Cancer remains the most formidable disease globally, with over 19,292,789 new cases and approximately 9,958,133 cancer-related deaths recorded worldwide each year (1). As is well-known, tumor cells primarily evade immune surveillance by downregulating tumor-associated antigens (TAAs) and tumor-specific antigens (TSAs), and releasing soluble antigens and MHC molecules (2). Therefore, tumor immunotherapy has emerged as a crucial therapeutic approach for suppressing both primary and metastatic tumors. Moreover, immunotherapy can confer long-term immune protection for the body (3). Immune checkpoint blockade (ICB) represents a novel groundbreaking tumor immunotherapy that targets two key immune checkpoint pathways programmed cell death protein 1/programmed death ligand 1 (PD-1/PD-L1) and cytotoxic T lymphocyte-associated protein 4/B7 (CTLA-4/B7). By disrupting the mechanisms of tumor immune resistance, ICB can effectively promote antigen-specific T-cell immune responses. Currently, more than ten ICB drugs have been approved by the FDA for the treatment of a broad spectrum of tumors, offering new hope in the fight against cancer (4). However, the efficacy of ICB drugs appears to be less than satisfactory against late-stage patients in relevant clinical trials, with only a few patients benefiting from these treatments (5).

Cancer vaccines represent a promising emerging approach in tumor immunotherapy, offering extensive application prospects (6). The complexity of the preparation process, coupled with insufficient antigenic immune effects and immune cell dysfunction, have emerged as the primary factors limiting the development of cancer vaccines (7, 8). Nonetheless, the identification of immunogenic cell death (ICD) as a distinct form of tumor-regulated cell demise has offered new prospects to overcome the limitations hampering the advancement of cancer vaccines (9). In this regard, the capacity of chemotherapy, radiotherapy, photothermal therapy, and sonodynamic therapy to induce ICD, as evidenced in recent studies, could present a novel approach for reshaping conventional methods in oncology (10). It is now understood that the importance of ICD-based cancer vaccines lies in the in vivo application of ICD nanomedicine inducers and the production of dying tumor cells (DTCs) in vitro during tumor treatment ( Figure 1 ).

ICD, induced by the chronic release and exposure of damage-associated molecular patterns (DAMPs) including calreticulin (CRT), adenosine triphosphate (ATP), high mobility histone 1 (HMGB1), heat shock protein (HSP) activates the recruitment and activation functions of neutrophils, macrophages, and dendritic cells. This orchestrated immune response associated within the tumor microenvironment exhibits characteristics akin to vaccination, a concept gaining significant traction within the research community (11). Simultaneously, during the study of ICD induction against tumor cells in vitro, it has been discovered that a substantial number of immunogenic DTCs are generated following ICD induction. These DTCs possess a strong ability to release immunogenic substances, such as DAMPs, which continuously trigger a potent immune stress response, remodel the immune microenvironment, and enhance the body’s immune surveillance capabilities. In summary, “ICD-based cancer vaccines” offer advantages such as broad-spectrum antigens and diverse induction conditions, which can mitigate numerous adverse factors in the development and application of cancer vaccines. Overall, the advent of ICD-based cancer vaccines has demonstrated significant potential for the immunotherapy of relevant tumors (12).

However, the pursuit of efficient and stable methods for ICD induction remains critical for developing and evaluating relevant ICD-stimulating nanomedicines. Since ICD inducers and induction strategies are key focuses in ICD-based cancer vaccine research, this review highlights recent advancements in ICD-based cancer vaccines from both in vivo and in vitro perspectives. Our goal is to provide more reliable preparation protocols and strategies for ICD-based cancer vaccines, thereby promoting their continued development and application. A crucial area of investigation for these vaccines, compared to other immunotherapies, lies in their potential to address tumor recurrence in long-term survivors of metastatic and invasive cancers To achieve curative potential, we advocate for the synergistic combination of immune-stimulating tools with ICD-based cancer vaccine therapy.

