Mortality among workers exposed to asbestos at the shipyard of Genoa, Italy: a 55 years follow-up.

BACKGROUND: Exposure to asbestos remains a global issue due to its massive use in the twentieth century and its long environmental persistence. Exposure to asbestos still occurs during dismantling of ships and vessels, buildings renovation, mining operations, and is reported in developing countries. Current estimate report exposure of hundreds of million people in occupational settings in countries where its use remains unregulated. METHODS: We conducted a historical prospective cohort mortality study aimed at estimating mortality from specific causes, the temporal changes of pleural and lung cancer mortality, and the attributable fraction (AF) of lung cancer deaths following asbestos exposure. The study included 3984 shipyard workers employed at the shipyard of Genoa, Italy, between 1960 and 1981 and followed up to December 2014. Standardized Mortality Ratios (SMR) and their 95% confidence intervals (95%CI) were computed. RESULTS: Overall deaths recorded were 3331 (83.6%). Excess mortality was observed for all cancers (SMR = 127, 95%CI:120-134), pleural mesothelioma (575, 469-697), cancers of the larynx (183, 134-244) and of the lung (154, 139-170), and for respiratory tract diseases (127, 114-141), including asbestosis (2277, 1525-3270). Ninety out of 399 deaths (22.6%) from lung cancer were attributed to asbestos exposure. The estimated lung cancer AF was 49.3% in workers with the highest SMR for pleural cancer. Median latency times for pleural and lung cancer were 42.8 years (minimum latency: 9.3 years) and 38.7 years (minimum latency: 6 years). The peak of mesothelioma incidence, expected in Italy in the period 2015-2024, was confirmed. CONCLUSIONS: The long follow-up period of our study allowed the detection of a substantial disease burden following asbestos exposure. These findings support the urgent need for the prevention of asbestos related diseases through the implementation of asbestos ban worldwide, including those countries where asbestos is still mined, manufactured and used.

Effects of cigarette smoking on circulating leukocytes and plasma cytokines in monozygotic twins.

BACKGROUND: Despite the well-documented role of cigarette smoke in the development of chronic obstructive pulmonary disease (COPD), lung cancer and cardiovascular disease, biomarkers for screening or monitoring disease progression and outcome remain elusive, particularly for COPD and lung cancer. Inflammatory cells and mediators are likely to be involved in the disease processes, but their importance is still poorly understood. The purpose of this study was to investigate early changes in immunological markers associated with smoking in healthy monozygotic twins without a detectable disease discordant for smoking, thereby minimising data variability due to genetic background. METHODS: Twenty-two monozygotic twin pairs, aged 31.5±6.3 years, entered the study. One of each twin pair was a smoker and the other a non-smoker. None of the subjects reported any diseases or clinically defined respiratory symptoms or airflow limitation. Each subject donated blood samples for determination of total leukocytes and subpopulations, lymphocyte subpopulation plus pro-inflammatory mediators (interleukin-8, tumour necrosis factor-α, soluble tumour necrosis factor-α receptors and C-reactive protein). RESULTS: We observed a significant increase in the number of circulating leukocytes and neutrophils in smokers compared to non-smokers. Smokers also had significantly higher numbers of B cells and CD4+ T cells, plus an increased CD4/CD8 ratio. The numbers of NK cells were statistically significant lower in smokers compared to non-smokers. CONCLUSIONS: While the prognostic significance of these changes is uncertain, results suggest that smoking is associated with immune changes, independent of genetic background and environmental conditions.

Cross-sectional study of biomarkers of exposure and biological effect on monozygotic twins discordant for smoking.

