Details of a Researcher - Shibata, Atsushi

Papers - Shibata, Atsushi

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Reporting of methodologies used for clonogenic assays to determine radiosensitivity

Takahiro Oike, Shuichiro Komatsu, Yuka Komatsu, Ankita Nachankar, Narisa Dewi Maulany Darwis, Atsushi Shibata, Tatsuya Ohno

Journal of Radiation Research (Oxford University Press (OUP)) 61 ( 6 ) 828 - 831 2020.08

Research paper (scientific journal), Joint Work, Accepted, ISSN 0449-3060

<title>Abstract</title>
Radiotherapy treatment strategies should be personalized based on the radiosensitivity of individual tumors. Clonogenic assays are the gold standard method for in vitro assessment of radiosensitivity. Reproducibility is the critical factor for scientific rigor; however, this is reduced by insufficient reporting of methodologies. In reality, the reporting standards of methodologies pertaining to clonogenic assays remain unclear. To address this, we performed a literature search and qualitative analysis of the reporting of methodologies pertaining to clonogenic assays. A comprehensive literature review identified 1672 papers that report the radiosensitivity of human cancer cells based on clonogenic assays. From the identified papers, important experimental parameters (i.e. number of biological replicates, technical replicates, radiation source and dose rate) were recorded and analyzed. We found that, among the studies, (i) 30.5% did not report biological or technical replicates; (ii) 47.0% did not use biological or technical replicates; (iii) 3.8% did not report the radiation source; and (iv) 32.3% did not report the dose rate. These data suggest that reporting of methodologies pertaining to clonogenic assays in a considerable number of previously published studies is insufficient, thereby threatening reproducibility. This highlights the need to raise awareness of standardization of the methodologies used to conduct clonogenic assays.

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Relative Biological Effectiveness of Carbon Ions for Head-and-Neck Squamous Cell Carcinomas According to Human Papillomavirus Status

Naoto Osu, Daijiro Kobayashi, Katsuyuki Shirai, Atsushi Musha, Hiro Sato, Yuka Hirota, Atsushi Shibata, Takahiro Oike, Tatsuya Ohno

Journal of Personalized Medicine (MDPI AG) 10 ( 3 ) 71 - 71 2020.07

Research paper (scientific journal), Joint Work, Accepted

Carbon-ion radiotherapy (CIRT) has strong antitumor effects and excellent dose conformity. In head-and-neck squamous cell carcinoma (HNSCC), human papillomavirus (HPV) status is a prognostic factor for photon radiotherapy outcomes. However, the effect of HPV status on the sensitivity of HNSCCs to carbon ions remains unclear. Here, we showed that the relative biological effectiveness (RBE) of carbon ions over X-rays was higher in HPV-negative cells than in HSGc-C5 cells, which are used for CIRT dose establishment, whereas the RBE in HPV-positive cells was modest. These data indicate that CIRT is more advantageous in HPV-negative than in HPV-positive HNSCCs.

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RNF8 promotes high linear energy transfer carbon-ion-induced DNA double-stranded break repair in serum-starved human cells

Nakako Izumi Nakajima, Motohiro Yamauchi, Sangeeta Kakoti, Liu Cuihua, Reona Kato, Tiara Bunga Mayang Permata, Moito Iijima, Hirohiko Yajima, Takaaki Yasuhara, Shigeru Yamada, Sumitaka Hasegawa, Atsushi Shibata

DNA Repair (Elsevier BV) 91-92 102872 - 102872 2020.07

Research paper (scientific journal), Joint Work, Last author, Corresponding author, Accepted, ISSN 1568-7864

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UBC13-Mediated Ubiquitin Signaling Promotes Removal of Blocking Adducts from DNA Double-Strand Breaks

