Advancements in the use of cancer nanovaccines: Comprehensive insights with focus on lung and colon cancer

3.1 Immunotherapeutic nanovaccine

A recent study has successfully created an in situ cocktail vaccination by using a cationic peptide that has been modified with cholesterol (DP7-C). The nanovaccine, consisting of small interfering RNAs (siRNAs) and cytosine-guanine oligodeoxynucleotides (CpG ODNs), triggers tumor cell death, enhances antigen presentation, and mitigates immune suppression inside the tumor microenvironment (TME). It has been tested on mice with colon carcinoma 26 (CT26) and B16F10 tumor models. This treatment specifically targets the main tumors, stimulates a systemic immune response against tumors, and prevents the spread of cancer to other parts of the body. Significantly, the nanovaccine transforms cool tumors into hot tumors, hence increasing their immunogenicity. Moreover, it enhances the immune response to anti-PD-1 treatment, indicating its promise as a flexible tool for cancer immunotherapy [59]. In another study, the use of cocktail vaccination through an animal model was investigated, which utilized diblock copolymers. The copolymers are formed of two distinct blocks. The first block is mostly made up of poly (ethylene glycol) and is utilized for antigen conjugation. The second block is pH-responsive and is responsible for packing nucleic acids. This architectural design allows for quick exit from endosomes into the cytoplasm. The work utilized a double-stranded RNA (dsRNA) analogue polyinosinic: polycytidylic acid (PolyIC), a sophisticated nucleic acid adjuvant, to showcase the amplified enhancement of antigen cross-presentation, co-stimulatory molecule expression, and cytokine secretion by DCs. The immunization platform greatly enhanced the accumulation of antigen and polyIC in nearby lymph nodes, resulting in a considerable improvement in CD8+ T cell responses, exceeding the efficacy of traditional antigen and polyIC combinations [60].

3.2 STING agonist-based nanovaccine

The stimulator of interferon genes (STING), an endoplasmic protein intricately associated with the endoplasmic reticulum, assumes a pivotal role in the orchestration of immune responses. Primarily recognized for its regulatory influence on the transcriptional dynamics of diverse immune system-related genes, STING emerges as a crucial mediator in the innate immune reactions directed against bacterial and viral agents [61]. Upon the detection of cytolytic DNA by cytosolic cyclic GMP-AMP synthase (cGAS), STING activation ensues. Subsequent to its activation, STING effectively facilitates the synthesis and release of type I interferons (IFNs) and proinflammatory cytokines. This orchestrated response serves as a foundational mechanism in the initiation of inflammatory pathways, integral to the clearance of pathogenic entities [62]. STING plays a pivotal role in adaptive immunity, particularly post-administration of DNA vaccines. CD8+ DCs, operating via the STING pathway, generate type I IFN, fostering antigen cross-presentation and priming CD8+ T cells, thereby enhancing adaptive immune responses [63]. Furthermore, STING’s relevance extends to tumorigenesis, where tumor-derived STING-activating components are identified by B cells and CD11b + tumor-infiltrating APCs. This recognition induces the release of STING-mediated type I IFNs by leukocytes, facilitating the priming of cytotoxic NK cells for targeted eradication of neoplastic entities [64].

A study involving the development of a simulated nano-platform that can simultaneously impede the alternative T-cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain (TIGIT) checkpoint and activate the STING signaling pathway has been reported. The production involved the fusion of a red blood cell membrane with liposomes that contained cascade-activating chemoagents (β-lapachone and tirapazamine), together with a detachable TIGIT block peptide known as RTLT. Within the TME, the peptide is selectively generated to counteract T-cell exhaustion and reinstate the body’s capacity to battle cancer proliferation. The step-by-step initiation of chemotherapeutic medicines causes harm to DNA and obstructs the mending of DNA with two strands, leading to the strong activation of STING at its initial position to promote a powerful immune response. The RTLT effectively inhibits the growth of tumors that are unresponsive to anti-PD-1 therapy and hinders the dissemination of cancer cells and the recurrence of tumors by promoting the generation of immunological memory that specifically targets antigens [65]. However, this study is in preclinical stage and only 18 studies are reported at the clinical level [66].