BACKGROUND: The aim of this study was to investigate the possible correlation between smoking status and biomarkers of exposure (BoE) and biological effect (BoBE) in monozygotic twins discordant for smoking status (smoker and non-smoker pairs). By eliminating potential genetic variability in this manner, a clearer pattern of the effects of lifestyle and environmental exposures should become apparent. METHODS: This was a cross-sectional study on monozygotic healthy twins (44 subjects, 26 males and 18 females) with a mean age 31.5 years. BoE to cigarette smoke and BoBE were measured in body fluids (24 h urine and blood) after medical pre-screening. RESULTS: All BoE were significantly higher in the smoker twins. Among BoBE, 11-dehydrothromboxane B(2) (11-dehydro TBX), 2,3-dinorthromboxane B(2) (2,3-dinor TBX), 8-epi-prostaglandin F2α (8-epiPGF), hydroxyproline (OH-P), fibrinogen, white blood cell (WBC), neutrophil and lymphocyte counts and heart rate were statistically significantly increased in the smoker compared to the non-smoker twins. Moreover, statistically significant correlations between neutrophil count and 11-dehydro TBX (r=0.32), WBC and 8-epiPGF (r=0.33), OH-P and 8-epiPGF (r=0.49) and heart rate and fibrinogen (r=0.46) were observed. CONCLUSIONS: The study results confirmed the reliability of the BoE for the evaluation of smoking status. Moreover, a subset of the BoBE, reported as being associated with inflammatory conditions and early stages of vascular disorders, has emerged as showing a consistent relationship with smoking status from the present and the previous studies. By using monozygotic twin pairs, genetic variability has been excluded as a possible source of variability in this study. These results should assist in the interpretation of other population studies using these biomarkers.

Smoking, DNA adducts and number of risk DNA repair alleles in lung cancer cases, in subjects with benign lung diseases and in controls.

Smoke constituents can induce DNA adducts that cause mutations and lead to lung cancer. We have analyzed DNA adducts and polymorphisms in two DNA repair genes, for example, XRCC1 Arg194Trp and Arg399Gln genes and XRCC3 Thr241Met gene, in 34 lung cancer cases in respect to 30 subjects with benign lung cancer disease and 40 healthy controls. When the study population was categorized in base to the number of risk alleles, adducts were significantly increased in individuals bearing 3-4 risk alleles (OR = 4.1 95% C.I. 1.28-13.09, P = .009). A significant association with smoking was noticed in smokers for more than 40 years carrying 3-4 risk alleles (OR = 36.38, 95% C.I. 1.17-1132.84, P = .040). A not statistically significant increment of lung cancer risk was observed in the same group (OR = 4.54, 95% C.I. 0.33-62.93, P = .259). Our results suggest that the analysis of the number of risk alleles predicts the interindividual variation in DNA adducts of smokers and lung cancer cases.

Duration of exposure to environmental carcinogens affects DNA-adduct level in human lymphocytes.

BACKGROUND AND OBJECTIVE: An important issue in human biomonitoring is determining how exposure duration affects the kinetics of molecular biomarkers. In this study we compare the influence of exposure variables on DNA adducts. METHODS: DNA adducts were analysed by 32P-postlabelling in lympho/monocytes of 677 Caucasian subjects. RESULTS: After correction for other variables, DNA adducts increased depending on the length of occupational and smoke exposures. Higher DNA adducts were detected in workers with more than 14 years of exposure than in workers with shorter exposures (RR = 1.19, p = 0.049) and in smokers with more than 10 years of exposure than in smokers with shorter exposure (RR = 1.21, p <0.001). CONCLUSIONS: Exposure length is the primary factor affecting DNA-adduct level in lympho/monocytes both in smokers and in occupationally exposed subjects.

A cross-sectional investigation of biomarkers of risk after a decade of smoking.

