Genomic copy number alterations in 33 malignant peritoneal mesothelioma analyzed by comparative genomic hybridization array

Effects of SETD2 on telomere length and malignant transformation property of Met-5A after one-month crocidolite exposure

Crocidolite is a carcinogen contributing to the pathogenesis of malignant mesothelioma. This study aimed to characterize the possible telomere-related events mediating the malignant transformation of mesothelial cells with and without SETD2 under crocidolite exposure. The crocidolite concentration resulting in 90% viable SETD2 knockout Met-5A (Met-5ASETD2-KO) and Met-5A were estimated to be 0.71 μg/cm2 and 1.8 μg/cm2, respectively, during 72 h of exposure, which was further employed in chronical crocidolite exposure during a 72 h exposure interval per time up to 1 month. Chronical crocidolite-exposed Met-5ASETD2-KO (chronical Cro-Met-5ASETD2-KO) had higher colony formation and increased telomerase reverse transcriptase (TERT) protein levels than chronical crocidolite-exposed Met-5A (chronical Cro-Met-5A) and Met-5ASETD2-KO. Chronical Cro-Met-5ASETD2-KO had longer telomere length (TL) than chronical Cro-Met-5A, although there were no changes in TL for either chronical Cro-Met-5A or chronical Cro-Met-5ASETD2-KO compared with their corresponding cells without crocidolite exposure. BIBR 1532, an inhibitor targeting TERT, partially reduced colony formation and TL for chronical Cro-Met-5ASETD2-KO, while BIBR 1532 reduced TL but had no effect on colony formation for chronical Cro-Met-5A. Therefore, SETD2 deficient mesothelial cells are susceptible to malignant transformation during chronical crocidolite exposure, and TERT-dependent TL modification likely partially drives SETD2 loss-mediated early onset of mesothelial malignant transformation.

Genomic landscape of pleural and peritoneal mesothelioma tumours

BACKGROUND

Malignant pleural and peritoneal mesotheliomas are rare malignancies with unacceptable poor prognoses and limited treatment options. The genomic landscape is mainly characterised by the loss of tumour suppressor genes and mutations in DNA repair genes. Currently, data from next-generation sequencing (NGS) of mesothelioma tumours is restricted to a limited number of cases; moreover, data comparing molecular features of mesothelioma from the pleural and peritoneal origin with NGS are lacking.

METHODS

We analysed 1113 pleural mesothelioma and 355 peritoneal mesothelioma samples. All tumours were sequenced with the FoundationOne® or FoundationOne®CDx assay for detection of substitutions, insertion-deletions, copy-number alterations and selected rearrangements in at least 324 cancer genes.

RESULTS

This analysis revealed alterations in 19 genes with an overall prevalence of at least 2%. Alterations in BAP1, CDKN2A, CDKN2B, NF2, MTAP, TP53 and SETD2 occurred with a prevalence of at least 10%. Peritoneal, compared to pleural mesothelioma, was characterised by a lower prevalence of alterations in CDKN2A, CDKN2B and MTAP. Moreover, we could define four distinct subgroups according to alterations in BAP1 and CDKN2A/B. Alterations in Hedgehog pathway-related genes (PTCH1/2 and SUFU) and Hippo pathway-related gene (NF2) as well as KRAS, EGFR, PDGFRA/B, ERBB2 and FGFR3 were detected in both cohorts.

CONCLUSION

Here, we report the molecular aberrations from the largest cohort of patients with mesothelioma. This analysis identified a proportion of patients with targetable alterations and suggests that molecular profiling can identify new treatment options for patients with mesothelioma.

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.

Malignant pleural mesothelioma: an update

Malignant mesotheliomas are rare types of cancers that affect the mesothelial surfaces, usually the pleura and peritoneum. They are associated with asbestos exposure, but due to a latency period of more than 30 years and difficult diagnosis, most cases are not detected until they reach advanced stages. Treatment options for this tumor type are very limited and survival ranges from 12 to 36 months. This review discusses the molecular physiopathology, current diagnosis, and latest therapeutic options for this disease.

Aurora Kinase A as a Diagnostic and Prognostic Marker of Malignant Mesothelioma

Background

Malignant mesothelioma (MM) is a highly aggressive cancer with a poor prognosis. Despite the use of several well-known markers, the diagnosis of MM is still challenging in some cases. we applied bioinformatics to identify key genes and screen for diagnostic and prognostic markers of MM.

