Differential Susceptibility of Human Pleural and Peritoneal Mesothelial Cells to Asbestos Exposure

Ovarian tumor cell-derived JAGGED2 promotes omental metastasis through stimulating the Notch signaling pathway in the mesothelial cells

The primary site of metastasis for epithelial ovarian cancer (EOC) is the peritoneum, and it occurs through a multistep process that begins with adhesive contacts between cancer cells and mesothelial cells. Despite evidence that Notch signaling has a role in ovarian cancer, it is unclear how exactly it contributes to ovarian cancer omental metastasis, as well as the cellular dynamics and intrinsic pathways that drive this tropism. Here we show that tumor cells produced the Notch ligand Jagged2 is a clinically and functionally critical mediator of ovarian cancer omental metastasis by activating the Notch signaling in single-layered omental mesothelial cells. In turn, Jagged2 promotes tumor growth and therapeutic resistance by stimulating IL-6 release from mesothelial cells. Additionally, Jagged2 is a potent downstream mediator of the omental metastasis cytokine TGF-β that is released during omental destruction. Importantly, therapeutic inhibition of Jagged2-mediated omental metastasis was significantly improved by directly disrupting the Notch pathway in omental mesothelial cells. These findings highlight the key role of Jagged2 to the functional interplay between the TGF-β and the Notch signaling pathways during the metastatic process of ovarian cancer cells to the omentum and identify the Notch signaling molecule as a precision therapeutic target for ovarian cancer metastasis.

Functional Annotation Routines Used by ABRF Bioinformatics Core Facilities - Observations, Comparisons, and Considerations

The functional annotation of gene lists is a common analysis routine required for most genomics experiments, and bioinformatics core facilities must support these analyses. In contrast to methods such as the quantitation of RNA-Seq reads or differential expression analysis, our research group noted a lack of consensus in our preferred approaches to functional annotation. To investigate this observation, we selected 4 experiments that represent a range of experimental designs encountered by our cores and analyzed those data with 6 tools used by members of the Association of Biomolecular Resource Facilities (ABRF) Genomic Bioinformatics Research Group (GBIRG). To facilitate comparisons between tools, we focused on a single biological result for each experiment. These results were represented by a gene set, and we analyzed these gene sets with each tool considered in our study to map the result to the annotation categories presented by each tool. In most cases, each tool produces data that would facilitate identification of the selected biological result for each experiment. For the exceptions, Fisher's exact test parameters could be adjusted to detect the result. Because Fisher's exact test is used by many functional annotation tools, we investigated input parameters and demonstrate that, while background set size is unlikely to have a significant impact on the results, the numbers of differentially expressed genes in an annotation category and the total number of differentially expressed genes under consideration are both critical parameters that may need to be modified during analyses. In addition, we note that differences in the annotation categories tested by each tool, as well as the composition of those categories, can have a significant impact on results.

Intratumor microbiota as a novel potential prognostic indicator in mesothelioma

Introduction

Despite increased attention on immunotherapy, primarily immune checkpoint blockade, as a therapeutic approach for mesothelioma (MMe), its efficacy and tolerability remain questioned. One potential explanation for different responses to immunotherapy is the gut and intratumor microbiota; however, these remain an underexplored facet of MMe. This article highlights the cancer intratumor microbiota as a novel potential prognostic indicator in MMe.

Methods

TCGA data on 86 MMe patients from cBioPortal underwent bespoke analysis. Median overall survival was used to divide patients into “Low Survivors” and “High Survivors”. Comparison of these groups generated Kaplan-Meier survival analysis, differentially expressed genes (DEGs), and identification of differentially abundant microbiome signatures. Decontamination analysis refined the list of signatures, which were validated as an independent prognostic indicator through multiple linear regression modelling and Cox proportional hazards modelling. Finally, functional annotation analysis on the list of DEGs was performed to link the data together.

