Chromosome Aberrations induced by the Auger emitter I-125

Introduction: DNA-associated Auger-electron emitters (AEE) induce cellular damage leading to high-LET type cell survival curves and possess enhanced relative biological effectiveness. DNA dsb induced by Iodine-125-deoxyuridine (I-125-UdR) decays are claimed to be very complex, thus efficiently leading to cell transformation, gene mutation and induction of chromatid aberrations. To elucidate the assumed genotoxic potential of DNA-associated AEE, chromosomal/chromatid aberrations were analyzed in I-125-UdR-exposed human peripheral blood lymphocytes (PBL).Methods: PBL were isolated from whole blood and stimulated with chromosome medium containing phytohaemagglutinin (PHA). After 24 h cultures were labeled with I-125-UdR for 18 h (0.25-4.5 kBq/ml) during the S-phase of the cell cycle. After removal of radioactive medium and washing steps, cells were re-cultured in stimulation medium for further 24 h. Colcemid was added 5.5 h before harvest of cells followed by fixation for aberrations at 71.5 h post-stimulation. All slides were stained with 10 % Giemsa, and 100 metaphases were analyzed microscopically for each dose point.Results: After 18 h labeling with I-125-UdR the cell cycle distribution is severely disturbed. Furthermore, 40% of PBL are fully labelled and 20% show a moderate uptake of I-125-UdR. I-125-UdR primarily induces chromatid-type aberrations. PBL reveal a very broad dose-dependent response spectrum: equal numbers of cells have either no aberration, or display a moderate aberration level (1-9 aberrations). Few cells exhibit a high aberration score (> 10 aberrations). A dose-dependent increase of aberrations is measured in the range of 0.2 to 2 Gy, followed by a plateau between 2 and 4.5 Gy. The data indicate that even the lowest dose of 0.2 Gy leads to significant damage in PBL and to a 4.5-fold increase of aberrations compared to the controls. Furthermore, a dose-dependent increase of cell death is observed.Conclusions: I-125-UdR has a very strong genotoxic capacity in human PBL even at very low doses of about 0.2 Gy. Efficiently labeled cells displaying a prolonged cell cycle compared to moderate labeled cells, and cell death contribute substantially to the desynchronisation of the cell cycle. In summary, it can be concluded that every fourth intracellular I-125 decay give rise to a single chromosome aberration

Corrigendum to 'Chromosome aberrations induced by the Auger electron emitter (125)I' [Mut. Res.-Genet. Toxicol. Environ. Mutagen. 793 (2015) 64-70].

The authors regret that a mistake occurred in Section 4.2.3 of the discussion, in the summary (Section 5) and in the abstract, when comparing their own results with data from the literature (Yasui 2004; Sedelnikova et al., 2002). The argumentation that every 125I-induced dsb is converted into a chromosome aberration is wrong. We made an incorrect calculation when correlating the decays per cell with the resulting chromosome aberrations. After reconsideration, our data (based on nine experiments) indicate that it takes on average 250 decays to induce one chromosome aberration (CA). Thus, the comparison of our CA data with the DSB data from Yasui [18] and Sedelnikova et al. [17] seems to be not adequate anymore. The authors would like to apologise for any inconvenience caused

Chromosome aberrations induced by the Auger electron emitter 125I

DNA-associated Auger electron emitters (AEE) cause cellular damage leading to high-LET type cell survivalcurves indicating an enhanced relative biological effectiveness. Double strand breaks (DSBs) induced byIodine-125-deoxyuridine (125I-UdR) decays are claimed to be very complex. To elucidate the assumedgenotoxic potential of125I-UdR, chromatid aberrations were analysed in exposed human peripheral bloodlymphocytes (PBL).PBL were stimulated with medium containing phytohaemagglutinin (PHA). After 24 h, cultures werelabelled with125I-UdR for 18 h (activity concentration 1–45 kBq) during the S-phase. Following stan-dard cytogenetic procedure, at least 100 metaphases were analysed microscopically for each activityconcentration. Cell death was measured by apoptosis assay using flow cytometry. Radiation doses weredetermined by using point kernel calculations.After 18 h labelling with125I-UdR the cell cycle distribution is severely disturbed. About 40% of PBL arefully labelled and 20% show a moderate labelling of125I-UdR, whereas 40% of cells remain un-labelled. Thedose-response relationship fits to a polynomial curve in the low dose range, whereas a linear fit suppliesa better estimation in the high dose range. Even the lowest dose of 0.2 Gy leads to a 13-fold increaseof aberrations compared to the controls. On average every fifth125I-decay produces a single chromatidaberration in PBL. Additionally, a dose-dependent increase of cell death is observed.125I-UdR has a very strong genotoxic capacity in human PBL, even at 0.2 Gy. Efficiently labelled cellsdisplaying a prolonged cell cycle compared to moderately labelled cells and cell death contribute substan-tially to the desynchronisation of the cell cycle. Our data, showing for the first time, that one125I-decayinduces ∼ 0.2 chromatid aberrations, are in very good accordance to DSB data, stating that ∼0.26 DSB areinduced per decay, indicating that approximately every DSB is converted into a chromatid aberration