Remi Akagawa, Hai Thanh Trinh, Liton Kumar Saha, Masataka Tsuda, Kouji Hirota, Shintaro Yamada, Atsushi Shibata, Masato T. Kanemaki, Shinichiro Nakada, Shunichi Takeda, Hiroyuki Sasanuma

iScience (Elsevier BV) 23 ( 4 ) 101027 - 101027 2020.04

Research paper (scientific journal), Joint Work, Accepted, ISSN 2589-0042

Chemical modifications and adducts at DNA double-strand break (DSB) ends must be cleaned before re-joining by non-homologous end-joining (NHEJ). MRE11 nuclease is essential for efficient removal of Topoisomerase II (TOP2)-DNA adducts from TOP2 poison-induced DSBs. However, mechanisms in MRE11 recruitment to DSB sites in G1 phase remain poorly understood. Here, we report that TOP2-DNA adducts are expeditiously removed through UBC13-mediated polyubiquitination, which promotes DSB resection in G2 phase. We found that this ubiquitin signaling is required for efficient recruitment of MRE11 onto DSB sites in G1 by facilitating localization of RAP80 and BRCA1 to DSB sites and complex formation between BRCA1 and MRE11 at DSB sites. UBC13 and MRE11 are dispensable for restriction-enzyme-induced “clean” DSBs repair but responsible for over 50% and 70% of NHEJ-dependent repair of γ-ray-induced “dirty” DSBs, respectively. In conclusion, ubiquitin signaling promotes nucleolytic removal of DSB blocking adducts by MRE11 before NHEJ.

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p53 deficiency augments nucleolar instability after ionizing irradiation.

Sangeeta Kakoti, Motohiro Yamauchi, Wenchao Gu, Reona Kato, Takaaki Yasuhara, Yoshihiko Hagiwara, Siddhartha Laskar, Takahiro Oike, Hiro Sato, Kathryn D Held, Takashi Nakano, Atsushi Shibata

Oncology reports (Spandidos publications) 42 ( 6 ) 2293 - 2302 2019.12

Research paper (scientific journal), Joint Work, Last author, Corresponding author, Accepted

Ribosomes are important cellular components that maintain cellular homeostasis through overall protein synthesis. The nucleolus is a prominent subnuclear structure that contains ribosomal DNA (rDNA) encoding ribosomal RNA (rRNA), an essential component of ribosomes. Despite the significant role of the rDNA‑rRNA‑ribosome axis in cellular homeostasis, the stability of rDNA in the context of the DNA damage response has not been fully investigated. In the present study, the number and morphological changes of nucleolin, a marker of the nucleolus, were examined following ionizing radiation (IR) in order to investigate the impact of DNA damage on nucleolar stability. An increase in the number of nucleoli per cell was found in HCT116 and U2OS cells following IR. Interestingly, the IR‑dependent increase in nucleolar fragmentation was enhanced by p53 deficiency. In addition, the morphological analysis revealed several distinct types of nucleolar fragmentation following IR. The pattern of nucleolar morphology differed between HCT116 and U2OS cells, and the p53 deficiency altered the pattern of nucleolar morphology. Finally, a significant decrease in rRNA synthesis was observed in HCT116 p53‑/‑ cells following IR, suggesting that severe nucleolar fragmentation downregulates rRNA transcription. The findings of the present study suggest that p53 plays a key role in protecting the transcriptional activity of rDNA in response to DNA damage.

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Deep learning-assisted literature mining for in vitro radiosensitivity data.

Shuichiro Komatsu, Takahiro Oike, Yuka Komatsu, Yoshiki Kubota, Makoto Sakai, Toshiaki Matsui, Endang Nuryadi, Tiara Bunga Mayang Permata, Hiro Sato, Hidemasa Kawamura, Masahiko Okamoto, Takuya Kaminuma, Kazutoshi Murata, Naoko Okano, Yuka Hirota, Tatsuya Ohno, Jun-Ichi Saitoh, Atsushi Shibata, Takashi Nakano

Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology (Elsevier) 139 87 - 93 2019.10

Joint Work, Accepted

BACKGROUND AND PURPOSE: Integrated analysis of existing radiosensitivity data obtained by the gold-standard clonogenic assay has the potential to improve our understanding of cancer cell radioresistance. However, extraction of radiosensitivity data from the literature is highly labor-intensive. To aid in this task, using deep convolutional neural networks (CNNs) and other computer technologies, we developed an analysis pipeline that extracts radiosensitivity data derived from clonogenic assays from the literature. MATERIALS AND METHODS: Three classifiers (C1-3) were developed to identify publications containing radiosensitivity data derived from clonogenic assays. C1 uses Faster Regions CNN with Inception Resnet v2 (fRCNN-IRv2), VGG-16, and Optical Character Recognition (OCR) to identify publications that contain semi-logarithmic graphs showing radiosensitivity data derived from clonogenic assays. C2 uses fRCNN-IRv2 and OCR to identify publications that contain bar graphs showing radiosensitivity data derived from clonogenic assays. C3 is a program that identifies publications containing keywords related to radiosensitivity data derived from clonogenic assays. A program (iSF2) was developed using Mask RCNN and OCR to extract surviving fraction after 2-Gy irradiation (SF2) as assessed by clonogenic assays, presented in semi-logarithmic graphs. The efficacy of C1-3 and iSF2 was tested using seven datasets (1805 and 222 publications in total, respectively). RESULTS: C1-3 yielded sensitivity of 91.2% ± 3.4% and specificity of 90.7% ± 3.6%. iSF2 returned SF2 values that were within 2.9% ± 2.6% of the SF2 values determined by radiation oncologists. CONCLUSION: Our analysis pipeline is potentially useful to acquire radiosensitivity data derived from clonogenic assays from the literature.

