Irradiation of tumor cells up-regulates Fas and enhances CTL lytic activity and CTL adoptive immunotherapy

Immune effects of α and β radionuclides in metastatic prostate cancer

External beam radiotherapy is used for radical treatment of organ-confined prostate cancer and to treat lesions in metastatic disease whereas molecular radiotherapy with labelled prostate-specific membrane antigen ligands and radium-223 (223Ra) is indicated for metastatic prostate cancer and has demonstrated substantial improvements in symptom control and overall survival compared with standard-of-care treatment. Prostate cancer is considered an immunologically cold tumour, so limited studies investigating the treatment-induced effects on the immune response have been completed. However, emerging data support the idea that radiotherapy induces an immune response in prostate cancer, but whether the response is an antitumour or pro-tumour response is dependent on the radiotherapy regime and is also cell-line dependent. In vitro data demonstrate that single-dose radiotherapy regimes induce a greater immune-suppressive profile than fractionated regimes; less is known about the immune response induced by molecular radiotherapy agents, but evidence suggests that these agents might induce an immune-suppressive systemic immune response, indicated by increased expression of inhibitory checkpoint molecules such as programmed cell death 1 ligand 1 and 2, and that these changes could be associated with clinical response. Different radiotherapy modalities can induce distinct immune profiles, which can either activate or suppress immune-mediated tumour killing and the current preclinical models used for prostate cancer research are not yet optimal for studying the complexity of the radiotherapy-induced immune response.

Killing two birds with one stone: Abscopal effect mechanism and its application prospect in radiotherapy

Abscopal effects are characterized by the emergence of neoplasms in regions unrelated to the primary radiation therapy site, displaying a gradual attenuation or regression throughout the progression of radiation therapy, which have been of interest to scientists since Mole's proposal in 1953. The incidence of abscopal effects in radiation therapy is intricately linked to the immune system, with both innate and adaptive immune responses playing crucial roles. Biological factors impacting abscopal effects ultimately exert their influence on the intricate workings of the immune system. Although abscopal effects are rarely observed in clinical cases, the underlying mechanism remains uncertain. This article examines the biological and physical factors influencing abscopal effects of radiotherapy. Through a review of preclinical and clinical studies, this article aims to offer a comprehensive understanding of abscopal effects and proposes new avenues for future research in this field. The findings presented in this article serve as a valuable reference for researchers seeking to explore this topic in greater depth.

Low-dose targeted radionuclide therapy synergizes with CAR T cells and enhances tumor response

Ionizing radiation has garnered considerable attention as a combination partner for immunotherapy due to its potential immunostimulatory effects. In contrast to the more commonly used external beam radiation, we explored the feasibility of combining chimeric antigen receptor (CAR) T cell therapy with targeted radionuclide therapy (TRT), which is achieved by delivering β-emitting 177Lu-DOTATATE to tumor via tumor-infiltrating CAR T cells that express somatostatin receptor 2 (SSTR2). We hypothesized that the delivery of radiation to tumors could synergize with CAR T therapy, resulting in enhanced antitumor immunity and tumor response. To determine the optimal dosage and timing of 177Lu-DOTATATE treatment, we measured CAR T cell infiltration and expansion in tumors longitudinally through positron emission tomography (PET) using a SSTR2-specific positron-emitting radiotracer,18F-NOTA-Octreotide. In animals receiving CAR T cells and a low-dose (2.5 Gy) of TRT following the administration of 177Lu-DOTATATE, we observed a rapid regression of large subcutaneous tumors, which coincided with a dramatic increase in serum proinflammatory cytokines. Tumor burden was also reduced when a higher radiation dose (6 Gy) was delivered to the tumor. However, this higher dose led to cell death in both the tumor and CAR T cells. Our study suggests that there may exist an optimum range of TRT dosage that can enhance T cell activity and sensitize tumor cells to T cell killing, which may result in more durable tumor control compared to a higher radiation dose.

Nanomaterial-mediated modulation of the cGAS-STING signaling pathway for enhanced cancer immunotherapy

Despite the current promise of immunotherapy, many cancer patients still suffer from challenges such as poor immune response rates, resulting in unsatisfactory clinical efficacy of existing therapies. There is an urgent need to combine emerging biomedical discoveries and innovations in traditional therapies. Modulation of the cGAS-STING signalling pathway represents an important innate immunotherapy pathway that serves as a crucial DNA sensing mechanism in innate immunity and viral defense. It has attracted increasing attention as an emerging target for cancer therapy. The recent advancements in nanotechnology have led to the significant utilization of nanomaterials in cancer immunotherapy, owing to their exceptional physicochemical properties such as large specific surface area and efficient permeability. Given the rapid development of cancer immunotherapy driven by the cGAS-STING activation, this study reviews the latest research progress in employing nanomaterials to modulate this signaling pathway. Based on the introduction of the main activation mechanisms of cGAS-STING pathway, this review focuses on nanomaterials that mediate the agonists involved and effectively activate this signaling pathway. In addition, combination nanotherapeutics based on the activation of the cGAS-STING signaling pathway are also discussed, including emerging strategies combining nanoformulated agonists with chemotherapy, radiotherapy as well as other immunomodulation in tumor targeting therapy. STATEMENT OF SIGNIFICANCE: Given the rapid development of cancer immunotherapy driven by the cGAS / STING activation, this study reviews the latest research advances in the use of nanomaterials to modulate this signaling pathway. Based on the introduction of key cGAS-STING components and their activation mechanisms, this review focuses on nanomaterials that can mediate the corresponding agonists and effectively activate this signaling pathway. In addition, combination nanotherapies based on the activation of the cGAS-STING signaling pathway are also discussed, including emerging strategies combining nanoformulated agonists with chemotherapy, radiotherapy as well as immunomodulation in cancer therapy,.

Current trends in the promising immune checkpoint inhibition and radiotherapy combination for locally advanced and metastatic urothelial carcinoma

Locally advanced and metastatic urothelial carcinoma (UC) remains a challenging malignancy, though several novel therapeutic drugs have been developed in recent years. Over the past decade, immune checkpoint inhibitors (ICI) have shifted the paradigm of therapeutic strategies for UC; however, only a limited number of patients respond to ICI. Since radiotherapy (RT) is widely known to induce systemic immune activation, it may boost the efficacy of ICI. Conversely, RT also causes exhaustion of cytotoxic T cells, and the activation and recruitment of immunosuppressive cells; ICI may help overcome these immunosuppressive effects. Therefore, the combination of ICI and RT has attracted attention in recent years. The therapeutic benefits of this combination therapy and its optimal regimen have not yet been determined through prospective studies. Therefore, this review article aimed to provide an overview of the current preclinical and clinical studies that illustrate the underlying mechanisms and explore the optimization of the RT regimen along with the ICI and RT combination sequence. We also analyzed ongoing prospective studies on ICI and RT combination therapies for metastatic UC. We noted that the tumor response to ICI and RT combination seemingly differs among cancer types. Thus, our findings highlight the need for well-designed prospective trials to determine the optimal combination of ICI and RT for locally advanced and metastatic UC.

