BAP1 mutation is a frequent somatic event in peritoneal malignant mesothelioma

Molecular and Genetic Markers of Peritoneal Metastasis

Peritoneal surface malignancies (PSMs) represent a biologically diverse group of cancers that range from primary peritoneal mesothelioma to metastatic gastrointestinal cancers. Because of the heterogenous nature of PSM, there is a large gap in molecular characterization of these cancers. This article reviews the underlying molecular and genetic mechanisms for PSM.

Systemic Therapy and Surgical Management of Peritoneal Mesothelioma

Malignant peritoneal mesothelioma is an aggressive and rare disease that affects the serosal membranes. The outcomes of patients who suffer from this disease have improved because of the advances in imaging, genetics, and treatment strategies such as systemic therapy and cytoreduction surgery and hyperthermic intraperitoneal chemotherapy. Multidisciplinary care remains essential for enhancing survival and quality of life.

Peritoneal Carcinomatosis: When Everything Is Not What It Seems

Malignant peritoneal mesothelioma (MPM) is a rare neoplasm with a low incidence rate worldwide but high morbidity and mortality rates. Due to its rarity, the studies are scarce. We present a case of a 73-year-old woman admitted to the internal medicine unit with constitutional syndrome, abdominal pain, and ascites. Throughout the investigation, aspects suggestive of peritoneal carcinomatosis were identified. An extensive study was then carried out in an attempt to identify the primary tumor, which proved to be unsuccessful. During the two weeks of hospitalization, the patient's clinical condition worsened, with an increase in ascites and a deterioration in her general health. This case was then discussed with an oncology consultant, and it was decided to biopsy a peritoneal implant with the support of interventional radiology. MPM was then diagnosed through histopathology. With this case, the authors intend to highlight that, although rare, this diagnosis should be considered when appropriate and that even in the suspicion of secondary disease, the primary tumor should always be identified, as localized MPM may be curable.

Molecular alterations and potential actionable mutations in peritoneal mesothelioma: a scoping review of high-throughput sequencing studies

BACKGROUND

Peritoneal mesothelioma (PeM) is a rare malignancy with a poor prognosis. Currently there is a lack of effective systemic therapies. Due to the rarity of PeM, it is challenging to study new treatment options. Off-label use of targeted drugs could be an effective approach. This scoping review aims to explore the genomic landscape of PeM to identify potential therapeutic targets.

MATERIALS AND METHODS

A systematic literature search of Embase, Medline, Web of Science, the Cochrane Library, and Google Scholar was carried out up to 1 November 2022. Studies that reported on molecular alterations in PeM detected by high-throughput sequencing techniques were included. Genes that were altered in ≥1% of PeMs were selected for the identification of potential targeted therapies.

RESULTS

Thirteen articles were included, comprising 824 PeM patients. In total, 142 genes were altered in ≥1% of patients, of which 7 genes were altered in ≥10%. BAP1 was the most commonly altered gene (50%). Other commonly altered genes were NF2 (25%), CDKN2A (23%), CDKN2B (17%), PBRM1 (15%), TP53 (14%), and SETD2 (13%). In total, 17% of PeM patients were carriers of a germline mutation, mainly in BAP1 (7%).

CONCLUSIONS

This scoping review provides an overview of the mutational landscape of PeM. Germline mutations might be a larger contributor to the incidence of PeM than previously thought. Currently available targeted therapy options are limited, but several targeted agents [such as poly (ADP-ribose) polymerase (PARP), enhancer of zeste homolog 2 (EZH2), and cyclin-dependent kinase 4/6 (CDK4/6) inhibitors] were identified that might provide new targeted therapy options in the future.

GC-MS-based untargeted metabolic profiling of malignant mesothelioma plasma

Background

Malignant mesothelioma (MM) is a cancer caused mainly by asbestos exposure, and is aggressive and incurable. This study aimed to identify differential metabolites and metabolic pathways involved in the pathogenesis and diagnosis of malignant mesothelioma.

Methods

By using gas chromatography-mass spectrometry (GC-MS), this study examined the plasma metabolic profile of human malignant mesothelioma. We performed univariate and multivariate analyses and pathway analyses to identify differential metabolites, enriched metabolism pathways, and potential metabolic targets. The area under the receiver-operating curve (AUC) criterion was used to identify possible plasma biomarkers.

Results

Using samples from MM (n = 19) and healthy control (n = 22) participants, 20 metabolites were annotated. Seven metabolic pathways were disrupted, involving alanine, aspartate, and glutamate metabolism; glyoxylate and dicarboxylate metabolism; arginine and proline metabolism; butanoate and histidine metabolism; beta-alanine metabolism; and pentose phosphate metabolic pathway. The AUC was used to identify potential plasma biomarkers. Using a threshold of AUC = 0.9, five metabolites were identified, including xanthurenic acid, (s)-3,4-hydroxybutyric acid, D-arabinose, gluconic acid, and beta-d-glucopyranuronic acid.

Conclusions

To the best of our knowledge, this is the first report of a plasma metabolomics analysis using GC-MS analyses of Asian MM patients. Our identification of these metabolic abnormalities is critical for identifying plasma biomarkers in patients with MM. However, additional research using a larger population is needed to validate our findings.

NR4A3 fusions characterize a distinctive peritoneal mesothelial neoplasm of uncertain biological potential with pure adenomatoid/microcystic morphology

A focal adenomatoid-microcystic pattern is not uncommon in peritoneal mesothelioma, but tumors composed almost exclusively of this pattern are distinctly rare and have not been well characterized. A small subset of mesotheliomas (mostly in children and young adults) are characterized by gene fusions including EWSR1/FUS::ATF1, EWSR1::YY1, and NTRK and ALK rearrangements, and often have epithelioid morphology. Herein, we describe five peritoneal mesothelial neoplasms (identified via molecular screening of seven histologically similar tumors) that are pure adenomatoid/microcystic in morphology and unified by the presence of an NR4A3 fusion. Patients were three males and two females aged 31-70 years (median, 40 years). Three presented with multifocal/diffuse and two with a localized disease. The size of the individual lesions ranged from 1.5 to 8 cm (median, 4.7). The unifocal lesions originated in the small bowel mesentery and the mesosigmoid. Treatment included surgery, either alone (three) or combined with hyperthermic intraperitoneal chemotherapy (two), and neoadjuvant or adjuvant chemotherapy (one case each). At the last follow-up (6-13 months), all five patients were alive and disease-free. All tumors were morphologically similar, characterized by extensive sieve-like microcystic growth with bland-looking flattened cells lining variably sized microcystic spaces and lacked a conventional epithelioid or sarcomatoid component. Immunohistochemistry confirmed mesothelial differentiation, but most cases showed limited expression of D2-40 and calretinin. Targeted RNA sequencing revealed an NR4A3 fusion (fusion partners were EWSR1 in three cases and CITED2 and NIPBL in one case each). The nosology and behavior of this morphomolecularly defined novel peritoneal mesothelial neoplasm of uncertain biological potential and its distinction from adenomatoid variants of conventional mesothelioma merit further delineation as more cases become recognized.

