Mechanisms of carcinogenesis and clinical features of asbestos-associated cancers

Presence of asbestos in building materials and soils in postfire areas of Mati, Kineta and Varimbombi in Greece

The present study was carried out to determine the presence of asbestos in Wildland Urban Interface (WUI) areas of Attica, Greece affected by wildfires between 2018 and 2021. It concerns the first major campaign that took place in Greece. The samples tested in this work were collected from prespecified buildings of the burned area. The samples included different types of building materials such as bricks, wall coatings, insulation plates etc. Soil samples nearby the buildings were also collected to examine dispersion of the fibers. The identification of asbestos was based on the optical properties of the fibrous particles and was performed with stereo microscope and Polarized Light Microscopy according to P401 provided by BOHS (Health and Safety Executive (HSE) 2021). Scanning Electron Microscopy with energy dispersive spectroscopy was also used to validate the presence of asbestos and determine its chemical composition. In this work, 2 different types of asbestos were determined, chrysotile and crocidolite. In some cases, fragments of asbestos containing materials were also detected in the afore-mentioned soil samples indicating dispersion of asbestos containing debris in an area around the burned spots. The presence of asbestos that was identified in this preliminary study could raise concerns to humans in the urban areas. For that reason, a risk assessment for the identified asbestos containing materials (ACMs) was conducted according to the guidelines on management and abatement of ACMs of Health and Safety Authority and the Asbestos: Survey guide, Appendix 4: Material assessment algorithm of Health and Safety Executive (HSE).

Pathophysiological Impact of the MEK5/ERK5 Pathway in Oxidative Stress

Oxidative stress regulates many physiological and pathological processes. Indeed, a low increase in the basal level of reactive oxygen species (ROS) is essential for various cellular functions, including signal transduction, gene expression, cell survival or death, as well as antioxidant capacity. However, if the amount of generated ROS overcomes the antioxidant capacity, excessive ROS results in cellular dysfunctions as a consequence of damage to cellular components, including DNA, lipids and proteins, and may eventually lead to cell death or carcinogenesis. Both in vitro and in vivo investigations have shown that activation of the mitogen-activated protein kinase kinase 5/extracellular signal-regulated kinase 5 (MEK5/ERK5) pathway is frequently involved in oxidative stress-elicited effects. In particular, accumulating evidence identified a prominent role of this pathway in the anti-oxidative response. In this respect, activation of krüppel-like factor 2/4 and nuclear factor erythroid 2-related factor 2 emerged among the most frequent events in ERK5-mediated response to oxidative stress. This review summarizes what is known about the role of the MEK5/ERK5 pathway in the response to oxidative stress in pathophysiological contexts within the cardiovascular, respiratory, lymphohematopoietic, urinary and central nervous systems. The possible beneficial or detrimental effects exerted by the MEK5/ERK5 pathway in the above systems are also discussed.

Journey to the centre of the lung. The perspective of a mineralogist on the carcinogenic effects of mineral fibres in the lungs

This work reviews the bio-chemical mechanisms leading to adverse effects produced when mineral fibres are inhaled and transported in the lungs from the perspective of a mineralogist. The behaviour of three known carcinogenic mineral fibres (crocidolite, chrysotile, and fibrous-asbestiform erionite) during their journey through the upper respiratory tract, the deep respiratory tract and the pleural cavity is discussed. These three fibres have been selected as they are the most socially and economically relevant mineral fibres representative of the classes of chain silicates (amphiboles), layer silicates (serpentine), and framework silicates (zeolites), respectively. Comparison of the behaviour of these fibres is made according to their specific crystal-chemical assemblages and properties. Known biological and subsequent pathologic effects which lead and contribute to carcinogenesis are critically reviewed under the mineralogical perspective and in relation to recent progress in this multidisciplinary field of research. Special attention is given to the understanding of the cause-effect relationships for lung cancer and malignant mesothelioma. Comparison with interstitial pulmonary fibrosis, or "asbestosis", will also be made here. This overview highlights open issues, data gaps, and conflicts in the literature for these topics, especially as regards relative potencies of the three mineral fibres under consideration for lung cancer and mesothelioma. Finally, an attempt is made to identify future research lines suitable for a general comprehensive model of the carcinogenicity of mineral fibres.

An Innovative Filtering System for the Handling of Asbestos-Based Products: Improvement of Safety and Quality of Work in Analysis Laboratories

Although being banned or restricted in many countries since the early 1990s, large quantities of asbestos are still used or present in building materials all over the world and its removal or handling requires specific systems that limit exposure to airborne fibers The exposure to asbestos causes chronic diseases such as asbestosis and lung cancer with an incubation period of 20 to 50 years. Among the operators most exposed to contamination are those who handle and analyze the materials in laboratories. For this reason, our work focused on an innovative method for removing a filter unit from a laboratory extraction hood, in order to improve the safety conditions for the operators and the surrounding environment. The hood has a particular construction technology with a mechanism that allows the spraying of a special encapsulating liquid on the ULPA filters below the work-bench, which is capable of forming a film and blocking the fibers on the surface of the same filter. The fibers are irreversibly bounded and can no longer be released into the surrounding environment. The monitoring of activity highlighted the absence of asbestos fibers in the air after installation of the filter and workers feel safer performing their activities. The introduction of an innovative filtering system enhanced the safety of work activities involving asbestos exposure, moreover, the time spent on the hood’s maintenance and the risk perception of workers were improved.

Effect of IL-15 addition on asbestos-induced suppression of human cytotoxic T lymphocyte induction

Background

Asbestos fibers possess tumorigenicity and are thought to cause mesothelioma. We have previously reported that exposure to asbestos fibers causes a reduction in antitumor immunity. Asbestos exposure in the mixed lymphocyte reaction (MLR) showed suppressed induction of cytotoxic T lymphocytes (CTLs), accompanied by a decrease in proliferation of CD8⁺ T cells. Recently, we reported that asbestos-induced suppression of CTL induction is not due to insufficient levels of interleukin-2 (IL-2). In this study, we continue to investigate the mechanism responsible for the effect of asbestos fibers on the differentiation of CTLs and focus on interleukin-15 (IL-15) which is known to be a regulator of T lymphocyte proliferation.

Methods

For MLR, human peripheral blood mononuclear cells (PBMCs) were cultured with irradiated allogenic PBMCs upon exposure to chrysotile B asbestos at 5 μg/ml for 7 days. After 2 days of culture, IL-15 was added at 1 ng/ml. After 7 days of MLR, PBMCs were collected and analyzed for phenotypic and functional markers of CD8⁺ T cells with fluorescence-labeled anti-CD3, anti-CD8, anti-CD45RA, anti-CD45RO, anti-CD25, and anti-granzyme B antibodies using flow cytometry. To examine the effect of IL-15 on the expression level of intracellular granzyme B in proliferating and non-proliferating CD8⁺ lymphocytes, PBMCs were stained using carboxyfluorescein diacetate succinimidyl ester (CFSE) and then washed and used for the MLR.

