Adoptive cell therapy (ACT) involving T cells derived from tumor-infiltrating lymphocytes (TIL) has the potential for both immunostimulatory and immunosuppressive cancer therapies [34]. However, ACT is still a barrier to a robust activation of the host immune system, the regulation of signaling pathways, and the maintenance of a progression-free state. The use of the nanoplatform can improve the production, application, and efficacy of T cell immunotherapy for a variety of cancer conditions [35].
2.2. Nanocarrier for Adoptive Cell Transfer (ACT)
Adoptive cell therapy (AC
T) i
nvolving T cells derived from tumor-infiltrating lymphocytes (TIL) has the potential for both immunostimulatory and immunosuppressive cancer therapies [35]. Howeversplatin,
ACT is still a
barrier to a robust activation of the host immune system, the regulation of signaling pathways, and the maintenance of a progression-free state. The use of the nanoplatform can improve the production, application, and efficacy of T cell immunotherapy for a variety of cancer conditions [36].
Cisplatin, also lso known as cis-diamminedichloroplatinum (II) (CDDP), is an effective cancer drug in clinical trials
[37][36]. The effectiveness of cisplatin in inhibiting tumor growth has been established; however, its organ toxicity presents a significant challenge. Yao and his colleagues utilized the CDDP drug-loaded polyethylene glycol (PEG)–polyglutamate block copolymer micelle nanoparticles (CDDP-NPs) for antitumor immune response
[38][37]. The longer retention time of the CDDP-NPs in the TME upregulates the major histocompatibility complex class I (MHC-I), leading to the activation of the amyloid precursor protein (APP) pathway. The DCs are attributed to the interaction between the T cell receptor (TCR) and the peptide it recognizes by the APP (
Figure 4). Thus, the CDDP-NPs indirectly activate the tumor antigen-presenting CD8
+ T cell through the TCR signaling pathways. The OX40 is a tumor necrosis factor receptor superfamily (TNFRSF) domain that acts as a costimulatory antigen molecule expressed in the CD8
+ T cells
[39][38]. Therefore, the use of CDDP-NPs along with the OX40 agonists (aOX40) had a remarkable therapeutic effect in inducing T cell infiltration in the tumor environment. The promotion of aOX40 would activate the proinflammatory cytokines and secrete TNF-α, IFN-γ, and IL-2 for killing the tumor. Immunotherapies utilizing CDDP-NPs remain in the preclinical phase of development. It is crucial to analyze the efficacy of nanomedicine in the clinic to determine the possible role of T cell infiltration in the tumor.
Figure 4. Schematic illustration which depicts the mechanism of ACT using various nanocarriers. The nanocarriers, such as lipid-based nanoparticles, nanodiscs, or core–shell nanoparticles are coloaded with immune drugs, antibodies, and adjuvants for active cancer immunotherapy. The immune activation of the dendritic cells contributes to immunological responses to the TME by secreting IFN-γ, which is promoted by the effector activities of CD8+ T cells to cause tumor death.
Tumor resistance can be developed through the stimulation of the innate immune system. The development of active nanocarriers facilitates binding with the innate immune system to regulate “danger signals”. The activation of danger signals at the tumor site by Toll-like receptors such as retinoic-acid-inducible gene I (RIG-I), nucleotide-binding oligomerization domain (NOD), and stimulator of interferon genes (STING) improves T cell response
[40][39]. Current clinical research indicates that natural ligands for STING and cyclic dinucleotides (CDNs) are effective agonists for inducing potent antitumor immunity. CDNs are susceptible to nucleases and impermeable to cell membranes, which hinders their systemic delivery. Irvine et al. formulated PEGylated lipids conjugated with CDNs that self-assemble in lipid nanodiscs (LNDs)
[41][40]. Discoid-shaped nanoparticles (LNDs-CDNs) are optimal for intravenous delivery and show effective penetration within the tumor model that leads to tumor necrosis.