Second Primary Cancers in a Population-Based Mesothelioma Registry

Background: The presence of a second primary cancer (SPC) in patients with pleural mesothelioma (PM) may impact overall survival and suggest a common mechanism of carcinogenesis or an underlying germline genetic alteration. Methods: We evaluated the occurrence of SPCs within PM cases collected from 2000 to 2018 by the Lombardy Mesothelioma Registry and their prognostic implications. Kaplan–Meier analysis was performed to estimate median survival times, together with univariate and multivariate Cox regression models to estimate hazard ratios (HR) and 95% confidence intervals (CI) of death. Results: The median overall survival (OS) of the entire study population (N = 6646) was 10.9 months (95% CI: 10.4–11.2); patient age and histotype were the strongest prognostic factors. No substantial survival difference was observed by the presence of an SPC (10.5 months in 1000 patients with an SPC vs. 10.9 months in 5646 patients in the non-SPC group, HR 1.03, p = 0.40). Shorter OS in the SPC group was only observed in 150 patients with the non-epithelioid subtype (median OS of 5.4 vs. 7.1 months, HR 1.21, p = 0.03). Conclusions: The diagnosis of an SPC did not influence the outcome of PM patients in the overall study population but was associated with shorter OS in non-epithelioid cases. Further studies are needed to clarify the role of SPCs as markers of genetic susceptibility in mesothelioma.

EWSR1::YY1 fusion positive peritoneal epithelioid mesothelioma harbors mesothelioma epigenetic signature: Report of 3 cases in support of an emerging entity

Mesothelioma is a rare, aggressive malignant neoplasm of mesothelial origin. A small subset of peritoneal mesothelioma is driven by recurrent gene fusions, mostly EWSR1/FUS::ATF1 fusions, with predilection for young adults. To date, only two cases of mesothelioma harboring EWSR1::YY1 fusions have been described. We present three additional cases of EWSR1::YY1-fused peritoneal mesotheliomas, two localized and one diffuse, all occurring in the peritoneum of middle-aged adults (2 females and 1 male), and discovered incidentally by imaging or during surgery performed for unrelated reasons. None presented with symptoms or had a known history of asbestos exposure. All three cases were cellular epithelioid neoplasms with heterogeneous architectural patterns comprising mostly solid nests and sheets with variably papillary and trabecular areas against collagenous stroma. Cytologically, the cells were monomorphic, polygonal, epithelioid cells with dense eosinophilic cytoplasm and centrally located nuclei. Overt mitotic activity or tumor necrosis was absent. All cases showed strong diffuse immunoreactivity for pancytokeratin, CK7, and nuclear WT1, patchy to negative calretinin, retained BAP1 expression, and were negative for Ber-EP4 and MOC31. RNA-sequencing confirmed in-frame gene fusion transcripts involving EWSR1 exon 7/8 and YY1 exon 2/3. By unsupervised clustering analysis, the methylation profiles of EWSR1::YY1-fused mesotheliomas clustered similarly with EWSR1/FUS::ATF1-fused mesotheliomas and conventional mesotheliomas, suggesting a mesothelioma epigenetic signature. All three patients underwent surgical resection or cytoreductive surgery of the masses. On follow-up imaging, no recurrence or progression of disease was identified. Our findings suggest that EWSR1::YY1-fusion defines a small subset of peritoneal epithelioid mesothelioma in middle-aged adults without history of asbestos exposure.

Advances in the management of peritoneal malignancies

Peritoneal surface malignancies (PSMs) are usually associated with a poor prognosis. Nonetheless, in line with advances in the management of most abdominopelvic metastatic diseases, considerable progress has been made over the past decade. An improved understanding of disease biology has led to the more accurate prediction of neoplasia aggressiveness and the treatment response and has been reflected in the proposal of new classification systems. Achieving complete cytoreductive surgery remains the cornerstone of curative-intent treatment of PSMs. Alongside centralization in expert centres, enabling the delivery of multimodal and multidisciplinary strategies, preoperative management is a crucial step in order to select patients who are most likely to benefit from surgery. Depending on the specific PSM, the role of intraperitoneal chemotherapy and of perioperative systemic chemotherapy, in particular, in the neoadjuvant setting, is established in certain scenarios but questioned in several others, although more prospective data are required. In this Review, we describe advances in all aspects of the management of PSMs including disease biology, assessment and improvement of disease resectability, perioperative management, systemic therapy and pre-emptive management, and we speculate on future research directions.

Peritoneal Pathology Review: Mullerian, Mucinous and Mesothelial Lesions

This review provides an overview of the pathology of selected benign and malignant lesions of the female peritoneum and their often-encountered differential diagnoses. It includes endometriosis and its related lesions, endosalpingiosis, pseudomyxoma peritonei (PMP) and related ovarian/appendiceal pathology, and malignant and benign mesothelial tumors. The current terminology associated with PMP is also discussed.

Molecular Pathways in Peritoneal Mesothelioma: A Minireview of New Insights

Mesothelioma is a rare malignant neoplasm with poor survival. It mainly affects the pleura (90%) but can arise in all serous cavities: peritoneum (5-10%), pericardium and tunica vaginalis testis (<1%). The onset of pleural mesothelioma is strictly related to asbestos exposure with a long latency time. The causal link with asbestos has also been suggested for peritoneal mesothelioma, while the importance of exposure in the onset of pericardial and tunica vaginalis testis mesotheliomas is not well known. Mesothelioma remains an aggressive and fatal disease with a five-year mortality rate higher than 95%. However, new therapeutic approaches based on molecular-targeted and immunomodulatory therapies are being explored but have conflicting results. In this context, the identification of critical targets appears mandatory. Awareness of the molecular and physiological changes leading to the neoplastic degeneration of mesothelial cells and the identification of gene mutations, epigenetic alterations, gene expression profiles and altered pathways could be helpful for selecting targetable mechanisms and molecules. In this review, we aimed to report recent research in the last 20 years focusing on the molecular pathways and prognostic factors in peritoneal mesothelioma and their possible diagnostic and therapeutic implications.

Pediatric Peritoneal Epithelial Malignant Mesothelioma Case Report

We present a 14-year-old boy with peritoneal epithelial malignant mesothelioma (PEMM). While pathology is required to make this diagnosis, radiology plays a crucial role throughout the clinical course of this disease. The key imaging characteristics of peritoneal mesothelioma have been previously well-described in the adult population, but there are rare reports in the pediatric population. This pediatric report highlights the multidimensional use of imaging in this disease, from the initial evaluation to therapeutic supplementation and subsequent follow-up.

BRCA-associated protein 1 (BAP1) and miR-31 combination predicts outcomes in epithelioid malignant pleural mesothelioma

BACKGROUND

Malignant pleural mesothelioma (MPM) is an aggressive disease, with few available treatment options. Identification of novel prognostic and predictive biomarkers is a priority. In MPM patients, BRCA-associated protein 1 (BAP1) alterations are detected in about 60% of cases and miR-31 seems to be involved in BAP1 regulation at post-transcriptional level. The aim of this study was to evaluate the interaction between BAP1 and miR-31 in MPM and their prognostic role in MPM.

