Immunomodulatory effects of targeted radionuclide therapy.

It is now clear that conventional radiation therapy can reinstate cell death immunogenicity. Recent preclinical data indicate that targeted radionuclide therapy that irradiate tumors at continuous low dose rate also can elicit immunostimulatory effects and represents a promising strategy to circumvent immune checkpoint inhibitor resistance. In this perspective, we discuss the accumulating preclinical and clinical data suggesting that activation of the immune system through the cGAS-STING axis and the release of extracellular vesicles by irradiated cells, participate to this antitumor immunity. This should need to be considered for adapting clinical practices to state of the art of the radiobiology and to increase targeted radionuclide therapy effectiveness.

Near-Edge X-ray Absorption Fine Structure Investigation of the Quasi-One-Dimensional Organic Conductor (TMTSF)2PF6.

We present high-resolution near-edge X-ray absorption fine structure (NEXAFS) measurements at the P L2/3 edges, F K edge, C K edge, and Se M2/3 edges of the quasi-one-dimensional (1D) conductor and superconductor (TMTSF)2PF6. NEXAFS allows probing the donor and acceptor moieties separately; spectra were recorded between room temperature (RT) and 30 K at normal incidence. Spectra taken around RT were also studied as a function of the angle (θ) between the electric field of the X-ray beam and the 1D conducting direction. In contrast with a previous study of the S L2/3-edges spectra in (TMTTF)2AsF6, the Se M2/3 edges of (TMTSF)2PF6 do not exhibit a well-resolved spectrum. Surprisingly, the C K-edge spectra contain three well-defined peaks exhibiting strong and nontrivial θ and temperature dependence. The nature of these peaks as well as those of the F K-edge spectra could be rationalized on the basis of first-principles DFT calculations. Despite the structural similarity, the NEXAFS spectra of (TMTSF)2PF6 and (TMTTF)2AsF6 exhibit important differences. In contrast with the case of (TMTTF)2AsF6, the F K-edge spectra of (TMTSF)2PF6 do not change with temperature despite stronger donor-anion interactions. All these features reveal subtle differences in the electronic structure of the TMTSF and TMTTF families of salts.

Realistic multi-cellular dosimetry for 177Lu-labelled antibodies: model and application.

Current preclinical dosimetric models often fail to take account of the complex nature of absorbed dose distribution typical of in vitro clonogenic experiments in targeted radionuclide therapy. For this reason, clonogenic survival is often expressed as a function of added activity rather than the absorbed dose delivered to cells/cell nuclei. We designed a multi-cellular dosimetry model that takes into account the realistic distributions of cells in the Petri dish, for the establishment of survival curves as a function of the absorbed dose. General-purpose software tools were used for the generation of realistic, randomised 3D cell culture geometries based on experimentally determined parameters (cell size, cell density, cluster density, average cluster size, cell cumulated activity). A mixture of Monte Carlo and analytical approaches was implemented in order to achieve as accurate as possible results while reducing calculation time. The model was here applied to clonogenic survival experiments carried out to compare the efficacy of Betalutin®, a novel 177Lu-labelled antibody radionuclide conjugate for the treatment of non-Hodgkin lymphoma, to that of 177Lu-labelled CD20-specific (rituximab) and non-specific antibodies (Erbitux) on lymphocyte B cells. The 3D cellular model developed allowed a better understanding of the radiative and non-radiative processes associated with cellular death. Our approach is generic and can also be applied to other radiopharmaceuticals and cell distributions.

Donor-anion interactions at the charge localization and charge ordering transitions of (TMTTF)2AsF6 probed by NEXAFS.

