The Cappadocia mesothelioma epidemic: its influence in Turkey and abroad

Established and new treatment roadmaps for pleural mesothelioma: opinions of the Turkish Collaborative Group

Pleural mesothelioma (PM) is a cancer of the pleural surface, which is aggressive and may be rapidly fatal. PM is a rare cancer worldwide, but is a relatively common disease in Turkey. Asbestos exposure is the main risk factor and the most common underlying cause of the disease. There have been significant improvements in diagnoses and treatments of many malignancies; however, there are still therapeutic challenges in PM. In this review, we aimed to increase the awareness of health care professionals, oncologists, and pulmonologists by underlining the unmet needs of patients with PM and by emphasizing the need for a multidisciplinary treatment and management of PM. After reviewing the general information about PM, we further discuss the treatment options for patients with PM using immunotherapy and offer evidence for improvements in the clinical outcomes of these patients because of these newer treatment modalities.

The Role of Germline Mutations in Thoracic Malignancies: Between Myth and Reality

Considering the established contribution of environmental factors to the development of thoracic malignancies, the inherited susceptibility of these tumors has rarely been explored. However, the recent introduction of next-generation sequencing-based tumor molecular profiling in the real-word setting enabled us to deeply characterize the genomic background of patients with lung cancer with or without smoking-related history, increasing the likelihood of detecting germline mutations with potential prevention and treatment implications. Pathogenic germline variants have been detected in 2% to 3% of patients with NSCLC undergoing next-generation sequencing analysis, whereas the proportion of germline mutations associated with the development of pleural mesothelioma widely varies across different studies, ranging between 5% and 10%. This review provides an updated summary of emerging evidence about germline mutations in thoracic malignancies, focusing on pathogenetic mechanisms, clinical features, therapeutic implications, and screening recommendations for high-risk individuals.

The crystal structure of the killer fibre erionite from Tuzköy (Cappadocia, Turkey)

Erionite is a non-asbestos fibrous zeolite classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen and is considered today similar to or even more carcinogenic than the six regulated asbestos minerals. Exposure to fibrous erionite has been unequivocally linked to cases of malignant mesothelioma (MM) and this killer fibre is assumed to be directly responsible for more than 50% of all deaths in the population of the villages of Karain and Tuzköy in central Anatolia (Turkey). Erionite usually occurs in bundles of thin fibres and very rarely as single acicular or needle-like fibres. For this reason, a crystal structure of this fibre has not been attempted to date although an accurate characterization of its crystal structure is of paramount importance for our understanding of the toxicity and carcinogenicity. In this work, we report on a combined approach of microscopic (SEM, TEM, electron diffraction), spectroscopic (micro-Raman) and chemical techniques with synchrotron nano-single-crystal diffraction that allowed us to obtain the first reliable ab initio crystal structure of this killer zeolite. The refined structure showed regular T-O distances (in the range 1.61-1.65 Å) and extra-framework content in line with the chemical formula (K2.63Ca1.57Mg0.76Na0.13Ba0.01)[Si28.62Al7.35]O72·28.3H2O. The synchrotron nano-diffraction data combined with three-dimensional electron diffraction (3DED) allowed us to unequivocally rule out the presence of offretite. These results are of paramount importance for understanding the mechanisms by which erionite induces toxic damage and for confirming the physical similarities with asbestos fibres.

Current causes of mesothelioma: how has the asbestos ban changed the perspective?

The association of mesothelioma, a lethal lung disease, with asbestos has led to an absolute ban on asbestos in at least 55 countries worldwide. The purpose of this paper is to review residual exposure to asbestos as well as other emerging causes of mesothelioma outside asbestos. The review provides detailed description of asbestos minerals, their geographical locations, mesothelioma in these areas, as well as contemporary possible sources of asbestos exposure. Second, we examine other emerging causes of mesothelioma including: ionizing radiation as the second most important risk factor after asbestos, particularly relevant to patients undergoing radiotherapy, third, carbon nanotubes which are under investigation and fourth, Simian virus 40. In the case of asbestos per se, the greatest risk is from occupational exposure during mining and subsequent processing. Of the non-occupational exposures, environmental exposure is most serious, followed by exposure from indoor asbestos minerals and secondary familial exposure. Overall, asbestos is still a major risk factor, but alternative causes should not be neglected, especially in young people, in women and those with a history of radiotherapy or living in high-risk locations.

