Intraoperative radiation therapy induces immune response activity after pancreatic surgery.

BACKGROUND: Pancreatic cancer has highly aggressive features, such as local recurrence that leads to significantly high morbidity and mortality and recurrence after successful tumour resection. Intraoperative radiation therapy (IORT), which delivers targeted radiation to a tumour bed, is known to reduce local recurrence by directly killing tumour cells and modifying the tumour microenvironment. METHODS: Among 30 patients diagnosed with pancreatic cancer, 17 patients received IORT immediately after surgical resection. We investigated changes in the immune response induced by IORT by analysing the peritoneal fluid (PF) and blood of patients with and without IORT treatment after pancreatic cancer surgery. Further, we treated three pancreatic cell lines with PF to observe proliferation and activity changes. RESULTS: Levels of cytokines involved in the PI3K/SMAD pathway were increased in the PF of IORT-treated patients. Moreover, IORT-treated PF inhibited the growth, migration, and invasiveness of pancreatic cancer cells. Changes in lymphocyte populations in the blood of IORT-treated patients indicated an increased immune response. CONCLUSIONS: Based on the characterisation and quantification of immune cells in the blood and cytokine levels in the PF, we conclude that IORT induced an anti-tumour effect by activating the immune response, which may prevent pancreatic cancer recurrence. CLINICAL TRIAL REGISTRATION: NCT03273374 .

Impact of proton therapy on antitumor immune response.

Radiotherapy delivered using photons induces an immune response that leads to modulation of the tumor microenvironment. Clinical studies are ongoing to evaluate immune checkpoint inhibitors in association with photon radiotherapy. At present, there is no publication on the radio-induced immune response after proton therapy. Balb/c mice bearing subcutaneous CT26 colon tumors were irradiated by a single fraction of 16.4 Gy using a proton beam extracted from a TR24 cyclotron. RNA sequencing analysis was assessed at 3 days post-treatment. Proton therapy immune response was monitored by flow cytometry using several panels (lymphoid, myeloid cells, lymphoid cytokines) at 7 and 14 days post-irradiation. RNA-Seq functional profiling identified a large number of GO categories linked to "immune response" and "interferon signaling". Immunomonitoring evaluation showed induced tumor infiltration by immune cells. This is the first study showing the effect of proton therapy on immune response. These interesting results provide a sound basis to assess the efficacy of a combination of proton therapy and immune checkpoint inhibitors.

Expression Level of Membrane Markers CD5, CD19, and CD20 in B Cells after UV-Irradiation and Incubation in the Presence of Autologous Plasma.

The effect of UV-light (240-390 nm) in doses of 151 and 755 J/m2 on the expression of membrane markers CD5, CD19, CD20 in human peripheral blood B cells was studied by flow cytometry. In 24 h after exposure to UV light, we observed activation of processes accompanied by structural rearrangements of B-cell membranes leading to changes in the expression of receptor molecules: the content of of CD19 and CD20 increased due to activation of the synthesis of these proteins, while the content of CD5 decreased. The percentage of CD5+ cells decreased over 24 h after UV-irradiation of lymphocytes, while addition of autologous plasma to the incubation medium produced a photoprotective effect on CD5+ cells.

Assessment of some factors of cellular and humoral immunity in radiology workers.

Radiation workers in medical diagnostic departments are occupationally exposed to long-term low-dose ionizing radiation, which may cause radiation-induced side effects. This study investigated subtypes of peripheral blood lymphocytes and immunoglobulin levels in workers who were occupationally exposed to X-ray radiation at the Department of Radiology. Seventeen radiology workers received low levels of ionizing radiation as the study group and 18 individuals who were not exposed to radiation were included as the control group. The percentage of lymphocyte subtypes (CD4+, CD8+ and CD4+/CD8+) and serum levels of immunoglobulins (IgA, IgG and IgM) were measured using peripheral blood samples. Considering all lymphocyte subtypes and serum levels of IgA, IgG and IgM, there was no significant difference between the study and control groups (P > 0.05). There were no significant differences in all mentioned parameters regarding gender (P > 0.05). For the length of employment period, there was a significant difference concerning CD4+/CD8+ (P < 0.05). The findings showed that exposure to low levels of ionizing radiation does not affect the immune system of workers in diagnostic radiology dose level. Because of relatively small samples of workers, it is suggested that these factors be investigated on larger samples of radiology workers.

Radiotherapy-exposed CD8+ and CD4+ neoantigens enhance tumor control.