Two groups of 20 healthy volunteers with cigarettes of different tar yield were compared with a group of 20 never smokers over 24 h for several biomarkers. All groups were of similar mean ages and the smokers had smoked for a homogeneous period of approximately 10 yr. The groups were assessed using routine medical parameters as well as biomarkers of recent smoke exposure and other biomarkers that were under evaluation as possible markers of risk for smoking-associated diseases. All biomarkers of exposure-carbon monoxide, nicotine plus its five major metabolites, and 4-(methylnitrosamine)-1-(3-pyridyl)-1-butanol (NNAL)-were significantly elevated in smokers. For biomarkers of potential risk evaluated in the blood, white cells and immunoglobulin (Ig) G showed a decrease related to smoking status (p < .01). Interleukin 6 levels were higher in smoker groups compared to never smokers, with a significant increasing trend across the groups (p < .05). Among the urinary biomarkers studied, 11-deydro-thromboxane B2, 2,3-dinor-thromboxane B2, and thymidine glycol showed significant increasing trends across the groups (p < .01). The results suggest that after the first decade or less of smoking, changes in inflammatory, immunological, and cardiovascular function can be observed. However, further studies on larger groups will be required to better understand the kinetics of these subtle effects observed early in smokers and their relationship with the potential risk of subsequent smoking-associated disease.

Estrogen receptor-beta affects the prognosis of human malignant mesothelioma.

Malignant pleural mesothelioma is an asbestos-related neoplasm with poor prognosis, refractory to current therapies, the incidence of which is expected to increase in the next decades. Female gender was identified as a positive prognostic factor among other clinical and biological prognostic markers for malignant mesothelioma, yet a role of estrogen receptors (ERs) has not been studied. Our goal was to investigate ERs expression in malignant mesothelioma and to assess whether their expression correlates with prognosis. Immunohistochemical analysis revealed intense nuclear ERbeta staining in normal pleura that was reduced in tumor tissues. Conversely, neither tumors nor normal pleura stained positive for ERalpha. Multivariate analysis of 78 malignant mesothelioma patients with pathologic stage, histologic type, therapy, sex, and age at diagnosis indicated that ERbeta expression is an independent prognostic factor of better survival. Moreover, studies in vitro confirmed that treatment with 17beta-estradiol led to an ERbeta-mediated inhibition of malignant mesothelioma cell proliferation as well as p21(CIP1) and p27(KIP1) up-regulation. Consistently cell growth was suppressed by ERbeta overexpression, causing a G(2)-M-phase cell cycle arrest, paralleled by cyclin B1 and survivin down-regulation. Our data support the notion that ERbeta acting as a tumor suppressor is of high potential relevance to prediction of disease progression and to therapeutic response of malignant mesothelioma patients.

Cardiovascular biomarkers in groups of established smokers after a decade of smoking.

To investigate tools for evaluation of smoking-associated disease initiation and progression, we examined basic clinical parameters and biomarkers of cardiovascular disease risk, in a group of healthy volunteers with an average 10-year smoking history. A small cross-sectional study of never-smokers, moderate smokers and smokers was performed. Caucasians were recruited to match pre-defined cigarette tar yields and cigarettes smoked per day. For haematological parameters, significant differences between never-smokers and all female smokers combined were seen for haemoglobin concentration, haematocrit, total leucocyte count, neutrophil count and lymphocyte count. For all male smokers combined, only total leucocyte count was statistically different. Analysis of exhaled CO and other smoke exposure biomarker (nicotine and its metabolites) data showed a statistically significant increase in all groups of smokers with a trend related to the number of cigarettes smoked per day. Thromboxane urinary metabolites 11-dehydro-thromboxane B(2) and 2,3-dinor-thromboxane B(2) were statistically significantly elevated in smokers. Significant statistical differences between smokers with approximately 10 years of smoking history and non-smokers in white cells count, hemoglobin and thromboxane turnover were seen, although they did not reach levels associated with overt diseases. These data could provide insight into early biomarkers predictive of risk for coronary and vascular disease.

The CREST biorepository: a tool for molecular epidemiology and translational studies on malignant mesothelioma, lung cancer, and other respiratory tract diseases.