Results

107 genera signatures were significantly associated with patient survival (positively or negatively), whilst clinical characteristic comparison between the two groups demonstrated that epithelioid histology was more common in “High Survivors” versus biphasic in “Low Survivors”. Of the 107 genera, 27 had published articles related to cancer, whilst only one (Klebsiella) had MMe-related published articles. Functional annotation analysis of the DEGs between the two groups highlighted fatty acid metabolism as the most enriched term in “High Survivors”, whilst for “Low Survivors” the enriched terms primarily related to cell cycle/division. Linking these ideas and findings together is that the microbiome influences, and is influenced by, lipid metabolism. Finally, to validate the independent prognostic value of the microbiome, multiple linear regression modelling as well as Cox proportional hazards modelling were employed, with both approaches demonstrating that the microbiome was a better prognostic indicator than patient age or stage of the cancer.

Discussion

The findings presented herein, alongside the very limited literature from scoping searches to validate the genera, highlight the microbiome and microbiota as a potentially rich source of fundamental analysis and prognostic value. Further in vitro studies are needed to elucidate the molecular mechanisms and functional links that may lead to altered survival.

Primary Peritoneal Mesothelioma: Diagnostic Challenges of This Lethal Imposter

Primary Peritoneal Mesothelioma is a rapidly aggressive and rare neoplasm that arises from the lining of mesothelial cells of the peritoneum and spreads extensively within the confines of the abdominal cavity. The pathogenesis of all forms of mesothelioma is strongly associated with industrial pollutants, of which asbestos is the principal carcinogen. Characteristically, asbestos exposure has a strong relationship with mesothelioma of the pleura, but the peritoneal cavity is the second most commonly affected site. Additionally, in contrast to pleural mesothelioma, which has a male predominance (male-female ratio of between four and five to one), women comprise approximately one-half of all cases of malignant peritoneal mesothelioma. A thorough history of occupational/paraoccupational exposure along with histopathology is the key to timely diagnosis and treatment.

Development of alginate and gelatin-based pleural and tracheal sealants

Pleural and tracheal injuries remain significant problems, and an easy to use, effective pleural or tracheal sealant would be a significant advance. The major challenges are requirements for adherence, high strength and elasticity, dynamic durability, appropriate biodegradability, and lack of cell or systemic toxicity. We designed and evaluated two sealant materials comprised respectively of alginate methacrylate and of gelatin methacryloyl, each functionalized by conjugation with dopamine HCl. Both compounds are cross-linked into easily applied as pre-formed hydrogel patches or as in situ hydrogels formed at the wound site utilizing FDA-approved photo-initiators and oxidants. Material testing demonstrates appropriate adhesiveness, tensile strength, burst pressure, and elasticity with no significant cell toxicity in vitro assessments. Air-leak was absent after sealant application to experimentally-induced injuries in ex-vivo rat lung and tracheal models and in ex vivo pig lungs. Sustained repair of experimentally-induced pleural injury was observed for up to one month in vivo rat models and for up to 2 weeks in vivo rat tracheal injury models without obvious air leak or obvious toxicities. The alginate-based sealant worked best in a pre-formed hydrogel patch whereas the gelatin-based sealant worked best in an in situ formed hydrogel at the wound site thus providing two potential approaches. These studies provide a platform for further pre-clinical and potential clinical investigations. STATEMENT OF SIGNIFICANCE: Pneumothorax and pleural effusions resulting from trauma and a range of lung diseases and critical illnesses can result in lung collapse that can be immediately life-threatening or result in chronic leaking (bronchopleural fistula) that is currently difficult to manage. This leads to significantly increased morbidity, mortality, hospital stays, health care costs, and other complications. We have developed sealants originating from alginate and gelatin biomaterials, each functionalized by methacryloylation and by dopamine conjugation to have desired mechanical characteristics for use in pleural and tracheal injuries. The sealants are easily applied, non-cytotoxic, and perform well in vitro and in vivo model systems of lung and tracheal injuries. These initial proof of concept investigations provide a platform for further studies.