3.3 Nanogels

It is possible to create NPs (size: 20–200 nm) that are potential enough to be used as immunotherapeutic agents, and drug delivery systems from either natural or synthetic polymers (chitosan, alginate, and polyacrylic acid) by crosslinking hydrophilic polymer networks, which result in 3D NPs known as Nanogels [67,68]. Nanogels offer substantial advantages over traditional organic or inorganic NPs commonly used in drug delivery systems, owing to their inherent properties derived from the polymers used in their synthesis. Their key features include the ability to adjust their size, a large surface area facilitating multivalent conjugations due to numerous exposed functional groups, high loading capacity, biodegradability, biocompatibility, and stability [69].

Furthermore, research suggests that these NPs exhibit immunological activity due to their physicochemical properties, enabling them to target specific cells and cellular compartments effectively together with this they also serve as efficient carriers by preventing degradation of vaccine and its subunits from in vivo degradation [68]. A total of 13 vaccine candidates utilizing nanogel-based formulations have been understudy yet. These candidates are in various stages of clinical trials, with most of them in Phase I trials. Specifically, 10 out of the 13 candidates are in Phase I clinical trials, while the remaining 3 candidates have progressed to Phase I & II trials. There are no vaccine candidates listed in Phase 2 or later stages of clinical trials [70].

Availability of various methodologies, viz., photoreaction, radical polymerization, click chemistry, and the Schiff-base reaction for synthesizing nanogels, allows precise control over their dimensions, shapes, deformations, and surface chemistries. The physicochemical stability of nanogels is affected by the degree of polymerization, which is itself dictated by the restricted polymerization of monomers with covalent bonds between them. Most of the time, they hold up well throughout a wide range of temperatures and pH levels. While chemically cross-linked nanogels have covalent cross linking, nanogels that are physically cross-linked are created when polymer chains are allowed to self-assemble via noncovalent linkages. Their stability is compromised when exposed to variations in temperature, pH, or ionic strength. Electrostatic interactions and Van der Waals forces (such as hydrogen bonds and hydrophobic interactions) are common ways for these nanogels to be crosslinked. In pre-clinical settings, experimental vaccines based on nanogels have shown encouraging results, including increased rates of animal survival, reduction of tumor growth, and activation of CD8+ T cells [71]. A temperature-responsive hydrogel incorporating doxorubicin (DOX), IL-2, and IFN-γ medications was developed, demonstrating enhanced efficacy against B16F10 melanoma tumors by inducing cancer cell apoptosis and promoting CD3+/CD4+/CD8+ T cell proliferation [72]. Some hormone therapy increases the risk of diabetes mellitus and blood clots, yet they are beneficial for hormone-associated malignancies. Nanogels developed for targeted medication delivery to various cancer types, on the other hand, do not present these hazards. Many cancers, including those of the breast, liver, prostate, and lungs, have responded well to loaded nanogels, especially DOX formulations including chitin.

Conventional cancer immunotherapy may inadvertently heighten toxicity to healthy cells. A potential answer has been found through the production of protein nanogels. In order to provide targeted immunotherapy using chimeric antigen receptor (CAR) T-cells, these nanogels were manufactured with precision. By reacting to the activation of T-cell receptors, the nanogels optimally release CAR T-cells into the TME. This kind of regulated release improves the effectiveness of the treatment while reducing the likelihood of side effects highlighting the opportunity for nanogels to transform T-cell immunotherapy by offering a more secure and efficient method of treatment [73]. Acknowledging the inherent constraints of traditional cancer treatments, such as the suppression of blood vessel growth, absence of specificity, and harm to neighboring cells, researchers are now exploring a nanogel system that is both biodegradable and pH-sensitive. This technology is being investigated as a medication nano-carrier for combinational chemotherapy and radiotherapy. A durable and consistent nanogel through the self-assembly of carboxymethyl cellulose and bovine serum albumin, and successfully loading it with radionuclide^131I and camptothecin was developed to enhance drug delivery efficiency. The result indicated 16.72 wt% with biocompatibility and limited hemolysis [74,75]. In addition, Lingyu et al. investigated the safety and effectiveness of nanogel carrier, particularly when used alongside radiation therapy in the aim developing a dual function contrast agent for magnetic resonance imaging (MRI) and intraoperative optical imaging for glioma detection. This was accomplished by creating a pH and temperature-sensitive polymer known as poly(N-isopropyl acrylamide co-acrylic acid) conjugated with Cy 5.5-labeled lactoferrin and coated with Fe₃O₄ NPs [75].

