• CENPS/X
• Chromatin
• DNA damage response
• Laser microirradiation
• MHF1/2
• RSF1

• Humans
• HeLa Cells
• DNA Breaks, Double-Stranded
• Nuclear Proteins/metabolism
• Chromatin/metabolism
• Trans-Activators/metabolism
• Chromosomal Proteins, Non-Histone/metabolism
• Ubiquitin-Protein Ligases/metabolism
• Ataxia Telangiectasia Mutated Proteins/metabolism
• DNA-Binding Proteins/metabolism
• DNA Repair
• DNA Damage
• Cell Cycle

• DNA repair foci
• X-ray
• fibroblasts
• hockey stick model
• residual foci
• threshold dose

• Humans
• Fibroblasts/radiation effects
• Fibroblasts/metabolism
• Fibroblasts/cytology
• Tumor Suppressor p53-Binding Protein 1
• Histones/metabolism
• Dose-Response Relationship, Radiation
• X-Rays
• Tumor Suppressor Protein p53/metabolism
• DNA Repair/radiation effects
• Intracellular Signaling Peptides and Proteins/metabolism
• DNA Breaks, Double-Stranded

• DDR
• DSB
• cytoskeletal protein
• neurodegenerative diseases
• tau

• tau Proteins/metabolism
• tau Proteins/genetics
• Humans
• Neurodegenerative Diseases/metabolism
• Neurodegenerative Diseases/genetics
• Neurodegenerative Diseases/pathology
• DNA Damage
• Animals
• DNA Repair
• Neurons/metabolism
• Neurons/pathology
• Cytoskeletal Proteins/metabolism
• Cytoskeletal Proteins/genetics

• Intramural reserch fund Shiga University of Medical Science
• JP22H02950 JSPS KAKENHI
• JP22485887 JSPS KAKENHI
• JP12345678 JSPS KAKENHI

• chromosomes
• dna

• Humans
• DNA Breaks, Double-Stranded/radiation effects
• Exodeoxyribonucleases/metabolism
• Exodeoxyribonucleases/genetics
• DNA Repair
• DNA Repair Enzymes/metabolism
• DNA Repair Enzymes/genetics
• Proliferating Cell Nuclear Antigen/metabolism
• Proliferating Cell Nuclear Antigen/genetics
• DNA/metabolism
• DNA/genetics
• Ubiquitination
• Cell Cycle Proteins

• Wellcome Trust
• 24759 Cancer Research UK
• CRUK/ A24759 Cancer Research UK (CRUK)

• Creatine
• l-arginine
• radioprotection

• Arginine/pharmacology
• Radiation-Protective Agents/pharmacology
• Creatine/pharmacology
• Dietary Supplements
• Animals
• Humans
• Oxidative Stress/drug effects
• Oxidative Stress/radiation effects

• DNA damage
• cancer therapeutics
• kinase
• phosphatase

• 2022R1A2C1091563 National Research Foundation of Korea
• 2019M3E5D3073092 National Research Foundation of Korea

• DNA Ligase IV
• NHEJ inhibitor
• V(D)J recombination
• cancer therapeutics
• double-strand break repair
• genomic instability

• Cancer treatment
• DNA double-strand breaks
• Double-strand break repair pathway
• Heavy-ion irradiation
• Radiotherapy
• Super-resolution microscopy

• DNA Breaks, Double-Stranded
• DNA Repair
• Linear Energy Transfer
• DNA/genetics
• Heavy Ion Radiotherapy
• Carbon