Chromosome Aberrations induced by the Auger electron emitter I-125

Introduction: DNA-associated Auger-electron emitters (AEE) cause cellular damage leading to high-LET type cell survival curves indicating an enhanced relative biological effectiveness. DNA double strand breaks (DSBs) induced by Iodine-125-deoxyuridine (I-125-UdR) decays are claimed to be very complex. To elucidate the assumed genotoxic potential of DNA-associated AEE, chromosome aberrations were analyzed in I-125-UdR-exposed human peripheral blood lymphocytes (PBL). Methods: PBL were isolated from whole blood and stimulated with chromosome medium containing phytohaemagglutinin (PHA). After 24 h cultures were labelled with I-125-UdR for 18 h (activity concentration 1 – 45 kBq) during the S-phase. Following standard cytogenetic procedure, at least 100 metaphases were analyzed microscopically for each activity concentration. Cell death was measured by apoptosis assay using flow cytometry. Radiation doses were determined by using point kernel calculations.Results: After 18 h labeling with I-125-UdR the cell cycle distribution is severely disturbed. About 40 % of PBL are fully labeled and 20 % show a moderate labeling of I-125-UdR, whereas 40 % of cells remain unlabeled. I-125-UdR primarily induces chromatid-type aberrations. The dose-response relationship fits well to a polynomial curve in the low dose range, whereas a linear fit supplies a better estimation in the high dose range. Even the lowest dose of 0.2 Gy leads to significant damage and to a 13-fold increase of aberrations compared to the controls. On average every fifth I-125-decay produces a single chromatid aberration in PBL. In addition, a dose-dependent increase of cell death is observed. Conclusions: I-125-UdR has a very strong genotoxic capacity in human PBL even at very low cellular doses of about 0.2 Gy. Efficiently labeled cells displaying a prolonged cell cycle compared to moderately labeled cells and cell death contribute substantially to the desynchronisation of the cell cycle. Our data, showing that one I-125-decay induces 0.2 chromatid aberrations, are in very good accordance to the data of Sedelnikova [1] and Yasui [2] who found 0.26 DSB per decay, indicating that approximately every DSB is converted into a chromatid aberration.[1] O.A. Sedelnikova et al. Radiation Research 158, 486 (2002)[2] L.S. Yasui, Int. J. Radiat. Biol., 80, 895 (2004

Analysis of Iodine-125-induced chromosome aberrations

DNA-associated Auger-electron emitters (AEE) induce cellular damage leading to high-LET type cell survival curves and possess enhanced relative biological effectiveness. Moreover, DNA dsb induced by 125I-deoxyuridine (125I-UdR) decays are claimed to be very complex. To elucidate the assumed genotoxic potential, chromosome aberrations were analyzed in 125I-UdR-exposed human peripheral blood lymphocytes (PBL).After 18 h labeling with 125I-UdR the cell cycle distribution is severely disturbed. Furthermore, 40% of PBL are fully labelled and 20% show a moderate uptake. Primarily chromatid-type aberrations are induced. PBL reveal a very broad dose-dependent response spectrum: equal numbers of cells have either no aberration, or display a moderate aberration level. Few cells exhibit a high aberration score (> 10 aberrations). A dose-dependent increase of aberrations is measured in the range of 0.2 to 2 Gy, followed by a plateau between 2 and 4.5 Gy. The data indicate that even the lowest dose of 0.2 Gy leads to a 4.5-fold increase of aberrations in PBL compared to the controls. Furthermore, a dose-dependent increase of cell death is observed.125I-UdR has a very strong genotoxic capacity in human PBL even at very low doses of about 0.2 Gy. Efficiently labeled cells display a prolonged cell cycle compared to moderate labeled cells and cell death contributes substantially to the desynchronisation of the cell cycle. It can be concluded that every fourth intracellular 125I decay give rise to a single chromosome aberration

