Kill and spread the word: stimulation of antitumor immune responses in the context of radiotherapy

MHC-I and PD-L1 Expression is Associated with Decreased Tumor Outgrowth and is Radiotherapy-inducible in the Murine Head and Neck Squamous Cell Carcinoma Model MOC1

INTRODUCTION

Combined radiotherapy and immune checkpoint inhibition is a potential treatment option for head and neck squamous cell carcinoma (HNSCC). Immunocompetent mouse models can help to successfully develop radio- immunotherapy combinations and to increase our understanding of the effects of radiotherapy on the tumor microenvironment for future clinical translation. Therefore, the aim of this study was to develop a homogeneous, reproducible HNSCC model originating from the Mouse Oral Cancer 1 (MOC1) HNSCC cell line, and to explore the radiotherapy-induced changes in its tumor microenvironment, using flow cytometry and PD-L1 microSPECT/CT imaging.

MATERIALS AND METHODS

In vivo growing tumors originating from the parental MOC1 line were used to generate single cell derived clones. These clones were screened in vitro for their ability to induce programmed cell death ligand 1 (PD-L1) and major histocompatibility complex class I (MHC-I) following IFNγ exposure. Clones with different IFNγ sensitivity were inoculated in C57BL/6 mice and assessed for tumor outgrowth. The composition of the tumor microenvironment of a stably growing (non)irradiated MOC1-derived clone was assessed by immunohistochemistry, flow cytometry and PD-L1 microSPECT/CT.

RESULTS

Low in vitro inducibility of MHC-I and PD-L1 by IFNγ was associated with increased tumor outgrowth of MOC1 clones in vivo. Flow cytometry analysis of cells derived from a stable in vivo growing MOC1 clone MOC1.3D5low showed expression of MHC-I and PD-L1 on several cell populations within the tumor. Upon irradiation, MHC-I and PD-L1 increased on leukocytes (CD45.2+) and cancer associated fibroblasts (CD45.2-/EpCAM-/CD90.1+). Furthermore, PD-L1 microSPECT/CT showed increased tumor uptake of radiolabeled PD-L1 antibodies with a heterogeneous spatial distribution of the radio signal, which co-localized with PD-L1+ and CD45.2+ areas.

DISCUSSION

PD-L1 and MHC-I inducibility by IFNγ in vitro is associated with tumor outgrowth of MOC1 clones in vivo. In tumors originating from a stably growing MOC1-derived clone, expression of these immune-related markers was induced by irradiation shown by flow cytometry on several cell populations within the tumor microenvironment such as immune cells and cancer associated fibroblasts. PD-L1 microSPECT/CT showed increased tumor uptake following radiotherapy, and autoradiography showed correlation of uptake with areas that are heavily infiltrated by immune cells. Knowledge of radiotherapy-induced effects on the tumor microenvironment in this model can help optimize timing and dosage for radio- immunotherapy combination strategies in future research.

DARES: A Phase II Trial of Durvalumab and Ablative Radiation in Extensive-Stage Small Cell Lung Cancer

BACKGROUND

Immunotherapy in combination with chemotherapy is first-line treatment for patients with extensive-stage small-cell lung cancer (ES-SCLC). Growing evidence suggests that radiation, specifically stereotactic body radiation therapy (SBRT), may enhance the immunogenic response as well as cytoreduce tumor burden. The primary objective of the study is to determine the progression free survival for patients with newly diagnosed ES-SCLC treated with combination multisite SBRT and chemo-immunotherapy (carboplatin, etoposide, and durvalumab).

METHODS

This is a multicenter, single arm, phase 2 study. Patients with treatment-naïve, ES-SCLC will be eligible for this study. Patients will receive durvalumab 1500mg IV q3w, carboplatin AUC 5 to 6 mg/mL q3w, and etoposide 80 to 100 mg/m2 on days 1 to 3 q3w for four cycles, followed by durvalumab 1500mg IV q4w until disease progression or unacceptable toxicity. Ablative radiation will be delivered 1 to 4 extracranial sites in 3 or 5 fractions, determined by location, during cycle 2. The primary endpoint is progression-free survival, measured from day 1 of chemoimmunotherapy. Secondary endpoints include grade ≥3 toxicity by CTCAE v5.0 within three months of RT, overall survival, response rate, time to second line systemic therapy, and time to new distant progression.

CONCLUSIONS

Now that immunotherapy is an established part of ES-SCLC management, it is important to further optimize its use and effect. This study will investigate the progression-free survival of combined SBRT and chemo-immunotherapy in patients with ES-SCLC. In addition, the data from this study may further inform the immunogenic role of SBRT with chemo-immunotherapy, as well as identify clinical, biological, or radiomic prognostic features.

Characterizing OXPHOS inhibitor-mediated alleviation of hypoxia using high-throughput live cell-imaging

BACKGROUND

Hypoxia is a common feature of many solid tumors and causes radiotherapy and immunotherapy resistance. Pharmacological inhibition of oxidative phosphorylation (OXPHOS) has emerged as a therapeutic strategy to reduce hypoxia. However, the OXPHOS inhibitors tested in clinical trials caused only moderate responses in hypoxia alleviation or trials were terminated due to dose-limiting toxicities. To improve the therapeutic benefit, FDA approved OXPHOS inhibitors (e.g. atovaquone) were conjugated to triphenylphosphonium (TPP+) to preferentially target cancer cell's mitochondria. In this study, we evaluated the hypoxia reducing effects of several mitochondria-targeted OXPHOS inhibitors and compared them to non-mitochondria-targeted OXPHOS inhibitors using newly developed spheroid models for diffusion-limited hypoxia.

METHODS

B16OVA murine melanoma cells and MC38 murine colon cancer cells expressing a HIF-Responsive Element (HRE)-induced Green Fluorescent Protein (GFP) with an oxygen-dependent degradation domain (HRE-eGFP-ODD) were generated to assess diffusion-limited hypoxia dynamics in spheroids. Spheroids were treated with IACS-010759, atovaquone, metformin, tamoxifen or with mitochondria-targeted atovaquone (Mito-ATO), PEGylated mitochondria-targeted atovaquone (Mito-PEG-ATO) or mitochondria-targeted tamoxifen (MitoTam). Hypoxia dynamics were followed and quantified over time using the IncuCyte Zoom Live Cell-Imaging system.

RESULTS

Hypoxic cores developed in B16OVA.HRE and MC38.HRE spheroids within 24 h hours after seeding. Treatment with IACS-010759, metformin, atovaquone, Mito-PEG-ATO and MitoTam showed a dose-dependent reduction of hypoxia in both B16OVA.HRE and MC38.HRE spheroids. Mito-ATO only alleviated hypoxia in MC38.HRE spheroids while tamoxifen was not able to reduce hypoxia in any of the spheroid models. The mitochondria-targeted OXPHOS inhibitors demonstrated stronger anti-hypoxic effects compared to the non-mito-targeted OXPHOS inhibitors.

CONCLUSIONS

We successfully developed a high-throughput spheroid model in which hypoxia dynamics can be quantified over time. Using this model, we showed that the mitochondria-targeted OXPHOS inhibitors Mito-ATO, Mito-PEG-ATO and MitoTam reduce hypoxia in tumor cells in a dose-dependent manner, potentially sensitizing hypoxic tumor cells for radiotherapy.

DNA as the main target in radiotherapy-a historical overview from first isolation to anti-tumour immune response

DNA damage is one of the foremost mechanisms of irradiation at the biological level. After the first isolation of DNA by Friedrich Miescher in the 19th century, the structure of DNA was described by Watson and Crick. Several Nobel Prizes have been awarded for DNA-related discoveries. This review aims to describe the historical perspective of DNA in radiation biology. Over the decades, DNA damage has been identified and quantified after irradiation. Depending on the type of sensing, different proteins are involved in sensing DNA damage and repairing the damage, if possible. For double-strand breaks, the main repair mechanisms are non-homologous end joining and homologous recombination. Additional mechanisms are the Fanconi anaemia pathway and base excision repair. Different methods have been developed for the detection of DNA double-strand breaks. Several drugs have been developed that interfere with different DNA repair mechanisms, e.g., PARP inhibitors. These drugs have been established in the standard treatment of different tumour entities and are being applied in several clinical trials in combination with radiotherapy. Over the past decades, it has become apparent that DNA damage mechanisms are also directly linked to the immune response in tumours. For example, cytosolic DNA fragments activate the innate immune system via the cGAS STING pathway.