In studies on the mechanism of DNA damage response where ionizing radiation is used as the DNA damaging agent, cells are often exposed to ionizing radiation on melting ice (corresponding to 0.8 °C). The purpose of this procedure is to inhibit cellular processes i.e. DNA repair. Low temperature at exposure has been shown to act in a radioprotective manner at the level of cytogenetic damage, but its mechanisms of action are poorly understood. The aim of the study was to analyze the effect of hypothermia at the level of formation and decay of NBS1, γH2AX, and 53BP1 foci, micronuclei, survival, cell cycle progression and oxidative stress in U2OS cells. The results show that hypothermia alone induced oxidative stress and foci. When applied in combination with radiation but only during the exposure time, it potentiated the formation of γH2AX and 53BP1 but not of NBS1 foci. When applied during irradiation and subsequent repair time, 53BP1 and NBS1 foci formed and decayed, but the levels were markedly lower than when repair was carried out at 37 °C. The frequency of micronuclei was elevated in cells irradiated at 0.8 °C, but only when analysed 20 h after irradiation which is likely due to a reduced G₂ cell cycle block. Hypothermia reduced cell survival, both with and without radiation exposure. The temperature effect should be considered when cooling cells on melting ice to inhibit DNA repair in the induction of DNA damage.

Loss or rearrangement of genetic information can result from incorrect responses to DNA double strand breaks (DSBs). The cellular responses to DSBs encompass a range of highly coordinated events designed to detect and respond appropriately to the damage, thereby preserving genomic integrity. In analogy with events occurring during viral infection, we appropriate the terms Immediate-Early, Early, and Late to describe the pre-repair responses to DSBs. A distinguishing feature of the Immediate-Early response is that the large protein condensates that form during the Early and Late response and are resolved upon repair, termed foci, are not visible. The Immediate-Early response encompasses initial lesion sensing, involving poly (ADP-ribose) polymerases (PARPs), KU70/80, and MRN, as well as rapid repair by so-called ‘fast-kinetic’ canonical non-homologous end joining (cNHEJ). Initial binding of PARPs and the KU70/80 complex to breaks appears to be mutually exclusive at easily ligatable DSBs that are repaired efficiently by fast-kinetic cNHEJ; a process that is PARP-, ATM-, 53BP1-, Artemis-, and resection-independent. However, at more complex breaks requiring processing, the Immediate-Early response involving PARPs and the ensuing highly dynamic PARylation (polyADP ribosylation) of many substrates may aid recruitment of both KU70/80 and MRN to DSBs. Complex DSBs rely upon the Early response, largely defined by ATM-dependent focal recruitment of many signalling molecules into large condensates, and regulated by complex chromatin dynamics. Finally, the Late response integrates information from cell cycle phase, chromatin context, and type of DSB to determine appropriate pathway choice. Critical to pathway choice is the recruitment of p53 binding protein 1 (53BP1) and breast cancer associated 1 (BRCA1). However, additional factors recruited throughout the DSB response also impact upon pathway choice, although these remain to be fully characterised. The Late response somehow channels DSBs into the appropriate high-fidelity repair pathway, typically either ‘slow-kinetic’ cNHEJ or homologous recombination (HR). Loss of specific components of the DSB repair machinery results in cells utilising remaining factors to effect repair, but often at the cost of increased mutagenesis. Here we discuss the complex regulation of the Immediate-Early, Early, and Late responses to DSBs proceeding repair itself.

• Science Foundation Ireland

Squamous cell carcinoma is the most common type of head and neck cancer (HNSCC) with a disease-free survival at 3 years that does not exceed 30%. Biomarkers able to predict clinical outcomes are clearly needed. The purpose of this study was to investigate whether a short-term culture of tumour fragments irradiated ex vivo could anticipate patient responses to chemo- and/or radiotherapies. Biopsies were collected prior to treatment from a cohort of 28 patients with non-operable tumours of the oral cavity or oropharynx, and then cultured ex vivo. Short-term biopsy slice culture is a robust method that keeps cells viable for 7 days. Different biomarkers involved in the stemness status (CD44) or the DNA damage response (pATM and γ-H2AX) were investigated for their potential to predict the treatment response. A higher expression of all these markers was predictive of a poor response to treatment. This allowed the stratification of responder or non-responder patients to treatment. Moreover, the ratio for the expression of the three markers 24 h after 4 Gy irradiation versus 0 Gy was higher in responder than in non-responder patients. Finally, combining these biomarkers greatly improved their predictive potential, especially when the γ-H2AX ratio was associated with the CD44 ratio or the pATM ratio. These results encourage further evaluation of these biomarkers in a larger cohort of patients.

