RENEB Inter-Laboratory comparison 2017: limits and pitfalls of ILCs.

PURPOSE: In case of a mass-casualty radiological event, there would be a need for networking to overcome surge limitations and to quickly obtain homogeneous results (reported aberration frequencies or estimated doses) among biodosimetry laboratories. These results must be consistent within such network. Inter-laboratory comparisons (ILCs) are widely accepted to achieve this homogeneity. At the European level, a great effort has been made to harmonize biological dosimetry laboratories, notably during the MULTIBIODOSE and RENEB projects. In order to continue the harmonization efforts, the RENEB consortium launched this intercomparison which is larger than the RENEB network, as it involves 38 laboratories from 21 countries. In this ILC all steps of the process were monitored, from blood shipment to dose estimation. This exercise also aimed to evaluate the statistical tools used to compare laboratory performance. MATERIALS AND METHODS: Blood samples were irradiated at three different doses, 1.8, 0.4 and 0 Gy (samples A, C and B) with 4-MV X-rays at 0.5 Gy min-1, and sent to the participant laboratories. Each laboratory was requested to blindly analyze 500 cells per sample and to report the observed frequency of dicentric chromosomes per metaphase and the corresponding estimated dose. RESULTS: This ILC demonstrates that blood samples can be successfully distributed among laboratories worldwide to perform biological dosimetry in case of a mass casualty event. Having achieved a substantial harmonization in multiple areas among the RENEB laboratories issues were identified with the available statistical tools, which are not capable to advantageously exploit the richness of results of a large ILCs. Even though Z- and U-tests are accepted methods for biodosimetry ILCs, setting the number of analyzed metaphases to 500 and establishing a tests' common threshold for all studied doses is inappropriate for evaluating laboratory performance. Another problem highlighted by this ILC is the issue of the dose-effect curve diversity. It clearly appears that, despite the initial advantage of including the scoring specificities of each laboratory, the lack of defined criteria for assessing the robustness of each laboratory's curve is a disadvantage for the 'one curve per laboratory' model. CONCLUSIONS: Based on our study, it seems relevant to develop tools better adapted to the collection and processing of results produced by the participant laboratories. We are confident that, after an initial harmonization phase reached by the RENEB laboratories, a new step toward a better optimization of the laboratory networks in biological dosimetry and associated ILC is on the way.

Biocompatible DNA/5-Fluorouracil-Gemini Surfactant-Functionalized Gold Nanoparticles as Promising Vectors in Lung Cancer Therapy.

The design and preparation of novel nanocarriers to transport cancer drugs for chemotherapy purposes is an important line of research in the medical field. A new 5-fluorouracil (5-Fu) transporter was designed based on the use of two new biocompatible gold nanosystems: (i) a gold nanoparticle precursor, Au@16-Ph-16, stabilized with the positively charged gemini surfactant 16-Ph-16, and (ii) the compacted nanocomplexes formed by the precursor and DNA/5-Fu complexes, Au@16-Ph-16/DNA-5-Fu. The physicochemical properties of the obtained nanosystems were studied by using UV-visible spectroscopy, TEM, dynamic light scattering, and zeta potential techniques. Method tuning also requires the use of circular dichroism, atomic force microscopy, and fluorescence spectroscopy techniques for the prior selection of the optimal relative Au@16-Ph-16 and DNA concentrations (R = CAu@16-Ph-16/CDNA), biopolymer compaction/decompaction, and 5-Fu release from the DNA/5-Fu complex. TEM experiments revealed the effective internalization of the both precursor and Au@16-Ph-16/DNA-5-Fu-compacted nanosystems into the cells. Moreover, cytotoxicity assays and internalization experiments using TEM and confocal microscopy showed that the new strategy for 5-Fu administration enhanced efficacy, biocompatibility and selectivity against lung cancer cells. The differential uptake among different formulations is discussed in terms of the physicochemical properties of the nanosystems.