Immune modulation during anti-cancer radio(immuno)therapy

Cancer can affect all human organs and tissues and ranks as a prominent cause of death as well as an obstruction to increasing life expectancy. A notable breakthrough in oncology has been the inclusion of the immune system in fighting cancer, potentially prolonging life and providing long-term benefits. The concept of "immunotherapy" has been discussed from the 19th and early 20th centuries by Wilhelm Busch, William B. Coley and Paul Ehrlich. This involves distinct approaches, including vaccines, non-specific cytokines and adoptive cell therapies. However, despite the advances made in recent years, questions on how to select the best therapeutic options or how to select the best combinations to improve clinical outcomes are still relevant for scientists and clinicians. More than half of cancer patients receive radiotherapy (RT) as part of their treatment. With the advances in RT and immunotherapy approaches, it is reasonable to consider how to enhance immunotherapy with radiation and vice versa, and to investigate whether combinations of these therapies would be beneficial. In this chapter, we will discuss how the immune system responds to cancer cells and different cancer therapies with a focus on combination of RT and immunotherapy (radioimmunotherapy, RIT).

Quantitative Imaging of Hypoxic CAIX-Positive Tumor Areas with Low Immune Cell Infiltration in Syngeneic Mouse Tumor Models

Limited diffusion of oxygen in combination with increased oxygen consumption leads to chronic hypoxia in most solid malignancies. This scarcity of oxygen is known to induce radioresistance and leads to an immunosuppressive microenvironment. Carbonic anhydrase IX (CAIX) is an enzyme functioning as a catalyzer for acid export in hypoxic cells and is an endogenous biomarker for chronic hypoxia. The aim of this study is to develop a radiolabeled antibody that recognizes murine CAIX to visualize chronic hypoxia in syngeneic tumor models and to study the immune cell population in these hypoxic areas. An anti-mCAIX antibody (MSC3) was conjugated to diethylenetriaminepentaacetic acid (DTPA) and radiolabeled with indium-111 (¹¹¹In). CAIX expression on murine tumor cells was determined using flow cytometry, and in vitro affinity of [¹¹¹In]In-MSC3 was analyzed in a competitive binding assay. Ex vivo biodistribution studies were performed to determine in vivo radiotracer distribution. CAIX⁺ tumor fractions were determined by mCAIX microSPECT/CT, and the tumor microenvironment was analyzed using immunohistochemistry and autoradiography. We showed that [¹¹¹In]In-MSC3 binds to CAIX-expressing (CAIX⁺) murine cells in vitro and accumulates in CAIX⁺ areas in vivo. We optimized the use of [¹¹¹In]In-MSC3 for preclinical imaging such that it can be applied in syngeneic mouse models and showed that we can quantitatively distinguish between tumor models with varying CAIX⁺ fractions by ex vivo analyses and in vivo mCAIX microSPECT/CT. Analysis of the tumor microenvironment identified these CAIX⁺ areas as less infiltrated by immune cells. Together these data demonstrate that mCAIX microSPECT/CT is a sensitive technique to visualize hypoxic CAIX⁺ tumor areas that exhibit reduced infiltration of immune cells in syngeneic mouse models. In the future, this technique may enable visualization of CAIX expression before or during hypoxia-targeted or hypoxia-reducing treatments. Thereby, it will help optimize immuno- and radiotherapy efficacy in translationally relevant syngeneic mouse tumor models.

CAR-T Cells in the Treatment of Ovarian Cancer: A Promising Cell Therapy

Ovarian cancer (OC) is among the most common gynecologic malignancies with a poor prognosis and a high mortality rate. Most patients are diagnosed at an advanced stage (stage III or IV), with 5-year survival rates ranging from 25% to 47% worldwide. Surgical resection and first-line chemotherapy are the main treatment modalities for OC. However, patients usually relapse within a few years of initial treatment due to resistance to chemotherapy. Cell-based therapies, particularly adoptive T-cell therapy and chimeric antigen receptor T (CAR-T) cell therapy, represent an alternative immunotherapy approach with great potential for hematologic malignancies. However, the use of CAR-T-cell therapy for the treatment of OC is still associated with several difficulties. In this review, we comprehensively discuss recent innovations in CAR-T-cell engineering to improve clinical efficacy, as well as strategies to overcome the limitations of CAR-T-cell therapy in OC.

CAR-T cell combination therapy: the next revolution in cancer treatment

In recent decades, the advent of immune-based therapies, most notably Chimeric antigen receptor (CAR)-T cell therapy has revolutionized cancer treatment. The promising results of numerous studies indicate that CAR-T cell therapy has had a remarkable ability and successful performance in treating blood cancers. However, the heterogeneity and immunosuppressive tumor microenvironment (TME) of solid tumors have challenged the effectiveness of these anti-tumor fighters by creating various barriers. Despite the promising results of this therapeutic approach, including tumor degradation and patient improvement, there are some concerns about the efficacy and safety of the widespread use of this treatment in the clinic. Complex and suppressing tumor microenvironment, tumor antigen heterogeneity, the difficulty of cell trafficking, CAR-T cell exhaustion, and reduced cytotoxicity in the tumor site limit the applicability of CAR-T cell therapy and highlights the requiring to improve the performance of this treatment. With this in mind, in the last decade, many efforts have been made to use other treatments for cancer in combination with tuberculosis to increase the effectiveness of CAR-T cell therapy, especially in solid tumors. The combination therapy results have promising consequences for tumor regression and better cancer control compared to single therapies. Therefore, this study aimed to comprehensively discuss different cancer treatment methods in combination with CAR-T cell therapy and their therapeutic outcomes, which can be a helpful perspective for improving cancer treatment in the near future.

The implications from the interplay of neoadjuvant chemoradiotherapy and the immune microenvironment in rectal cancer

Neoadjuvant chemoradiotherapy (nCRT) is recommended for the treatment of locally advanced rectal cancer. Even though the combination of nCRT and immune checkpoint inhibitors (ICIs) has received much attention, the specific combination modes and dose fractions in radiotherapy (RT) are still indistinct. This review focuses on the immunological mechanism involved in nCRT, the clinical efficacy, the immunological effect of different combined strategies, concurrent or sequential nCRT plus ICIs, long-course RT and short-course RT. This review discusses the impact of nCRT on tumor immunity and summarizes the availability of different dose fractions in RT and distinct combined strategies, aiming at providing clues for optimal neoadjuvant therapy options that maximize efficacy and minimize side effects.

Overcoming Immune Resistance With Radiation Therapy in Prostate Cancer

Prostate cancer is the second most common cancer in men and represents a significant healthcare burden worldwide. Therapeutic options in the metastatic castration-resistant setting remain limited, despite advances in androgen deprivation therapy, precision medicine and targeted therapies. In this review, we summarize the role of immunotherapy in prostate cancer and offer perspectives on opportunities for future development, based on current knowledge of the immunosuppressive tumor microenvironment. Furthermore, we discuss the potential for synergistic therapeutic strategies with modern radiotherapy, through modulation of the tumor microenvironment. Emerging clinical and pre-clinical data suggest that radiation can convert immune desert tumors into an inflamed immunological hub, potentially sensitive to immunotherapy.