Global magnitude and temporal trend of mesothelioma burden along with the contribution of occupational asbestos exposure in 204 countries and territories from 1990 to 2019: Results from the Global Burden of Disease Study 2019

Understanding the burden of mesothelioma with the contribution of occupational asbestos exposure globally provides essential foundations for cancer control, policy decisions and resource allocation. Globally, 34,511 incident cases, 29,251 deaths and 668,104 disability-adjusted life years (DALYs) of mesothelioma were estimated in 2019. The age-standardized rates of incidence, mortality and DALYs all showed a slightly declining trend over the past 30 years, but the latest absolute number of mesothelioma burden almost doubled since 1990. The burden rate decreased among the population aged under 70 years, but increased among the population aged over 80 years, especially in the High socio-demographic index (SDI) region. The burden rate of mesothelioma attributable to asbestos exposure was positively associated with SDI at the national level. This study depicted a continuous increase in mesothelioma burden globally over the past 30 years. Controlling occupational asbestos exposure will reduce the mesothelioma burden, especially for higher SDI regions.

A3 Adenosine and P2X7 Purinergic Receptors as New Targets for an Innovative Pharmacological Therapy of Malignant Pleural Mesothelioma

Human malignant pleural mesothelioma (MPM) is a rare, but aggressive tumor of the serosal cavities whose 5-year survival rate is 15%. At present, there are no effective therapies for MPM. Although recent findings suggest that A3 adenosine (A3AR) and P2X7 (P2X7R) receptors can be employed as antitumoral pharmacological targets in MPM, their potential role in a combined therapy is currently unknown. The A3AR agonist Cl-IB-MECA and the P2X7 receptor antagonist AZ10606120, as a single compound or in combination, were investigated in vitro for their anti-tumor activities. Assays were carried out in MPM cell lines IST-Mes2 and MPP89 and in primary human normal mesothelial cells (HMCs), as control. Single treatment with Cl-IB-MECA reduced cell proliferation and favored a pro-apoptotic effect in both MPP89 and IST-Mes2 cell lines, whereas AZ10606120 inhibited cell proliferation and induced apoptosis in IST-Mes2, only. The combined treatment with Cl-IB-MECA and AZ10606120 reduced cell proliferation and favored apoptosis in MPP89 and IST-Mes2 cell lines, whereas no synergistic effect was detected. These data cumulatively suggest the absence of a synergistic effect in combined targeting of A3 adenosine and P2X7 receptors of MPM cell lines. This study may stimulate further investigations aimed at determining new combinations of antitumor compounds and more effective therapeutic strategies against MPM.

Asbestos in High-Risk Communities: Public Health Implications

Asbestos-related diseases (ARDs)-mesothelioma, lung cancer, and asbestosis-are well known as occupational diseases. As industrial asbestos use is eliminated, ARDs within the general community from para-occupational, environmental, and natural exposures are more prominent. ARD clusters have been studied in communities including Broni, Italy; Libby, Montana; Wittenoom, Western Australia; Karain, Turkey; Ambler, Pennsylvania; and elsewhere. Community ARDs pose specific public health issues and challenges. Community exposure results in higher proportions of mesothelioma in women and a younger age distribution than occupational exposures. Exposure amount, age at exposure, fiber type, and genetic predisposition influence ARD expression; vulnerable groups include those with social and behavioral risk, exposure to extreme events, and genetic predispositions. To address community exposure, regulations should address all carcinogenic elongated mineral fibers. Banning asbestos mining, use, and importation will not reduce risks from asbestos already in place. Residents of high-risk communities are characteristically exposed through several pathways differing among communities. Administrative responsibility for controlling environmental exposures is more diffuse than for workplaces, complicated by diverse community attitudes to risk and prevention and legal complexity. The National Mesothelioma Registries help track the identification of communities at risk. High-risk communities need enhanced services for screening, diagnosis, treatment, and social and psychological support, including for retired asbestos workers. Legal settlements could help fund community programs. A focus on prevention, public health programs, particularization to specific community needs, and participation is recommended.