Neoantigens generated by somatic nonsynonymous mutations are key targets of tumor-specific T cells, but only a small number of mutations predicted to be immunogenic are presented by MHC molecules on cancer cells. Vaccination studies in mice and patients have shown that the majority of neoepitopes that elicit T cell responses fail to induce significant antitumor activity, for incompletely understood reasons. We report that radiotherapy upregulates the expression of genes containing immunogenic mutations in a poorly immunogenic mouse model of triple-negative breast cancer. Vaccination with neoepitopes encoded by these genes elicited CD8+ and CD4+ T cells that, whereas ineffective in preventing tumor growth, improved the therapeutic efficacy of radiotherapy. Mechanistically, neoantigen-specific CD8+ T cells preferentially killed irradiated tumor cells. Neoantigen-specific CD4+ T cells were required for the therapeutic efficacy of vaccination and acted by producing Th1 cytokines, killing irradiated tumor cells, and promoting epitope spread. Such a cytotoxic activity relied on the ability of radiation to upregulate class II MHC molecules as well as the death receptors FAS/CD95 and DR5 on the surface of tumor cells. These results provide proof-of-principle evidence that radiotherapy works in concert with neoantigen vaccination to improve tumor control.

Cytotoxicity of zinc oxide nanoparticles to innate and adaptive human immune cells.

Zinc oxide nanoparticles (ZnO-NPs) are widely used in almost every area of life. Therefore, exposure to them is unavoidable, which makes it necessary to assess their safety for humans. This paper aims to determine toxicity of ZnO-NPs of two diameters toward human immune cells responsible for: innate response (U-937 and HL-60) and acquired response (COLO-720L and HUT-78). Mitochondrial activity, membrane integrity, degree of cellular lipid oxidation, induction of inflammation, and activation of the apoptosis pathway were evaluated to determine differences in cellular response to the tested nanoparticles. ZnO-NPs with a diameter of 100 and 130 nm cause significant cell mortality at 25 and 12 mg/L, respectively. Mitochondrial damage leads to the activation of the caspase cascade and, consequently, to cell apoptosis. ZnO-NPs also cause peroxidation of membrane lipids. Due to the photocatalytic properties of ZnO-NPs, the effect of ultraviolet (UV) irradiation on the degree of their toxicity was also investigated. However, UV irradiation enhances the toxic effect of nanoparticles mainly by weakening the cell's defense capabilities. ZnO-NPs are cytotoxic to human immune system, and they may cause both long-term and short-term negative effects.

Dose Fractionation During Puberty Is More Detrimental to Mammary Gland Development Than an Equivalent Acute Dose of Radiation Exposure.

PURPOSE: Computed tomographic (CT) scans in adolescents have increased dramatically in recent years. However, the effects of cumulative low-dose exposures on the development of radiation sensitive organs, such as the mammary gland, is unknown. The purpose of this work was to define the effects of dose rate on mammary organ formation during puberty, an especially sensitive window in mammary development. We used a fractionated low-dose x-ray exposure to mimic multiple higher dose CT scans, and we hypothesized that fractionated exposure would have less of an effect on the number of mammary gland defects compared with an acute exposure. METHODS AND MATERIALS: Female mice were subjected to fractionated low-dose x-ray exposure (10 cGy/d for 5 days), acute x-ray exposure (1 × 50 cGy), or sham exposure. As the wide genetic diversity in humans can play a role in a person's response to irradiation, 2 genetically diverse mouse strains differing in radiation sensitivity (BALB/c-sensitive; C57BL/6-resistant) were used to investigate the role of genetic background on the magnitude of the effect. RESULTS: Unexpectedly, our data reveal that multiple low-dose exposures produce greater immune and mammary defects for weeks after exposure compared with controls. The most pronounced defects being increased ductal branching in both strains and a greater percentage of terminal end buds in the BALB/c strain of mice exposed to fractionated radiation compared with sham. Radiation-induced defects near the terminal end bud were also increased in both strains. CONCLUSIONS: The findings suggest that fractionated low-dose exposures are potentially more damaging to organ development compared with an equivalent, single acute exposure and that genetic background is an important parameter modifying the severity of these effects.

Immunomodulatory Effects of Radiotherapy.

