In this work, the suitability and performance of a mouse-size MOSFET (Mousefet) phantom is investigated for routine quality assurance (QA) of the small animal radiation research platform (SARRP). This Mousefet phantom is a simple construction consisting of five micro-MOSFETS custom integrated in a quincunx pattern within a tissue-equivalent phantom, allowing repeat/multiple QA tasks to be quickly performed in one experimental set-up. The Mousefet phantom is particularly evaluated for facilitating SARRP QA tasks which may warrant daily evaluation, including output constancy, isocenter congruency test and cone beam computed tomography (CBCT) image geometric accuracy. Results for the output constancy measurements showed a maximum daily variation of less than 2.6% for all MOSFETS, in consonance with observations from concurrent ion chamber measurements. It is also shown that the design of the Mousefet phantom allows the output check data to be used for prompt verification of beam energy and cone profile constancy. For the isocenter congruency test, it is demonstrated that the Mousefet phantom can detect 0.3 mm deviations of the CBCT isocenter from the radiation isocenter. Meanwhile, results for CBCT image geometric accuracy were consistently found to be within 2% of the expected value. Other CBCT image quality parameters could also be assessed in terms of image intensity constancy, noise and image uniformity. Overall, the results establish the Mousefet phantom as a simple and time-efficient multipurpose tool that could be employed effectively for routine QA of the SARRP.
Ngwa W, Tsiamas P, Zygmanski P, Makrigiorgos GM, Berbeco RI.
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Cellular Autofluorescence following Ionizing Radiation.
Cells often autofluoresce in response to UV radiation excitation and this can reflect critical aspects of cellular metabolism. Here we report that many different human and murine cell types respond to ionizing radiation with a striking rise in autofluorescence that is dependent on dose and time. There was a highly reproducible fluorescent shift at various wavelengths, which was mirrored by an equally reproducible rise in the vital intracellular metabolic co-factors FAD and NADH. It appears that mitochondria, metabolism and Ca2+ homeostasis are important for this to occur as cells without mitochondria or cells unable to alter calcium levels did not behave in this way. We believe these radiation-induced changes are of biological importance and that autofluorescence may even provide us with a tool to monitor radiation responses in the clinic.
Dörthe Schaue, Josephine A Ratikan and Keisuke S Iwamoto
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Radiosensitization of Normoxic and Hypoxic H1339 Lung Tumor Cells by Heat Shock Protein 90 Inhibition Is Independent of Hypoxia Inducible Factor-1a.
Ionizing irradiation is a commonly accepted treatment modality for lung cancer patients. However, the clinical outcome is hampered by normal tissue toxicity and tumor hypoxia. Since tumors often have higher levels of active heat shock protein 90 (Hsp90) than normal tissues, targeting of Hsp90 might provide a promising strategy to sensitize tumors towards irradiation. Hsp90 client proteins include oncogenic signaling proteins, cell cycle activators, growth factor receptors and hypoxia inducible factor-1α (HIF-1α). Overexpression of HIF-1α is assumed to promote malignant transformation and tumor progression and thus might reduce the accessibility to radiotherapy.
Daniela Schilling, Christine Bayer, Wei Li, Michael Molls, Peter Vaupel and Gabriele Multhoff
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Radiation and dual checkpoint blockade activate non-redundant immune mechanisms in cancer.
Immune checkpoint inhibitors1 result in impressive clinical responses2, 3, 4, 5, but optimal results will require combination with each other6 and other therapies. This raises fundamental questions about mechanisms of non-redundancy and resistance. Here we report major tumour regressions in a subset of patients with metastatic melanoma treated with an anti-CTLA4 antibody (anti-CTLA4) and radiation, and reproduced this effect in mouse models. Although combined treatment improved responses in irradiated and unirradiated tumours, resistance was common. Unbiased analyses of mice revealed that resistance was due to upregulation of PD-L1 on melanoma cells and associated with T-cell exhaustion. Accordingly, optimal response in melanoma and other cancer types requires radiation, anti-CTLA4 and anti-PD-L1/PD-1. Anti-CTLA4 predominantly inhibits T-regulatory cells (Treg cells), thereby increasing the CD8 T-cell to Treg (CD8/Treg) ratio. Radiation enhances the diversity of the T-cell receptor (TCR) repertoire of intratumoral T cells. Together, anti-CTLA4 promotes expansion of T cells, while radiation shapes the TCR repertoire of the expanded peripheral clones. Addition of PD-L1 blockade reverses T-cell exhaustion to mitigate depression in the CD8/Treg ratio and further encourages oligoclonal T-cell expansion. Similarly to results from mice, patients on our clinical trial with melanoma showing high PD-L1 did not respond to radiation plus anti-CTLA4, demonstrated persistent T-cell exhaustion, and rapidly progressed. Thus, PD-L1 on melanoma cells allows tumours to escape anti-CTLA4-based therapy, and the combination of radiation, anti-CTLA4 and anti-PD-L1 promotes response and immunity through distinct mechanisms.
Christina Twyman-Saint Victor, Andrew J. Rech, Amit Maity, Ramesh Rengan, Kristen E. Pauken, Erietta Stelekati, Joseph L. Benci, Bihui Xu, Hannah Dada, Pamela M. Odorizzi, Ramin S. Herati, Kathleen D. Mansfield, Dana Patsch, Ravi K. Amaravadi, Lynn M. Schuchter, Hemant Ishwaran, Rosemarie Mick, Daniel A. Pryma, Xiaowei Xu, Michael D. Feldman, Tara C. Gangadhar, Stephen M. Hahn, E. John Wherry, Robert H. Vonderheide & Andy J. Minn
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Delta-Like Ligand 4–Notch Blockade and Tumor Radiation Response.
