR only. After tumor clearance, TCR+CD3 engineered T cells persisted in larger numbers than TCR-only T cells and mounted a more effective memory response when rechallenged with antigen. The data demonstrate that provision of additional CD3 molecules is an effective strategy to enhance the avidity, anti-tumor activity and functional memory formation of TCR gene modified T cells in vivo.

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Exendin-4 Exacerbates Burn-Induced Morbidity in Mice by Activation of the Sympathetic Nervous System

Mediators of Inflammation ◽

10.1155/2019/2750528 ◽

2019 ◽

Vol 2019 ◽

pp. 1-16 ◽

Cited By ~ 1

Author(s):

Xiao-Jing Ji ◽

Ji-Wei Hao ◽

Guang-Lei Li ◽

Ning Dong ◽

Xin-Qi Wang ◽

...

Keyword(s):

Nervous System ◽

T Cell ◽

Sympathetic Nervous System ◽

Cell Function ◽

Burn Injury ◽

Total Body Surface Area ◽

T Cell Function ◽

Sympathetic Nervous

Background. Although glucagon-like peptide 1- (GLP-1-) based therapy of hyperglycemia in burn injury has shown great potential in clinical trials, its safety is seldom evaluated. We hypothesize that exendin-4, a GLP-1 analogue, might affect the immune response via the activation of the sympathetic nervous system in burn injury. Methods. Male Balb/c mice were subjected to sham or thermal injury of 15% total body surface area. Exendin-4 on T cell function in vitro was examined in cultured splenocytes in the presence of β-adrenoceptor antagonist propranolol (1 nmol/L) or GLP-1R antagonist exendin (9-39) (1 μmol/L), whereas its in vivo effect was determined by i.p. injection of exendin-4 (2.4 nmol/kg) in mice. To further elucidate the sympathetic mechanism, propranolol (30 mg/kg) or vehicle was applied 30 min prior to injury. Results. Although the exacerbated burn-induced mortality by exendin-4 was worsened by propranolol pretreatment, the inhibition of T cell proliferation by exendin-4 in vitro could be restored by propranolol instead of exendin (9-39). However, a Th2 switch by exendin-4 in vitro could only be reversed by exendin (9-39). Likewise, the inhibition of splenic T cell function and NFAT activity by exendin-4 in vivo was restored by propranolol. By contrast, the increased splenic NF-κB translocation by exendin-4 in vivo was potentiated by propranolol in sham mice but suppressed in burn mice. Accordingly, propranolol abrogated the heightened inflammatory response in the lung and the accelerated organ injuries by exendin-4 in burn mice. On the contrary, a Th2 switch and higher serum levels of inflammatory mediators by exendin-4 were potentiated by propranolol in burn mice. Lastly, exendin-4 raised serum stress hormones which could be remarkably augmented by propranolol. Conclusions. Exendin-4 suppresses T cell function and promotes organ inflammation through the activation of the sympathetic nervous system, while elicits Th2 switch via GLP-1R in burn injury.

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Discovery and characterization of llama VHH targeting the RO form of human CD45

10.1101/2020.09.01.278853 ◽

2020 ◽

Author(s):

Deepti Rokkam ◽

Patrick J. Lupardus

Keyword(s):

T Cell ◽

Cell Function ◽

Tyrosine Phosphatase ◽

Surface Protein ◽

Cell Receptor ◽

Phage Display Library ◽

Signaling Complex ◽

T Cell Function

AbstractCD45 is an abundant and highly active cell-surface protein tyrosine phosphatase (PTP) found on cells of hematopoietic origin. CD45 is of particular importance for T-cell function, playing a key role in the activation/inactivation cycle of the T-cell receptor signaling complex. The extracellular domain of CD45 is comprised of an N-terminal mucin-like domain which can be alternatively spliced to a core domain (RO) consisting of four domains with fibronectin 3 domain (FN3)-like topology. The study of CD45 has been hampered by a small set of publicly available antibodies, which we characterized as specific to the N-terminal FN3 domains of CD45 RO. To broaden the human CD45 reagent set, we identified anti-CD45 single domain VHH antibodies from a post-immune llama phage display library. Using a yeast display domain mapping system and affinity measurement we characterized seven unique clonotypes specific for CD45 RO, including binders that target each of the four FN3-like domains. These VHH molecules are important new tools for studying the role of CD45 in T-cell function in vitro and in vivo.

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Targeting the myeloid checkpoint receptor SIRPα potentiates innate and adaptive immune responses to promote anti-tumor activity

Journal of Hematology & Oncology ◽

10.1186/s13045-020-00989-w ◽

2020 ◽

Vol 13 (1) ◽

Author(s):

Tracy C. Kuo ◽

Amy Chen ◽

Ons Harrabi ◽

Jonathan T. Sockolosky ◽

Anli Zhang ◽

...

