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Showing papers in "International Journal of Radiation Biology in 2000"


Journal ArticleDOI
TL;DR: Clinical data suggesting that cancer metastasis may be induced by the microenvironment of the primary tumour is presented and possible mechanisms of microenvironment-induced metastasis are discussed, based on a critical review of relevant data from studies of experimental tumours and cells in culture.
Abstract: Purpose : To present and evaluate clinical data suggesting that cancer metastasis may be induced by the microenvironment of the primary tumour and to discuss possible mechanisms of microenvironment-induced metastasis, based on a critical review of relevant data from studies of experimental tumours and cells in culture. Conclusions : Low oxygen tension in the primary tumour is associated with metastasis in soft tissue sarcoma, cervix carcinoma and carcinoma of the head and neck. Multiple mechanisms may be involved in hypoxia-induced metastasis. Thus, hypoxia followed by reoxygenation may induce point mutations and DNA strand breakage leading to deletions, amplifications and genomic instability. Hypoxia may also provide a physiological pressure in tumours selecting for metastatic cell phenotypes. Moreover, hypoxia may induce a temporary increase in the expression of gene products involved in the metastatic cascade, either through gene amplifications or through normal physiological processes by activating ox...

343 citations


Journal ArticleDOI
TL;DR: An increased biologically effective dose can be produced by gold microspheres suspended in cell culture or distributed in tumour tissue exposed to kilovoltage photon beams, with the increasing use of interstitial brachytherapy with isotopes that produce low-energy photons.
Abstract: Purpose : To investigate dose enhancement and radiosensitization associated with electrons produced and scattered from gold particles suspended in cells in vitro and with tumour cells growing in vivo irradiated with low-energy photons. Materials and methods : CHO-K1, EMT-6 and DU-145 cells were irradiated with kilovoltage X-ray and Cs-137 beams in slowly stirred suspensions in the presence of various concentrations of gold particles (1.5-3.0 μ m); cell survival was measured by clonogenic assay. Gold particles were injected directly into EMT-6 tumours growing in scid mice prior to their irradiation. Tumour cell killing was assayed by an in vivo-in vitro technique. Results : Dose enhancement was confirmed by both Fricke dosimetry and cell killing for 100, 140, 200 and 240kVp X-rays, but not for Cs-137 γ-rays. For the chemical dosimeter, a dose enhancement (DMF) of 1.42 was measured for 1% gold particle solutions irradiated with 200 kVp X-rays. When rodent and human cells were irradiated in the presence of 1...

283 citations


Journal ArticleDOI
TL;DR: ACE inhibitors and one AII type 1 receptor blocker were effective in protecting lungs from radiation-induced pneumonitis and the development of lung fibrosis in two models of rat radiation injury.
Abstract: Purpose : This report summarizes our experiences on the protective effect of angiotensin-converting enzyme (ACE) inhibitors, especially captopril and an angiotensin II type 1 receptor blocker on radiation-induced pulmonary injury. Method : In the first series of experiments, adult male Sprague Dawley rats were given a single dose of either 20 or 30 Gy of gamma rays to a 35 cm 2 right hemithorax port, whilst shielding the left, contralateral, lung. Perfusion scans and autopsies were performed at intervals up to 12 months post-radiation. Three different ACE inhibitors, penicillamine and pentoxifylline were given as radiation protectors and their activity compared. A model of irradiation for total bone marrow transplant (BMT) was used for the second group of experiments. Male WAC/Rij/MCW rats received total-body irradiation and a regimen of cyclophosphamide (CTX) in preparation for bone marrow transplant. The modifiers were two ACE inhibitors, captopril and enalapril, and L-158,809, an angiotensin II (A II) ...

206 citations


Journal ArticleDOI
TL;DR: This study shows that purified COX is a specific target of He-Ne laser light; therefore, COX may be considered to be a mitochondrial photo-acceptor.
Abstract: Purpose : In order to gain some insight into the mechanism of interaction between Helium-Neon (He-Ne) laser light and mitochondrial cytochromes, the sensitivity of cytochrome electron transfer activity to He-Ne laser was tested. Materials and methods : Irradiation of solutions containing either purified cytochromes or dissolved rat liver mitochondria was carried out (wavelength 632.8nm, fluence rate 10 m W cm -2, fluence 2 J cm -2) ; the irradiation conditions were the ones able to affect cytochrome c oxidase (COX) activity in mitochondria (Pastore et al., 1994). Results : Cytochrome c oxidation catalysed by COX was affected by He-Ne laser irradiation of the purified enzyme. This result was obtained from measurements of the pseudo-first-order kinetic constant and from determinations of the turnover number of the enzyme, performed at different cytochrome c/COX ratios. Consistently, the kinetic parameters of COX changed. On the contrary, no alteration in the rate of electron transfer catalysed by either cyt...