• CD44
• DNA damage response
• HNSCC
• ex vivo culture
• pATM
• predictive biomarker
• γ-H2AX foci

• Me45 cells
• ionizing radiation
• mRNA and miRNA expression
• miRNA biogenesis
• reporter genes

• B-Lymphocytes/enzymology
• Catalytic Domain/genetics
• Cell Cycle Proteins/chemistry
• Cell Cycle Proteins/genetics
• Cell Cycle Proteins/ultrastructure
• Crystallography, X-Ray
• DNA End-Joining Repair/genetics
• DNA Repair/genetics
• DNA-Binding Proteins/antagonists & inhibitors
• DNA-Binding Proteins/chemistry
• DNA-Binding Proteins/genetics
• DNA-Binding Proteins/ultrastructure
• Endonucleases/antagonists & inhibitors
• Endonucleases/chemistry
• Endonucleases/genetics
• Endonucleases/ultrastructure
• Enzyme Inhibitors/chemistry
• Exodeoxyribonucleases/chemistry
• Exodeoxyribonucleases/genetics
• Exodeoxyribonucleases/ultrastructure
• Humans
• Phosphorylation/genetics
• Protein Folding
• Severe Combined Immunodeficiency/enzymology
• Severe Combined Immunodeficiency/genetics
• Severe Combined Immunodeficiency/pathology
• T-Lymphocytes/enzymology

• A24759 Cancer Research UK
• 106244/Z/14/Z Wellcome Trust
• 24759 Cancer Research UK
• 106169/ZZ14/Z Wellcome Trust
• Wellcome Trust

• ATM
• DNA double-strand break
• homologous recombination
• ionizing radiation
• non-homologous end joining

• health effects
• radiation risk
• tritiated water (HTO)
• tritium

• Carcinogenesis/pathology
• Evidence-Based Medicine
• Humans
• Public Health
• Radiation Exposure
• Radiation, Ionizing
• Tritium/adverse effects

• JSPS

• DNA double strand break repair
• colorectal cancer
• replication stress
• target therapy

• DSB repair
• NHEJ
• artemis
• mechanistic modelling
• modelling DNA repair
• resection-dependent repair
• slow kinetics

• EC/730983-INSPIRE European Union's Horizon 2020 Research and Innovation program
• BRC-1215-20007 National Institute for Health Research Manchester Biomedical Research Centre: Radiotherapy Stream
• EP/S024344/1- BioProton United Kingdom Engineering and Physical Science Research Council
• 201806340232 China Scholarship Council

Laser-driven accelerators allow to generate ultrashort (from femto- to picoseconds) high peak dose-rate (up to tens of GGy/s) accelerated particle beams. However, the radiobiological effects of ultrashort pulsed irradiation are still poorly studied. The aim of this work was to compare the formation and elimination of γH2AX and 53BP1 foci (well known markers for DNA double-strand breaks (DSBs)) in Hela cells exposed to ultrashort pulsed electron beams generated by Advanced Research Electron Accelerator Laboratory (AREAL) accelerator (electron energy 3.6 MeV, pulse duration 450 fs, pulse repetition rates 2 or 20 Hz) and quasi-continuous radiation generated by Varian accelerator (electron energy 4 MeV) at doses of 250–1000 mGy. Additionally, a study on the dose–response relationships of changes in the number of residual γH2AX foci in HeLa and A549 cells 24 h after irradiation at doses of 500–10,000 mGy were performed. We found no statistically significant differences in γH2AX and 53BP1 foci yields at 1 h after exposure to 2 Hz ultrashort pulse vs. quasi-continuous radiations. In contrast, 20 Hz ultrashort pulse irradiation resulted in 1.27-fold higher foci yields as compared to the quasi-continuous one. After 24 h of pulse irradiation at doses of 500–10,000 mGy the number of residual γH2AX foci in Hela and A549 cells was 1.7–2.9 times higher compared to that of quasi-continuous irradiation. Overall, the obtained results suggest the slower repair rate for DSBs induced by ultrashort pulse irradiation in comparison to DSBs induced by quasi-continuous irradiation.