New insights in the pathology of peritoneal surface malignancy

Pathology is central to the management of peritoneal surface malignancy. This article highlights some recent advances that have had an impact on patient management or could do so in the near future. Malignant peritoneal mesothelioma, particularly the epithelioid subtype, is amenable to radical therapy in selected cases, and factors such as ki67 proliferation index, expression of BAP1 and mutation in CDKN2A show promise as prognostic indicators. Our understanding of multicystic mesothelioma has improved in recent years; it is a true neoplasm for which surgery may be indicated. Serous carcinomas involving the peritoneum are now known to originate from tubal epithelium. They are of two distinct types, high grade and low grade, which are now recognized as different neoplasms with distinctive features, oncogenesis and behavior. Pseudomyxoma peritonei (PMP) is an unusual condition that usually arises from an appendiceal mucinous neoplasm. Recent consensus in the classification and nomenclature of these lesions is discussed, including the distinction between low grade and high grade appendiceal mucinous neoplasms (HAMN), and the diagnostic criteria for appendiceal adenocarcinoma. PMP is divided into four prognostic groups: acellular mucin, low grade mucinous carcinoma peritonei, high grade mucinous carcinoma peritonei, and high grade mucinous carcinoma peritonei with signet ring cells. The pseudomyxoma microbiome is a promising area for clinical intervention but has been the subject of little research activity. Goblet cell adenocarcinoma (previously known as 'goblet cell carcinoid') is a distinctive type of appendiceal adenocarcinoma. Its behavior correlates with histologic features, but no general consensus for classification has been reached.

Mouse models for mesothelioma drug discovery and development

INTRODUCTION

Mesothelioma is an aggressive mesothelial lining tumor. Available drug therapies include chemotherapeutic agents, targeted molecular therapies, and immune system modulators. Mouse models were instrumental in the discovery and evaluation of such therapies, but there is need for improved understanding of the role of inflammation, tumor heterogeneity, mechanisms of carcinogenesis, and the tumor microenvironment. Novel mouse models may provide new insights and drive drug therapy discovery that improves efficacy.

AREAS COVERED

This review concerns available mouse models for mesothelioma drug discovery and development including the advantages and disadvantages of each. Gaps in current knowledge of mesothelioma are highlighted, and future directions for mouse model research are considered.

EXPERT OPINION

Soon, CRISPR-Cas gene-editing will improve understanding of mesothelioma mechanisms foundational to the discovery and testing of efficacious therapeutic targets. There are at least two likely areas of upcoming methodology development. One is concerned with precise modeling of inflammation - is it a causal process whereby inflammatory signals contribute to tumor initiation, or is it a secondary passenger process driven by asbestos exposure effects? The other area of methods improvement regards the availability of humanized immunocompromised mice harboring patient-derived xenografts. Combining human tumors in an environment with human immune cells will enable rapid innovation in immuno-oncology therapeutics.

Environmental epitranscriptomics

Chemical modifications of RNA molecules have gained increasing attention since evidence emerged for their substantive roles in a range of biological processes, such as the stability and translation of mRNA transcripts. More than 150 modifications have been identified in different organisms to date, collectively known as the 'epitranscriptome', with 6-methyladenosine (m⁶A), 5-methylcytidine (m⁵C), pseudouridine and N1-methyladenosine (m¹A) the most extensively investigated. Although we are just beginning to elucidate the roles of these modifications in cellular functions, there is already evidence for their dysregulation in diseases such as cancer and neurodevelopmental disorders. There is currently more limited knowledge regarding how environmental exposures affect the epitranscriptome and how this may mediate disease risk, but evidence is beginning to emerge. Here, we review the current evidence for the impact of environmental exposures such as benzo[a]pyrene, bisphenol A, pesticides, metals and nanoparticles upon RNA modifications and the expression of their 'writers' (methyl transferases), 'erasers' (demethylases) and 'readers'. We discuss future directions of the field and identify areas of particular promise and consider the technical challenges that are faced.