187 citations


Journal ArticleDOI
TL;DR: Transmissible-type complexes were observed, specifically insertions, in both second and third division cells after exposure to high-LET alpha-particles in vitro, and the usefulness of insertions as biomarkers of past exposure to environmentally relevant doses of high-let alpha- particles is supported.
Abstract: Purpose: To determine the induction and transmission, to second and third division cells, of complex chromosome aberrations in peripheral blood lymphocytes after exposure to high-LET alpha-particles in vitro. Materials and methods: Separated peripheral blood lymphocytes collected from four healthy donors were irradiated in vitro with either high-LET alpha-particles (121keV/mum; 0.5Gy) or low-LET X-rays (250kV constant potential; 3Gy). Cells were harvested in first, second and third division post-irradiation and chromosome aberrations observed at each cell division were analysed by combining the techniques of FISH and DAPI/Hoechst 33258 harlequin staining. Whole chromosome probes were used for chromosomes 1, 2 and 5, together with a pan-centromeric probe and the resulting chromosome 'painting' patterns were classified according to the Savage and Simpson (S & S) scheme (Savage and Simpson 1994a, Savage and Tucker 1996). Results: A greater proportion of complex chromosome aberrations was observed, defined as...

150 citations


Journal ArticleDOI
TL;DR: The results suggest that the exposure to EMF modulates the responses of EEG oscillatory activity approximately 8 Hz specifically during cognitive processes.
Abstract: Purpose : To examine the effects of electromagnetic fields (EMF) emitted by cellular phones on the event-related desynchronization/synchronization (ERD/ERS) responses of the 4-6, 6-8, 8-10 and 10-12 Hz EEG frequency bands during cognitive processing. Materials and methods : Twenty-four subjects performed a visual sequential letter task (n -back task) with three different working memory load conditions: zero, one and two items. All subjects performed the memory task both with and without exposure to a digital 902MHz EMF in counterbalanced order. Results : The presence of EMF altered the ERD/ERS responses in the 6-8 and 8-10Hz frequency bands but only when examined as a function of memory load and depending also on whether the presented stimulus was a target or not. Conclusions : The results suggest that the exposure to EMF modulates the responses of EEG oscillatory activity ~8Hz specifically during cognitive processes.

127 citations


Journal ArticleDOI
TL;DR: A significant non-random contribution to the number of dsb after irradiation with high-LET was confirmed by detailed fragment analysis using pulsed-field gel electrophoresis, and the LET had a strong influence on the initial DNA fragment distribution, and hence also on the induction yields measured.
Abstract: Purpose : To investigate DNA fragmentation as a function of linear energy transfer (LET) after exposure to accelerated ions in the LET range 40–225 keV/mum. Materials and methods : Fragmentation patterns of double-stranded DNA in the range 5 kilobasepairs (kbp) to 5.7 megabasepairs (Mbp) were analysed after irradiation of low-passage GM 5758 normal human fibroblast cells with 60 Co-photons, helium ions at 40 keV/mum and high-LET nitrogen ions between 80 and 225 keV/mum. Two separate pulsed-field gel electrophoresis protocols were used, optimized for separation of 1–6 Mbp and 5 kbp to 1.5 Mbp fragments. Results : An increased probability of formation of short and medium-sized DNA fragments was revealed following high-LET irradiation. The DNA double-strand break (dsb) induction yields were, respectively, 5.8 and 6.9–8.8 x 10 -9 dsb bp -1 Gy -1 for 60 Co-photons and ions. The ion yields were some 80–110% higher than those calculated according to a conventional approach, disregarding the fragment distribution...