Immune Priming with Spatially Fractionated Radiation Therapy

PURPOSE OF REVIEW

This review aims to summarize the current preclinical and clinical evidence of nontargeted immune effects of spatially fractionated radiation therapy (SFRT). We then highlight strategies to augment the immunomodulatory potential of SFRT in combination with immunotherapy (IT).

RECENT FINDINGS

The response of cancer to IT is limited by primary and acquired immune resistance, and strategies are needed to prime the immune system to increase the efficacy of IT. Radiation therapy can induce immunologic effects and can potentially be used to synergize the effects of IT, although the optimal combination of radiation and IT is largely unknown. SFRT is a novel radiation technique that limits ablative doses to tumor subvolumes, and this highly heterogeneous dose deposition may increase the immune-rich infiltrate within the targeted tumor with enhanced antigen presentation and activated T cells in nonirradiated tumors. The understanding of nontargeted effects of SFRT can contribute to future translational strategies to combine SFRT and IT. Integration of SFRT and IT is an innovative approach to address immune resistance to IT with the overall goal of improving the therapeutic ratio of radiation therapy and increasing the efficacy of IT.

Stereotactic radiosurgery with immune checkpoint inhibitors for brain metastases: a meta-analysis study

BACKGROUND

Immune checkpoint inhibitors (ICIs) are an emerging tool in the treatment of brain metastases (BMs), Stereotactic radiosurgery (SRS), traditionally used for BMs, elicits an immune brain response and can act synergistically with ICIs. We aim to investigate the efficacy of ICI administered with SRS and determine the impact of timing on BM response.

METHODS

A systematical search was performed to identify potential studies concerning BMs managed with SRS alone or with SRS + ICI with relative timing administration (ICI concurrent with SRS, ICI nonconcurrent with SRS, SRS before ICI, SRS after ICI). The overall survival (OS), 12-month OS, local progression-free survival (LPFS), 12-month local brain control (LBC), distant progression-free survival (DPFS), 12-month distant brain control (DBC), and adverse events (intracranial hemorrhage, radionecrosis) were analyzed using the random-effects model.

RESULTS

A total of 16 retrospective studies with 1356 BM patients were included. Compared to nonconcurrent therapy, concurrent therapy revealed a significantly longer OS (HR= 1.43; p = 0.008) and 12-months LBC (HR = 1.91; p = 0.04), a similar 12-months DBC (HR = 1.12; p = 0.547) and higher complication rate (R = 0.77; p = 0.346). Concurrent therapy leads to a significantly higher OS compared to ICI before SRS (HR = 2.55; p = 0.0003).

CONCLUSION

The combination of SRS with ICI improves patients' clinical and radiological outcomes. The effectiveness of the combination is subject to the identification of an optimal therapeutic window.

Radiation and Immune Checkpoint Inhibitors: Combination Therapy for Treatment of Hepatocellular Carcinoma

The liver tumor immune microenvironment has been thought to possess a critical role in the development and progression of hepatocellular carcinoma (HCC). Despite the approval of immune checkpoint inhibitors (ICIs), such as programmed cell death receptor 1 (PD-1)/programmed cell death ligand 1 (PD-L1) and cytotoxic T lymphocyte associated protein 4 (CTLA-4) inhibitors, for several types of cancers, including HCC, liver metastases have shown evidence of resistance or poor response to immunotherapies. Radiation therapy (RT) has displayed evidence of immunosuppressive effects through the upregulation of immune checkpoint molecules post-treatment. However, it was revealed that the limitations of ICIs can be overcome through the use of RT, as it can reshape the liver immune microenvironment. Moreover, ICIs are able to overcome the RT-induced inhibitory signals, effectively restoring anti-tumor activity. Owing to the synergetic effect believed to arise from the combination of ICIs with RT, several clinical trials are currently ongoing to assess the efficacy and safety of this treatment for patients with HCC.

Modulation of CD8+ T Cell Responses by Radiotherapy-Current Evidence and Rationale for Combination with Immune Checkpoint Inhibitors

Radiotherapy for cancer has been known to affect the responses of immune cells, especially those of CD8+ T cells that play a pivotal role in anti-tumor immunity. Clinical success of immune checkpoint inhibitors led to an increasing interest in the ability of radiation to modulate CD8+ T cell responses. Recent studies that carefully analyzed CD8+ T cell responses following radiotherapy suggest the beneficial roles of radiotherapy on anti-tumor immunity. In addition, numerous clinical trials to evaluate the efficacy of combining radiotherapy with immune checkpoint inhibitors are currently undergoing. In this review, we summarize the current status of knowledge regarding the changes in CD8+ T cells following radiotherapy from various preclinical and clinical studies. Furthermore, key biological mechanisms that underlie such modulation, including both direct and indirect effects, are described. Lastly, we discuss the current evidence and essential considerations for harnessing radiotherapy as a combination partner for immune checkpoint inhibitors.

Immunotherapies landscape and associated inhibitors for the treatment of cervical cancer

Cervical cancer ranks as the fourth most common form of cancer worldwide. There is a large number of situations that may be examined in the developing world. The risk of contracting HPV (Human Papillomavirus) due to poor sanitation and sexual activity is mostly to blame for the disease's alarming rate of expansion. Immunotherapy is widely regarded as one of the most effective medicines available. The immunotherapy used to treat cervical cancer cells relies on inhibitors that block the immune checkpoint. The poly adenosine diphosphate ribose polymer inhibited cervical cancer cells by activating both the programmed death 1 (PD-1) and programmed death ligand 1 (CTLA-1) checkpoints, a strategy that has been shown to have impressive effects. Yet, immunotherapy directed towards tumors that have already been invaded by lymphocytes leaves a positive imprint on the healing process. Immunotherapy is used in conjunction with other treatments, including chemotherapy and radiation, to provide faster and more effective outcomes. In this combination therapy, several medications such as Pembrolizumab, Durvalumab, Atezolizumab, and so on are employed in clinical trials. Recent developments and future predictions suggest that vaccinations will soon be developed with the dual goal of reducing the patient's susceptibility to illness while simultaneously strengthening their immune system. Many clinical and preclinical studies are now investigating the effectiveness of immunotherapy in slowing the progression of cervical cancer. The field of immunotherapy is expected to witness more progress toward improving outcomes. Immunotherapies landscape and associated inhibitors for the treatment of Cervical Cancer.

Selective multimodal bladder-sparing therapy for muscle-invasive bladder cancer: the present and the future

INTRODUCTION

Despite the lack of level 1 evidence, selective bladder-sparing therapy using trimodal therapy is currently recommended by guidelines as a standard of care in patients with non-metastatic, muscle-invasive bladder cancer who are eligible for the treatment.

AREAS COVERED

This article reviews major studies of selective, bladder-sparing therapy utilizing multiple modalities for muscle-invasive bladder cancer and those comparing the oncological outcomes between bladder-sparing therapy and radical cystectomy. Also discussed are predictive biomarkers potentially capable of guiding treatment decisions by patients with muscle-invasive bladder cancer and a novel strategy for boosting the antitumor immune response in bladder-sparing therapy. PubMed databases were searched for records of 30 June 2023 or earlier.