Keyword(s):

T Cell ◽

Mononuclear Cells ◽

Regulatory Protein ◽

Human Tumor ◽

Tumor Xenograft ◽

Hematological Toxicity ◽

Human Tumor Xenograft ◽

Cynomolgus Monkeys

Abstract Background Signal regulatory protein α (SIRPα) is a myeloid-lineage inhibitory receptor that restricts innate immunity through engagement of its cell surface ligand CD47. Blockade of the CD47–SIRPα interaction synergizes with tumor-specific antibodies and T-cell checkpoint inhibitors by promoting myeloid-mediated antitumor functions leading to the induction of adaptive immunity. Inhibition of the CD47–SIRPα interaction has focused predominantly on targeting CD47, which is expressed ubiquitously and contributes to the accelerated blood clearance of anti-CD47 therapeutics. Targeting SIRPα, which is myeloid-restricted, may provide a differential pharmacokinetic, safety, and efficacy profile; however, SIRPα polymorphisms and lack of pan-allelic and species cross-reactive agents have limited the clinical translation of antibodies against SIRPα. Here, we report the development of humanized AB21 (hAB21), a pan-allelic anti-SIRPα antibody that binds human, cynomolgus monkey, and mouse SIRPα alleles with high affinity and blocks the interaction with CD47. Methods Human macrophages derived from donors with various SIRPα v1 and v2 allelic status were used to assess the ability of hAB21 to enhance phagocytosis. HAB21_IgG subclasses were evaluated for targeted depletion of peripheral blood mononuclear cells, phagocytosis and in vivo efficacy in xenograft models. Combination therapy with anti-PD1/anti-PD-L1 in several syngeneic models was performed. Immunophenotyping of tissues from MC38 tumor-bearing mice treated with AB21 and anti-PD-1 was evaluated. PK, PD and tolerability of hAB21 were evaluated in cynomolgus monkeys. Results SIRPα blockade with hAB21 promoted macrophage-mediated antibody-dependent phagocytosis of tumor cells in vitro and improved responses to rituximab in the Raji human tumor xenograft mouse model. Combined with PD-1/PD-L1 blockade, AB21 improved response rates by facilitating monocyte activation, dendritic cell activation, and T cell effector functions resulting in long term, durable antitumor immunity. In cynomolgus monkeys, hAB21 has a half-life of 5.3 days at 10 mg/kg and complete target occupancy with no hematological toxicity or adverse findings at doses up to 30 mg/kg. Conclusions The in vitro and in vivo antitumor activity of hAB21 broadly recapitulates that of CD47 targeted therapies despite differences in ligand expression, binding partners, and function, validating the CD47–SIRPα axis as a fundamental myeloid checkpoint pathway and its blockade as promising therapeutic intervention for treatment of human malignancies.

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Eukaryotic expression of the broad-spectrum chemokine receptor antagonist vMIP-II and its effects on T-cell function in vitro and in vivo

Experimental Dermatology ◽

10.1111/j.1600-0625.2006.00455.x ◽

2006 ◽

Vol 15 (8) ◽

pp. 634-642 ◽

Cited By ~ 9

Author(s):

Simone Rubant ◽

Ralf J. Ludwig ◽

Jeannette Pfeffer ◽

Petra Schulze-Johann ◽

Roland Kaufmann ◽

...

Keyword(s):

T Cell ◽

Receptor Antagonist ◽

Chemokine Receptor ◽

Broad Spectrum ◽

Cell Function ◽

Eukaryotic Expression ◽

Chemokine Receptor Antagonist ◽

T Cell Function

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Novel phosphatidylserine-binding molecule enhances antitumor T-cell responses by targeting immunosuppressive exosomes in human tumor microenvironments

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2021-003148 ◽

2021 ◽

Vol 9 (10) ◽

pp. e003148

Author(s):

Maulasri Bhatta ◽

Gautam N Shenoy ◽

Jenni L Loyall ◽

Brian D Gray ◽

Meghana Bapardekar ◽

...

Keyword(s):

T Cell ◽

Mouse Model ◽

Ovarian Tumor ◽

Human Tumor ◽

T Cell Responses ◽

Tumor Xenograft ◽

High Avidity ◽

Cell Responses

BackgroundThe human tumor microenvironment (TME) is a complex and dynamic milieu of diverse acellular and cellular components, creating an immunosuppressive environment, which contributes to tumor progression. We have previously shown that phosphatidylserine (PS) expressed on the surface of exosomes isolated from human TMEs is causally linked to T-cell immunosuppression, representing a potential immunotherapeutic target. In this study, we investigated the effect of ExoBlock, a novel PS-binding molecule, on T-cell responses in the TME.MethodsWe designed and synthesized a new compound, (ZnDPA)6-DP-15K, a multivalent PS binder named ExoBlock. The PS-binding avidity of ExoBlock was tested using an in vitro competition assay. The ability of this molecule to reverse exosome-mediated immunosuppression in vitro was tested using human T-cell activation assays. The in vivo therapeutic efficacy of ExoBlock was then tested in two different human tumor xenograft models, the melanoma-based xenomimetic (X-)mouse model, and the ovarian tumor-based omental tumor xenograft (OTX) model.ResultsExoBlock was able to bind PS with high avidity and was found to consistently and significantly block the immunosuppressive activity of human ovarian tumor and melanoma-associated exosomes in vitro. ExoBlock was also able to significantly enhance T cell-mediated tumor suppression in vivo in both the X-mouse and the OTX model. In the X-mouse model, ExoBlock suppressed tumor recurrence in a T cell-dependent manner. In the OTX model, ExoBlock treatment resulted in an increase in the number as well as function of CD4 and CD8 T cells in the TME, which was associated with a reduction in tumor burden and metastasis, as well as in the number of circulating PS+ exosomes in tumor-bearing mice.ConclusionOur results establish that targeting exosomal PS in TMEs with ExoBlock represents a promising strategy to enhance antitumor T-cell responses.

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