Tumors of the central nervous system (CNS) present diverse malignancies like gliomas, meningiomas, and medulloblastomas, each with distinct characteristics and treatment hurdles. Their location within the brain or spinal cord causes debilitating symptoms, complicating patient care and QOL. Nanogels hold significant promise for improving drug delivery in the treatment of CNS cancer due to their enhanced permeability across the blood-brain barrier (BBB), high drug-loading efficiency, non-toxic nature, specific targeting capabilities, and the growing body of research supporting their efficacy. Their ability to encapsulate drugs in a concentrated form, while being composed of biocompatible materials, ensures both efficacy and safety in treatment. Furthermore, nanogels can be tailored to target specific cells or tissues within the CNS, enhancing drug delivery to cancerous cells while minimizing systemic side effects [76].

3.4 Nanovaccines to support photothermal therapy

As a developing kind of anticancer therapy, photothermal therapy (PTT) involves eliminating tumors with heat to produce tumor-antigens along with additional immunogenetic signals, thereby activating antitumor immune responses. Several photothermal agents have been created to trigger immunogenic cell death (ICD) in tumors. This falls under the category of carbon based, noble metal nanomaterials, cyanine-based, porphyrin-based, polymer-based nanomaterials. For photothermal tumor targeting, CuS NPs with a strong near-infrared II (NIR-II) absorption characteristic is used as it may penetrate deep tissues and have high photothermal conversion efficiency. The carrier works in a way in which laser irradiation can cause local hyperthermia of tumor accumulation, which can trigger ICDs, and activating tumor-associated antigens (TAAs). This stimulates the expression of damage-associated molecular patterns, and produces pro-inflammatory factors. This environment is ideal for maturing DCs, which in turn activate cytotoxic T lymphocytes (CTLs), that remove the tumors [77–79].

An innovative approach involved the utilization of surgical tumor-derived cell membranes (CMs) to cover mesoporous polydopamine NPs, which were then filled with resiquimod (R848). This nanovaccine, known as MR@C, was developed for precise tumor photothermal immunotherapy and prevention. It showed remarkable effectiveness in imaging-guided photothermal immunotherapy, successfully eliminating solid tumors when subjected to NIR laser irradiation. In addition, it suppressed the growth of metastatic tumors by triggering strong immune responses against the cancer cells, especially when used in conjunction with a PD-L1 therapy. Efficiency of vaccine to prevent recurrence of 4T1 cells was proved through the prophylactic testing of the case in which the success was 100% [80]. There was a study of photothermal immunotherapy on glioblastoma (GBM) mice that used microorganisms as a medication delivery system. Microbes that have been fed glucose polymer are utilized in this scenario, together with photosensitive indocyanine green (ICG) silicon NPs. The BBB was effectively permeable, allowing the bacteria administered intravenously to GBM animal models to infiltrate and cause damage to GBM cells. Photothermal effects produced by an 808 nm laser beaming down on ICG destroyed both cancer cells in the immediate vicinity and microorganisms. This germ debris and antigen was reported to stimulate the immune system providing greater probability of survival [81].

An alternative strategy for enhancing both biosafety and immunotherapeutic efficacy for solid tumors was developed by selecting photothermal and weak-immunostimulatory porous silicon@Au nanocomposites as particulate cores to prepare a biomimetic nanovaccine. In another study, the usage of weak immunostimulatory agents based on a photothermal approach were employed to develop highly efficient vaccines for solid tumors. The study reported the absence of reoccurrence and 100% survival in the mice, which justifies the efficiency of this alternative approach [82]. Information on the classification of nanovaccines with additional details are listed in Table 2.

4.1 Protein-based nanocarriers

Protein-based nanocarriers stabilize nutraceutical, diagnostic, and therapeutic substances better than other delivery methods. These nanocarriers are popular for pharmaceutical delivery since they are safe and perishable. Proteins are unique in their bioavailability, biodegradability, antigenicity, nutritional value, abundance, and binding ability for many chemicals used in nutrition, diagnostics, and medicine. Protein NPs can be solid spherical, nanotubes, nanogels, nanocages, or plate-shaped. When these nanocarriers create intricate three-dimensional networks with the encapsulated medicines, reversible protection and precise target delivery are possible. Nanocarriers can be made from organic proteins. Zein, gliadin, soy, and lectins are plant proteins; gelatin, collagen, albumin, milk, silk, and elastin are animal proteins. These nanocarriers can be synthesized by electrospraying, self-assembly, nanoprecipitation, emulsification, desolvation, and co-acervation [96].