METHODS

The expression of BAP1 and miR-31 was analyzed in tissues of 55 MPM patients treated with first-line chemotherapy. Overall survival (OS) and progression-free survival (PFS) were assessed by Kaplan-Meier method and Log-rank test was used to investigate differences among subgroups. Multivariate Cox regression analysis was used to evaluate independent predictors of survival.

RESULTS

In the whole cohort, loss of BAP1 was associated with a significant improvement in OS, but not in PFS. Lower miR-31 levels were detected in epithelioid MPM (e-MPM) compared to the non-epithelioid subtypes and resulted associated with BAP1 loss. By looking at the e-MPM subgroup, loss of BAP1 was not able to predict clinical outcome. Conversely, miR-31 levels were significantly associated with PFS (P=0.028), but not with OS (P=0.059). By combining the two biomarkers, e-MPM patients with BAP1 loss/low miR-31 levels showed a better prognosis compared to the ones with BAP1 retained/high miR-31 levels (median OS 22.6 vs. 17.0 months, P=0.017 and median PFS 8.7 vs. 5.1 months, P=0.020). The BAP1 and miR-31 combination was confirmed at multivariate analysis as an independent prognostic factor for e-MPM patients.

CONCLUSIONS

In this preliminary study, we found that the prognostic stratification of e-MPM patients may be improved by simultaneously assessing of BAP1 status and miR-31 levels. The two-biomarker score is useful to identify a subgroup of e-MPM tumors characterized by BAP1 retained and high miR-31 levels with worse clinical outcome.

Meningioma: A Pathology Perspective

Meningiomas are dural-based neoplasms that account for ∼37% of all intracranial tumors in the adult population. They can occur anywhere within the central nervous system and have a predilection for females. The World Health Organization classifies meningiomas into 3 grades based on increased risk of recurrence and associated mortality in grade III tumors. Although most tumors are categorized as low-grade, up to ∼15%-20% demonstrate more aggressive behavior. With the long-recognized association with neurofibromatosis type 2 gene mutation, putative driver mutations can be attributed to ∼80% of tumors. Several germline mutations have also been identified in some cases of familial meningiomatosis such as SMARCE1, SUFU, PTEN, and BAP1. Finally, in addition to genetic data, epigenetic alterations, specifically deoxyribonucleic acid methylation, are being increasingly recognized for their prognostic value, potentially adding objectivity to a currently subjective grading scheme.

Microsimulation Model for Evaluating the Cost-Effectiveness of Surveillance in BAP1 Pathogenic Variant Carriers

PURPOSE

Pathogenic BAP1 germline variants cause a tumor-predisposition syndrome (BAP1-TPDS) linked to uveal melanoma, mesothelioma, cutaneous melanoma, and renal cell carcinoma. Surveillance of carriers of pathogenic BAP1 variants provides an opportunity for early tumor detection; however, there are no evidence-based guidelines for management of BAP1-TPDS, nor health economic evaluation; this study aims to provide this evidence.

METHODS

We created a Markov microsimulation health state transition model of BAP1 germline carriers to predict if active surveillance for the four main tumors influences survival and improves associated economic costs with a time horizon of 100 years from the perspective of the healthcare system (N = 10,000). Model inputs were derived from data published by the BAP1 Interest Group Consortium and other studies. Management and healthcare costs were extracted from Australian costing schedules (final figures converted to US dollars [USD]), and outcomes compared for individuals receiving surveillance with those in a nonsurveillance arm. Robustness was evaluated on 10,000 iterations of a 100-sample random sampling of the model output.

RESULTS

On average, surveillance of BAP1 carriers increased survival by 4.9 years at an additional cost of $6,197 USD for the healthcare system including surveillance costs ($1,265 USD per life year gained). The nonsurveillance arm had more diagnosed late tumors (62.8% v 10.7%) and a higher rate of BAP1-related deaths (50.2% v 35.4%; a 29.5% increase). The model was cost-effective under all sensitivity analyses. Our secondary robustness analysis estimated that 99.86% of 100-sample iterations were cost-effective and 19.67% of these were cost-saving.

CONCLUSION

It is recommended that carriers of BAP1 germline variants are identified and undertake active surveillance, as this model suggests that this could improve survival and be cost-effective for the healthcare system.

The Role of Hyperthermic Intraperitoneal Chemotherapy for Non-colorectal Peritoneal Surface Malignancies

BACKGROUND

Peritoneal carcinomatosis, from a variety of gastrointestinal and gynecological malignancies, has been historically challenging to treat and there remains a wide range of biologic aggressiveness in these patients. Malignancies commonly associated with PC include those of colorectal, appendiceal, gastric, ovarian, sarcoma, small intestinal, and primary peritoneal origin among others. Advances in our understanding of this unique disease process have led to significant interest in cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) as an emerging treatment option. The goal of CRS-HIPEC is to remove all visible macroscopic disease while preserving organ function, and then treat microscopic disease through perfusion of the peritoneal cavity with heated chemotherapy.

PURPOSE

Although recent reviews have focused on the management of peritoneal carcinomatosis secondary to colorectal cancer given the publication of several recent randomized controlled trials, the purpose of the current review is to summarize the evidence on CRS-HIPEC for non-colorectal peritoneal surface malignancies, including appendiceal neoplasms, malignant peritoneal mesothelioma, gastric cancer, and ovarian cancer.

RESULTS

While retrospective studies have clarified the importance of prognostic factors such as the peritoneal carcinomatosis index, completeness of cytoreduction, histopathological characteristics, and lymph node positivity, the lack of convincing level 1 evidence for the use of CRS-HIPEC has led to it remaining a highly controversial topic.

CONCLUSION

The decision to utilize CRS-HIPEC should involve a multidisciplinary team approach and evaluation of prognostic factors to balance the short-term morbidity of the operation with maximum long-term benefits. Large, multi-institutional groups and ongoing trials hold promise for clarifying the role of CRS-HIPEC in peritoneal surface malignancies.

Apatinib Mesylate Inhibits the Proliferation and Metastasis of Epithelioid Malignant Peritoneal Mesothelioma In Vitro and In Vivo

Objective

Malignant peritoneal mesothelioma (MPM) is a rare malignancy with few effective molecular therapies. In this study, we evaluated the anti-tumor activity and safety of apatinib, a vascular endothelial growth factor receptor 2 inhibitor, in MPM in vitro and in vivo.

Methods

We established several patient-derived xenograft (PDX) models and primary cell lines of MPM. The cell lines were used to study the effects of apatinib on proliferation, cell cycle, migration, and apoptosis by CCK8, flow cytometry, wound-healing, Transwell, DAPI staining, and caspase-3 assays, respectively. For in vivo study, apatinib was delivered by gastric gavage into PDX models, and then efficacy and toxicity were determined by experimental peritoneal cancer index (ePCI) score and pathological examinations.

Results

Our results showed that apatinib significantly inhibited the proliferation and migration of MPM cells in vitro and induced cell cycle arrest. Studies on PDX models concurred that apatinib effectively suppressed subphrenic and liver invasions of nude mice. Moreover, histopathological analysis found that lymphocyte infiltration, coagulation necrosis and eosinophilic cell fragments were detected in tumor tissues after apatinib treatment. Apatinib showed no obvious effects on body mass of models and did not affect function of important organs, except for occasional focal lymphoid infiltration of liver (16.7%) and cardiac muscle (16.7%).