OBJECTIVES: The Cancer of RESpiratory Tract (CREST) biorepository was established to investigate biological mechanisms and to develop tools and strategies for primary and secondary prevention of respiratory tract cancer. The CREST biorepository is focused on pleural malignant mesothelioma, a rare and severe cancer linked to asbestos exposure whose incidence is particularly high in the Ligurian region. METHODS: The CREST biorepository includes biological specimens from (a) patients with pleural malignant mesothelioma and lung cancer, (b) patients with nonneoplastic respiratory conditions, and (c) control subjects. Whole blood, plasma, serum, lymphocytes, pleural fluid, saliva, and biopsies are collected, and a questionnaire is administered. Collection, transportation, and storage are done according to international standards. RESULTS: As of January 31, 2008, the overall number of subjects recruited was 1,590 (446 lung cancer, 209 pleural malignant mesothelioma, and 935 controls). The biorepository includes a total of 10,055 aliquots (4,741 serum; 3,082 plasma; 1,599 whole blood; 633 pleural fluid; and 561 lymphocytes) and 107 biopsies. Demographic, clinical, and epidemiologic information is collected for each subject and processed in a dedicated database. CONCLUSIONS: The CREST biorepository is a valuable tool for molecular epidemiology and translational studies. This structure relies on a network of contacts with local health districts that allows for an active search for patients. This is a particularly efficient approach, especially when the object of the study is a rare cancer type. The CREST experience suggests that the presence of limited resources can be overcome by the biorepository specialization, the high quality of the epidemiologic information, and the variety of samples.

Genetic susceptibility to malignant pleural mesothelioma and other asbestos-associated diseases.

Exposure to asbestos fibers is a major risk factor for malignant pleural mesothelioma (MPM), lung cancer, and other non-neoplastic conditions, such as asbestosis and pleural plaques. However, in the last decade many studies have shown that polymorphism in the genes involved in xenobiotic and oxidative metabolism or in DNA repair processes may play an important role in the etiology and pathogenesis of these diseases. To evaluate the association between diseases linked to asbestos and genetic variability we performed a review of studies on this topic included in the PubMed database. One hundred fifty-nine citations were retrieved; 24 of them met the inclusion criteria and were evaluated in the review. The most commonly studied GSTM1 polymorphism showed for all asbestos-linked diseases an increased risk in association with the null genotype, possibly linked to its role in the conjugation of reactive oxygen species. Studies focused on GSTT1 null and SOD2 Ala16Val polymorphisms gave conflicting results, while promising results came from studies on alpha1-antitrypsin in asbestosis and MPO in lung cancer. Among genetic polymorphisms associated to the risk of MPM, the GSTM1 null genotype and two variant alleles of XRCC1 and XRCC3 showed increased risks in a subset of studies. Results for the NAT2 acetylator status, SOD2 polymorphism and EPHX activity were conflicting. Major limitations in the study design, including the small size of study groups, affected the reliability of these studies. Technical improvements such as the use of high-throughput techniques will help to identify molecular pathways regulated by candidate genes.

Genetic susceptibility to malignant mesothelioma and exposure to asbestos: the influence of the familial factor.

BACKGROUND: Asbestos is the principal etiological factor of malignant mesothelioma (MM), accounting for more than 80% of all tumor cases. However, other co-factors, including genetic susceptibility may play a role in the etiology of this disease, possibly modulating the effects of exposure to asbestos and other carcinogenic mineral fibers. The frequent report of familial clustering was the first indication supporting the involvement of genetic factors. Therefore, we performed an extensive literature search to evaluate existing studies reporting familial cases of MM. METHODS: Published reports addressing the issue of familial susceptibility to MM have been searched through PubMed using keywords and free text tools. Eighty-two citations were retrieved and 20 of them actually reported a familial cluster of MM. Three more articles were identified through the references. The probability that the observed familial clusters of mesothelioma could have randomly occurred in exposed families was evaluated with the Family History Score Zi (FHSi). RESULTS: The result of this analysis suggested that clustering of MM cases in families exposed to asbestos may be explained with the additional contribution of other familial factors. The FHSi allowed to reject the hypothesis of random occurrence of these clusters with a probability of a first type error ranging between 1 per cent and 1 per billion. CONCLUSIONS: The evaluation of the published materials supports the hypothesis that - although familial clustering of MM is largely attributable to shared asbestos exposure - the additional contribution of factors dealing with genetic susceptibility may play a role in the etiology of MM.

Clinical significance of serum mesothelin in patients with mesothelioma and lung cancer.