119 citations


Journal ArticleDOI
TL;DR: RBE for inactivation with high-LET protons increased with the cellular radioresistance to gamma-rays, and a similar trend has been found in studies reported in the literature with He, C, N ions with LET in the range 20-125 keV/microm on human tumour cell lines.
Abstract: Purpose : To analyse the cell inactivation frequencies induced by low energy protons in human cells with different sensitivity to photon radiation. Materials and methods : Four human cell lines with various sensitivities to photon irradiation were used: the SCC25 and SQ20B derived from human epithelium tumours of the tongue and larynx, respectively, and the normal lines M/10, derived from human mammary epithelium, and HF19 derived from a lung fibroblast. The cells were irradiated with γ-rays and proton beams with linear energy transfer (LET) from 7 to 33keV/ μ m. Clonogenic survival was assessed. Results : Survival curves are reported for each cell line following irradiation with γ-rays and with various proton LETs. The surviving fraction after 2 Gy of γ-rays was 0.72 for SQ20B cells, and 0.28–0.35 for the other cell lines. The maximum LET proton effectiveness was generally greater than that of γ-rays. In particular there was a marked increase in beam effectiveness with increasing LET for the most resista...

111 citations


Journal ArticleDOI
TL;DR: The effects of weak magnetic fields (> approximately 1 mT) on chemical reactions involving free radicals, in the context of possible effects of environmental electromagnetic radiation on biological systems are demonstrated.
Abstract: Purpose : To demonstrate the effects of weak magnetic fields (> ˜ 1 mT) on chemical reactions involving free radicals, in the context of possible effects of environmental electromagnetic radiation on biological systems. Materials and methods : Transient absorption, flash photolysis experiments have been performed to study the kinetics and yields of radical reactions. The triplet state of benzophenone has been used as a convenient source of radical pairs, whose identity is largely immaterial to the investigation of the so-called Low Field Effect. Hydrogen abstraction from surfactant molecules in micelles yields a pair of neutral radicals, one large and one small, in a region of restricted translational and rotational motion. Results : In alkyl sulphate and sulphonate micelles a weak field increases the concentration of free radicals that escape from the micelle to an extent that depends on the structure, dynamics and volume of the space in which the radical pairs are confined. The effect (up to 10%) is typ...

107 citations


Journal ArticleDOI
TL;DR: Cell killing after irradiation or hydrogen peroxide appears to be due to dsb, whereas cells withstand large numbers of single-strand lesions and other types of non-DNA damage occurring at lower concentrations of hydrogen perox.
Abstract: Purpose: Free OH radicals are considered to be the common mediator of DNA damage after ionizing radiation and oxidative stress. In particular, double-strand breaks (dsb) have a major impact on cell killing after irradiation, while the mechanism of cell killing is less clear for oxidative injury. The latter not only affects DNA, but also equally other cell compartments, such as membranes and mitochondria, which may trigger cell death. This study intended to clarify the relationship between DNA damage induction, repair and cell inactivation for hydrogen peroxide and ionizing radiation. Materials and methods: Chinese hamster ovary (CHO) cells were treated with H 2 O 2 in serum-free medium in combination with/without X-irradiation. DNA damage was measured using the alkaline unwinding method or neutral constant-field gel electrophoresis. Cell survival was recorded using the colony-formation assay. Results: Hydrogen peroxide induced a large number of single-strand breaks (ssb>36000/cell) without impairing cell ...

107 citations


Journal ArticleDOI
TL;DR: The cdk1/cyclin-B activity levels during the G2 to M transition impair DNA repair processes and play a major role in the yield of chromatid breaks induced after G2-irradiation.
Abstract: Purpose : To test the hypothesis that deficient DNA repair as measured by increased G2 chromosomal radiosensitivity results from up-regulation of cdk1/cyclinB and cell cycle control mechanisms during the G2 to M transition. Materials and methods : A total of 185 cancer patients and 25 normal individuals were tested for G2 chromosomal radiosensitivity. The chromatid breaks were analysed in metaphase using the G2 assay or directly in G0 and G2 phase using premature chromosome condensation (PCC). The activity of cdk1/cyclinB, a key regulator of the G2 to M-phase transition, was measured by histone H1 kinase activity and correlated with the development of chromatid breaks after irradiation of cell lines in vitro. Results : Based on the G2 assay, cancer patients on average showed increased chromosomal radiosensitivity above controls. When the analysis was carried out directly in G0 or G2 lymphocytes using PCC, no differences in the induction of chromosomal damage and its repair were observed between G2 assay-s...