Methods

The expression profiles of GSE2549 and GSE112154 microarray datasets from the Gene Expression Omnibus database contained 87 cases of MM tissue and 8 cases of normal mesothelial tissue in total. The GEO2R tool was used to detect differentially expressed genes (DEGs). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of DEGs were performed using DAVID Bioinformatics Resources. The DEGs protein-protein interaction networks were constructed from the STRING database. Cytoscape was used to identify significant modules and hub genes. The GEPIA database was used to explore relationships between hub genes and prognosis of MM. Immunohistochemistry was used to analyze protein expression in tissue microarrays with 47 Chinese MM tissues. Statistical analyses diagnostic and prognostic values.

Results

346 DEGs were identified: 111 genes upregulated, and 235 downregulated. GO analysis showed that the primary biological processes of these DEGs were cell adhesion, leukocyte migration, and angiogenesis. The main cellular components included the extracellular space, extracellular exosome, and extracellular region. The molecular functions were integrin binding, heparin binding, and calcium ion binding. KEGG pathway analysis showed that DEGs are primarily involved in PPAR signaling pathway, extracellular matrix–receptor interactions, and regulation of lipolysis in adipocytes. Survival analysis showed that seven genes—AURKA, GAPDH, TOP2A, PPARG, SCD, FABP4, and CEBPA—may be potential prognostic markers for MM. Immunohistochemical studies showed that Aurora kinase A (AURKA gene encode, Aurora-A) and GAPDH were highly expressed in MM tissue in comparison with normal mesothelial tissue. Kaplan-Meier analysis confirmed a correlation between Aurora-A protein expression and overall survival but did not confirm a correlation with GAPDH. The receiver operating characteristic curves of Aurora-A protein expression suggested acceptable accuracy (AUC = 0.827; 95% CI [0.6686 to 0.9535]; p = 0.04). The sensitivity and specificity of Aurora-A were 83.33% and 77.78%, respectively.

Conclusion

Aurora-A could be an optimal diagnostic biomarker and a potential prognostic marker for MM.

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.

Well-Differentiated Papillary Mesothelioma of the Peritoneum Is Genetically Distinct from Malignant Mesothelioma

Well-differentiated papillary mesothelioma (WDPM) is an uncommon mesothelial proliferation that is most commonly encountered as an incidental finding in the peritoneal cavity. There is controversy in the literature about whether WDPM is a neoplasm or a reactive process and, if neoplastic, whether it is a variant or precursor of epithelial malignant mesothelioma or is a different entity. Using whole exome sequencing of five WDPMs of the peritoneum, we have identified distinct mutations in EHD1, ATM, FBXO10, SH2D2A, CDH5, MAGED1, and TP73 shared by WDPM cases but not reported in malignant mesotheliomas. Furthermore, we show that WDPM is strongly enriched with C > A transversion substitution mutations, a pattern that is also not found in malignant mesotheliomas. The WDPMs lacked the alterations involving BAP1, SETD2, NF2, CDKN2A/B, LASTS1/2, PBRM1, and SMARCC1 that are frequently found in malignant mesotheliomas. We conclude that WDPMs are neoplasms that are genetically distinct from malignant mesotheliomas and, based on observed mutations, do not appear to be precursors of malignant mesotheliomas.

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.

Cisplatin unleashes Toll-like receptor 3-mediated apoptosis through the downregulation of c-FLIP in malignant mesothelioma

Toll-like receptor 3 (TLR3) is an immune receptor that behaves like a death receptor in tumor cells, thereby providing an original target for cancer therapy. The therapeutic potential of TLR3 targeting in malignant mesothelioma, an aggressive and incurable neoplasia of the pleura and peritoneum, has so far not been addressed. We investigated TLR3 expression and sensitivity of human mesothelioma cell lines to the synthetic dsRNA Poly(I:C), alone or in combination with cisplatin, the gold standard chemotherapy in mesothelioma. Activation of TLR3 by Poly(I:C) induced apoptosis of 4/8 TLR3-positive cell lines but not of TLR3-negative cell lines. The combined cisplatin/Poly(I:C) treatment enhanced apoptosis of 3/4 Poly(I:C)-sensitive cell lines and overcame resistance to Poly(I:C) or cisplatin alone in 2/4 cell lines. Efficacy of the combined treatment relied on cisplatin-induced downregulation of c-FLIP, the main regulator of the extrinsic apoptotic pathway, leading to an enhanced caspase-8-mediated pathway. Of note, 6/6 primary cell samples isolated from patients with peritoneal mesothelioma expressed TLR3. Patient-derived cells were sensitive to Poly(I:C) alone while the combined cisplatin/Poly(I:C) treatment induced dramatic cell death. Our findings demonstrate that TLR3 targeting in combination with cisplatin presents an innovative therapeutic strategy in mesothelioma.