Real-world use of key performance indicators for point-of-Care Testing network accredited by ISO 22870.

OBJECTIVE: We aimed to evaluate the results of key performance indicators (KPIs) for a period of over three years, as well as their effectiveness as an improvement tool, to provide information about Point-of-Care Testing (POCT) management system performance and quality assurance. DESIGN AND METHODS: KPIs regarding the global POCT process, extra-analytical phase, quality assurance and staff training and competency were evaluated for blood gases, HbA1c, sweat test and non-connected and connected glucose in an ISO 22870 accredited network. We established the definition of every KPI and its corresponding target. The results of KPIs from all clinical settings were appraised every month during the study period, taking corrective actions when necessary. RESULTS: Annual global results were generally acceptable. However, some clinical areas displayed deviations in specific months. The monitoring of these KPIs allowed us to detect the deviations immediately and identify their causes. These included errors in patient identification, consumables, strips, reagents, analyzers, calibration, internal and external quality control, sample management, connectivity, and operator identification strategy, among others. CONCLUSIONS: The evaluation of these KPIs over time has shown their appropriateness. This set of quality indicators could be a useful tool for laboratory medicine leading POCT networks for better and safer patient care.

The Cockayne syndrome protein B is involved in the repair of 5-AZA-2'-deoxycytidine-induced DNA lesions.

The Cockayne Syndrome Protein B (CSB) plays an essential role in Transcription-Coupled Nucleotide Excision Repair (TC-NER) by recruiting repair proteins once transcription is blocked with a DNA lesion. In fact, CSB-deficient cells are unable to recover from transcription-blocking DNA lesions. 5-Aza-2'-deoxycytidine (5-azadC) is a nucleoside analogue that covalently traps DNA methyltransferases (DNMTs) onto DNA. This anticancer drug has a double mechanism of action: it reverts aberrant hypermethylation in tumour-suppressor genes, and it induces DNA damage. We have recently reported that Homologous Recombination and XRCC1/PARP play an important role in the repair of 5-azadC-induced DNA damage. However, the mechanisms involved in the repair of the DNMT adducts induced by azadC remain poorly understood. In this paper, we show for the first time the importance of CSB in the repair of azadC-induced DNA lesions. We propose a model in which CSB initiates a signalling pathway to repair transcription blocks induced by incorporated 5-azadC. Indeed, CSB-deficient cells treated with 5-azadC show a delay in the repair of trapped DNMT1, increased levels of DNA damage and reduced survival.

Zebularine induces replication-dependent double-strand breaks which are preferentially repaired by homologous recombination.

Zebularine is a second-generation, highly stable hydrophilic inhibitor of DNA methylation with oral bioavailability that preferentially target cancer cells. It acts primarily as a trap for DNA methyl transferases (DNMTs) protein by forming covalent complexes between DNMT protein and zebularine-substrate DNA. It's well documented that replication-blocking DNA lesions can cause replication fork collapse and thereby to the formation of DNA double-strand breaks (DSB). DSB are dangerous lesions that can lead to potentially oncogenic genomic rearrangements or cell death. The two major pathways for repair of DSB are non-homologous end joining (NHEJ) and homologous recombination (HR). Recently, multiple functions for the HR machinery have been identified at arrested forks. Here we investigate in more detail the importance of the lesions induced by zebularine in terms of DNA damage and cytotoxicity as well as the role of HR in the repair of these lesions. When we examined the contribution of NHEJ and HR in the repair of DSB induced by zebularine we found that these breaks were preferentially repaired by HR. Also we show that the production of DSB is dependent on active replication. To test this, we determined chromosome damage by zebularine while transiently inhibiting DNA synthesis. Here we report that cells deficient in single-strand break (SSB) repair are hypersensitive to zebularine. We have observed more DSB induced by zebularine in XRCC1 deficient cells, likely to be the result of conversion of SSB into toxic DSB when encountered by a replication fork. Furthermore we demonstrate that HR is required for the repair of these breaks. Overall, our data suggest that zebularine induces replication-dependent DSB which are preferentially repaired by HR.