Results

IL-15 addition partially reversed the decrease in CD3⁺CD8⁺ cell numbers and facilitated complete recovery of granzyme B⁺ cell percentages. IL-15 completely reversed the asbestos-induced decrease in percentage of granzyme B⁺ cells in both non-proliferating CFSE-positive and proliferating CFSE-negative CD8⁺ cells. The asbestos-induced decrease in the percentage of CD25⁺ and CD45RO⁺ cells in CD8⁺ lymphocytes was not reversed by IL-15.

Conclusion

These findings indicate that CTLs induced upon exposure to asbestos possess dysfunctional machinery that can be partly compensated by IL-15 supplementation, and that IL-15 is more effective in the recovery of proliferation and granzyme B levels from asbestos-induced suppression of CTL induction compared with IL-2.

Effect of asbestos exposure on differentiation and function of cytotoxic T lymphocytes

Asbestos exposure is known to cause malignant mesothelioma, which is associated with poor prognosis. We focused on and examined the effect of asbestos exposure on the differentiation and function of cytotoxic T lymphocytes (CTLs). CTLs have the ability to specifically attack tumor cells after being differentiated from naïve CD8⁺ T cells following antigen stimulation. Exposure to chrysotile B asbestos suppressed the differentiation of CTLs during the mixed lymphocyte reaction (MLR) and was associated with a decrease in proliferation of CD8⁺ T cells. Additionally, in an effort to investigate the mechanism associated with suppressed CTL differentiation upon exposure to asbestos, we focused on IL-2, a cytokine involved in T cell proliferation. Our findings indicated that insufficient levels of IL-2 are not the main cause for the suppressed induction of CTLs by asbestos exposure, although they suggest potential improvement in the suppressed CTL function. Furthermore, the functional properties of peripheral blood CD8⁺ lymphocytes from asbestos-exposed individuals with pleural plaque (PP) and patients with malignant mesothelioma (MM) were examined. MM patients showed lower perforin levels in CD8⁺ lymphocytes following stimulation compared with PP-positive individuals. The production capacity of IFN-γ in the MM group tended to be lower compared with healthy volunteers or PP-positive individuals. In an effort to determine whether chronic and direct asbestos exposure affected the function of CD8⁺ T cells, cultured human CD8⁺ T cells were employed as an in vitro model and subjected to long-term exposure to chrysotile (CH) asbestos. This resulted in decreased levels of intracellular perforin and secreted IFN-γ. Those findings underlie the possibility that impaired CD8⁺ lymphocyte function is caused by asbestos exposure, which fail to suppress the development of MM. Our studies therefore reveal novel effects of asbestos exposure on CTLs, which might contribute towards the development and implementation of an effective strategy for the prevention and cure of malignant mesothelioma.

Decrease in Intracellular Perforin Levels and IFN-γ Production in Human CD8+ T Cell Line following Long-Term Exposure to Asbestos Fibers

Although the tumorigenicity of asbestos, which is thought to cause mesothelioma, has been clarified, its effect on antitumor immunity requires further investigation. We previously reported a decrease in the percentage of perforin⁺ cells of stimulated CD8⁺ lymphocytes derived from patients with malignant mesothelioma. Therefore, we examined the effects of long-term exposure to asbestos on CD8⁺ T cell functions by comparing long-term cultures of the human CD8⁺ T cell line EBT-8 with and without exposure to chrysotile (CH) asbestos as an in vitro model. Exposure to CH asbestos at 5 μg/ml or 30 μg/ml did not result in a decrease in intracellular granzyme B in EBT-8 cells. In contrast, the percentage of perforin⁺ cells decreased at both doses of CH exposure. CH exposure at 30 μg/ml did not suppress degranulation following stimulation with antibodies to CD3. Secreted production of IFN-γ stimulated via CD3 decreased by CH exposure at 30 μg/ml, although the percentage of IFN-γ⁺ cells induced by PMA/ionomycin did not decrease. These results indicate that long-term exposure to asbestos can potentially suppress perforin levels and the production of IFN-γ in human CD8⁺ T cells.

Chrysotile effects on the expression of anti-oncogene P53 and P16 and oncogene C-jun and C-fos in Wistar rats' lung tissues

Chrysotile is the most widely used form of asbestos worldwide. China is the world's largest consumer and second largest producer of chrysotile. The carcinogenicity of chrysotile has been extensively documented, and accumulative evidence has shown that chrysotile is capable of causing lung cancer and other forms of cancer. However, molecular mechanisms underlying the tumorigenic effects of chrysotile remained poorly understood. To explore the carcinogenicity of chrysotile, Wistar rats were administered by intratracheal instillation (by an artificial route of administration) for 0, 0.5, 2, or 8 mg/ml of natural chrysotile (from Mangnai, Qinghai, China) dissolved in saline, repeated once a month for 6 months (a repeated high-dose exposure which may have little bearing on the effects following human exposure). The lung tissues were analyzed for viscera coefficients and histopathological alterations. Expression of P53, P16, C-JUN, and C-FOS was measured by western blotting and qRT-PCR. Our results found that chrysotile exposure leads the body weight to grow slowly and lung viscera coefficients to increase in a dose-dependent manner. General sample showed white nodules, punctiform asbestos spots, and irregular atrophy; moreover, HE staining revealed inflammatory infiltration, damage of alveolar structures, agglomerations, and pulmonary fibrosis. In addition, chrysotile can induce inactivation of the anti-oncogene P53 and P16 and activation of the proto-oncogenes C-JUN and C-FOS both in the messenger RNA and protein level. In conclusion, chrysotile induced an imbalanced expression of cancer-related genes in rats' lung tissue. These results contribute to our understanding of the carcinogenic mechanism of chrysotile.

Optimal management program for asbestos containing building materials to be available in the event of a disaster

The safe management and disposal of asbestos is a matter of considerable importance. A large number of studies have been undertaken to quantify the issue of waste management following a disaster. Nevertheless, there have been few (if any) studies concerning asbestos waste, covering the amount generated, the cost of disposal, and the degree of hazard incurred. Thus, the current study focuses on developing a program for the management of Asbestos Containing Building Materials (ACBMs), which form the source of asbestos waste in the event of a disaster. The study will also discuss a case study undertaken in a specific region in Korea in terms of: (1) the location of ACBM-containing buildings; (2) types and quantities of ACBMs; (3) the cost of ACBM disposal; (4) the amount of asbestos fiber present during normal times and during post-disaster periods; (5) the required order in which ACBM-containing buildings should be dismantled; and (6) additional greenhouse gases generated during ACBM removal. The case study will focus on a specific building, with an area of 35.34m², and will analyze information concerning the abovementioned points. In addition, the case study will focus on a selected area (108 buildings) and the administrative district (21,063 buildings). The significance of the program can be established by the fact that it visibly transmits information concerning ACBM management. It is a highly promising program, with a widespread application for the safe management and optimal disposal of asbestos in terms of technology, policy, and methodology.