• 53BP1
• DNA double-strand breaks
• cancer cells
• ionizing radiation
• laser-driven accelerators
• ultrashort pulsed electron beam
• γH2AX

• A549 Cells
• DNA Breaks, Double-Stranded/radiation effects
• DNA Repair/radiation effects
• HeLa Cells
• Histones/genetics
• Histones/metabolism
• Humans
• Lasers
• Radiation, Ionizing
• Tumor Suppressor p53-Binding Protein 1/genetics
• Tumor Suppressor p53-Binding Protein 1/metabolism

• Bronchi/metabolism
• Bronchi/pathology
• Cell Transformation, Neoplastic/genetics
• Cell Transformation, Neoplastic/metabolism
• Cell Transformation, Neoplastic/pathology
• Cells, Cultured
• DNA Damage
• DNA Replication
• Epithelial Cells/metabolism
• Epithelial Cells/pathology
• Forkhead Box Protein M1/genetics
• Forkhead Box Protein M1/metabolism
• Genomic Instability/radiation effects
• Humans
• Radiation, Ionizing
• Stress, Physiological

• U.S. Department of Defense
• National Institutes of Health

Cisplatin based cancer therapy is an affordable and effective standard therapy for several solid cancers, including lung, ovarian and head and neck cancers. However, the clinical use of cisplatin is routinely limited by the development of drug resistance and subsequent therapeutic failure. Therefore, methods of circumventing cisplatin resistance have the potential to increase therapeutic efficiency and dramatically increase overall survival. Cisplatin resistance can be mediated by alterations to the DNA damage response, where multiple components of the repair machinery have been described to be client proteins of HSP90. In the present study, we have investigated whether therapy with the novel HSP90 inhibitor onalespib can potentiate the efficacy of cisplatin and potentially reverse cisplatin resistance in ovarian and head and neck cancer cells.

Cell viability, cancer cell proliferation and migration capacity were evaluated in vitro on models of ovarian and head and neck cancer cells. Western blotting was used to assess the downregulation of HSP90 client proteins and alterations in downstream signaling proteins after exposure to cisplatin and/or onalespib. Induction of apoptosis and DNA damage response were evaluated in both monotherapy and combination therapy groups.

Results demonstrate that onalespib enhances the efficiency of cisplatin in a dose-dependent manner. Tumor cells treated with both drugs displayed lower viability and a decreased migration rate compared to vehicle-control cells and cells treated with individual compounds. An increase of DNA double strand breaks was observed in both cisplatin and onalespib treated cells. The damage was highest and most persistent in the combination group, delaying the DNA repair machinery. Further, the cisplatin and onalespib co-treated cells had greater apoptotic activity compared to controls.

The results of this study demonstrate that the reduced therapeutic efficacy of cisplatin due to drug-resistance could be overcome by combination treatment with onalespib. We speculate that the increased apoptotic signaling, DNA damage as well as the downregulation of HSP90 client proteins are important mechanisms promoting increased sensitivity to cisplatin treatment.

• AT13387
• CDDP
• Hsp90 inhibition
• chemo-sensitization
• cisplatin
• combination treatment
• drug resistance
• synergy

Esophageal cancer is a common digestive tract tumor that is generally treated with radiotherapy. Poor responses to radiotherapy in most patients generally result in local radiotherapy failure, so it is essential to find new radiosensitizers that can enhance the response of cancer cells to radiotherapy and improve the survival of esophageal cancer patients with radiation resistance. The long non-coding RNA (lncRNA) Rpph1 is highly expressed in human gastric cancer tissues, and represses breast cancer cell proliferation and tumorigenesis. However, the expression of lncRNA Rpph1 in esophageal cancer and its relationship with radio-sensitivity has not been studied.

To explore the value of lncRNA Rpph1 in esophageal cancer and its effect on cancer cell sensitivity to radiotherapy.