High-resolution near-edge X-ray absorption fine structure (NEXAFS) measurements at the As M-edge, F K-edge and S L-edge of the Fabre salt (TMTTF)2AsF6 were performed from room temperature (RT) to 90 K, allowing to reach the charge localization regime below Tρ ≈ 230 K and to cross the charge ordering (CO) transition at TCO ≈ 102 K. The F K-edge and S L-edge spectra exhibit several transitions which have been indexed on the basis of first-principles DFT calculations. Upon cooling from RT significant energy shifts up to +0.8 eV and -0.4 eV were observed in transitions exhibited by the F 1s and S 2p spectra respectively, while the As 3p doublet does not show a significant shift. Opposite energy shifts found in the F 1s and S 2p spectra reflect substantial thermal changes in the electronic environment of F atoms of the anion and S atoms of TMTTF. The changes found around the charge localization crossover suggest an increase of the participation of the S d orbitals in the empty states of TMTTF as well as an increase of the strength of donoranion interactions. A new F 1s pre-edge signal detected upon entry into the CO phase is a clear fingerprint of the symmetry breaking occurring at TCO. We propose that this new transition is caused by a substantial mixing between the HOMO of the AsF6(-) anion and the unoccupied part of the TMTTF HOMO conduction band. Analysis of the whole spectra also suggests that the loss of the inversion symmetry associated with the CO is due to an anion displacement increasing the strength of SF interactions. Our data show unambiguously that anions are not, as previously assumed, innocent spectators during the electronic modifications experienced by the Fabre salts upon cooling. In particular the interpretation of the spectra pointing out a thermally dependent mixing of anion wave functions with those of the TMTTF chains demonstrates for the first time the importance of anion-donor interactions.

²°¹Tl⁺-labelled Prussian blue nanoparticles as contrast agents for SPECT scintigraphy.

Prussian blue (PB) and its analogues on the nanometric scale are exciting nano-objects that combine the advantages of molecular-based materials and nanochemistry. Herein, we demonstrate that ultra-small PB nanoparticles of 2-3 nm can be easily labelled with radioactive (201)Tl(+) to obtain new nanoprobes as radiotracers for 201-thallium-based imaging.

Place of (18)F-FDG-PET with computed tomography in the diagnostic algorithm of patients with fever of unknown origin.

There is evidence for the interest of (18)F-fluoro-deoxyglucose positron emission tomography with computed tomography ((18)F-FDG-PET/CT) in fever of unknown origin (FUO) clinical investigation. However, little and conflicting data exist about its place in the investigation procedure. The aim of this work was to evaluate the clinical value of (18)F-FDG-PET/CT in patients with FUO and identify patients who need early (18)F-FDG-PET/CT rather than a last-resort procedure. We performed a 2-year retrospective cohort study at the Nîmes University Hospital, France. A total of 79 patients (36 men, 43 women, mean age 54.0 ± 16.2 years) with FUO underwent (18)F-FDG-PET/CT. A final diagnosis was established in 61 (77.2 %) cases. Aetiologies of FUO were determined using (18)F-FDG-PET/CT findings in 45 (73.8 % of patients with diagnosis) cases. The sensibility and specificity value were 98 % and 87 %, respectively. The presence of adenopathy, low haemoglobin and increased C-reactive protein (CRP) were predictors of high-yield (18)F-FDG-PET/CT. (18)F-FDG-PET/CT may help to detect most causes of FUO. The predictors of high-yield (18)F-FDG-PET/CT found in this study can help identify patients likely to benefit from specific and early imaging techniques.

Inhomogeneous superconductivity in organic conductors: the role of disorder and magnetic field.

Several experimental studies have shown the presence of spatially inhomogeneous phase coexistence of superconducting and non-superconducting domains in low dimensional organic superconductors. The superconducting properties of these systems are found to be strongly dependent on the amount of disorder introduced in the sample regardless of its origin. The suppression of the superconducting transition temperature T(c) shows a clear discrepancy with the result expected from the Abrikosov-Gor'kov law giving the behavior of T(c) with impurities. On the basis of the time dependent Ginzburg-Landau theory, we derive a model to account for this striking feature of T(c) in organic superconductors for different types of disorder by considering the segregated texture of the system. We show that the calculated T(c) quantitatively agrees with experiments. We also focus on the effect of superconducting fluctuations on the upper critical fields H(c2) of layered superconductors showing slab structure where superconducting domains are sandwiched by non-superconducting regions. We found that H(c2) may be strongly enhanced by such fluctuations.

Ground state of the quasi-1D compound BaVS3 resolved by resonant magnetic x-ray scattering.