Normal mesothelial cell lines newly derived from human pleural biopsy explants

Mesothelial cells are arranged as a monolayer on covering membranes that invest surfaces of body cavities like the pleura and peritoneum. Primary human mesothelial cell (HMC) cultures are needed for studying mesothelial cell homeostasis and developing disease models, such as wound healing or cancers. Remarkably, there is a paucity of useable HMC lines that are currently available that faithfully recapitulate normal in vivo phenotypic characteristics. Here, we present a strategy to recover HMC from human pleural tissue and to immortalize them for extended in vitro culturing. Human pleural membrane was harvested by minimally invasive surgical techniques. HMC were isolated using a two-step process combining explant cellular outgrowth from biopsy tissue and flow cytometry based on cell surface expression of cadherin-1 and CD71. Cell cultures were generated after lentiviral transfection with human telomerase. The new HMC cultures retain the same phenotypic traits and physiologic features as their in vivo counterparts, yet they can be adapted for short-term or long-term culture in large-scale in vitro experimentation. In particular, we generated a new HMC line harboring a germline mutation in breast cancer type-1-associated protein-1 (BAP1), a causal tumor suppressor gene, that could be instrumental to malignant mesothelioma research. Patient-specific, normal HMC may serve as novel discovery tools allowing more powerful research models of both normal physiology and disease processes. Our surgically driven approach leads to a limitless resource of novel mesothelial cell cultures.

Upregulation of mesothelial genes in ovarian carcinoma cells is associated with an unfavorable clinical outcome and the promotion of cancer cell adhesion

A hallmark of ovarian high‐grade serous carcinoma (HGSC) is its early and massive peritoneal dissemination via the peritoneal fluid. It is generally believed that tumor cells must breach the mesothelium of peritoneal organs to adhere to the underlying extracellular matrix (ECM) and initiate metastatic growth. However, the molecular mechanisms underlying these processes are only partially understood. Here, we have analyzed 52 matched samples of spheroids and solid tumor masses (suspected primary lesions and metastases) from 10 patients by targeted sequencing of 21 loci previously proposed as targets of HGSC driver mutations. This analysis revealed very similar patterns of genetic alterations in all samples. One exception was FAT3 with a strong enrichment of mutations in metastases compared with presumed primary lesions in two cases. FAT3 is a putative tumor suppressor gene that codes for an atypical cadherin, pointing a potential role in peritoneal dissemination in a subgroup of HGSC patients. By contrast, transcriptome data revealed clear and consistent differences between tumor cell spheroids from ascites and metastatic lesions, which were mirrored by the in vitro adherence of ascites‐derived spheroids. The adhesion‐induced transcriptional alterations in metastases and adherent cells resembled epithelial–mesenchymal transition, but surprisingly also included the upregulation of a specific subset of mesothelial genes, such as calretinin (CALB2) and podoplanin (PDPN). Consistent with this finding, calretinin staining was also observed in subsets of tumor cells in HGSC metastases, particularly at the invasive tumor edges. Intriguingly, a high expression of either CALB2 or PDPN was strongly associated with a poor clinical outcome. siRNA‐mediated CALB2 silencing triggered the detachment of adherent HGSC cells in vitro and inhibited the adhesion of detached HGSC cells to collagen type I. Our data suggest that the acquisition of a mesenchymal–mesothelial phenotype contributes to cancer cell adhesion to the ECM of peritoneal organs and HGSC progression.

Health impact of exposure to asbestos in polluted area of Southern Italy

The three main sources of asbestos pollution in the city of Bari, Puglia, the former Fibronit asbestos factory, the Torre Quetta beach, the former Rossani barracks and the history of their reclamation are described. The results of cohort studies on factory workers and case-control studies on asbestos exposure to the resident population and the onset of mesothelioma are also reported. Finally, the data of the regional register of mesothelioma related to residents in the city of Bari and four new cases with environmental exposure due to the former Rossani barracks are presented.

