Biomarkers of Radiotherapy-Induced Immunogenic Cell Death

Clinical application of immunogenic cell death inducers in cancer immunotherapy: turning cold tumors hot

Immunotherapy has emerged as a promising cancer treatment option in recent years. In immune "hot" tumors, characterized by abundant immune cell infiltration, immunotherapy can improve patients' prognosis by activating the function of immune cells. By contrast, immune "cold" tumors are often less sensitive to immunotherapy owing to low immunogenicity of tumor cells, an immune inhibitory tumor microenvironment, and a series of immune-escape mechanisms. Immunogenic cell death (ICD) is a promising cellular process to facilitate the transformation of immune "cold" tumors to immune "hot" tumors by eliciting innate and adaptive immune responses through the release of (or exposure to) damage-related molecular patterns. Accumulating evidence suggests that various traditional therapies can induce ICD, including chemotherapy, targeted therapy, radiotherapy, and photodynamic therapy. In this review, we summarize the biological mechanisms and hallmarks of ICD and introduce some newly discovered and technologically innovative inducers that activate the immune system at the molecular level. Furthermore, we also discuss the clinical applications of combing ICD inducers with cancer immunotherapy. This review will provide valuable insights into the future development of ICD-related combination therapeutics and potential management for "cold" tumors.

Bimetallic nanoparticles as cascade sensitizing amplifiers for low-dose and robust cancer radio-immunotherapy

Radiotherapy (RT) is one of the most feasible and routinely used therapeutic modalities for treating malignant tumors. In particular, immune responses triggered by RT, known as radio-immunotherapy, can partially inhibit the growth of distantly spreading tumors and recurrent tumors. However, the safety and efficacy of radio-immunotherapy is impeded by the radio-resistance and poor immunogenicity of tumor. Herein, we report oxaliplatin (IV)-iron bimetallic nanoparticles (OXA/Fe NPs) as cascade sensitizing amplifiers for low-dose and robust radio-immunotherapy. The OXA/Fe NPs exhibit tumor-specific accumulation and activation of OXA (II) and Fe2+ in response to the reductive and acidic microenvironment within tumor cells. The cascade reactions of the released metallic drugs can sensitize RT by inducing DNA damage, increasing ROS and O2 levels, and amplifying the immunogenic cell death (ICD) effect after RT to facilitate potent immune activation. As a result, OXA/Fe NPs-based low-dose RT triggered a robust immune response and inhibited the distant and metastatic tumors effectively by a strong abscopal effect. Moreover, a long-term immunological memory effect to protect mice from tumor rechallenging is observed. Overall, the bimetallic NPs-based cascade sensitizing amplifier system offers an efficient radio-immunotherapy regimen that addresses the key challenges.

Nanoparticles integrated with mild photothermal therapy and oxaliplatin for tumor chemotherapy and immunotherapy

Aims: Preparation and evaluation of nanoparticles for tumor chemotherapy and immunotherapy mild photothermal therapy and oxaliplatin. Methods: The double emulsion method was used for nanoparticle preparations. Polydopamine was deposited on the surface, which was further modified with folic acid. Cytotoxicity assays were carried out by cell counting kit-8. In vivo antitumor assays were carried out on 4T1 tumor-bearing mice. Results: The nanoparticles exhibited a 190 nm-diameter pomegranate-like sphere, which could increase temperature to 43-46°C. In vivo distribution showed enhanced accumulation. The nanoparticles generated stronger immunogenic cell death effects. By stimulating the maturation of dendritic cells, mild photothermal therapy combined with oxaliplatin significantly increased the antitumor effect by a direct killing effect and activation of immunotherapy. Conclusion: This study provided a promising strategy of combination therapy for tumors.

Liver-directed moderately hypo-fractionated radiotherapy combined with pembrolizumab and bevacizumab for advanced hepatocellular carcinoma: a retrospective observational study of 23 cases

Background

Programmed cell death protein 1 (PD-1) or its ligand (PD-L1) monoclonal antibody combined with bevacizumab (a monoclonal antibody targeting vascular endothelial growth factor) has been established as first-line systemic treatment for advanced hepatocellular carcinoma (HCC). Radiotherapy is a crucial local treatment for HCC. Mutual efficacy enhancement has been reported between radiotherapy, anti-angiogenesis therapy and immunotherapy in preclinical researches, but not been validated in clinical practice. Whether radiotherapy can enhance efficacy of anti-PD-1 immunotherapy plus bevacizumab for HCC remains unclear. This retrospective observational study aimed to appraise efficacy and safety of the combination of radiotherapy with pembrolizumab (a PD-1 monoclonal antibody) and bevacizumab for advanced HCC for the first time.

Methods

Patients with advanced HCC treated by intrahepatic tumor-directed moderately hypo-fractionated radiotherapy combined with pembrolizumab and bevacizumab were consecutively included. Clinicopathological characteristics, therapeutic outcomes and treatment-related adverse events (TRAEs) were recorded and evaluated.

Results

A total of 23 patients were eventually enrolled. Median cycles of pembrolizumab and bevacizumab were 4 (median, 1-8) and 4 (median, 1-9) cycles. The objective response rates and disease control rates of irradiated intrahepatic HCC and non-irradiated extrahepatic HCC were 34.8% [95% confidence interval (CI), 16.4-57.3%] vs. 10.0% (95% CI, 1.2-31.7%), and 91.3% (95% CI, 72.0-98.9%) vs. 70.0% (95% CI, 45.7-88.1%), respectively. The median progression-free survival (PFS) and overall survival (OS) were 6.6 (95% CI, 4.7-8.5) and 18.3 (95% CI, 8.2-33.6) months, and 12-month PFS and OS rates were 17.5% (95% CI, 7.0-28.0%) and 60.9% (95% CI, 50.7-71.1%). Two patients (8.7%) with locally advanced, unresectable HCC eventually underwent curative resection of tumors after this trimodal treatment. Eighteen patients (78.3%) had ≥ grade 3 TRAEs, with myelosuppression and transaminase increase as the most common.

Conclusions

This study firstly reported that combining radiotherapy with pembrolizumab and bevacizumab was preliminarily a feasible and effective therapeutic choice for advanced HCC in despite of more TRAEs. This tri-modal regimen may be a potential conversion therapy for unresectable, locally advanced HCC. The limitations of this study are its retrospective nature and small sample size; therefore, big-sample prospective studies are warranted to further investigate this tri-modal regimen.