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FGFR Signaling as a Candidate Therapeutic Target for Cancers Resistant to Carbon Ion Radiotherapy.

Narisa Dewi Maulany Darwis, Ankita Nachankar, Yasushi Sasaki, Toshiaki Matsui, Shin-Ei Noda, Kazutoshi Murata, Tomoaki Tamaki, Ken Ando, Noriyuki Okonogi, Shintaro Shiba, Daisuke Irie, Takuya Kaminuma, Takuya Kumazawa, Mai Anakura, Souichi Yamashita, Takashi Hirakawa, Sangeeta Kakoti, Yuka Hirota, Takashi Tokino, Akira Iwase, Tatsuya Ohno, Atsushi Shibata, Takahiro Oike, Takashi Nakano

International journal of molecular sciences (MDPI) 20 ( 18 ) 4563 2019.09

Research paper (scientific journal), Joint Work, Accepted

Radiotherapy is an essential component of cancer therapy. Carbon ion radiotherapy (CIRT) promises to improve outcomes compared with standard of care in many cancers. Nevertheless, clinicians often observe in-field recurrence after CIRT. This indicates the presence of a subset of cancers that harbor intrinsic resistance to CIRT. Thus, the development of methods to identify and sensitize CIRT-resistant cancers is needed. To address this issue, we analyzed a unique donor-matched pair of clinical specimens: a treatment-naïve tumor, and the tumor that recurred locally after CIRT in the same patient. Exon sequencing of 409 cancer-related genes identified enrichment of somatic mutations in FGFR3 and FGFR4 in the recurrent tumor compared with the treatment-naïve tumor, indicating a pivotal role for FGFR signaling in cancer cell survival through CIRT. Inhibition of FGFR using the clinically available pan-FGFR inhibitor LY2874455 sensitized multiple cancer cell lines to carbon ions at 3 Gy (RBE: relative biological effectiveness), the daily dose prescribed to the patient. The sensitizer enhancement ratio was 1.66 ± 0.17, 1.27 ± 0.09, and 1.20 ± 0.18 in A549, H1299, and H1703 cells, respectively. Our data indicate the potential usefulness of the analytical pipeline employed in this pilot study to identify targetable mutations associated with resistance to CIRT, and of LY21874455 as a sensitizer for CIRT-resistant cancers. The results warrant validation in larger cohorts.

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Robustness of Clonogenic Assays as a Biomarker for Cancer Cell Radiosensitivity.

Toshiaki Matsui, Endang Nuryadi, Shuichiro Komatsu, Yuka Hirota, Atsushi Shibata, Takahiro Oike, Takashi Nakano

International journal of molecular sciences (MDPI) 20 ( 17 ) 4148 2019.08

Research paper (scientific journal), Joint Work, Accepted

Photon radiation therapy is a major curative treatment for cancer. However, the lack of robust predictive biomarkers for radiosensitivity precludes personalized radiation therapy. Clonogenic assays are the gold standard method for measuring the radiosensitivity of cancer cells. Although a large number of publications describe the use of clonogenic assays to measure cancer cell radiosensitivity, the robustness of results from different studies is unclear. To address this, we conducted a comprehensive detailed literature search of 256 common cancer cell lines and identified the eight cell lines most-frequently examined for photon sensitivity using clonogenic assays. Survival endpoints and experimental parameters from all 620 relevant experiments were compiled and analyzed. We found that the coefficients of variation for SF2 (surviving fraction after 2 Gy irradiation) and for D10 (dose that yields a surviving fraction of 10%) were below 30% for all cell lines, indicating that SF2 and D10 have acceptable inter-assay precision. These data support further analysis of published data on clonogenic assays using SF2 and D10 as survival endpoints, which facilitates robust identification of biological profiles representative of cancer cell sensitivity to photons.