Journal ArticleDOI
TL;DR: The combination of chromosome painting and the detection of centromeres and telomeres enable unequivocal discrimination between incomplete and complete exchanges.
Abstract: Purpose : To discriminate precisely between radiation-induced complete and incomplete chromosome exchanges using chromosome painting together with the detection of the centromeres and telomeres in one FISH assay. Materials and methods : Human lymphocytes were exposed in vitro to X-rays at a dose of 4 Gy. Chromosome aberrations were analysed using the FISH technique in combination with a whole chromosome-specific DNA probe for chromosome 8, human pan-centromeric DNA and telomeric PNA probes. Results : The combined FISH assay has improved the resolution of detecting chromosomal exchanges in human lymphocytes. Results indicate that the frequency of observed incomplete exchange patterns was 21% when telomeric signals were ignored during the analysis. When the telomeric signals were included in the analysis a large proportion of apparently incomplete exchange patterns appeared complete and should be re-classified. The percentage of true incomplete exchanges was found to be less than 5%. Conclusion : The combin...

Journal ArticleDOI
TL;DR: Quantitative estimates of radiobiological characteristics of human lung are available for the pneumonitis phase where the fractionation sensitivity is in the same range as for most late-responding normal tissues, and for the later phase of lung fibrosis, the estimates are fewer and generally less precise.
Abstract: Purpose : To quantify the response of human lung to a course of fractionated radiotherapy based on a literature review of published clinical data. Materials and methods : Quantitative clinical radiobiology is concerned with the estimation of parameters that describe the clinical outcome of radiotherapy as a function of patient and treatment characteristics. Here, parameters describing the steepness of the dose–response curve, the response to a change in dose per fraction and to a change in overall treatment time for early and late lung injury are compiled based on published clinical studies. Results : Two phases of lung injury are seen, radiation pneumonitis and lung fibrosis. The first signs of early lung changes are seen almost immediately after irradiation. This reaction peaks after 5 to 6 months, and settles partially before 9–10 months. Around that time, the late changes become manifest and these are stable in most cases. There is an important distinction between lung injury and radiotherapy-related ...

Journal ArticleDOI
TL;DR: DNA fragment analysis detected LET-dependent differences in the amount of rejoining while the half-times were independent of LET, and the majority of dsb were rapidly rejoined even after high-LET irradiation.
Abstract: Purpose : To analyse the rejoining of DNA double-strand breaks (dsb) produced by high-linear energy transfer (LET) ions, with the specific focus on the influence, on the rejoining estimates, of the...

Journal ArticleDOI
TL;DR: The results indicate the important role of TGF-beta1 in triggering radiation-induced inhibition of clonogenic activity as well as terminal differentiation of rat lung fibroblasts and support the hypothesis that terminal differentiation is an essential cellular process in the development of radiation- induced fibrosis in the lung.
Abstract: Purpose : To study the influence of TGF-beta1 and TGF-beta-neutralizing antibodies on the clonogenic activity and terminal differentiation of rat lung fibroblasts following radiation exposure. Material and methods : Early passage rat lung fibroblasts were used in this study. Colony formation assays were applied to determine the radiation sensitivity as well as radiation-induced alterations in differentiation pattern. Based on a TGF-beta1-specific ELISA system, the amount of TGF-beta1 in the culture medium of sham-irradiated and irradiated cultures was determined. Results : Applying immediate (ip) and delayed plating (dp) procedures for cells irradiated in the subconfluent state, distinct differences in the radiation dose–response curves could be observed (SF2 ip 0.20 +/- 0.025 versus SF2 dp 0.51 +/- 0.0077). Upon irradiation with a single dose of 4 Gy the level of TGF-beta1 found in the culture medium increased by about 60%. Radiation-induced terminal differentiation of progenitor fibroblasts (MF) to post...

Journal ArticleDOI
TL;DR: Regional radiographic changes in CT-defined tissue density or SPECT- defined tissue perfusion are similar in patients with and without RT-induced pulmonary symptoms because these endpoints do not consider the volume of lung affected.
Abstract: Purpose : To assess the relationship between radiation (RT)induced pulmonary symptoms and subclinical changes in pulmonary functions tests (PFT) and radiographs. Materials and methods : A total of 184 patients irradiated between 1992 and 1998 were prospectively evaluated for RT-induced pulmonary symptoms, changes in computed tomography (CT) density, reductions in single photon emission CT (SPECT) perfusion, and changes in pulmonary functions tests (forced expiratory volume in 1s [FEV 1 ] and diffusion capacity to carbon monoxide [DLCO]). Comparisons between the evaluable patients with (N = 34) and without (N = 106) RT-induced pulmonary symptoms were made. Results : Within 6 months of RT, 80% of the RT-induced symptoms were noted. There was no association between the presence or absence of RT-induced pulmonary symptoms and the frequency of RT-induced radiographic changes (p = 0.53), or in the dose–response curve for RT-induced reductions in regional perfusion. Overall, RT-induced changes in SPECT images we...