Radiation therapy (RT), an integral component of curative treatment for many malignancies, can be administered via an increasing array of techniques. In this review, we summarize the properties and application of different types of RT, specifically, conventional therapy with x-rays, stereotactic body RT, and proton and carbon particle therapies. We highlight how low-linear energy transfer (LET) radiation induces simple DNA lesions that are efficiently repaired by cells, whereas high-LET radiation causes complex DNA lesions that are difficult to repair and that ultimately enhance cancer cell killing. Additionally, we discuss the immunogenicity of radiation-induced tumor death, elucidate the molecular mechanisms by which radiation mounts innate and adaptive immune responses and explore strategies by which we can increase the efficacy of these mechanisms. Understanding the mechanisms by which RT modulates immune signaling and the key players involved in modulating the RT-mediated immune response will help to improve therapeutic efficacy and to identify novel immunomodulatory drugs that will benefit cancer patients undergoing targeted RT.

[Biologic effects of high doses per fraction]. / Effets biologiques des hautes doses par fraction.

The radiobiological concepts described for conventional doses per fraction (1.8 to 2Gy) seem difficult to translate to high doses per fraction radiobiology. In fact, specific mechanisms are involved during high dose per fraction irradiation, involving vascular microenvironment damage and anti tumor immune response. The "5R's" of "classical" radiobiology (factors influencing the response of healthy or cancer cells to irradiation) seem to play a less important role in case of high doses per fraction. In addition, applicability of the linear quadratic model in this context is debated. It is therefore difficult to obtain reliable equivalent doses, hence the importance of including our patients in clinical trials, especially in case of concomitant systemic treatments. In addition to stereotactic radiotherapy, flash irradiations defined by a dose rate approximately 2000 times faster than "conventional" irradiation can also deliver high doses per fraction, with a much better tolerance for normal tissue without loss of anti tumor efficacy. Finally, availability of robust prospective data is a prerequisite to answer the question of short and long-term risk/benefit ratio of these different irradiation techniques.

A Genomic Profile of Local Immunity in the Melanoma Microenvironment Following Treatment with α Particle-Emitting Ultrasmall Silica Nanoparticles.

An α particle-emitting nanodrug that is a potent and specific antitumor agent and also prompts significant remodeling of local immunity in the tumor microenvironment (TME) has been developed and may impact the treatment of melanoma. Biocompatible ultrasmall fluorescent core-shell silica nanoparticles (C' dots, diameter ∼6.0 nm) have been engineered to target the melanocortin-1 receptor expressed on melanoma through α melanocyte-stimulating hormone peptides attached to the C' dot surface. Actinium-225 is also bound to the nanoparticle to deliver a densely ionizing dose of high-energy α particles to cancer. Nanodrug pharmacokinetic properties are optimal for targeted radionuclide therapy as they exhibit rapid blood clearance, tumor-specific accumulation, minimal off-target localization, and renal elimination. Potent and specific tumor control, arising from the α particles, was observed in a syngeneic animal model of melanoma. Surprisingly, the C' dot component of this drug initiates a favorable pseudopathogenic response in the TME generating distinct changes in the fractions of naive and activated CD8 T cells, Th1 and regulatory T cells, immature dendritic cells, monocytes, MΦ and M1 macrophages, and activated natural killer cells. Concomitant upregulation of the inflammatory cytokine genome and adaptive immune pathways each describes a macrophage-initiated pseudoresponse to a viral-shaped pathogen. This study suggests that therapeutic α-particle irradiation of melanoma using ultrasmall functionalized core-shell silica nanoparticles potently kills tumor cells, and at the same time initiates a distinct immune response in the TME.

The Influence of Adjuvant Radiotherapy and Single Nucleotide Polymorphisms on Circulating Immune Response Cell Numbers and Phenotypes of Patients With Breast Cancer.

BACKGROUND/AIM: Adjuvant radiotherapy (RT) damages multiple layers of skin, muscle, blood vessels and blood cells that are included within the RT area. Indirect, bystander systemic effects could also develop in cells not directly hit by radiation. MATERIALS AND METHODS: Ninety-three female patients recovering from breast cancer surgery and 82 female healthy blood donors were analyzed. For identification of systemic adaptive and innate immune response, rapid and low-cost blood-based biomarkers were assayed. RESULTS: Post-operated breast cancer patients had a decreased number of circulating adaptive immune response cells but increased number of circulating immunosuppressive myeloid subpopulations. RT decreased the number of T-cells and platelets without influencing the number of immunosuppressive myeloid subpopulations. Alterations in the number and phenotypes of T-cell subpopulations were associated with SNPs. CONCLUSION: The combination of RT and immunotherapy might provide optimal treatment for cancer patients.