The Suppressed Induction of Human Mature Cytotoxic T Lymphocytes Caused by Asbestos Is Not due to Interleukin-2 Insufficiency

We previously reported that exposure to chrysotile B (CB) asbestos suppressed the induction of mature cytotoxic T lymphocytes (CTLs) during mixed lymphocyte reaction assays (MLRs) with a decrease in the proliferation of immature CTLs. However, the mechanism responsible for the effect of asbestos fibers on the differentiation of CTLs remains unclear. Since interleukin-2 (IL-2) is a regulator of T lymphocyte proliferation, we examined the effect of IL-2 addition on suppressed CTL differentiation in CB-exposed cultures using flow cytometry (FCM). When IL-2 was added at 1 ng/mL on the second day of MLRs, the asbestos-caused decreases in the proliferation and percentages of CD25⁺ and CD45RO⁺ cells in CD8⁺ lymphocytes were not recovered by IL-2 addition, although the decrease in percentage of granzyme B⁺ cells was partially recovered. CD8⁺ lymphocytes from the IL-2-treated culture with asbestos showed the same degree of cytotoxicity as those in cultures without IL-2 or asbestos. These findings indicate that IL-2 insufficiency is not the main cause for the suppressed induction of CTLs by asbestos exposure, although they suggest a potential for the improvement of such suppressed CTL functions. Secretory factors other than IL-2 in addition to membrane-bound stimulatory molecules may play a role in asbestos-caused suppressed CTL differentiation.

Estimating the Additional Greenhouse Gas Emissions in Korea: Focused on Demolition of Asbestos Containing Materials in Building

When asbestos containing materials (ACM) must be removed from the building before demolition, additional greenhouse gas (GHG) emissions are generated. However, precedent studies have not considered the removal of ACM from the building. The present study aimed to develop a model for estimating GHG emissions created by the ACM removal processes, specifically the removal of asbestos cement slates (ACS). The second objective was to use the new model to predict the total GHG emission produced by ACM removal in the entire country of Korea. First, an input-equipment inventory was established for each step of the ACS removal process. Second, an energy consumption database for each equipment type was established. Third, the total GHG emission contributed by each step of the process was calculated. The GHG emissions generated from the 1,142,688 ACS-containing buildings in Korea was estimated to total 23,778 tonCO₂eq to 132,141 tonCO₂eq. This study was meaningful in that the emissions generated by ACS removal have not been studied before. Furthermore, the study deals with additional problems that can be triggered by the presence of asbestos in building materials. The method provided in this study is expected to contribute greatly to the calculation of GHG emissions caused by ACM worldwide.

Fungal weathering of asbestos in semi arid regions of India

The science of Geomicrobiology, which deals with mineral- microbe interaction in nature contributes effectively to three important processes namely- mineral and metal bioremediation, biomining and soil mineral formation by microbes. Bioremediation one of the important process of the above, degrades or transforms hazardous contaminants to less toxic compounds. Several groups of fungi have proved highly efficient in this aspect, with asbestos being one such toxic entity in the environment on which their activity was studied. The present investigation uses the same tool as a device for detoxifying asbestos, a potent carcinogenic entity; with fungal isolates native to the asbestos mines of Rajasthan, India, being investigated for the first time. The cellular mechanism of asbestos toxicity is mainly attributed to the presence of iron in its chemical composition which catalyzes generation of free radicals leading to oxidation of biomolecules. The two dominant novel species found therein, identified as Aspergillus tubingenesis and Coemansia reversa have proved capable of actively removing iron from asbestos fibers as studied by scanning electron microscopy- electron diffraction X-ray (SEM-EDX) analysis. This probably could lead to a reduction in toxicity of asbestos, due to reduced iron concentration as reported in related studies. Many fungi are known to release iron chelating compounds, siderophores, which could be instrumental in the study. The findings related to two new fungal species being added to the list of earlier identified fungal bioremediators of asbestos, widens the prospect of using bioremediation as an effective tool for asbestos detoxification.

The chemical environment of iron in mineral fibres. A combined X-ray absorption and Mössbauer spectroscopic study

Although asbestos represents today one of the most harmful contaminant on Earth, in 72% of the countries worldwide only amphiboles are banned while controlled use of chrysotile is allowed. Uncertainty on the potential toxicity of chrysotile is due to the fact that the mechanisms by which mineral fibres induces cyto- and geno-toxic damage are still unclear. We have recently started a long term project aimed at the systematic investigation of the crystal-chemistry, bio-interaction and toxicity of the mineral fibres. This work presents a systematic structural investigation of iron in asbestos and erionite (considered the most relevant mineral fibres of social and/or economic-industrial importance) using synchrotron X-ray absorption and Mössbauer spectroscopy. In all investigated mineral fibres, iron in the bulk structure is found in octahedral sites and can be made available at the surface via fibre dissolution. We postulate that the amount of hydroxyl radicals released by the fibers depends, among other factors, upon their dissolution rate; in relation to this, a ranking of ability of asbestos fibres to generate hydroxyl radicals, resulting from available surface iron, is advanced: amosite > crocidolite ≈ chrysotile > anthophyllite > tremolite. Erionite, with a fairly high toxicity potential, contains only octahedrally coordinated Fe(3+). Although it needs further experimental evidence, such available surface iron may be present as oxide nanoparticles coating and can be a direct cause of generation of hydroxyl radicals when such coating dissolves.

Genome-wide Gene-Asbestos Exposure Interaction Association Study Identifies a Common Susceptibility Variant on 22q13.31 Associated with Lung Cancer Risk

BACKGROUND

Occupational asbestos exposure has been found to increase lung cancer risk in epidemiologic studies.

METHODS

We conducted an asbestos exposure-gene interaction analyses among several Caucasian populations who were current or ex-smokers. The discovery phase included 833 Caucasian cases and 739 Caucasian controls, and used a genome-wide association study (GWAS) to identify single-nucleotide polymorphisms (SNP) with gene-asbestos interaction effects. The top ranked SNPs from the discovery phase were replicated within the International Lung and Cancer Consortium (ILCCO). First, in silico replication was conducted in those groups that had GWAS and asbestos exposure data, including 1,548 cases and 1,527 controls. This step was followed by de novo genotyping to replicate the results from the in silico replication, and included 1,539 cases and 1,761 controls. Multiple logistic regression was used to assess the SNP-asbestos exposure interaction effects on lung cancer risk.