Journal ArticleDOI
TL;DR: Findings indicate the importance of an intercellular signal transduction pathway initiated by nitric oxide in the cellular response to accelerated heavy ions in human glioblastoma A-172 and T98G cells.
Abstract: Purpose : To investigate whether nitric oxide excreted from cells irradiated with accelerated carbon-ion beams modulates cellular radiosensitivity against irradiation in human glioblastoma A-172 and T98G cells. Materials and methods : Western-blot analysis of inducible nitric oxide synthase, hsp72 and p53, the concentration assay of nitrite in medium and cell survival assay after irradiation with accelerated carbon-ion beams were performed. Results : The accumulation of inducible nitric oxide synthase was caused by accelerated carbon-ion beam irradiation of T98G cells but not of A-172 cells. The accumulation of hsp72 and p53 was observed in A-172 cells after exposure to the conditioned medium of the T98G cells irradiated with accelerated carbon-ion beams, and the accumulation was abolished by the addition of an inhibitor for inducible nitric oxide synthase to the medium. The radiosensitivity of A-172 cells was reduced in the conditioned medium of the T98G cells irradiated with accelerated carbonion beams ...

Journal ArticleDOI
TL;DR: The hypothesis that complex, less reparable DSB are induced in higher proportion by light ions with respect to gamma-rays and that, for the same ion, increasing LET leads to an increase in this proportion is supported.
Abstract: Purpose : To study the induction and the time-course of rejoining of DNA double strand breaks (DSB) in V79 cells irradiated with light ions with different linear energy transfer (LET). Materials and methods : V79 cells were irradiated in monolayer with monoenergetic proton, deuteron, helium-3 or helium-4 ion beams, each at two different energy values. Gamma rays were used as reference radiation. DSB have been measured by constant field gel electrophoresis (CFGE). Results : The initial yield depended little on the particle type and LET. The amount of DSB left unrejoined for up to 2 h incubation time could be roughly described by a decreasing exponential function with a final plateau, although more complex functions cannot be excluded. Radiation quality had little effect on the rejoining rate but affected the plateau. The amount of residual DSB after 2h was higher for densely than for sparsely ionizing radiation, and for the same particle was dependent on LET. The corresponding RBE ranged from 1.8 to 6.0. C...

Journal ArticleDOI
TL;DR: The lack of cell loss observed soon after irradiation indicates that the observed reduction in gland function was caused by a compromised functioning of the acini, and protection of gland morphology and function by sialogogues at later times must involve resistance of progenitor cells to radiation-induced cell death.
Abstract: Purpose : To understand early and late radiation-induced loss of function of the submandibular gland, changes in cell number were documented and correlated with data on gland function. Modulation of the radiation effect by sialogogues was used to investigate possible mechanisms of action. Materials and methods : Rats were irradiated with a single dose of 15 Gy of X-rays after pre-treatment with either saline, the muscarinic receptor agonists methacholine or pilocarpine, the adrenergic receptor agonist phenylephrine or methacholine plus phenylephrine. Before and 1-240 days after irradiation, submandibular saliva flow rate was measured. At the same time points and from comparable animals submandibular glands were carefully extirpated, weighed and prepared for light microscopic examination. Results : Soon after irradiation (<30 days) no significant loss of cells was observed, whereas the gland function was severely compromized. Sialogogue pre-treatment attenuated the radiation-induced loss of gland function....

Journal ArticleDOI
TL;DR: For irradiation followed by delayed plating only, non-repaired DNA double-strand breaks can be used to predict the cellular radiosensitivity.
Abstract: Purpose : The aim of this study was to test under which conditions non-repaired DNA double-strand breaks (dsb) could be used as an indicator of cellular radiosensitivity of normal human fibroblasts. Materials and methods : The experiments were performed with a primary normal skin fibroblast line (NFHH) derived from a healthy donor. Cells were X-irradiated either in exponential or confluent state with high (4 Gy/min) or low dose rate (0.04Gy/min) and either plated immediately or delayed after irradiation. The fraction of clonogenic cells was determined after doses up to 12 Gy using colony forming assay and the number of non-repaired dsb were measured 24h after X-irradiation with doses up to 180 Gy using constant-field gel electrophoresis. Results : Cellular radiosensitivity of NFHH cells was found to depend on all three conditions tested. In contrast, the number of non-repaired dsb was found to depend on dose rate and growth state only. There were, however, no differences for the plating conditions tested....