Investigation of the influence of calibration practices on cytogenetic laboratory performance for dose estimation.

PURPOSE: In the frame of the QA program of RENEB, an inter-laboratory comparison (ILC) of calibration sources used in biological dosimetry was achieved to investigate the influence of calibration practices and protocols on the results of the dose estimation performance as a first step to harmonization and standardization of dosimetry and irradiation practices in the European biological dosimetry network. MATERIALS AND METHODS: Delivered doses by irradiation facilities used by RENEB partners were determined with EPR/alanine dosimetry system. Dosimeters were irradiated in the same conditions as blood samples. A short survey was also performed to collect the information needed for the data analysis and evaluate the diversity of practices. RESULTS: For most of partners the deviation of delivered dose from the targeted dose remains below 10%. Deviations larger than 10% were observed for five facilities out of 21. Origins of the largest discrepancies were identified. Correction actions were evaluated as satisfactory. The re-evaluation of some ILC results for the fluorescence in situ hybridization (FISH) and premature chromosome condensation (PCC) assays has been performed leading to an improvement of the overall performances. CONCLUSIONS: This work has shown the importance of dosimetry in radiobiology studies and the needs of harmonization, standardization in irradiation and dosimetry practices and educational training for biologists using ionizing radiation.

RENEB accident simulation exercise.

PURPOSE: The RENEB accident exercise was carried out in order to train the RENEB participants in coordinating and managing potentially large data sets that would be generated in case of a major radiological event. MATERIALS AND METHODS: Each participant was offered the possibility to activate the network by sending an alerting email about a simulated radiation emergency. The same participant had to collect, compile and report capacity, triage categorization and exposure scenario results obtained from all other participants. The exercise was performed over 27 weeks and involved the network consisting of 28 institutes: 21 RENEB members, four candidates and three non-RENEB partners. RESULTS: The duration of a single exercise never exceeded 10 days, while the response from the assisting laboratories never came later than within half a day. During each week of the exercise, around 4500 samples were reported by all service laboratories (SL) to be examined and 54 scenarios were coherently estimated by all laboratories (the standard deviation from the mean of all SL answers for a given scenario category and a set of data was not larger than 3 patient codes). CONCLUSIONS: Each participant received training in both the role of a reference laboratory (activating the network) and of a service laboratory (responding to an activation request). The procedures in the case of radiological event were successfully established and tested.

RENEB intercomparison exercises analyzing micronuclei (Cytokinesis-block Micronucleus Assay).

PURPOSE: In the framework of the 'Realizing the European Network of Biodosimetry' (RENEB) project, two intercomparison exercises were conducted to assess the suitability of an optimized version of the cytokinesis-block micronucleus assay, and to evaluate the capacity of a large laboratory network performing biodosimetry for radiation emergency triages. Twelve European institutions participated in the first exercise, and four non-RENEB labs were added in the second one. MATERIALS AND METHODS: Irradiated blood samples were shipped to participating labs, whose task was to culture these samples and provide a blind dose estimate. Micronucleus analysis was performed by automated, semi-automated and manual procedures. RESULTS: The dose estimates provided by network laboratories were in good agreement with true administered doses. The most accurate estimates were reported for low dose points (≤ 0.94 Gy). For higher dose points (≥ 2.7 Gy) a larger variation in estimates was observed, though in the second exercise the number of acceptable estimates increased satisfactorily. Higher accuracy was achieved with the semi-automated method. CONCLUSION: The results of the two exercises performed by our network demonstrate that the micronucleus assay is a useful tool for large-scale radiation emergencies, and can be successfully implemented within a large network of laboratories.

RENEB - Running the European Network of biological dosimetry and physical retrospective dosimetry.