Tumour predisposition and cancer syndromes as models to study gene-environment interactions

Cell division and organismal development are exquisitely orchestrated and regulated processes. The dysregulation of the molecular mechanisms underlying these processes may cause cancer, a consequence of cell-intrinsic and/or cell-extrinsic events. Cellular DNA can be damaged by spontaneous hydrolysis, reactive oxygen species, aberrant cellular metabolism or other perturbations that cause DNA damage. Moreover, several environmental factors may damage the DNA, alter cellular metabolism or affect the ability of cells to interact with their microenvironment. While some environmental factors are well established as carcinogens, there remains a large knowledge gap of others owing to the difficulty in identifying them because of the typically long interval between carcinogen exposure and cancer diagnosis. DNA damage increases in cells harbouring mutations that impair their ability to correctly repair the DNA. Tumour predisposition syndromes in which cancers arise at an accelerated rate and in different organs - the equivalent of a sensitized background - provide a unique opportunity to examine how gene-environment interactions influence cancer risk when the initiating genetic defect responsible for malignancy is known. Understanding the molecular processes that are altered by specific germline mutations, environmental exposures and related mechanisms that promote cancer will allow the design of novel and effective preventive and therapeutic strategies.

Biological Mechanisms and Clinical Significance of BAP1 Mutations in Human Cancer

Among more than 200 BAP1-mutant families affected by the "BAP1 cancer syndrome," nearly all individuals inheriting a BAP1 mutant allele developed one or more malignancies during their lifetime, mostly uveal and cutaneous melanoma, mesothelioma, and clear-cell renal cell carcinoma. These cancer types are also those that, when they occur sporadically, are more likely to carry somatic biallelic BAP1 mutations. Mechanistic studies revealed that the tumor suppressor function of BAP1 is linked to its dual activity in the nucleus, where it is implicated in a variety of processes including DNA repair and transcription, and in the cytoplasm, where it regulates cell death and mitochondrial metabolism. BAP1 activity in tumor suppression is cell type- and context-dependent. BAP1 has emerged as a critical tumor suppressor across multiple cancer types, predisposing to tumor development when mutated in the germline as well as somatically. Moreover, BAP1 has emerged as a key regulator of gene-environment interaction.This article is highlighted in the In This Issue feature, p. 1079.

Circulating Epigenetic Biomarkers in Malignant Pleural Mesothelioma: State of the Art and critical Evaluation

Malignant pleural mesothelioma (MPM) is a rare and aggressive cancer, which originates from the mesothelial cells of the pleura and is associated with asbestos exposure. In light of its aggressive nature, late diagnosis and dismal prognosis, there is an urgent need for identification of biomarkers in easily accessible samples (such as blood) for early diagnosis of MPM. In the last 10 years, epigenetic markers, such as DNA methylation and microRNAs (miRNAs), have gained popularity as possible early diagnostic and prognostic biomarkers in cancer research. The aim of this review is to provide a critical analysis of the current evidences on circulating epigenetic biomarkers for MPM and on their translational potential to the clinical practice for early diagnosis and for prognosis.

Diffuse epithelioid malignant mesothelioma of the pleura presenting as a hydropneumothorax and vertebral body invasion

Malignant mesothelioma is an uncommon form of neoplastic transformation of the mesothelial cells that line the serosal surfaces of the body. It most commonly affects the pleura and is often associated with pleural effusions and pleural-based masses. The annual incidence in the United States is only 3300 cases, representing less than 0.3% of all cancers worldwide, although this is likely underestimated. We present a case of diffuse epithelioid malignant pleural mesothelioma in a patient with remote, short-term asbestos exposure complicated by recurrent left-sided hydropneumothoraces and pleural-based invasion of the T12 vertebral body, which represent two rare coexisting complications. This case illustrates the importance of maintaining a broad differential for hydropneumothorax, particularly as the risk factors may be decades removed and the degree of asbestos exposure to induce a malignant mesothelioma may be smaller than has been traditionally thought.

Mesothelioma: Scientific clues for prevention, diagnosis, and therapy

Mesothelioma affects mostly older individuals who have been occupationally exposed to asbestos. The global mesothelioma incidence and mortality rates are unknown, because data are not available from developing countries that continue to use large amounts of asbestos. The incidence rate of mesothelioma has decreased in Australia, the United States, and Western Europe, where the use of asbestos was banned or strictly regulated in the 1970s and 1980s, demonstrating the value of these preventive measures. However, in these same countries, the overall number of deaths from mesothelioma has not decreased as the size of the population and the percentage of old people have increased. Moreover, hotspots of mesothelioma may occur when carcinogenic fibers that are present in the environment are disturbed as rural areas are being developed. Novel immunohistochemical and molecular markers have improved the accuracy of diagnosis; however, about 14% (high-resource countries) to 50% (developing countries) of mesothelioma diagnoses are incorrect, resulting in inadequate treatment and complicating epidemiological studies. The discovery that germline BRCA1-asssociated protein 1 (BAP1) mutations cause mesothelioma and other cancers (BAP1 cancer syndrome) elucidated some of the key pathogenic mechanisms, and treatments targeting these molecular mechanisms and/or modulating the immune response are being tested. The role of surgery in pleural mesothelioma is controversial as it is difficult to predict who will benefit from aggressive management, even when local therapies are added to existing or novel systemic treatments. Treatment outcomes are improving, however, for peritoneal mesothelioma. Multidisciplinary international collaboration will be necessary to improve prevention, early detection, and treatment.