Eighty-three patients with esophageal cancer admitted to Qilu Hospital of Shandong University and 90 healthy participants who received physical examinations were collected as research participants. The expression of Rpph1 was determined by qRT-PCR. siRNA-NC and siRNA-Rpph1 were transfected into esophageal cancer cell lines, and cells without transfection were designated as the blank control group. Cell survival was tested by colony formation assays, and the levels of proteins related to apoptosis and epithelial-mesenchymal transitions were determined by Western blot assays. Cell proliferation was assessed by MTT assays, cell apoptosis by flow cytometry, and cell migration by wound-healing assays. Changes in cell cycle distribution were monitored.

Rpph1 was highly expressed in esophageal carcinoma, making it a promising marker for the diagnosis of esophageal cancer. Rpph1 could also be used to distinguish different short-term responses, T stages, N stages, and clinical stages of esophageal cancer patients. The results of 3-year overall survival favored patients with lower Rpph1 expression over patients with higher Rpph1 expression (P < 0.05). In vitro and in vivo experiments showed that silencing Rpph1 expression led to higher sensitivity of esophageal cancer cells to radiotherapy, stronger apoptosis in esophageal cancer cells induced by radiotherapy, higher expression of Bax and caspase-3, and lower expression of Bcl-2 (Bax, caspase-3, and Bcl-2 are apoptosis-related proteins). Additionally, silencing Rpph1 attenuated radiation-induced G2/M phase arrest, and significantly inhibited the expression of proteins involved in cell proliferation, migration, and epithelial-mesenchymal transition regulation in esophageal cancer cells.

Rpph1 is highly expressed in esophageal cancer. Silencing Rpph1 expression can promote cell apoptosis, inhibit cell proliferation and migration, and increase radio-sensitivity.

• Long non-coding RNA Rpph1
• Esophageal cancer
• Cell sensitivity to radiotherapy
• Apoptosis
• Cell cycle
• Epithelial-mesenchymal transition

• Adenocarcinoma/genetics
• Adenocarcinoma/mortality
• Adenocarcinoma/pathology
• Adenocarcinoma/radiotherapy
• Aged
• Apoptosis/genetics
• Cell Line, Tumor
• Cell Movement/genetics
• Cell Proliferation/genetics
• Epithelial-Mesenchymal Transition/genetics
• Esophageal Neoplasms/genetics
• Esophageal Neoplasms/mortality
• Esophageal Neoplasms/pathology
• Esophageal Neoplasms/radiotherapy
• Esophageal Squamous Cell Carcinoma/genetics
• Esophageal Squamous Cell Carcinoma/mortality
• Esophageal Squamous Cell Carcinoma/pathology
• Esophageal Squamous Cell Carcinoma/radiotherapy
• Female
• Follow-Up Studies
• G2 Phase Cell Cycle Checkpoints/genetics
• Gene Expression Regulation, Neoplastic
• Humans
• Male
• Middle Aged
• RNA, Long Noncoding/genetics
• RNA, Long Noncoding/metabolism
• RNA, Small Interfering/metabolism
• Radiation Tolerance/genetics
• Treatment Outcome

Rationale: Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death worldwide, with high recurrence and metastasis rates. Although radiation is an effective treatment for tumors, it is often limited by intrinsic radioresistance in HCC. The contributions of dysregulated microRNAs, including miR-31-5p, to HCC progression have been recently reported. However, the role of miR-31-5p in the radiation response of HCC is unknown. In this study, we aimed to investigate the impact of miR-31-5p on HCC radiosensitivity.

Methods: miR-31-5p expression in HCC tissues, paired adjacent tissues, and HCC cell lines was measured using quantitative real-time polymerase chain reaction and in situ hybridization. Bioinformatic analyses, gain- and loss-of-function experiments, and luciferase reporter assays were performed to validate peroxisomal biogenesis factor 5 (PEX5) as a direct target of miR-31-5p. The biofunctions of PEX5 and miR-31-5p in HCC were determined by Transwell, wound-healing, and Cell Counting Kit-8 (CCK8) assays. A colony formation assay was used to evaluate the radiosensitivity of HCC cells. The interaction among PEX5, β-catenin, Rac1, and JNK-2 was confirmed by coimmunoprecipitation. A xenograft tumor model was established to validate the effects of miR-31-5p and PEX5 on HCC progression and radiosensitivity in vivo.