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Radiosensitivity Differences between EGFR Mutant and Wild-Type Lung Cancer Cells are Larger at Lower Doses

Mai Anakura, Ankita Nachankar, Daijiro Kobayashi, Napapat Amornwichet, Yuka Hirota, Atsushi Shibata, Takahiro Oike, Takashi Nakano

International Journal of Molecular Sciences (MDPI) 20 ( 15 ) 3635 2019.07

Research paper (scientific journal), Joint Work, Accepted

In the era of precision medicine, radiotherapy strategies should be determined based on genetic profiles that predict tumor radiosensitivity. Accordingly, pre-clinical research aimed at discovering clinically applicable genetic profiles is needed. However, how a given genetic profile affects cancer cell radiosensitivity is unclear. To address this issue, we performed a pilot in vitro study by utilizing EGFR mutational status as a model for genetic profile. Clonogenic assays of EGFR mutant (n = 6) and wild-type (n = 9) non-small cell lung carcinoma (NSCLC) cell lines were performed independently by two oncologists. Clonogenic survival parameters SF2, SF4, SF6, SF8, mean inactivation dose (MID), D10, D50, α, and β were obtained using the linear quadratic model. The differences in the clonogenic survival parameters between the EGFR mutant and wild-type cell lines were assessed using the Mann-Whitney U test. As a result, for both datasets, the p values for SF2, SF4, D50, α, and α/β were below 0.05, and those for SF2 were lowest. These data indicate that a genetic profile of NSCLC cell lines might be predictive for their radiation response; i.e., EGFR mutant cell lines might be more sensitive to low dose- and low fraction sized-irradiation.

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Base excision repair regulates PD-L1 expression in cancer cells.

Tiara Bunga Mayang Permata, Yoshihiko Hagiwara, Hiro Sato, Takaaki Yasuhara, Takahiro Oike, Soehartati Gondhowiardjo, Kathryn D Held, Takashi Nakano, Atsushi Shibata

Oncogene (Springer nature) 38 ( 23 ) 4452 - 4466 2019.06

Research paper (scientific journal), Joint Work, Last author, Corresponding author, Accepted

Programmed death-ligand 1 (PD-L1) is a key factor influencing cancer immunotherapy; however, the regulation of PD-L1 expression in cancer cells remains unclear, particularly regarding DNA damage, repair and its signalling. Herein, we demonstrate that oxidative DNA damage induced by exogenously applied hydrogen peroxide (H2O2) upregulates PD-L1 expression in cancer cells. Further, depletion of the base excision repair (BER) enzyme DNA glycosylase augments PD-L1 upregulation in response to H2O2. PD-L1 upregulation in BER-depleted cells requires ATR/Chk1 kinase activities, demonstrating that PD-L1 upregulation is mediated by DNA damage signalling. Further analysis of The Cancer Genome Atlas revealed that the expression of PD-L1 is negatively correlated with that of the BER/single-strand break repair (SSBR) and tumours with low BER/SSBR gene expression show high microsatellite instability and neoantigen production. Hence, these results suggest that PD-L1 expression is regulated in cancer cells via the DNA damage signalling and neoantigen-interferon-γ pathway under oxidative stress.

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Elucidation of the Mechanism Regulating Transcription Associated DNA Double Strand Break Repair and Its Pathway.

Atsushi Shibata, Takaaki Yasuhara

Impact (Science Impact Ltd) 2019 ( 3 ) 50 - 51 2019.03

Research paper (scientific journal), Joint Work, Lead author, Corresponding author, Accepted