Resonant magnetic x-ray scattering near the vanadium L2,3-absorption edges has been used to investigate the low temperature magnetic structure of high quality BaVS3 single crystals. Below T(N)=31 K, the strong resonance revealed a triple-incommensurate magnetic ordering at the wave vector (0.226   0.226   ξ) in hexagonal notation, with ξ=0.033. The azimuthal-angle dependence of the scattering signal and time-dependent density functional theory simulations indicate an antiferromagnetic order within the ab plane with the spins polarized along a in the monoclinic structure.

Evidence for lattice effects at the charge-ordering transition in (TMTTF)2X.

High-resolution thermal expansion measurements have been performed for exploring the mysterious "structureless transition" in (TMTTF)2X (X=PF(6) and AsF6), where charge ordering at T(CO) coincides with the onset of ferroelectric order. Particularly distinct lattice effects are found at T(CO) in the uniaxial expansivity along the interstack c direction. We propose a scheme involving a charge modulation along the TMTTF stacks and its coupling to displacements of the counteranions X-. These anion shifts, which lift the inversion symmetry enabling ferroelectric order to develop, determine the 3D charge pattern without ambiguity. Evidence is found for another anomaly for both materials at T(int) approximately 0.6T(CO) indicative of a phase transition related to the charge ordering.

PCC-FISH in skin fibroblasts for local dose assessment: biodosimetric analysis of a victim of the Georgian radiological accident.

We propose a new method of biodosimetry that could be applied in cases of localized irradiation. The approach is based on excess chromosome segments determination by the PCC-FISH technique in fibroblasts isolated from skin biopsy. Typically, 0 to 10 Gy ex vivo gamma-irradiated human skin biopsies were dissociated and fibroblasts were isolated and grown for several days. Cells next underwent PCC-FISH painting of whole chromosome 4, and the number of excess chromosome segments per metaphase was determined. An ex vivo reference curve correlating the number of excess chromosome segments per metaphase to the radiation dose was established and used to assess the dose delivered to the skin of one of the victims of the radiological accident that occurred at Lia in Georgia in December 2001. Specifically, the victim suffering from moist desquamation underwent skin excision in Hospital Percy (France). Measurement of excess chromosome segments per metaphase was done in fibroblasts isolated and grown from removed wounded skin and subsequent conversion to radiation doses was performed. The radiation dose map obtained was shown to be in accordance with clinical data and physical dosimetry as well as with conventional biodosimetry. These results demonstrated that PCC-FISH painting applied to skin fibroblasts may be a suitable technique for dose estimation. To assess its worth, this approach needs to be extended to future accidents involving localized radiation exposure.

The cell membrane as a biosensor of oxidative stress induced by radiation exposure: a multiparameter investigation.

The role of biological membranes as a target in biological radiation damage remains unclear. The present study investigates how the biochemical and biophysical properties of a simple biological model, i.e. human erythrocyte membranes, are altered after exposure to relatively low doses of (60)Co gamma rays. Lipid peroxidation increased in the hours after radiation exposure, based on measurements of MDA and on the lipid peroxidation index after parinaric acid incorporation. Protein carbonyl content also increased rapidly after radiation exposure. An imbalance between the radiation-mediated oxidative damages and the antioxidant capacity of the erythrocytes was observed in the hours after radiation exposure. Antioxidant enzyme activities, mainly catalase and glutathione peroxidase, were found to decrease after irradiation. The development of a radiation-induced oxidative stress probably explains the reorganization of the fatty acid pattern 72 h after radiation exposure. The phosphatidylethanolamine (PE) fatty acids of the (n-3) and (n-6) series decreased, while the PE saturated fatty acid content increased. All these modifications may be involved in the variation of the biophysical properties of the membranes that we noted after radiation exposure. Specifically, we observed that the lipid compartment of the membrane became more fluid while the lipid-protein membrane interface became more rigid. Taken together, these findings reinforce our understanding that the cell membrane is a significant biological target of radiation. Thus the role of the biological membrane in the expression and course of cell damage after radiation exposure must be considered.

Formation of modified DNA bases in cells exposed either to gamma radiation or to high-LET particles.

