Stopper, H. (Helga)
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- Minimum Information for Reporting on the Comet Assay (MIRCA): recommendations for describing comet assay procedures and results(2020) Stopper, H. (Helga); Boutet-Robinet, E. (Elisa); Langie, S.A.S. (Sabine A. S.); Collins, A. (Andrew); Cooke, M.S. (Marcus S.); Sramkova, M. (Monika); Richling, E. (Elke); Moraes-de-Andrade, V. (Vanessa); Novak, M. (Matjaz); Del-Bo, C. (Cristian); Koppen, G. (Gudrun); Godschalk, R. (Roger); Bonassi, S. (Stefano); Costa, S. (Solange); Teixeira, J.P. (Joao Paulo); Gützkow, K.B. (Kristine Bjerve); Gajski, G. (Goran); Costa-Pereira, C. (Cristiana); Møller, P. (Peter); Dusinska, M. (Maria); Laffon, B. (Blanca); Milic, M. (Mirta); Giovannelli, L. (Lisa); Vodicka, P. (Pavel); Zegura, B. (Bojana); Vodenkova, S. (Sona); Azqueta, A. (Amaya); Brunborg, G. (Gunnar); Valdiglesias, V. (Vanessa); Gabelova, A. (Alena); Basaran, N. (Nursen)The comet assay is a widely used test for the detection of DNA damage and repair activity. However, there are interlaboratory differences in reported levels of baseline and induced damage in the same experimental systems. These differences may be attributed to protocol differences, although it is difficult to identify the relevant conditions because detailed comet assay procedures are not always published. Here, we present a Consensus Statement for the Minimum Information for Reporting Comet Assay (MIRCA) providing recommendations for describing comet assay conditions and results. These recommendations differentiate between ‘desirable’ and ‘essential’ information: ‘essential’ information refers to the precise details that are necessary to assess the quality of the experimental work, whereas ‘desirable’ information relates to technical issues that might be encountered when repeating the experiments. Adherence to MIRCA recommendations should ensure that comet assay results can be easily interpreted and independently verified by other researchers.
- Potassium bromate as positive assay control for the Fpg-modified comet assay(Oxford University Press, 2020) Stopper, H. (Helga); Langie, S.A.S. (Sabine A. S.); Scavone, F. (Francesca); Bankoglu, E.E. (Ezgi Eyluel); Kruszewski, M. (Marcin); Wojewódzka, M. (Maria); Jensen, A. (Annie); Marino, M. (Mirko); Richling, E. (Elke); Bakuradze, T. (Tamara); Muruzábal, D. (Damián); Riso, P. (Patrizia); Del-Bo, C. (Cristian); Möller, P. (Peter); Shaposhnikov, S. (Sergey); Costa, S. (Solange); Teixeira, J.P. (Joao Paulo); Laffon, B. (Blanca); Giovannelli, L. (Lisa); Costa, C. (Carlos); Azqueta, A. (Amaya); Valdiglesias, V. (Vanessa); Collins, A. (A.)The comet assay is a popular assay in biomonitoring studies. DNA strand breaks (or unspecific DNA lesions) are measured using the standard comet assay. Oxidative stress-generated DNA lesions can be measured by employing DNA repair enzymes to recognise oxidatively damaged DNA. Unfortunately, there has been a tendency to fail to report results from assay controls (or maybe even not to employ assay controls). We believe this might have been due to uncertainty as to what really constitutes a positive control. It should go without saying that a biomonitoring study cannot have a positive control group as it is unethical to expose healthy humans to DNA damaging (and thus potentially carcinogenic) agents. However, it is possible to include assay controls in the analysis (here meant as a cryopreserved sample of cells i.e. included in each experiment as a reference sample). In the present report we tested potassium bromate (KBrO3) as a positive comet assay control for the formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay. Ten laboratories used the same procedure for treatment of monocytic THP-1 cells with KBrO3 (0.5, 1.5 and 4.5 mM for 1 h at 37°C) and subsequent cryopreservation. Results from one laboratory were excluded in the statistical analysis because of technical issues in the Fpg-modified comet assay. All other laboratories found a concentration–response relationship in cryopreserved samples (regression coefficients from 0.80 to 0.98), although with different slopes ranging from 1.25 to 11.9 Fpg-sensitive sites (%DNA in tail) per 1 mM KBrO3. Our results demonstrate that KBrO3 is a suitable positive comet assay control.
- Do cytotoxicity and cell death cause false positive results in the in vitro comet assay?(Elsevier, 2022) Stopper, H. (Helga); Møller, P. (Peter); Dusinska, M. (Maria); Zegura, B. (Bojana); Azqueta, A. (Amaya)The comet assay is used to measure DNA damage induced by chemical and physical agents. High concentrations of test agents may cause cytotoxicity or cell death, which may give rise to false positive results in the comet assay. Systematic studies on genotoxins and cytotoxins (i.e. non-genotoxic poisons) have attempted to establish a threshold of cytotoxicity or cell death by which DNA damage results measured by the comet assay could be regarded as a false positive result. Thresholds of cytotoxicity/cell death range from 20% to 50% in various publications. Curiously, a survey of the latest literature on comet assay results from cell culture studies suggests that one-third of publications did not assess cytotoxicity or cell death. We recommend that it should be mandatory to include results from at least one type of assay on cytotoxicity, cell death or cell proliferation in publications on comet assay results. A combination of cytotoxicity (or cell death) and proliferation (or colony forming efficiency assay) is preferable in actively proliferating cells because it covers more mechanisms of action. Applying a general threshold of cytotoxicity/cell death to all types of agents may not be applicable; however, 25% compared to the concurrent negative control seems to be a good starting value to avoid false positive comet assay results. Further research is needed to establish a threshold value to distinguish between true and potentially false positive genotoxic effects detected by the comet assay.