Unconventional radiotherapy to enhance immunotherapy efficacy in bulky tumors: a case report

Determining the most appropriate management strategy for patients with large tumor masses is a very challenging issue. Unconventional radiotherapy modalities, such as spatially fractionated radiation therapy (SFRT), are associated with dramatic responses. Recent studies have suggested that systemic immune activation may be triggered by SFRT delivery to primary tumor lesion. This report describes the case of a patient treated with a novel form of immune-sparing partially ablative irradiation (ISPART) for a bulky peritoneal metastasis from renal cell cancer, refractory to anti-PD-1 therapy (nivolumab) as third-line therapy after sequential therapy with sunitinib and cabozantinib. The observed response suggests that there may be a synergistic effect between ISPART and immunotherapy. This case report supports the inclusion of ISPART in patients presenting with bulky lesions treated with checkpoint inhibitors .

Head and neck tumor cells treated with hypofractionated irradiation die via apoptosis and are better taken up by M1-like macrophages

Purpose

The incidence of head and neck squamous cell carcinomas (HNSCC) is increasing worldwide, especially when triggered by the human papilloma virus (HPV). Radiotherapy has immune-modulatory properties, but the role of macrophages present in HNSCC and having contact with irradiated tumor cells remains unclear. The influence of irradiated (2 × 5Gy) HNSCC cells on the (re-)polarization and phagocytosis of human macrophages, either non-polarized or with a more M1 or M2 phenotype, was therefore investigated.

Methods

Human monocytes were differentiated with the hematopoietic growth factors M‑CSF (m) or GM-CSF (g) and additionally pre-polarized with either interleukin (IL)-4 and IL-10 or interferon (IFN)-γ and lipopolysaccharides (LPS), respectively. Subsequently, they were added to previously irradiated (2 × 5Gy) and mock-treated HPV-positive (UD-SCC-2) and HPV-negative (Cal33) HNSCC cells including their supernatants.

Results

The HNSCC cells treated with hypofractionated irradiation died via apoptosis and were strongly phagocytosed by M0m and M2 macrophages. M0g and M1 macrophages phagocytosed the tumor cells to a lesser extent. Irradiated HNSCC cells were better phagocytosed by M1 macrophages compared to mock-treated controls. The polarization status of the macrophages was not significantly changed, except for the expression of CD206 on M2 macrophages, which was reduced after phagocytosis of irradiated HPV-negative cells. Further, a significant increase in the uptake of irradiated HPV-positive cells by M0g macrophages when compared to HPV-negative cells was observed.

Conclusion

HNSCC cells treated with hypofractionated irradiation foster phagocytosis by anti-tumorigenic M1 macrophages. The data provide the first evidence on the impact of the HPV status of HNSCC cells on the modulation of the macrophage response to irradiated tumor cells.

Novel Radiation Therapy Paradigms and Immunomodulation: Heresies and Hope

Radiation therapy benefits the majority of patients across the spectrum of cancer types. However, both local and distant tumor recurrences limit its clinical success. While departing from the established tenet of fractionation in clinical radiotherapy, ablative-intensity hypofractionated radiotherapy, especially stereotactic radiosurgery and stereotactic ablative radiotherapy, has emerged as an alternative paradigm achieving unprecedented rates of local tumor control. Direct tumor cell killing has been assumed to be the primary therapeutic mode of action of such ablative radiation. But with increasing recognition that tumor responses also depend on the immunostimulatory or immunosuppressive status of the tumor microenvironment, the immunologic effect of ablative radiotherapy is emerging as a key contributor to antitumor response. More recently, novel radiation modalities, such as spatially fractionated radiotherapy and ultrahigh dose rate FLASH irradiation, that venture even further from conventional paradigms have shown promise of increasing the therapeutic index of radiation therapy with the potential of immunomodulation. Here, we review the immunomodulatory impact of novel radiation therapy paradigms, heretofore considered radiobiological heresies, a deeper understanding of which is imperative to realizing fully their potential for more curative cancer therapy.

Advances in immune therapies for the treatment of microsatellite instability‑high/deficient mismatch repair metastatic colorectal cancer (Review)

Microsatellite instability-high/deficient mismatch repair colorectal cancer (MSI-H/dMMR CRC) is a molecular subtype characterized by high-frequency mutations within DNA mismatch repair genes. Defects in the DNA mismatch repair machinery lead to subsequent frame-shift mutations, resulting in the generation of frame-shift peptides that serve as neoantigens. This has translated into exquisite sensitivity to immune checkpoint inhibitors (ICIs) and a significant clinical benefit from immune therapies in this patient population. The present article provides a comprehensive review of the advances in the field of immune therapies for MSI-H/dMMR metastatic CRC, with a focus on the major randomized clinical trials that led to Food and Drug Administration approval of specific ICIs for this population, a detailed review of the molecular background responsible for tumor response, as well as the mechanisms of resistance to ICI therapy. Finally, ongoing investigations of other immunotherapeutic strategies to address and overcome the challenges that currently limit response and long-term response to ICIs were presented.

Targeted Alpha-Particle Radiotherapy and Immune Checkpoint Inhibitors Induces Cooperative Inhibition on Tumor Growth of Malignant Melanoma

Simple Summary

Radiation therapy and immune checkpoint inhibitors (ICIs) have been demonstrated to cooperatively activate adaptive anti-tumor immunity with curative potential in preclinical models of melanoma. Receptor-targeted radionuclide therapy can be systemically injected to selectively deliver ionizing radiation to tumor sites throughout the body, potentially rendering all tumor sites more susceptible to anti-tumor immune response. In this study, we demonstrated the feasibility of delivering alpha-particle radiation to murine melanoma tumors using a ²¹²Pb radiolabeled peptide [²¹²Pb]VMT01 that targets the melanocortin 1 receptor (MC1R). Our data showed anti-tumor cooperation between [²¹²Pb]VMT01 and ICIs in melanoma, mediated by induction of tumor-specific immunity. The immunogenicity of [²¹²Pb]VMT01 in melanoma was also evidenced by enhanced tumor infiltrating lymphocytes and tumor vaccination assays.

Abstract

Radiotherapy can facilitate the immune recognition of immunologically “cold” tumors and enhance the efficacy of anti-PD-1 and anti-CTLA-4 immune checkpoint inhibitors (ICIs) in melanoma. Systemic administration of receptor-targeted radionuclide therapy has the potential to selectively deliver radionuclides to multiple tumors throughout the body in metastatic settings. By triggering immunologic cell death and increasing the immune susceptibility of surviving tumor cells in these locations, targeted radionuclide therapies may overcome resistance to ICIs and render immunologically “cold” tumors throughout the body responsive to ICIs and immunologically “hot”. Here, we show the anti-tumor cooperation of targeted α-particle radionuclide therapy (α-TRT) and ICIs in preclinical models of melanoma. Melanocortin 1 receptor (MC1R)-targeted radiopeptide [²¹²Pb]VMT01 was employed to deliver α-radiation to melanoma tumors in mice. A single injection of 4.1 MBq [²¹²Pb]VMT01 significantly slowed the tumor growth of B16-F10 melanoma and the combination of [²¹²Pb]VMT01 and ICIs induced a cooperative anti-tumor effect leading to 43% complete tumor response with no sign of malignancy on autopsy. Animals with complete response developed anti-tumor immunity to reject further tumor inoculations. This therapeutic cooperation was completely abolished in RAG1 KO mice, which are deficient in T-cell maturation. In addition, the anti-tumor cooperation was compromised when fractionated [²¹²Pb]VMT01 was used in the combination. We also demonstrated that [²¹²Pb]VMT01 induced immunogenic cell death in tumor vaccination assays and in vitro exposure to [²¹²Pb]VMT01 sensitized immunotolerant melanoma to ICIs treatment in vivo. Enhanced tumor infiltrating CD3⁺, CD4⁺, CD8⁺ lymphocytes were observed following injection of 1.4 MBq [²¹²Pb]VMT01. Overall, we demonstrated anti-tumor cooperation between α-TRT and ICIs in melanoma that is mediated by tumor specific immunity.

Prognostic Impact of Sarcopenia and Radiotherapy in Patients With Advanced Gastric Cancer Treated With Anti-PD-1 Antibody

Background

We explored the combined effects of sarcopenia (SAR) and radiotherapy (RT) on outcomes in patients with advanced gastric cancer (AGC) treated with immune-checkpoint blockade (ICB).