PURPOSE: High levels of serum-soluble mesothelin family proteins (SMRP) have been found to be associated with malignant mesothelioma (MM), but not lung cancer (LC). To verify the clinical role of this marker for both these tumors, we tested serum SMRP in the largest population of thoracic cancers ever assembled. EXPERIMENTAL DESIGN: SMRP blood concentrations were measured in 107 patients with MM, 215 patients with LC, 130 patients with benign respiratory diseases (BRD), and 262 controls. Statistical comparison between mean serum SMRP levels in all groups was done and receiver operating characteristic curves were constructed to evaluate the performance of this marker. RESULTS: SMRP levels were significantly higher in patients with MM and LC than in patients with benign respiratory diseases and controls (P < 0.001). The area under the receiver operating characteristic curve for serum SMRP discriminating MM and controls was 0.77 (95% confidence interval, 0.71-0.83), with a best cutoff of 1.00 nmol/L (sensitivity, 68.2%; specificity, 80.5%). In both MM and LC, serum SMRP levels did not differ significantly between early and late stages. High SMRP levels proved to be an independent negative prognostic factor in patients with MM. CONCLUSIONS: Our data confirm that serum SMRP is a promising marker for the diagnosis, prognosis, and clinical monitoring of MM. We found that serum SMRP dosage may prove helpful in LC diagnosis as well. These data may also have positive repercussions on secondary preventive medical strategies for workers previously exposed to asbestos.

A bibliometric analysis of scientific production in cancer molecular epidemiology.

OBJECTIVES: The main purpose of this research was to compare the scientific production in the field of cancer molecular epidemiology among countries and to evaluate the publication trend between 1995 and 2004. METHODS: A bibliometric study was carried out searching the PubMed database with a combined search strategy based on the keywords listed in the medical subject headings and a free text search. Only articles from a representative subset of 92 journals--accounting for 80% of papers identified--were selected for the analysis, and the resulting 13,240 abstracts were manually checked according to a list of basic inclusion criteria. The study evaluated the number of publications and the impact factor (mean and sum), absolute and normalized by country population and gross domestic product. RESULTS: A total of 3,842 citations were finally selected for the analysis. Thirty-seven percent came from the European Union (UK, Germany, Italy, France and Sweden ranking at the top), 31.6% from USA and 9.7% from Japan. The highest mean impact factor was reported for Canada (6.3), USA (5.9), Finland (5.8) and UK (5.2). Finland, Sweden and Israel had the best ratio between scientific production and available resources. 'Genetic polymorphism, glutathione transferase, breast neoplasm, risk factors, case-control studies and polymerase chain reaction' were the most used keywords in each of the subgroups evaluated, although inclusion criteria may have privileged studies dealing with exogenous carcinogens. CONCLUSION: Cancer molecular epidemiology is an expanding area attracting an increasing interest. The identification of an operative definition is a necessary condition to give to this discipline a unique scientific identity.

Polymorphisms of glutathione-S-transferase M1 and manganese superoxide dismutase are associated with the risk of malignant pleural mesothelioma.

Individual response to oxidative stress, due to exposure to asbestos fibres plays a significant role in the malignant pleural mesothelioma (MPM) etiology. The differential impact on MPM risk of polymorphic alleles of glutathione-S-transferases (GSTs) and manganese superoxide dismutase (MnSOD/SOD2) genes involved in the defence against oxidative damage has been investigated. Ninety cases of MPM and 395 controls were genotyped using the arrayed-primer extension technique. Logistic regression analysis was applied to assess the predictive role of single nucleotide polymorphisms (SNPs) potentially involved in MPM carcinogenesis after adjustment for potential confounders. An increased risk of MPM was found in subjects bearing a GSTM1 null allele (OR = 1.69, 95% CI = 1.04-2.74; p = 0.034), and in those with the Ala/Ala genotypes at codon 16 within MnSOD (OR = 3.07, 95% CI = 1.55-6.05; p = 0.001). A stronger effect of MnSOD was observed among patients without a clear exposure to asbestos fibres. No effect was found for GSTA2, GSTA4, GSTM3, GSTP1 and GSTT1 genes. These findings, if replicated, contribute substantial evidence to the hypothesis that oxidative stress and cellular antireactive oxygen species systems are involved in the pathogenesis and in the natural history of MPM.