Endoplasmic Reticulum-Targeting AIE Photosensitizers to Boost Immunogenic Cell Death for Immunotherapy of Bladder Carcinoma

Bladder cancer is characterized by high rates of recurrence and multifocality. Immunogenic cell death (ICD) of cancer cells has emerged as a promising strategy to improve the immunogenicity of tumor cells for enhanced cancer immunotherapy. Although photosensitizer-based photodynamic therapy (PDT) has been validated as capable of inducing ICD in cancer cells, the photosensitizers with a sufficient ICD induction ability are still rare, and there have been few reports on the development of advanced photosensitizers to strongly evoke the ICD of bladder cancer cells for eliciting potent antitumor immune responses and eradicating bladder carcinoma in situ. In this work, we have synthesized a new kind of endoplasmic reticulum (ER)-targeting aggregation-induced emission (AIE) photosensitizer (named DPASCP-Tos), which could effectively anchor to the cellular ER and trigger focused reactive oxygen species (ROS) production within the ER, thereby boosting ICD in bladder cancer cells. Furthermore, we have demonstrated that bladder cancer cells killed by ER-targeted PDT could serve as a therapeutic cancer vaccine to elicit a strong antitumor immunity. Prophylactic vaccination of the bladder cancer cells killed by DPASCP-Tos under light irradiation promoted the maturation of dendritic cells (DCs) and the expansion of tumor antigen-specific CD8+ T cells in vivo and protected mice from subsequent in situ bladder tumor rechallenge and extended animal survival. In summary, the ER-targeted AIEgens developed here significantly amplified the ICD of bladder cells through focused ROS-based ER oxidative stress and transformed bladder cancer cells into the therapeutic vaccine to enhance immunogenicity against orthotopic bladder cancer, providing valuable insights for bladder carcinoma treatment.

Combining spatially fractionated radiation therapy (SFRT) and immunotherapy opens new rays of hope for enhancing therapeutic ratio

Spatially Fractionated Radiation Therapy (SFRT) is a form of radiotherapy that delivers a single large dose of radiation within the target volume in a heterogeneous pattern with regions of peak dosage and regions of under dosage. SFRT types can be defined by how the heterogeneous pattern of radiation is obtained. Immune checkpoint inhibitors (ICIs) have been approved for various malignant tumors and are widely used to treat patients with metastatic cancer. The efficacy of ICI monotherapy is limited due to the "cold" tumor microenvironment. Fractionated radiotherapy can achieve higher doses per fraction to the target tumor, and induce immune activation (immodulate tumor immunogenicity and microenvironment). Therefore, coupling ICI therapy and fractionated radiation therapy could significantly improve the outcome of metastatic cancer. This review focuses on both preclinical and clinical studies that use a combination of radiotherapy and ICI therapy in cancer.

A novel immunogenic cell death-related genes signature for predicting prognosis, immune landscape and immunotherapy effect in hepatocellular carcinoma

OBJECTIVE

Immunogenic cell death (ICD) has emerged as a promising strategy to activate the adaptive immune response, modulate the tumor microenvironment (TME) and enhance the efficacy of immune therapy. However, the relationship between ICD and TME reprogramming in hepatocellular carcinoma (HCC) remains poorly understood.

METHODS

Transcriptional profiles and clinical spectrum of 486 HCC patients were obtained from TCGA and GEO databases. We utilized consensus clustering analysis to construct two distinct molecular subtypes and established an ICD-based scoring system (named ICD score) via WGCNA and LASSO Cox regression to predict the prognosis of the HCC cohort. Then we employed CIBERSORT and ESTIMATE methods to analyze the immune landscape of ICD score in HCC. Subsequently, the immunophenoscore (IPS) and tumor immune dysfunction and rejection (TIDE) analyses were performed to determine whether the ICD score could influence the immune therapeutic effect. Based on the ICD scoring system, a novel nomogram was generated to provide a numerical probability of HCC patients' overall survival (OS).

RESULTS

We identified two independent ICD clusters (cluster A/B), and cluster B possessed a worse prognosis and higher immune cell infiltration. Using ICD scoring system, the HCC patients were divided into high- and low-ICD-score groups. Through integrative analyses, the high-ICD cohort owned advanced TNM stage, high pathologic grade and increased suppressive immune cell enrichment. We developed a nomogram containing the ICD score, demonstrating a high predictive accuracy with a C-index of 0.703. We further discovered that PSMD2 and PSMD14 could serve as ICD-associated prognostic biomarkers and therapeutic targets in HCC.

CONCLUSION

The ICD score exhibits a high degree of reliability for predicting prognosis and may provide valuable guidance for the selection of immunotherapy for HCC patients. This novel scoring system enables the estimation of clinical immunotherapy response for HCC patients, offering new opportunities for personalized immunotherapy.

Radiation-sensitive genetic prognostic model identifies individuals at risk for radiation resistance in head and neck squamous cell carcinoma

BACKGROUND

The advantages of radiotherapy for head and neck squamous cell carcinoma (HNSCC) depend on the radiation sensitivity of the patient. Here, we established and verified radiological factor-related gene signature and built a prognostic risk model to predict whether radiotherapy would be beneficial.

METHODS

Data from The Cancer Genome Atlas, Gene Expression Omnibus, and RadAtlas databases were subjected to LASSO regression, univariate COX regression, and multivariate COX regression analyses to integrate genomic and clinical information from patients with HNSCC. HNSCC radiation-related prognostic genes were identified, and patients classified into high- and low-risk groups, based on risk scores. Variations in radiation sensitivity according to immunological microenvironment, functional pathways, and immunotherapy response were investigated. Finally, the expression of HNSCC radiation-related genes was verified by qRT-PCR.

RESULTS

We built a clinical risk prediction model comprising a 15-gene signature and used it to divide patients into two groups based on their susceptibility to radiation: radiation-sensitive and radiation-resistant. Overall survival was significantly greater in the radiation-sensitive than the radiation-resistant group. Further, our model was an independent predictor of radiotherapy response, outperforming other clinical parameters, and could be combined with tumor mutational burden, to identify the target population with good predictive value for prognosis at 1, 2, and 3 years. Additionally, the radiation-resistant group was more vulnerable to low levels of immune infiltration, which are significantly associated with DNA damage repair, hypoxia, and cell cycle regulation. Tumor Immune Dysfunction and Exclusion scores also suggested that the resistant group would respond less favorably to immunotherapy.

CONCLUSIONS

Our prognostic model based on a radiation-related gene signature has potential for application as a tool for risk stratification of radiation therapy for patients with HNSCC, helping to identify candidates for radiation therapy and overcome radiation resistance.

Cyclometalated iridium(III) complexes induce immunogenic cell death in HepG2 cells via paraptosis

Immunotherapy has been shown to provide superior antitumor efficacy by activating the innate immune system to recognize, attack and eliminate tumor cells without seriously harming normal cells. Herein, we designed and synthesized three new cyclometalated iridium(III) complexes (Ir1, Ir2, Ir3) then evaluated their antitumor activity. When co-incubated with HepG2 cells, the complex Ir1 localized in the lysosome, where it induced paraptosis and endoplasmic reticulum stress (ER stress). Notably, Ir1 also induced immunogenic cell death (ICD), promoted dendritic cell maturation that enhanced effector T cell chemotaxis to tumor tissues, down-regulated proportions of immunosuppressive regulatory T cells within tumor tissues and triggered activation of antitumor immunity throughout the body. To date, Ir1 is the first reported iridium(III) complex-based paraptosis inducer to successfully induce tumor cell ICD. Furthermore, Ir1 induced ICD of HepG2 cells without affecting cell cycle or reactive oxygen species levels.