NLRP inflammasome as a key role player in the pathogenesis of environmental toxicants

Exposure to environmental toxicants (ET) results in specific organ damage and auto-immune diseases, mostly mediated by inflammatory responses. The NLRP3 inflammasome has been found to be the major initiator of the associated pathologic inflammation. It has been found that ETs can trigger all the signals required for an NLRP3-mediated response. The exaggerated activation of the NLRP3 inflammasome and its end product IL-1β, is responsible for the pathogenesis caused by many ETs including pesticides, organic pollutants, heavy metals, and crystalline compounds. Therefore, an extensive study of these chemicals and their mechanisms of inflammasome (INF) activation may provide the scientific evidence for possible targeting of this pathway by proposing possible protective agents that have been previously shown to affect INF compartments and its activation. Melatonin and polyunsaturated fatty acids (PUFA) are among the safest and the most studied of these agents, which affect a wide variety of cellular and physiological processes. These molecules have been shown to suppress the NLRP3 inflammasome mostly through the regulation of cellular redox status and the nuclear factor-κB (NF-κB) pathway, rendering them potential promising compounds to overcome ET-mediated organ damage. In the present review, we have made an effort to extensively review the ETs that exert their pathogenesis via the stimulation of inflammation, their precise mechanisms of action and the possible protective agents that could be potentially used to protect against such toxicants.

Inflammatory and oxidative stress biomarkers at protein and molecular levels in workers occupationally exposed to crystalline silica

Workers chronically exposed to respirable crystalline silica (CS) are susceptible to adverse health effects like silicosis and lung cancer. This study aimed to investigate potential early peripheral biomarkers of inflammation and oxidative stress in miners. The subjects enrolled in this study were occupationally unexposed workers (OUW, n = 29) and workers exposed to crystalline silica (WECS), composed by miners, which were divided into two subgroups: workers without silicosis (WECS I, n = 39) and workers diagnosed with silicosis, retired from work (WECS II, n = 42). The following biomarkers were evaluated: gene expression of L-selectin, CXCL2, CXCL8 (IL-8), HO-1, and p53; malondialdehyde (MDA) plasma levels and non-protein thiol levels in erythrocytes. Additionally, protein expression of L-selectin was evaluated to confirm our previous findings. The results demonstrated that gene expression of L-selectin was decreased in the WECS I group when compared to the OUW group (p < 0.05). Regarding gene expression of CXCL2, CXCL8 (IL-8), HO-1, and p53, significant fold change decreases were observed in workers exposed to CS in relation to unexposed workers (p < 0.05). The results of L-selectin protein expression in lymphocyte surface corroborated with our previous findings; thus, significant downregulation in the WECS groups was observed compared to OUW group (p < 0.05). The MDA was negatively associated with the gene expression of CXCL-2, CXCL8 (IL-8), and p53 (p < 0.05). The participants with silicosis (WECS II) presented significant increased non-protein thiol levels in relation to other groups (p < 0.05). Taken together, our findings may contribute to help the knowledge about the complex mechanisms involved in the silicosis pathogenesis and in the risk of lung cancer development in workers chronically exposed to respirable CS.

Genomics and Epigenetics of Malignant Mesothelioma

Malignant mesothelioma is an aggressive and lethal asbestos-related disease. Diagnosis of malignant mesothelioma is particularly challenging and is further complicated by the lack of disease subtype-specific markers. As a result, it is especially difficult to distinguish malignant mesothelioma from benign reactive mesothelial proliferations or reactive fibrosis. Additionally, mesothelioma diagnoses can be confounded by other anatomically related tumors that can invade the pleural or peritoneal cavities, collectively resulting in delayed diagnoses and greatly affecting patient management. High-throughput analyses have uncovered key genomic and epigenomic alterations driving malignant mesothelioma. These molecular features have the potential to better our understanding of malignant mesothelioma biology as well as to improve disease diagnosis and patient prognosis. Genomic approaches have been instrumental in identifying molecular events frequently occurring in mesothelioma. As such, we review the discoveries made using high-throughput technologies, including novel insights obtained from the analysis of the non-coding transcriptome, and the clinical potential of these genetic and epigenetic findings in mesothelioma. Furthermore, we aim to highlight the potential of these technologies in the future clinical applications of the novel molecular features in malignant mesothelioma.