Well-documented by numerous studies, immunogenic cell death plays a critical role in generating an immunogenic tumor phenotype, effectively overcoming immunosuppressive effects of a non-immunoreactive tumor microenvironment (TME).ICD is characterized by CRT exposure, ATP release, and leakage of HMGB1 and HSP (13). These processes facilitate the uptake of TAAs by adaptive immune cells, triggering a broad-spectrum antigen-specific immune response, promoting DC maturation, and enhancing the search for DTCs (14). Furthermore, ICB therapy relies on the production and activation of tumor antigen-specific T cells. Consequently, the release of specific antigens from ICD tumor cells is crucial for reshaping the TME and has been validated in the combination of ICB with chemotherapy and radiotherapy. The recruitment of adaptive immune cells, neutrophils, macrophages, and NK cells all can activate innate effector mechanisms (15).

Immunogenic substances released during ICD can be classified into constitutive DAMPs (cDAMPs) and inducible DAMPs (iDAMPs). cDAMPs consist of immune-stimulating molecules such as CRT, ATP, HMGB1, and HSP, which are expressed prior to tumor cell death (16). iDAMPs are endogenous molecules produced by underlying mechanisms during tumor cell death, primarily including cytotoxic T-lymphocytes (CTLs) with CD3+, CD4+, and CD8+, releasing interferon-α (IFN-α), granzymes, lysins, and perforins (17). In this respect, CRT and HSP emit eat-me signals. CRT-CD91 and HSP90-CD91 interactions promote endocytosis signals in tumor cells, inducing antigen presentation and specific CTL responses. Additionally, the release of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) (18); ATP emit energy signals, ATP-P2RY2 binding is involved in the recruitment of monocytes or macrophages, neutrophils, and promoting DC maturation (19); HMGB1, aided by chemokines, binds to pattern recognition receptor (PRR) (P2RX7, P2RY2), CD91, CD40, and Toll-like receptor 4 (TLR4) receptors on the surface of antigen-presenting cells (APCs) (20). Upon the functional activation of APCs, those APCs exposed to TAA and TSA immunostimulants initiate cross-presentation to CD4+/CD8+ T cells, enhancing DC antigen presentation and CTLs proliferation (14). Consequently, the transition from a “cold” to a “hot” tumor immune microenvironment occurs, accompanied by changes in the secretion levels of immunostimulatory and immunosuppressive factors (up-regulation of IFN-γ, TNF-α, and IL-12; down-regulation of IL-4, IL-6, and IL-10), as well as the depletion of myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), and tumor-associated macrophages 2 (TAM2) (21). The above studies overlap in their assertion that ICD, as an in-situ vaccine, possesses potential immunomodulatory abilities and holds great value in reversing the TME and improving the efficacy of tumor immunotherapy.

Over the years, a multitude of ICD inducers have been developed, especially when integrated with nanotechnology, to boost the effectiveness of ICDs. Administering ICD nano-inducers to the tumor site not only averts degradation and premature active ingredient release but also enhances their penetration and retention capabilities (EPR) (22). Presently, the primary driving methods of ICDs encompass chemotherapy, photodynamic, photothermal, radiotherapy, and sonodynamic therapies Table 1 . Thus, a comprehensive investigation of ICD induction mechanisms and inducers holds substantial importance in advancing the development of “in situ ICD-based cancer vaccines”. The release of cancer cell immunogenic antigens induced by ICD and the presentation of these antigens by APCs constitute the fundamental stages of the “cancer vaccine-like function” observed in vivo ( Figure 2 ). We introduce the ICD induction methods with some latest research to provide more evidence in the field of ICD-vaccine.