Journal ArticleDOI
TL;DR: The correlation between the increases in the SSB and DSB yields was unaffected by the scavenger concentration during irradiation, and the majority of DSB appear to be formed from two hydroxyl radical attacks.
Abstract: Purpose : To determine the increases in SSB and DSB yields after post gamma-irradiation incubation of plasmid DNA with the Escherichia coli base excision repair endonucleases formamidopyrimidineDNA N -glycosylase (FPG) and endonuclease III (endo III). Materials and methods : Aqueous solutions of plasmid DNA were irradiated with 137 Cs gamma-rays in the presence of 10 -4 -10 -1 mol dm -3 formate. After irradiation, aliquots were treated with FPG and/or endo III. SSB and DSB yields were then determined using gel electrophoresis. Results : Both SSB and DSB yields were found to increase after enzyme incubation, with the increase in the DSB yield being approximately equal to the square of the increase in the SSB yield. The correlation between the increases in the SSB and DSB yields was unaffected by the scavenger concentration during irradiation. Conclusion : Under the conditions used, the majority of DSB appear to be formed from two hydroxyl radical attacks.

Journal ArticleDOI
TL;DR: The kinetics and dose response observed experimentally for DSB rejoining and the formation of simple chromosome exchange aberrations are shown to be consistent with kinetic models based on enzymatic reaction approaches.
Abstract: PURPOSE: To investigate the role of kinetics in the processing of DNA double strand breaks (DSB), and the formation of simple chromosome exchange aberrations following X-ray exposures to mammalian cells based on an enzymatic approach. METHODS: Using computer simulations based on a biochemical approach, rate-equations that describe the processing of DSB through the formation of a DNA-enzyme complex were formulated. A second model that allows for competition between two processing pathways was also formulated. The formation of simple exchange aberrations was modelled as misrepair during the recombination of single DSB with undamaged DNA. Non-linear coupled differential equations corresponding to biochemical pathways were solved numerically by fitting to experimental data. RESULTS: When mediated by a DSB repair enzyme complex, the processing of single DSB showed a complex behaviour that gives the appearance of fast and slow components of rejoining. This is due to the time-delay caused by the action time of enzymes in biomolecular reactions. It is shown that the kinetic- and dose-responses of simple chromosome exchange aberrations are well described by a recombination model of DSB interacting with undamaged DNA when aberration formation increases with linear dose-dependence. Competition between two or more recombination processes is shown to lead to the formation of simple exchange aberrations with a dose-dependence similar to that of a linear quadratic model. CONCLUSIONS: Using a minimal number of assumptions, the kinetics and dose response observed experimentally for DSB rejoining and the formation of simple chromosome exchange aberrations are shown to be consistent with kinetic models based on enzymatic reaction approaches. A non-linear dose response for simple exchange aberrations is possible in a model of recombination of DNA containing a DSB with undamaged DNA when two or more pathways compete for DSB repair.

Journal ArticleDOI
TL;DR: Unstable aberrations characteristic of radiation-induced chromosomal instability may commonly result in apoptosis and account for a component of the delayed reproductive death/lethal mutation phenotype in HPV-G cells.
Abstract: Purpose : To investigate the relationship between two well-established delayed effects of ionizing radiation, experiments were conducted to determine the induction and expression of lethal mutations (delayed reproductive death) and chromosomal instability with respect to dose and time in a human immortalized keratinocyte cell line. Methods : HPV-G cells were γ- or α -irradiated and maintained in culture for up to 72 population doublings. At intervals, measurements were made of cloning efficiency and the cells examined for apoptosis and cytogenetic aberrations. Results : The descendants of cells surviving 1 or 3 Gy γ-irradiation, but not 0.5 Gy γ-irradiation, exhibited a reduced colony-forming efficiency. The reduction persisted at a constant rate of 15–20% clonogenic cell loss per population doubling for up to 72 population doublings. Apoptosis was demonstrated in all colonies in the 1 and 3 Gy groups at 30 and 72 population doublings post-irradiation but not in the 0.5 Gy group. A significant persistent ...

