Department of Oncology, St. Olavs Hospital, Trondheim University Hospital, Norway; Norwegian University of Science and Technology (NTNU), Department of Cancer Research and Molecular Medicine, Trondheim, Norway.

Soluble mesothelin-related protein (SMRP) in serum is potentially a sensitive marker of malignant mesothelioma (MM) diagnosis and progression, and may be useful as screening marker. Mesothelin expression in tumors is regarded as a sensitive marker for diagnosis and disease progression, and is a candidate prognostic marker. Levels of SMRP, CA125 and CYFRA 21-1 in pre-diagnostic (1-30 years) serum samples from 47 mesothelioma cases and 141 matched controls were analysed. Mesothelin expression in tumors was assessed. The association between biomarker level and mesothelioma risk and survival was analysed, adjusting for asbestos exposure. Survival related to tumor mesothelin expression, age, sex, histological type, location, asbestos exposure and pre-clinical SMRP was analysed. There was no significant association between biomarker levels and mesothelioma risk when analysed as continuous variables or as tertiles. Biomarker levels <10, 10-19 and >/=20 years before diagnosis were not significantly associated to mesothelioma risk. Mesothelin expressed in >50% of tumor cells was seen in 36 of 47 (77%) tumors. Mesothelin expression in <50% of tumor cells was a significant negative prognostic marker in all cases of malignant mesothelioma (median survival=6 months vs. 12 months, hazard ratio (HR)=2.49, 95%CI 1.17-5.27), and also when only epithelial mesothelioma was analysed (median=6 months vs. 14 months, HR=2.36, 95%CI 1.07-5.22). When adjusted for age and gender, the prognosis was still dismal, but non-significant (HR=1.85, 95%CI 0.85-4.05). High age (>65 years) was an independent negative prognostic factor that was related to both mesothelin expression and asbestos exposure. Mesothelioma of the epithelial type of the peritoneum had a significantly longer survival than epithelial type in pleura and was also related to mesothelin expression.

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Division of Cellular and Molecular Toxicology, Biological Safety Research Center, National Institute of Health Sciences, Kamiyoga, Tokyo, Japan.

Nanomaterials of carbon origin tend to form various shapes of particles in micrometer dimensions. Among them, multi-wall carbon nanotubes (MWCNT) form fibrous or rod-shaped particles of length around 10 to 20 micrometers with an aspect ratio of more than three. Fibrous particles of this dimension including asbestos and some man-made fibers are reported to be carcinogenic, typically inducing mesothelioma. Here we report that MWCNT induces mesothelioma along with a positive control, crocidolite (blue asbestos), when administered intraperitoneally to p53 heterozygous mice that have been reported to be sensitive to asbestos. Our results point out the possibility that carbon-made fibrous or rod-shaped micrometer particles may share the carcinogenic mechanisms postulated for asbestos. To maintain sound activity of industrialization of nanomaterials, it would be prudent to implement strategies to keep good control of exposure to fibrous or rod-shaped carbon materials both in the workplace and in the future market until the biological/ carcinogenic properties, especially of their long-term biodurability, are fully assessed.

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ChemRisk, Inc., San Francisco, California 94105, USA.