Methods

Among 185 patients with AGC treated with ICB, we defined SAR as skeletal muscle index <49 cm2/m2 for men and <31 cm2/m2 for women; 93 patients met criteria. We defined high neutrophil-to-lymphocyte ratio (hNLR) as NLR≥3. Palliative RT was performed in 37 patients (20%) before ICB.

Results

We frequently observed hNLR in patients with SAR (53% vs. 35%, p = 0.02). The median overall survival (OS) for the entire cohort was 5 months. Stratification by risk factors of SAR or hNLR revealed a significant difference in median OS (0 [N = 60] vs. 1 [N = 76] vs. 2 [N = 49]: 7.6 vs. 6.4 vs. 2.2 months, p < 0.001). Patients with microsatellite instability-high (MSI-H, N = 19) or Epstein-Barr virus (EBV)-positive tumors (N = 13) showed favorable outcomes compared to those with microsatellite stable (MSS, N = 142) tumors (median OS, not reached vs. 16.8 vs. 3.8 months, respectively). The benefit of RT was evident in patients with both SAR and hNLR (median OS, 3.1 vs. 1.3 months, p = 0.02) and MSS/EBV-negative tumor (median OS, 6.5 vs. 3.5 months, p = 0.03), but outcomes after RT in MSI-H tumor were not significantly different. In multivariable analysis, SAR/hNLR, molecular subtypes, and a history of RT were associated with OS (all p < 0.05).

Conclusions

We demonstrated the negative predictive value of SAR/hNLR on outcomes after ICB for AGC, and the history of RT could overcome the negative impact of SAR/hNLR and the MSS/EBV-negative subtype.

Circulating immune cell populations related to primary breast cancer, surgical removal, and radiotherapy revealed by flow cytometry analysis

BACKGROUND

Advanced breast cancer (BC) impact immune cells in the blood but whether such effects may reflect the presence of early BC and its therapeutic management remains elusive.

METHODS

To address this question, we used multiparametric flow cytometry to analyze circulating leukocytes in patients with early BC (n = 13) at the time of diagnosis, after surgery, and after adjuvant radiotherapy, compared to healthy individuals. Data were analyzed using a minimally supervised approach based on FlowSOM algorithm and validated manually.

RESULTS

At the time of diagnosis, BC patients have an increased frequency of CD117⁺CD11b⁺ granulocytes, which was significantly reduced after tumor removal. Adjuvant radiotherapy increased the frequency of CD45RO⁺ memory CD4⁺ T cells and CD4⁺ regulatory T cells. FlowSOM algorithm analysis revealed several unanticipated populations, including cells negative for all markers tested, CD11b⁺CD15^low, CD3⁺CD4^-CD8^-, CD3⁺CD4⁺CD8⁺, and CD3⁺CD8⁺CD127⁺CD45RO⁺ cells, associated with BC or radiotherapy.

CONCLUSIONS

This study revealed changes in blood leukocytes associated with primary BC, surgical removal, and adjuvant radiotherapy. Specifically, it identified increased levels of CD117⁺ granulocytes, memory, and regulatory CD4⁺ T cells as potential biomarkers of BC and radiotherapy, respectively. Importantly, the study demonstrates the value of unsupervised analysis of complex flow cytometry data to unravel new cell populations of potential clinical relevance.

Radiotherapy and the immune system: More than just immune suppression

Radiotherapy (RT) is still one of the standard cancer therapies, with up to two third of all cancer patients with solid tumors being irradiated in the course of their disease. The aim of using ionizing radiation in fractionated treatment schedules was always to achieve local tumor control by inducing DNA damage which can be repaired by surrounding normal tissue but leads to cell death in tumor cells. Meanwhile, it is known that RT also has immunological effects reshaping the tumor microenvironment. Nevertheless, RT alone often fails to elicit potent antitumor immune responses as these effects can be immunostimulatory as well as immunosuppressive. Here, we discuss how immunotherapies can be exploited in combined therapies to boost RT-induced antitumor immune responses or to counteract preexisting and RT-mediated immunosuppression to improve local and systemic tumor control. Furthermore, we highlight some parameters of radioimmunotherapies (RITs) which are under investigation for potential optimizations and how RIT approaches are tested in first phases II and III trials. Finally, we discuss how RT might affect normal and cancer stem cells.

Targeting Oxidative Phosphorylation to Increase the Efficacy of Radio- and Immune-Combination Therapy

As tumors grow, they upregulate glycolytic and oxidative metabolism to support their increased and altered energetic demands. These metabolic changes have major effects on the tumor microenvironment. One of the properties leading to this aberrant metabolism is hypoxia, which occurs when tumors outgrow their often-chaotic vasculature. This scarcity of oxygen is known to induce radioresistance but can also have a disrupting effect on the antitumor immune response. Hypoxia inhibits immune effector cell function, while immune cells with a more suppressing phenotype become more active. Therefore, hypoxia strongly affects the efficacy of both radiotherapy and immunotherapy, as well as this therapy combination. Inhibition of oxidative phosphorylation (OXPHOS) is gaining interest for its ability to combat tumor hypoxia, and there are strong indications that this results in a reactivation of the immune response. This strategy decreases oxygen consumption, leading to better oxygenation of hypoxic tumor areas and eventually an increase in immunogenic cell death induced by radio-immunotherapy combinations. Promising preclinical improvements in radio- and immunotherapy efficacy have been observed by the hypoxia-reducing effect of OXPHOS inhibitors and several compounds are currently in clinical trials for their anticancer properties. Here, we will review the pharmacologic attenuation of tumor hypoxia using OXPHOS inhibitors, with emphasis on their impact on the intrinsic antitumor immune response and how this affects the efficacy of (combined) radio- and immunotherapy.

Impacts of combining anti-PD-L1 immunotherapy and radiotherapy on the tumour immune microenvironment in a murine prostate cancer model

BACKGROUND

Radiotherapy enhances innate and adaptive anti-tumour immunity. It is unclear whether this effect may be harnessed by combining immunotherapy with radiotherapy fractions used to treat prostate cancer. We investigated tumour immune microenvironment responses of pre-clinical prostate cancer models to radiotherapy. Having defined this landscape, we tested whether radiotherapy-induced tumour growth delay could be enhanced with anti-PD-L1.

METHODS

Hypofractionated radiotherapy was delivered to TRAMP-C1 and MyC-CaP flank allografts. Tumour growth delay, tumour immune microenvironment flow-cytometry, and immune gene expression were analysed. TRAMP-C1 allografts were then treated with 3 × 5 Gy ± anti-PD-L1.

RESULTS

3 × 5 Gy caused tumour growth delay in TRAMP-C1 and MyC-CaP. Tumour immune microenvironment changes in TRAMP-C1 at 7 days post-radiotherapy included increased tumour-associated macrophages and dendritic cells and upregulation of PD-1/PD-L1, CD8+ T-cell, dendritic cell, and regulatory T-cell genes. At tumour regrowth post-3 × 5 Gy the tumour immune microenvironment flow-cytometry was similar to control tumours, however CD8+, natural killer and dendritic cell gene transcripts were reduced. PD-L1 inhibition plus 3 × 5 Gy in TRAMP-C1 did not enhance tumour growth delay versus monotherapy.

CONCLUSION

3 × 5 Gy hypofractionated radiotherapy can result in tumour growth delay and immune cell changes in allograft prostate cancer models. Adjuncts beyond immunomodulation may be necessary to improve the radiotherapy-induced anti-tumour response.