Analysis of damage-associated molecular patterns in amyotrophic lateral sclerosis based on ScRNA-seq and bulk RNA-seq data

Background

Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disorder characterized by the progressive loss of motor neurons. Despite extensive research, the exact etiology of ALS remains elusive. Emerging evidence highlights the critical role of the immune system in ALS pathogenesis and progression. Damage-Associated Molecular Patterns (DAMPs) are endogenous molecules released by stressed or damaged cells, acting as danger signals and activating immune responses. However, their specific involvement in ALS remains unclear.

Methods

We obtained single-cell RNA sequencing (scRNA-seq) data of ALS from the primary motor cortex in the Gene Expression Omnibus (GEO) database. To better understand genes associated with DAMPs, we performed analyses on cell-cell communication and trajectory. The abundance of immune-infiltrating cells was assessed using the single-sample Gene Set Enrichment Analysis (ssGSEA) method. We performed univariate Cox analysis to construct the risk model and utilized the least absolute shrinkage and selection operator (LASSO) analysis. Finally, we identified potential small molecule drugs targeting ALS by screening the Connectivity Map database (CMap) and confirmed their potential through molecular docking analysis.

Results

Our study annotated 10 cell types, with the expression of genes related to DAMPs predominantly observed in microglia. Analysis of intercellular communication revealed 12 ligand-receptor pairs in the pathways associated with DAMPs, where microglial cells acted as ligands. Among these pairs, the SPP1-CD44 pair demonstrated the greatest contribution. Furthermore, trajectory analysis demonstrated distinct differentiation fates of different microglial states. Additionally, we constructed a risk model incorporating four genes (TRPM2, ROCK1, HSP90AA1, and HSPA4). The validity of the risk model was supported by multivariate analysis. Moreover, external validation from dataset GSE112681 confirmed the predictive power of the model, which yielded consistent results with datasets GSE112676 and GSE112680. Lastly, the molecular docking analysis suggested that five compounds, namely mead-acid, nifedipine, nifekalant, androstenol, and hydrastine, hold promise as potential candidates for the treatment of ALS.

Conclusion

Taken together, our study demonstrated that DAMP entities were predominantly observed in microglial cells within the context of ALS. The utilization of a prognostic risk model can accurately predict ALS patient survival. Additionally, genes related to DAMPs may present viable drug targets for ALS therapy.

Non-cellular immunotherapies in pediatric central nervous system tumors

Central nervous system (CNS) tumors are the second most common type of cancer and the most common cause of cancer death in pediatric patients. New therapies are desperately needed for some of the most malignant of all cancers. Immunotherapy has emerged in the past two decades as an additional avenue to augment/replace traditional therapies (such as chemotherapy, surgery, and radiation therapy). This article first discusses the unique nature of the pediatric CNS immune system and how it interacts with the systemic immune system. It then goes on to review three important and widely studied types of immune therapies: checkpoint inhibitors, vaccines, and radiation therapy, and touches on early studies of antibody-mediated immunogenic therapies, Finally, the article discusses the importance of combination immunotherapy for pediatric CNS tumors, and addresses the neurologic toxicities associated with immunotherapies.

The cGAS/STING/IFN-1 Response in Squamous Head and Neck Cancer Cells after Genotoxic Challenges and Abrogation of the ATR-Chk1 and Fanconi Anemia Axis

Locally advanced head and neck squamous cell carcinomas (HNSCC) are often refractory to platinum-based radiochemotherapy and new immuno-oncological strategies. To stimulate immunogenic antitumor responses in HNSCC patients, we investigated the cGAS/STING/IFN-1 signaling pathway after genotoxic treatments and concomitant abrogation of the DNA damage response (DDR). For this purpose, FaDu and UM-SCC1 cells were exposed to X-rays or cisplatin and treated with an ATR or Chk1 inhibitor, or by Fanconi anemia gene A knockout (FANCA ko). We assessed clonogenic survival, cell cycle regulation, micronuclei, free cytosolic double-stranded DNA, and the protein expression and activity of the cGAS/STING/IFN-1 pathway and related players. Cell survival, regulation of G2/M arrest, and formation of rupture-prone cGAS-positive micronuclei after genotoxic treatments were most affected by ATR inhibition and FANCA ko. In UM-SCC-1 cells only, 8 Gy X-rays promoted IFN-1 expression unaltered by abrogation of the DDR or concomitant increased TREX1 expression. At a higher dose of 20 Gy, this effect was observed only for concurrent Chk1- or ATR-inhibition. FANCA ko or cisplatin treatment was ineffective in this regard. Our observations open new perspectives for the enhancement of cGAS/STING/IFN-1-mediated antitumor immune response in HNSCC by hypofractionated or stereotactic radiotherapy concepts in multimodal settings with immuno-oncological strategies.

Calreticulin as a marker and therapeutic target for cancer

Calreticulin (CRT) is a multifunctional protein found within the endoplasmic reticulum (ER). In addition, CRT participates in the formation and development of tumors and promotes the proliferation and migration of tumor cells. When a malignant tumor occurs in the human body, cancer cells that die from immunogenic cell death (ICD) expose CRT on their surface, and CRT that is transferred to the cell surface represents an "eat me" signal, which promotes dendritic cells to phagocytose the tumor cells, thereby increasing the sensitivity of tumors to anticancer immunotherapy. Expression of CRT in tumor tissues is higher than in normal tissues and is associated with disease progression in many malignant tumors. Thus, the dysfunctional production of CRT can promote tumorigenesis because it disturbs not only the balance of healthy cells but also the body's immune surveillance. CRT may be a diagnostic marker and a therapeutic target for cancer, which is discussed extensively in this review.

Trial watch: chemotherapy-induced immunogenic cell death in oncology

Immunogenic cell death (ICD) refers to an immunologically distinct process of regulated cell death that activates, rather than suppresses, innate and adaptive immune responses. Such responses culminate into T cell-driven immunity against antigens derived from dying cancer cells. The potency of ICD is dependent on the immunogenicity of dying cells as defined by the antigenicity of these cells and their ability to expose immunostimulatory molecules like damage-associated molecular patterns (DAMPs) and cytokines like type I interferons (IFNs). Moreover, it is crucial that the host's immune system can adequately detect the antigenicity and adjuvanticity of these dying cells. Over the years, several well-known chemotherapies have been validated as potent ICD inducers, including (but not limited to) anthracyclines, paclitaxels, and oxaliplatin. Such ICD-inducing chemotherapeutic drugs can serve as important combinatorial partners for anti-cancer immunotherapies against highly immuno-resistant tumors. In this Trial Watch, we describe current trends in the preclinical and clinical integration of ICD-inducing chemotherapy in the existing immuno-oncological paradigms.