Effective Radiotherapy in Tumor Assisted by Ganoderma lucidum Polysaccharide-Conjugated Bismuth Sulfide Nanoparticles through Radiosensitization and Dendritic Cell Activation.

Radiotherapy is a traditional method for cancer therapy but may become ineffective likely due to the radiation-induced immunosuppression. Instead of simply increasing the radiation dose, reactivation of immunosuppression in the tumor microenvironment is an alternative strategy for successful cancer treatment. In this work, we synthesized bismuth sulfide nanoparticles (BiNP) and conjugated with immunoactive Ganoderma lucidum polysaccharide (GLP). GLP-BiNP were able to increase the sensitivity of radiotherapy, attributing to the efficient X-ray absorption of bismuth element. BiNP alone can mildly activate dendritic cells (DC) in vitro, while GLP-BiNP further enhanced the level of DC maturation, shown as the increase in phenotypic maturation markers, cytokine release, acid phosphatase activity, and T cell proliferation in DC/T cell co-culture. Compared to BiNP, GLP-BiNP altered the tissue distribution with faster accumulation in the tumor. Meanwhile, mature DC greatly increased in both tumor and spleen by GLP-BiNP within 24 h. GLP-BiNP combination with radiation achieved remarkable inhibition of tumor growth through apoptosis. Alternatively, lung metastasis was largely prohibited by GLP-BiNP, shown as a reduced amount of tumor nodules and cancer cell invasion by pathological findings. Mechanistically, GLP-BiNP altered the tumor immunosuppression microenvironment by preferably increasing the number of intratumor CD8+ T cell proliferation, as well as the improved immunobalance shown as the increased serum interferon-γ/interleukin-4 ratio. Specifically, GLP conjugation seemed to protect the kidney from injury occasionally introduced by bare BiNP. As a result, GLP-BiNP play a dual role in tumor treatment through radiosensitization and immunoactivities.

Radiotherapy, Lymphopenia, and Host Immune Capacity in Glioblastoma: A Potentially Actionable Toxicity Associated With Reduced Efficacy of Radiotherapy.

Radiotherapy is cytotoxic to tumor cells and is therefore a critical component of therapy for many malignancies, including glioblastoma (GBM). We now appreciate the value of the immunomodulatory effects of radiation that may be important to overall therapeutic success in some patients with this primary brain tumor. Although potentially beneficial immune-stimulating properties of radiotherapy treatment have been the focus of recent study, this modality is actually at the same time associated with the depletion of lymphocytes, which are crucial to the defense against neoplastic development and progression. In this review, we describe the association of systemic lymphopenia with poor tumor outcome, present evidence that radiotherapy is an important contributing cause of lymphodepletion, describe the systemic immune context of tumor and brain injury that contributes to immunosuppression, describe other contributing factors to lymphopenia including concomitant medications and treatments, and speculate about the role of the normal physiologic response to brain injury in the immunosuppressive dynamics of GBM. Radiotherapy is one significant and potentially actionable iatrogenic suppressor of immune response that may be limiting the success of therapy in GBM and other tumor types. Altered strategies for radiotherapy more permissive of a vigorous antineoplastic immune response may improve outcome for malignancy.

Impact of Radiation Dose to the Host Immune System on Tumor Control and Survival for Stage III Non-Small Cell Lung Cancer Treated with Definitive Radiation Therapy.

PURPOSE: The significance of radiation dose to the host immune system during the treatment of stage III non-small cell lung cancer (NSCLC) is unknown, but higher doses were associated with worse tumor control and overall survival (OS) in a secondary analysis of RTOG 0617. In this study, we sought to assess the impact of the estimated dose of radiation to immune cells (EDRIC) on cancer-specific outcomes in an independent cohort of patients treated at our institution. METHODS AND MATERIALS: We retrospectively identified 117 patients with stage III NSCLC treated with definitive fractionated radiation from 2004 to 2017 at a single academic center (median dose of 60 Gy; 60% underwent intensity modulated radiation therapy and 92% received concurrent platinum-based chemotherapy). EDRIC was calculated as a function of the number of radiation fractions and mean doses to the lung, heart, and remaining body based on a model developed by Jin et al. RESULTS: Median follow-up was 16 months with 77% of patients followed until death. In the entire population, 5-year OS was 11.2% with a median survival of 17.3 months. Median EDRIC for the entire cohort was 6.1 Gy (range, 2.5-10.0 Gy). A higher EDRIC was correlated with greater risk of grade ≥3 lymphopenia (P = .004). On multivariate analysis including total prescription radiation dose, planning target volume, and chemotherapy utilization, EDRIC was independently associated with OS (hazard ratio [HR] 1.17, P = .03), local progression-free survival (HR 1.17, P = .02), and disease-free survival (HR 1.15, P = .04). The median OS for patients with an EDRIC above 7.3 Gy (fourth quartile) and below 5.1 Gy (first quartile) was 14.3 and 28.2 months, respectively. CONCLUSIONS: Higher doses of radiation to the immune system were associated with tumor progression and death after the definitive treatment of stage III NSCLC. Tailoring radiation therapy to spare the immune system may be an important future direction to improve outcomes in this population.