PURPOSE: A European network was initiated in 2012 by 23 partners from 16 European countries with the aim to significantly increase individualized dose reconstruction in case of large-scale radiological emergency scenarios. RESULTS: The network was built on three complementary pillars: (1) an operational basis with seven biological and physical dosimetric assays in ready-to-use mode, (2) a basis for education, training and quality assurance, and (3) a basis for further network development regarding new techniques and members. Techniques for individual dose estimation based on biological samples and/or inert personalized devices as mobile phones or smart phones were optimized to support rapid categorization of many potential victims according to the received dose to the blood or personal devices. Communication and cross-border collaboration were also standardized. To assure long-term sustainability of the network, cooperation with national and international emergency preparedness organizations was initiated and links to radiation protection and research platforms have been developed. A legal framework, based on a Memorandum of Understanding, was established and signed by 27 organizations by the end of 2015. CONCLUSIONS: RENEB is a European Network of biological and physical-retrospective dosimetry, with the capacity and capability to perform large-scale rapid individualized dose estimation. Specialized to handle large numbers of samples, RENEB is able to contribute to radiological emergency preparedness and wider large-scale research projects.

RENEB intercomparisons applying the conventional Dicentric Chromosome Assay (DCA).

PURPOSE: Two quality controlled inter-laboratory exercises were organized within the EU project 'Realizing the European Network of Biodosimetry (RENEB)' to further optimize the dicentric chromosome assay (DCA) and to identify needs for training and harmonization activities within the RENEB network. MATERIALS AND METHODS: The general study design included blood shipment, sample processing, analysis of chromosome aberrations and radiation dose assessment. After manual scoring of dicentric chromosomes in different cell numbers dose estimations and corresponding 95% confidence intervals were submitted by the participants. RESULTS: The shipment of blood samples to the partners in the European Community (EU) were performed successfully. Outside the EU unacceptable delays occurred. The results of the dose estimation demonstrate a very successful classification of the blood samples in medically relevant groups. In comparison to the 1st exercise the 2nd intercomparison showed an improvement in the accuracy of dose estimations especially for the high dose point. CONCLUSIONS: In case of a large-scale radiological incident, the pooling of ressources by networks can enhance the rapid classification of individuals in medically relevant treatment groups based on the DCA. The performance of the RENEB network as a whole has clearly benefited from harmonization processes and specific training activities for the network partners.

Integration of new biological and physical retrospective dosimetry methods into EU emergency response plans - joint RENEB and EURADOS inter-laboratory comparisons.

PURPOSE: RENEB, 'Realising the European Network of Biodosimetry and Physical Retrospective Dosimetry,' is a network for research and emergency response mutual assistance in biodosimetry within the EU. Within this extremely active network, a number of new dosimetry methods have recently been proposed or developed. There is a requirement to test and/or validate these candidate techniques and inter-comparison exercises are a well-established method for such validation. MATERIALS AND METHODS: The authors present details of inter-comparisons of four such new methods: dicentric chromosome analysis including telomere and centromere staining; the gene expression assay carried out in whole blood; Raman spectroscopy on blood lymphocytes, and detection of radiation-induced thermoluminescent signals in glass screens taken from mobile phones. RESULTS: In general the results show good agreement between the laboratories and methods within the expected levels of uncertainty, and thus demonstrate that there is a lot of potential for each of the candidate techniques. CONCLUSIONS: Further work is required before the new methods can be included within the suite of reliable dosimetry methods for use by RENEB partners and others in routine and emergency response scenarios.