Micro-Raman Spectroscopy, a Powerful Technique Allowing Sure Identification and Complete Characterization of Asbestiform Minerals

Micro-Raman spectroscopy has been applied to fibrous minerals regulated as “asbestos”—anthophyllite, actinolite, amosite, crocidolite, tremolite, and chrysotile—responsible of severe diseases affecting mainly, but not only, the respiratory system. The technique proved to be powerful in the identification of the mineral phase and in the recognition of particles of carbonaceous materials (CMs) lying on the “asbestos” fibers surface. Also, erionite, a zeolite mineral, from different outcrops has been analyzed. To erionite has been ascribed the peak of mesothelioma noticed in Cappadocia (Turkey) during the 1970s. On the fibers, micro-Raman spectroscopy allowed to recognize many grains, micrometric in size, of iron oxy-hydroxides or potassium iron sulphate, in erionite from Oregon, or particles of CMs, in erionite from North Dakota, lying on the crystal surface. Raman spectroscopy appears therefore to be the technique allowing, without preparation of the sample, a complete characterization of the minerals and of the associated phases.

A case from India of pleural malignant mesothelioma probably due to domestic and environmental asbestos exposure: a posthumous report

India is the largest consumer of asbestos in the world. There is no report from India of mesothelioma related to asbestos. The case is a 42-year-old man who died of pleural mesothelioma. He was exposed to asbestos domestically and from the environment since birth. Two of his close family members worked in a factory that used asbestos. The living quarter of the family was within the premises of the factory. Asbestos waste was strewn on the grounds surrounding the quarters. After decades of legal battles by workers and families exposed to asbestos, Indian courts have ordered remedial measures and compensation to people, who are exposed to asbestos at work and the environment. Mesothelioma, currently in epidemic proportions in the west where asbestos production was banned in the 1990s, could rise to alarming levels in the next decades in India if the legal remedial measures are not implemented soon.

Gene expression profiling of homologous recombination repair pathway indicates susceptibility for olaparib treatment in malignant pleural mesothelioma in vitro

BACKGROUND

Malignant pleural mesothelioma (MPM) is a tumour arising from pleural cavities with poor prognosis. Multimodality treatment with pemetrexed combined with cisplatin shows unsatisfying response-rates of 40%. The reasons for the rather poor efficacy of chemotherapeutic treatment are largely unknown. However, it is conceivable that DNA repair mechanisms lead to an impaired therapy response. We hypothesize a major role of homologous recombination (HR) for genome stability and survival of this tumour. Therefore, we analysed genes compiled under the term "BRCAness". An inhibition of this pathway with olaparib might abrogate this effect and induce apoptosis.

METHODS

We investigated the response of three MPM cell lines and lung fibroblasts serving as a control to treatment with pemetrexed, cisplatin and olaparib. Furthermore, we aimed to find possible correlations between response and gene expression patterns associated with BRCAness phenotype. Therefore, 91 clinical MPM samples were digitally screened for gene expression patterns of HR members.

RESULTS

A BRCAness-dependent increase of apoptosis and senescence during olaparib-based treatment of BRCA-associated-protein 1 (BAP1)-mutated cell lines was observed. The gene expression pattern identified could be found in approx. 10% of patient samples. Against this background, patients could be grouped according to their defects in the HR system. Gene expression levels of Aurora Kinase A (AURKA), RAD50 as well as DNA damage-binding protein 2 (DDB2) could be identified as prognostic markers in MPM.

CONCLUSIONS

Defects in HR compiled under the term BRCAness are a common event in MPM. The present data can lead to a better understanding of the underlaying cellular mechanisms and leave the door wide open for new therapeutic approaches for this severe disease with infaust prognosis. Response to Poly (ADP-ribose)-Polymerase (PARP)-Inhibition could be demonstrated in the BAP1-mutated NCI-H2452 cells, especially when combined with cisplatin. Thus, this combination therapy might be effective for up to 2/3 of patients, promising to enhance patients' clinical management and outcome.