Non-myeloablative busulfan chimeric mouse models are less pro-inflammatory than head-shielded irradiation for studying immune cell interactions in brain tumours.

BACKGROUND: Chimeric mouse models generated via adoptive bone marrow transfer are the foundation for immune cell tracking in neuroinflammation. Chimeras that exhibit low chimerism levels, blood-brain barrier disruption and pro-inflammatory effects prior to the progression of the pathological phenotype, make it difficult to distinguish the role of immune cells in neuroinflammatory conditions. Head-shielded irradiation overcomes many of the issues described and replaces the recipient bone marrow system with donor haematopoietic cells expressing a reporter gene or different pan-leukocyte antigen, whilst leaving the blood-brain barrier intact. However, our previous work with full body irradiation suggests that this may generate a pro-inflammatory peripheral environment which could impact on the brain's immune microenvironment. Our aim was to compare non-myeloablative busulfan conditioning against head-shielded irradiation bone marrow chimeras prior to implantation of glioblastoma, a malignant brain tumour with a pro-inflammatory phenotype. METHODS: Recipient wild-type/CD45.1 mice received non-myeloablative busulfan conditioning (25 mg/kg), full intensity head-shielded irradiation, full intensity busulfan conditioning (125 mg/kg) prior to transplant with whole bone marrow from CD45.2 donors and were compared against untransplanted controls. Half the mice from each group were orthotopically implanted with syngeneic GL-261 glioblastoma cells. We assessed peripheral blood, bone marrow and spleen chimerism, multi-organ pro-inflammatory cytokine profiles at 12 weeks and brain chimerism and immune cell infiltration by whole brain flow cytometry before and after implantation of glioblastoma at 12 and 14 weeks respectively. RESULTS: Both non-myeloablative conditioning and head-shielded irradiation achieve equivalent blood and spleen chimerism of approximately 80%, although bone marrow engraftment is higher in the head-shielded irradiation group and highest in the fully conditioned group. Head-shielded irradiation stimulated pro-inflammatory cytokines in the blood and spleen but not in the brain, suggesting a systemic response to irradiation, whilst non-myeloablative conditioning showed no cytokine elevation. Non-myeloablative conditioning achieved higher donor chimerism in the brain after glioblastoma implantation than head-shielded irradiation with an altered immune cell profile. CONCLUSION: Our data suggest that non-myeloablative conditioning generates a more homeostatic peripheral inflammatory environment than head-shielded irradiation to allow a more consistent evaluation of immune cells in glioblastoma and can be used to investigate the roles of peripheral immune cells and bone marrow-derived subsets in other neurological diseases.

Exogenous melatonin modulates carbon ion radiation-induced immune dysfunction in mice.

In spite of carbon ion radiotherapy is a talented modality for malignant tumor patients, the radiation damage of normal tissues adjacent to tumor and the dysfunction of immune system limits therapeutic gain. Protecting immune system against carbon ion radiation-caused damage has the possibility to improve cancer treatment, but it is uncertain whether conventional radioprotective agents play a role in carbon ion radiation. To certify carbon ion caused immune dysfunction and assess the radioprotective effect of melatonin on immune system, animal experiments were performed in radiosensitive BALB/C mice. Here, we observed the bodyweight loss, death and apoptosis, abnormal T-cell distributions in immune system in carbon ion radiated mice. Pretreatment with melatonin could increase the index of thymus and spleen, reduce cell apoptosis in thymus and spleen, and attenuate the carbon ion radiation-caused imbalance of T lymphocytes and disorder of cytokines. These results suggest that melatonin can act as an effective protector against carbon ion radiation-caused immune dysfunction. Furthermore, we also found melatonin restored the activity of the antioxidant enzymes and reduced the level of lipid peroxidation in serum. These data have provided baseline information both for radiation workers and cancer patients to use melatonin as a radioprotector during the carbon ion radiation treatment.