Results: Low expression of miR-31-5p in HCC specimens, as observed in this study, predicted a poor clinical outcome. However, the expression pattern of PEX5, as a direct target of miR-31-5p, was opposite that of miR-31-5p, and high PEX5 expression indicated poor prognosis in HCC patients. Ectopic expression of PEX5 increased the proliferation, migration, and invasion abilities and enhanced the radioresistance of HCC cells in vitro and in vivo; however, these phenotypes were inhibited by miR-31-5p. Mechanistically, PEX5 stabilized cytoplasmic β-catenin and facilitated β-catenin nuclear translocation to activate Wnt/β-catenin signaling. Moreover, upon radiation exposure, PEX5 reduced excessive reactive oxygen species (ROS) accumulation and activated the homologous recombination (HR) pathway, which protected HCC cells from radiation-induced damage.

Conclusions: Our findings demonstrated a novel role for PEX5 as a miR-31-5p target and a mediator of the Wnt/β-catenin signaling and HR pathways, providing new insights into studying HCC radiation responses and implicating PEX5 and miR-31-5p as potential therapeutic targets in HCC.

• Homologous Recombination
• PEX5
• Radiosensitivity
• miR-31-5p
• β-catenin

The significance of canonical DNA non-homologous end-joining (c-NHEJ) for DNA double strand break (DSB) repair has increased from lower organisms to higher eukaryotes, and plays the predominant role in human cells. Ku, the c-NHEJ end-binding component, binds DSBs with high efficiency enabling c-NHEJ to be the first choice DSB repair pathway, although alternative pathways can ensue after regulated steps to remove Ku. Indeed, radiation-induced DSBs are repaired rapidly in human cells. However, an important question is the fidelity with which radiation-induced DSBs are repaired, which is essential for assessing any harmful impacts caused by radiation exposure. Indeed, is compromised fidelity a price we pay for high capacity repair. Two subpathways of c-NHEJ have been revealed; a fast process that does not require nucleases or significant chromatin changes and a slower process that necessitates resection factors, and potentially more significant chromatin changes at the DSB. Recent studies have also shown that DSBs within transcriptionally active regions are repaired by specialised mechanisms, and the response at such DSBs encompasses a process of transcriptional arrest. Here, we consider the limitations of c-NHEJ that might result in DSB misrepair. We consider the common IR-induced misrepair events and discuss how they might arise via the distinct subpathways of c-NHEJ.

Accumulating evidence suggests a synergistic effect in cells simultaneously exposed to different types of clustered and dispersed DNA damage. We aimed to analyse the effect of mixed beams of alpha particles and X-rays (1:1 dose of each) on DNA damage response genes in human peripheral blood lymphocytes isolated from four donors. Two donors were compared upon inhibition of ATM or DNA-PK and at different sampling times. qPCR was used to measure mRNA levels of FDXR, GADD45A, BBC3, MDM2, CDKN1A, and XPC 24 h following exposure. Generally, alpha particles and mixed beams were stronger inducers of gene expression compared to X-rays, displaying saturated versus linear dose–response curves, respectively. Three out of four donors responded synergistically to mixed beams. When two donors were sampled again one year later, the former additive effect in one donor was now synergistic and no significant difference in intrinsic radiosensitivity was displayed, as determined by gamma-radiation-induced micronuclei. ATM, but not DNA-PK inhibition, reduced the radiation-induced gene expression, but differently for alpha radiation between the two donors. In conclusion, synergy was present for all donors, but the results suggest individual variability in the response to mixed beams, most likely due to lifestyle changes.