The aim of the present study was to measure the formation of eight base modifications in the DNA of cells exposed to either low-LET ((60)Co gamma rays) or high-LET ((12)C(6+) particles) radiation. For this purpose, a recently optimized HPLC-MS/MS method was used subsequent to DNA extraction and hydrolysis. The background level of the measured modified bases and nucleosides was shown to vary between 0.2 and 2 lesions/10(6) bases. Interestingly, thymidine glycols constitute the main radiation-induced base modifications, with an overall yield of 0.097 and 0.062 lesion/10(6) bases per gray for gamma rays and carbon heavy ions, respectively. Both types of radiations generate four other major degradation products, in the following order of decreasing importance: FapyGua > 5-HmdUrd > 5-FordUrd > 8-oxodGuo. The yields of formation of FapyAde and 8-oxoAde are one order of magnitude lower than those of the related guanine modifications, whereas the radiation-induced generation of 5-OHdUrd was below the limit of detection of the assay. The efficiency for both types of radiation to generate base damage in cellular DNA is low because the highest yield per gray was 0.097 thymine glycols per 10(6) DNA bases. As a striking observation, the yield of formation of the measured DNA lesions was found to be, on average, twofold lower after exposure to high-LET radiation ((12)C(6+)) than after exposure to low-LET gamma radiation. These studies show that the HPLC-MS/MS assay provides an accurate, reliable and sensitive method for measuring cellular DNA base damage.

Ab initio fermi surface calculation for charge-density wave instability in transition metal oxide bronzes.

The electronic structure of the charge density wave (CDW) bronze (PO2)(4)(WO3)(2m), m = 4, is determined using ab initio density functional theory. The calculation shows that the Fermi surface (FS) consists in the superposition of three one-dimensional FS's associated with three types of chains. The q dependence of the electronic response function calculated from the electronic structure quantitatively accounts for the anisotropy of the fluctuations probed by x-ray diffuse scattering. The results validate the hidden nesting mechanism proposed for the CDW transitions in this series of bronzes.

General aspects of the cellular response to low- and high-LET radiation.

Radiobiological studies have shown for some time that the effects of ionising radiation on cells are mainly explained by modification of the DNA. Numerous studies over the past 50 years have accumulated clear evidence of the cause-effect relationship between damage to DNA and the cytotoxic and mutagenic effects of ionising radiation. However, the path from irradiation of the cells to the induction of biological effects comprises several complex steps. The first step involves interactions between the radiation and the cellular environment. These consist of physical and chemical reactions which produce ions, excited molecules and radical species. Excitations and ionisations are complete in about 10(-15) s, and are followed by a chemical thermal equilibrium of the species produced within 10(-12) s. These species then diffuse from their site of production and provoke alterations to a variety of cellular components. This damage is detected by cellular surveillance systems, which in turn activate signalling cascades, gene transcription and enzyme recruitment, which participate in the cellular response. In most cases, cell cycle arrest occurs, allowing, according to the biological relevance of the DNA damage, either a process of DNA repair or programmed cell death (apoptosis). The accuracy of the DNA repair which is performed depends on the complexity of the DNA lesion and on the DNA repair machinery fidelity itself. Improper DNA repair can lead to mutation, chromosome aberration, genetic instability, oncogenic transformation and, ultimately, cell death.

Modulation of exogenous and endogenous levels of thioredoxin in human skin fibroblasts prevents DNA damaging effect of ultraviolet A radiation.

Thioredoxin (Trx) plays important biological roles both intra- and extracellularly via thiol redox control. We have previously demonstrated that Trx exhibited protective effects against UVA cytotoxicity in human skin fibroblasts. As an extension of the latter investigation, the present work is aimed at assessing ability of Trx to maintain genomic integrity in human skin fibroblasts upon exposure to UVA radiation. Indeed, UVA (320--380 nm) is mutagenic and induces genomic damage to skin cells. The alkaline comet assay was used in association with DNA repair enzyme including formamido pyrimidine glycosylase (Fpg) and endonuclease III (endo III) to estimate the amount of modified bases together with the level of strand breaks and alkali-labile sites. The HPLC-EC assay was applied to assess 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) levels and to permit the calibration of comet assay as previously described. We reported that overexpression of human Trx (transient transfection) as well as exogenous human recombinant Trx added to the culture medium, decreased the level of DNA damage in UVA irradiated cells. Interestingly, transfection appeared to prevent UVA-induced 8-oxodGuo (3.06 au per Joules.cm(-2) compared to 4.94 au per Joules.cm(-2) for nontransfected cells). Moreover, Trx accumulates into nuclei in transfected cells. This finding supports the notion that Trx is important for the maintenance of the integrity of genetic information. This work demonstrated that under conditions of UVA oxidative stress, Trx prevented the UVA-induced DNA damage.