EXPERT OPINION

Selective, bladder-sparing therapy appears to be underutilized at present. To promote its use, measures should be taken to facilitate the referral of eligible patients to specialist centers and broaden the number of facilities providing the therapy. Recent studies have suggested a prognostic benefit of radiotherapy for the primary lesion in patients with metastatic bladder cancer. Given that irradiation can induce the abscopal effect, particularly in combination with immune checkpoint inhibitors, demand for bladder-sparing therapies may increase in the context of treatments for metastases.

The Histological Background of Recurrence in Laryngeal Squamous Cell Carcinoma: An Insight into the Modifications of Tumor Microenvironment

Recurrent laryngeal carcinoma presents differences from the primary tumor that largely depend on the treatment. In this article, we review the histologic and molecular treatment-induced changes that may affect the diagnosis of recurrent laryngeal carcinoma, the assessment of predictive markers, and the response to treatment with immune checkpoint inhibitors. Radiotherapy induces profound modifications that are strictly related to necrosis of different tissue components, fibrosis, and damage of the tumor vessels. Postradiotherapy recurrent/persistent laryngeal squamous cell carcinoma typically presents a discohesive growth pattern within a fibrotic background associated with significant changes of the tumor immune microenvironment, with both important immunosuppressive and immunostimulatory effects. Overall, the increase of immunoregulatory cells and immune checkpoints such as CTLA-4, TIM-3, PD-1, and PD-L1 induced by radiotherapy and chemotherapy strongly supports the use of immune checkpoint inhibitors in recurrent/persistent laryngeal carcinoma. Future studies aiming to identify predictive factors of the response to immune checkpoint inhibitors should consider such treatment-induced modifications.

Mechanistic rationales for combining immunotherapy with radiotherapy

Immunotherapy consisted mainly of immune checkpoint inhibitors (ICIs) has led to significantly improved antitumor response. However, such response has been observed only in tumors possessing an overall responsive tumor immune micro-environment (TIME), in which the presence of functional tumor-infiltrating lymphocytes (TILs) is critical. Various mechanisms of immune escape from immunosurveillance exist, leading to different TIME phenotypes in correlation with primary or acquired resistance to ICIs. Radiotherapy has been shown to induce antitumor immunity not only in the irradiated primary tumor, but also at unirradiated distant sites of metastases. Such antitumor immunity is mainly elicited by radiation's stimulatory effects on antigenicity and adjuvanticity. Furthermore, it may be significantly augmented when irradiation is combined with immunotherapy, such as ICIs. Therefore, radiotherapy represents one potential therapeutic strategy to restore anti-tumor immunity in tumors presenting with an unresponsive TIME. In this review, the generation of anti-tumor immunity, its impairment, radiation's immunogenic properties, and the antitumor effects of combining radiation with immunotherapy will be comprehensively discussed.

CAR T cell-based immunotherapy and radiation therapy: potential, promises and risks

CAR T cell-based therapies have revolutionized the treatment of hematological malignancies such as leukemia and lymphoma within the last years. In contrast to the success in hematological cancers, the treatment of solid tumors with CAR T cells is still a major challenge in the field and attempts to overcome these hurdles have not been successful yet. Radiation therapy is used for management of various malignancies for decades and its therapeutic role ranges from local therapy to a priming agent in cancer immunotherapy. Combinations of radiation with immune checkpoint inhibitors have already proven successful in clinical trials. Therefore, a combination of radiation therapy may have the potential to overcome the current limitations of CAR T cell therapy in solid tumor entities. So far, only limited research was conducted in the area of CAR T cells and radiation. In this review we will discuss the potential and risks of such a combination in the treatment of cancer patients.

Cell death, therapeutics, and the immune response in cancer

Induction of cell death is inexorably linked with cancer therapy, but this can also initiate wound-healing processes that have been linked to cancer progression and therapeutic resistance. Here we describe the contribution of apoptosis and the lytic cell death pathways in the response to therapy (including chemotherapy and immunotherapy). We also discuss how necroptosis, pyroptosis, and ferroptosis function to promote tumor immunogenicity, along with emerging findings that these same forms of death can paradoxically contribute to immune suppression and tumor progression. Understanding the duality of cell death in cancer may allow for the development of therapeutics that shift the balance towards regression.

Novel unconventional radiotherapy techniques: Current status and future perspectives - Report from the 2nd international radiation oncology online seminar

•Improvement of therapeutic ratio by novel unconventional radiotherapy approaches.•Immunomodulation using high-dose spatially fractionated radiotherapy.•Boosting radiation anti-tumor effects by adding an immune-mediated cell killing.

Combining radiotherapy and NK cell-based therapies: The time has come

Natural killer (NK) cells are innate lymphoid cells that play an essential role in the anti-tumor response through immunosurveillance, multiple mechanisms of cytotoxicity and the synthesis of cytokines modulating the immune tumor microenvironment (TME). After the dramatic advances in immunotherapy targeting T cells including the success of checkpoint inhibitors or autologous chimeric antigen receptor (CAR) expressing T cells in clinical practice, NK cells have gained growing interest for the development of new therapies. Although NK cells have shown promising responses in leukemia patients, the effects of NK-targeted therapies are currently limited in the treatment of solid tumors. Thus, radiotherapy could provide a valuable solution to improve treatments targeting NK cells. Indeed, ionizing radiations represent a powerful immuno-modulator that can either induce a pro-inflammatory and anti-tumor TME, or conversely lead to immunosuppression of effector immune cells in favor of tumor growth and therapeutic escape, depending on how it is delivered and tumor models. However, the effects of ionizing radiation on NK cells are only partially understood. Therefore, we review the effects of radiotherapy on the NK cell-mediated anti-tumor response, and propose potential strategies to reinvigorate NK cells by combining radiotherapy with NK cell-targeted therapies.

Radiotherapy/Chemotherapy-Immunotherapy for Cancer Management: From Mechanisms to Clinical Implications

Cancer immunotherapy has drawn much attention because it can restart the recognition and killing function of the immune system to normalize the antitumor immune response. However, the role of radiotherapy and chemotherapy in cancer treatment cannot be ignored. Due to cancer heterogeneity, combined therapy has become a new trend, and its efficacy has been confirmed in many studies. This review discussed the clinical implications and the underlying mechanisms of cancer immunotherapy in combination with radiotherapy or chemotherapy, offering an outline for clinicians as well as inspiration for future research.