Conclusions

We successfully established MPM PDX models and primary cell lines, and confirmed that apatinib effectively inhibited proliferation and metastasis of MPM in vitro and in vivo study.

Molecular characterization of diffuse malignant peritoneal mesothelioma

Malignant peritoneal mesothelioma is a rare aggressive tumor that arises from the peritoneal lining. While recurrent BAP1 mutations have been identified in a subset of mesotheliomas, molecular characteristics of peritoneal mesotheliomas, including those lacking BAP1 alterations, remain poorly understood. Using targeted next-generation sequencing, we examined the molecular features of 26 diffuse malignant peritoneal mesotheliomas. As part of an exploratory analysis, we analyzed an additional localized peritoneal mesothelioma and one well-differentiated papillary mesothelioma with invasive foci. Genomic characterization identified categories of diffuse malignant peritoneal mesotheliomas: The first group included 18 (69%) tumors with recurrent BAP1 alterations, with eight (31%) having more than one BAP1 alterations, and concomitant alterations in PBRM1 (46%) and SETD2 (35%). All tumors with complete loss of BAP1 expression by immunohistochemistry harbored BAP1 molecular alterations. PBRM1 alterations were significantly enriched in the BAP1-altered cohort. Frequent copy number loss of BAP1, ARID1B, PRDM1, PBRM1, SETD2, NF2, and CDKN2A was noted. The second group included eight (31%) BAP1-wild-type tumors: two with TP53 mutations, one with a TRAF7 activating mutation, one with a SUZ12 inactivating mutation, and three with ALK rearrangements that we previously published. One TP53-mutant biphasic mesothelioma showed evidence of genomic near-haploidization showing loss of heterozygosity of all chromosomes except 5, 7, 16, and 20. The localized peritoneal mesothelioma harbored a nonsense CHEK2 mutation, and the well-differentiated papillary mesothelioma with invasive foci harbored no reportable variants. In conclusion, we described the genetic categories of diffuse malignant peritoneal mesotheliomas, with BAP1-mutant and BAP1-wild-type groups. Our findings implicated DNA repair, epigenetics, and cell cycle regulation in the pathogenesis of peritoneal mesotheliomas, with identification of potential therapeutic targets.

Mutational Profile of Malignant Pleural Mesothelioma (MPM) in the Phase II RAMES Study

Simple Summary

Malignant pleura Mesothelioma (MPM) is an aggressive cancer arising from the mesothelial cells of the pleura. About 80% of mesothelioma cases are linked to asbestos exposure; the remainder may be related to prior chest radiation, genetic predisposition or spontaneous occurrence. Understanding the genetic alterations that drive MPM is critical for successful development of diagnostics, prognostics and personalized therapeutic modalities. Because MPM is rare, genomic studies are limited and have typically involved a small number of samples. The aim of our study was to understand the mutational landscape of MPM. Our analysis identified significantly mutated genes. This study on a rare tumor type will be important for patients “in real life”.

Abstract

Purpose: Malignant pleural mesothelioma (MPM) is an aggressive cancer. Data are not available in prospective trials on correlations between genetic alterations and outcomes of therapies. In this study, we assessed the genetic profile of MPM patients (pts) in tissue samples. Patients and Methods: From December 2016 to July 2018 (end of enrolment), 164 pts were enrolled. We evaluated by targeted sequencing the mutational profile of a panel of 34 genes: ACTB, ACTG1, ACTG2, ACTR1A, BAP1, CDH8, CDK4, CDKN2A, CDKN2B, COL3A1, COL5A2, CUL1, DHFR, GOT1, KDR, KIT, MXRA5, NF2, NFRKB, NKX6-2, NOD2, PCBD2, PDZK1IP1, PIK3CA, PIK3CB, PSMD13, RAPGEF6, RDX, SETDB1, TAOK1, TP53, TXNRD1, UQCRC1, XRCC6. Genetic profiling was correlated with clinical and pathological variables. Results: Overall, 110 pts (67%) from both treatment arms had samples available for molecular analysis. Median age was 63 years (45–81), 25.5% (n = 28) were females, and 74.5% (n = 82) were males. Tumor histotype was 81.8% (n = 90) epithelioid and 18.2% (n = 20) non-epithelioid; 28.5% of the tumors (n = 42) were stage IV, 71.5% (n = 68) were stage III. Targeted sequencing of tissue specimens identified 275 functional somatic mutations in the 34 genes analyzed. The number of mutated genes was positively associated with higher stage and metastatic disease (p = 0.025). RDX (42%), MXRA5 (23%), BAP1 (14%), and NF2 (11%) were the most frequently mutated genes. Mutations in RAPGEF6 (p = 0.03) and ACTG1 (p = 0.02) were associated with the non-epithelioid subtype, and mutations in BAP1 (p = 0.04) were related to progression-free survival (PFS) > 6 months. Conclusions: In the Ramucirumab Mesothelioma clinical trial (RAMES), mutation of the gene BAP1 is related to a prolonged PFS for patients treated with platinum/pemetrexed regimens (p = 0.04).

Chicago Consensus Working Group. The Chicago Consensus on Peritoneal Surface Malignancies: Management of Peritoneal Mesothelioma

The Chicago Consensus Working Group provides multidisciplinary recommendations for the management of peritoneal mesothelioma. These guidelines are developed with input from leading experts including surgical oncologists, medical oncologists, pathologists, radiologists, palliative care physicians, and pharmacists. These guidelines recognize and address the emerging need for increased awareness of the appropriate management of peritoneal surface disease. They are not intended to replace the quest for higher levels of evidence.

Chicago Consensus Working Group. The Chicago Consensus on peritoneal surface malignancies: Management of peritoneal mesothelioma

The Chicago Consensus Working Group provides multidisciplinary recommendations for the management of peritoneal mesothelioma. These guidelines are developed with input from leading experts, including surgical oncologists, medical oncologists, pathologists, radiologists, palliative care physicians, and pharmacists. These guidelines recognize and address the emerging need for increased awareness of the appropriate management of peritoneal surface disease. They are not intended to replace the quest for higher levels of evidence.

Fluorescence in situ hybridization (FISH) provides estimates of minute and interstitial BAP1, CDKN2A, and NF2 gene deletions in peritoneal mesothelioma

The aim of this study was to assess the performance of fluorescence in situ hybridization (FISH) in identifying the copy number profiles of the three key peritoneal mesothelioma tumor suppressor genes BAP1, CDKN2A, and NF2, with particular emphasis on minute homozygous deletions, a copy number abnormality recently unveiled at the 3p21 (BAP1) chromosomal region using high-throughput methods. FISH was performed on 75 formalin-fixed-paraffin-embedded peritoneal mesotheliomas and recognized two types of monoallelic loss (monosomy, and hemizygous deletion) and two types of biallelic loss (canonical homozygous deletion with a complete loss of FISH signal and homozygous deletion with diminished signal). Diminished FISH signals revealed deletions occurring within the genomic region covered by the gene-specific probe and affected all three tumor suppressors. BAP1 homozygous deletions with diminished signal outnumbered canonical homozygous deletions (13 vs 3): conversely, canonical homozygous deletions were prevalent for CDKN2A (2 vs 14). Diminished signal homozygous deletion was the only pattern of biallelic loss observed for NF2 (2 cases). Hemizygous deletion mainly affected BAP1 (21 vs 6), while monosomy was prevalent for CDKN2A (14 vs 7) and particularly for NF2 where it accounts for all monoallelic losses. FISH/immunohistochemistry (BAP1, CDKN2A, and MTAP) correlation showed that all homozygous deletions, including those with diminished signals, resulted in a null BAP1 and CDKN2A immunophenotype but only canonical CDKN2A homozygous deletions resulted in MTAP loss of expression. BAP1 hemizygous deletion, but not monosomy, was also invariably associated with loss of protein expression whereas neither type of CDKN2A monoallelic loss correlated with p16 or MTAP immunohistochemistry. Array comparative genomic hybridization performed on a spontaneously emerging peritoneal mesothelioma cell line provided support for the interpretation of the FISH patterns and allowed us to extend the number of chromatin remodeling factors involved in mesothelioma to SETD7 and PCGF5, two previously unreported genes.