RESULTS

We observed significantly increased lung cancer risk among MIRLET7BHG (MIRLET7B host gene located at 22q13.31) polymorphisms rs13053856, rs11090910, rs11703832, and rs12170325 heterozygous and homozygous variant allele(s) carriers (P < 5 × 10(-7) by likelihood ratio test; df = 1). Among the heterozygous and homozygous variant allele(s) carriers of polymorphisms rs13053856, rs11090910, rs11703832, and rs12170325, each unit increase in the natural log-transformed asbestos exposure score was associated with age-, sex-, smoking status, and center-adjusted ORs of 1.34 [95% confidence interval (CI), 1.18-1.51], 1.24 (95% CI, 1.14-1.35), 1.28 (95% CI, 1.17-1.40), and 1.26 (95% CI, 1.15-1.38), respectively, for lung cancer risk.

CONCLUSION

Our findings suggest that MIRLET7BHG polymorphisms may be important predictive markers for asbestos exposure-related lung cancer.

IMPACT

To our knowledge, our study is the first report using a systematic genome-wide analysis in combination with detailed asbestos exposure data and replication to evaluate asbestos-associated lung cancer risk.

Functional Alteration of Natural Killer Cells and Cytotoxic T Lymphocytes upon Asbestos Exposure and in Malignant Mesothelioma Patients

Malignant mesothelioma is caused by exposure to asbestos, which is known to have carcinogenic effects. However, the development of mesothelioma takes a long period and results from a low or intermediate dose of exposure. These findings have motivated us to investigate the immunological effects of asbestos exposure and analyze immune functions of patients with mesothelioma and pleural plaque, a sign of exposure to asbestos. Here, we review our knowledge concerning natural killer (NK) cells and cytotoxic T lymphocytes (CTL). NK cells showed impaired cytotoxicity with altered expression of activating receptors upon exposure to asbestos, while induction of granzyme(+) cells in CD8(+) lymphocytes was suppressed by asbestos exposure. It is interesting that a decrease in NKp46, a representative activating receptor, is common between NK cells in PBMC culture with asbestos and those of mesothelioma patients. Moreover, it was observed that CD8(+) lymphocytes may be stimulated by some kind of "nonself" cells in plaque-positive individuals and in mesothelioma patients, whereas CTL in mesothelioma is impaired by poststimulation maintenance of cytotoxicity. These findings suggest that analysis of immunological parameters might contribute to the evaluation of health conditions of asbestos-exposed individuals and to a greater understanding of the pathology of malignant mesothelioma.

The c-Jun N-terminal kinase signaling pathway mediates chrysotile asbestos-induced alveolar epithelial cell apoptosis

Exposure to chrysotile asbestos exposure is associated with an increased risk of mortality in combination with pulmonary diseases including lung cancer, mesothelioma and asbestosis. Multiple mechanisms by which chrysotile asbestos fibers induce pulmonary disease have been identified, however the role of apoptosis in human lung alveolar epithelial cells (AEC) has not yet been fully explored. Accumulating evidence implicates AEC apoptosis as a crucial event in the development of both idiopathic pulmonary fibrosis and asbestosis. The aim of the present study was to determine whether chrysotile asbestos induces mitochondria‑regulated (intrinsic) AEC apoptosis and, if so, whether this induction occurs via the activation of mitogen‑activated protein kinases (MAPK). Human A549 bronchoalveolar carcinoma‑derived cells with alveolar epithelial type II‑like features were used. The present study showed that chrysotile asbestos induced a dose‑ and time‑dependent decrease in A549 cell viability, which was accompanied by the activation of the MAPK c‑Jun N‑terminal kinases (JNK), but not the MAPKs extracellular signal‑regulated kinase 1/2 and p38. Chrysotile asbestos was also shown to induce intrinsic AEC apoptosis, as evidenced by the upregulation of the pro‑apoptotic genes Bax and Bak, alongside the activation of caspase‑9, poly (ADP‑ribose) polymerase (PARP), and the release of cytochrome c. Furthermore, the specific JNK inhibitor SP600125 blocked chrysotile asbestos‑induced JNK activation and subsequent apoptosis, as assessed by both caspase‑9 cleavage and PARP activation. The results of the present study demonstrated that chrysotile asbestos induces intrinsic AEC apoptosis by a JNK‑dependent mechanism, and suggests a potential novel target for the modulation of chrysotile asbestos‑associated lung diseases.

In vivo genotoxicity evaluation of lung cells from Fischer 344 rats following 28 days of inhalation exposure to MWCNTs, plus 28 days and 90 days post-exposure

Despite their useful physico-chemical properties, carbon nanotubes (CNTs) continue to cause concern over occupational and human health due to their structural similarity to asbestos. Thus, to evaluate the toxic and genotoxic effect of multi-wall carbon nanotubes (MWCNTs) on lung cells in vivo, eight-week-old rats were divided into four groups (each group = 25 animals), a fresh air control (0 mg/m(3)), low (0.17 mg/m(3)), middle (0.49 mg/m(3)), and high (0.96 mg/m(3)) dose group, and exposed to MWCNTs via nose-only inhalation 6 h per day, 5 days per week for 28 days. The count median length and geometric standard deviation for the MWCNTs determined by TEM were 330.18 and 1.72 nm, respectively, and the MWCNT diameters ranged from 10 to 15 nm. Lung cells were isolated from five male and five female rats in each group on day 0, day 28 (only from males) and day 90 following the 28-day exposure. The total number of animals used was 15 male and 10 female rats for each concentration group. To determine the genotoxicity of the MWCNTs, a single cell gel electrophoresis assay (Comet assay) was conducted on the rat lung cells. As a result of the exposure, the olive tail moments were found to be significantly higher (p < 0.05) in the male and female rats from all the exposed groups when compared with the fresh air control. In addition, the high-dose exposed male and middle and high-dose exposed female rats retained DNA damage, even 90 days post-exposure (p < 0.05). To investigate the mode of genotoxicity, the intracellular reactive oxygen species (ROS) levels and inflammatory cytokine levels (TNF-α, TGF- β, IL-1, IL-2, IL-4, IL-5, IL-10, IL-12 and IFN-γ) were also measured. For the male rats, the H2O2 levels were significantly higher in the middle (0 days post-exposure) and high- (0 days and 28 days post-exposure) dose groups (p < 0.05). Conversely, the female rats showed no changes in the H2O2 levels. The inflammatory cytokine levels in the bronchoalveolar lavage (BAL) fluid did not show any statistically significant difference. Interestingly, the short-length MWCNTs deposited in the lung cells were persistent at 90 days post-exposure. Thus, exposing lung cells to MWCNTs with a short tube length may induce genotoxicity.

