Combined analysis of chromosomal aberrations and glutathione S-transferase M1 and T1 polymorphisms in pathologists occupationally exposed to formaldehyde.

The formaldehyde (FA) genotoxic potential in occupationally exposed individuals is conflicting. A relevant indoor-air FA pollution was found in hospitals and scientific institutions where FA is used as a bactericide and tissue preservative. In the present study, we evaluated the frequency of chromosomal aberrations (CAs) in peripheral blood lymphocytes from workers in pathology wards who have been exposed to FA, compared with a group of unexposed subjects. The subjects were also analyzed for the GSTM1 and GSTT1 metabolic gene polymorphisms. The exposed subjects showed a significant increase in the frequency of CA per cell and in the percentage of cells with aberrations compared to control subjects. The different GST genotypes did not affect the level of cytogenetic damage since CA frequencies were not statistically different between the GST "null" genotypes and the GST "positives". The generalized linear models showed that the number of CAs and cells with CAs increased with age, but, independent of age, it was significantly higher in the experimental rather than in the control group. Cubic-spline regression confirmed the linear relationship between CAs and age, but it provided evidence for a non-linear relationship between CAs and the number of years of FA exposure. Similar results were observed when the model included the number of cells with CAs as dependent variables. Our results demonstrate that air FA induces CAs even consequently to low levels of daily exposure, indicating an increased risk of genetic damage for workers exposed to this air pollutant.

Analysis of glutathione S-transferase M1 and glutathione S-transferase T1 gene polymorphisms suggests age-related relationships in a northern Italian population.

The present work attempts to determine the distribution of GSTM1 and GSTT1 genotype and allele frequencies in a sample of northern Italian population, and to examine the age-related association of these polymorphisms. The frequencies of the deleted GSTM1 and GSTT1 genotypes were 0.357 and 0.169, respectively. GSTT1 null-genotype frequency found in this work further confirms data obtained in previous studies of Italian populations, while for GSTM1 deletion our sample showed a significantly lower-frequency value with respect to other Italian and European populations, with exception of the Greek. No significant differences occurred between men and women in the frequency of each gene, which could suggest that, in the studied sample, there were no sex differences in susceptibility to diseases and in detoxifying enzymes such as GSTs. In order to analyze the relationship between GSTT1 and GSTM1 gene polymorphisms and age, the sample was subdivided into four age groups: 1-30 years (n = 101); 31-50 years (n = 160); 51-79 years (n = 144) and 80-100 years (n = 58). This age-related analysis showed a decreasing gradient of GSTs null genotypes between younger and older groups, with the 80-100 age group showing a significantly lower frequency of GSTT1 null, GSTM1 null and GSTT1/GSTM1 double null genotypes with respect to the younger group.

Allelic frequencies at the ACE and LRPAP1 loci suggest age-related relationships in a northern Italian population.

The present work attempts to determine the distribution of ACE and LRPAP1 genotypes and allele frequencies in a sample of the population of north-western Italy and to examine the age-related association of these polymorphisms. ACE D allele frequency found in this work further confirms data obtained in previous studies of Northern Italian populations. Regarding the LRPAP1 gene, high frequencies of the deleted allele in European populations were also confirmed. In order to analyse the relationship between ACE and LRPAP1 gene polymorphisms and age, the sample was subdivided into four age groups: 1-30 (n= 99), 31-50 (n= 165), 51-79 (n= 146) and 80-100 years old (n= 57). For the ACE gene, significant difference in D/D genotype frequency was found only between the younger and the 51-79 age groups (p<0.05), the latter showing the lower frequency value. Significant differences were found, for both the I/D and D/D LRPAP1 genotypes, between the first and the second age group (p < 0.02) and between the first and the third age group (p < 0.01), with the 51-79 age group showing the higher D/D and the lower I/D genotype frequency values.

An increased micronucleus frequency in peripheral blood lymphocytes predicts the risk of cancer in humans.

The frequency of micronuclei (MN) in peripheral blood lymphocytes (PBL) is extensively used as a biomarker of chromosomal damage and genome stability in human populations. Much theoretical evidence has been accumulated supporting the causal role of MN induction in cancer development, although prospective cohort studies are needed to validate MN as a cancer risk biomarker. A total of 6718 subjects from of 10 countries, screened in 20 laboratories for MN frequency between 1980 and 2002 in ad hoc studies or routine cytogenetic surveillance, were selected from the database of the HUman MicroNucleus (HUMN) international collaborative project and followed up for cancer incidence or mortality. To standardize for the inter-laboratory variability subjects were classified according to the percentiles of MN distribution within each laboratory as low, medium or high frequency. A significant increase of all cancers incidence was found for subjects in the groups with medium (RR=1.84; 95% CI: 1.28-2.66) and high MN frequency (RR=1.53; 1.04-2.25). The same groups also showed a decreased cancer-free survival, i.e. P=0.001 and P=0.025, respectively. This association was present in all national cohorts and for all major cancer sites, especially urogenital (RR=2.80; 1.17-6.73) and gastro-intestinal cancers (RR=1.74; 1.01-4.71). The results from the present study provide preliminary evidence that MN frequency in PBL is a predictive biomarker of cancer risk within a population of healthy subjects. The current wide-spread use of the MN assay provides a valuable opportunity to apply this assay in the planning and validation of cancer surveillance and prevention programs.

Intra- and inter-laboratory variation in the scoring of micronuclei and nucleoplasmic bridges in binucleated human lymphocytes. Results of an international slide-scoring exercise by the HUMN project.

One of the objectives of the HUman MicroNucleus (HUMN) project is to identify the methodological variables that have an important impact on micronucleus (MN) or micronucleated (MNed) cell frequencies measured in human lymphocytes using the cytokinesis-block micronucleus assay. In a previous study we had shown that the scoring criteria used were likely to be an important variable. To determine the extent of residual variation when laboratories scored cells from the same cultures using the same set of standard scoring criteria, an inter-laboratory slide-scoring exercise was performed among 34 laboratories from 21 countries with a total of 51 slide scorers involved. The results of this study show that even under these optimized conditions there is a great variation in the MN frequency or MNed cell frequency obtained by individual laboratories and scorers. All laboratories ranked correctly the MNed cell frequency in cells from cultures that were unirradiated, or exposed to 1 or 2Gy of gamma rays. The study also estimated that the intra-scorer median coefficient of variation for duplicate MNed cell frequency scores is 29% for unexposed cultures and 14 and 11% for cells exposed to 1 and 2Gy, respectively. These values can be used as a standard for quality or acceptability of data in future studies. Using a Poisson regression model it was estimated that radiation dose explained 67% of the variance, while staining method, cell sample, laboratory, and covariance explained 0.6, 0.3, 6.5, and 25.6% of the variance, respectively, leaving only 3.1% of the variance unexplained. As part of this exercise, nucleoplasmic bridges were also estimated by the laboratories; however, inexperience in the use of this biomarker of chromosome rearrangement was reflected in the much greater heterogeneity in the data and the unexplained variation estimated by the Poisson model. The results of these studies indicate clearly that even after standardizing culture and scoring conditions it will be necessary to calibrate scorers and laboratories if MN, MNed cell and nucleoplasmic bridge frequencies are to be reliably compared among laboratories and among populations.