“ICD-based cancer vaccines” involve DTCs for re-infusion vaccination in vivo, ultimately leading to tumor therapy. DTCs, produced after treatment with ICD inducers, exhibit excellent immunogenicity ( Figure 3 ). In this respect, studies have reported that ICD-based cancer vaccines can induce robust immune activation in mouse models during prophylactic vaccination trials in vivo (75). ICD-based cancer vaccines offer a distinct advantage by inducing a comprehensive tumor cell antigen expression profile. This eliminates the dependence on a single antibody for recognition, a major hurdle in conventional immunotherapy. By promoting the expression of diverse tumor antigens, ICD vaccines significantly reduce the risk of tumor cells evading immune attack during treatment. The rationale behind this approach lies in the ability of ICD inducers to stimulate the spontaneous production of relevant antigens, DAMPs, and immune activation molecules within tumor cells. This comprehensive immune response translates to potent antitumor effects, establishment of long-term immune memory against the tumor, and aligns perfectly with the evolving paradigm of immunotherapy, which seeks to integrate preventive and therapeutic strategies.

Studies have explored various methods for the preparation of ICD-based cancer vaccines include: One approach utilizes chemotherapy. Qing et al. demonstrated that DOX can induce tumor cells to become dendritic cell activators. They employed liquid nitrogen cryogenics to generate frozen dying tumor cells (FDTs), which achieved a 38% tumor elimination rate in the MC100 peritoneal carcinoma mouse model. Furthermore, in combination with cytokines IL-12 and aPD-L1, they achieved 100% eradication in the peritoneal metastasis model of colorectal carcinoma (76). Li et al. showed that tumor antigens CIAs induced by chemotherapeutic agents in vitro, triggering an immune response and demonstrating synergistic effects with anti-PD-1 therapy (77). Another approach involves using radiotherapy. Researchers have successfully prepared nano-vaccines in vitro using RT-induced tumor cells. These vaccines demonstrated efficacy in treating metastatic tumors and enhanced immunotherapeutic effects when combined with anti-PD-1 treatment (78).Although research on ICD inducers and strategies is more advanced, the development of ICD-based cancer vaccines in vitro is still in the preliminary stage. However, achieving high efficiency and low cost remains crucial research criteria for ICD-based cancer vaccines. Therefore, investigating whether photodynamic and sonodynamic therapy can be an ideal induction for ICD-based cancer vaccines is expected to be a worthy direction for more researchers to explore. Given the promising results of ICD induction using chemotherapy and radiotherapy, investigating the potential of PDT and SDT as triggers for ICD-based cancer vaccines warrants further exploration. we posit that the personalized design of these ICD-based cancer vaccines holds immense potential for advancing clinical translation in antitumor immunotherapy translation. As an example, previously mentioned strategies like encapsulating patient-specific nanoparticles and obtaining DC activators from tumors offer valuable avenues for personalization. While current personalized cancer vaccine development primarily focus on immune cells loaded with immune-stimulating agents, future breakthroughs lie in utilizing specific immune elements to create novel and highly effective therapeutic strategies.

In clinical immunotherapy studies involving non-small cell lung cancer, hepatocellular carcinoma, breast cancer, bladder cancer, melanoma, squamous carcinoma, and other solid tumors, the induction of ICD has demonstrated the ability to enhance the presentation function of APCs such as DCs, deplete Treg cells, and activate the vitality of immune cytotoxic effector cells. Thess combined effects ultimately lead to improved efficacy in tumor therapy.

As summarized in ( Table 2 ), clinical trials have primarily focused on chemotherapy and radiotherapy for inducing ICD, demonstrating its clinical applicability. Researchers have further shown that physical treatments, like cryoablation, can also trigger ICD, potentially improving cost-effectiveness and clinical translation efficiency. However, significant progress is needed to develop and translate ICD-based cancer vaccines for clinical use. Therefore, exploring novel therapeutic approaches based on ICD-based cancer vaccines research and establishing a system to comprehensively evaluate the types and levels of immunogenic substance generated by ICD are crucial next steps.