Targeted Radiation and Immune Therapies-Advances and Opportunities for the Treatment of Prostate Cancer

Prostate cancer is the most diagnosed malignancy in men in the United States and the second leading cause of cancer-related death. For localized disease, radiation therapy is a standard treatment that is often curative. For metastatic disease, radiation therapy has been primarily used for palliation, however, several newer systemic radiation therapies have been demonstrated to significantly improve patient outcomes and improve survival. In particular, several targeted radionuclide therapies have been approved for the treatment of advanced-stage cancer, including strontium-89, samarium-153, and radium-223 for bone-metastatic disease, and lutetium-177-labeled PSMA-617 for patients with prostate-specific membrane antigen (PSMA)-expressing metastatic castration-resistant prostate cancer (mCRPC). Contrarily, immune-based treatments have generally demonstrated little activity in advanced prostate cancer, with the exception of the autologous cellular vaccine, sipuleucel-T. This has been attributed to the presence of an immune-suppressive prostate cancer microenvironment. The ability of radiation therapy to not only eradicate tumor cells but also potentially other immune-regulatory cells within the tumor immune microenvironment suggests that targeted radionuclide therapies may be well poised to combine with immune-targeted therapies to eliminate prostate cancer metastases more effectively. This review provides an overview of the recent advances of targeted radiation agents currently approved for prostate cancer, and those being investigated in combination with immunotherapy, and discusses the challenges as well as the opportunities in this field.

Immunomodulatory Therapy in Head and Neck Squamous Cell Carcinoma: Recent Advances and Clinical Prospects

The immune system plays a significant role in the development, invasion, progression, and metastasis of head and neck cancer. Over the last decade, the emergence of immunotherapy has irreversibly altered the paradigm of cancer treatment. The current treatment modalities for head and neck squamous cell carcinoma (HNSCC) include surgery, radiotherapy, and adjuvant or neoadjuvant chemotherapy which has failed to provide satisfactory clinical outcomes. To encounter this, there is a need for a novel or targeted therapy such as immunological targets along with conventional treatment strategy for optimal therapeutic outcomes. The immune system can contribute to promoting metastasis, angiogenesis, and growth by exploiting the tumor's influence on the microenvironment. Immunological targets have been found effective in recent clinical studies and have shown promising results. This review outlines the important immunological targets and the medications acting on them that have already been explored, are currently under clinical trials and are further being targeted.

Radiation therapy in the era of immune treatment for hepatocellular carcinoma

Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment in recent years and provide new opportunities to treat hepatocellular carcinoma (HCC). To date, several ICIs have been approved by the FDA for advanced HCC in first-line or second-line therapy. Downstaging conversion therapy for potentially resectable HCC to provide opportunities for surgical intervention is challenging. ICIs have become a hot spot in this field due to their high response rate. However, HCC has various etiologies and can evade the immune system through multiple mechanisms, which limit the efficacy of ICI monotherapy and demand novel combination strategies. Radiation therapy (RT) is also a candidate for conversion therapy in HCC and is currently gaining increasing attention as a good combination partner with ICIs due to its ability to modulate the tumor microenvironment. In this review, we illustrate the current indications for ICIs and RT in HCC, the rationale for their synergistic combination, and the current clinical trials in combination therapy. We also speculate on predictive biomarkers and novel future strategies to further enhance the efficacy of this combination. This review aims to provide references for future research on radiation and immunotherapy to arrive at a promising new era of HCC treatment.

In-plane Extended Nano-coulter Counter (XnCC) for the Label-free Electrical Detection of Biological Particles

We report an in-plane extended nanopore Coulter counter (XnCC) chip fabricated in a thermoplastic via imprinting. The fabrication of the sensor utilized both photolithography and focused ion beam milling to make the microfluidic network and the in-plane pore sensor, respectively, in Si from which UV resin stamps were generated followed by thermal imprinting to produce the final device in the appropriate plastic (cyclic olefin polymer, COP). As an example of the utility of this in-plane extended nanopore sensor, we enumerated SARS-CoV-2 viral particles (VPs) affinity-selected from saliva and extracellular vesicles (EVs) affinity-selected from plasma samples secured from mouse models exposed to different ionizing radiation doses.

Radiotherapy induced immunogenic cell death by remodeling tumor immune microenvironment

Emerging evidence indicates that the induction of radiotherapy(RT) on the immunogenic cell death (ICD) is not only dependent on its direct cytotoxic effect, changes in the tumor immune microenvironment also play an important role in it. Tumor immune microenvironment (TIME) refers to the immune microenvironment that tumor cells exist, including tumor cells, inflammatory cells, immune cells, various signaling molecules and extracellular matrix. TIME has a barrier effect on the anti-tumor function of immune cells, which can inhibit all stages of anti-tumor immune response. The remodeling of TIME caused by RT may affect the degree of immunogenicity, and make it change from immunosuppressive phenotype to immunostimulatory phenotype. It is of great significance to reveal the causes of immune escape of tumor cells, especially for the treatment of drug-resistant tumor. In this review, we focus on the effect of RT on the TIME, the mechanism of RT in reversing the TIME to suppress intrinsic immunity, and the sensitization effect of the remodeling of TIME caused by RT on the effectiveness of immunotherapy.

Dying of Stress: Chemotherapy, Radiotherapy, and Small-Molecule Inhibitors in Immunogenic Cell Death and Immunogenic Modulation

Innovative strategies to re-establish the immune-mediated destruction of malignant cells is paramount to the success of anti-cancer therapy. Accumulating evidence suggests that radiotherapy and select chemotherapeutic drugs and small molecule inhibitors induce immunogenic cell stress on tumors that results in improved immune recognition and targeting of the malignant cells. Through immunogenic cell death, which entails the release of antigens and danger signals, and immunogenic modulation, wherein the phenotype of stressed cells is altered to become more susceptible to immune attack, radiotherapies, chemotherapies, and small-molecule inhibitors exert immune-mediated anti-tumor responses. In this review, we discuss the mechanisms of immunogenic cell death and immunogenic modulation and their relevance in the anti-tumor activity of radiotherapies, chemotherapies, and small-molecule inhibitors. Our aim is to feature the immunological aspects of conventional and targeted cancer therapies and highlight how these therapies may be compatible with emerging immunotherapy approaches.

The molecular basis of immuno-radiotherapy

PURPOSE

Radiotherapy (RT) and immunotherapy are powerful anti-tumor treatment modalities. Experimental research has demonstrated an important interplay between the cytotoxic effects of RT and the immune system. This systematic review provides an overview of the basics of anti-tumor immunity and focuses on the mechanisms underlying the interplay between RT and immune anti-tumor response that set the molecular basis of immuno-RT.

CONCLUSIONS

An 'immunity acquired equilibrium' mimicking tumor dormancy can be achieved post-irradiation treatment, with the balance shifted toward tumor eradication or regrowth when immune cells' cytotoxic effects or cancer proliferation rate prevail, respectively. RT has both immunosuppressive and immune-enhancing properties. The latter effect is also known as radio-vaccination. Its mechanisms involve up- or down-regulation of membrane molecules, such as PD-L1, HLA-class-I, CD80/86, CD47, and Fas/CD95, that play a vital role in immune checkpoint pathways and increased cytokine expression (e.g. INFα,β,γ, IL1,2, and TNFα) by cancer or immune cells. Moreover, the interactions of radiation with the tumor microenvironment (fibroblasts, tumor-infiltrating lymphocytes, monocytes, and dendritic cells are also an important component of radio-vaccination. Thus, RT may have anti-tumor vaccine properties, whose sequels can be exploited by immunotherapy agents to treat different cancer subtypes effectively.