Malignant Peritoneal Mesothelioma: Patterns of Care and Survival in the Netherlands: A Population-Based Study

BACKGROUND

Malignant peritoneal mesothelioma (MPM) is a rare and aggressive disease. Recently, focus has shifted toward a more aggressive and multimodal treatment approach. This study aimed to assess the patterns of care and survival for MPM patients in the Netherlands on a nationwide basis.

METHODS

The records of patients with a diagnosis of MPM from 1993 to 2016 were retrieved from the Dutch Cancer Registry. Data regarding diagnosis, staging, treatment, and survival were extracted. Cox regression analyses and Kaplan-Meier survival curves were used to study overall survival.

RESULTS

Between 1993 and 2016, MPM was diagnosed for 566 patients. Overall, the prognosis was very poor (24% 1-year survival). The most common morphologic subtype was the epithelioid subtype (88%), followed by the biphasic (8%) and sarcomatoid (4%) subtypes. Surgical treatment has become more common in recent years, which most likely has resulted in improved survival rates. In this study, improved survival was independently associated with hyperthermic intraperitoneal chemotherapy (hazard ratio [HR], 0.33; 95% confidence interval [CI], 0.21-0.55) and surgery with adjuvant systemic chemotherapy (HR, 0.33; 95% CI, 0.23-0.48). Nonetheless, most patients (67%) do not receive any form of anti-cancer treatment.

CONCLUSION

This study indicated that MPM still is a rare and fatal disease. The survival rates in the Netherlands have improved slightly in the past decade, most likely due to more aggressive treatment approaches and increased use of surgery. However, most patients still do not receive cancer-directed treatment. To improve MPM management, and ultimately survival, care should be centralized in expert medical centers.

BAP1 haploinsufficiency predicts a distinct immunogenic class of malignant peritoneal mesothelioma

Background

Malignant peritoneal mesothelioma (PeM) is a rare and fatal cancer that originates from the peritoneal lining of the abdomen. Standard treatment of PeM is limited to cytoreductive surgery and/or chemotherapy, and no effective targeted therapies for PeM exist. Some immune checkpoint inhibitor studies of mesothelioma have found positivity to be associated with a worse prognosis.

Methods

To search for novel therapeutic targets for PeM, we performed a comprehensive integrative multi-omics analysis of the genome, transcriptome, and proteome of 19 treatment-naïve PeM, and in particular, we examined BAP1 mutation and copy number status and its relationship to immune checkpoint inhibitor activation.

Results

We found that PeM could be divided into tumors with an inflammatory tumor microenvironment and those without and that this distinction correlated with haploinsufficiency of BAP1. To further investigate the role of BAP1, we used our recently developed cancer driver gene prioritization algorithm, HIT’nDRIVE, and observed that PeM with BAP1 haploinsufficiency form a distinct molecular subtype characterized by distinct gene expression patterns of chromatin remodeling, DNA repair pathways, and immune checkpoint receptor activation. We demonstrate that this subtype is correlated with an inflammatory tumor microenvironment and thus is a candidate for immune checkpoint blockade therapies.

Conclusions

Our findings reveal BAP1 to be a potential, easily trackable prognostic and predictive biomarker for PeM immunotherapy that refines PeM disease classification. BAP1 stratification may improve drug response rates in ongoing phases I and II clinical trials exploring the use of immune checkpoint blockade therapies in PeM in which BAP1 status is not considered. This integrated molecular characterization provides a comprehensive foundation for improved management of a subset of PeM patients.

Electronic supplementary material

The online version of this article (10.1186/s13073-019-0620-3) contains supplementary material, which is available to authorized users.

Well-differentiated papillary mesothelioma of the peritoneum is genetically defined by mutually exclusive mutations in TRAF7 and CDC42

Well-differentiated papillary mesothelioma is an uncommon mesothelial neoplasm that most frequently arises in the peritoneal cavity of women of reproductive age. Whereas malignant mesothelioma is an aggressive tumor associated with poor outcome, well-differentiated papillary mesothelioma typically exhibits indolent behavior. However, histologically differentiating between these two entities can be challenging, necessitating the development of distinguishing biomarkers. While the genetic alterations that drive malignant mesothelioma have recently been determined, the molecular pathogenesis of well-differentiated papillary mesothelioma is unknown. Here we performed genomic profiling on a cohort of ten well-differentiated papillary mesothelioma of the peritoneum. We identified that all tumors harbored somatic missense mutations in either the TRAF7 or CDC42 genes, and lacked alterations involving BAP1, NF2, CDKN2A, DDX3X, SETD2, and ALK that are frequent in malignant mesothelioma. We recently identified that another mesothelial neoplasm, adenomatoid tumor of the genital tract, is genetically defined by somatic missense mutations in the TRAF7 gene, indicating a shared molecular pathogenesis between well-differentiated papillary mesothelioma and adenomatoid tumors. To the best of our knowledge, well-differentiated papillary mesothelioma is the first human tumor type found to harbor recurrent mutations in the CDC42 gene, which encodes a Rho family GTPase. Immunohistochemistry demonstrated intact BAP1 expression in all cases of well-differentiated papillary mesothelioma, indicating that this is a reliable marker for distinguishing well-differentiated papillary mesothelioma from malignant mesotheliomas that frequently display loss of expression. Additionally, all well-differentiated papillary mesothelioma demonstrated robust expression of L1 cell adhesion molecule (L1CAM), a marker of NF-kB pathway activation, similar to that observed in adenomatoid tumors. In contrast, we have previously shown that L1CAM staining is not observed in normal mesothelial cells and malignant mesotheliomas of the peritoneum. Together, these studies demonstrate that well-differentiated papillary mesothelioma is genetically defined by mutually exclusive mutations in TRAF7 and CDC42 that molecularly distinguish this entity from malignant mesothelioma.

First case report of malignant peritoneal mesothelioma and oral verrucous carcinoma in a patient with a germline PTEN mutation: a combination of extremely rare diseases with probable further implications

BACKGROUND

The PTEN-hamartoma-tumor-syndrome (PHTS) is caused by germline mutations in Phosphatase and Tensin homolog (PTEN) and predisposes to the development of several typical malignancies. Whereas PTEN mutations have been implicated in the occurrence of malignant mesotheliomas, the genetic landscape of verrucous carcinomas (VC) is largely uncharted. Both VC and malignant peritoneal mesotheliomas (MPM) are exceedingly rare and a potential link between these malignancies and PHTS has never been reported.