Analysis of immunogenic cell death in atherosclerosis based on scRNA-seq and bulk RNA-seq data

BACKGROUND

Regulated cell death plays a very important role in atherosclerosis (AS). Despite a large number of studies, there is a lack of literature on immunogenic cell death (ICD) in AS.

METHOD

Carotid atherosclerotic plaque single-cell RNA (scRNA) sequencing data were analyzed to define involved cells and determine their transcriptomic characteristics. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, CIBERSORT, ESTIMATE and ssGSEA (Gene Set Enrichment Analysis), consensus clustering analysis, random forest (RF), Decision Curve Analysis (DCA), and the Drug-Gene Interaction and DrugBank databases were applied for bulk sequencing data. All data were downloaded from Gene Expression Omnibus (GEO).

RESULT

mDCs and CTLs correlated obviously with AS occurrence and development (k2(mDCs) = 48.333, P < 0.001; k2(CTL) = 130.56, P < 0.001). In total, 21 differentially expressed genes were obtained for the bulk transcriptome; KEGG enrichment analysis results were similar to those for differentially expressed genes in endothelial cells. Eleven genes with a gene importance score > 1.5 were obtained in the training set and validated in the test set, resulting in 8 differentially expressed genes for ICD. A model to predict occurrence of AS and 56 drugs that may be used to treat AS were obtained with these 8 genes.

CONCLUSION

Immunogenic cell death occurs mainly in endothelial cells in AS. ICD maintains chronic inflammation in AS and plays a crucial role in its occurrence and development. ICD related genes may become drug-targeted genes for AS treatment.

Anti-4-1BB immunotherapy enhances systemic immune effects of radiotherapy to induce B and T cell-dependent anti-tumor immune activation and improve tumor control at unirradiated sites

Radiation therapy (RT) can prime and boost systemic anti-tumor effects via STING activation, resulting in enhanced tumor antigen presentation and antigen recognition by T cells. It is increasingly recognized that optimal anti-tumor immune responses benefit from coordinated cellular (T cell) and humoral (B cell) responses. However, the nature and functional relevance of the RT-induced immune response are controversial, beyond STING signaling, and agonistic interventions are lacking. Here, we show that B and CD4+ T cell accumulation at tumor beds in response to RT precedes the arrival of CD8+ T cells, and both cell types are absolutely required for abrogated tumor growth in non-irradiated tumors. Further, RT induces increased expression of 4-1BB (CD137) in both T and B cells; both in preclinical models and in a cohort of patients with small cell lung cancer treated with thoracic RT. Accordingly, the combination of RT and anti-41BB therapy leads to increased immune cell infiltration in the tumor microenvironment and significant abscopal effects. Thus, 4-1BB therapy enhances radiation-induced tumor-specific immune responses via coordinated B and T cell responses, thereby preventing malignant progression at unirradiated tumor sites. These findings provide a rationale for combining RT and 4-1bb therapy in future clinical trials.

Anti-Tumor Immunity and Preoperative Radiovaccination: Emerging New Concepts in the Treatment of Breast Cancer

Neoadjuvant chemotherapy (NACT) for certain breast cancer (BC) subtypes confers significant tumor regression rates and a survival benefit for patients with a complete pathologic response. Clinical and preclinical studies have demonstrated that immune-related factors are responsible for better treatment outcomes, and thus, neoadjuvant immunotherapy (IO) has emerged as a means to further improve patient survival rates. Innate immunological "coldness", however, of specific BC subtypes, especially of the luminal ones, due to their immunosuppressive tumor microenvironment, hinders the efficacy of immune checkpoint inhibitors. Treatment policies aiming to reverse this immunological inertia are, therefore, needed. Moreover, radiotherapy (RT) has been proven to have a significant interplay with the immune system and promote anti-tumor immunity. This "radiovaccination" effect could be exploited in the neoadjuvant setting of BC and significantly enhance the effects of the already established clinical practice. Modern stereotactic irradiation techniques directed to the primary tumor and involved lymph nodes may prove important for the RT-NACT-IO combination. In this review, we provide an overview and critically discuss the biological rationale, clinical experience, and ongoing research underlying the interplay between neoadjuvant chemotherapy, anti-tumor immune response, and the emerging role of RT as a preoperative adjunct with immunological therapeutic implications in BC.

Harnessing the Immunological Effects of Radiation to Improve Immunotherapies in Cancer

Ionizing radiation (IR) is used to treat 50% of cancers. While the cytotoxic effects related to DNA damage with IR have been known since the early 20th century, the role of the immune system in the treatment response is still yet to be fully determined. IR can induce immunogenic cell death (ICD), which activates innate and adaptive immunity against the cancer. It has also been widely reported that an intact immune system is essential to IR efficacy. However, this response is typically transient, and wound healing processes also become upregulated, dampening early immunological efforts to overcome the disease. This immune suppression involves many complex cellular and molecular mechanisms that ultimately result in the generation of radioresistance in many cases. Understanding the mechanisms behind these responses is challenging as the effects are extensive and often occur simultaneously within the tumor. Here, we describe the effects of IR on the immune landscape of tumors. ICD, along with myeloid and lymphoid responses to IR, are discussed, with the hope of shedding light on the complex immune stimulatory and immunosuppressive responses involved with this cornerstone cancer treatment. Leveraging these immunological effects can provide a platform for improving immunotherapy efficacy in the future.

Ferrostatin-1 mitigates ionizing radiation-induced intestinal injuries by inhibiting apoptosis and ferroptosis: an in vitro and in vivo study

PURPOSE

Intestinal injuries caused by ionizing radiation (IR) are a major complication of radiotherapy. Ferrostatin-1 (Fer-1) exerts antioxidant and anti-inflammatory effects. We investigated the influence of Fer-1 on IR-induced intestinal damage and explored the possible mechanisms.

MATERIALS AND METHODS

IEC-6 cells were administrated with Fer-1 for 30 min and subsequently subjected to 9.0 Gy-irradiation. Flow cytometry, qPCR, and WB were used to detect changes. For in vivo experiments, Fer-1 was given intraperitoneally to mice at 1 h before and 24 h after 9.0 Gy total body irradiation (TBI) respectively. Three days after TBI, the small intestines were isolated for analysis. The diversity and composition of the gut microbiota were analyzed by 16S rRNA gene sequencing.