Journal ArticleDOI
TL;DR: The hypothesis that elevated TGF-beta levels during radiotherapy may not only indicate patients with a higher risk of developing pulmonary toxicity but also patients with high risk of treatment failure is suggested.
Abstract: Purpose : To determine whether changes in TGF-beta plasma levels during radiation therapy may be useful in predicting radiation-induced pulmonary injury and tumour response in non-small-cell lung cancer (NSCLC) patients. Materials and methods : Plasma TGF-beta was investigated in 27 patients with stage III NSCLC, who were treated with 60 Gy (2Gy/day) radiotherapy with or without carboplatin. TGF-beta was measured prior to beginning radiotherapy and weekly during treatment; evaluated as a ratio between TGF-beta levels obtained during treatment and the pretreatment TGF-beta level. The endpoints of the study were development of symptomatic radiation pneumonitis and tumour response. Results : Nine of the 27 patients developed pneumonitis. The patients who developed pneumonitis had high persistent TGF-beta levels throughout the course of treatment (TGF-beta ratio>1), whereas the TGF-beta levels in patients who did not develop pneumonitis were unchanged or declined towards normal (TGF-beta ratio<1). Patients wh...

Journal ArticleDOI
TL;DR: The results demonstrate that NF-kappaB plays a major role in X-ray-inducible IL-6 expression in HeLa cells and provide new insights into the prodromal events of radiation-induced inflammation of epithelial cells and putatively the cutaneous radiation syndrome.
Abstract: Purpose : To investigate the mechanisms leading to initiation by ionizing radiation of IL-6 transcription in HeLa cells. Materials and methods : HeLa cells were irradiated with X-rays at a dose rate of approximately 1 Gy/min or treated with TPA (100 ng/ml). Transient transfection analysis with truncated IL-6 promoter CAT constructs was used to identify the radiation-sensitive region within the IL-6 promoter/enhancer. Results : For basal expression of the IL-6 gene in unirradiated control cells the presence of the binding site for the nuclear factor kappa B (NF- κB) and the multiple response elements (MRE) were necessary. After deletion of either the activator protein (AP)-1 or the MRE site, radiation-induced IL-6 promoter CAT activity was significantly reduced, whereas after deletion of the NF-kappaB site it was completely abolished. Maximal radiation-induced IL-6 promoter CAT activity was observed when the AP1, NF κB and MRE motifs were present. In electrophoretic mobility shift analyses (EMSA), X-ray-in...

Journal ArticleDOI
TL;DR: The results show that PARP-1 plays a key role in the earliest steps of cell response to ionizing radiation with clonogenic ability or growth as endpoint, and is hypothesized to bring about rapid chromatin remodelling that may affect the incidence of chromosomal damage upon re-irradiation.
Abstract: Purpose : To determine whether DNA-dependent protein kinase (DNA-PK) and poly(ADP-ribose) polymerase (PARP-1) are involved in eliciting the rapid fluctuations of radiosensitivity that have been observed when cells are exposed to short pulses of ionizing radiation. Materials and methods : The effect of DNA-PK and PARP-1 inhibitors on the survival of cells to split-dose irradiation was investigated using Chinese hamster V79 fibroblasts and human carcinoma SQ-20B cells. The responses of PARP-1 proficient and PARP-1 knockout mouse 3T3 fibroblasts were compared in a similar split-dose assay. Results : Inactivation of DNA-PK by wortmannin potentiated radiation-induced cell kill but it did not alter the oscillatory, W-shaped pattern of early radiation response. In contrast, oscillatory radiation response was abolished by 3-aminobenzamide, a reversible inhibitor of enzymes containing a PARP catalytic domain. The oscillatory response was also lacking in PARP-1 knockout mouse 3T3 fibroblasts. Conclusion : The resul...