The ability to repair breaks and mutations in DNA is essential for a cell's – and therefore organism's – survival. Breaks and other mutations arise naturally over time and are dealt with by the cell using several different pathways. Incorrect or non-existent DNA repair can lead directly to either cell death or the development of a cancerous cell. A break in double strand in the DNA is particularly serious. Dr Atsushi Shibata, a Principle Investigator and Senior Lecturer at Gunma University, Japan explains that the cell has two key ways to deal with this sort of break. 'These are homologous recombination repair (HRR) and non-homologous end-joining (NHEJ),' he says. 'HRR is the more accurate pathway, while NHEJ provides a quicker fix, but it has a risk of error under some circumstance.' This makes HRR perfectly suited to repairing important parts of the genome whilst NHEJ is better suited to less key regions.
The molecular mechanisms behind these repair pathways have been extensively studied. However, the question of how a particular pathway is selected over another in different situations is less well characterised, particularly in human normal cells as well as cancer cells. Uncovering the signalling pathways behind this choice the cell makes is both very important to our fundamental understanding of DNA repair and to its potential use in tackling cancer. Investigating these pathways Shibata is collaborating with Dr Takaaki Yasuhara from the University of Tokyo. They have revealed some of the inner workings behind the choice of repair pathway.
Previously, Shibata has shown that the NHEJ was the default choice for repairing DSBs, but that HRR is then selected if the re-joining does not occur properly. He has also shown a fundamental role of MRE11 nuclease in determining the type of repair that occurs at a DSB. Additionally, Shibata has shown the crucial role BRCA1 has in directing the repair of DSB towards the HRR pathway. In short, his work in the field is internationally recognised. 'These studies have contributed to the establishment of research basis for the recent discovery in the study of transcription-associated HRR,' observes Shibata.

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Clustered DNA double-strand break formation and the repair pathway following heavy-ion irradiation.

Yoshihiko Hagiwara, Takahiro Oike, Atsuko Niimi, Motohiro Yamauchi, Hiro Sato, Siripan Limsirichaikul, Kathryn D Held, Takashi Nakano, Atsushi Shibata

Journal of radiation research (Oxford University Press) 60 ( 1 ) 69 - 79 2019.01

Research paper (scientific journal), Joint Work, Last author, Corresponding author, Accepted

Photons, such as X- or γ-rays, induce DNA damage (distributed throughout the nucleus) as a result of low-density energy deposition. In contrast, particle irradiation with high linear energy transfer (LET) deposits high-density energy along the particle track. High-LET heavy-ion irradiation generates a greater number and more complex critical chromosomal aberrations, such as dicentrics and translocations, compared with X-ray or γ irradiation. In addition, the formation of >1000 bp deletions, which is rarely observed after X-ray irradiation, has been identified following high-LET heavy-ion irradiation. Previously, these chromosomal aberrations have been thought to be the result of misrepair of complex DNA lesions, defined as DNA damage through DNA double-strand breaks (DSBs) and single-strand breaks as well as base damage within 1-2 helical turns (<3-4 nm). However, because the scale of complex DNA lesions is less than a few nanometers, the large-scale chromosomal aberrations at a micrometer level cannot be simply explained by complex DNA lesions. Recently, we have demonstrated the existence of clustered DSBs along the particle track through the use of super-resolution microscopy. Furthermore, we have visualized high-level and frequent formation of DSBs at the chromosomal boundary following high-LET heavy-ion irradiation. In this review, we summarize the latest findings regarding the hallmarks of DNA damage structure and the repair pathway following heavy-ion irradiation. Furthermore, we discuss the mechanism through which high-LET heavy-ion irradiation may induce dicentrics, translocations and large deletions.

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Human Rad52 Promotes XPG-Mediated R-loop Processing to Initiate Transcription-Associated Homologous Recombination Repair.

Takaaki Yasuhara, Reona Kato, Yoshihiko Hagiwara, Bunsyo Shiotani, Motohiro Yamauchi, Shinichiro Nakada, Atsushi Shibata, Kiyoshi Miyagawa

Cell (Cell Press) 175 ( 2 ) 558 - 570 2018.10

Research paper (scientific journal), Joint Work, Corresponding author, Accepted, ISSN 0092-8674

Given that genomic DNA exerts its function by being transcribed, it is critical for the maintenance of homeostasis that DNA damage, such as double-strand breaks (DSBs), within transcriptionally active regions undergoes accurate repair. However, it remains unclear how this is achieved. Here, we describe a mechanism for transcription-associated homologous recombination repair (TA-HRR) in human cells. The process is initiated by R-loops formed upon DSB induction. We identify Rad52, which is recruited to the DSB site in a DNA-RNA-hybrid-dependent manner, as playing pivotal roles in promoting XPG-mediated R-loop processing and initiating subsequent repair by HRR. Importantly, dysfunction of TA-HRR promotes DSB repair via non-homologous end joining, leading to a striking increase in genomic aberrations. Thus, our data suggest that the presence of R-loops around DSBs within transcriptionally active regions promotes accurate repair of DSBs via processing by Rad52 and XPG to protect genomic information in these critical regions from gene alterations.