Radiovaccination Strategy for Cancer Treatment Integrating Photodynamic Therapy-Generated Vaccines with Radiotherapy

Therapeutic cancer vaccines have become firmly established as a reliable and proficient form of tumor immunotherapy. They represent a promising approach for substantial advancements in the successful treatment of malignant diseases. One attractive vaccine strategy is using, as the vaccine material, the whole tumor cells treated ex vivo by rapid tumor ablation therapies that instigate stress signaling responses culminating in immunogenic cell death (ICD). One such treatment is photodynamic therapy (PDT). The underlying mechanisms and critical elements responsible for the potency of these vaccines are discussed in this review. Radiotherapy has emerged as a suitable component for the combined therapy protocols with the vaccines. Arguments and prospects for optimizing tumor control using a radiovaccination strategy involving X-ray irradiation plus PDT vaccines are presented, together with the findings supporting its validity.

A Review of the Abscopal Effect in the Era of Immunotherapy

The abscopal effect is a systemic immune response mediated by the effects of radiation on the immune system. This effect has been observed in a number of cancer types in addition to lung cancer, including but not limited to renal cell carcinoma, hepatocellular carcinoma, lymphoma, and melanoma. The combination of radiation therapy and immune checkpoint inhibition (ICI) acts at several stages of the antitumor response, suggesting a mechanism of synergy between the two modalities. This review focuses on recent advances in the understanding of the effect of radiation and immunotherapy in the context of the abscopal effect.

Primary and secondary immune checkpoint inhibitors resistance in colorectal cancer: Key mechanisms and ways to overcome resistance

Immune checkpoint inhibitors (ICIs) have significantly advanced colorectal cancer treatment in recent years. Antibodies that target the proteins programmed cell death-1 (PD-1), programmed cell death-1 ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) are among the ICIs that are currently being used in clinical practice. However, in colorectal cancer, ICI's effectiveness is limited to a fraction of patients with microsatellite instability-high (MSI-H), which only accounts for about 5% of advanced cases. The tumor microenvironment and intrinsic changes in tumor cells are just a couple of the many mechanisms that play a role in ICI primary or secondary resistance. In order to advance precision medicine and broaden the population benefiting from ICI, this paper highlights the main underlying mechanisms of ICIs resistance and suggested techniques to overcome it.

Efficacy and Safety of Combined Brain Stereotactic Radiotherapy and Immune Checkpoint Inhibitors in Non-Small-Cell Lung Cancer with Brain Metastases

Background: To analyze the outcomes of patients with brain metastases (BM) from non-small cell lung cancer (NSCLC) treated with immunotherapy (IT) and stereotactic radiotherapy (SRT) and to study the impact of the sequence between the two modalities. Methods: The authors reviewed the records of 51 patients with 84 BM from NSCLC treated at Institut Curie with IT and SRT. BM were categorized into three groups: ‘SRT before IT’, ‘concurrent SRT and IT’, and ‘SRT after IT.’ Regional progression-free interval (R-PFI) and overall survival (OS) were estimated using the Kaplan–Meier method. Results: After a median follow-up from SRT of 22.5 months (2.7–47.3), the 1-year and 2-year OS were 69.7% (95%CI [58.0–83.8]) and 44.0% [30.6–63.2], respectively. Concerning distant intracranial control, the 1-year and 2-year R-PFI were 40.1% [30.1–53.3] and 35.2% [25.1–49.4], respectively. Moreover, one-year R-PFI in ‘SRT before IT’, ‘concurrent SRT and IT’, and ‘SRT after IT’ groups were 24.1%, 49.6%, and 34.2%, respectively (p = 0.094). The type of therapeutic sequence did not appear to impact the risk of brain necrosis. Conclusions: The concurrent administration of SRT and IT appeared to offer the best locoregional control, without increasing the risk of toxicity, compared to patients treated with SRT before or after IT.

Immunotherapy for EGFR-mutant advanced non-small-cell lung cancer: Current status, possible mechanisms and application prospects

Immune checkpoint inhibitors (ICIs) are effective against advanced and even perioperative non-small-cell lung cancer (NSCLC) and result in durable clinical benefit, regardless of programmed death ligand-1 (PD-L1) expression status in cancer. Existing clinical evidence shows that the effect of immunotherapy in patients with EGFR-mutant NSCLC after the development of tyrosine kinase inhibitor (TKI) resistance is not satisfactory. However, compared with monotherapy, ICIs combined with chemotherapy can improve the efficacy. Encouragingly, compared with that of patients with sensitive mutations, the progression-free survival of patients with rare mutations who were treated with ICIs was increased. Adequately maximizing the efficacy of ICIs in EGFR-mutant NSCLC patients is worth exploring. In this review, we described preclinical and clinical studies of ICIs or combined therapy for EGFR-mutant NSCLC. We further focused on EGFR mutations and the cancer immune response, with particular attention given to the role of EGFR activation in the cancer-immunity cycle. The mechanisms for the natural resistance to ICIs were explored to identify corresponding countermeasures that made more EGFR-mutant NSCLC patients benefit from ICIs.

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.

HIF-1α Inhibition Improves Anti-Tumor Immunity and Promotes the Efficacy of Stereotactic Ablative Radiotherapy (SABR)

Simple Summary

Stereotactic ablative radiotherapy (SABR), which irradiates tumors with high-dose radiation per fraction, promotes anti-tumor immunity by stimulating various immune processes. SABR also induces vascular damage and obstructs blood flow, thereby increasing tumor hypoxia and upregulation of hypoxia-inducible factors HIF-1α and HIF-2α, master transcription factors for the cellular response to hypoxia. HIF-1α and HIF-2α are key players in the upregulation of immune suppression in hypoxia. Therefore, the radiation-induced increase in anti-tumor immunity is masked by the HIF-mediated immune suppression. Pre-clinical experiments show that inhibition of HIF-1α effectively prevents immune suppression and improves anti-tumor immunity. A combination of HIF-1α inhibitors with immunotherapy with checkpoint blocking antibodies may represent a novel approach to boost anti-tumor immunity and enhance the efficacy of SABR.

Abstract

High-dose hypofractionated radiation such as SABR (stereotactic ablative radiotherapy) evokes an anti-tumor immune response by promoting a series of immune-stimulating processes, including the release of tumor-specific antigens from damaged tumor cells and the final effector phase of immune-mediated lysis of target tumor cells. High-dose hypofractionated radiation also causes vascular damage in tumors, thereby increasing tumor hypoxia and upregulation of hypoxia-inducible factors HIF-1α and HIF-2α, the master transcription factors for the cellular response to hypoxia. HIF-1α and HIF-2α are critical factors in the upregulation of immune suppression and are the master regulators of immune evasion of tumors. Consequently, SABR-induced increase in anti-tumor immunity is counterbalanced by the increase in immune suppression mediated by HIFα. Inhibition of HIF-1α with small molecules such as metformin downregulates immunosuppressive pathways, including the expression of immune checkpoints, and it improves or restores the anti-tumor immunity stimulated by irradiation. Combinations of HIFα inhibitors, particularly HIF-1α inhibitors, with immune checkpoint blocking antibodies may represent a novel approach to boost the overall anti-tumor immune profile in patients and thus enhance outcomes after SABR.