RESULTS

In vitro, Fer-1 protected IEC-6 cells from IR injury by reducing the production of ROS and inhibiting both ferroptosis and apoptosis. In vivo, Fer-1 enhanced the survival rates of mice subjected to lethal doses of IR and restored intestinal structure and physiological function. Further investigation showed that Fer-1 protected IEC-6 cells and mice by inhibiting the p53-mediated apoptosis signaling pathway and restoring the gut-microbe balance.

CONCLUSION

This study confirms that Fer-1 protects intestinal injuries through suppressing apoptosis and ferroptosis.

Radiation Therapy and the Microbiome; More Than a Gut Feeling

ABSTRACT

It is increasingly recognized that heterogeneities in tumor response and severity of adverse effects in irradiated patients can be attributed to the tumor microenvironment and host-related factors. Among the latter, a growing body of literature in recent years has demonstrated the role of the patient's microbiome in modulating both tumor and normal tissue response to radiotherapy (RT). Upon contact with the environment after birth, the infant's gastrointestinal tract is rapidly colonized by microbiota, which is low in diversity and predominantly characterized by 2 dominant species, Actinobacteria and Proteobacteria. With time, intestinal microbiota diversity increases, and colonization of Firmicutes and Bacteroidetes becomes dominant. By the time a child reaches 3 years, the gut microbiota composition has been reshaped and is relatively similar to that of an adult. The microbiome colonizing the different body organs comprises various species and abundances, which may impact human health. Although the adult microbiome composition is thought to remain stable in health, microbiome diversity and composition respond to different environmental and pathological conditions, including pharmaceutical interventions and RT. Our review focuses on how the gut microbiota modulates normal tissue toxicity and tumor control. Readers who want to learn more about how RT shapes gut microbiome diversity and composition are referred to several excellent recently published reviews.

Integrated Nanorod-Mediated PD-L1 Downregulation in Combination with Oxidative-Stress Immunogene Therapy against Cancer

It is an engaging program for tumor treatment that rationalizes the specific microenvironments, activation of suppressed immune system (immune resistance/escape reversion), and synergistic target therapy. Herein, a biomimetic nanoplatform that combines oxidative stress with genetic immunotherapy to strengthen the therapeutic efficacy is developed. Ru-TePt nanorods, small interfering RNA (PD-L1 siRNA), and biomimetic cellular membrane vesicles with the targeting ability to design a multifunctional Ru-TePt@siRNA-MVs system are rationally integrated. Notably, the Fenton-like activity significantly enhances Ru-TePt nanorods sonosensitization, thus provoking stronger oxidative stress to kill cells directly. Meanwhile, immunogenic cell death is triggered to secrete numerous cytokines and activate T cells. The effective catalase characteristics of Ru-TePt enable the in situ oxygen-producing pump to improve tumor oxygen level and coordinately strengthen the therapeutic effect of SDT followed. More importantly, anti-PD-L1-siRNA mediated immune checkpoint silence of the PD-L1 gene creates an environment conducive to activating cytotoxic T lymphocytes, synergistic with boosted reactive oxygen species-triggered antitumor immune response. The experimental results in vitro and in vivo reveal that the Ru-TePt@siRNA-MVs nanosystems can effectively activate the oxidative stress-triggered immune response and inhibit PD-1/PD-L1 axis-mediated immune resistance. Consequently, this orchestrated treatment paradigm provides valuable insights for developing potential oxidative stress and genetic immunotherapy.

Basic and translational research on carbon-ion radiobiology

Carbon-ion beam irradiation (IR) has evident advantages over the conventional photon beams in treating tumors. It releases enormous amount of energy in a well-defined range with insignificant scatter in surrounding tissues based on well-localized energy deposition. Over the past 28 years, more than 14,000 patients with various types of cancer have been treated by carbon ion radiotherapy (CIRT) with promising results at QST. I have provided an overview of the basic and translational research on carbon-ion radiobiology including mechanisms underlying high linear energy transfer (LET) carbon-ion IR-induced cell death (apoptosis, autophagy, senescence, mitotic catastrophe etc.) and high radiocurability produced by carbon-ion beams in combination with DNA damaging drugs or with molecular-targeted drugs, micro-RNA therapeutics and immunotherapy. Additionally, I have focused on the application of these treatment in human cancer cells, especially cancer stem cells (CSCs). Finally, I have summarized the current studies on the application of basic carbon-ion beam IR according to the cancer types and clinical outcomes.

Chemotherapeutic and targeted drugs-induced immunogenic cell death in cancer models and antitumor therapy: An update review

As traditional strategies for cancer treatment, some chemotherapy agents, such as doxorubicin, oxaliplatin, cyclophosphamide, bortezomib, and paclitaxel exert their anti-tumor effects by inducing immunogenic cell death (ICD) of tumor cells. ICD induces anti-tumor immunity through release of, or exposure to, damage-related molecular patterns (DAMPs), including high mobility group box 1 (HMGB1), calreticulin, adenosine triphosphate, and heat shock proteins. This leads to activation of tumor-specific immune responses, which can act in combination with the direct killing functions of chemotherapy drugs on cancer cells to further improve their curative effects. In this review, we highlight the molecular mechanisms underlying ICD, including those of several chemotherapeutic drugs in inducing DAMPs exposed during ICD to activate the immune system, as well as discussing the prospects for application and potential role of ICD in cancer immunotherapy, with the aim of providing valuable inspiration for future development of chemoimmunotherapy.

Thoracic irradiation as consolidation therapy in patients with extensive-stage small cell lung cancer

PURPOSE OF REVIEW

Small cell lung cancer (SCLC) is marked by an exceptionally high proliferative rate and poor prognosis. Given its high propensity to metastasize, nearly two-thirds of SCLC patients are diagnosed with extensive-stage (ES) disease when surgery is not a treatment option anymore. Over several decades, only minimal changes have been made in the therapeutic armamentarium of ES-SCLC. Recently, however, several new therapeutic avenues were defined, thus renewing the hope for patients with this recalcitrant cancer. Here, we present an overview of the most current therapeutic advances in ES-SCLC focusing in particular on consolidative thoracic radiation therapy (cTRT) and chemo-immunotherapy.

RECENT FINDINGS

The incorporation of immunotherapy in the standard-of-care of ES-SCLC patients and the resulting outcomes are both a remarkable hallmark of progress and a disappointment. Indeed, chemo-immunotherapy with or without cTRT and prophylactic cranial irradiation contributes to longer survival outcomes with minimal toxicity rates in well selected and properly monitored patients. Nevertheless, the gain in overall survival is still modest relative to that seen in many other solid tumors.

SUMMARY

Despite the encouraging results, further clinical trials are needed to determine the efficacy and safety of these therapeutic approaches, and moreover, to identify new predictive biomarkers of response.