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Mutational analysis of uterine cervical cancer that survived multiple rounds of radiotherapy.

Endang Nuryadi, Yasushi Sasaki, Yoshihiko Hagiwara, Tiara Bunga Mayang Permata, Hiro Sato, Shuichiro Komatsu, Yuya Yoshimoto, Kazutoshi Murata, Ken Ando, Nobuteru Kubo, Noriyuki Okonogi, Yosuke Takakusagi, Akiko Adachi, Mototaro Iwanaga, Keisuke Tsuchida, Tomoaki Tamaki, Shin-Ei Noda, Yuka Hirota, Atsushi Shibata, Tatsuya Ohno, Takashi Tokino, Takahiro Oike, Takashi Nakano

Oncotarget 9 32642 - 32652 2018.08

Research paper (scientific journal), Joint Work, Accepted

Radiotherapy is an essential component of cancer therapy. Despite advances in cancer genomics, the mutation signatures of radioresistant tumors have not yet been fully elucidated. To address this issue, we analyzed a unique set of clinical specimens from a uterine cervical cancer that repeatedly locally recurred after multiple rounds of radiotherapy. Exon sequencing of 409 cancer-related genes in the treatment-naïve tumor and the tumors that recurred after initial and secondary radiotherapy identified (i) activating mutations in PIK3CA and KRAS, and putative inactivating mutations in SMAD4, as trunk mutation signatures that persisted over the clinical course; and (ii) mutations in KMT2A, TET1, and NLRP1 as acquired mutation signatures observed only in recurrent tumors after radiotherapy. Comprehensive mining of published in vitro genomics data pertaining to radiosensitivity revealed that simultaneous mutations in KRAS and SMAD4, which have not been described previously in uterine cervical cancer, are associated with cancer cell radioresistance. The association between this mutation signature and radioresistance was validated by isogenic cell-based experiments. These results provide proof-of-principle for the analytical pipeline employed in this study, which explores clinically relevant mutation signatures for radioresistance, and demonstrate that this approach is worth pursuing with larger cohorts in the future.

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Analysis of programmed death-ligand 1 expression in primary normal human dermal fibroblasts after DNA damage.

Yoshihiko Hagiwara, Hiro Sato, Tiara Bunga Mayang Permata, Atsuko Niimi, Motohiro Yamauchi, Takahiro Oike, Takashi Nakano, Atsushi Shibata

Human immunology (Elsevier) 79 ( 8 ) 627 - 631 2018.05

Research paper (scientific journal), Joint Work, Last author, Corresponding author, Accepted, ISSN 0198-8859

Programmed cell death-1 (PD-1) and its ligand (programmed death-ligand 1, PD-L1) are key factors that regulate a cytotoxic immune reaction. Anti-PD-1 therapy provides significant clinical benefits for patients with cancer, even those with advanced-stage cancer. We have recently demonstrated that DNA damage signaling from DNA double-strand breaks (DSBs) promotes PD-L1 upregulation in cancer cells. In the present study, we aimed to investigate PD-L1 expression in primary normal human dermal fibroblasts (NHDFs) in response to DSBs. We demonstrated that PD-L1 expression in NHDFs is not upregulated after ionizing radiation (IR). In addition, interferon (IFN) regulatory factor 1 (IRF1) and signal transducer and activator of transcription 1 (STAT1) phosphorylation do not respond in NHDFs after IR. In contrast, IFNγ treatment upregulates PD-L1 and IRF1 expressions and STAT1 phosphorylation. The nonresponsiveness was also observed after treatment with other DNA-damaging agents, such as camptothecin and etoposide. Treatment with a histone deacetylase inhibitor (HDACi), which causes chromatin relaxation and restores gene silencing, upregulates PD-L1 without exogenous DNA damage; however, IR-dependent upregulation is not observed in NHDFs treated with HDACi. Taken together, our data suggest that DNA-damage signaling is insufficient for upregulating PD-L1 in NHDFs.

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3D-structured illumination microscopy reveals clustered DNA double-strand break formation in widespread γH2AX foci after high LET heavy-ion particle radiation.