CASE PRESENTATION

We here describe the clinical course of a PHTS patient who, in addition to a typical thyroid carcinoma at the age of 36 years, developed a highly-differentiated oral VC and an epithelioid MPM six years later. The patient with a history of occupational asbestos exposure underwent cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for MPM. The clinical diagnosis of PHTS was consequently corroborated by a germline PTEN deletion. Sequencing of tumor tissue revealed a second hit in PTEN in the thyroid carcinoma and VC, confirmed by a PTEN loss and activation of the PI3K/AKT pathway in immunohistochemistry. Furthermore, additional somatic mutations in the thyroid carcinoma as well as in the VC were detected, whereas the genetics of MPM remained unrevealing.

DISCUSSION AND CONCLUSIONS

We here report the very unusual clinical course of a patient with rare tumors that have a germline mutation first hit in PTEN in common. Since this patient was exposed to asbestos and current evidence suggests molecular mechanisms that might render PHTS patients particularly susceptible to mesothelioma, we strongly recommend PHTS patients to avoid even minimal exposure.

Pre-clinical Models for Malignant Mesothelioma Research: From Chemical-Induced to Patient-Derived Cancer Xenografts

Malignant mesothelioma (MM) is a rare disease often associated with environmental exposure to asbestos and other erionite fibers. MM has a long latency period prior to manifestation and a poor prognosis. The survival post-diagnosis is often less than a year. Although use of asbestos has been banned in the United States and many European countries, asbestos is still being used and extracted in many developing countries. Occupational exposure to asbestos, mining, and migration are reasons that we expect to continue to see growing incidence of mesothelioma in the coming decades. Despite improvements in survival achieved with multimodal therapies and cytoreductive surgeries, less morbid, more effective interventions are needed. Thus, identifying prognostic and predictive biomarkers for MM, and developing novel agents for targeted therapy, are key unmet needs in mesothelioma research and treatment. In this review, we discuss the evolution of pre-clinical model systems developed to study MM and emphasize the remarkable capability of patient-derived xenograft (PDX) MM models in expediting the pre-clinical development of novel therapeutic approaches. PDX disease model systems retain major characteristics of original malignancies with high fidelity, including molecular, histopathological and functional heterogeneities, and as such play major roles in translational research, drug development, and precision medicine.

Peritoneal Metastases from Malignant Mesothelioma

Diffuse malignant peritoneal mesothelioma (MPM) is a rare cancer that is ultimately fatal in almost all afflicted individuals. Morbidity and mortality from MPM is due to its propensity to progress locoregionally within the abdominal cavity. Patients with MPM most commonly present with nonspecific abdominal symptoms that usually lead to diagnosis when the condition is relatively advanced. MPM is considered a chemotherapy-resistant malignancy.

Mutational Profiling of Malignant Mesothelioma Revealed Potential Therapeutic Targets in EGFR and NRAS

Pemetrexed and platinum (PP) combination chemotherapy is the current standard first-line therapy for treatment of malignant mesothelioma (MM). However, a useful predictive biomarker for PP therapy is yet to be found. Here, we performed targeted exome sequencing to profile somatic mutations and copy number variations in 12 MM patients treated with PP therapy. We identified 187 somatic mutations in 12 patients (65 synonymous, 102 missense, 2 nonsense, 5 splice site, and 13 small coding insertions/deletions). We identified somatic mutations in 23 genes including BAP1, TP53, NRAS, and EGFR. Interestingly, rare NRAS p.Q61K and EGFR exon 19 deletions were observed in 2 patients. We also found somatic chromosomal copy number deletions in CDKN2A and CDKN2B genes. Genetic alteration related to response after PP therapy was not found. Somatic mutation profiling in MM patients receiving PP therapy revealed genetic alterations in potential therapeutic targets such as NRAS and EGFR. No alterations in genes with potential predictive role for PP therapy were found.

Advances in systemic therapy for malignant mesothelioma: future perspectives

Malignant mesothelioma is a rare and aggressive form of cancer affecting the mesothelium. This mainly occupational disease is becoming more common in those countries where asbestos has been used for industrial applications. Notwithstanding the progress made in the field, patients do not survive more than 12 months on average with standard treatment. With the advent of next generation sequencing, it is now possible to study the mutational landscape of each tumor with the aim of identifying the genetic aberrations driving tumorigenesis. This review encompasses the latest research in the field, with particular attention to new chemotherapy combinatorial regimens, molecular targets and immunotherapies, providing a comprehensive picture of the current and future treatment options for malignant mesothelioma patients.

Peritoneal Mesothelioma with Residential Asbestos Exposure. Report of a Case with Long Survival (Seventeen Years) Analyzed by Cgh-Array

Malignant mesothelioma is a rare and aggressive tumor with limited therapeutic options. We report a case of a malignant peritoneal mesothelioma (MPM) epithelioid type, with environmental asbestos exposure, in a 36-year-old man, with a long survival (17 years). The patient received standard treatment which included cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC).

METHODS AND RESULTS

Molecular analysis with comparative genomic hybridization (CGH)-array was performed on paraffin-embedded tumoral samples. Multiple chromosomal imbalances were detected. The gains were prevalent. Losses at 1q21, 2q11.1→q13, 8p23.1, 9p12→p11, 9q21.33→q33.1, 9q12→q21.33, and 17p12→p11.2 are observed. Chromosome band 3p21 (BAP1), 9p21 (CDKN2A) and 22q12 (NF2) are not affected. Conclusions: the defects observed in this case are uncommon in malignant peritoneal mesothelioma. Some chromosomal aberrations that appear to be random here, might actually be relevant events explaining the response to therapy, the long survival and, finally, may be considered useful prognostic factors in peritoneal malignant mesothelioma (PMM).

Diagnostic accuracy of BRCA1-associated protein 1 in malignant mesothelioma: a meta-analysis

Background

Conventional measurements are not always helpful in the diagnosis of malignant mesothelioma (MM). Increasing studies indicate that loss of BRCA1–associated protein 1 (BAP1) detected by immunohistochemistry (IHC) is a useful diagnostic marker for MM. In this meta-analysis, we investigated the diagnostic accuracy of BAP1 in MM.

Results

In total, 12 eligible studies with a total of 1824 patients were selected. Results indicated that loss of BAP1 sustained a pooled sensitivity of 0.56 (95% CI, 0.50–0.62), specificity of 1.00 (95% CI, 0.95–1.00), PLR of 548.82 (95% CI, 11.31–2.7 × 104), NLR of 0.44 (95% CI, 0.39–0.50), DOR of 1247.78 (95% CI, 25.08 −6.2 × 104) in discriminating MM from non-MM. The AUC of 0.72, reflecting the SROC, indicated moderate diagnostic accuracy. Subgroup analysis showed that BAP1 detection in histological specimens owned the higher diagnostic performance than cytological ones. In addition, BAP1 showed superior diagnostic accuracy in epithelioid MM than biphasic or sarcomatoid MM.