A novel biosynthetic vaccine containing an unfolded protein nanocarrier was developed for loading and delivering Etoposide DNA damage-inducing agent for cancer therapy in rats. The medicine that was nanoformulated showed four times the loading effectiveness of the original, had a half-life of 17.6 h, and released Etoposide in a regulated manner over 6 days. Better solubility and cellular internalization are thought to be responsible for the noticeable improvement in therapy. There were negative toxicological consequences, including damage to the kidneys and liver, and the nanocarrier exhibited less immunogenicity [97]. In recent years, important international organizations have approved Abraxane, a treatment that consists of albumin NPs encapsulating the anti-cancer chemical paclitaxel. Drug delivery experts have taken notice of its remarkable yearly development and effectiveness in curing several cancer kinds [98,99].

4.2 Liposomes

Liposomes are closed spherical structures made of phospholipids, consisting of a bilayer with an inner core of water. They have the special capacity to enclose hydrophobic substances in their lipid bilayer and hydrophilic substances in the inner water compartment [100]. Liposomes are a potential option for delivering medicines and vaccines due to their versatility, biocompatibility, biodegradability, and low/nontoxic properties. Liposomes can include both water-loving (hydrophilic) and water-repelling (hydrophobic) substances. This allows for the administration of two antigens at the same time and improves the ability to dissolve substances that are not easily soluble in water. In addition, they provide a regulated and prolonged release of enclosed antigens, enhancing resistance to degradation. Liposomes, which may be chemically modified to bind ligands, can enhance the duration of circulation in the body, minimize unintended side effects, and display several copies of epitopes [101]. Liposomes’ particle form facilitates the cross-presentation of antigens, which is essential for the production of antigen-specific cytotoxic T cell responses [102].

Liposomes exhibit effectiveness against many diseases, triggering strong immune responses including both antibodies and cells. The encapsulation of antigens within liposomes enhances their ability to be captured by APCs due to their bilayer scaffold particle structure. This distinctive characteristic enables the processing and presentation of antigens through MHC molecules, leading to the activation of T cells. As a result, both innate and adaptive immune responses are initiated [103]. In addition, liposomes have a depot effect, which means they can retain antigens for a long time and release them slowly. This leads to both T-helper 2 responses and a prolonged T-helper 1-dependent immune response. This is especially useful in protecting against intracellular pathogens, where relying solely on antibody-based immunity may not be enough [104].

Current research and clinical trials involving liposomal vaccines for cancer immunotherapy are at various stages of development. Several studies have demonstrated promising results in preclinical and early-phase clinical trials, indicating the potential of liposomal vaccines in the treatment of cancer. As of march 2024, a total of 35 studies are reported for clinical studies. A count of 5 studies is in phase 3 stage. 14 studies have been completed with result. In which majority of the studies include treatments with Tecemotide (L-BLP25) for various cancers including prostate cancer, small cell lung cancer, NSCLC and multiple myeloma [105].

A study investigating the impact of the BLP25 liposome vaccine (L-BLP25) on patients diagnosed with stage IIIB and IV NSCLC unveiled significant findings. According to the analysis, patients administered L-BLP25 exhibited a median survival time of 4.4 months longer than their counterparts who received best supportive care (BSC). Notably, patients in stage IIIB with locoregional (LR) cancer experienced particularly favorable outcomes. The median survival time for the L-BLP25 group exceeded that of BSC, boasting an adjusted hazard ratio of 0.524 (95% CI, 0.261–1.052; P = 0.069). Importantly, the study highlighted the vaccine’s safety, with no severe toxicity observed. Furthermore, patients in the L-BLP25 cohort consistently demonstrated an improvement in health-related QOL. Further an updated survival analysis was given by the researchers indicating survival time for patients diagnosed with stage IIIB/IV NSCLC was notably extended when treated with L-BLP25 in combination with BSC compared to those receiving BSC alone. The most significant difference in survival outcomes was observed in patients specifically diagnosed with stage IIIB LR disease. This suggests a potential benefit of using L-BLP25 in improving survival rates, particularly for patients with stage IIIB LR NSCLC, highlighting the potential efficacy of the treatment in enhancing overall patient outcomes in this specific subgroup [106,107].

