Multimodal targeting of glioma with functionalized nanoparticles

Chimeric antigen receptors (CAR) are receptors that identify certain surface proteins and are synthesized. They are made up of single chain variable fragment (scFv) and are generated in the extracellular domain. CD3 is the intracellular component, and it contains immunoreceptor tyrosine-based activation motifs [145, 146]. In third-generation CAR, the intracellular domain has two costimulatory domains in addition to CD3, such as CD3-CD28-OX40 or CD3-CD28-41BB [145, 147]. CAR-T cells targeting the antigens Interleukin-13 receptor alpha 2 (IL13R2), human epidermal growth factor receptor 2 (HER2), and epidermal growth factor receptor variant III (EGFRvIII) have been produced in glioblastoma [146]. IL13R2 CAR-T has been used in glioblastoma treatment in a few clinical trials [146]. T-cell therapy benefits from nanoparticles. T-cells must be grown ex vivo before being processed for application. Various nanoparticles that operate as antigen-presenting portions have been proposed to improve expansion and minimize cost (Fig. 3). Polystyrene beads, liposomes, iron/dextran nanoparticles, and carbon nanotubes are among them. The most attention has been paid to Dynabeads, which are generally made of Fe3O4 in a polystyrene matrix and coated with anti-CD3 and anti-CD28 antibodies. They have consistently demonstrated T-cell expansion, are simple to handle, and have lower costs [148]. Fadel et al. developed antigen-attached carbon nanotubes in a similar way. Furthermore, IL-2 was combined with magnetite in poly(lactide-co-glycolide) nanoparticles. The nanoparticles stimulated T-cell proliferation with a 1000-fold lower use of IL-2, according to the researchers [149]. Nanoparticles could potentially be used to examine and track T-cells in real time. T-cells expressing melanoma-specific T-cell receptors were generated and tagged with gold nanoparticles by Meir et al. T-cells were subsequently injected into melanoma-bearing animals, and T-cells were tracked using CT. In contrast to non-engineered cells, the authors found that designed cells aggregated at the tumour location. The capacity to investigate the kinetics and biodistribution of T-cells is a key feature of the devised technique [150]. Nanoparticles can also be injected into the body along with T-cells. Tsao et al. created a poly(ethyleneglycol)-g-chitosan-based degradable hydrogel. At low temperatures, the gel is a liquid, and at higher degrees, it becomes a gel. The gel's goal was to encapsulate T-cells and manage their release in order to treat glioblastoma. In vitro, lymphocytes released from the gel killed glioblastoma cells, and poly(ethyleneglycol)-g-chitosan was more effective than Matrigel. Biocompatibility, degradability, and minimal immunogenicity are all advantages of poly(ethyleneglycol)-g-chitosan [151]. The use of photothermal therapy to improve T-cell therapy is another way to improve it. Chen et al. created poly(lactic-co-glycolic) acid nanoparticles that were loaded with the NIR dye indocyanine green. The nanoparticles were put into melanoma tumor-bearing mice. CAR-T against chondroitin sulphate proteoglycan-4 was also injected after that. After photothermal therapy, T-cell effectiveness rose, and the combined therapy had a therapeutic effect [152].

Tumors frequently develop a variety of defense mechanisms to prevent being eliminated by the immune system. Inhibition of T-cell response is one of the strategies. When certain antigens are exposed to T-cells, they become activated and attack tumour cells. Co-inhibitory molecules such as cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) and PD-1, on the other hand, prevent the cytotoxic T-cell response [153]. As a result, drugs that target CTLA4 and PD-1 hold a lot of promise as cancer treatments. Ipilimumab, a monoclonal antibody that targets CTLA4, has already been licenced by the FDA and the European Medicines Agency (EMA) for the treatment of melanoma. Rovelizumab, another CTLA4 antibody, has been licenced for the treatment of mesothelioma [154]. The FDA has also approved the anti-PD1 antibodies nivolumab and pembrolizumab for the treatment of melanoma and non-small-cell lung cancer (NSCLC) [155]. Atezolizumab and avelumab, two anti-PD-L1 antibodies, have also been approved [154]. There are a slew of preclinical studies and clinical trials testing immune-checkpoint modulators as cancer treatments. Glioblastomas have a high level of PDL1 expression. PDL1 expression is seen in 88 percent of freshly diagnosed glioblastomas and 72 percent of recurrent glioblastomas, according to the study. The expression is likewise very low in healthy tissue around it. Furthermore, the expression is much higher than in melanoma and NSCLC (about 30% and 25%–36 percent higher, respectively). PDL1 suppresses T-cell activation and lymphocyte production of Interferons (IFNs), IL-2, and IL-10 in glioma cells [153]. Due to the high expression of PDL1 in glioblastoma, anti-PD1/PDL1 monotherapy or combined therapy has received a lot of attention [153]. Immune checkpoint modulator monotherapy appears to be ineffective in glioblastoma. In recurrent glioblastoma patients, nivolumab and pembrolizumab monotherapy did not show any benefit in terms of patient survival [156]. Many clinical trials for immune checkpoint modulators in combination with chemotherapy, radiation, bevacizumab, or other treatment modalities are now underway [156]. Many other possible modulators have also been developed, such as those targeting indoleamine 2,3-dioxygenase (IDO). Patients with solid tumours or glioblastomas are being tested in clinical trials [157]. Immune checkpoint modulators have not been shown to be useful in the treatment of glioblastoma in general. They have, on the other hand, been shown to be safe and tolerated in therapeutic settings [156].

