Context .- The separation of benign from malignant mesothelial proliferations is crucial to patient care but is frequently morphologically difficult. Objective .- To briefly review adjunctive tests claimed to be useful in this setting and to examine in detail 2 new tests: p16 fluorescence in situ hybridization (FISH) and BRCA1-associated protein 1 (BAP1) immunohistochemistry. Design .- Literature review with emphasis on p16 FISH and BAP1 immunohistochemistry. Results .- Glucose transporter-1, p53, insulin-like growth factor 2 messenger RNA-binding protein 3 (IMP-3), desmin, and epithelial membrane antigen have all been claimed to mark either benign or malignant mesothelial processes, but in practice they at best provide statistical differences in large series of cases, without being useful in an individual case. Homozygous deletion of p16 by FISH or loss of BAP1 has only been reported in malignant mesotheliomas and not in benign mesothelial proliferations. BAP1 appears to be lost more frequently in epithelial than mixed or sarcomatous mesotheliomas. Homozygous deletion of p16 by FISH is seen in pleural epithelial, mixed, and sarcomatous mesotheliomas, but it is much less frequent in peritoneal mesothelioma. The major drawback to both these tests is limited sensitivity; moreover, failure to find p16 deletion or BAP1 loss does not make a mesothelial process benign. Conclusions .- In the context of a mesothelial proliferation, the finding of homozygous deletion of p16 by FISH or loss of BAP1 by immunohistochemistry is, thus far, 100% specific for malignant mesothelioma. The limited sensitivity of each test may be improved to some extent by running both tests.
Malignant mesothelioma (MM) is an aggressive malignancy of the pleura and other serosal membranes originating from mesothelial cells that, despite decades of research, continues to have limited therapeutic options and is associated with a poor prognosis. Areas covered: MMs induce a strong inflammatory response that is also associated with neoangiogenesis and activation of proangiogenic factors. Given this, several anti-angiogenic agents have been trialled in a variety of malignancies including mesothelioma. Herein we summarise the role of angiogenesis in MM and the current available data targeting these pathways. Expert commentary: The addition of bevacizumab to cisplatin/pemetrexed chemotherapy is currently a therapeutic option with a proven 2.7 month overall survival benefit in fit patients less than 75. Other antiangiogenics such as nintedinib show early promise, although the Phase III trial results are eagerly awaited before this therapy enters treatment paradigms. Beyond this, it is likely that combinations of antiangiogenics with immunotherapies will be investigated in future studies.
Diffuse malignant peritoneal mesothelioma (MPeM) is rare and arises from peritoneal serosal surfaces. Although it shares similar histomorphology with its counterpart, malignant pleural mesothelioma, etiologies, clinical courses, and therapies differ. Nuclear grading and level of mitoses have been correlated with prognosis in malignant pleural mesothelioma with epithelioid subtype. Whether nuclear grading and level of mitoses correlate with prognosis in MPeM is still unknown. Our study utilizes a 2 tier system incorporating nuclear features and level of the mitoses to stratify cases of MPeM with epithelioid subtype. Fifty-one cases of MPeM with clinical follow-up underwent retrospective microscopic review. From that subset, 46 cases were of epithelioid subtype, which were then stratified into a low-grade or high-grade tier. Survival times were calculated on the basis of Kaplan-Meier analysis. The low-grade tier had higher overall survival with a median of 11.9 years and 57% at 5 years when compared with the high-grade tier with a median of 3.3 years and 21% at 5 years (P=0.002). Although not statistically significant, the low-grade tier had higher progression-free survival with a median of 4.7 years and 65% at 5 years when compared with the high-grade tier with a median of 1.9 years and 35% at 5 years (P=0.089). Our study is first to specifically evaluate and correlate nuclear features and level of mitoses with overall survival in MPeM with epithelioid subtype.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially. http://creativecommons.org/licenses/by-nc-nd/4.0/.
Chronic exposure to intraperitoneal asbestos triggered a marked response in the mesothelium well before tumor development. Macrophages, mesothelial precursor cells, cytokines, and growth factors accumulated in the peritoneal lavage. Transcriptome profiling revealed YAP/TAZ activation in inflamed mesothelium with further activation in tumors, paralleled by increased levels of cells with nuclear YAP/TAZ. Arg1 was one of the highest upregulated genes in inflamed tissue and tumor. Inflamed tissue showed increased levels of single-nucleotide variations, with an RNA-editing signature, which were even higher in the tumor samples. Subcutaneous injection of asbestos-treated, but tumor-free mice with syngeneic mesothelioma tumor cells resulted in a significantly higher incidence of tumor growth when compared to naïve mice supporting the role of the environment in tumor progression.
Malignant Pleural Mesothelioma (MPM) is an aggressive tumor arising from mesothelial cells lining the pleural cavities characterized by resistance to standard therapies. Most of the molecular steps responsible for pleural transformation remain unclear; however, several growth factor signaling cascades are known to be altered during MPM onset and progression. Transducers of these pathways, such as PIK3CA-mTOR-AKT, MAPK, and ezrin/radixin/moesin (ERM) could therefore be exploited as possible targets for pharmacological intervention. This study aimed to identify ‘druggable’ pathways in MPM and to formulate a targeted approach based on the use of commercially available molecules, such as the multikinase inhibitor sorafenib and the mTOR inhibitor everolimus.