4.3 Polymers

Polymeric nanoparticles (NPs), which are solid colloidal systems, can be synthesized using various techniques that typically produce particles ranging in size from 10 to 1,000 nanometers. These processes include salting out, antisolvent, nanoprecipitation, solvent evaporation/extraction, and emulsification that result in the formation of nanocapsules or nanospheres [108]. Nanocapsules use a polymeric membrane to encase pharmaceuticals in a cavity, whereas nanospheres encase medications in a polymeric matrix [109]. NP Polymer synthesis uses both natural and synthetic ingredients. Natural materials including chitosan, gelatin, alginate, dextran, heparin, collagen, albumin, and polyhydroxyalkanoates are superior, but they are difficult to extract and have short supply. As an example, chitosan is a naturally occurring polymer that is both biocompatible and biodegradable; it comes from marine creatures [108,110].

Chitosan is one of the most well-known natural polymers used in vaccine distribution, while synthetic polymers also play a role. Chitosan helps antigens release slowly because of its bioadhesive nature and strong cationic charge [111]. Notably, it may electrostatically bind with anionic nucleic acids to produce strong complexes [112]. The bioadhesive property of chitosan allows antigens to stay in touch with mucosal surfaces for longer, in-turn continuing to stimulate immune cells. Because of its unusual mix of properties, chitosan shows promise as a vehicle for the administration of mucosal and nucleic acid vaccines. The effectiveness of encapsulating inactivated influenza virus antigens in chitosan-based NP vaccines was proven in the research by Sawaengsak et al. When given two doses of this vaccine intravenously, mice showed an increase in the production of antibodies specific to the antigen and IFNγ + T cells. Notably, this resulted in a 100% protection of vaccinated mice against influenza virus infection [112].

Nanoscale coordination polymers (NCPs), characterized by their adjustable compositions, belong to a category of hybrid nanocomposites created through the combination of metal ions and organic ligands [113]. Recently a novel hydrogel nanocomposite based on organic polymers (polyacrylic acid, polyvinyl pyrrolidone), and inorganic polymer (molybdenum disulfide) was developed for a pH-responsive and a controlled release of 5-Fluorouracil in cancer treatment [114].

In yet another study, a nanocomposite to upgrade quercetin’s (QC) limitations viz., stability, solubility, and bioavailability was developed for cancer therapy. This composite included natural polymers like starch and chitosan and graphene quantum dots and titanium dioxide. The researchers demand that the porosity and biocompatible optimized nanocomposite, enables controlled, pH- and temperature-sensitive release of QC an antioxidant and a potential anticancer compound. An enhanced cytotoxic effects was also reported by the authors when they conducted a cell line test on A549 lung cancer cells, which further support its potential in targeted lung cancer treatment [115].

The nanocarrier demonstrated superior drug loading efficiency, stability, and enhanced anticancer activity, as confirmed through various characterization techniques and cellular experiments. In another study, an organic ligand called meso-2,6-diaminopimelic acid (DAP) as well as NCP generated between Mn²⁺ ions were used to prepare a vaccine. These novel OVA@Mn-DAP NPs include a model protein antigen called ovalbumin (OVA). A combination of increased cellular absorption of the antigen and DAP-stimulated Nod1 pathway maturation enhances antigen cross-presentation and DC maturation. Vaccination with OVA@Mn-DAP provides significant advantages in the treatment of existing tumors as well as prevention against newly developed B16-OVA tumors. The OVA@Mn-DAP vaccination has a synergistic impact, leading to significant suppression of tumor development, when it is coupled with αPD-1 immune CPI treatment [113].

In contrast, synthetic materials such as cyclodextrins, poly(lactic-coglycolic acid; PLGA), poly-n (cyanoacrylate), polycaprolactone), polyethylene glycol (PEG), and others are easy to work with but do not break down very well in nature. Two synthetic materials that have been authorized for use in biomaterial medicines by the US FDA are PLGA and albumin. Medications can be safely delivered to solid tumors using human serum albumin, which is plentiful in the bloodstream and acts as a glutamine catabolic source. With a retention duration of one month or more in vivo, PLGA was found to be useful for tissue engineering repairs [116]. The various nanocarriers employing till today are depicted in Figure 2.