The zeta potential of mineral fibres

For the first time, the zeta (ξ) potential of pathogenic mineral fibres (chrysotiles, amphiboles and erionite) was systematically investigated to shed light on the relationship between surface reactivity and fibre pathogenicity. A general model explaining the zeta potential of chrysotile, amphiboles and erionite has been postulated. In double distilled water, chrysotiles showed positive values while crocidolite and erionite showed negative values. In contact with organic solutions, all fibres exhibited negative values of zeta potential. The decrease of the surface potential is deemed to be a defensive chemical response of the macrophage cells to minimize hemolytic damage. Negatively charged surfaces favour the binding of collagen and redox activated Fe-rich proteins, to form the so-called asbestos bodies and prompt the formation of HO via the reaction with peroxide (H2O2+e(-)→HO+HO(-)). An additional mechanism accounting for higher carcinogenicity is possibly related to the Ca(2+) sequestration by the fibres with surface negative potential, impairing the mitochondrial apoptotic pathway. It was also found that with a negative zeta potential, the attractive forces prevailed over repulsions and favoured processes such as agglomeration responsible of a tumorigenic chronic inflammation.

AKT/mTOR and c-Jun N-terminal kinase signaling pathways are required for chrysotile asbestos-induced autophagy

Chrysotile asbestos is closely associated with excess mortality from pulmonary diseases such as lung cancer, mesothelioma, and asbestosis. Although multiple mechanisms in which chrysotile asbestos fibers induce pulmonary disease have been identified, the role of autophagy in human lung epithelial cells has not been examined. In this study, we evaluated whether chrysotile asbestos induces autophagy in A549 human lung epithelial cells and then analyzed the possible underlying molecular mechanism. Chrysotile asbestos induced autophagy in A549 cells based on a series of biochemical and microscopic autophagy markers. We observed that asbestos increased expression of A549 cell microtubule-associated protein 1 light chain 3 (LC3-II), an autophagy marker, in conjunction with dephosphorylation of phospho-AKT, phospho-mTOR, and phospho-p70S6K. Notably, AKT1/AKT2 double-knockout murine embryonic fibroblasts (MEFs) had negligible asbestos-induced LC3-II expression, supporting a crucial role for AKT signaling. Chrysotile asbestos also led to the phosphorylation/activation of Jun N-terminal kinase (JNK) and p38 MAPK. Pharmacologic inhibition of JNK, but not p38 MAPK, dramatically inhibited the protein expression of LC3-II. Moreover, JNK2(-/-) MEFs but not JNK1(-/-) MEFs blocked LC3-II levels induced by chrysotile asbestos. In addition, N-acetylcysteine, an antioxidant, attenuated chrysotile asbestos-induced dephosphorylation of P-AKT and completely abolished phosphorylation/activation of JNK. Finally, we demonstrated that chrysotile asbestos-induced apoptosis was not affected by the presence of the autophagy inhibitor 3-methyladenine or autophagy-related gene 5 siRNA, indicating that the chrysotile asbestos-induced autophagy may be adaptive rather than prosurvival. Our findings demonstrate that AKT/mTOR and JNK2 signaling pathways are required for chrysotile asbestos-induced autophagy. These data provide a mechanistic basis for possible future clinical applications targeting these signaling pathways in the management of asbestos-induced lung disease.

Functional properties of CD8(+) lymphocytes in patients with pleural plaque and malignant mesothelioma

It is known that asbestos exposure can cause malignant mesothelioma (MM) and that CD8⁺ T cells play a critical role in antitumor immunity. We examined the properties of peripheral blood CD8⁺ lymphocytes from asbestos-exposed patients with pleural plaque (PL) and MM. The percentage of CD3⁺CD8⁺ cells in PBMCs did not differ among the three groups, although the total numbers of PBMCs of the PL and MM groups were lower than those of the healthy volunteers (HV). The percentage of IFN-γ⁺ and CD107a⁺ cells in PMA/ionomycin-stimulated CD8⁺ lymphocytes did not differ among the three groups. Percentages of perforin⁺ cells and CD45RA⁻ cells in fresh CD8⁺ lymphocytes of PL and MM groups were higher than those of HV. Percentages of granzyme B⁺ and perforin⁺ cells in PMA/ionomycin-stimulated CD8⁺ lymphocytes were higher in PL group compared with HV. The MM group showed a decrease of perforin level in CD8⁺ lymphocytes after stimulation compared with patients with PL. These results indicate that MM patients have characteristics of impairment in stimulation-induced cytotoxicity of peripheral blood CD8⁺ lymphocytes and that PL and MM patients have a common character of functional alteration in those lymphocytes, namely, an increase in memory cells, possibly related to exposure to asbestos.

The role of genotoxicity in asbestos-induced mesothelioma: an explanation for the differences in carcinogenic potential among fiber types

The mechanism(s) underlying asbestos toxicity associated with the pathogenesis of mesothelioma has been a challenge to unravel for more than 60 years. A significant amount of research has focused on the characteristics of different fiber types and their potential to induce mesothelioma. These mechanistic studies of fiber toxicity have proceeded along two lines: those demonstrating biochemical mechanisms by which fibers induce disease and those investigating human susceptibility. Most recent studies focused on in vitro genotoxic effects induced by asbestos as the mechanism responsible for asbestos-induced disease. Although asbestos exerts a genotoxic effect at certain concentrations in vitro, a positive response in these tests does not indicate that the chemical is likely to produce an increased risk of carcinogenesis in exposed human populations. Thus far, findings from studies on the effects of fiber type in mesothelial cells are seriously flawed by a lack of a dose response relationship. The common limitation of these in vitro experiments is the lack of attention paid to the complexities of the human anatomy, biochemistry and physiology, which make the observed effects in these experimental systems difficult to extrapolate to persons in the workplace. Mechanistic differences between carcinogenic and genotoxic processes indicate why tests for genotoxicity do not provide much insight regarding the ability to predict carcinogenic potential in workers exposed to asbestos doses in the post-Occupational Safety and Health Administration era. This review discusses the existing literature on asbestos-induced genotoxicity and explains why these studies may or may not likely help characterize the dose-response curve at low dose.

Potential toxicity and safety evaluation of nanomaterials for the respiratory system and lung cancer

Engineered nanomaterials (ENMs) are a diverse group of materials finding increasing use in manufacturing, computing, food, pharmaceuticals, and biomedicine due to their very small size and exceptional properties. Health and safety concerns for ENMs have forced regulatory agencies to consider preventive measures and regulations for workers’ health and safety protection. Respiratory system toxicity from inhalable ENMs is the most important concern to health specialists. In this review, we focus on similarities and differences between conventional microparticles (diameters in mm and μm), which have been previously studied, and nanoparticles (sizes between 1 and 100 nm) in terms of size, composition, and mechanisms of action in biological systems. In past decades, respirable particulate matter (PM), asbestos fibers, crystalline silicate, and various amorphous dusts have been studied, and epidemiological evidence has shown how dangerous they are to human health, especially from exposure in working environments. Scientific evidence has shown that there is a close connection between respirable PM and pulmonary oxidative stress through the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). There is a close connection between oxidative stress in the cell and the elicitation of an inflammatory response via pro-inflammatory gene transcription. Inflammatory processes increase the risk for lung cancer. Studies in vitro and in vivo in the last decade have shown that engineered nanoparticles (ENPs) at various doses can cause ROS generation, oxidative stress, and pro-inflammatory gene expression in the cell. It is assumed that ENPs have the potential to cause acute respiratory diseases and probably lung cancer in humans. The situation regarding chronic exposure at low doses is more complicated. The long-term accumulation of ENPs in the respiratory system cannot be excluded. However, at present, exposure data for the general public regarding ENPs are not available.