Psychometric properties of the reading comprehension test ECOMPLEC. Sec / Propiedades psicométricas de la prueba de compresión lectora ECOMPLEC.SEC

ANTECEDENTES: en ciencias sociales, del comportamiento y de salud es habitual usar tests breves. El tamaño del test puede afectar a la correcta identificación de ítems con DIF. Este trabajo compara la eficacia relativa de la Regresión Logística Discriminante (RLD) e IRTLRDIF en la detección del DIF en tests cortos politómicos. MÉTODO: se diseñó un estudio de simulación. Se manipuló tamaño del test, tamaño de la muestra, cantidad DIF y número de categorías de respuesta al ítem. Se evaluó el Error Tipo I y la potencia. RESULTADOS: en las condiciones de no-DIF IRTLRDIF y RLD mostraron tasas de Error Tipo I cercanas al nivel nominal. En tests con DIF las tasas de Error Tipo I dependieron del tamaño del test, de la muestra, cantidad de DIF, contaminación del test y número de categorías del ítem. RLD presentó mayor tasa de Error Tipo I que IRTLRDIF. La potencia estuvo afectada por la cantidad de DIF y tamaño de la muestra. En tests muy cortos RLD mostró mayor potencia que IRTLRDIF. CONCLUSIONES: en tests cortos y con DIF las tasas de Error Tipo I fueron elevadas. La potencia de IRTLRDIF y RLD fue relativamente baja en tests cortos y tamaños muestrales pequeños BACKGROUND: COOMPLEC.Sec is a reading comprehension test for secondary students, conceived from a multidimensional perspective in line with large-scale educational surveys such as PISA or PIRLS. The objective of this study was to validate the theoretical model of ECOMPLEC.Sec. A bifactor model that postulates the existence of a general reading comprehension factor and three specific factors provided a good fit to the data. METHOD: 1,912 adolescents (13-18 years) participated in this study. Data analysis included construct validity via confirmatory factor analysis, and factors were regressed onto observed covariates for the interpretation of the constructs. Reliability was calculated from a non-linear SEM in order to justify the interpretability of the observed scale and subscale scores. RESULTS: the bifactor model exhibited a significantly better fit to the data than the second-order model. Furthermore, construct validity analysis suggests the existence of specific reading comprehension factors. Finally, the reliability study also supports the idea of using a total score to obtain a measure of reading comprehension. CONCLUSIONS: ECOMPLEC.Sec displays a valid parsimonious factor structure, as well as metric properties that make it a suitable tool to assess reading comprehension

ANTECEDENTES: ECOMPLEC.Sec es una prueba de comprensión lectora para estudiantes de Secundaria concebido desde una perspectiva multidimensional en consonancia con las pruebas educativas de gran escala como PISA o PIRLS. El objetivo de este estudio fue la validación del modelo teórico de ECOMPLEC.Sec. Un modelo bifactorial que presupone la existencia de un factor general de comprensión lectora y tres factores específicos ajustó adecuadamente a los datos. MÉTODO: 1.912 adolescentes (edades entre 13-18 años) participaron en este estudio. Los análisis estadísticos incluyen un análisis factorial confirmatorio cuyos factores se predicen por cuatro covariables con el fin de aportar significado a los constructos. La fiabilidad se abordó desde un modelo no lineal SEM para ayudar en la interpretación de las puntuaciones observadas de las escalas y subescalas. RESULTADOS: el modelo bifactorial exhibió un ajuste significativamente mejor que el modelo factorial de segundo orden. Las evidencias de validez de constructo apuntan a la existencia de factores específicos de comprensión lectora. CONCLUSIONES: ECOMPLEC.Sec muestra una estructura factorial parsimoniosa junto con unas propiedades psicométricas que hacen de ella una prueba adecuada para evaluar la comprensión lectora

Psychometric properties of the reading comprehension test ECOMPLEC.Sec.