Evidence of gene gene interactions in lung carcinogenesis in a large pooled analysis.

To test the hypothesis of interaction among genetic variants in increasing the individual risk of cancer, we have studied the cumulative effect on lung cancer risk of variants in three metabolic genes, CYP1A1, GSTM1 and GSTT1, which are involved in the metabolism of the tobacco smoke constituents and environmental contaminants, polycyclic aromatic hydrocarbons and of other lung carcinogens. We have selected from the Genetic Susceptibility to Environmental Carcinogens pooled analysis all the studies on lung cancer conducted after 1991 in which all variants were available. The data set includes 611 cases and 870 controls. We found a cumulative effect of the combination of the a priori 'at-risk' alleles for these genes (P for trend 0.004). The risk of lung cancer was increased with the combination of CYP1A1*2B or CYP1A1*4 alleles and the double deletion of both GSTM1 and GSTT1 up to an odds ratio (OR) of 8.25 (95% confidence interval 2.29-29.77) for the combination including CYP1A1*4; among never smokers, the latter combination was associated with an OR of 16.19 (1.90-137). Estimates did not change after adjustment by the number of cigarettes smoked and duration of smoking were consistent across ethnicities and were approximately the same for adenocarcinomas and squamous cell carcinomas. These observations from a large pooled analysis strongly suggest the existence of gene-gene interactions in lung carcinogenesis. People with rare combinations of common gene variants have a high risk of cancer and can be assimilated to subjects with highly penetrant mutations.

Prognostic role of K-Ras mutations in non-small cell lung cancer: still an issue for open debate.

We herein comment on a recently published experience on circulating K-ras DNA in lung cancer patients.

Metabolic genotypes as modulators of asbestos-related pleural malignant mesothelioma risk: a comparison of Finnish and Italian populations.

The role of CYP1A1, GSTM1, GSTT1, EPHX1, and NAT2 genotypes in susceptibility to malignant mesothelioma (MM) was compared in two case-control studies, previously conducted in two countries where different types of asbestos fibers have been used [Hirvonen et al., 1995. Inherited GSTM1 and NAT2 defects as concurrent risk modifiers in asbestos-related human malignant mesothelioma. Cancer Res. 55, 2981-2983; Hirvonen et al., 1996. Glutathione S-Transferase and N-Acetyltransferase genotypes and asbestos-associated pulmonary disorders. J. Natl. Cancer Inst.88, 1853-1856; Neri et al., 2005. Pleural malignant mesothelioma, genetic susceptibility and asbestos exposure. Mutat. Res. 592, 36-44]. Fifty-seven asbestos-exposed MM patients and 255 controls were recruited in Italy, 48 cases and 121 controls in Finland. In order to make the two studies comparable, they have been updated and new genotyping analyses have been performed. The NAT2 fast acetylator and EPHX1 low-activity genotypes were positively associated with MM in the Italian study, while they were negatively associated with this malignancy in the Finnish one. A combined significant effect was also observed in the Italian study for the NAT2 fast acetylator and EPHX1 low-activity genotypes, while this combination was protective in the Finnish study. Combination of NAT2 fast acetylator and GSTM1 null genotype posed a significantly increased risk of MM in the Italian, but not in the Finnish study. The opposite results obtained in Finland and Italy may be ascribed to random chance, but a role may be hypothesized for the fact that different types of asbestos have been used in the two countries.