Schweinfurthin induces ICD without ER stress and caspase activation

Our previous study showed that one of the schweinfurthin compounds, 5’-methoxyschweinfurthin G (MeSG), not only enhances the anti-tumor effect of anti-PD1 antibody in the B16F10 murine melanoma model, but also provokes durable, protective anti-tumor immunity. Here we further investigated the mechanisms by which MeSG treatment induces immunogenic cell death (ICD). MeSG induced significant cell surface calreticulin (CRT) exposure in a time and concentration dependent manner as well as increased phagocytosis of tumor cells by dendritic cells in vitro. Interestingly, this CRT exposure differs from the canonical pathway in several aspects. MeSG does not cause ER stress and does not require PERK to induce CRT exposure. Caspase inhibitors partially rescue cells from MeSG-induced apoptosis, but fail to reduce CRT exposure. MeSG does not cause ERp57 exposure and the absence of ERp57 expression does not reduce CRT exposure. Finally, an intact ER to Golgi transport system is required for this phenomenon. These results lend support to the development of the schweinfurthin family as drugs to enhance clinical response to immunotherapy and highlight the need for additional research on the mechanisms of ICD induction.

Encouraging efficacy of a comprehensive therapy consisting of sintilimab, bevacizumab biosimilar IBI305, hypo-fractionated intensity-modulated radiotherapy, and oxaliplatin for a maxillary metastasis from hepatocellular carcinoma: A case report and literature review

Oro-maxillo-facial metastasis from hepatocellular carcinoma (HCC) is very rare, and reports on treating maxillary metastasis from HCC are unavailable. Anti-angiogenesis therapy combined with immunotherapy represented by programmed cell death 1 (PD-1) or its ligand (PD-L1) inhibitor has become the standard treatment of advanced HCC. However, integrating chemoradiotherapy into immunotherapy-bevacizumab combination therapy has not been reported. Here, we presented a Chinese woman with maxillary metastasis from HCC who achieved a nearly complete response (CR) to a quadruple treatment scheme consisting of a PD-1 monoclonal antibody (sintilimab), bevacizumab biosimilar IBI305, hypo-fractionated intensity-modulated radiotherapy (hfIMRT), and concurrent oxaliplatin. This comprehensive treatment is an innovative and effective therapy for advanced HCC.

Dynamic alterations in PD-1/PD-L1 expression level and immune cell profiles based on radiation response status in mouse tumor model

Introduction

Based on the immunologic effects of anti-cancer treatment and their therapeutic implications, we evaluated radiotherapy (RT)-induced dynamic alterations in programmed death-1 (PD-1)/PD ligand-1 (PD-L1) expression profiles.

Methods

Local RT with 2 Gy × 5 or 7.5 Gy × 1 was administered to the CT26 mouse model. Thereafter, tumors were resected and evaluated at the following predefined timepoints according to radiation response status: baseline, early (immediately after RT), middle (beginning of tumor shrinkage), late (stable status with RT effect), and progression (tumor regrowth). PD-1/PD-L1 activity and related immune cell profiles were quantitatively assessed.

Results

RT upregulated PD-L1 expression in tumor cells from the middle to late phase; however, the levels subsequently decreased to levels comparable to baseline in the progression phase. RT with 2 Gy × 5 induced a higher frequency of PD-L1+ myeloid-derived suppressor cells, with a lesser degree of tumor regression, compared to 7.5 Gy. The proportion of PD-1+ and interferon (IFN)-γ+CD8α T cells continued to increase. The frequency of splenic PD-1+CD8+ T cells was markedly elevated, and was sustained longer with 2 Gy × 5. Based on the transcriptomic data, RT stimulated the transcription of immune-related genes, leading to sequentially altered patterns.

Discussion

The dynamic alterations in PD-1/PD-L1 expression level were observed according to the time phases of tumor regression. This study suggests the influence of tumor cell killing and radiation dosing strategy on the tumor immune microenvironment.

Toward Precision Radiotherapy: A Nonlinear Optimization Framework and an Accelerated Machine Learning Algorithm for the Deconvolution of Tumor-Infiltrating Immune Cells

Tumor-infiltrating immune cells (TIICs) form a critical part of the ecosystem surrounding a cancerous tumor. Recent advances in radiobiology have shown that, in addition to damaging cancerous cells, radiotherapy drives the upregulation of immunosuppressive and immunostimulatory TIICs, which in turn impacts treatment response. Quantifying TIICs in tumor samples could form an important predictive biomarker guiding patient stratification and the design of radiotherapy regimens and combined immune-radiation treatments. As a result of several limitations associated with experimental methods for quantifying TIICs and the availability of extensive gene sequencing data, deconvolution-based computational methods have appeared as a suitable alternative for quantifying TIICs. Accordingly, we introduce and discuss a nonlinear regression approach (remarkably different from the traditional linear modeling approach of current deconvolution-based methods) and a machine learning algorithm for approximating the solution of the resulting constrained optimization problem. This way, the deconvolution problem is treated naturally, given that the gene expression levels of pure and heterogenous samples do not have a strictly linear relationship. When applied across transcriptomics datasets, our approach, which also allows the coupling of different loss functions, yields results that closely match ground-truth values from experimental methods and exhibits superior performance over popular deconvolution-based methods.

A pan-tumor-siRNA aptamer chimera to block nonsense-mediated mRNA decay inflames and suppresses tumor progression

Immune-checkpoint blockade (ICB) therapy has changed the clinical outcome of many types of aggressive tumors, but there still remain many cancer patients that do not respond to these treatments. There is an unmet need to develop a feasible clinical therapeutic platform to increase the rate of response to ICB. Here we use a previously described clinically tested aptamer (AS1411) conjugated with SMG1 RNAi (AS1411-SMG1 aptamer-linked siRNA chimeras [AsiCs]) to inhibit the nonsense-mediated RNA decay pathway inducing tumor inflammation and improving response to ICB. The aptamer AS1411 shows binding to numerous mouse and human tumor cell lines tested. AS1411 induces tumor cytotoxicity in long incubation times, which allows for the use of the aptamer as a carrier to target the RNAi inhibition to the tumor. The AS1411-SMG1 AsiCs induce a strong antitumor response in local and systemic treatment in different types of tumors. Finally, AS1411-SMG1 AsiCs are well tolerated with no detected side effects.

An Overview on Immunogenic Cell Death in Cancer Biology and Therapy

Immunogenic cell death (ICD) is a modality of regulated cell death that is sufficient to promote an adaptive immune response against antigens of the dying cell in an immunocompetent host. An important characteristic of ICD is the release and exposure of damage-associated molecular patterns, which are potent endogenous immune adjuvants. As the induction of ICD can be achieved with conventional cytotoxic agents, it represents a potential approach for the immunotherapy of cancer. Here, different aspects of ICD in cancer biology and treatment are reviewed.