Materials and Methods

PubMed, Embase and the Cochrane Library and reference lists of related articles were searched, and studies that evaluated the utility of BAP1 in MM were included. Data from eligible studies were pooled to estimate sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR). Summary receiver operating curves (SROC) was applied to estimate overall diagnostic accuracy.

Conclusions

Current meta-analysis indicates that detection of BAP1 by IHC is a useful diagnostic marker for MM. Loss of BAP1 almost provides confirming diagnosis for MM, while positive staining for BAP1 is not enough to exclude non-MM.

Somatic BRCA1-associated protein 1 (BAP1) loss is an early and rare event in esophageal adenocarcinoma

Esophageal cancer is the eighth most common malignant tumor worldwide, and the number of incidences of esophageal adenocarcinoma is increasing in the Western world. Despite improvements in perioperative treatment, the overall survival rate of patients with esophageal adenocarcinoma remains poor. Breast cancer type 1 susceptibility protein (BRCA1)-associated protein (BAP1) is located on chromosome 3p21, and it is an enzyme with ubiquitin carboxyl hydrolase activity that regulates cell growth. It interacts with BRCA1, and the nuclear localization of BAP1 is required for its tumor suppressor function. BAP1 is frequently mutated in uveal melanomas, malignant mesothelioma and several carcinomas, including a subtype of renal cell carcinoma, intrahepatic cholangiocarcinoma and squamous cell carcinoma of the esophagus. Furthermore, several germline-associated mutations of tumors have been described (BAP1 hereditary cancer syndrome). However, the importance and frequency of BAP1 alterations in adenocarcinoma of the esophagus remain to be elucidated. In the present study, tissue microarrays of 332 resected adenocarcinomas (including a few cases of concomitant Barrett dysplasia) of the esophagus were constructed. The tumor tissue was analyzed using immunohistochemistry to investigate the levels of BAP1 expression. Fibroblasts or inflammatory cells served as an internal positive control. Three adenocarcinomas revealed nuclear loss of BAP1 (0.9%). One case with concomitant Barrett dysplasia also exhibited a loss of BAP1. Of the resected adenocarcinomas, 329 of them exhibited an intact and uniform strong nuclear staining pattern. To the best of our knowledge, this is the first description of BAP1 deficiency in adenocarcinomas of the esophagus. Furthermore, it has been demonstrated that BAP1 loss is possibly an early event in esophageal adenocarcinoma. These results warrant further functional and clinical evaluation.

BAP1 Is Altered by Copy Number Loss, Mutation, and/or Loss of Protein Expression in More Than 70% of Malignant Peritoneal Mesotheliomas

INTRODUCTION

Malignant mesothelioma is a deadly disease that is strongly associated with asbestos exposure. Peritoneal mesotheliomas account for 10% of all the cases. BRCA1 associated protein 1 (BAP1) is a deubiquitinating hydrolase that plays a key role in various cellular processes. Germline and somatic inactivation of BRCA1 associated protein 1 gene (BAP1) is frequent in pleural mesothelioma; however, little is known about its status in peritoneal mesothelioma.

METHODS

Taking advantage of the extensive French National Network for the Diagnosis of Malignant Pleural Mesothelioma and Rare Peritoneal Tumors and the French National Network for the Treatment of Rare Peritoneal Surface Malignancies, we collected biological material and clinical and epidemiological data for 46 patients with peritoneal mesothelioma. The status of BAP1 was evaluated at the mutational and protein expression levels and combined with our previous data on copy number alterations assessed in the same samples.

RESULTS

We detected mutations in 32% of the malignant peritoneal mesotheliomas analyzed. In addition, we have previously reported that copy number losses occurred in 42% of the samples included in this series. Overall, 73% of the malignant peritoneal mesotheliomas analyzed carried at least one inactivated BAP1 allele, but only 57% had a complete loss of its protein nuclear expression. Better overall survival was observed for patients with BAP1 mutations (p = 0.04), protein expression loss (p = 0.016), or at least one of these alterations (p = 0.007) independently of tumor histological subtype, age, and sex.

CONCLUSIONS

As in pleural mesothelioma, inactivation of BAP1 is frequent in peritoneal mesotheliomas. We found that BAP1 protein nuclear expression is a good prognostic factor and a more reliable marker for the complete loss of BAP1 activity than mutation or copy number loss.

Genomic profiling of malignant peritoneal mesothelioma reveals recurrent alterations in epigenetic regulatory genes BAP1, SETD2, and DDX3X

Malignant mesothelioma is a rare cancer that arises from the mesothelial cells that line the pleural cavity and less commonly from the peritoneal lining of the abdomen and pelvis. Most pleural mesotheliomas arise in patients with a history of asbestos exposure, whereas the association of peritoneal mesotheliomas with exposure to asbestos and other potential carcinogens is less clear, suggesting that the genetic alterations that drive malignant peritoneal mesothelioma may be unique from those in pleural mesothelioma. Treatment options for all malignant mesotheliomas are currently limited, with no known targeted therapies available. To better understand the molecular pathogenesis of malignant peritoneal mesothelioma, we sequenced 510 cancer-related genes in 13 patients with malignant mesothelioma arising in the peritoneal cavity. The most frequent genetic alteration was biallelic inactivation of the BAP1 gene, which occurred in 9/13 cases, with an additional two cases demonstrating monoallelic loss of BAP1. All 11 of these cases demonstrated loss of BAP1 nuclear staining by immunohistochemistry, whereas two tumors without BAP1 alteration and all 42 cases of histologic mimics in peritoneum (8 multilocular peritoneal inclusion cyst, 6 well-differentiated papillary mesothelioma of the peritoneum, 16 adenomatoid tumor, and 12 low-grade serous carcinoma of the ovary) demonstrated intact BAP1 nuclear staining. Additional recurrently mutated genes in this cohort of malignant peritoneal mesotheliomas included NF2 (3/13), SETD2 (2/13), and DDX3X (2/13). While these genes are known to be recurrently mutated in pleural mesotheliomas, the frequencies are distinct in peritoneal mesotheliomas, with nearly 85% of peritoneal tumors harboring BAP1 alterations versus only 20-30% of pleural tumors. Together, these findings demonstrate the importance of epigenetic modifiers including BAP1, SETD2, and DDX3X in mesothelial tumorigenesis and suggest opportunities for targeted therapies.

Whole exome sequencing of independent lung adenocarcinoma, lung squamous cell carcinoma, and malignant peritoneal mesothelioma: A case report

The presence of multiple primary tumors (MPT) in a single patient has been identified with an increasing frequency. A critical issue is to establish if the second tumor represents an independent primary cancer or a metastasis. Therefore, the assessment of MPT clonal origin might help understand the disease behavior and improve the management/prognosis of the patient.Herein, we report a 73-year-old male smoker who developed 2 primary lung cancers (adenocarcinoma and squamous cell carcinoma) and a malignant peritoneal mesothelioma (PM).Whole exome sequencing (WES) of the 3 tumors and of germline DNA was performed to determine the clonal origin and identify genetic cancer susceptibility.Both lung cancers were characterized by a high mutational rate with distinct mutational profiles and activation of tumor-specific pathways. Conversely, the PM harbored a relative low number of genetic variants and a novel mutation in the WT1 gene that might be involved in the carcinogenesis of nonasbestos-related mesothelioma. Finally, WES of the germinal DNA displayed several single nucleotide polymorphisms in DNA repair genes likely conferring higher cancer susceptibility.Overall, WES did not disclose any somatic genetic variant shared across the 3 tumors, suggesting their clonal independency; however, the carcinogenic effect of smoke combined with a deficiency in DNA repair genes and the patient advanced age might have been responsible for the MPT development. This case highlights the WES importance to define the clonal origin of MPT and susceptibility to cancer.