Functional analysis of c-Met/hepatocyte growth factor pathway in malignant pleural mesothelioma.

c-Met receptor tyrosine kinase (RTK) has not been extensively studied in malignant pleural mesothelioma (MPM). In this study, c-Met was overexpressed and activated in most of the mesothelioma cell lines tested. Expression in MPM tissues by immunohistochemistry was increased (82%) in MPM in general compared with normal. c-Met was internalized with its ligand hepatocyte growth factor (HGF) in H28 MPM cells, with robust expression of c-Met. Serum circulating HGF was twice as high in mesothelioma patients as in healthy controls. There was a differential growth response and activation of AKT and extracellular signal-regulated kinase 1/2 in response to HGF for the various cell lines. Dose-dependent inhibition (IC50 < 2.5 micromol/L) of cell growth in mesothelioma cell lines, but not in H2052, H2452, and nonmalignant MeT-5A (IC50 > 10 micromol/L), was observed with the small-molecule c-Met inhibitor SU11274. Furthermore, migration of H28 cells was blocked with both SU11274 and c-Met small interfering RNA. Abrogation of HGF-induced c-Met and downstream signaling was seen in mesothelioma cells. Of the 43 MPM tissues and 7 cell lines, we have identified mutations within the semaphorin domain (N375S, M431V, and N454I), the juxtamembrane domain (T1010I and G1085X), and an alternative spliced product with deletion of the exon 10 of c-Met in some of the samples. Interestingly, we observed that the cell lines H513 and H2596 harboring the T1010I mutation exhibited the most dramatic reduction of cell growth with SU11274 when compared with wild-type H28 and nonmalignant MeT-5A cells. Ultimately, c-Met would be an important target for therapy against MPM.

Baseline micronuclei frequency in children: estimates from meta- and pooled analyses.

The number of studies evaluating the effect of environmental exposure to genotoxic agents in children has rapidly increased in the last few years. The frequency of micronuclei (MN) in peripheral blood lymphocytes determined with the cytokinesis block assay is among the most popular biomarkers used for this purpose, although large inter- and intralaboratory variability of this end point has been observed in population studies. The availability of reference measures is therefore necessary for laboratories to validate protocols and analytical procedures, and for molecular epidemiologists, as well, to estimate the statistical power of studies and to assess the quality of data. In this article, we provide estimates of the baseline frequency of MN in children, conducting a meta-analysis of MN frequency reported by field studies in children and a pooled analysis of individual data [available from published studies and from the Human Micronucleus International Collaborative Study (HUMN) database]. Thirteen articles were selected for meta-analysis, and individual data included in the pooled analysis were retrieved from the databases of 12 laboratories. Overall means of 4.48 [95% confidence interval (CI), 3.35-5.98] and 5.70 (95% CI, 4.29-7.56) MN per 1,000 binucleated cells were estimated by the meta- and pooled analysis, respectively. A clear effect of age was detected, even within the restricted range of pediatric age considered, with significantly lower frequency values in newborns. No influence of sex was found. The study showed the advantage of using data from large collaborative studies and suggested a synergistic use of meta- and pooled analysis.

Serum PDGF-AB in pleural mesothelioma.

Overexpression of platelet-derived growth factor (PDGF) has been observed in lung and pleural tumors. The aim of this study was to evaluate the diagnostic and prognostic role of serum PDGF in pleural mesothelioma (PM). Four groups of subjects were studied: 93 malignant PM patients, 33 primary non small cell lung cancer patients, 51 subjects exposed to asbestos, defined as high-risk controls, and 24 healthy controls. PDGF-AB mean concentration was higher in PM patients (45.8 ng/ml) than in high-risk controls (33.1 ng/ml) and healthy controls (26.8 ng/ml). Using the cut-off level of 49.8 ng/ml, corresponding to the mean+2SD of PDGF-AB in healthy controls, 43% of PM patients showed positive PDGF-AB levels. Survival was evaluated in 82 PM patients. At the end of the follow-up (median 9.8 months) 80.5% of patients had died. Median survival was 13.1 and 7.9 months for patients with PDGF-AB lower and higher than the cut-off, respectively. Adjusting for age, sex, histology and platelet count, positive PDGF-AB levels were associated with lower survival (OR=1.2, 95%CI: 0.9-1.6), even if not significantly so. In conclusion, serum PDGF may represent a useful additional parameter to prognostic factors already available for PM.