Nanocarrier-based immunotherapy in cancer management and research

Purpose: Cancer immunotherapy can induce specific antitumor immunity, control metastases, and provide immunological memory, but faces barriers including immunosuppressive tumour microenvironments and poor delivery of immunomodulators. Nanocarriers offer a versatile way to deliver antigens, adjuvants, cytokines, antibodies, and drugs to immune cells or tumours, improving stability, targeting, and controlled release.

Hypothesis: No formal experimental hypothesis. Central thesis: nanocarrier-based delivery of immunomodulators—alone or in combination—can enhance anticancer immune responses, improve targeting to antigen-presenting cells and tumours, and overcome limitations of soluble immunotherapeutic formulations.

Aims: Review cancer immunotherapy with special focus on nanocarrier-based targeted approaches. - Cover both prophylactic and therapeutic immunotherapy. - Analyse key studies with respect to underlying immunological principles. - Highlight clinical utility, successes, and nanocarrier-based immunotherapies in clinical trials.

Delivery system: Polymeric nanocarriers: PLGA NPs, poly-α-hydroxy acid microparticles, polyketal microparticles, PBCA NPs, poly-γ-glutamic acid NPs, chitosan NPs, alginate hydrogels, acid-degradable hydrogels, PEGylated liposomes. - Lipid-based systems: liposomes, fusogenic liposomes, bubble liposomes, interbilayer-crosslinked multilamellar vesicles (ICMVs), cationic liposome-plasmid complexes, nanoemulsions. - Inorganic systems: gold NPs, iron oxide-zinc oxide core-shell NPs, magnetite NPs. - Other platforms: virus-like particles, three-dimensional polymeric scaffolds, monoclonal antibodies, bispecific antibodies. - Payloads: tumour-associated antigens (OVA, HGP, TRP, MUC1, CEA, MAGE, gp100), whole tumour lysate, TLR ligands/adjuvants (CpG ODN, poly I:C, LPS, MPLA, R848, P-LPS), cytokines (IL-2, IL-12, IL-15, TNF-α, IFN-γ, GM-CSF), antibodies/ligands (anti-DEC-205, anti-DC-SIGN, CD40L, anti-CD25), chemokines, siRNA/plasmid DNA, and anticancer drugs (paclitaxel, doxorubicin). - Targeting strategies: passive EPR effect, active DC targeting, lymph node targeting, tumour microenvironment targeting.

Approach: Review of in vitro and in vivo studies and clinical trials. Preclinical models include mouse melanoma (B16/BL6/B16-F10), E.G7-OVA thymoma, MO-5 melanoma, lung metastasis, glioblastoma, head and neck squamous cell carcinoma, and other tumour models. Clinical examples include Doxil, Abraxane, Ad-ISF35, Allovectin-7, TNF-α-bound PEGylated gold NPs, PEGylated liposomal doxorubicin plus IL-18, Cervarix, and Gardasil. Clinical phases range from phase I to phase III, with some approvals and one phase III failure.

Key methods: Immune cell quantification and characterisation: tumour-infiltrating APCs, macrophages, DCs, CD4+ and CD8+ T cells, Tregs, MDSCs. - Cytokine secretion: IFN-γ, TNF-α, IL-2, IL-6, IL-12, IL-10. - Antibody responses: antigen-specific IgG, IgG1, IgG2a titers. - CTL-mediated killing, MHC I/II presentation, cross-presentation, DC maturation, lymph node targeting, complement activation. - Tumour growth inhibition, survival, metastasis reduction. - Particle characterisation: size, surface charge, encapsulation versus adsorption, release kinetics.

Key results: 25 nm and 100 nm OVA-conjugated polyhydroxylated NPs induced DC maturation and CD8+ T-cell activation comparable to OVA plus LPS; antibody titers persisted up to 21 days. - OVA encapsulated in PLGA NPs led to 1,000-fold higher T-cell-mediated IL-2 secretion than free antigen; class I presentation extended up to 96 hours. - Paclitaxel and P-LPS co-encapsulated in PLGA NPs reduced mean tumour volume by ~40% versus paclitaxel and P-LPS alone in a B16-F10 melanoma model, with greater APC and T-cell infiltration. - Gold NPs conjugated with CpG enhanced macrophage stimulation; Hp91 immunostimulatory peptide was 5-fold more potent when encapsulated and 20-fold more potent when surface-conjugated versus free peptide, with high DC/macrophage infiltration and prolonged survival in mice. - NP-Ag-treated DCs enhanced CTL responses, delayed tumour growth, and increased survival; patient-derived DCs stimulated CD8+ T cells with increased IFNγ and decreased IL-10 in 80% of patients. - Chitosan NPs generated potent Th1 and Th2 responses; poly-γ-glutamic acid NPs activated splenic DCs via NF-κB and MAPK pathways. - Small particles (0.43 and 1 µm) were readily taken up by DCs and induced IL-1β via NALP3 inflammasome; larger particles (10 and 32 µm) showed limited uptake. - Clinical: Doxil and Abraxane approved; Ad-ISF35 reached phase II; Allovectin-7 failed phase III; TNF-α gold NPs reached phase II; PEGylated liposomal doxorubicin plus IL-18 reached phase II; Cervarix and Gardasil approved.

Interpretation: Nanocarriers offer an attractive mode of delivery for immunotherapeutics, reducing systemic cytotoxicity, improving tumour localisation, and providing sustained release that enhances effector and memory immune responses. Combination chemoimmunotherapy can be synergistic. Polymers with inherent immunomodulatory activity may serve dual roles as adjuvants and carriers. The authors conclude that nanotechnology-based approaches can revolutionize cancer immunotherapy, but translation requires attention to scale-up, stability, safety, and biological interactions.

Limitations: Review article; no primary experimental data. - Most nanocarrier-based immunotherapies remain preclinical; clinical translation is limited, and one major candidate (Allovectin-7) failed phase III. - Nanoparticles are recognised as foreign; plasma protein interactions, clearance, and efficacy require thorough evaluation. - “Burst” release after administration may cause sudden free drug spikes, toxicity, and nonspecific accumulation. - Better understanding of nanoparticle fate in biological milieu is needed for improved safety and efficacy. - Scale-up feasibility, cost-effectiveness, residual solvents, drying/purification, and sterilisation steps must be considered for long-term stability and storage. - Tumour heterogeneity, immunoediting, and presence of self-antigens complicate prophylactic strategies.