Geno- and Cytotoxicity of DNA-associated Auger Electron emitters

Theoretical considerations, Monte-Carlo simulations and experimental findings suggest that DNA-incorporated Auger electron emitters (AEE) cause primarily complex and clustered DNA lesions. It was previously shown that the shape of AEE-induced cell survival curves resembles that of High-LET irradiation and, therefore, poses the question of an increased biological effectiveness and a separate quality factor for Auger electrons. During electron capture or internal conversion an electron vacancy in an inner atomic shell is created. Filling the electron vacancy by a higher shell electron can initiate a process of non-radiative energy transmission, commonly termed as “Auger effect”. During the process numerous low-energy Auger electrons (up to 27 in the case of Iodine-125) with a short range are emitted leading to energy densities and free radical production in the close vicinity of the emitter exceeding that of a 5 MeV alpha-particle traversing the DNA double-helix. Experimental data demonstrate, that the cyto- and genotoxicity of AEE is comparable to low-LET radiation per unit dose when the AEE is exclusively located in the cytoplasm. However, in case of DNA-incorporation RBEs ranging from 5 – 9 are frequently reported. Employing the alkaline and neutral comet assay, the high DSB/SSB ratio of I-125-iododeoxyuridine derived from Monte-Carlo simulations could be experimentally confirmed. The unique properties of AEE and the possibility to target DNA in a sequence-specific manner using AEE-labeled Triplex-forming oligonucleotides (TFOs) enable to study the repair of complex DNA lesions at defined sites in more detail. A transgenic SCL-II p2RT strain carrying the stably integrated recoverable p2RT vector system harboring a specific triplex target sequence for TFO-p2RT will help to analyze the repair efficiency of complex DNA lesions regarding mutation frequency, mutation type and mutation localization

Chromosomal radiosensitivity of prostate cancer patients and healthy donors analysed by FISH

Background: It is known that about 10 % of cancer patients show severe clinical side effects during and after radiotherapy due to enhanced sensitivity to ionizing ra-diation. Identification of those radiosensitive individuals by an in vitro assay before onset of treatment would be of great impact for successful radiotherapy.In this study we compared the radiosensitivity of the chromosomes 2, 11 and 17 in prostate cancer patients with and without severe side effects after radiotherapy and in age-matched healthy donors (control cohort). The chromosomal radiosensitivity of peripheral blood lymphocytes (PBL) of radiotherapy patients was used as predictive parameter for clinical side effects.Material und Methods: Each cohort consisted of at least 10 donors. PBL were irra-diated ex vivo with 0.5, 1 und 2 Gy (Cs-137 -rays) in the G0-Phase of the cell cycle. We analyzed the radiosensitivity of the chromosomes 2, 11 and 17 by scoring of 100 FISH painted metaphases for each dose point. Statistical analyses were performed by non-parametric Mann-Whitney test, by test of variances (ANOVA) and Chi-square goodness-of-fit test at a significance level of 0.05. Results: Analysis of the overall aberration yield revealed no significant differences between any donor groups. However, variance analyses showed significant differ-ences between the patient’s cohort and healthy donors for chromosomes 11 and 17 for all doses analyzed. In contrast, this was not true for chromosome 2. Furthermore, good correlations between chromosomes sizes (DNA content) and aberration yield were found.Conclusion: The cohort of prostate cancer patients can be distinguished from healthy donors due to variances of the aberration yields of the chromosomes 11 and 17. These chromosomes might be potential cytogenetic biomarkers for prostate can-cer patients in clinical studies. Funded by Dr. Erich-Schmitt -Foundatio

TP53 Mutations in Low-Risk Myelodysplastic Syndromes With del(5q) Predict Disease Progression

Purpose To determine the frequency of TP53 mutations and the level of p53 protein expression by immunohistochemistry (IHC) in low-risk myelodysplastic syndromes (MDS) with del(5q) and to assess their impact on disease progression. Patients and Methods Pre- and postprogression bone marrow (BM) samples from 55 consecutive patients with International Prognostic Scoring System low risk (n = 32) or intermediate-1 risk (n = 23) were studied by next-generation sequencing of TP53. IHC for p53 was performed on 148 sequential BM samples. Results TP53 mutations with a median clone size of 11% (range, 1% to 54%) were detected in 10 patients (18%) already at an early phase of the disease. Mutations were equally common in low-risk and intermediate-1–risk patients and were associated with evolution to acute myeloid leukemia (5 of 10 v 7 of 45; P = .045). Nine of 10 patients carrying mutations showed more than 2% BM progenitors with strong p53 staining. The probability of a complete cytogenetic response to lenalidomide was lower in mutated patients (0 of 7 v 12 of 24; P = .024). Conclusion By using sensitive deep-sequencing technology, we demonstrated that TP53 mutated populations may occur at an early disease stage in almost a fifth of low-risk MDS patients with del(5q). Importantly, mutations were present years before disease progression and were associated with an increased risk of leukemic evolution. TP53 mutations could not be predicted by common clinical features but were associated with p53 overexpression. Our findings indicate a previously unrecognized heterogeneity of the disease which may significantly affect clinical decision making. </jats:sec