Assessing the interactions between radiotherapy and antitumour immunity

Immunotherapy, specifically the introduction of immune checkpoint inhibitors, has transformed the treatment of cancer, enabling long-term tumour control even in individuals with advanced-stage disease. Unfortunately, only a small subset of patients show a response to currently available immunotherapies. Despite a growing consensus that combining immune checkpoint inhibitors with radiotherapy can increase response rates, this approach might be limited by the development of persistent radiation-induced immunosuppression. The ultimate goal of combining immunotherapy with radiotherapy is to induce a shift from an ineffective, pre-existing immune response to a long-lasting, therapy-induced immune response at all sites of disease. To achieve this goal and enable the adaptation and monitoring of individualized treatment approaches, assessment of the dynamic changes in the immune system at the patient level is essential. In this Review, we summarize the available clinical data, including forthcoming methods to assess the immune response to radiotherapy at the patient level, ranging from serum biomarkers to imaging techniques that enable investigation of immune cell dynamics in patients. Furthermore, we discuss modelling approaches that have been developed to predict the interaction of immunotherapy with radiotherapy, and highlight how they could be combined with biomarkers of antitumour immunity to optimize radiotherapy regimens and maximize their synergy with immunotherapy.

Immunotherapy for Colorectal Cancer: A Review of Current and Novel Therapeutic Approaches

Colorectal cancer (CRC) remains a leading cause of cancer-related deaths in the United States. Although immunotherapy has dramatically changed the landscape of treatment for many advanced cancers, the benefit in CRC has thus far been limited to patients with microsatellite instability high (MSI-H):DNA mismatch repair-deficient (dMMR) tumors. Recent studies in the refractory CRC setting have led to US Food and Drug Administration approvals for pembrolizumab as well as nivolumab (with or without ipilimumab) for tumors harboring an MSI-H:dMMR molecular profile. Several randomized controlled trials are underway to move immunotherapy into the frontline for metastatic cancer (with or without chemotherapy) and the adjuvant setting. Awareness of these studies is critical given the relatively low incidence (approximately 3%-5%) of MSI-H:dMMR in advanced or metastatic CRC to support study completion, because the results could be potentially practice changing. The real challenge in this disease is related to demonstrating the benefit of immunotherapy for the vast majority of patients with CRC not harboring MSI-H:dMMR. Given the rapid pace of scientific changes, this article provides a narrative review regarding the current landscape of immunotherapy for CRC. Particular attention is paid to the currently available data that inform today's clinical practice along with upcoming randomized controlled trials that may soon dramatically change the treatment landscape for CRC.

National Cancer Institute (NCI) state of the science: Targeted radiosensitizers in colorectal cancer

Colorectal cancer (CRC) represents a major public health problem as the second leading cause of cancer-related mortality in the United States. Of an estimated 140,000 newly diagnosed CRC cases in 2018, roughly one-third of these patients will have a primary tumor located in the distal large bowel or rectum. The current standard-of-care approach includes curative-intent surgery, often after preoperative (neoadjuvant) radiotherapy (RT), to increase rates of tumor down-staging, clinical and pathologic response, as well as improving surgical resection quality. However, despite advancements in surgical techniques, as well as sharpened precision of dosimetry offered by contemporary RT delivery platforms, the oncology community continues to face challenges related to disease relapse. Ongoing investigations are aimed at testing novel radiosensitizing agents and treatments that might exploit the systemic antitumor effects of RT using immunotherapies. If successful, these treatments may usher in a new curative paradigm for rectal cancers, such that surgical interventions may be avoided. Importantly, this disease offers an opportunity to correlate matched paired biopsies, radiographic response, and molecular mechanisms of treatment sensitivity and resistance with clinical outcomes. Herein, the authors highlight the available evidence from preclinical models and early-phase studies, with an emphasis on promising developmental therapeutics undergoing prospective validation in larger scale clinical trials. This review by the National Cancer Institute's Radiation Research Program Colorectal Cancer Working Group provides an updated, comprehensive examination of the continuously evolving state of the science regarding radiosensitizer drug development in the curative treatment of CRC.

Metformin as a Radiation Modifier; Implications to Normal Tissue Protection and Tumor Sensitization

BACKGROUND

Nowadays, ionizing radiation is used for several applications in medicine, industry, agriculture, and nuclear power generation. Besides the beneficial roles of ionizing radiation, there are some concerns about accidental exposure to radioactive sources. The threat posed by its use in terrorism is of global concern. Furthermore, there are several side effects to normal organs for patients who had undergone radiation treatment for cancer. Hence, the modulation of radiation response in normal tissues was one of the most important aims of radiobiology. Although, so far, several agents have been investigated for protection and mitigation of radiation injury. Agents such as amifostine may lead to severe toxicity, while others may interfere with radiation therapy outcomes as a result of tumor protection. Metformin is a natural agent that is well known as an antidiabetic drug. It has shown some antioxidant effects and enhances DNA repair capacity, thereby ameliorating cell death following exposure to radiation. Moreover, through targeting endogenous ROS production within cells, it can mitigate radiation injury. This could potentially make it an effective radiation countermeasure. In contrast to other radioprotectors, metformin has shown modulatory effects through induction of several genes such as AMPK, which suppresses reduction/ oxidation (redox) reactions, protects cells from accumulation of unrepaired DNA, and attenuates initiation of inflammation as well as fibrotic pathways. Interestingly, these properties of metformin can sensitize cancer cells to radiotherapy.

CONCLUSION

In this article, we aimed to review the interesting properties of metformin such as radioprotection, radiomitigation and radiosensitization, which could make it an interesting adjuvant for clinical radiotherapy, as well as an interesting candidate for mitigation of radiation injury after a radiation disaster.

Modulation of radiation sensitivity and antitumor immunity by viral pathogenic factors: Implications for radio-immunotherapy

Several DNA viruses including Human Papillomavirus (HPV), Epstein-Barr virus (EBV), and Human cytomegalovirus (HCMV) are mechanistically associated with the development of human cancers (HPV, EBV) and/or modulation of the immune system (HCMV). Moreover, a number of distinct mechanisms have been described regarding the modulation of tumor cell response to ionizing radiation and evasion from the host immune system by viral factors. There is further accumulating interest in the treatment with immune-modulatory therapies such as immune checkpoint inhibitors for malignancies with a viral etiology. Also, patients with HPV-positive tumors have a significantly improved prognosis that is attributable to increased intrinsic radiation sensitivity and may also arise from modulation of a cytotoxic T cell response in the tumor microenvironment (TME). In this review, we will highlight recent advances in the understanding of the biological basis of radiation response mediated by viral pathogenic factors and evasion from and modulation of the immune system by viruses.

Radiotherapy and immune response: the systemic effects of a local treatment

Technological developments have allowed improvements in radiotherapy delivery, with higher precision and better sparing of normal tissue. For many years, it has been well known that ionizing radiation has not only local action but also systemic effects by triggering many molecular signaling pathways. There is still a lack of knowledge of this issue. This review focuses on the current literature about the effects of ionizing radiation on the immune system, either suppressing or stimulating the host reactions against the tumor, and the factors that interact with these responses, such as the radiation dose and dose / fraction effects in the tumor microenvironment and vasculature. In addition, some implications of these effects in cancer treatment, mainly in combined strategies, are addressed from the perspective of their interactions with the more advanced technology currently available, such as heavy ion therapy and nanotechnology.

Combination therapy: A feasibility strategy for CAR-T cell therapy in the treatment of solid tumors

Chimeric antigen receptor (CAR) T-cell therapies have been demonstrated to have durable and potentially curative therapeutic efficacies in patients with hematological malignancies. Currently, multiple clinical trials in CAR-T cell therapy have been evaluated for the treatment of patients with solid malignancies, but have had less marked therapeutic effects when the agents are used as monotherapies. When summarizing relevant studies, the present study found that combination therapy strategies for solid tumors based on CAR-T cell therapies might be more effective. This review will focus on various aspects of treating solid tumors with CAR-T cell therapy: i) The therapeutic efficacy of CAR-T cell monotherapy, ii) the feasibility of the CAR-T cell therapy in conjunction with chemotherapy, iii) the feasibility of CAR-T cell therapy with radiotherapy, iv) the feasibility of CAR-T cell therapy with chemoradiotherapy, and v) the feasibility of the combination of CAR-T cell therapy with other strategies.