Narrative Review of Synergistics Effects of Combining Immunotherapy and Stereotactic Radiation Therapy

Stereotactic radiotherapy (SRT) has become an attractive treatment modality in full bloom in recent years by presenting itself as a safe, noninvasive alternative to surgery to control primary or secondary malignancies. Although the focus has been on local tumor control as the therapeutic goal of stereotactic radiotherapy, rare but intriguing observations of abscopal (or out-of-field) effects have highlighted the exciting possibility of activating antitumor immunity using high-dose radiation. Furthermore, immunotherapy has revolutionized the treatment of several types of cancers in recent years. However, resistance to immunotherapy often develops. These observations have led researchers to combine immunotherapy with SRT in an attempt to improve outcomes. The benefits of this combination would come from the stimulation and suppression of various immune pathways. Thus, in this review, we will first discuss the immunomodulation induced by SRT with the promising results of preclinical studies on the changes in the immune balance observed after SRT. Then, we will discuss the opportunities and risks of the combination of SRT and immunotherapy with the preclinical and clinical data available in the literature. Furthermore, we will see that many perspectives are conceivable to potentiate the synergistic effects of this combination with the need for prospective studies to confirm the encouraging data.

Escaping Death: How Cancer Cells and Infected Cells Resist Cell-Mediated Cytotoxicity

Cytotoxic lymphocytes are critical in our immune defence against cancer and infection. Cytotoxic T lymphocytes and Natural Killer cells can directly lyse malignant or infected cells in at least two ways: granule-mediated cytotoxicity, involving perforin and granzyme B, or death receptor-mediated cytotoxicity, involving the death receptor ligands, tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) and Fas ligand (FasL). In either case, a multi-step pathway is triggered to facilitate lysis, relying on active pro-death processes and signalling within the target cell. Because of this reliance on an active response from the target cell, each mechanism of cell-mediated killing can be manipulated by malignant and infected cells to evade cytolytic death. Here, we review the mechanisms of cell-mediated cytotoxicity and examine how cells may evade these cytolytic processes. This includes resistance to perforin through degradation or reduced pore formation, resistance to granzyme B through inhibition or autophagy, and resistance to death receptors through inhibition of downstream signalling or changes in protein expression. We also consider the importance of tumour necrosis factor (TNF)-induced cytotoxicity and resistance mechanisms against this pathway. Altogether, it is clear that target cells are not passive bystanders to cell-mediated cytotoxicity and resistance mechanisms can significantly constrain immune cell-mediated killing. Understanding these processes of immune evasion may lead to novel ideas for medical intervention.

Comparison of stereotactic body radiotherapy and radiofrequency ablation for early-stage non-small cell lung cancer: a systematic review and meta-analysis

Background

Stereotactic body radiation therapy (SBRT) and radiofrequency ablation (RFA) are recommended for patients with inoperable early-stage non-small cell lung cancer (NSCLC), with both offering promising results. However, it is largely unknown which of these two treatment modalities provides superior benefits for patients. Therefore, this systematic review and meta-analysis compared clinical outcomes and safety between SBRT and RFA in patients with inoperable early-stage NSCLC.

Methods

Eligible studies published between 2001 and 2020 were obtained through a comprehensive search of the PubMed, Medline, Embase, and Cochrane Library databases. Original English-language studies on the treatment of early-stage NSCLC with SBRT or RFA were included. Local control (LC) rates, overall survival (OS) rates, and adverse events were obtained by pooled analyses.

Results

Eighty-seven SBRT studies (12,811 patients) and 18 RFA studies (1,535 patients) met the eligibility criteria. For SBRT, the LC rates (with 95% confidence intervals) at 1, 2, 3, and 5 years were 98% (97-98%), 95% (95-96%), 92% (91-93%), and 92% (91-93%), respectively, which were significantly higher than those for RFA [75% (69-82%), 31% (22-39%), 67% (58-76%), and 41% (30-52%), respectively] (P<0.01). There were no significant differences in short-term OS between SBRT and RFA [1-year OS rate: 87% (86-88%) versus 89% (88-91%), P=0.07; 2-year OS rate: 71% (69-72%) versus 69% (64-74%), P=0.42]. Regarding long-term OS, the 3- and 5-year OS rates for SBRT were 58% (56-59%) and 39% (37-40%), respectively, which were significantly (P<0.01) superior to those for RFA [48% (45-51%) and 21% (19-23%), respectively]. The most common complication of SBRT was radiation pneumonitis (grade ≥2), making up 9.1% of patients treated with SBRT, while pneumothorax was the most common complication of RFA, making up 27.2% of patients treated with RFA.

Discussion

Compared with RFA, SBRT has superior LC and long-term OS rates but similar short-term OS rates. Prospective randomized trials with large sample sizes comparing the efficacy of SBRT and RFA are warranted.

Cancer Vaccine in Cold Tumors: Clinical Landscape, Challenges, and Opportunities

The idea of cancer immunotherapy is to stimulate the immune system to fight tumors without destroying normal cells. One of the anticancer therapy methods, among many, is based on the use of cancer vaccines that contain tumor antigens in order to induce immune responses against tumors. However, clinical trials have shown that the use of such vaccines as a monotherapy is ineffective in many cases, since they do not cause a strong immune response. Particular tumors are resistant to immunotherapy due to the absence or insufficient infiltration of tumors with CD8+ T cells, and hence, they are called cold or non-inflamed tumors. Cold tumors are characterized by a lack of CD8+ T cell infiltration, the presence of anti-inflammatory myeloid cells, tumor-associated M2 macrophages, and regulatory T cells. It is very important to understand which stage of the antitumor response does not work properly in order to use the right strategy for the treatment of patients. Applying other therapeutic methods alongside cancer vaccines can be more rational for cold tumors which do not provoke the immune system strongly. Herein, we indicate some combinational therapies that have been used or are in progress for cold tumor treatment alongside vaccines.

Effective Combinations of Immunotherapy and Radiotherapy for Cancer Treatment

Though single tumor immunotherapy and radiotherapy have significantly improved the survival rate of tumor patients, there are certain limitations in overcoming tumor metastasis, recurrence, and reducing side effects. Therefore, it is urgent to explore new tumor treatment methods. The new combination of radiotherapy and immunotherapy shows promise in improving therapeutic efficacy and reducing recurrence by enhancing the ability of the immune system to recognize and eradicate tumor cells, to overcome tumor immune tolerance mechanisms. Nanomaterials, as new drug-delivery-system materials of the 21st century, can maintain the activity of drugs, improve drug targeting, and reduce side effects in tumor immunotherapy. Additionally, nanomaterials, as radiosensitizers, have shown great potential in tumor radiotherapy due to their unique properties, such as light, heat, electromagnetic effects. Here, we review the mechanisms of tumor immunotherapy and radiotherapy and the synergy of radiotherapy with multiple types of immunotherapies, including immune checkpoint inhibitors (ICIs), tumor vaccines, adoptive cell therapy, and cytokine therapy. Finally, we propose the potential for nanomaterials in tumor radiotherapy and immunotherapy.