Switching off malignant mesothelioma: exploiting the hypoxic microenvironment

Malignant mesotheliomas are aggressive, asbestos-related cancers with poor patient prognosis, typically arising in the mesothelial surfaces of tissues in pleural and peritoneal cavity. The relative unspecific symptoms of mesotheliomas, misdiagnoses, and lack of precise targeted therapies call for a more critical assessment of this disease. In the present review, we categorize commonly identified genomic aberrations of mesotheliomas into their canonical pathways and discuss targeting these pathways in the context of tumor hypoxia, a hallmark of cancer known to render solid tumors more resistant to radiation and most chemo-therapy. We then explore the concept that the intrinsic hypoxic microenvironment of mesotheliomas can be Achilles' heel for targeted, multimodal therapeutic intervention.

Comparative genetics of diffuse malignant mesothelioma tumors of the peritoneumand pleura, with focus on BAP1 expression

Malignant mesothelioma (MM) is a malignancy arising from the mesothelial cells lining the thoracic and abdominal serosal cavities. The pleural space is the most commonly affected site, accounting for about 80% of cases, while peritoneum makes up the majority of the remaining 20%. The different types of mesotheliomas are generally considered as distinct diseases with specific risk factors, therapeutic strategies and prognoses. Epidemiological and clinical differences between pleural and peritoneal MM raise questions about the involvement of different molecular mechanisms. Since the BAP1 gene is involved in the BAP1 cancer syndrome and seems to be a prognostic factor in MM, this review presents an overview of BAP1 alterations in mesothelioma comparing pleural and peritoneal localizations.

A Tumor-Specific Neo-Antigen Caused by a Frameshift Mutation in BAP1 Is a Potential Personalized Biomarker in Malignant Peritoneal Mesothelioma

Malignant peritoneal mesothelioma (MPM) is an aggressive rare malignancy associated with asbestos exposure. A better understanding of the molecular pathogenesis of MPM will help develop a targeted therapy strategy. Oncogene targeted depth sequencing was performed on a tumor sample and paired peripheral blood DNA from a patient with malignant mesothelioma of the peritoneum. Four somatic base-substitutions in NOTCH2, NSD1, PDE4DIP, and ATP10B and 1 insert frameshift mutation in BAP1 were validated by the Sanger method at the transcriptional level. A 13-amino acids neo-peptide of the truncated Bap1 protein, which was produced as a result of this novel frameshift mutation, was predicted to be presented by this patient's HLA-B protein. The polyclonal antibody of the synthesized 13-mer neo-peptide was produced in rabbits. Western blotting results showed a good antibody-neoantigen specificity, and Immunohistochemistry (IHC) staining with the antibody of the neo-peptide clearly differentiated neoplastic cells from normal cells. A search of the Catalogue of Somatic Mutations in Cancer (COSMIC) database also revealed that 53.2% of mutations in BAP1 were frameshift indels with neo-peptide formation. An identified tumor-specific neo-antigen could be the potential molecular biomarker for personalized diagnosis to precisely subtype rare malignancies such as MPM.

Diagnosis and management of patients with malignant peritoneal mesothelioma

Malignant peritoneal mesothelioma (MPM) is a rare neoplastic condition that arises, usually diffusely, from the serosal membranes of the abdominal cavity. MPM represents about 7% to 10% of all mesothelioma diagnoses and this translates into approximately 800 cases per year in the United States. The disease has variable tumor biology but progression, when it occurs, is almost always within the abdominal cavity. Although many patients can be successfully treated at initial presentation, the disease is almost always fatal in time. It afflicts men and women almost equally and the median age at presentation is 50 years. The diagnosis is made when a diffuse malignant process within the abdominal cavity is observed and a tissue sample reveals the characteristic histopathology and immunohistochemical profile of mesothelioma. Initial staging is usually via a cross sectional imaging study of the abdomen and pelvis making sure that the lower thorax is also assessed. If the disease burden and distribution is favorable then operative exploration, cytoreduction, and hyperthermic intraperitoneal chemotherapy (HIPEC) are considered first line treatment in selected patients. Systemic pemetrexed and cisplatin (or gemcitabine) have modest response rates that are of limited duration. Research advances with novel systemic or intraperitoneal agents hold promise.

Diffuse Malignant Peritoneal Mesothelioma Presenting with Psammomatous Calcification on a Cervical Smear

BACKGROUND

Psammoma bodies in cervical smears are rare but may be associated with benign and malignant diseases of the female genital tract.

CASE

A 52-year-old nulliparous woman presented with a 2-month history of intermittent vaginal spotting and post-coital bleeding. A cervical smear showed an inconclusive high-grade glandular lesion with psammomatous calcification. Previous cervical smears had been normal. This smear contained papillary tissue fragments, occasional spheres of gland-like cells and frequent psammoma bodies. The patient underwent a laparoscopic hysterectomy, bilateral salpingo-oophorectomy and omentectomy. The surface of the omentum and both ovaries contained psammoma bodies with groups of cells identical to those in the cervical smear. Within the omentum, there were invasive malignant epithelioid cells positive for CK7, CK5/6, calretinin, D2-40, WT-1, CK5/6, p16 and EMA. Desmin and PAX-8 immunostains were negative. There was also evidence of BRCA1-associated protein 1 (BAP1) dysfunction compatible with diffuse malignant peritoneal mesothelioma (DMPM).

CONCLUSION

We describe the first reported case of DMPM presenting with an abnormal cervical smear, a rare but important differential diagnosis to consider in abnormal cervical smears showing psammomatous calcification.

Comprehensive review of BAP1 tumor predisposition syndrome with report of two new cases

The BRCA1-associated protein-1 (BAP1) tumor predisposition syndrome (BAP1-TPDS) is a recently identified hereditary cancer syndrome. Germline mutations in this tumor suppressor gene predispose families to the development of various malignancies. The molecular functions of the gene as well as the clinical phenotype of the syndrome are still being clarified. We sought to conduct a comprehensive review of published research into BAP1-TPDS to more thoroughly delineate the clinical implications of germline BAP1 mutations. We also report two additional families with germline BAP1 mutations. Current evidence demonstrates that germline BAP1 mutations predispose families to uveal melanoma, renal cell carcinoma, malignant mesothelioma, cutaneous melanoma, and possibly to a range of other cancers as well. Some of these cancers tend to be more aggressive, have a propensity to metastasize, and onset earlier in life in patients with BAP1 mutations as compared to non-predisposed patients with equivalent cancers. Although further research is necessary, this information can aid in the management, diagnosis, and therapy of these patients and their families, and highlights the importance of genetic counseling.