Yoshihiko Hagiwara, Atsuko Niimi, Mayu Isono, Motohiro Yamauchi, Takaaki Yasuhara, Siripan Limsirichaikul, Takahiro Oike, Hiro Sato, Kathryn D Held, Takashi Nakano, Atsushi Shibata

Oncotarget 8 109370 - 109381 2017.11

Research paper (scientific journal), Joint Work, Last author, Corresponding author, Accepted

DNA double-strand breaks (DSBs) induced by ionising radiation are considered the major cause of genotoxic mutations and cell death. While DSBs are dispersed throughout chromatin after X-rays or γ-irradiation, multiple types of DNA damage including DSBs, single-strand breaks and base damage can be generated within 1-2 helical DNA turns, defined as a complex DNA lesion, after high Linear Energy Transfer (LET) particle irradiation. In addition to the formation of complex DNA lesions, recent evidence suggests that multiple DSBs can be closely generated along the tracks of high LET particle irradiation. Herein, by using three dimensional (3D)-structured illumination microscopy, we identified the formation of 3D widespread γH2AX foci after high LET carbon-ion irradiation. The large γH2AX foci in G2-phase cells encompassed multiple foci of replication protein A (RPA), a marker of DSBs undergoing resection during homologous recombination. Furthermore, we demonstrated by 3D analysis that the distance between two individual RPA foci within γH2AX foci was approximately 700 nm. Together, our findings suggest that high LET heavy-ion particles induce clustered DSB formation on a scale of approximately 1 μm3. These closely localised DSBs are considered to be a risk for the formation of chromosomal rearrangement after heavy-ion irradiation.

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DNA double-strand break repair pathway regulates PD-L1 expression in cancer cells

Hiro Sato, Atsuko Niimi, Takaaki Yasuhara, Tiara Bunga Mayang Permata, Yoshihiko Hagiwara, Mayu Isono, Endang Nuryadi, Ryota Sekine, Takahiro Oike, Sangeeta Kakoti, Yuya Yoshimoto, Kathryn D. Held, Yoshiyuki Suzuki, Koji Kono, Kiyoshi Miyagawa, Takashi Nakano, Atsushi Shibata

NATURE COMMUNICATIONS (NATURE PUBLISHING GROUP) 8 ( 1 ) 1751 2017.11

Research paper (scientific journal), Joint Work, Last author, Corresponding author, Accepted, ISSN 2041-1723

Accumulating evidence suggests that exogenous cellular stress induces PD-L1 upregulation in cancer. A DNA double-strand break (DSB) is the most critical type of genotoxic stress, but the involvement of DSB repair in PD-L1 expression has not been investigated. Here we show that PD-L1 expression in cancer cells is upregulated in response to DSBs. This upregulation requires ATM/ATR/Chk1 kinases. Using an siRNA library targeting DSB repair genes, we discover that BRCA2 depletion enhances Chk1-dependent PD-L1 upregulation after X-rays or PARP inhibition. In addition, we show that Ku70/80 depletion substantially enhances PD-L1 upregulation after X-rays. The upregulation by Ku80 depletion requires Chk1 activation following DNA end-resection by Exonuclease 1. DSBs activate STAT1 and STAT3 signalling, and IRF1 is required for DSB-dependent PD-L1 upregulation. Thus, our findings reveal the involvement of DSB repair in PD-L1 expression and provide mechanistic insight into how PD-L1 expression is regulated after DSBs.

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Aquarius is required for proper CtIP expression and homologous recombination repair

Ryo Sakasai, Mayu Isono, Mitsuo Wakasugi, Mitsumasa Hashimoto, Yumi Sunatani, Tadashi Matsui, Atsushi Shibata, Tsukasa Matsunaga, Kuniyoshi Iwabuchi

SCIENTIFIC REPORTS (NATURE PUBLISHING GROUP) 7 13808 2017.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 2045-2322

Accumulating evidence indicates that transcription is closely related to DNA damage formation and that the loss of RNA biogenesis factors causes genome instability. However, whether such factors are involved in DNA damage responses remains unclear. We focus here on the RNA helicase Aquarius (AQR), a known R-loop processing factor, and show that its depletion in human cells results in the accumulation of DNA damage during S phase, mediated by R-loop formation. We investigated the involvement of Aquarius in DNA damage responses and found that AQR knockdown decreased DNA damage-induced foci formation of Rad51 and replication protein A, suggesting that Aquarius contributes to homologous recombination (HR)-mediated repair of DNA double-strand breaks (DSBs). Interestingly, the protein level of CtIP, a DSB processing factor, was decreased in AQR-knockdown cells. Exogenous expression of Aquarius partially restored CtIP protein level; however, CtIP overproduction did not rescue defective HR in AQR-knockdown cells. In accordance with these data, Aquarius depletion sensitized cells to genotoxic agents. We propose that Aquarius contributes to the maintenance of genomic stability via regulation of HR by CtIP-dependent and -independent pathways.