Effect of asbestos exposure on differentiation of cytotoxic T lymphocytes in mixed lymphocyte reaction of human peripheral blood mononuclear cells

Asbestos fibers are associated with tumorigenicity, and are thought to cause mesothelioma. However, their effect on immune response remains unclear. We examined the effect of asbestos exposure on differentiation of cytotoxic T lymphocytes (CTLs) in mixed lymphocyte reactions (MLR) of human peripheral blood mononuclear cells (PBMCs) upon exposure to chrysotile B (CB) or crocidolite (CR) asbestos at 5 μg/ml for 7 days. Exposure to CB during MLR suppressed increases in the percentage and number of CD8⁺ T cells in response to allogenic cells. The cytotoxicity for allogenic targets decreased in PBMCs exposed to CB, but not CR, when compared with PBMCs without any exposure during MLR. Exposure to CB during MLR resulted in suppression of increases in granzyme B⁺ cells and IFN-γ⁺ cells. CB exposure also resulted in suppression of increases in CD45RO⁺ effector/memory cells and CD25⁺-activated cells in CD8⁺ lymphocytes, and a decrease in CD45RA⁺ cells. CB exposure suppressed the proliferation of CD8⁺ lymphocytes without an increase in annexin V⁺ apoptotic cells in CD8⁺ lymphocytes. Moreover, the production of IL-10, IFN-γ, and TNF-α, but not IL-2, decreased in the presence of CB. These results suggest that exposure to asbestos potentially suppresses the differentiation of cytotoxic T lymphocyte, accompanied by decreases in IFN-γ and TNF-α.

Cyclooxygenase-2, epidermal growth factor receptor, and aromatase signaling in inflammation and mesothelioma

Malignant mesothelioma or mesothelioma is a rare form of cancer that develops from transformed cells originating in the mesothelium, the protective lining that covers many of the internal organs of the body. It is directly linked to asbestos exposure, which acts as a carcinogen by initiating the carcinogenic process. Because of their shape, asbestos fibers can cross the membrane barriers inside the body and cause inflammatory and fibrotic reactions. Such reactions are believed to be the mechanism by which asbestos fibers may trigger malignant mesothelioma in the pleural membrane around the lungs. Carcinogens are known to modulate the transcription factors, antiapoptotic proteins, proapoptotic proteins, protein kinases, cell-cycle proteins, cell adhesion molecules, COX-2, and growth factor signaling pathways. This article reviews recent studies regarding some malignant mesothelioma molecular targets not only for cancer prevention but also for cancer therapy.

Altered functions of alveolar macrophages and NK cells involved in asbestos-related diseases

Asbestos exposure causes asbestosis and malignant mesothelioma, disorders which remain difficult to cure. We focused on alveolar macrophages (AM) and natural killer (NK) cells in asbestosis and mesothelioma, respectively, and examined their functions upon exposure to asbestos or in patients with mesothelioma. Exposure to asbestos caused rat AM to exhibit high production of transforming growth factor-beta (TGF-β) with prolonged survival in the absence of other cells, not simultaneously with the apoptosis caused by asbestos. The NK cell line showed impaired cytotoxicity with altered expression of activating receptors upon exposure to asbestos, and primary NK cells in culture with asbestos and peripheral blood NK cells in mesothelioma shared a decrease in expression of NKp46, a representative activating receptor. The AM finding indicates that AM contribute to asbestosis by playing a direct role in the fibrogenic response, as well as the inflammatory response. The response of NK cells indicates that exposure to asbestos has an immune-suppressive effect, as well as a tumorigenic effect. Our studies therefore reveal novel effects of asbestos exposure on AM and tumor immunity, which may represent valuable information for construction of a strategy for prevention and cure of asbestosis and malignant mesothelioma.

Extracellular signal-regulated kinase 5: a potential therapeutic target for malignant mesotheliomas

PURPOSE

Malignant mesothelioma is a devastating disease with a need for new treatment strategies. In the present study, we showed the importance of extracellular signal-regulated kinase 5 (ERK5) in malignant mesothelioma tumor growth and treatment.

EXPERIMENTAL DESIGN

ERK5 as a target for malignant mesothelioma therapy was verified using mesothelial and mesothelioma cell lines as well as by xenograft severe combined immunodeficient (SCID) mouse models.

RESULTS

We first showed that crocidolite asbestos activated ERK5 in LP9 cells and mesothelioma cell lines exhibit constitutive activation of ERK5. Addition of doxorubicin resulted in further activation of ERK5 in malignant mesothelioma cells. ERK5 silencing increased doxorubicin-induced cell death and doxorubicin retention in malignant mesothelioma cells. In addition, shERK5 malignant mesothelioma lines exhibited both attenuated colony formation on soft agar and invasion of malignant mesothelioma cells in vitro that could be related to modulation of gene expression linked to cell proliferation, apoptosis, migration/invasion, and drug resistance as shown by microarray analysis. Most importantly, injection of shERK5 malignant mesothelioma cell lines into SCID mice showed significant reduction in tumor growth using both subcutaneous and intraperitoneal models. Assessment of selected human cytokine profiles in peritoneal lavage fluid from intraperitoneal shERK5 and control tumor-bearing mice showed that ERK5 was critical in regulation of various proinflammatory (RANTES/CCL5, MCP-1) and angiogenesis-related (interleukin-8, VEGF) cytokines. Finally, use of doxorubicin and cisplatin in combination with ERK5 inhibition showed further reduction in tumor weight and volume in the intraperitoneal model of tumor growth.

CONCLUSION

ERK5 inhibition in combination with chemotherapeutic drugs is a beneficial strategy for combination therapy in patients with malignant mesothelioma.

Effect of chemical composition and state of the surface on the toxic response to high aspect ratio nanomaterials

Nanomaterials often act as a double sword. On the one hand they offer exceptional new properties, but on the other hand show signs of toxicity. High aspect ratio nanomaterials (HARNs) cause more concern than isometric nanoparticles owing to their physical similarity with asbestos. Many compounds may be prepared in fibrous shape with nano-sized diameter differing one from the other in various ways. This article reports a comparative picture of the chemical features and related toxic responses to a variety of HARNs, namely carbon nanotubes, asbestos, carbon nanofibers, oxide and metal wires and rods. In spite of similarities in form, durability and several biological responses elicited in vitro and in vivo, carbon nanotubes - opposite to asbestos - quench radicals, are hydrophobic and may be fully purified from metal impurities. Most of the other HARNs produced so far are metal or metal oxide compounds, less biopersistent than carbon nanotubes.