Consensus report of the 8 and 9th Weinman Symposia on Gene x Environment Interaction in carcinogenesis: novel opportunities for precision medicine

The relative contribution of intrinsic genetic factors and extrinsic environmental ones to cancer aetiology and natural history is a lengthy and debated issue. Gene-environment interactions (G x E) arise when the combined presence of both a germline genetic variant and a known environmental factor modulates the risk of disease more than either one alone. A panel of experts discussed our current understanding of cancer aetiology, known examples of G × E interactions in cancer, and the expanded concept of G × E interactions to include somatic cancer mutations and iatrogenic environmental factors such as anti-cancer treatment. Specific genetic polymorphisms and genetic mutations increase susceptibility to certain carcinogens and may be targeted in the near future for prevention and treatment of cancer patients with novel molecularly based therapies. There was general consensus that a better understanding of the complexity and numerosity of G × E interactions, supported by adequate technological, epidemiological, modelling and statistical resources, will further promote our understanding of cancer and lead to novel preventive and therapeutic approaches.

A Subset of Mesotheliomas With Improved Survival Occurring in Carriers of BAP1 and Other Germline Mutations

PURPOSE

We hypothesized that four criteria could help identify malignant mesotheliomas (MMs) most likely linked to germline mutations of BAP1 or of other genes: family history of MM, BAP1-associated cancers, or multiple malignancies; or age younger than 50 years.

PATIENTS AND METHODS

Over the course of 7 years, 79 patients with MM met the four criteria; 22 of the 79 (28%) reported possible asbestos exposure. They were screened for germline BAP1 mutations by Sanger sequencing and by targeted next-generation sequencing (tNGS) for germline mutations in 55 additional cancer-linked genes. Deleterious mutations detected by tNGS were validated by Sanger sequencing.

RESULTS

Of the 79 patients, 43 (16 probands and 27 relatives) had deleterious germline BAP1 mutations. The median age at diagnosis was 54 years and median survival was 5 years. Among the remaining 36 patients with no BAP1 mutation, median age at diagnosis was 45 years, median survival was 9 years, and 12 had deleterious mutations of additional genes linked to cancer. When compared with patients with MMs in the SEER cohort, median age at diagnosis (72 years), median survival for all MM stages (8 months), and stage I (11 months) were significantly different from the 79 patients with MM in the current study ( P < .0001).

CONCLUSION

We provide criteria that help identify a subset of patients with MM who had significantly improved survival. Most of these patients were not aware of asbestos exposure and carried either pathogenic germline mutations of BAP1 or of additional genes linked to cancer, some of which may have targeted-therapy options. These patients and their relatives are susceptible to development of additional cancers; therefore, genetic counseling and cancer screening should be considered.

Detecting germline BAP1 mutations in patients with peritoneal mesothelioma: benefits to patient and family members

Germline mutations in the BRCA-1 associated tumor protein 1 (BAP1) increase susceptibility to mesothelioma and other cancers. We describe a patient with a family history of peritoneal mesothelioma, who developed malignant peritoneal mesothelioma at age 45 in the absence of known asbestos exposure. These findings lead us to hypothesize that the mesothelioma occurred in the setting of germline a BAP1 mutation. This was confirmed by genetic testing. The subsequent therapeutic choices for the patient and testing of at-risk family members highlight the importance of recognizing this genetic syndrome and screening for individuals at high risk.

Assessing occupational erionite and respirable crystalline silica exposure among outdoor workers in Wyoming, South Dakota, and Montana

Erionite is a naturally occurring fibrous mineral found in many parts of the world, including the western United States. Inhalational exposure to erionite fibers in some localities is associated with health effects similar to those caused by asbestos exposure, including malignant mesothelioma. Therefore, there is concern regarding occupational exposures in the western United States. Currently, there are no standard sampling and analytical methods for airborne erionite fibers, as well as no established occupational exposure limits. Due to the potential adverse health effects, characterizing and minimizing exposures is prudent. Crystalline silica also occurs naturally in areas where erionite is found, principally as the mineral quartz. Work activities involving rocks containing quartz and soils derived from those rocks can lead to exposure to respirable crystalline silica (RCS). The typically dry and dusty environment of the western United States can increase the likelihood of exposures to aerosolized rocks and soils, but inhalation exposure is also possible in more humid conditions. In this case study, we describe several outdoor occupational environments with potential exposures to erionite and RCS. We describe our method for evaluating those exposures and demonstrate: (1) the occurrence of occupational exposures to airborne erionite and RCS, (2) that the chemical make-up of the erionite mineral can be determined, and (3) that effective dust control practices are needed to reduce employee exposures to these minerals.