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One-step Protocol for Evaluation of the Mode of Radiation-induced Clonogenic Cell Death by Fluorescence Microscopy

Daijiro Kobayashi, Atsushi Shibata, Takahiro Oike, Takashi Nakano

JOVE-JOURNAL OF VISUALIZED EXPERIMENTS (JOURNAL OF VISUALIZED EXPERIMENTS) ( 128 ) e56338 2017.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 1940-087X

Research on ionizing radiation (IR)-induced clonogenic cell death is important for understanding the effect of IR on malignant tumors and normal tissues. Here, we describe a quick and cost-effective one-step assay for simultaneously assessing the major modes of clonogenic cell death induced by IR, i.e., apoptosis, mitotic catastrophe, and cellular senescence. In this method, cells grown on a cover slip are irradiated with Xrays and stained with 4',6-diamidino-2-phenylindole dihydrochloride (DAPI). Using fluorescence microscopy, apoptosis, mitotic catastrophe, and cellular senescence are identified based on the characteristic morphologies of the DAPI-stained nuclei. Apoptosis is determined by the presence of apoptotic bodies (i.e., condensed and fragmented nuclei). Mitotic catastrophe is determined by the presence of nuclei that exhibit two or more distinct lobes and micronuclei. Cellular senescence is determined by the presence of senescence-associated heterochromatic foci (i.e., nuclear DNA containing 30-50 bright, dense foci). This approach allows the experimenter to easily screen for clonogenic cell death modes using various cell lines, treatment settings, and/or time points, with the goal of elucidating the mechanisms of cell death in the target cells and conditions of interest.

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Inhibition of the HDAC/Suv39/G9a pathway restores the expression of DNA damage-dependent major histocompatibility complex class I-related chain A and B in cancer cells

Nakako Izumi Nakajima, Atsuko Niimi, Mayu Isono, Takahiro Oike, Hiro Sato, Takashi Nakano, Atsushi Shibata

Oncology Reports (Spandidos publications) 38 693 - 702 2017.06

Research paper (scientific journal), Joint Work, Last author, Corresponding author, Accepted, ISSN 1021-335X

Immunotherapy is expected to be promising as a next generation cancer therapy. Immunoreceptors are often activated constitutively in cancer cells, however, such levels of ligand expression are not effectively recognized by the native immune system due to tumor microenvironmental adaptation. Studies have demonstrated that natural-killer group 2, member D (NKG2D), a major activating immunoreceptor, responds to DNA damage. The upregulation of major histocompatibility complex class I-related chain A and B (MICA/B) (members of NKG2D ligands) expression after DNA damage is associated with NK cell-mediated killing of cancer cells. However, the regulation of DNA damage-induced MICA/B expression has not been fully elucidated in the context of the types of cancer cell lines. In the present study, we found that MICA/B expression varied between cancer cell lines after DNA damage. Screening in terms of chromatin remodeling identified that inhibitors related to chromatin relaxation via post-translational modification on histone H3K9, i.e. HDAC, Suv39 or G9a inhibition, restored DNA damage-dependent MICA/B expression in insensitive cells. In addition, we revealed that the restored MICA/B expression was dependent on ATR as well as E2F1, a transcription factor. We further revealed that low-dose treatment of an HDAC inhibitor was sufficient to restore MICA/B expression in insensitive cells. Finally, we demonstrated that HDAC inhibition restored DNA damage-dependent cytotoxic NK activity against insensitive cells. Thus, the present study revealed that DNA damage-dependent MICA/B expression in insensitive cancer cells can be restored by chromatin relaxation via the HDAC/Suv39/G9a pathway. Collectively, manipulation of chromatin status by therapeutic cancer drugs may potentiate the antitumor effect by enhancing immune activation following radiotherapy and DNA damage-associated chemotherapy.

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