Abscopal, immunological effects of radiotherapy: Narrowing the gap between clinical and preclinical experiences

Radiotherapy-despite being a local therapy that meanwhile is characterized by an impressively high degree of spatial accuracy-can stimulate systemic phenomena which occasionally lead to regression and rejection of non-irradiated, distant tumor lesions. These abscopal effects of local irradiation have been observed in sporadic clinical case reports since the beginning of the 20th century, and extensive preclinical work has contributed to identify systemic anti-tumor immune responses as the underlying driving forces. Although abscopal tumor regression still remains a rare event in the radiotherapeutic routine, increasing numbers of cases are being reported, particularly since the clinical implementation of immune checkpoint inhibiting agents. Accordingly, interests to systematically exploit the therapeutic potential of radiotherapy-stimulated systemic responses are constantly growing. The present review briefly delineates the history of radiotherapy-induced abscopal effects and the activation of systemic anti-tumor immune responses by local irradiation. We discuss preclinical and clinical reports with specific focus on the corresponding controversies, and we propose issues that should be addressed in the future in order to narrow the gap between preclinical knowledge and clinical experiences.

The Evolution of Radiation Therapy in Metastatic Breast Cancer: From Local Therapy to Systemic Agent

Radiation therapy is a mainstay of treatment in early and locally advanced breast cancer but is typically reserved for palliation of symptomatic lesions in patients with metastatic breast cancer. With new advances in the field of tumor biology and immunology, the role of radiation in the metastatic setting is evolving to harness its immune-enhancing properties. Through the release of tumor antigens, tumor DNA, and cytokines into the tumor microenvironment, radiation augments the antitumoral immune response to affect both the targeted lesion and distant sites of metastatic disease. The use of immunotherapeutics to promote antitumoral immunity has resulted in improved treatment responses in patients with metastatic disease and the combination of radiation therapy and immunotherapy has become an area of intense investigation. In this article, we will review the emerging role of radiation in the treatment of metastatic disease and discuss the current state of the science and clinical trials investigating the combination of radiation and immunotherapy.

Abscopal effects of radiotherapy and combined mRNA-based immunotherapy in a syngeneic, OVA-expressing thymoma mouse model

BACKGROUND

Tumor metastasis and immune evasion present major challenges of cancer treatment. Radiotherapy can overcome immunosuppressive tumor microenvironments. Anecdotal reports suggest abscopal anti-tumor immune responses. This study assesses abscopal effects of radiotherapy in combination with mRNA-based cancer vaccination (RNActive®).

METHODS

C57BL/6 mice were injected with ovalbumin-expressing thymoma cells into the right hind leg (primary tumor) and left flank (secondary tumor) with a delay of 4 days. Primary tumors were irradiated with 3 × 2 Gy, while secondary tumors were shielded. RNA and combined treatment groups received mRNA-based RNActive® vaccination.

RESULTS

Radiotherapy and combined radioimmunotherapy significantly delayed primary tumor growth with a tumor control in 15 and 53% of mice, respectively. In small secondary tumors, radioimmunotherapy significantly slowed growth rate compared to vaccination (p = 0.002) and control groups (p = 0.01). Cytokine microarray analysis of secondary tumors showed changes in the cytokine microenvironment, even in the non-irradiated contralateral tumors after combination treatment.

CONCLUSION

Combined irradiation and immunotherapy is able to induce abscopal responses, even with low, normofractionated radiation doses. Thus, the combination of mRNA-based vaccination with irradiation might be an effective regimen to induce systemic anti-tumor immunity.

Immune modulatory effects of radiotherapy as basis for well-reasoned radioimmunotherapies

BACKGROUND

Radiotherapy (RT) has been known for decades as a local treatment modality for malign and benign disease. In order to efficiently exploit the therapeutic potential of RT, an understanding of the immune modulatory properties of ionizing radiation is mandatory. These should be used for improvement of radioimmunotherapies for cancer in particular.

METHODS

We here summarize the latest research and review articles about immune modulatory properties of RT, with focus on radiation dose and on combination of RT with selected immunotherapies. Based on the knowledge of the manifold immune mechanisms that are triggered by RT, thought-provoking impulse for multimodal radioimmunotherapies is provided.

RESULTS

It has become obvious that ionizing radiation induces various forms of cell death and associated processes via DNA damage initiation and triggering of cellular stress responses. Immunogenic cell death (ICD) is of special interest since it activates the immune system via release of danger signals and via direct activation of immune cells. While RT with higher single doses in particular induces ICD, RT with a lower dose is mainly responsible for immune cell recruitment and for attenuation of an existing inflammation. The counteracting immunosuppression emanating from tumor cells can be overcome by combining RT with selected immunotherapies such as immune checkpoint inhibition, TGF-β inhibitors, and boosting of immunity with vaccination.

CONCLUSION

In order to exploit the full power of RT and thereby develop efficient radioimmunotherapies, the dose per fraction used in RT protocols, the fractionation, the quality, and the quantity of certain immunotherapies need to be qualitatively and chronologically well-matched to the individual immune status of the patient.

Abscopal effect of radiation on bone metastases of breast cancer: A case report

The abscopal effect is defined as the clearance of distant tumors after applying localized irradiation to a particular tumor site. It has been proposed that a mechanism for the abscopal effect might be the activation of the immune system, which leads to immunogenic tumor cell death. Here, we describe a woman with advanced breast cancer that received modified ablative radiation therapy that targeted her primary breast tumor. She experienced an apparent regression of metastatic mass in the thoracic spine. This case supported the hypothesis that the abscopal effect might be attributable to an activation of the systemic immune response.

Dynamics of Heat Shock Protein 70 Serum Levels As a Predictor of Clinical Response in Non-Small-Cell Lung Cancer and Correlation with the Hypoxia-Related Marker Osteopontin

Hypoxia mediates resistance to radio(chemo)therapy (RT) by stimulating the synthesis of hypoxia-related genes, such as osteopontin (OPN) and stress proteins, including the major stress-inducible heat shock protein 70 (Hsp70). Apart from its intracellular localization, Hsp70 is also present on the plasma membrane of viable tumor cells that actively release it in lipid vesicles with biophysical characteristics of exosomes. Exosomal Hsp70 contributes to radioresistance while Hsp70 derived from dying tumor cells can serve as a stimulator of immune cells. Given these opposing traits of extracellular Hsp70 and the unsatisfactory outcome of locally advanced lung tumors, we investigated the role of Hsp70 in the plasma of patients with advanced, non-metastasized non-small-cell lung cancer (NSCLC) before (T1) and 4–6 weeks after RT (T2) in relation to OPN as potential biomarkers for clinical response. Plasma levels of Hsp70 correlate with those of OPN at T1, and high OPN levels are significantly associated with a decreased overall survival (OS). Due to a therapy-induced reduction in viable tumor mass after RT Hsp70 plasma levels dropped significantly at T2 (p = 0.016). However, with respect to the immunostimulatory capacity of Hsp70 derived from dying tumor cells, patients with higher post-therapeutic Hsp70 levels showed a significantly better response to RT (p = 0.034) than those with lower levels at T2. In summary, high OPN plasma levels at T1 are indicative for poor OS, whereas elevated post-therapeutic Hsp70 plasma levels together with a drop of Hsp70 between T1 and T2, successfully predict favorable responses to RT. Monitoring the dynamics of Hsp70 in NSCLC patients before and after RT can provide additional predictive information for clinical outcome and therefore might allow a more rapid therapy adaptation.

Anti-inflammatory Mechanisms Triggered by Apoptotic Cells during Their Clearance

In the human body, billions of cells die by apoptosis every day. The subsequent clearance of apoptotic cells by phagocytosis is normally efficient enough to prevent secondary necrosis and the consequent release of cell contents that would induce inflammation and trigger autoimmunity. In addition, apoptotic cells generally induce an anti-inflammatory response, thus removal of apoptotic cells is usually immunologically silent. Since the first discovery that uptake of apoptotic cells leads to transforming growth factor (TGF)-β and interleukin (IL)-10 release by engulfing macrophages, numerous anti-inflammatory mechanisms triggered by apoptotic cells have been discovered, including release of anti-inflammatory molecules from the apoptotic cells, triggering immediate anti-inflammatory signaling pathways by apoptotic cell surface molecules via phagocyte receptors, activating phagocyte nuclear receptors following uptake and inducing the production of anti-inflammatory soluble mediators by phagocytes that may act via paracrine or autocrine mechanisms to amplify and preserve the anti-inflammatory state. Here, we summarize our present knowledge about how these anti-inflammatory mechanisms operate during the clearance of apoptotic cells.