High-performance liquid chromatography--tandem mass spectrometry measurement of radiation-induced base damage to isolated and cellular DNA.

A method involving high-performance liquid chromatography (HPLC) separation associated with tandem mass spectrometry (MS/MS) detection in the multiple-reaction monitoring mode was set up for the assessment of radiation-induced degradation products of DNA bases. This sensitive and specific assay is aimed at assessing six oxidized 2'-deoxyribonucleosides and two modified purine bases within both isolated and cellular DNA. For this purpose, stable isotopically labeled internal standards were prepared and used for isotope dilution mass spectrometry measurements. The latter method was validated through a comparison with two other assays, including HPLC associated with electrochemical detection and gas chromatography coupled to mass spectrometry. Using the specific and sensitive HPLC-MS/MS approach, 5,6-dihydroxy-5,6-dihydrothymidine, 5-hydroxy-2'-deoxyuridine, 5-(hydroxymethyl)-2'-deoxyuridine, 5-formyl-2'-deoxyuridine, 8-oxo-7,8-dihydro-2'-deoxyadenosine, 8-oxo-7,8-dihydro-2'-deoxyguanosine, 4, 6-diamino-5-formamidopyrimidine, and 2, 6-diamino-4-hydroxy-5-formamidopyrimidine were quantified within both isolated and cellular DNA upon exposure to gamma-radiation.

DNA damage induced in cells by gamma and UVA radiation as measured by HPLC/GC-MS and HPLC-EC and Comet assay.

The aim of the work was to measure DNA damage induced within tumoral human monocytes by gamma rays, UVA radiation, and exogenous photosensitizers. The accurate HPLC-EC assay was used to determine the level of 8-oxodGuo. The formation of FapyGua and FapyAde was monitored by HPLC/GC-MS analyses after formic acid hydrolysis at room temperature. For this purpose, cells were exposed to relatively high doses of gamma rays and UVA radiation. The extent of formation of FapyGua in the DNA of cells exposed to gamma rays was estimated to be more than 2-fold higher than that of 8-oxodGuo, i.e., about 0. 027 lesion per 10(6) bases per Gy. The yield of FapyAde was estimated to be 1 order of magnitude lower. The latter results were used to calibrate the alkaline comet assay associated with DNA N-glycosylases. The latter approach allowed the determination of the background level (0.11-0.16 Fpg-sensitive site/10(6) bases) and the yields of strand breaks and DNA base damage upon low irradiation doses. Insights into the mechanism of radiation-induced DNA damage were gained from these measurements. A major involvement of (1)O(2) with respect to hydroxyl radicals and type I photosensitization was thus observed within cells exposed to UVA radiation.

Hydroxyl radicals and DNA base damage.

Modified purine and pyrimidine bases constitute one of the major classes of hydroxyl-radical-mediated DNA damage together with oligonucleotide strand breaks, DNA-protein cross-links and abasic sites. A comprehensive survey of the main available data on both structural and mechanistic aspects of.OH-induced decomposition pathways of both purine and pyrimidine bases of isolated DNA and model compounds is presented. In this respect, detailed information is provided on both thymine and guanine whereas data are not as complete for adenine and cytosine. The second part of the overview is dedicated to the formation of.OH-induced base lesions within cellular DNA and in vivo situations. Before addressing this major point, the main available methods aimed at singling out.OH-mediated base modifications are critically reviewed. Unfortunately, it is clear that the bulk of the chemical and biochemical assays with the exception of the high performance liquid chromatographic-electrochemical detection (HPLC/ECD) method have suffered from major drawbacks. This explains why there are only a few available accurate data concerning both the qualitative and quantitative aspects of the.OH-induced formation of base damage within cellular DNA. Therefore, major efforts should be devoted to the reassessment of the level of oxidative base damage in cellular DNA using appropriate assays including suitable conditions of DNA extraction.