Journal ArticleDOI
TL;DR: Data indicate that the response of the CNS to irradiation includes the activation of a similar set of transcription factors as previously observed after other types of insults.
Abstract: Purpose : To determine the effects of ionising radiation on the DNA-binding activity of the injury-related transcription factors AP-1, Sp-1, p53 and NF κB in the rat brain. Materials and methods : Male Sprague-Dawley rats were irradiated with 137 Cs gamma-rays at 3.8Gy/min and the cerebral cortex was isolated at intervals up to 24h. Nuclear protein extract of the cerebral cortex was analysed by electrophoretic mobility shift assay for DNA-binding activity of AP-1, Sp-1, p53 and NF κB. In addition, total RNA was extracted from the cerebral cortex and subjected to northern analysis. Results : The DNA-binding activity of each of the transcription factors increased in a time- and dose-dependent manner after irradiation. Maximum increase in the activity of AP-1, Sp-1, and p53 DNA binding was seen after exposure to 10 Gy and then decreased after higher doses. In contrast, NF κB DNA-binding activity continued to increase out to at least 30 Gy. The levels of bFGF and p21 WAF-1 mRNA increased after irradiation, su...

Journal ArticleDOI
TL;DR: Interstitial fragments form a major class of radiation-induced chromosomal aberrations that are induced about half as frequently as dicentrics over the whole dose range investigated and suggest that the ratio between non- or incomplete repair and incorrect repair is independent of dose.
Abstract: Purpose : To generate dose-response curves for X-ray-induced chromosomal aberrations analysed in human blood lymphocytes using telomeric and centromeric peptide nucleic acid (PNA) probes. Materials and methods : Isolated human lymphocytes were X-irradiated with doses of 0, 1, 2, 3, 4 and 6 Gy. Aberrations were analysed in the first post-irradiation metaphases using telomeric and centromeric PNA probes. Results : Similar to the dose-response curves for the yield of dicentrics and centric rings, the dose-response curves for interstitial fragments and incomplete elements (derived from either terminal deletions or incomplete exchanges) follow a linear-quadratic function. Furthermore, it was estimated that 76% of excess acentric fragments originate from complete exchanges (interstitial deletions) and only 24% from incomplete exchanges or terminal deletions. Conclusions : Interstitial fragments form a major class of radiation-induced chromosomal aberrations. They are induced about half as frequently as dicentri...

Journal ArticleDOI
TL;DR: RBE values for the inactivation of cells irradiated in the spread-out Bragg peak are compatible with the value currently assumed in clinical applications and in the distal declining edge of the beam, the RBE values increased significantly to an extent that may be of concern when the region of the treatment volume is close to sensitive tissues.
Abstract: Purpose : To determine the relative biological effectiveness (RBE) for initial and delayed inactivation of cells by a modulated proton beam suitable for the treatment of tumours of the eye, within the spread-out Bragg peak and in its distal declining edge. Materials and methods : Human tumour SCC25 cells were irradiated with the 65 MeV proton beam at the Cyclotron Medicyc in Nice. Perspex plates of different thickness were used to simulate five positions along the beam line: 2 mm corresponding to the entrance beam; 15.6 and 25mm in the spread-out Bragg peak; 27.2 and 27.8mm for the distal edge. At each position clonogenic survival of the irradiated cells and of their progeny were determined at various dose values. 60 Co γ-rays were used as reference radiation. Results : RBE values evaluated at the survival level given by 2 Gy of γ-rays increased with increasing depth from close to 1.0 at the proximal to about 1.2 at the distal part of the peak. Within the declining edge it reached the value of about 1.4 a...

Journal ArticleDOI
TL;DR: The spectral and dose-effect behaviour indicates that DSB are induced predominantly by single-event processes in the energy range covered, and provides evidence for the ability of photons as low as 7 eV to induce both SSB and DSB.
Abstract: ations deposit a wide range of energies within the Purpose: To measure action spectra for the induction of single- critical target (i.e. a small section of the DNA helix) strand breaks (SSB) and double-strand breaks (DSB) in plasmid (Goodhead 1989, Goodhead and Nikjoo 1989, Nikjoo DNA by low-energy photons and provide estimates for the et al. 1997, Ottolenghi et al. 1997). These will be from energy dependence of strand-break formation important for zero energy up to several hundred electron volts, track-structure simulations of DNA damage. Materials and methods: Plasmid pMSG-CAT was irradiated as a although densely ionizing radiation will produce a monolayer, under vacuum, with 7‐150eV photons produced greater fraction of higher energy depositions than by a synchrotron source. Yields of SSB and DSBwere determined sparsely ionizing radiation. Many modelling studies by the separation of the three plasmid forms by gel have equated this distribution of energy events with electrophoresis. the likely yields and spectra of lesions that will be Results: The yields of SSB per incident photon increased from 1.4O 10O 15 SSB per plasmid per photon/cm 2 at 7eV to produced in DNA by radiations of diU ering LET