Figure 2

Various types of nanocarriers employed for efficient transport of embedded drug and targeted delivery.

4.4 Exosomes

Every kind of cell releases EVs to take part in important activities including inflammation, cell proliferation, and immunological response by transferring molecular information between cells [116]. The EVs play important roles in healthy bodily processes, viz., the development of cancer and a host of infectious cancers. EVs’ ability to carry a wide variety of molecules to adjacent or faraway locations is a defining characteristic that allows them to modulate a wide range of biological activities. Adaptable delivery mechanisms of EVs capacity to transport payloads to particular cellular sites for therapeutic action emphasize the potential for the creation of novel therapeutic approaches, including vaccination [117]. These EVs can be broadly categorized into several subtypes based on their biogenesis and size, with exosomes being one of them. Exosomes are typically smaller vesicles, ranging from about 30 to 150 nm in diameter, and are formed through the inward budding of endosomal membranes to form multivesicular bodies, which then fuse with the cell’s plasma membrane, releasing the exosomes into the extracellular space [118].

A combination therapy involves the designing and development of an antitumor vaccine for breast cancer. This method involved loading EVs that express α-lactalbumin (α-LA) with Toll-like receptor 3 agonist Hiltonol and neutrophil elastase, which induces ICD, through electroporation. The modified EVs were successful in stimulating DCs and thereby CD8+ in the TME [119]. Exosomes are being tested for stomach cancer diagnosis and prognosis in a Phase I clinical trial NCT01779583. In the particular study, circulating stomach exosomes are examined as prognostic and predictive indications in advanced gastric cancer patients. In a prospective cohort of advanced gastric cancer patients undergoing first-line chemotherapy, plasma gastric cancer exosome levels and dynamics is examined for prognostic and predictive value. The study reports that exosomes present at the plasmatic level of cancer patients carry recognized tumor markers such as PSA and CEA, as well as more enzymatic activity and nucleic acids than those found in healthy persons [120]. In another study, exosomes were assessed for their effects on tissue toxicity and tumor growth, and compared them to ordinary DOX for breast and ovarian cancer. The results demonstrated that exosomal DOX (exoDOX) minimized cardiac toxicity by restricting regular DOX accessing the heart, allowing greater dosages and improved tumor therapy outcomes [121]. There are currently 80 clinical trials reported. Among these, 19 studies have been completed, and 2 studies are under Phase II level. None of the studies are in Phase IV emphasizing the necessity of advancement of research in this area [122].

5.1 Tumor antigens

Many human malignancies create antigens that can be discharged into the circulation or stay on the cell surface. Detecting these antigens allows the immune system to target their elimination, highlighting the potential for immunotherapy in cancers like kidney, breast, prostate, lung, and colon cancers and also in Burkitt lymphoma and neuroblastoma [7,123], these antigens are either tumor associated antigens (TAAs) or tumor specific antigens (TSAs) based on the parental gene expression pattern. Oncoviral and somatic mutation-derived neoantigens are overexpressed are considered TSAs, while TAAs are self-antigens overexpressed in tumors. Overexpressed proteins including RAGE-1, EGFR, hTERT, p53, mesothelin, MUC-1, and carbonic anhydrase IX are commonly seen in tumor protein profiles as they are considered as universal antigens of persons with similar cancer [124–126]. These proteins are attractive targets for cancer treatment techniques because of their important roles in cancer cell survival and their resistance to downregulation processes. Cancer germline/cancer testis antigens (CTAs) are only expressed in human tumors of diverse histological kinds and lacking in normal somatic tissue except testis and placenta tissue. CTAs are interesting therapeutic targets because of their tumor selectivity and strong immunogenicity due to the absence of immune tolerance [127].