A ‘Hybrid’ Radiotherapy Regimen Designed for Immunomodulation: Combining High-Dose Radiotherapy with Low-Dose Radiotherapy

Simple Summary

Radiotherapy is an important cancer treatment. Aside from its direct killing effect, it also affects anti-tumor immunity. However, radiotherapy’s immune effect is not clear; it depends on the dose and fraction, cancer type, combined immunotherapy, and many other factors. Studies have focused on the optimal radiotherapy regimen to stimulate anti-tumor immunity, but conflicts exist, especially regarding the best radiation dose and fractions. Interestingly, high-dose radiotherapy and low-dose radiotherapy have complementary effects on stimulating anti-tumor immunity. Preclinical studies supporting this finding have accumulated, but gaps between theory and clinical practice still exist. This review summarizes the evidence supporting the use of this ‘hybrid’ radiotherapy approach to effectively stimulate anti-tumor immunity, explains the immune mechanisms of this combination, raises questions that must be addressed in clinical practice, and provides ideas for designing individualized treatment to increase efficiency in stimulating anti-tumor immunity using high-dose plus low-dose radiotherapy.

Abstract

Radiotherapy (RT) affects anti-tumor immunity. However, the exact impact of RT on anti-tumor immune response differs among cancer types, RT dose and fractions, patients’ innate immunity, and many other factors. There are conflicting findings on the optimal radiation dose and fractions to stimulate effective anti-tumor immunity. High-dose radiotherapy (HDRT) acts in the same way as a double-edged sword in stimulating anti-tumor immunity, while low-dose radiotherapy (LDRT) seems to play a vital role in modulating the tumor immune microenvironment. Recent preclinical data suggest that a ‘hybrid’ radiotherapy regimen, which refers to combining HDRT with LDRT, can reap the advantages of both. Clinical data have also indicated a promising potential. However, there are still questions to be addressed in order to put this novel combination therapy into clinical practice. For example, the selection of treatment site, treatment volume, the sequencing of high-dose radiotherapy and low-dose radiotherapy, combined immunotherapy, and so on. This review summarizes the current evidence supporting the use of HDRT + LDRT, explains possible immune biology mechanisms of this ‘hybrid’ radiotherapy, raises questions to be considered when working out individualized treatment plans, and lists possible avenues to increase efficiency in stimulating anti-tumor immunity using high-dose plus low-dose radiotherapy.

Association of Cell Death Markers With Tumor Immune Cell Infiltrates After Chemo-Radiation in Cervical Cancer

Irradiation induces distinct cellular responses such as apoptosis, necroptosis, iron-dependent cell death (a feature of ferroptosis), senescence, and mitotic catastrophe. Several of these outcomes are immunostimulatory and may represent a potential for immunogenic type of cell death (ICD) induced by radiotherapy triggering abscopal effects. The purpose of this study is to determine whether intra-tumoral ICD markers can serve as biomarkers for the prediction of patient's outcomes defined as the metastasis status and survival over a 5-year period. Thirty-eight patients with locally advanced cervical cancer, treated with neoadjuvant chemoradiotherapy using cisplatin were included in this study. Pre-treatment tumor biopsy and post-treatment hysterectomy samples were stained for cell death markers and danger associated molecular patterns (DAMPs): cleaved caspase-3 (apoptosis), phosphorylated mixed lineage kinase domain like pseudokinase (pMLKL; necroptosis), glutathione peroxidase 4 (GPX4; ferroptosis) and 4-hydroxy-2-noneal (4-HNE; ferroptosis), high mobility group box 1 (HMGB1) and calreticulin. Although these markers could not predict the patient's outcome in terms of relapse or survival, many significantly correlated with immune cell infiltration. For instance, inducing ferroptosis post-treatment seems to negatively impact immune cell recruitment. Measuring ICD markers could reflect the impact of treatment on the tumor microenvironment with regard to immune cell recruitment and infiltration.

One Sentence Summary

Cell death readouts during neoadjuvant chemoradiation in cervical cancer.

Clinical Significance of Preoperative Hematological Parameters in Patients with D2-Resected, Node-Positive Stomach Cancer

The purpose of the present study was to investigate the clinical significance of preoperative hematological parameters in patients with advanced stomach cancer, and to explore who might benefit from adjuvant concurrent chemoradiotherapy (CCRT) compared to chemotherapy alone. Among 1032 patients with node-positive stomach cancer who had a confirmed diagnosis after complete D2 resection, and who received adjuvant chemotherapy alone or CCRT, a total of 692 patients was selected using propensity score matching. Among absolute neutrophil count, absolute lymphocyte count (ALC), absolute monocyte count (AMC), platelet count, neutrophil-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, and platelet-to-lymphocyte ratio, AMC was the most relevant prognostic factor for overall survival and recurrence-free survival (hazard ratio (HR) 1.674, 95% confidence interval (CI) 1.180–2.376; HR 1.908, 95% CI 1.650–2.695, respectively). In a subgroup with a high ALC, patients treated with adjuvant CCRT had a favorable recurrence-free survival (HR 0.620, 95% CI 0.393–0.980) compared to those treated with chemotherapy alone. Further study is needed to confirm our findings and to develop tailored adjuvant treatment.

DNA-Based MXFs to Enhance Radiotherapy and Stimulate Robust Antitumor Immune Responses

Metal "X" Frameworks (MXFs) constructed from metal ions and biomacromolecules ("X components") via coordination interactions show crystalline structures and diverse functionalities. Here, a series of MXFs composed of various metal ions (e.g., Zn²⁺, Hf⁴⁺, Ca²⁺) and DNA oligodeoxynucleotides were reported. With MXF consisting of Hf⁴⁺ and CpG oligodeoxynucleotides as the example, we show that such Hf-CpG MXF can achieve high-Z elements-enhanced photon radiotherapy and further trigger robust tumor-specific immune responses, thus showing efficient tumor suppression ability. In vivo experiments showed that external beam radiotherapy applied on tumors locally injected with Hf-CpG MXF result in the thorough elimination of primary tumors, complete inhibition of tumor metastasis, and protection against tumor rechallenge by triggering robust antitumor immune responses. Our findings provide a blueprint for fabricating a variety of rationally designed MXFs with desired functions and present the strategy of stimulating whole-body systemic immune responses by only local treatment of radiotherapy.

Immunogenic cell death and its therapeutic or prognostic potential in high-grade glioma

Immunogenic cell death (ICD) has emerged as a key component of therapy-induced anti-tumor immunity. Over the past few years, ICD was found to play a pivotal role in a wide variety of novel and existing treatment modalities. The clinical application of these techniques in cancer treatment is still in its infancy. Glioblastoma (GBM) is the most lethal primary brain tumor with a dismal prognosis despite maximal therapy. The development of new therapies in this aggressive type of tumors remains highly challenging partially due to the cold tumor immune environment. GBM could therefore benefit from ICD-based therapies stimulating the anti-tumor immune response. In what follows, we will describe the mechanisms behind ICD and the ICD-based (pre)clinical advances in anticancer therapies focusing on GBM.