The microenvironment plays an important role in regulating tumor response to radiotherapy. Ionizing radiation can disrupt tumor vasculature, and Notch pathway inhibition can interfere with functional angiogenesis. We explored the potential cooperativity between Notch inhibition and ionizing radiation in delaying tumor growth.
Stanley K Liu, Saif A S Bham, Emmanouil Fokas, John Beech, Jaehong Im, Song Cho, Adrian L Harris and Ruth J Muschel
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Acid Sphingomyelinase Is Required for Protection of Effector Memory T Cells against Glucocorticoid-Induced Cell Death.
The activity of acid sphingomyelinase (aSMase) was previously reported to be involved in glucocorticoid-induced cell death (GICD) of T lymphocytes. This mechanism in turn is believed to contribute to the therapeutic efficacy of glucocorticoids (GCs) in the treatment of inflammatory diseases. In this study, we reassessed the role of aSMase in GICD by using aSMase knockout mice. The absence of aSMase largely abolished the partial protection that effector memory CD4+ T cells in wild-type mice possess against GICD. Reduced IL-2 secretion by aSMase-deficient CD4+ T cells suggested that a lack of this important survival factor might be the cause of these cells’ enhanced susceptibility to GICD. Indeed, addition of IL-2 restored the protection against GICD, whereas neutralization of IL-2 abrogated the otherwise protective effect seen in wild-type effector memory CD4+ T cells. The therapeutic implications of the altered sensitivity of aSMase-deficient T cells to GICD were assessed in models of inflammatory disorders; namely, experimental autoimmune encephalomyelitis and acute graft-versus-host disease. Surprisingly, GC treatment was equally efficient in both models in terms of ameliorating the diseases, regardless of the genotype of the T cells. Thus, our data reveal a hitherto unrecognized contribution of aSMase to the sensitivity of effector memory CD4+ T cells to GICD and call into question the traditionally attributed importance of GICD of T cells to the treatment of inflammatory diseases by GCs.
Denise Tischner, Jennifer Theiss, Anna Karabinskaya, Jens van den Brandt, Sybille D Reichardt, Ulrike Karow, Marco J Herold, Fred Lühder, Olaf Utermöhlen, and Holger M Reichardt
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Caspase-2 is required for DNA damage-induced expression of the CDK inhibitor p21WAF1/CIP1. Available from:
Although caspase-2 represents the most conserved caspase across species and was the second caspase identified, its precise function remains enigmatic. In several cell types we show that knockdown of caspase-2 specifically impaired DNA damage-induced p21 expression, whereas overexpression of a caspase-2 mutant increased p21 levels. Caspase-2 did not influence p21 mRNA transcription; moreover, various inhibitors targeting proteasomal or non-proteasomal proteases, including caspases, could not restore p21 protein levels following knockdown of caspase-2. As, however, silencing of caspase-2 impaired exogenous expression of p21 constructs containing 3′-UTR sequences, our results strongly indicate that caspase-2 regulates p21 expression at the translational level. Intriguingly, unlike depletion of caspase-2, which prevented p21 expression and thereby reverted the γ-IR-induced senescent phenotype of wild-type HCT116 colon carcinoma cells into apoptosis, knockdown of none of the caspase-2-interacting components RAIDD, RIP or DNA-PKcs was able to mimic these processes. Together, our data suggest that this novel role of caspase-2 as a translational regulator of p21 expression occurs not only independently of its enzymatic activity but also does not require known caspase-2-activating platforms.
Academic paper: Caspase-2 is required for DNA damage-induced expression of the CDK inhibitor p21WAF1/CIP1. Available from: https://www.researchgate.net/publication/51034476_Caspase-2_is_required_for_DNA_damage-induced_expression_of_the_CDK_inhibitor_p21WAF1CIP1 [accessed May 2, 2017].
D Sohn, W Budach and R U Jänicke
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Impact of oncogenic K-RAS on YB-1 phosphorylation induced by ionizing radiation.
Expression of Y-box binding protein-1 (YB-1) is associated with tumor progression and drug resistance. Phosphorylation of YB-1 at serine residue 102 (S102) in response to growth factors is required for its transcriptional activity and is thought to be regulated by cytoplasmic signaling phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathways. These pathways can be activated by growth factors and by exposure to ionizing radiation (IR). So far, however, no studies have been conducted on IR-induced YB-1 phosphorylation.
Mahmoud Toulany, Tim-Andre Schickfluß, Wolfgang Eicheler, Rainer Kehlbach, Birgit Schittek and H Peter Rodemann
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Irradiation-Induced Up-Regulation of HLA-E on Macrovascular Endothelial Cells Confers Protection against Killing by Activated Natural Killer Cells.
Apart from the platelet/endothelial cell adhesion molecule 1 (PECAM-1, CD31), endoglin (CD105) and a positive factor VIII-related antigen staining, human primary and immortalized macro- and microvascular endothelial cells (ECs) differ in their cell surface expression of activating and inhibitory ligands for natural killer (NK) cells. Here we comparatively study the effects of irradiation on the phenotype of ECs and their interaction with resting and activated NK cells.
Isabelle Riederer, Wolfgang Sievert, Günther Eissner, Michael Molls and Gabriele Multhoff
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