5.2 Peptide antigens

To target tumor-specific or TAAs, nano-cancer vaccines use peptide antigens, which are short chains of amino acids. Better stability, transport, and activation of the immune response by inducing de novo antitumor T cell responses in cancer patients against cancer cells are achieved by encapsulating or conjugating these peptides with NPs. Nano-cancer vaccines, which use peptide antigens, may provide a more precise and efficient method of cancer immunotherapy by training the immune system to identify and destroy cancer cells [71]. A number of multi-epitope formulations have recently emerged as peptide vaccines, which are renowned for their capacity to elicit strong immune responses; this is particularly true in the field of cancer immunotherapy. By combining peptides from the early proteins viz E5 to E7, a new multi-epitope vaccination (E765m) that targets human papillomavirus type 16 is developed, which in turn resulted in the production of chimeric VLPs termed HBc-E765m [128]. Several tumor peptide vaccines have undergone extensive clinical trials across a spectrum of cancer types. Among them, five have been completed, which are in Phase III. In breast cancer, Nelipepimut-S (NP-S) completed a Phase 3 trial (NCT01479244), showcasing its potential as a therapeutic option. Metastatic melanoma witnessed trials of MDX-1379 targeting gp100, completing Phase 3 (NCT00094653) alongside gp100 alone, which also completed Phase 3 (NCT00019682), underscoring the diverse approaches in vaccine development [129]. Multiple myeloma saw investigation with MAGE-A3/NY-ESO-1 in a Phase 2/Phase 3 trial (NCT00090493), indicating interest in exploring peptide vaccines for hematologic malignancies. For esophageal cancer and gastric cancer, G17DT completed a Phase 3 trial (NCT00020787), emphasizing the extensiveness of applications for peptide-based immunotherapy. These trials collectively demonstrate ongoing endeavors to evaluate the efficacy and safety profiles of various peptide vaccine candidates in diverse cancer populations, reflecting a promising avenue in cancer treatment research [54,130,131].

5.3 Biologics

Biologics encompass a diverse array of molecules derived from biological sources or synthesized to mimic biological activity. This includes nucleic acids such as DNA and RNA, as well as proteins like monoclonal antibodies (mABs). Harnessing the unique properties of biologics as antigens in nanovaccines holds tremendous potential for enhancing anti-tumor immune responses and improving therapeutic outcomes in cancer patients. DNA vaccines present a number of advantages over conventional tumor vaccines, including a wider variety of tumor antigens, ease of preparation and storage, and the ability to induce or enhance long term adaptive immune responses against tumor cells expressing these antigens [132].

A phase I/IIa clinical trial has been reported to prove the efficacy of DNA vaccines in clearing HPV-16 cervical intraepithelial neoplasia and gave success results by treating half of the women subject who were given the conjugated therapeutic VB10.16 vaccine, which in turn was aimed to clear the target CCR5 (NCT02529930) [133]. A microencapsulated DNA vaccine termed ZYC101, which encodes numerous CTL epitopes specific to HPV-16 E7, is also reported through two separate phase I studies. Among the several clinical trials conducted, currently four studies are in Phase III level and one in phase IV [134].

DNA vaccines provide several advantages, including rapid production, elimination of the need to handle hazardous pathogens, thermal stability, and convenient storage and transportation at a little expense. One major issue with DNA vaccines administered by needles and syringes is their limited efficacy due to suboptimal cellular uptake of the DNA. Therefore, it is crucial to discover more effective and secure methods of administering medications [135]. Further, it is possible to successfully activate the immune system to recognize tumors using mRNA expressing particular tumor antigens or full-length tumor antigens. A potential new direction for cancer immunotherapy, these mRNA-based vaccines have advantages including great efficiency, safety, and cost-effectiveness [136]. As of March 2024, 55 clinical trials have been reported on the study of RNA vaccines against various cancers. Among the studies, 27 have been completed and 3 are in phase III level [137]. As a substitute for natural antibodies, monoclonal antibodies are man-made molecules. Their goal is to trigger activating receptor 4-1BB or CD40, alter, or mimic the immune system’s attack on cancer cells and other undesirable cells. Among the many roles that monoclonal antibodies play in cancer therapy the notable ones are the identification and elimination of cancer cells by activating the breakdown of CMs, the blockage of proteins that promote cell proliferation, and the prevention of blood vessel formation, which is crucial for tumor survival. In addition to directly attacking cancer cells, blocking immune system inhibitors such as CTLA-4, and delivering radiation or chemotherapy treatments to cancer cells while minimizing the harm to healthy tissues are possible with certain monoclonal antibodies. Additionally, some medications aid the immune system’s assaults on cancer cells by binding cancer and immune cells together using monoclonal antibodies [133].