The importance of hypoxia in radiotherapy for the immune response, metastatic potential and FLASH-RT

PURPOSE

Hypoxia (low oxygen) is a common feature of solid tumors that has been intensely studied for more than six decades. Here we review the importance of hypoxia to radiotherapy with a particular focus on the contribution of hypoxia to immune responses, metastatic potential and FLASH radiotherapy, active areas of research by leading women in the field.

CONCLUSION

Although hypoxia-driven metastasis and immunosuppression can negatively impact clinical outcome, understanding these processes can also provide tumor-specific vulnerabilities that may be therapeutically exploited. The different oxygen tensions present in tumors and normal tissues may underpin the beneficial FLASH sparing effect seen in normal tissue and represents a perfect example of advances in the field that can leverage tumor hypoxia to improve future radiotherapy treatments.

Identification of Potential Prognostic and Predictive Immunological Biomarkers in Patients with Stage I and Stage III Non-Small Cell Lung Cancer (NSCLC): A Prospective Exploratory Study

Radiotherapy (RT) and chemotherapy can induce immune responses, but not much is known regarding treatment-induced immune changes in patients. This exploratory study aimed to identify potential prognostic and predictive immune-related proteins associated with progression-free survival (PFS) in patients with non-small cell lung cancer (NSCLC). In this prospective study, patients with stage I NSCLC treated with stereotactic body radiation therapy (n = 26) and patients with stage III NSCLC treated with concurrent chemoradiotherapy (n = 18) were included. Blood samples were collected before (v1), during (v2), and after RT (v3). In patients with stage I NSCLC, CD244 (HR: 10.2, 95% CI: 1.8-57.4) was identified as a negative prognostic biomarker. In patients with stage III NSCLC, CR2 and IFNGR2 were identified as positive prognostic biomarkers (CR2, HR: 0.00, 95% CI: 0.00-0.12; IFNGR2, HR: 0.04, 95% CI: 0.00-0.46). In addition, analysis of the treatment-induced changes of circulating protein levels over time (Δv2/v3-v1) also identified CXCL10 and IL-10 as negative predictive biomarkers (CXCL10, HR: 3.86, 95% CI: 1.0-14.7; IL-10, HR: 16.92 (2.74-104.36)), although serum-induced interferon (IFN) response was a positive prognostic. In conclusion, we identified several circulating immunogenic proteins that are correlated with PFS in patients with stage I and stage III NSCLC before and during treatment.

Dynamics of HMBG1 (High Mobility Group Box 1) during radiochemotherapy correlate with outcome of HNSCC patients

Purpose

High Mobility Group Box 1 (HMGB1) protein has been described as a consensus marker for immunogenic cell death (ICD) in cancer. To personalize treatments, there is a need for biomarkers to adapt dose prescription, concomitant chemotherapy, and follow-up in radiation oncology. Thus, we investigated the levels of HMGB1 in plasma of patients with head and neck squamous cell carcinoma (HNSCC) during the course of radiochemotherapy and follow-up in correlation with oncologic outcome and clinical confounders.

Methods

In our pilot study, 11 patients with advanced HNSCC were treated with definitive radiochemotherapy. Blood samples were taken weekly during treatment and frequently at follow-up visits. HMGB1 levels as well as routine laboratory values were measured and clinical information was collected including tumor volume, infections, toxicity, and follow-up data.

Results

In total, 85 samples were analyzed. In eight patients, HMGB1 levels (baseline vs. last available sample during treatment) were increasing and in three patients HMGB1 values were decreasing toward the end of treatment. All three patients with decreasing values developed tumor recurrence. By contrast, no relapse occurred in patients that showed increasing HMGB1 levels during therapy. Moreover, a positive correlation of HMGB1 levels with tumor volumes, C‑reactive protein (CRP) levels, infections, and grade three toxicity (RTOG) was observed.

Conclusion

HMGB1 might be a promising marker to monitor ICD in HNSCC during the course of radiochemotherapy. However, HMGB1 seems to reflect complex and diverse immunogenic responses and potential confounders. Infections and treatment-associated toxicity should be considered when interpreting the dynamics of HMGB1.

Immunogenic Cell Death Induction by Ionizing Radiation

Immunogenic cell death (ICD) is a form of regulated cell death (RCD) induced by various stresses and produces antitumor immunity via damage-associated molecular patterns (DAMPs) release or exposure, mainly including high mobility group box 1 (HMGB1), calreticulin (CRT), adenosine triphosphate (ATP), and heat shock proteins (HSPs). Emerging evidence has suggested that ionizing radiation (IR) can induce ICD, and the dose, type, and fractionation of irradiation influence the induction of ICD. At present, IR-induced ICD is mainly verified in vitro in mice and there is few clinical evidence about it. To boost the induction of ICD by IR, some strategies have shown synergy with IR to enhance antitumor immune response, such as hyperthermia, nanoparticles, and chemotherapy. In this review, we focus on the molecular mechanisms of ICD, ICD-promoting factors associated with irradiation, the clinical evidence of ICD, and immunogenic forms of cell death. Finally, we summarize various methods of improving ICD induced by IR.

[Precision medicine and immuno-radiotherapy]

Numerous clinical studies aim to integrate immunotherapy in radiotherapy oncology, either for generating abscopal responses in metastatic patients in combination with radiotherapy, or in the treatment of a locally advanced tumor. The search for biomarkers of response to treatment is a major axis in the development of these therapeutic combinations, to allow the early identification of patients who will benefit from the treatment, in the context of an increasingly personalized approach. We review some of the strategies that can be applied for personalization to combined radiotherapy and immunotherapy treatments.

Exploring the optimal dose of low ionizing radiation to enhance immune function: a rabbit model

Primary liver cancer is one of the most common malignant tumors in China. Currently, immunotherapy for liver cancer is a research hotspot. Experimental studies and epidemiological investigations have confirmed the antineoplastic activity of low ionizing radiation. The aim of this study was to explore the optimal dose of low ionizing radiation to enhance immune function. Twenty-five New Zealand rabbits were randomly divided into five groups (n = 5 each): experimental group 1 (25 mGy), experimental group 2 (50 mGy), experimental group 3 (75 mGy), experimental group 4 (100 mGy), and the control group (0 mGy). VX-2 tumor tissue was injected into rabbits using a high-frequency B-ultrasound probe (3.5 MHz). Rabbits were irradiated, and on day 4 after irradiation, blood was collected from each rabbit. Blood chemistry, interleukin (IL)-4, interferon (IFN)-γ, immunoglobulin (Ig)G, and IgM levels were assessed. On day 15 after irradiation, macrophage phagocytic function was assessed. The rabbits were sacrificed, and the spleen was removed and weighed to calculate its spleen index. Each parameter was highest in the experimental group 3 (75 mGy). Thus, we suspect the optimal low ionizing radiation dose to improve immune function may be 75 mGy.