Effective cancer cytosol penetration of CDN-loaded lipid nanomaterials triggers antitumor immunity through CD8
+ T cell and natural killer (NK) cell activation
[42][41]. STING activation pathways trigger NK cells to produce interferon γ (IFN-γ), promoting PD-1 expression in tumor cells
[43][42]. However, the data from studies implies that a single dose is insufficient to activate NK cells
[44][43]. Therefore, a combination of PD-1 antibody with the CDN agonists loaded in lipid nanoparticles has an antitumor impact in lung metastasis under multiple-dose cycles. Ferroptosis is an iron-dependent form of apoptosis for tumor suppression. Cancer cells undergoing ferroptosis also trigger IFN-γ, which promotes the CD8
+ T lymphocytes in the TME. The expression profile analysis identified miR-21-3p as the highly upregulated microRNAs that regulate ferroptosis. Chunying Li’s group examined the anti-PD-1 immunotherapy impact of miR-21-3p-loaded gold nanoparticles in a preclinical tumor model
[45][44]. T-cell-adoptive cancer immunotherapies can be improved by integrating the nanosystem loaded with the immune drugs.
2.3. Nanocarriers for Cancer Vaccine
Cancer vaccines generally use tumor-associated antigens (TAAs) and tumor-specific antigens (TSAs) to boost the patient’s immune system. Therapies involving TSAs or neoantigens selectively expressed in the tumor have been at the forefront of cancer immunotherapy. Vaccines based on neoantigens have the potential to circumvent central immune tolerance and activate tumor-specific T cells
[46][45]. Sipuleucel-T (Provenge
®) and talimogene laherparepvec (IMLYGIC
®) are some of the DCs-based cancer vaccines currently in phase I clinical trials
[47,48][46][47]. However, poor targeting of the neoantigen-based cancer vaccines results in a low affinity to the TCR, making it incapable of mediating an effective antitumor response. Combining the NPs platform with the neoantigen-targeted vaccine delivery has therapeutic potential in cancer immunotherapy.
Jadidi and colleagues were the first to report that the combined suppression of lymphocyte-associated gene 3 (LAG3) and PD-1 by DC vaccines improves anticancer efficacy in the TME. LAG3 is an inhibitory receptor generated by immune cells to trigger T cell dysfunction
[49][48]. Initiating immunosuppressive responses and promoting the proliferation of cancer cells, LAG3 promotes the development of cancer
[50][49]. Specific siRNAs and LAG3/PD-1 antibodies were loaded onto chitosan–dextran sulfate–lactate (TMC-DS-L) nanoparticles, which led to increased IFN-γ production at the tumor site
[51][50].
The primary obstacles in cancer immunotherapy are multiple drug resistance (MDR) and the inadequate accumulation of cancer vaccines in the TME
[52][51]. Yao et al. developed a zwitterionic polymer employing poly (carboxy betaine methacrylate) (PBCMA) as a polymer shell over mesoporous organo silica nanoparticles (MONs) to overcome MDR in the TME
[53][52]. PCBMA is loaded with redox-responsive sulfur dioxide (SO
2), prodrug molecules (DN 2,4 dinitrobenzene-sulfonyl chloride), and chemotherapeutic drugs (DOX, doxorubicin) to treat MDR cancer effectively. The downregulation of P-glycoprotein in the presence of SO
2 makes cancer cells more susceptible to chemotherapy-induced apoptosis. PCBMA increases the nanomedicine’s intratumor accumulation, resulting in a 94.8% reduction in tumor growth. The redox-responsive SO
2 sensitizes cells, which aids DOX in prolonging the apoptosis in the TME.
Preclinical immuno compatibility development requires the controlled activation of innate immunity
[54][53]. Biopolymers (proteins, nucleic acids, collagen, chitosan, etc.), synthetic polymers (polystyrene, poly (lactic-co-glycolic acid) (PLGA), and poly (amino ester) (PBAEs)), and stimuli-responsive polymers loaded with immunoadjuvants have MDR capabilities that promote immunological activity. These polymers enable multi adjuvant synergy in cancer immunotherapy by stabilizing drug–cargo transport and activating proinflammatory cytokines. Thus, the camouflage of polymeric nanoparticles for the delivery of cancer vaccines provides an efficient platform for cancer immunotherapy (
Figure 5).
Figure 5. The cancer vaccination nanoparticles were camouflaged for specific functions in the TME. Nanovesicles containing a cancer vaccine comprised of a variety of antigens and biomolecules are being developed for use in cancer immunotherapy.