Antigen-capturing nanoparticles may boost the efficacy of immune-checkpoint inhibitors in the treatment of glioblastoma. These are nanoparticles with a surface modification that can bind tumour antigens. Non-covalent hydrophobic–hydrophobic interactions, as well as ionic or covalent interactions, generally alter the surface [158]. Min et al. created a poly(lactic-co-glycolic) acid-based nanoparticle. They demonstrated that different surfaces had variable antigen collecting capacities. Furthermore, poly (lactic-co-glycolic) acid and 1,2-dioleoyloxy-3-(trimethylammonium) propane showed the best ability to bind tumour antigens. After that, the nanoparticles were administered into mice with melanoma who were receiving anti-PD-1 therapy. The antigens were successfully delivered to dendritic cells by the nanoparticles, with a total response rate of 20%. Overall, the study found that biodegradable and biocompatible nanoparticles can improve antigen presentation and survival rates significantly [159]. Zhang et al. created PD-1 receptor-expressing cell membrane vesicles that were also packed with an inhibitor of indoleamine 2,3-dioxygenase (IDO). After that, vesicles were introduced into animals with melanoma tumours. Combined therapy was found to be more effective than single therapy in reducing tumour growth and improving mouse survival [160].

Immune photothermal therapy aims to eliminate primary cancers as well as malignancies in many places. Immune checkpoint inhibitors in combination with plasmonic gold nanostars, which are used in photothermal therapy, were created by Liu et al. [161]. Light energy is efficiently converted into heat by gold nanostars. The therapy was put to the test in vivo on bladder cancer patients and showed encouraging outcomes. In general, combination therapy outperformed anti-PD-L1 monotherapy in terms of outcomes. The mice had a 40% survival rate and established long-lasting immunity against cancer cells [162]. Peng et al. generated NLG919/IR780 micelles with a size of less than 50 nm in another investigation. NLG919 is an IDO inhibitor, and IR780 can absorb light in the near-infrared spectrum. Micelles were given to animals with malignancies in their breasts. Primary tumours were successfully destroyed, and secondary cancers were stopped from growing, thanks to a combination of photothermal therapy and immunotherapy. T-reg activity was also reduced, whereas the presence of CD8+ T-cells increased [163].

Hollow gold nanoshells were packed together with anti-PD1 peptide in poly(lactic-co-glycolic acid) nanoparticles in a work by Luo et al. Photothermal therapy with gold nanoshells was used, and immunotherapy with anti-PD-1 was applied. The nanoparticles were then put into tumor-bearing mice. The mice were exposed to near-infrared light, which allowed the nanoparticles to release peptides. Later, CpG was added to a vaccine made of poly (lactic-co-glycolic acid), and the combination therapy caused dendritic cells to mature and produce cytokines. The therapy reduced the main tumour, stopped the growth of metastases, and prevented the formation of new tumours, which were all extremely positive outcomes [164].

Vaccine-based immunotherapy has primarily been explored in rodent animal models and has involved a variety of techniques, including glioma cell modification, dendritic cell application, peptide-based vaccinations, and a combination approach with various treatment modalities [165]. Mutant IDH, EGFRvIII, a panel of antigens, or even personally selected antigens are the most prevalent targets in glioblastomas. In glioblastoma, the EGFR gene is increased in 40% of cases, and exon 2–7 is deleted or mutated in more than 50% of cases [165, 166]. Because the mutant form of the protein lacks a ligand-binding domain, it has constitutive activity, which promotes cancer. Several kinases, including Src family kinases, can also activate the mutant receptor [166]. The altered amino-acid sequence has been discovered to be immunogenic, and a vaccine called rindopepimut has been produced to stimulate the immune system [167]. The vaccine showed promise in early clinical trials. The subsequent phase III clinical trial, however, failed to show any improvements in overall survival [168]. Patients with recurrent glioblastomas were given either control or rindopepimut in another clinical trial called ReACT (A Study of Rindopepimut/GM-CSF in patients with relapsed EGFRvIII-Positive Glioblastoma). The vaccine outperformed the control group, with a median survival of 12 months against 8.8 months [169]. The use of nanoparticles in vaccinations can improve their efficacy. They have the ability to shield the vaccine against degradation while also increasing APC absorption. Kuai and colleagues created nanodiscs using lipids and peptides obtained from high-density lipoprotein. The surface was then coated with antigen peptides and cholesterol. The nanodiscs were more effective in priming T cells in animals with melanoma tumours, and the impact lasted longer. Nanodiscs combined with anti-PD-1 therapy produced tumour regression in 88 percent of mice with tumour models, which was significantly higher than either of them alone [170]. Alternatively, the vaccination could be in the form of mRNA. Liu et al. synthesised lipid/calcium/phosphate nanoparticles that conveyed mucin 1 (MUC1) mRNA. The vaccine was subsequently combined with anti-CTLA-4 antibody and injected into animals with triple-negative breast cancer. The combined therapy had a better response than either therapy alone [171].

Nanoparticle platforms can be engineered to deliver tumour antigens, whole tumour cells, and chemotherapeutic or phototherapeutic agents in such a way that the host’s immune system is effectively and safely triggered against tumour cells. Nanovaccines provide a one-of-a-kind platform for the delivery of personalised tumour neoantigens and adjuvants, as well as the induction of robust immune responses against aggressive tumours. Approaches based on antigens and whole tumour cells may pave the way for personalized cancer vaccination and immunotherapy. Finally, building on recent advances in nanoparticle-based cancer immunotherapy, the field should aim for clinical translation and clinical efficacy as its ultimate goal. The regulatory, analytical, and manufacturing roadblocks that need to be overcome in order to accelerate the clinical translation of nanomedicine-based cancer immunotherapy [172].