BACKGROUND: ECOMPLEC.Sec is a reading comprehension test for secondary students, conceived from a multidimensional perspective in line with large-scale educational surveys such as PISA or PIRLS. The objective of this study was to validate the theoretical model of ECOMPLEC.Sec. A bifactor model that postulates the existence of a general reading comprehension factor and three specific factors provided a good fit to the data. METHOD: 1,912 adolescents (13-18 years) participated in this study. Data analysis included construct validity via confirmatory factor analysis, and factors were regressed onto observed covariates for the interpretation of the constructs. Reliability was calculated from a non-linear SEM in order to justify the interpretability of the observed scale and subscale scores. RESULTS: The bifactor model exhibited a significantly better fit to the data than the second-order model. Furthermore, construct validity analysis suggests the existence of specific reading comprehension factors. Finally, the reliability study also supports the idea of using a total score to obtain a measure of reading comprehension. CONCLUSIONS: ECOMPLEC.Sec displays a valid parsimonious factor structure, as well as metric properties that make it a suitable tool to assess reading comprehension.

The PARP inhibitor Olaparib disrupts base excision repair of 5-aza-2'-deoxycytidine lesions.

Decitabine (5-aza-2'-deoxycytidine, 5-azadC) is used in the treatment of Myelodysplatic syndrome (MDS) and Acute Myeloid Leukemia (AML). Its mechanism of action is thought to involve reactivation of genes implicated in differentiation and transformation, as well as induction of DNA damage by trapping DNA methyltranferases (DNMT) to DNA. We demonstrate for the first time that base excision repair (BER) recognizes 5-azadC-induced lesions in DNA and mediates repair. We find that BER (XRCC1) deficient cells are sensitive to 5-azadC and display an increased amount of DNA single- and double-strand breaks. The XRCC1 protein co-localizes with DNMT1 foci after 5-azadC treatment, suggesting a novel and specific role of XRCC1 in the repair of trapped DNMT1. 5-azadC-induced DNMT foci persist in XRCC1 defective cells, demonstrating a role for XRCC1 in repair of 5-azadC-induced DNA lesions. Poly (ADP-ribose) polymerase (PARP) inhibition prevents XRCC1 relocation to DNA damage sites, disrupts XRCC1-DNMT1 co-localization and thereby efficient BER. In a panel of AML cell lines, combining 5-azadC and Olaparib cause synthetic lethality. These data suggest that PARP inhibitors can be used in combination with 5-azadC to improve treatment of MDS and AML.

Chromosomal radiosensitivity in patients with multiple sclerosis.

Multiple sclerosis is a clinically heterogeneous autoimmune disease leading to severe neurological disability. Although during the last years many disease-modifying agents as treatment options for multiple sclerosis have been made available, their mechanisms of action are still not fully determined. In the present study radiosensitivity in lymphocytes of patients with relapsing-remitting multiple sclerosis, secondary progressive multiple sclerosis and healthy controls was investigated. Whole blood cultures from multiple sclerosis patients and healthy controls were used to analyze the spontaneous and radiation-induced micronuclei in binucleated lymphocytes. A subgroup of patients with relapsing-remitting multiple sclerosis was treated with immunomodulatory agents, interferon ß or glatiramer acetate. The secondary progressive multiple sclerosis patients group was not receiving any treatment. Our results reveal that the basal DNA damage was not different between relapsing-remitting and secondary progressive multiple sclerosis patients, and healthy controls. No differences between gamma-irradiation induced micronuclei frequencies in binucleated cells from relapsing-remitting and secondary progressive multiple sclerosis patients, and healthy controls were found either. Nevertheless, when we compared the radiation induced DNA damage in binucleated cells from healthy individuals with the whole group of patients, a reduction in the frequency of micronuclei was obtained in the patients group. Induced micronuclei yield was significantly lower in the irradiated samples from treated relapsing-remitting multiple sclerosis patients than in healthy controls and relapsing-remitting not treated patients. Intrinsic sensitivity of lymphocytes subpopulations to the apoptotic effect of immunomodulatory treatment could be responsible for this result.

5-Aza-2'-deoxycytidine causes replication lesions that require Fanconi anemia-dependent homologous recombination for repair.