Chemoradiation Increases PD-L1 Expression in Certain Melanoma and Glioblastoma Cells

Immunotherapy approaches currently make their way into the clinics to improve the outcome of standard radiochemotherapy (RCT). The programed cell death receptor ligand 1 (PD-L1) is one possible target that, upon blockade, allows T cell-dependent antitumor immune responses to be executed. To date, it is unclear which RCT protocol and which fractionation scheme leads to increased PD-L1 expression and thereby renders blockade of this immune suppressive pathway reasonable. We therefore investigated the impact of radiotherapy (RT), chemotherapy (CT), and RCT on PD-L1 surface expression on tumor cells of tumor entities with differing somatic mutation prevalence. Murine melanoma (B16-F10), glioblastoma (GL261-luc2), and colorectal (CT26) tumor cells were treated with dacarbazine, temozolomide, and a combination of irinotecan, oxaliplatin, and fluorouracil, respectively. Additionally, they were irradiated with a single dose [10 Gray (Gy)] or hypo-fractionated (2 × 5 Gy), respectively, norm-fractionated (5 × 2 Gy) radiation protocols were used. PD-L1 surface and intracellular interferon (IFN)-gamma expression was measured by flow cytometry, and IL-6 release was determined by ELISA. Furthermore, tumor cell death was monitored by AnnexinV-FITC/7-AAD staining. For first in vivo analyses, the B16-F10 mouse melanoma model was chosen. In B16-F10 and GL261-luc2 cells, particularly norm-fractionated and hypo-fractionated radiation led to a significant increase of surface PD-L1, which could not be observed in CT26 cells. Furthermore, PD-L1 expression is more pronounced on vital tumor cells and goes along with increased levels of IFN-gamma in the tumor cells. In melanoma cells CT was the main trigger for IL-6 release, while in glioblastoma cells it was norm-fractionated RT. In vivo, fractionated RT only in combination with dacarbazine induced PD-L1 expression on melanoma cells. Our results suggest a tumor cell-mediated upregulation of PD-L1 expression following in particular chemoradiation that is not only dependent on the somatic mutation prevalence of the tumor entity.

Checkpoint inhibitors and radiation treatment in Hodgkin's lymphoma : New study concepts of the German Hodgkin Study Group

BACKGROUND

Patients with classical Hodgkin's lymphoma (cHL) have a good prognosis even in advanced stages. However, combined chemo- and radiotherapy, as the standard of care, is also associated with treatment-related toxicities such as organ damage, secondary neoplasias, infertility, or fatigue and long-term fatigue. Many patients suffer from this burden although their cHL was cured. Therefore, the efficacy of immune checkpoint inhibitors like anti-PD1/PD-L1 antibodies in the treatment of solid cancers and also in HL offers new options. A remarkable and durable response rate with a favorable toxicity profile was observed in heavily pretreated cHL patients.

METHODS

Planning to perform prospective randomized clinical trials in the content of radio-immune treatment in patients with Hodgkin's lymphoma (HL), we transferred the results of preliminary clinical studies and basic research in clinical relevant study concepts.

RESULTS

Based on these promising early phase trial data, the German Hodgkin Study Group (GHSG) will investigate innovative treatment regimens in upcoming phase II trials.

CONCLUSION

The therapeutic efficacy and potential synergies of anti-PD1 antibodies in combination with chemo- or radiotherapy will be investigated in various settings of HL.

Enhanced binding of necrosis-targeting immunocytokine NHS-IL12 after local tumour irradiation in murine xenograft models

PURPOSE

NHS-IL12 is an immunocytokine targeting necrotic tumour areas. IL12 shows anti-tumour activity. As local irradiation might induce additional necrosis in solid tumours, we aimed to evaluate the increase in intratumoural accumulation of NHS-IL12 after irradiation and correlate the findings with diffusion-weighted MRI studies in two xenograft models.

METHODS

Human rhabdomyosarcoma (A204) and prostate cancer (PC3) cells were studied in vitro and as subcutaneous xenografts. Radiation sensitivity of the cell lines was assessed in vitro by colony formation assays. In vivo tumour necrosis was assessed based on apparent diffusion coefficients (ADC). Biodistribution of NHS-IL12 was evaluated with and without tumour irradiation using in vivo small-animal PET and ex vivo biodistribution.

RESULTS

A204 and PC3 differed in their intrinsic radiation sensitivity. Accordingly, radiation-induced tumour necrosis was found only in A204 xenografts. In comparison with control, ADC was significantly increased after irradiation of A204 tumours with 1 × 8.0 Gy and 5 × 2.0 Gy, whereas no change in ADC was observed in PC3 xenografts in all irradiation regimes. ADC correlated with histology. An enhanced uptake of radiolabelled NHS-IL12 in A204 tumours was detected by PET and ex vivo biodistribution after tumour irradiation. In PC3 tumours, no increase in NHS-IL12 uptake was observed.

CONCLUSIONS

In dependence of the tumour model, tumour irradiation enhanced tumour necrosis measured in MRI and histology. In vivo PET and ex vivo biodistribution showed enhanced binding of NHS-IL12 in rhabdomyosarcoma xenografts. Thus, enhanced binding of necrosis-targeting immunocytokines might be a novel mechanism of additive effects in combination with irradiation.

Immune-modulating properties of ionizing radiation: rationale for the treatment of cancer by combination radiotherapy and immune checkpoint inhibitors

Radiotherapy (RT) utilizes the DNA-damaging properties of ionizing radiation to control tumor growth and ultimately kill tumor cells. By modifying the tumor cell phenotype and the tumor microenvironment, it may also modulate the immune system. However, out-of-field reactions of RT mostly assume further immune activation. Here, the sequence of the applications of RT and immunotherapy is crucial, just as the dose and fractionation may be. Lower single doses may impact on tumor vascularization and immune cell infiltration in particular, while higher doses may impact on intratumoral induction and production of type I interferons. The induction of immunogenic cancer cell death seems in turn to be a common mechanism for most RT schemes. Dendritic cells (DCs) are activated by the released danger signals and by taking up tumor peptides derived from irradiated cells. DCs subsequently activate T cells, a process that has to be tightly controlled to ensure tolerance. Inhibitory pathways known as immune checkpoints exist for this purpose and are exploited by tumors to inhibit immune responses. Cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed cell death protein 1 (PD-1) on T cells are two major checkpoints. The biological concepts behind the findings that RT in combination with anti-CTLA-4 and/or anti-PD-L1 blockade stimulates CD8+ T cell-mediated anti-tumor immunity are reviewed in detail. On this basis, we suggest clinically significant combinations and sequences of RT and immune checkpoint inhibition. We conclude that RT and immune therapies complement one another.

Modern Radiotherapy Concepts and the Impact of Radiation on Immune Activation

Even though there is extensive research carried out in radiation oncology, most of the clinical studies focus on the effects of radiation on the local tumor tissue and deal with normal tissue side effects. The influence of dose fractionation and timing particularly with regard to immune activation is not satisfactorily investigated so far. This review, therefore, summarizes current knowledge on concepts of modern radiotherapy (RT) and evaluates the potential of RT for immune activation. Focus is set on radiation-induced forms of tumor cell death and consecutively the immunogenicity of the tumor cells. The so-called non-targeted, abscopal effects can contribute to anti-tumor responses in a specific and systemic manner and possess the ability to target relapsing tumor cells as well as metastases. The impact of distinct RT concepts on immune activation is outlined and pre-clinical evidence and clinical observations on RT-induced immunity will be discussed. Knowledge on the radiosensitivity of immune cells as well as clinical evidence for enhanced immunity after RT will be considered. While stereotactic ablative body radiotherapy seem to have a beneficial outcome over classical RT fractionation in pre-clinical animal models, in vitro model systems suggest an advantage for classical fractionated RT for immune activation. Furthermore, the optimal approach may differ based on the tumor site and/or genetic signature. These facts highlight that clinical trials are urgently needed to identify whether high-dose RT is superior to induce anti-tumor immune responses compared to classical fractionated RT and in particular how the outcome is when RT is combined with immunotherapy in selected tumor entities.