Exosomes from asbestos-exposed cells modulate gene expression in mesothelial cells

Asbestos exposure is a determinate cause of many diseases, such as mesothelioma, fibrosis, and lung cancer, and poses a major human health hazard. At this time, there are no identified biomarkers to demarcate asbestos exposure before the presentation of disease and symptoms, and there is only limited understanding of the underlying biology that governs asbestos-induced disease. In our study, we used exosomes, 30-140 nm extracellular vesicles, to gain insight into these knowledge gaps. As inhaled asbestos is first encountered by lung epithelial cells and macrophages, we hypothesize that asbestos-exposed cells secrete exosomes with signature proteomic cargo that can alter the gene expression of mesothelial cells, contributing to disease outcomes like mesothelioma. In the present study using lung epithelial cells (BEAS2B) and macrophages (THP-1), we first show that asbestos exposure causes changes in abundance of some proteins in the exosomes secreted from these cells. Furthermore, exposure of human mesothelial cells (HPM3) to these exosomes resulted in gene expression changes related to epithelial-to-mesenchymal transition and other cancer-related genes. This is the first report to indicate that asbestos-exposed cells secrete exosomes with differentially abundant proteins and that those exosomes have a gene-altering effect on mesothelial cells.-Munson, P., Lam, Y.-W., Dragon, J. MacPherson, M., Shukla, A. Exosomes from asbestos-exposed cells modulate gene expression in mesothelial cells.

In vitro experimental models of mesothelioma revisited

Malignant pleural mesothelioma (MPM) is a biologically unusual, highly aggressive cancer that defies current multimodality treatments. Epidemiologic data suggest that this malignancy has not abated despite increasingly strict environmental regulations on asbestos, the putative causative agent for sporadic cases. An incomplete understanding of all the factors mechanistically driving mesothelioma is largely responsible for the current lack of curative treatments. Many approaches have been employed to ascertain the step-by-step molecular events involved in mesothelioma oncogenesis including in vitro, small animal in vivo, and human experimental models; though clearly defined, druggable mechanisms still are elusive. Importantly, the foundation of the latest accepted model of tumor initiation is derived from in vitro systems. A thorough review of in vitro mesothelioma oncogenesis models may suggest further opportunities for discovery.

Profiling of the silica-induced molecular events in lung epithelial cells using the RNA-Seq approach

Silicosis is a prolonged, irreversible and incurable occupational disease, and there is a significant number of newly diagnosed cases every year in Hong Kong. Due to the long latency of the disease, the diagnosis can be missed until detailed clinical examination at a later stage. For a better control of this deadly disease, detailing the pro-inflammatory and fibrotic events in the macrophage would be instrumental in understanding the pathogenesis of the disease and essential for the significant biomarkers discovery. In this in vitro study, human cell line model A549 lung epithelial cells were used. The immediate molecular events underneath the activation of quartz silica polymorphs were followed in a time course of 0, 0.5, 2, 8, 16 and 24 h. The transcriptome library was prepared and subjected to RNA-Seq analysis. Data analysis was performed by pathway analysis tools and verified by real-time PCR. The results showed that triggered genes were mainly found in the immune response and inflammatory pathways. An interesting finding was the association of the DNA-binding protein inhibitor (ID) family in the silica exposure to lung cells. The linkage of ID1, ID2 and ID3 to cancer may rationalize themselves to be the markers indicating an early response of silicosis. However, further studies are required to consolidate the roles of these genes in silicosis. Copyright © 2017 John Wiley & Sons, Ltd.