5-Aza-2'-deoxycytidine (5-azadC) is a DNA methyltransferase (DNMT) inhibitor increasingly used in treatments of hematological diseases and works by being incorporated into DNA and trapping DNMT. It is unclear what DNA lesions are caused by 5-azadC and if such are substrates for DNA repair. Here, we identify that 5-azadC induces DNA damage as measured by γ-H2AX and 53BP1 foci. Furthermore, 5-azadC induces radial chromosomes and chromatid breaks that depend on active replication, which altogether suggest that trapped DNMT collapses oncoming replication forks into double-strand breaks. We demonstrate that RAD51-mediated homologous recombination (HR) is activated to repair 5-azadC collapsed replication forks. Fanconi anemia (FA) is a rare autosomal recessive disorder, and deaths are often associated with leukemia. Here, we show that FANCG-deficient cells fail to trigger HR-mediated repair of 5-azadC-induced lesions, leading to accumulation of chromatid breaks and inter-chromosomal radial fusions as well as hypersensitivity to the cytotoxic effects of 5-azadC. These data demonstrate that the FA pathway is important to protect from 5-azadC-induced toxicity. Altogether, our data demonstrate that cytotoxicity of the epigenetic drug 5-azadC can, at least in part, be explained by collapsed replication forks requiring FA-mediated HR for repair.

Méndez Zaballos, L. (2011). Prácticum de Psicología. La formación de profesionales en la enseñanza no presencial. Madrid: Sanz y Torres, S.L. y UNED / No disponible

No disponible

Coexistence of Langerhans cell histiocytosis, Rosai-Dorfman disease and splenic lymphoma with fatal outcome after rapid development of histiocytic sarcoma of the liver.

The coexistence of skin-limited Langerhans cell histiocytosis (LCH) and Rosai-Dorfman disease (RDD) is an exceptional finding. The association of lymphomas and histiocytosis is also infrequent. We report the case of a 68-year-old man which presented an exceptional association of cutaneous LCH and RDD and splenic marginal zone lymphoma. He was stable for few years. Suddenly, the patient was admitted into Hematology Department with a remarkable enlargement of spleen and liver without enlargement of lymphadenopathies or skin lesions flare. He died 24 h later despite treatment with systemic chemotherapy combined with prednisone. Pre-mortem biopsy showed infiltration with histiocytic sarcoma. We think that a transdifferentiation phenomenon could explain our case, although we could not show a clonal relationship between the cutaneous and the liver diseases. We also want to pay attention to the fact that a fast transformation to a more aggressive disease can occur long time after the presentation of the first lesion, a problem that stresses the importance of performing a close and permanent follow-up of these patients.

The DNA topoisomerase II catalytic inhibitor merbarone is genotoxic and induces endoreduplication.

In the last years a number of reports have shown that the so-called topoisomerase II (topo II) catalytic inhibitors are able to induce DNA and chromosome damage, an unexpected result taking into account that they do not stabilize topo II-DNA cleavable complexes, a feature of topo II poisons such as etoposide and amsacrine. Merbarone inhibits the catalytic activity of topo II by blocking DNA cleavage by the enzyme. While it was first reported that merbarone does not induce genotoxic effects in mammalian cells, this has been challenged by reports showing that the topo II inhibitor induces efficiently chromosome and DNA damage, and the question as to a possible behavior as a topo II poison has been put forward. Given these contradictory results, and the as yet incomplete knowledge of the molecular mechanism of action of merbarone, in the present study we have tried to further characterize the mechanism of action of merbarone on cell proliferation, cell cycle, as well as chromosome and DNA damage in cultured CHO cells. Merbarone was cytotoxic as well as genotoxic, inhibited topo II catalytic activity, and induced endoreduplication. We have also shown that merbarone-induced DNA damage depends upon ongoing DNA synthesis. Supporting this, inhibition of DNA synthesis causes reduction of DNA damage and increased cell survival.

Robertson, M. y Cavanna, A. (2010). El síndrome de Tourette, segunda edición, Alianza Editorial / No disponible

No disponible