The immunological adjuvant effect of ICD is now understood to be intricately linked to the exposure and release of cellular DAMPs. These DAMPs include exposed CRT, secreted ATP, ANXA1, TNF-α, and HMGB1, as well as phosphorylated eIF2α. However, additional valuable markers likely remain undiscovered. For example, low levels of autophagy can both protect cells and limit the release of immunogenic substances, while potentially increasing the risk of oncogenicity during treatment. Mounting evidence suggests that tumor autophagy, once thought to be similar to apoptosis, can also impact the effectiveness of antitumor immunotherapy. As expected, the autophagy inducer called STF-62247 (STF) can effectively convert protective autophagy into ICD, thereby enhancing antitumor immune activation. Furthermore, the uncertainty surrounding conventional methods of inducing ICD and determining the optimal dosage of ICD inducers makes it challenging to accurately quantify the release of associated immunogenic DAMPs. As ICD-based cancer therapy gains wider acceptance in clinical settings, it becomes increasingly important to select closely correlated assay secretions for screening ICD inducers that possess efficient induction capabilities for future development of ICD-based cancer vaccines.

Meanwhile, the development of safer and more reliable in vitro systems for ICD-based cancer vaccines, as well as the elimination of unfavorable factors in vivo, are areas that warrant attention and in-depth exploration. While some personalized ICD-based cancer vaccine research has been discussed above, providing potential mechanisms for their effectiveness, the activation of immunity by cancer vaccines is a complex process. For instance, studies have demonstrated that targeting the STING pathway can activate innate immune signaling in immune-infiltrating cells and within tumor cells, ultimately inducing ICD. However, the effectiveness of STING pathway activation within tumor cells may vary depending on the tumor type., Nanotechnology offers a potential solution by enhancing the delivery of STING activators to cells, thereby improving their efficacy (79). The involvement of the CXCL12/CXCR4 signaling pathway also plays a role in various physiological processes, such as tumor survival, invasion, metastasis, angiogenesis, and the creation of hypoxic environments (80). Additionally, CXCR4 expression can facilitate the transportation of MDSCs in different tumors, leading to the creation of an immunosuppressive TME and immune resistance (81). In gliomas, blocking CXCR4 signaling using nanoparticles loaded with CXCR4 inhibitors can reduce the infiltration of immunosuppressive MDSC and trigger an adaptive immune response (82).

In recent years, immunotherapy has made remarkable strides in the treatment of cancer, particularly with the emergence of cancer vaccines based on immune cell death. These vaccines hold great promise for expanding and enhancing tumor immunotherapy. In this article, we expounded on the mechanisms of ICD as a potent tool for regulating TME and explored the vast potential of ICD-based cancer vaccines. The successful clinical application of ICD-based cancer vaccines necessitates a rigorous evaluation of their therapeutic value. Therefore, we advocate for the identification of more robust clinical evaluation indicators, particularly those that assess the efficacy of ICD induction by these vaccines. A comprehensive assessment of both safety and efficacy is paramount in determining the transformative potential of this approach in cancer treatment. Further exploration of the intricate mechanisms underlying ICD and its role in tumor immunotherapy is crucial to unlocking the full potential of this innovative strategy. Our ongoing research endeavors to contribute to the expanding body of knowledge surrounding ICD-based cancer vaccines and ultimately pave the way for their successful translation into clinical practice through meticulous evaluation and analysis. In conclusion, the utilization of immunogenic patterns generated by ICD in tumor cells represents a paradigm shift in the field of tumor immunotherapy. By advancing the development of disease-specific cancer vaccines, we can harness the full potential of this approach to significantly improve treatment outcomes for cancer patients. Rigorous evaluation and analysis are essential to ensure the clinical relevance and applicability of these vaccines, ultimately leading to improved patient outcomes on a global scale.

JW: Software, Visualization, Writing – original draft, Writing – review & editing. JM: Investigation, Supervision, Writing – review & editing. FX: Supervision, Writing – review & editing. FM: Supervision, Writing – review & editing. LL: Supervision, Writing – review & editing. YH: Investigation, Writing – review & editing. XZ: Supervision, Writing – review & editing. JY: Supervision, Writing – review & editing. ZT: Supervision, Writing – review & editing. QZ: Funding acquisition, Writing – review & editing. LB: Funding acquisition, Supervision, Writing – review & editing.