Radiotherapy transiently reduces the sensitivity of cancer cells to lymphocyte cytotoxicity

The impact of radiotherapy on the interaction between immune cells and cancer cells is important not least because radiotherapy can be used alongside immunotherapy as a cancer treatment. Unexpectedly, we found that X-ray irradiation of cancer cells induced significant resistance to natural killer (NK) cell killing. This was true across a wide variety of cancer-cell types as well as for antibody-dependent cellular cytotoxicity. Resistance appeared 72 h postirradiation and persisted for 2 wk. Resistance could also occur independently of radiotherapy through pharmacologically induced cell-cycle arrest. Crucially, multiple steps in NK-cell engagement, synapse assembly, and activation were unaffected by target cell irradiation. Instead, radiotherapy caused profound resistance to perforin-induced calcium flux and lysis. Resistance also occurred to a structurally similar bacterial toxin, streptolysin O. Radiotherapy did not affect the binding of pore-forming proteins at the cell surface or membrane repair. Rather, irradiation instigated a defect in functional pore formation, consistent with phosphatidylserine-mediated perforin inhibition. In vivo, radiotherapy also led to a significant reduction in NK cell-mediated clearance of cancer cells. Radiotherapy-induced resistance to perforin also constrained chimeric antigen receptor T-cell cytotoxicity. Together, these data establish a treatment-induced resistance to lymphocyte cytotoxicity that is important to consider in the design of radiotherapy-immunotherapy protocols.

Restoring FAS Expression via Lipid-Encapsulated FAS DNA Nanoparticle Delivery Is Sufficient to Suppress Colon Tumor Growth In Vivo

Simple Summary

A key feature of human colorectal tumor is loss of FAS expression. FAS is the death receptor for FASL of activated T cells. Loss of FAS expression therefore may promote tumor cell immune escape. We aimed at determining whether restoring FAS expression is sufficient to suppress colorectal tumor growth. Mouse and human FAS cDNA was synthesized and encapsulated into cationic lipid nanoparticle DOTAP-Cholesterol to formulate DOTAP-Chol-mFAS and DOTAP-Chol-hFAS, respectively. Restoring FAS expression in metastatic mouse colon-tumor cells enabled FASL-induced elimination of FAS⁺ tumor cells in vitro and suppressed colon-tumor growth and progression in tumor-bearing mice in vivo. Restoring FAS expression induced FAS receptor auto-oligomerization and tumor cell auto-apoptosis in metastatic human colon-tumor cells in vitro. DOTAP-Chol-hFAS therapy is also sufficient to suppress metastatic human colon tumor xenograft growth in athymic mice. Tumor-selective delivery of FAS DNA nanoparticle is potentially an effective therapy for human colorectal cancer.

Abstract

A hallmark of human colorectal cancer is lost expression of FAS, the death receptor for FASL of cytotoxic T lymphocytes (CTLs). However, it is unknown whether restoring FAS expression alone is sufficient to suppress csolorectal-cancer development. The FAS promoter is hypermethylated and inversely correlated with FAS mRNA level in human colorectal carcinomas. Analysis of single-cell RNA-Seq datasets revealed that FAS is highly expressed in epithelial cells and immune cells but down-regulated in colon-tumor cells in human colorectal-cancer patients. Codon usage-optimized mouse and human FAS cDNA was designed, synthesized, and encapsulated into cationic lipid to formulate nanoparticle DOTAP-Chol-mFAS and DOTAP-Chol-hFAS, respectively. Overexpression of codon usage-optimized FAS in metastatic mouse colon-tumor cells enabled FASL-induced elimination of FAS⁺ tumor cells in vitro, suppressed colon tumor growth, and increased the survival of tumor-bearing mice in vivo. Overexpression of codon-optimized FAS-induced FAS receptor auto-oligomerization and tumor cell auto-apoptosis in metastatic human colon-tumor cells. DOTAP-Chol-hFAS therapy is also sufficient to suppress metastatic human colon tumor xenograft growth in athymic mice. DOTAP-Chol-mFAS therapy exhibited no significant liver toxicity. Our data determined that tumor-selective delivery of FAS DNA nanoparticles is sufficient for suppression of human colon tumor growth in vivo.

The Research Progress of PD-1/PD-L1 Inhibitors Enhancing Radiotherapy Efficacy

Approximately 60%–70% of patients with malignant tumours require radiotherapy. The clinical application of immune checkpoint inhibitors (ICIs), such as anti-PD-1/PD-L1, has revolutionized cancer treatment and greatly improved the outcome of a variety of cancers by boosting host immunity.However, radiotherapy is a double-edged sword for PD-1/PD-L immunotherapy. Research on how to improve radiotherapy efficacy using PD-1/PD-L1 inhibitor is gaining momentum. Various studies have reported the survival benefits of the combined application of radiotherapy and PD-1/PD-L1 inhibitor. To fully exerts the immune activation effect of radiotherapy, while avoiding the immunosuppressive effect of radiotherapy as much as possible, the dose selection, segmentation mode, treatment timing and the number of treatment sites of radiotherapy play a role. Therefore, we aim to review the effect of radiotherapy combined with anti-PD-1/PD-L1 on the immune system and its optimization.

Dendritic Cells and Cancer Immunotherapy: The Adjuvant Effect

Dendritic cells (DCs) are immune specialized cells playing a critical role in promoting immune response against antigens, and may represent important targets for therapeutic interventions in cancer. DCs can be stimulated ex vivo with pro-inflammatory molecules and loaded with tumor-specific antigen(s). Protocols describing the specific details of DCs vaccination manufacturing vary widely, but regardless of the employed protocol, the DCs vaccination safety and its ability to induce antitumor responses is clearly established. Many years of studies have focused on the ability of DCs to provide overall survival benefits at least for a selection of cancer patients. Lessons learned from early trials lead to the hypothesis that, to improve the efficacy of DCs-based immunotherapy, this should be combined with other treatments. Thus, the vaccine’s ultimate role may lie in the combinatorial approaches of DCs-based immunotherapy with chemotherapy and radiotherapy, more than in monotherapy. In this review, we address some key questions regarding the integration of DCs vaccination with multimodality therapy approaches for cancer treatment paradigms.

Radioembolisation with Y90-resin microspheres followed by nivolumab for advanced hepatocellular carcinoma (CA 209-678): a single arm, single centre, phase 2 trial

BACKGROUND

Therapeutic synergism between radiotherapy and immune checkpoint blockade has been observed in preclinical models of hepatocellular carcinoma. We aimed to study the safety and efficacy of sequential radioembolisation with yttrium-90-resin microspheres (Y90-radioembolisation) followed by nivolumab in patients with advanced hepatocellular carcinoma.

