The HUMN and HUMNxL international collaboration projects on human micronucleus assays in lymphocytes and buccal cells--past, present and future

Abstract

The International Human Micronucleus (HUMN) Project (www.humn.org) was founded in 1997 to coordinate worldwide research efforts aimed at using micronucleus (MN) assays to study DNA damage in human populations. The central aims were to (i) collect databases on baseline MN frequencies and associated methodological, demographic, genetic and exposure variables, (ii) determine those variables that affect MN frequency, (iii) establish standardised protocols for performing assays so that data comparisons can be made more reliably across laboratories and countries and (iv) evaluate the association of MN frequency with disease outcomes both cross-sectionally and prospectively. In the first 10 years of the HUMN project, all of these objectives were achieved successfully for the MN assay using the cytokinesis-block micronucleus (CBMN) assay in human peripheral blood lymphocytes and the findings were published in a series of papers that are among the most highly cited in the field. The CBMN protocol and scoring criteria are now standardised; the effect of age, gender and smoking status have been defined, and it was shown prospectively using a database of almost 7000 subjects that an increased MN frequency in lymphocytes predicts cancer risk. More recently in 2007, the HUMN coordinating group decided to launch an equivalent project focussed on the human MN assay in buccal epithelial cells because it provides a complementary method for measuring MN in a tissue that is easily accessible and does not require tissue culture. This new international project is now known as the human MN assay in exfoliated cells (HUMN(xL)). At present, a database for >5000 subjects worldwide has been established for the HUMN(xL) project. The inter-laboratory slide-scoring exercise for the HUMN(xL) project is at an advanced stage of planning and the analyses of data for methodological, demographic, genetic, lifestyle and exposure variables are at a final stage of completion. Future activities will be aimed at (i) defining the genetic variables that affect MN frequencies, (ii) validation of the various automated scoring systems based on image analysis, flow cytometry and laser scanning cytometry, (iii) standardisation of protocols for scoring micronuclei (MNi) in cells from other tissues, e.g. erythrocyte and nasal cells and (iv) prospective association studies with pregnancy complications, developmental defects, childhood cancers, cardiovascular disease and neurodegenerative diseases.

Genotoxicity Expert Panel review: weight of evidence evaluation of the genotoxicity of glyphosate, glyphosate-based formulations, and aminomethylphosphonic acid

“…Diet, disease status (e.g. presence of inflammatory diseases), seasonal variation, and physical stress are all important confounding factors that influence an individual's background level for any parameter under consideration (Moller 2005;Battershill et al 2008;Bonassi et al 2011;Fenech et al 2011;Tenorio et al 2013;Collins et al 2014). There is evidence that different factors may have different impact depending on the specific genotoxic endpoints (e.g.…”

“…There is evidence that different factors may have different impact depending on the specific genotoxic endpoints (e.g. Fenech et al 2011 for the cytokinesis block MN endpoint; Collins et al 2014 for the comet endpoint). It is worth noting that there is currently considerable debate concerning the relevance of increased levels of micronuclei in human biomonitoring studies.…”

Genotoxic potential of 10% and 16% Carbamide Peroxide in dental bleaching

“…16 Our MN levels at baseline were close to the lower value of the mean worldwide frequency found by Bonassi et al 16 In the present study, 1000 cells/individual were counted, although the literature suggests using a minimum of 2000 cells/individual. 17,18 The study evaluated the genotoxicity of a local agent, as is the case of the effect of bleaching gels on the cells of the gingival epithelium (stratified parakeratinized squamous epithelium). International recommendations (HUMN-XL) 18 suggest oral mucosa cells (non-keratinized stratified squamous tissue) for these assessments.…”

“…17,18 The study evaluated the genotoxicity of a local agent, as is the case of the effect of bleaching gels on the cells of the gingival epithelium (stratified parakeratinized squamous epithelium). International recommendations (HUMN-XL) 18 suggest oral mucosa cells (non-keratinized stratified squamous tissue) for these assessments. Cell exfoliation is easier to perform in the oral mucosa than in gingival tissue, where the number of exfoliated cells is much smaller than in the buccal mucosa; moreover, these tissues have different histological features.…”

Avaliação citogenética e molecular de trabalhadores intoxicados pelo benzeno

“…Este teste vem sendo utilizado como um biomarcador de eventos genotóxicos e de instabilidade cromossômica, desde que permite incluir alterações nucleares como pontes nucleoplasmáticas e brotos nucleares (Fenech et al, 2011a (Rekhadevi et al, 2010). A avaliação dos danos gerados ao material genético por agentes como o benzeno também pode ser realizada por meio do teste de CBMN em células da mucosa oral ou em outros tipos de células esfoliativas (Fenech et al, 2011b;Bonassi et al, 2011). Apesar de também não existir um consenso sobre a frequência de MN em amostras de células da mucosa oral e/ou células esfoliativas em avaliações de trabalhadores expostos ao benzeno, alguns estudos demonstraram aumento significativo na frequência de células com MN em trabalhadores expostos nas refinarias de petróleo, quando comparados aos controles (Celik et al, 2003;Singaraju et al, 2012 (Fenech, 1998 (Vigliani e Saita, 1964;Vigliani e Forni, 1976;Aksoy, 1971Aksoy, e 1989.…”