Toxic responses in primary rat hepatocytes exposed with occupational dust collected from work environment of bone-based industrial unit

In this in vitro study we investigated the toxic responses in hepatocytes treated with occupational dust to which workers are exposed in bone-based industrial units. The present study investigated the toxicity mechanism of bone-based occupational dust, from a particular industrial unit, on isolated rat hepatocytes. The hepatocytes were isolated by collagenase perfusion method and cell viability was determined by trypan blue exclusion and MTT [3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay treated with occupational dust at 0.1-1.0 mgmL(-1), for 120 min. The cell viability decreased significantly in a concentration-dependent manner. Dust induced significant membrane damage measured by lactate dehydrogenase (LDH) and glutathione (GSH) release in culture media for 30-, 60- and 120 min treatment duration. The toxicity was found to be correlated with the induction of lipid peroxidation (LPO). In addition, nitric oxide (NO), and hydrogen peroxide (H(2)O(2)) generation by occupational dusts were also found to be time- and concentration-dependent. Over all the present study provides initial evidences for the toxic potential of occupational dust generated in bone-based industries and, therefore, the dust exposure to workers in unorganized industrial units should be controlled.

The diagnostic utility of p16 FISH and GLUT-1 immunohistochemical analysis in mesothelial proliferations

Two promising ancillary tests used in the diagnosis of mesothelioma include GLUT-1 immunohistochemical analysis and fluorescence in situ hybridization (FISH) testing for the p16 deletion. This study compared the diagnostic usefulness of p16 FISH and GLUT-1 immunohistochemical analysis in the diagnosis of mesothelial proliferations in 158 cases with a diagnosis of benign (45.4%), atypical (10.4%), or malignant/mesothelioma (44.2%). Of the 70 benign cases, none had a deletion of p16 and 5 cases (7%) were positive for GLUT-1. Of the 68 mesotheliomas, 40 (59%) had a deletion of p16 (sensitivity, 59%; specificity, 100%) and 27 (40%) were positive for GLUT-1 (sensitivity, 40%; specificity, 93%). GLUT-1 showed lower sensitivity in pleural (56% vs 70%) and peritoneal (29% vs 51%) mesotheliomas (P = .004). Our results demonstrate that p16 FISH is a more sensitive and specific test than GLUT-1 immunohistochemical analysis and can be a more reliable ancillary tool to support the diagnosis of mesothelioma.

[Management of pleural disease]

In view of the presentations in the First National Forum of Trainee Pneumologists, the present article focuses on infectious pleural effusions and on the study of possible markers of malignant disease in asbestos-exposed individuals. The yield of the distinct techniques for the diagnosis of tuberculous pleural effusion is assessed, with emphasis on analysis of sputum and pleural samples (fluid and tissue) for Mycobacteriumtuberculosis. The utility of adenosine deaminase (ADA) (in the absence of empyema, ADA > 70 U/l is diagnostic of tuberculous pleurisy, while values of less than 40 U/l exclude this diagnosis) and interferon gamma in pleural fluid (cut off: 3.7 Ul/ml) is also discussed. The management of complicated parapneumonic pleural effusions is stratified in four categories, depending on the anatomical and morphological (size and eventual presence of loculations), bacteriological (positivity or negativity of pleural fluid culture) and biochemical (pH/glucose) characteristics of the effusion. Finally, recently developed markers for the evaluation and follow-up of asbestos-exposed individuals are described, with special emphasis on serum determination of mesothelin levels, which seem highly promising as a marker of the development of mesothelioma in these cases. A multicenter study currently being performed in Spain found that soluble mesothelin-related protein (SMRP) levels higher than 0.55 nmol/L showed a sensitivity and specificity of 72% for the diagnosis of epithelial malignant mesothelioma.

Antioxidants prevent the RhoA inhibition evoked by crocidolite asbestos in human mesothelial and mesothelioma cells

Asbestos is a naturally occurring fibrous silicate, whose inhalation is highly related to the risk of developing malignant mesothelioma (MM), and crocidolite is one of its most oncogenic types. The mechanism by which asbestos may cause MM is unclear. We have previously observed that crocidolite in human MM (HMM) cells induces NF-κB activation and stimulates the synthesis of nitric oxide by inhibiting the RhoA signaling pathway. In primary human mesothelial cells (HMCs) and HMM cells exposed to crocidolite asbestos, coincubated or not with antioxidants, we evaluated cytotoxicity and oxidative stress induction (lipid peroxidation) and the effect of asbestos on the RhoA signaling pathway (RhoA GTP binding, Rho kinase activity, RhoA prenylation, hydroxy-3-methylglutharyl-CoA reductase activity). In this paper we show that the reactive oxygen species generated by the incubation of crocidolite with primary HMCs and three HMM cell lines mediate the inhibition of 3-hydroxy-3-methylglutharyl-CoA reductase (HMGCR). The coincubation of HMCs and HMM cells with crocidolite together with antioxidants, such as Tempol, Mn-porphyrin, and the association of superoxide dismutase and catalase, prevented the cytotoxicity and lipoperoxidation caused by crocidolite alone as well as the decrease of HMGCR activity and restored the RhoA/RhoA-dependent kinase activity and the RhoA prenylation. The same effect was observed when the oxidizing agent menadione was administrated to the cells in place of crocidolite. Such a mechanism could at least partly explain the effects exerted by crocidolite fibers in mesothelial cells.

A critical review of the biological mechanisms underlying the in vivo and in vitro toxicity of carbon nanotubes: The contribution of physico-chemical characteristics

This critical review of the available human health safety data, relating to carbon nanotubes (CNTs), was conducted in order to assess the risks associated with CNT exposure. Determining the toxicity related to CNT exploitation is of great relevance and importance due to the increased potential for human exposure to CNTs within occupational, environmental and consumer settings. When this information is combined with knowledge on the likely exposure levels of humans to CNTs, it will enable risk assessments to be conducted to assess the risks posed to human health. CNTs are a diverse group of materials and vary with regards to their wall number (single and multi-walled CNTs are evident), length, composition, and surface chemistry. The attributes of CNTs that were identified as being most likely to drive the observed toxicity have been considered, and include CNT length, metal content, tendency to aggregate/agglomerate and surface chemistry. Of particular importance, is the contribution of the fibre paradigm to CNT toxicity, whereby the length of CNTs appears to be critical to their toxic potential. Mechanistic processes that are critical to CNT toxicity will also be discussed, with the findings insinuating that CNTs can exert an oxidative response that stimulates inflammatory, genotoxic and cytotoxic consequences. Consequently, it may transpire that a common mechanism is responsible for driving CNT toxicity, despite the fact that CNTs are a diverse population of materials. The similarity of the structure of CNTs to that of asbestos has prompted concern surrounding the exposure of humans, and so the applicability of the fibre paradigm to CNTs will be evaluated. It is also necessary to determine the systemic availability of CNTs following exposure, to determine where potential targets of toxicity are, and to thereby direct in vitro investigations within the most appropriate target cells. CNTs are therefore a group of materials whose useful exploitable properties prompts their increased production and utilization within diverse applications, so that ensuring their safety is of vital importance.