Exposure to Solar UVR Suppresses Cell-Mediated Immunization Responses in Humans: The Australian Ultraviolet Radiation and Immunity Study.

Animal and human studies show that exposure to solar-simulated UVR is immunomodulatory. Human studies that used natural sun exposure and controlled for confounding are rare. We immunized 217 healthy adults (age range = 18-40 years) with a T-cell-dependent antigen, keyhole limpet hemocyanin, and measured personal clothing-adjusted UVR exposure (for 5 days before and after immunization), lifetime cumulative UVR exposure, serum 25-hydroxyvitamin D concentration at immunization, and potential confounding factors. We tested cellular and humoral immune responses in relation to UVR exposure. The delayed-type hypersensitivity response to keyhole limpet hemocyanin recall challenge was lower in individuals with higher personal clothing-adjusted UVR exposure on the day before immunization (P = 0.015) and during intervals spanning the day before to 2-3 days after immunization. There was an incremental increase in T helper type 17 cells (as a proportion of CD4+ T cells) from preimmunization to postimmunization in the high, compared with the low, personal clothing-adjusted UVR exposure group (0.31% vs. -0.39%, P = 0.004). Keyhole limpet hemocyanin-specific antibody titers were not associated with acute or cumulative UVR exposure or serum 25-hydroxyvitamin D levels. Higher UVR exposure at antigen sensitization was associated with a reduced delayed-type hypersensitivity response and altered T helper type 17 kinetics. This has implications for the effectiveness of vaccinations and susceptibility to infections that rely on cell-mediated immune responses.

Nanoscale Reduced Graphene Oxide-Mediated Photothermal Therapy Together with IDO Inhibition and PD-L1 Blockade Synergistically Promote Antitumor Immunity.

Despite the potential efficacy of immune checkpoint blockade for effective treatment of cancer, this therapeutic modality is not generally curative, and only a fraction of patients respond. Combination approaches provide strategies to target multiple antitumor immune pathways to induce synergistic antitumor immunity. Here, a multi-combination immunotherapy, including photothermal therapy (PTT), indoleamine-2,3-dioxygenase (IDO) inhibition, and programmed cell death-ligand 1 (PD-L1) blockade, is introduced for inducing synergistic antitumor immunity. We designed a multifunctional IDO inhibitor (IDOi)-loaded reduced graphene oxide (rGO)-based nanosheets (IDOi/rGO nanosheets) with the properties to directly kill tumor cells under laser irradiation and in situ trigger antitumor immune response. In vivo experiments further revealed that the triggered immune response can be synergistically promoted by IDO inhibition and PD-L1 blockade; the responses included the enhancement of tumor-infiltrating lymphocytes, including CD45+ leukocytes, CD4+ T cells, CD8+ T cells, and NK cells; the inhibition of the immune suppression activity of regulator T cells (Tregs); and the production of INF-γ. We also demonstrate that the three combinations of PTT, IDO inhibition, and PD-L1 blockade can effectively inhibit the growth of both irradiated tumors and tumors in distant sites without PTT treatment. This work can be thought of as an important proof of concept to target multiple antitumor immune pathways to induce synergistic antitumor 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-ß 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.

The anti-PD-1 era - an opportunity to enhance radiotherapy for patients with bladder cancer.

An urgent need exists to improve the outcomes of patients with muscle-invasive bladder cancer (MIBC), and especially of those with metastatic disease. Treatments that enhance antitumour immune responses - such as immune-checkpoint inhibition - provide an opportunity to do this. Despite initial success, durable response rates in patients with advanced-stage MIBC treated with novel inhibitory antibodies targeting programmed cell death protein 1 (PD-1) or its endogenous ligand programmed cell death 1 ligand 1 (PD-L1) remain low. Radiotherapy is part of the management of bladder cancer in many patients. Evidence that radiotherapy has immunogenic properties is now available, but radiotherapy-induced immune responses are often negated by immunosuppression within the tumour microenvironment. Anti-PD-1 or anti-PD-L1 antibodies might enhance radiotherapy-induced antitumour immunity. This effect has been demonstrated in preclinical models of bladder cancer, and clinical trials involving this approach are currently recruiting. Combination treatment strategies provide an exciting opportunity for urological oncologists to not only improve the chances of cure in patients undergoing radical treatment for MIBC, but also to increase long-term response rates in those with metastatic disease.