The dual role of NK cells in antitumor reactions triggered by ionizing radiation in combination with hyperthermia

Classical tumor therapy consists of surgery, radio(RT)- and/or chemotherapy. Additive immunotherapy has gained in impact and antitumor in situ immunization strategies are promising to strengthen innate and adaptive immune responses. Immunological effects of RT and especially in combination with immune stimulation are mostly described for melanoma. Since hyperthermia (HT) in multimodal settings is capable of rendering tumor cells immunogenic, we analyzed the in vivo immunogenic potential of RT plus HT-treated B16 melanoma cells with an immunization and therapeutic assay. We focused on the role of natural killer (NK) cells in the triggered antitumor reactions. In vitro experiments showed that RT plus HT-treated B16 melanoma cells died via apoptosis and necrosis and released especially the danger signal HMGB1. The in vivo analyses revealed that melanoma cells are rendered immunogenic by RT plus HT. Especially, the repetitive immunization with treated melanoma cells led to an increase in NK cell number in draining lymph nodes, particularly of the immune regulatory CD27⁺CD11b⁻ NK cell subpopulation. While permanent NK cell depletion after immunization led to a significant acceleration of tumor outgrowth, a single NK cell depletion two days before immunization resulted in significant tumor growth retardation. The therapeutic model, a local in situ immunization closely resembling the clinical situation when solid tumors are exposed locally to RT plus HT, confirmed these effects. We conclude that a dual and time-dependent impact of NK cells on the efficacy of antitumor immune reactions induced by immunogenic tumor cells generated with RT plus HT exists.

Immunomodulation of classical and non-classical HLA molecules by ionizing radiation

Radiotherapy has been employed for the treatment of oncological patients for nearly a century, and together with surgery and chemotherapy, radiation oncology constitutes one of the three pillars of cancer therapy. Ionizing radiation has complex effects on neoplastic cells and on tumor microenvironment: beyond its action as a direct cytotoxic agent, tumor irradiation triggers a series of alterations in tumoral cells, which includes the de novo synthesis of particular proteins and the up/down-regulation of cell surface molecules. Additionally, ionizing radiation may induce the release of "danger signals" which may, in turn lead to cellular and molecular responses by the immune system. This immunomodulatory action of ionizing radiation highlights the importance of the combined use (radiotherapy plus immunotherapy) for cancer healing. Major histocompatibility complex antigens (also called Human Leukocyte Antigens, HLA in humans) are one of those molecules whose expression is modulated after irradiation. This review summarizes the modulatory properties of ionizing radiation on the expression of HLA class I (classical and non-classical) and class II molecules, with special emphasis in non-classical HLA-I molecules.

Adenosine can thwart antitumor immune responses elicited by radiotherapy : Therapeutic strategies alleviating protumor ADO activities

BACKGROUND

By studying the bioenergetic status we could show that the development of tumor hypoxia is accompanied, apart from myriad other biologically relevant effects, by a substantial accumulation of adenosine (ADO). ADO has been shown to act as a strong immunosuppressive agent in tumors by modulating the innate and adaptive immune system. In contrast to ADO, standard radiotherapy (RT) can either stimulate or abrogate antitumor immune responses. Herein, we present ADO-mediated mechanisms that may thwart antitumor immune responses elicited by RT.

MATERIALS AND METHODS

An overview of the generation, accumulation, and ADO-related multifaceted inhibition of immune functions, contrasted with the antitumor immune effects of RT, is provided.

RESULTS

Upon hypoxic stress, cancer cells release ATP into the extracellular space where nucleotides are converted into ADO by hypoxia-sensitive, membrane-bound ectoenzymes (CD39/CD73). ADO actions are mediated upon binding to surface receptors, mainly A2A receptors on tumor and immune cells. Receptor activation leads to a broad spectrum of strong immunosuppressive properties facilitating tumor escape from immune control. Mechanisms include (1) impaired activity of CD4 (+) T and CD8 (+) T, NK cells and dendritic cells (DC), decreased production of immuno-stimulatory lymphokines, and (2) activation of Treg cells, expansion of MDSCs, promotion of M2 macrophages, and increased activity of major immunosuppressive cytokines. In addition, ADO can directly stimulate tumor proliferation and angiogenesis.

CONCLUSION

ADO mechanisms described can thwart antitumor immune responses elicited by RT. Therapeutic strategies alleviating tumor-promoting activities of ADO include respiratory hyperoxia or mild hyperthermia, inhibition of CD39/CD73 ectoenzymes or blockade of A2A receptors, and inhibition of ATP-release channels or ADO transporters.

Key mechanisms involved in ionizing radiation-induced systemic effects. A current review

Organisms respond to physical, chemical and biological threats by a potent inflammatory response, aimed at preserving tissue integrity and restoring tissue homeostasis and function. Systemic effects in an organism refer to an effect or phenomenon which originates at a specific point and can spread throughout the body affecting a group of organs or tissues. Ionizing radiation (IR)-induced systemic effects arise usually from a local exposure of an organ or part of the body. This stress induces a variety of responses in the irradiated cells/tissues, initiated by the DNA damage response and DNA repair (DDR/R), apoptosis or immune response, including inflammation. Activation of this IR-response (IRR) system, especially at the organism level, consists of several subsystems and exerts a variety of targeted and non-targeted effects. Based on the above, we believe that in order to understand this complex response system better one should follow a 'holistic' approach including all possible mechanisms and at all organization levels. In this review, we describe the current status of knowledge on the topic, as well as the key molecules and main mechanisms involved in the 'spreading' of the message throughout the body or cells. Last but not least, we discuss the danger-signal mediated systemic immune effects of radiotherapy for the clinical setup.

Comparative analysis of the effects of radiotherapy versus radiotherapy after adjuvant chemotherapy on the composition of lymphocyte subpopulations in breast cancer patients

BACKGROUND

Breast cancer is the most common cancer in women worldwide and surgery, radiotherapy (RT) and chemotherapy (ChT) are frequently used to treat this cancer. Adjuvant RT has been shown to cause long-term changes in lymphocyte counts in the peripheral blood. Herein, the time course of changes in lymphocyte subpopulations upon RT was studied in patients with and without adjuvant ChT in order to explore its potential clinical impact.

MATERIALS AND METHODS

Total lymphocyte counts and the composition of lymphocyte subpopulations before RT (t0), after 30 Gy (t1), at the end of RT (t2), and 6 weeks (t3), 6 months (t4), and 1 year (t5) after RT were studied by flow cytometry.

RESULTS

Absolute lymphocyte counts were significantly lower in all breast cancer patients (n=40) before and also 1 year after RT compared to healthy controls. The percentage of CD3(+)/CD4(+) helper T cells and FoxP3(+) regulatory T cells increased significantly in patients without adjuvant ChT. Different NK cell subpopulations dropped during RT in patients with and without ChT, but recovered to initial levels 6months after RT (t4). During RT (t0-t2) the percentage of CD19(+) B cells significantly dropped in patients without ChT, but gradually increased in patients with adjuvant ChT. Both patient groups reached initial levels 6 months after RT (t4).

CONCLUSION

Different lymphocyte subpopulations respond differently to RT with and without adjuvant ChT. CD4(+) T cells increase during RT, whereas NK cells and B cells decrease in patients without ChT, but recover within 6 months after RT. Treg cells gradually increase in patients without ChT from t0 to t5, but not in patients with adjuvant ChT.