Numerous investigators have suggested that there is likely to be a cumulative chrysotile exposure below which there is negligible risk of asbestos-related diseases. However, to date, little research has been conducted to identify an actual “no-effect” exposure level for chrysotile-related lung cancer and mesothelioma. The purpose of this analysis is to summarize and present all of the cumulative exposure-response data reported for predominantly chrysotile-exposed cohorts in the published literature. Criteria for consideration in this analysis included stratification of relative risk or mortality ratio estimates by cumulative chrysotile exposure. Over 350 studies were initially evaluated and subsequently excluded from the analysis due primarily to lack of cumulative exposure information, lack of information on fiber type, and/or evidence of significant exposures to amphiboles. Fourteen studies meeting the inclusion criteria were found where lung cancer risk was stratified by cumulative chrysotile exposure; four such studies were found for mesothelioma. All of the studies involved cohorts exposed to high levels of chrysotile in mining or manufacturing settings. The preponderance of the cumulative “no-effects” exposure levels for lung cancer and mesothelioma fall in a range of approximately 25-1,000 fibers per cubic centimeter per year (f/cc-yr) and 15-500 f/cc-yr, respectively, and a majority of the studies did not report an increased risk at the highest estimated exposure. Sources of uncertainty in these values include errors in the cumulative exposure estimates, conversion of dust counts to fiber data, and use of national age-adjusted mortality rates. Numerous potential biases also exist. For example, smoking was rarely controlled for and amphibole exposure did in fact occur in a majority of the studies, which would bias many of the reported “no-effect” exposure levels towards lower values. However, many of the studies likely lack sufficient power (e.g., due to small cohort size) to assess whether there could have been a significant increase in risk at the reported no-observed-adverse-effects level (NOAEL); additional statistical analyses are required to address this source of bias and the attendant influence on these values. The chrysotile NOAELs appear to be consistent with exposure-response information for certain cohorts with well-established industrial hygiene and epidemiology data. Specifically, the range of chrysotile NOAELs were found to be consistently higher than upper-bound cumulative chrysotile exposure estimates that have been published for pre-1980s automobile mechanics (e.g., 95th percentile of 2.0 f/ cc-yr), an occupation that historically worked with chrysotile-containing friction products yet has been shown to have no increased risk of asbestos-related diseases. While the debate regarding chrysotile as a risk factor for mesothelioma will likely continue for some time, future research into nonlinear, threshold cancer risk models for chrysotile-related respiratory diseases appears to be warranted.

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Biological Mechanisms and Prevention of Work-related Diseases, Health and Work Ability, Finnish Institute of Occupational Health, Helsinki, Finland.

Exposure to asbestos is known to induce lung cancer, and our previous studies have suggested that specific chromosomal regions, such as 19p13, are preferentially aberrant in lung tumours of asbestos-exposed patients. Here, we further examined the association between the 19p region and exposure to asbestos, using array comparative genomic hybridization and fluorescence in situ hybridization (FISH) in lung tumours and FISH characterization of asbestos-induced micronuclei in human bronchial epithelial BEAS 2B cells in vitro. We detected an increased number of 19p losses in the tumours of asbestos-exposed patients in comparison with tumours from non-exposed subjects with similar distribution of tumour histology in both groups (13/33; 39% vs. 3/25; 12%, P=0.04). In BEAS 2B cells, a 48-h exposure to crocidolite asbestos (2.0 mug/cm(2)) was found to induce centromere-negative micronuclei harbouring chromosomal fragments. Furthermore, an increased frequency of rare micronuclei containing a 19p fragment was observed after the crocidolite treatment in comparison with untreated controls (6/6000 vs. 1/10000, P=0.01). The results suggest that 19p has significance in asbestos-associated carcinogenesis and that asbestos may be capable of inducing specific chromosome aberrations.

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Università Politecnica delle Marche, Dipartimento di Patologia Molecolare e Terapie Innovative, Clinica di Medicina del Lavoro, Tronto 10/a, 0020 Torrette, AN. m.amati@univpm.it

Improved detection methods for diagnosis of asymptomatic malignant pleural mesothelioma (MPM) are essential for an early and reliable detection and treatment of this disease. Thus, focus has been on finding tumour markers in the blood. 94 asbestos-exposed subjects, 22 patients with MM, and 54 healthy subjects were recruited for evaluation of the significance of 8-hydroxy-2′-deoxy-guanosine (80HdG) in white blood cells and plasma concentrations of soluble mesothelin-related peptides (SMRPs), angiogenic factors (PDGFbeta, HGF, bFGF, VEGFbeta), and matrix proteases (MMP2, MMP9, TIMP1, TIMP2) for potential early detection of MM. The area under ROC curves (AUC) indicates that 80HdG levels can discriminate asbestos-exposed subjects from controls but not from MPM patients. Significant AUC values were found for SMRP discriminating asbestos-exposed subjects from MPM patients but not from controls. VEGFbeta can significantly differentiate asbestos-exposed subjects from control and cancer groups. No diagnostic value was observed for MMP2, MMP9, TIMP1, TIMP2. The sensitivity and specificity results of markers were calculated at defined cut-offs. The combination of 80HdG, VEGFbeta and SMRPs best distinguished the individual groups, suggesting a potential indicator of early and advanced MPM cancers. The combination of blood biomarkers and radiographic findings could be used to stratify the risk of mesothelioma in asbestos-exposed populations.

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