Nanoparticles for Enhanced Adoptive T Cell Therapies and Future Perspectives for CNS Tumors

Purpose: Adoptive T cell therapy has revolutionized treatment of some hematologic malignancies but remains limited in solid tumours—especially central nervous system (CNS) tumours—by poor intratumoral delivery across anatomical barriers, suboptimal T cell specificity or activation, and intratumoral T cell dysfunction caused by immunosuppressive tumour microenvironments. Nanoparticles may overcome these limitations by improving ex vivo T cell manufacture, enabling co-localised stimulation, and adding functionality when conjugated to T cells.

Hypothesis: No formal experimental hypothesis. Central thesis: nanoparticle-based strategies that enhance T cell therapy for solid tumours—by improving ex vivo T cell activation/expansion, overcoming tumour microenvironment (TME) immunosuppression, aiding tumour infiltration, and adding combination functionality—can plausibly be applied to treat CNS tumours. The authors explicitly hypothesize that principles of nanoparticle-enhanced T cell therapy can be successfully translated to brain and CNS tumours, although no studies yet demonstrate efficacy in the CNS tumour setting.

Aims: Summarise recent preclinical advances in using nanoparticles to enhance adoptive T cell therapy. - Highlight nanoparticle-mediated strategies to prepare T cell products for adoptive therapy. - Discuss nanoparticles conjugated to T cells to overcome TME immunosuppression. - Review nanoparticles that enhance T cell tumour infiltration, activate T cells in situ, and/or add functionality to T cell therapy. - Discuss potential applicability and constraints of nanoparticle-enhanced T cells as a new platform for treating CNS tumours.

Delivery system: Nanoparticle types: carbon nanotubes, polymer-based particles (PLGA, PEG hydrogels, polymeric nanocarriers), magnetic nanoparticles (paramagnetic nanoparticles, biomimetic magnetosomes, magnetic nanoclusters), lipid nanoparticles/liposomes (immunoliposomes, ionisable lipid nanoparticles, PEGylated liposomes, maleimide-functionalised liposomes), gold nanoparticles, mesoporous silica micro-rods, protein nanogels, Prussian blue nanoparticles. - Payloads/cargo: anti-CD3 and anti-CD28 antibodies, MHC-I/peptide complexes, IL-2, IL-15 superagonist (IL-15SA), IL-21, TGF-β inhibitor, siRNA, mRNA encoding CAR, PI3K inhibitor, α-GalCer, indocyanine green (ICG), adenosine antagonist, anti-PD-1 antibodies, CAR plasmid DNA, bispecific aptamers. - Targeting/functionalization: antibodies against CD3, CD28, CD45, CD90, Thy1.1, PD-1; tumour-targeting peptide iRGD; immune cell membranes; CAR T cell membranes; magnetic guidance. - CNS-relevant strategies proposed: artificial antigen-presenting cells (aAPCs) engineered with CNS tumour antigens; magnetic nanoparticles conjugated to T cells for MRI-guided delivery; nanoparticle-mediated photothermal therapy to prime the CNS TME; nanoparticles targeting endogenous T cells to bypass ex vivo engineering.

Approach: Perspective review of preclinical literature, with no primary experiments. Discussed in vitro systems include primary T cells, antigen-specific T cells, CAR T cells, and T cell cultures. In vivo models include mouse melanoma, leukaemia, lymphoma, hepatocellular carcinoma, and other solid tumour models. Clinical context includes FDA-approved T cell therapeutics (Kymriah, Yescarta, Breyanzi) and glioblastoma clinical trials. The authors note that no studies show efficacy of nanoparticle-enhanced T cell therapy in CNS tumours.

Key methods: Review-level synthesis of: - T cell activation, proliferation, memory phenotype, and granzyme expression. - Gene silencing (siRNA) and mRNA delivery for transient CAR expression. - Antigen-specific cytotoxicity and T cell expansion. - Tumour growth inhibition, regression, and survival in mouse models. - Magnetic accumulation and MRI guidance. - Photothermal effects and TME remodeling. - TME immunosuppression reversal and adenosine pathway blockade. - Artificial antigen-presenting cell (aAPC) performance and T cell product output.

Key results: Representative findings from cited studies: - Nanostructured PEG hydrogels with anti-CD3-conjugated gold nanoparticles enabled T cell activation, proliferation, and memory. - Immunoliposomes targeting CD90 delivered a TGF-β inhibitor, enhanced T cell activation and granzyme expression, and produced the most T cell-mediated antitumor activity after adoptive transfer. - Gold nanoparticle photoporation delivered siRNA to T cells with significantly less cell death than nucleofection. - Ionisable lipid nanoparticles delivered CD19 CAR mRNA with decreased cell death compared with electroporation and achieved anti-tumour efficacy in a leukaemia model. - Carbon nanotube–polymer composites with MHC-I and anti-CD28 expanded T cells with 1000× less IL-2 than standard manufacture and delayed melanoma growth in mice. - Biomimetic scaffolds mimicking aAPCs expanded polyclonal and EBV-specific cytotoxic T cells and CAR T cells, enabling lymphoma regression in vivo. - IL-15SA nanogels conjugated to T cells released cargo only upon T cell receptor–antigen binding, increasing intratumoral T cell expansion and CAR T cell-mediated tumour clearance. - Liposomal adenosine antagonist attached to CAR T cells blocked adenosine-mediated immunosuppression in the TME. - Lipid nanoparticles carrying PI3K inhibitor, iRGD, and α-GalCer remodeled the TME and improved CAR T cell expansion and tumour regression. - PLGA nanoparticles encapsulating ICG enabled photothermal therapy that increased CAR T cell accumulation and anti-tumour efficacy. - Magnetic nanoclusters armed with anti-PD-1 antibodies magnetically recruited T cells to tumours and disassembled to release anti-PD-1. - DNA nanocarriers generated CAR T cells in vivo at levels equivalent to conventionally infused CAR T cells. - Circular bispecific aptamers activated T cells in situ and promoted T cell accumulation in the TME. - Prussian blue nanoparticles conjugated to antigen-specific T cells combined photothermal therapy with T cell cytotoxicity. - IR780-loaded mesoporous silica nanoparticles coated with CAR T cell membranes targeted GPC3+ hepatocellular carcinoma.

Interpretation: Nanoparticles offer unique advantages for T cell therapy, including the ability to penetrate anatomical barriers, encapsulate or immobilise therapeutic cargo, and specifically target tumour cells. The authors propose that nanoparticle-enhanced T cell therapy could be adapted for CNS tumours through aAPCs presenting CNS tumour antigens, magnetic guidance across the blood–brain barrier, photothermal priming of the CNS TME, and in situ targeting of endogenous T cells. However, no studies have yet demonstrated efficacy in CNS tumours, and clinical translation remains distant.

Limitations: Perspective article; no primary data. - No studies show efficacy of nanoparticle-enhanced T cell therapy in CNS tumours. - CNS tumours face restrictive anatomical barriers, including the blood–brain barrier, limiting T cell delivery. - Solid tumour TMEs are immunosuppressive and heterogeneous, impairing T cell function. - Photothermal therapy is not clinically approved; magnetic nanoparticles remain under clinical investigation. - Therapeutic T cells may need intratumoral administration in the absence of additional TME manipulations. - Efficacy of in situ T cell targeting may be limited by the number of endogenous T cells in the tumour. - Clinical application of several strategies (e.g., DNA nanocarriers, bispecific aptamers) has not yet been reported. - Safety, scalability, and regulatory pathways for nanoparticle-enhanced T cell products remain unresolved.