2.4. Nanocarriers for Immunogenic Cell Death (ICD)
Immunotherapy is a treatment method to eradicate cancer cells with a high degree of specificity and minimal side effects while preventing their recurrence. Chemotherapy, photothermal therapy (PTT), radiotherapy, and reactive-oxygen-species (ROS)-mediated therapies can induce immunogenic cell death (ICD), which is used to improve cytotoxic-based antitumor immunity. Cancer immunotherapies have had limited success in ablation treatment due to the development of local and systemic immunosuppression and immune evasion. Local radiation therapy in the TME destroys cancer cells by activating the immune system
[55][54]. When radiation and immunotherapy are combined on a nanoplatform, they have the potential to enhance the overall therapeutic efficacy
[56][55]. These methods have the potential to improve patient outcomes, but they encounter challenges in optimizing the radiation dose, toxicity, and timing of combined therapies
[57][56].
Chemotherapeutics can induce ICD and release tumor-specific antigens that are effective against numerous types of cancer
[58][57]. Combining chemotherapeutics and immune adjuvants is a viable method for achieving synergistic therapeutic benefits. Deng et al. reported a nanocarrier composed of liposomal spherical nucleic acids (SNAs) and FDA-approved 1,2-dioleoyl-sn-glycerol-3-phosphoethanolamine (DOPE) for enhanced cellular absorption and stability against nucleases
[59][58]. Conjugating chemotherapeutics such as doxorubicin (DOX) with DOPE triggered the ICD (DOPE-DOX) to secrete tumor-specific antigens. CpG oligodeoxynucleotides (CpGs) and matrix metalloproteinases-9 (MMP-9) are immunostimulatory reagents (DOPE-MMP-CpG) that amplify the immune response and promote immune cell penetration into the TME, respectively. Tumor cell MMP-9 and glutathione stimulated lipid-encapsulated SNAs to release DOX and CpGs into the TME. However, immunosuppression and cytotoxic side effects continue to restrict the use of these nanocarriers.
Yibru et al. developed a pH-responsive polyamidoamine (PAMAM) dendritic nanoparticles into the copolymer hydrogel (PCLA-PEG-PCLA) for the codelivery of DOX (PAMAM-DOX). PCLA-PEG-PCLA (poly(caprolactone-co-lactide)-poly (ethylene glycol)-b-poly(caprolactone-co-lactide) is a thermo reversible polymer ability to integrate with PAMAM-DOX nanocarriers for targeted drug delivery. At body temperature, PAMAM-DOX dendritic nanocarriers form a gel and facilitate a sustained DOX release in the TME. The combination of the immune activation with various cancer ablation techniques enhances the death of tumors. IND coupled with PAMAM-DOX also promotes the activate NK cells to attack tumor cells. However, immunological adjuvants in combination with chemotherapy remain resistant in treating some forms of cancer, especially triple-negative breast cancer (TNBC).
The photothermal immunotherapy (PTT) technique has also been demonstrated to reduce tumor development and enhance immune response. However, PTT efficiency in clinical applications is hindered by its poor stability, low therapeutic potency, and loss of affinity in the multistep delivery carrier synthesis
[60][59]. A research team led by Zou developed a mesoporous carbon nanocomposite (MCN) loaded with IR792 a near-infrared (NIR) laser dye (IR792-MCN)
[61][60]. Photothermal immunotherapy using NIR laser irradiation is improved by combining the PD-L1 antibody with the nanocarrier (IR792-MCN@ICB). The delivered IR792-MCN@ICB irradiated at 808 nm efficiently kills tumor cells by inducing DC maturation and secreting cytokines. PD-L1 gene silencing in conjunction with photothermal immunotherapy promotes tumor-infiltrating CD8
+ and CD4
+ T cells, which reduces tumor growth and prevents cancer metastasis. Cancer immunotherapy based on ICDs in combination with inhibitors as adjuvants plays a significant role in determining the effectiveness of personalized therapy (
Figure 6).
Figure 6. Schematic illustration of immunogenic cell death mediated by targeted nanocarriers conjugated with stimulating molecules such as immunological adjuvants and agonistic antibodies. The combination of immune activation with various cancer-ablation techniques enhances the death of tumors.