METHODS

Patients with Child-Pugh A cirrhosis and advanced hepatocellular carcinoma not suitable for curative surgery were treated with Y90-radioembolisation followed by intravenous nivolumab 240 mg 21 days after Y90-radioembolisation and every 2 weeks thereafter. The primary endpoint, assessed in the per-protocol population, was the objective response rate, determined by RECIST version 1.1, defined as the proportion of patients with a confirmed complete or partial response observed for lesions both within and outside the Y90-radioembolisation field. This study is registered with ClinicalTrials.gov, NCT03033446 and has been completed.

FINDINGS

40 patients were enrolled, of whom 36 received Y90-radioembolisation followed by nivolumab. One (3%) patient had a complete response and ten (28%) had a partial response; the objective response rate was 30·6% (95% CI 16·4-48·1). The most common treatment-related adverse events of any grade were pruritus (18 [50%] of 36 patients) and maculopapular rash (13 [36%]). Two (6%) patients experienced grade 3-4 treatment-related adverse events: one patient had a grade 3 increase in alanine aminotransferase levels, grade 3 bilirubin increase, and grade 4 increase in aspartate aminotransferase levels, while the other had a grade 3 maculopapular rash. Five (14%) patients had a treatment-related serious adverse event (Steven-Johnson syndrome, hepatitis E infection, fever, liver abscesses, and ascites).

INTERPRETATION

Y90-radioembolisation followed by nivolumab resulted in an encouraging objective response rate in patients with advanced hepatocellular carcinoma, although the activity observed was not as high as the study was powered for. This strategy should be further evaluated in patients with Barcelona Clinic Liver Clinic (BCLC) stage B hepatocellular carcinoma that is ineligible or refractory to transarterial chemoembolisation and patients with BCLC C disease without extrahepatic spread.

FUNDING

National Medical Research Council Singapore, Bristol-Myers Squibb, Sirtex.

Repurposing Radiation Therapy for Immuno-oncology

Radiation therapy is traditionally used for the local control of tumour growth, but recent studies suggest that radiation therapy can have immunomodulatory properties that can be applied in combination therapy with immunotherapeutic agents. The paradigm of using radiation therapy for immunomodulation in cancer treatment is a rapidly progressing field, with multiple ongoing clinical trials exploring its use in combination with immune checkpoint blockades to induce an abscopal effect. Permutations of radiation therapy regimens, including variations in radiation dosing, radiation planning parameters and radiation modality, are being tested with varying degrees of success. The relative biological effectiveness was a concept introduced in the early days of radiation biology that allows the comparison of local tumour control across various radiation modalities and energies. Similarly, there remains a need for a new concept of comparing the immunological effectiveness of various radiation modalities. In this review, we will provide an overview of immunobiological models for preclinical and clinical monitoring of radiation therapy regimens and introduce the concept of relative immunological effectiveness to compare and screen for immune-activating functions of these regimens.

Radiotherapy Combined with PD-1 Inhibition Increases NK Cell Cytotoxicity towards Nasopharyngeal Carcinoma Cells

BACKGROUND

Nasopharyngeal carcinoma (NPC) in endemic regions and younger patients is characterized by a prominent lymphomononuclear infiltration. Radiation is the principal therapeutic modality for patients with NPC. Recent data suggest that the efficacy of radiotherapy in various cancers can be augmented when combined with immune checkpoint blockade. Here, we investigate the effect of radiotherapy on the killing of NPC cells by Natural Killer (NK) cells.

METHODS

NPC cell lines and a patient-derived xenograft were exposed to NK cells in the context of radiotherapy. Cytotoxicity was measured using the calcein-release assay. The contribution of the PD-L1/PD-1 checkpoint and signaling pathways to killing were analyzed using specific inhibitors.

RESULTS

Radiotherapy sensitized NPC cells to NK cell killing and upregulated expression of PD-1 ligand (PD-L1) in NPC cells and PD-1 receptor (PD-1) in NK cells. Blocking of the PD-L1/PD-1 checkpoint further increased the killing of NPC cells by NK cells in the context of radiotherapy.

CONCLUSION

Radiation boosts the killing of NPC cells by NK cells. Killing can be further augmented by blockade of the PD-L1/PD-1 checkpoint. The combination of radiotherapy with PD-L1/PD-1 checkpoint blockade could therefore increase the efficacy of radiotherapy in NPC tumors.

Combining Radiation with Immunotherapy: The University of Pennsylvania Experience

Immune checkpoint inhibitors have shown remarkable clinical benefit across a variety of cancer types. However, the majority of patients do not respond or develop relapse after therapy. Radiation can favorably modulate the immune system and enhance tumor antigen recognition and rejection. Thus, the combination of radiation and immune checkpoint blockade (ICB) has been recognized as a promising strategy to improve tumor response and broaden the clinical utility of immunotherapy. In this review, we highlight the preclinical and clinical experience at our institution aimed at understanding and promoting the immunostimulatory effect of radiation. We discuss the rationale, design, results, and lessons from our clinical trials in combining radiation with anti-CTLA4 and/or anti-PD-1 therapy. In parallel, our studies to understand the resistance mechanism to radiation and ICB have converged on interferon (IFN) signaling as a key regulatory pathway. Persistent IFN-γ signaling impairs anti-tumor immune responses which can be reversed by using JAK inhibitor to disrupt the IFN signaling. Lastly we discuss remaining challenges, ongoing studies, and future directions in combining radiation with immunotherapy.

Effects of Radiation on the Tumor Microenvironment

A malignant tumor consists of malignant cells as well as a wide array of normal host tissues including stroma, vasculature, and immune infiltrate. The interaction between cancer and these host tissues is critical as these host tissues play a variety of roles in supporting or resisting disease progression. Radiotherapy (RT) has direct effects on malignant cells, but, also, critically important effects on these other components of the tumor microenvironment (TME). Given the growing role of immune checkpoint inhibitors and other immunotherapy strategies, understanding how RT affects the TME, particularly the immune compartment, is essential to advance RT in this new era of cancer therapy. The interactions between RT and the TME are complex, affecting the innate and adaptive arms of the immune system. RT can induce both proinflammatory effects and immune suppressive effects that can either promote or impede antitumor immunity. It is likely that the initial proinflammatory effects of RT eventually lead to rebound immune-suppression as chronic inflammation sets in. The exact kinetics and nature of how RT changes the TME likely depends on timing, dose, fractionation, site irradiated, and tumor type. With increased understanding of the effects of RT on the TME, in the future it is likely that we will be able to personalize RT by varying the dose, site, and timing of intervention to generate the desired response to partner with immunotherapy strategies.

Parallels Between the Antiviral State and the Irradiated State

Improved understanding of host antiviral defense and antitumor immunity have elucidated molecular pathways important to both processes. During viral infection, RNA or DNA in the host cell serves as a danger signal that initiates the antiviral response. Recent studies have elucidated similarities in the signaling pathways activated by viruses and the signaling pathways induced by tumor DNA that is released into the cytoplasm of irradiated tumor cells. Both the host defense to viral infection and the sterile inflammation provoked by radiotherapy induce a type I interferon response that is necessary for pathogen control and immune-mediated tumor control, respectively. These findings have led to the hypothesis that radiotherapy employs a form of viral mimicry.