8.1 Tumor antigens

Proteins that are expressed by cancer cells but are either absent or present at significantly lower levels in normal cells are known as TSAs or TAAs. Nanovaccines have the potential to transport these antigens to APCs, where they can trigger immune responses that target cancer cells. Commonly used tumor-associated proteins include HER2/neu, mutated variant of the EGFR (EGFRvIII), cancer-testis antigen (NY-ESO-1), melanocyte differentiation antigen (MART-1), and WT1 [164–166]. The range of targets that are of interest in target delivery for the development of sustainable nanovaccine is represented in Figure 3.

Figure 3

(a) Range of therapeutic targets for immunotherapeutic approach of nanovaccines and (b) the mechanism behind antigen cross presentation at tumor microenvironment and CD8+ T cell activation by dendritic cells and tumor apoptosis.

8.2 Neoantigens

Neoantigens are antigens derived from tumor-specific mutations or aberrant gene expression in cancer cells. Nanovaccines can target neoantigens unique to individual tumors, providing personalized immunotherapy. Neoantigen-targeting vaccines aim to overcome tumor heterogeneity and immune escape mechanisms. Advances in sequencing technologies have enabled the identification of neoantigens for vaccine development. Neoantigens can be made by viral open reading frames in cervical cancer with HPV and nasopharyngeal with Epstein-Barr virus. Neoantigens are only found in tumors and not in healthy tissues, which increase their specificity in targeting tumor cells. The ability to bypass negative selection of Thymus T cells makes more neoantigen-specific T cells, which boosts immune reactions against tumors. Hence, immunotherapy can increase neoantigen-specific T-cell reactions and improve immune memory after treatment, which may stop the recurrence [167,168].

8.3 Tumor-associated glycans

Aberrant glycosylation patterns on cancer cells can serve as targets for nanovaccines. Tumor-associated glycans, such as sialyl-Tn and Tn antigens, are overexpressed in various cancer types. Nanovaccines targeting these glycans aim to induce glycan-specific immune responses, leading to tumor cell recognition and elimination [169].

8.4 Immune checkpoints

Immune checkpoints, such as PD-1 and (CTLA-4), regulate immune responses and can be exploited by cancer cells to evade immune surveillance. Nanovaccines incorporating immune CPIs or targeting checkpoint molecules aim to enhance anti-tumor immunity by releasing the brakes on T cell activation [170]. Nanovaccines can also act as TME modulators target molecules involved in shaping the TME, such as cytokines, chemokines, and growth factors. By modulating the TME, nanovaccines aim to create an immunostimulatory conducive to anti-tumor immune responses while inhibiting immunosuppressive factors.

8.5 Heat shock proteins (HSPs)

HSPs are chaperone proteins that play a role in antigen presentation and immune activation. Nanovaccines can be designed to deliver tumor antigens complex with HSPs, enhancing antigen uptake and presentation by APCs and promoting anti-tumor immune responses by triggering T-lymphocytes [171].

8.6 DCs

The DCs are professional APCs that play a central role in initiating and regulating immune responses. Nanovaccines can target DCs to enhance antigen uptake, maturation, and activation, thereby amplifying anti-tumor immune responses. Strategies using nanovaccines include targeting DC-specific receptors or delivering the antigens/adjuvants directly to DCs [172].

8.7 TLRs

The TLRs are pattern recognition receptors that recognize pathogen-associated molecular patterns and activate innate immune responses. Nanovaccines can incorporate TLR agonists as adjuvants to enhance DC maturation, cytokine production, and T cell priming, leading to potent anti-tumor immunity [173].

11.1 Future directions

11.2 Challenges

When considering challenges, it includes ensuring safety and biocompatibility like any other treatment options involved in immune reactions, and achieving scalable, cost-effective production with stable and precise quality. However, the insecurity of NPs in exhibiting toxicity is still the main concern, due to the limitation in knowledge on nanomaterial interaction with the biological components. This is often associated with their nano size and large surface contact with biological systems[208]. Resilience of cancer cells to chemotherapy by rewiring their intercellular cascades and metabolism is another challenge that arises while manufacturing a biocompatible nanodrug [209]. Nevertheless, it also includes regulatory, ethical, and technical checkpoints, viz., adapting to tumor heterogeneity, patient immune specificity, and establishing a long-term efficacy. In conclusion, we would like to highlight the fact that even though nanovaccines provides a hope of promising approach, thorough and careful consideration of all the facts mentioned above will offer a potential therapeutical approach that will offer safer, more effective, and personalized treatment options in future.