• DNA damage response
• gene expression
• radiation

• BRCA
• DNA polymerase theta
• DSB repair
• PARP inhibition (PARPi)
• alternative end joining (a-EJ)
• cancer therapy
• homologous recombination (HR)
• synthetic lethality

• rdna gene expression
• chromosome rearrangement
• cancer development

• Apoptosis
• Bone Neoplasms/genetics
• Bone Neoplasms/pathology
• Cell Nucleolus/genetics
• Cell Nucleolus/metabolism
• Cell Nucleolus/radiation effects
• Colorectal Neoplasms/genetics
• Colorectal Neoplasms/pathology
• DNA Damage
• DNA, Ribosomal/genetics
• DNA, Ribosomal/metabolism
• Humans
• Osteosarcoma/genetics
• Osteosarcoma/pathology
• Phosphoproteins/genetics
• Phosphoproteins/metabolism
• RNA, Ribosomal/genetics
• RNA, Ribosomal/metabolism
• RNA-Binding Proteins/genetics
• RNA-Binding Proteins/metabolism
• Radiation, Ionizing
• Transcription, Genetic
• Tumor Cells, Cultured
• Tumor Suppressor Protein p53/deficiency
• Tumor Suppressor Protein p53/genetics
• Nucleolin

• DNA damage
• clinical protocol
• combined modality therapy
• cytotoxic T lymphocyte
• signal transduction

• B7-H1 Antigen/antagonists & inhibitors
• B7-H1 Antigen/genetics
• B7-H1 Antigen/metabolism
• Cell Communication
• Cell Cycle Checkpoints
• Cell Death/physiology
• DNA Breaks, Double-Stranded
• DNA Damage
• DNA Fragmentation
• DNA Repair
• DNA, Neoplasm/drug effects
• DNA, Neoplasm/radiation effects
• Humans
• Lymphocyte Activation
• Membrane Proteins/metabolism
• Microsatellite Instability
• Mutation
• Neoplasms/genetics
• Neoplasms/immunology
• Neoplasms/metabolism
• Neoplasms/therapy
• Nucleotidyltransferases/metabolism
• Precision Medicine
• Programmed Cell Death 1 Receptor/antagonists & inhibitors
• Programmed Cell Death 1 Receptor/metabolism
• RNA, Messenger/metabolism
• Tumor Escape
• Up-Regulation

• Cell Science Research Foundation
• Takeda Science Foundation
• Yasuda Memorial Medical Foundation
• Program of the Network-type Joint Usage/Research Center for Radiation Disaster Medical Science of Hiroshima University, Nagasaki University, and Fukushima Medical University
• JP17H04713 Japan Society for the Promotion of Science
• JP17K16420 Japan Society for the Promotion of Science
• Daiichi Sankyo Foundation of Life Science

Radiotherapy (RT) has been applied for decades as a treatment modality in the management of various types of cancer. Ionizing radiation induces tumor cell death, which in turn can either elicit protective anti-tumor immune responses or immunosuppression in the tumor micromilieu that contributes to local tumor recurrence. Immunosuppression is frequently accompanied by the attraction of immunosuppressive cells such as myeloid-derived suppressor cells (MDSCs), M2 tumor-associated macrophages (TAMs), T regulatory cells (Tregs), N2 neutrophils, and by the release of immunosuppressive cytokines (TGF-β, IL-10) and chemokines. Immune checkpoint pathways, particularly of the PD-1/PD-L1 axis, have been determined as key regulators of cancer immune escape. While IFN-dependent upregulation of PD-L1 has been extensively investigated, up-to-date studies indicated the importance of DNA damage signaling in the regulation of PD-L1 expression following RT. DNA damage dependent PD-L1 expression is upregulated by ATM/ATR/Chk1 kinase activities and cGAS/STING-dependent pathway, proving the role of DNA damage signaling in PD-L1 induced expression. Checkpoint blockade immunotherapies (i.e., application of anti-PD-1 and anti-PD-L1 antibodies) combined with RT were shown to significantly improve the objective response rates in therapy of various primary and metastatic malignancies. Further improvements in the therapeutic potential of RT are based on combinations of RT with other immunotherapeutic approaches including vaccines, cytokines and cytokine inducers, and an adoptive immune cell transfer (DCs, NK cells, T cells). In the current review we provide immunological rationale for a combination of RT with various immunotherapies as well as analysis of the emerging preclinical evidences for these therapies.

• PD-1
• PD-L1
• immune checkpoint inhibitors
• immunosuppression
• radiotherapy