Exfoliated Cells MN Project

Genoa, 6 March 2008.

Dear colleague,

Over the last five years, the number of laboratories working with the micronucleus (MN) assay in exfoliated cells such as buccal, urothelial, nasal epithelia has substantially increased. Many research groups are interested in this approach because exfoliated cells hold strong potential as a tool for biomonitoring human populations at risk of genotoxic damage.

Collection of exfoliated buccal cells is a less invasive method available for measuring DNA damage in humans especially in comparison to collection of blood samples for lymphocyte and erythrocyte assays. The exfoliated buccal cell MN assay, was first proposed in 1983 and continues to gain popularity as a biomarker of genetic damage in numerous applications.   

Different issues related to the buccal cell MN assays were reviewed in several publications over the last decade, but despite the large number of papers, there are several important issues concerning the protocols and other issues that still need to be addressed. Our knowledge about effects of genotoxic agents on this biomarker is limited to a few substances (e.g. smoking, smokeless tobacco, formaldehyde, pesticides, cytostatic drugs, and ionizing radiation). The relative importance of the confounding variables that could affect MN frequency in buccal cells has not been adequately quantified. Furthermore, the assay protocol and scoring criteria have not been standardized in such a way that results from different laboratories can be easily compared, and the statistical analyses of data in many of the publications is seldom appropriate. Finally, the predictive value of the buccal MN frequency for disease risk has not been studied in a comprehensive manner.

After the successful experience obtained with the international collaborative project on Micronucleus Frequency in Human Populations (HUMN) that examined the MN frequency in peripheral blood lymphocytes, we  are initiating a new project that will focus on the MN assay in exfoliated buccal cells. The gaps of knowledge regarding this assay were discussed at the 8th HUMN project workshop (Antalya, Turkey, May 2007) and are detailed in a workshop report (submitted for publication) and in the commentary recently published by the HUMN committee (Fenech et al, 2007, Mutagenesis). A position paper by the coordinating group about the buccal cell MN assay and proposed new HUMN validation project has been accepted for publication in the upcoming special issue of the Mutation Research Reviews. Copies of the report, commentary and review will be forwarded to all HUMN participants and will be available at the HUMN website. 

The specific aims of the new HUMN project, characterized by a novel acronym which includes XL to remember the focus on eXfoLiated cells (i.e., HUMNXL) (and hopefully to describe the size of the study !!), include:

1) Comparison and standardization of the protocol of buccal cell collection, processing, staining and scoring. The results will be used to establish an internationally acceptable procedure that will enable comparison of results among laboratories and across countries;
2) Comparison of spontaneous and induced MN levels. This comparison will provide information on the extent to which there is agreement on the key variables (e.g. age, sex, smoking) that affect the base-line MN frequencies in buccal cells;
3) Evaluation of MN as a biomarker of cancer risk in epithelial buccal tissue, which will require a prospective study linking MN index with cancer risk, mortality and life-span.

The HUMNXL project is a promising vehicle for an international collaborative effort to bring together the various databases, and to analyze and quantify the key variables affecting this biomarker  in a specially designed validation project.  In addition, an inter-laboratory slide-scoring exercise is planned to evaluate the reproducibility of the staining and scoring of buccal exfoliated cell MN within and across laboratories, similar to the approach successfully used by the HUMN project for the MN assay in lymphocytes.

The initial work plan is aimed at collecting information about the most frequently used protocols in the laboratories that have published their results in reputable, peer-reviewed journals. Before a laboratory can be included in the project, all information in its questionnaire will be carefully evaluated by the HUMNXL project steering committee.

Several labs already expressed their interest in the partecipation in HUMNXL project initiative. To assess the extent of interest in such a collaboration, please complete the brief questionnaire attached to this letter and return it to us within 30 days of receiving this letter. Please send the completed questionnaire to:

to:

           Stefano Bonassi, PhD
           Unit of Molecular Epidemiology
           National Cancer Research Institute
           Largo Rosanna Benzi, 10
           I-16132 Genova, Italy

            or fax it to the following number: +39-010-5600501

            or just send the questionnaire as an attachment to: stefano.bonassi@istge.it 

    Please share this invitation with your colleagues who may be interested in the project.

    If you want additional information about this HUMN  project you can contact any member of the coordinating group indicated below, or visit the site www.humn.org where all HUMN publications are available (70 different researchers from 30 countries co-authored these papers !!).

    Thank you for your attention

    Yours,

    To download this invitation letter, please click here.

    Please contact Dr. Nina Holland at ninah@uclink.berkeley.edu for any additional information on exfoliated buccal cell assays.