Asbestos-Induced Mesothelial to Fibroblastic Transition Is Modulated by the Inflammasome

Despite the causal relationship established between malignant mesothelioma (MM) and asbestos exposure, the exact mechanism by which asbestos induces this neoplasm and other asbestos-related diseases is still not well understood. MM is characterized by chronic inflammation, which is believed to play an intrinsic role in the origin of this disease. We recently found that asbestos activates the nod-like receptor family member containing a pyrin domain 3 (NLRP3) inflammasome in a protracted manner, leading to an up-regulation of IL-1β and IL-18 production in human mesothelial cells. Combined with biopersistence of asbestos fibers, we hypothesize that this creates an environment of chronic IL-1β signaling in human mesothelial cells, which may promote mesothelial to fibroblastic transition (MFT) in an NLRP3-dependent manner. Using a series of experiments, we found that asbestos induces a fibroblastic transition of mesothelial cells with a gain of mesenchymal markers (vimentin and N-cadherin), whereas epithelial markers, such as E-cadherin, are down-regulated. Use of siRNA against NLRP3, recombinant IL-1β, and IL-1 receptor antagonist confirmed the role of NLRP3 inflammasome-dependent IL-1β in the process. In vivo studies using wild-type and various inflammasome component knockout mice also revealed the process of asbestos-induced mesothelial to fibroblastic transition and its amelioration in caspase-1 knockout mice. Taken together, our data are the first to suggest that asbestos induces mesothelial to fibroblastic transition in an inflammasome-dependent manner.

The NLRP3 inflammasome in pathogenic particle and fibre-associated lung inflammation and diseases

The concept of the inflammasome, a macromolecular complex sensing cell stress or danger signals and initiating inflammation, was first introduced approximately a decade ago. Priming and activation of these intracellular protein platforms trigger the maturation of pro-inflammatory chemokines and cytokines, most notably, interleukin-1β (IL-1β) and IL-18, to promulgate innate immune defenses. Although classically studied in models of gout, Type II diabetes, Alzheimer's disease, and multiple sclerosis, the importance and mechanisms of action of inflammasome priming and activation have recently been elucidated in cells of the respiratory tract where they modulate the responses to a number of inhaled pathogenic particles and fibres. Most notably, inflammasome activation appears to regulate the balance between tissue repair and inflammation after inhalation of pathogenic pollutants such as asbestos, crystalline silica (CS), and airborne particulate matter (PM). Different types of fibres and particles may have distinct mechanisms of inflammasome interaction and outcome. This review summarizes the structure and function of inflammasomes, the interplay between various chemokines and cytokines and cell types of the lung and pleura after inflammasome activation, and the events leading to the development of non-malignant (allergic airway disease and chronic obstructive pulmonary disease (COPD), asbestosis, silicosis) and malignant (mesothelioma, lung cancer) diseases by pathogenic particulates. In addition, it emphasizes the importance of communication between cells of the immune system, target cells of these diseases, and components of the extracellular matrix (ECM) in regulation of inflammasome-mediated events.

KAT5 (Tip60) is a potential therapeutic target in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare aggressive cancer of the pleura. Asbestos exposure (through inhalation) is the most well established risk factor for mesothelioma. The current standard of care for patients suffering from MPM is a combination of cisplatin and pemetrexed (or alternatively cisplatin and raltitrexed). Most patients, however, die within 24 months of diagnosis. New therapies are therefore urgently required for this disease. Lysine acetyltransferases (KATs) including KAT5 have been linked with the development of cisplatin resistance. This gene may therefore be altered in MPM and could represent a novel candidate target for intervention. Using RT-PCR screening the expression of all known KAT5 variants was found to be markedly increased in malignant tumors compared to benign pleura. When separated according to histological subtype, KAT5 was significantly overexpressed in both the sarcomatoid and biphasic subgroups for all transcript variants. A panel of MPM cell lines including the normal pleural cells LP9 and Met5A was screened for expression of KAT5 variants. Treatment of cells with a small molecule inhibitor of KAT5 (MG-149) caused significant inhibition of cellular proliferation (p<0.0001), induction of apoptosis and was accompanied by significant induction of pro-inflammatory cytokines/chemokines.