The hypothesis that most cancers are of monoclonal origin is often accepted as a fact in the scientific community. This dogma arose decades ago, primarily from the study of hematopoietic malignancies and sarcomas, which originate as monoclonal tumors. The possible clonal origin of malignant mesothelioma (MM) has not been investigated. Asbestos inhalation induces a chronic inflammatory response at sites of fiber deposition that may lead to malignant transformation after 30-50 years latency. As many mesothelial cells are simultaneously exposed to asbestos fibers and to asbestos-induced inflammation, it may be possible that more than one cell undergoes malignant transformation during the process that gives rise to MM, and result in a polyclonal malignancy.
Malignant pleural mesothelioma is a highly aggressive tumour associated with asbestos exposure. There are few effective treatment options for mesothelioma and patients have a very poor prognosis with a median survival of less than 12 months from diagnosis. Biomarkers have been proposed as a cost-effective means of cancer management and the search for a mesothelioma biomarker has been on-going for the past thirty years. Many traditional soluble (glyco)-protein biomarkers have been evaluated over this time and an ever increasing list of new biomarkers, including mRNA, DNA, miRNA and antibodies, are being reported from biomarker discovery projects. To date, soluble mesothelin is the only tumour biomarker to receive FDA approval for clinical use in mesothelioma. Mesothelin is a glycoprotein normally expressed on the surface of mesothelial cells, and in the cancerous state can be present in the circulation. Mesothelin has a limited expression on normal, non-malignant tissue and is thus an attractive therapeutic target for mesothelin-positive tumours. In this review we will focus on the discovery and clinical usages of mesothelin and provide an update on other mesothelioma biomarkers and show how such biomarker studies might impact on the management of this deadly tumour in the future.
In response to cardiac damage, a mesothelial tissue layer enveloping the heart called the epicardium is activated to proliferate and accumulate at the injury site. Recent studies have implicated the epicardium in multiple aspects of cardiac repair: as a source of paracrine signals for cardiomyocyte survival or proliferation; a supply of perivascular cells and possibly other cell types such as cardiomyocytes; and as a mediator of inflammation. However, the biology and dynamism of the adult epicardium is poorly understood. To investigate this, we created a transgenic line to ablate the epicardial cell population in adult zebrafish. Here we find that genetic depletion of the epicardium after myocardial loss inhibits cardiomyocyte proliferation and delays muscle regeneration. The epicardium vigorously regenerates after its ablation, through proliferation and migration of spared epicardial cells as a sheet to cover the exposed ventricular surface in a wave from the chamber base towards its apex. By reconstituting epicardial regeneration ex vivo, we show that extirpation of the bulbous arteriosus-a distinct, smooth-muscle-rich tissue structure that distributes outflow from the ventricle-prevents epicardial regeneration. Conversely, experimental repositioning of the bulbous arteriosus by tissue recombination initiates epicardial regeneration and can govern its direction. Hedgehog (Hh) ligand is expressed in the bulbous arteriosus, and treatment with a Hh signalling antagonist arrests epicardial regeneration and blunts the epicardial response to muscle injury. Transplantation of Sonic hedgehog (Shh)-soaked beads at the ventricular base stimulates epicardial regeneration after bulbous arteriosus removal, indicating that Hh signalling can substitute for the influence of the outflow tract. Thus, the ventricular epicardium has pronounced regenerative capacity, regulated by the neighbouring cardiac outflow tract and Hh signalling. These findings extend our understanding of tissue interactions during regeneration and have implications for mobilizing epicardial cells for therapeutic heart repair.
BACKGROUNDEndometriosis affects 6-10% of women of reproductive age and is associated with chronic pelvic pain, dysmenorrhoea, dyspareunia and infertility. Endometriosis is defined by the presence of endometrial tissue outside the uterus, most commonly attached to the pelvic peritoneum. The endometrium in women with endometriosis is reported to be altered and there is increasing evidence that the phenotype of the pelvic peritoneum may also play a role in the establishment and maintenance of the disease. The aim of this review is to discuss the putative role of the pelvic peritoneum in the pathophysiology of peritoneal endometriosis.METHODSA review was undertaken of the published literature on (i) the anatomy and physiology of the peritoneum and (ii) the potential roles played by peritoneal cells in the establishment and maintenance of peritoneal endometriosis. The current understanding of the biology of peritoneal endometriosis is summarized and the potential interaction of the peritoneum with ectopic endometrial cells in endometriosis is highlighted.RESULTSSeveral studies indicate that differential expression of peritoneal mesothelial adhesion factors occurs in women with endometriosis, providing potential ectopic endometrial cell attachment sites for the establishment of endometriosis lesions. Changes in the peritoneal mesothelial cell phenotype, including loss of tight junctions, may allow ectopic cells to bind to, or early lesions to invade into, the extracellular matrix. Epithelial-to-mesenchymal transition of peritoneal mesothelial cells may also lead to an increase in lesion invasion and formation of fibrotic tissue in and around the lesion. There is evidence that the peritoneal mesothelium may also play a role in the invasion potential of ectopic cells by production of MMPs increasing local tissue remodelling. Peritoneal immune scavenging function may be lowered in women with endometriosis; for example there is a notable increase in macrophage-derived secretion products in women with endometriosis associated with increases in cell proliferation, cell adhesion and neovascularization.CONCLUSIONSThe pelvic peritoneum appears to play a key role in the development and maintenance of endometriosis.
Peritoneal mesothelial cysts (PMC) are a clinical dilemma because of their true pathogenic nature. Many definitions have been associated with PMC, including “benign multicystic mesothelioma”, “cystic mesothelioma”, “multilocular peritoneal inclusion cysts”, “inflammatory cysts of the peritoneum” or “postoperative peritoneal cyst”.