Review of carbon nanotubes toxicity and exposure--appraisal of human health risk assessment based on open literature

Carbon nanotubes (CNTs) possess many unique electronic and mechanical properties and are thus interesting for numerous novel industrial and biomedical applications. As the level of production and use of these materials increases, so too does the potential risk to human health. This study aims to investigate the feasibility and challenges associated with conducting a human health risk assessment for carbon nanotubes based on the open literature, utilising an approach similar to that of a classical regulatory risk assessment. Results indicate that the main risks for humans arise from chronic occupational inhalation, especially during activities involving high CNT release and uncontrolled exposure. It is not yet possible to draw definitive conclusions with regards the potential risk for long, straight multi-walled carbon nanotubes to pose a similar risk as asbestos by inducing mesothelioma. The genotoxic potential of CNTs is currently inconclusive and could be either primary or secondary. Possible systemic effects of CNTs would be either dependent on absorption and distribution of CNTs to sensitive organs or could be induced through the release of inflammatory mediators. In conclusion, gaps in the data set in relation to both exposure and hazard do not allow any definite conclusions suitable for regulatory decision-making. In order to enable a full human health risk assessment, future work should focus on the generation of reliable occupational, environmental and consumer exposure data. Data on toxicokinetics and studies investigating effects of chronic exposure under conditions relevant for human exposure should also be prioritised.

Genetically engineered oncolytic Newcastle disease virus effectively induces sustained remission of malignant pleural mesothelioma

Malignant pleural mesothelioma is a highly aggressive tumor. Alternative treatment strategies such as oncolytic viral therapy may offer promising treatment options in the future. In this study, the oncolytic efficacy and induction of tumor remission by a genetically engineered Newcastle disease virus [NDV; NDV(F3aa)-GFP; GFP, green fluorescent protein] in malignant pleural mesothelioma is tested and monitored by bioluminescent tumor imaging. The efficacy of NDV(F3aa)-GFP was tested against several mesothelioma cell lines in vitro. Firefly luciferase-transduced MSTO-211H* orthotopic pleural mesothelioma tumor-bearing animals were treated with either single or multiple doses of NDV(F3aa)-GFP at different time points (days 1 and 10) after tumor implantation. Tumor burden was assessed by bioluminescence imaging. Mesothelioma cell lines exhibited dose-dependent susceptibility to NDV lysis in the following order of sensitivity: MSTO-211H > MSTO-211H* > H-2452 > VAMT > JMN. In vivo studies with MSTO-211H* cells showed complete response to viral therapy in 65% of the animals within 14 days after treatment initiation. Long-term survival in all of these animals was >50 days after tumor installation (control animals, <23 d). Multiple treatment compared with single treatment showed a significantly better response (P = 0.005). NDV seems to be an efficient viral oncolytic agent in the therapy of malignant pleural mesothelioma in an orthotopic pleural mesothelioma tumor model.

Mechanisms by which inflammation may increase intestinal cancer risk in inflammatory bowel disease

Patients with ulcerative colitis and Crohn's disease are at increased risk of developing intestinal cancers via mechanisms that remain incompletely understood. However, chronic inflammation and repeated events of inflammatory relapse in inflammatory bowel disease (IBD) expose these patients to a number of signals known to have tumorigenic effects including persistent activation of the nuclear factor-kappaB and cyclooxygenase-2/prostaglandin pathways, release of proinflammatory mediators such as tumor necrosis factor-alpha and interleukin-6, and enhanced local levels of reactive oxygen and nitrogen species. These inflammatory signals can contribute to carcinogenesis via 3 major processes: 1) by increasing oxidative stress, which promotes DNA mutagenesis thus contributing to tumor initiation; 2) by activating prosurvival and antiapoptotic pathways in epithelial cells, thereby contributing to tumor promotion; and 3) by creating an environment that supports sustained growth, angiogenesis, migration, and invasion of tumor cells, thus supporting tumor progression and metastasis. The present review integrates clinical and basic research observations in an attempt to provide a comprehensive understanding of how inflammatory processes may contribute to intestinal cancer development in IBD patients.

In Vitro Study of Mutagenesis Induced by Crocidolite-Exposed Alveolar Macrophages NR8383 in Cocultured Big Blue Rat2 Embryonic Fibroblasts

Asbestos-induced mutagenicity in the lung may involve reactive oxygen/nitrogen species (ROS/RNS) released by alveolar macrophages. With the aim of proposing an alternative in vitro mutagenesis test, a coculture system of rat alveolar macrophages (NR8383) and transgenic Big Blue Rat2 embryonic fibroblasts was developed and tested with a crocidolite sample. Crocidolite exposure induced no detectable increase in ROS production from NR8383, contrasting with the oxidative burst that occurred following a brief exposure (1 hour) to zymosan, a known macrophage activator. In separated cocultures, crocidolite and zymosan induced different changes in the gene expressions involved in cellular inflammation in NR8383 and Big Blue. In particular, both particles induced up-regulation of iNOS expression in Big Blue, suggesting the formation of potentially genotoxic nitrogen species. However, crocidolite exposure in separated or mixed cocultures induced no mutagenic effects whereas an increase in Big Blue mutants was detected after exposure to zymosan in mixed cocultures. NR8383 activation by crocidolite is probably insufficient to induce in vitro mutagenic events. The mutagenesis assay based on the coculture of NR8383 and Big Blue cannot be used as an alternative in vitro method to assess the mutagenic properties of asbestos fibres.

Antiproliferative effect of Aurora kinase targeting in mesothelioma

The Aurora proteins are a small family of serine/threonine kinase that function in various stages of mitosis. Current interest in Aurora kinase relates to its role in tumours, and its potential as a therapeutic target. In this work we studied the expression of Aurora kinases A and B and related genes in human mesothelioma tissues and in five mesothelioma cell lines. Moreover, we analyzed the effects of ZM447439 (ZM), an Aurora kinase inhibitor, on cellular growth. Results evidenced an over-expression of Aurora kinase A and related genes in human mesothelioma tissues and an over-expression of Aurora kinases A and B in all cell lines. Moreover, we demonstrated that ZM447439 was able to inhibit cell growth in all cell lines and that this inhibition was due to a specific effect as demonstrated by the reduction in the level of Histone H3 phosphorylation. Our findings support a role of Aurora kinase in mesothelioma and the possibility of using Aurora kinase inhibitors in therapeutic modalities.