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.

Analyzing biological and molecular characteristics and genomic damage induced by exposure to asbestos

Asbestos is one of the most important occupational carcinogens. Currently, about 125 million people worldwide are exposed to asbestos in the workplace. According to global estimates, at least 107,000 people die each year from lung cancer, mesothelioma, and asbestosis as a result of occupational exposure to asbestos. The high pathogenicity of this material is currently known, being associated with the development of pulmonary diseases, of which lung cancer is the main cause of death due to exposure to this mineral. Pulmonary diseases related to asbestos are a common clinical problem and a major health concern worldwide. Extensive research has identified many important pathogenic mechanisms; however, the precise molecular mechanisms involved, and the generated genomic damage that lead to the development of these diseases, are not completely understood. The modes of action that underlie this type of disease seem to differ depending on the type of fiber, lung clearance, and genetics. This evidences the need to increase our knowledge about these effects on human health. This review focuses on the characteristics of asbestos and the cellular and genomic damage generated in humans via exposure.

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.

Splicing modulation as novel therapeutic strategy against diffuse malignant peritoneal mesothelioma

Introduction

Therapeutic options for diffuse malignant peritoneal mesothelioma (DMPM) are limited to surgery and locoregional chemotherapy. Despite improvements in survival rates, patients eventually succumb to disease progression. We investigated splicing deregulation both as molecular prognostic factor and potential novel target in DMPM, while we tested modulators of SF3b complex for antitumor activity.

Methods

Tissue-microarrays of 64 DMPM specimens were subjected to immunohistochemical assessment of SF3B1 expression and correlation to clinical outcome. Two primary cell cultures were used for gene expression profiling and in vitro screening of SF3b modulators. Drug-induced splicing alterations affecting downstream cellular pathways were detected through RNA sequencing. Ultimately, we established bioluminescent orthotopic mouse models to test the efficacy of splicing modulation in vivo.

Results

Spliceosomal genes are differentially upregulated in DMPM cells compared to normal tissues and high expression of SF3B1 correlated with poor clinical outcome in univariate and multivariate analysis. SF3b modulators (Pladienolide-B, E7107, Meayamycin-B) showed potent cytotoxic activity in vitro with IC50 values in the low nanomolar range. Differential splicing analysis of Pladienolide-B-treated cells revealed abundant alterations of transcripts involved in cell cycle, apoptosis and other oncogenic pathways. This was validated by RT-PCR and functional assays. E7107 demonstrated remarkable in vivo antitumor efficacy, with significant improvement of survival rates compared to vehicle-treated controls.

Conclusions

SF3B1 emerged as a novel potential prognostic factor in DMPM. Splicing modulators markedly impair cancer cell viability, resulting also in potent antitumor activity in vivo. Our data designate splicing as a promising therapeutic target in DMPM.

Molecular pathways and diagnosis in malignant mesothelioma: A review of the 14th International Conference of the International Mesothelioma Interest Group

The pathologist plays a central role in the diagnosis and management of malignant mesothelioma, including definitive tissue-based diagnosis in conjunction with clinical and radiographic data; diverse ancillary studies of diagnostic, prognostic, and predictive importance; and research efforts to better define the pathobiology of mesothelioma and develop novel clinical applications. The pivotal role of pathology in care of mesothelioma patients was on display at the recent meeting of the International Mesothelioma Interest Group (iMig) in Ottawa, Canada. This review summarizes the key findings of the "Molecular Pathways and Diagnosis in Malignant Mesothelioma" plenary session, including a large multi-institutional validation of a composite nuclear grading system for pleural mesothelioma, including incorporation of tumor necrosis as an additional independent prognostic factor; the correlation between nuclear grading in small biopsies and paired resection specimens in pleural mesothelioma; a multi-institutional study of important clinical and pathologic prognostic factors in peritoneal mesothelioma; the diagnostic role of HEG1 immunohistochemistry as a highly sensitive and specific marker of mesothelial lineage; the prevalence and diagnostic significance of MET protein overexpression in mesothelioma, as well as the correlation between MET protein overexpression and MET gene amplification; and the prognostic role of EZH2 protein overexpression in mesothelioma, together with data indicating an important pathogenic role for EZH2 in mesothelioma tumorigenesis. Special consideration is given to the convergence of diagnostic, prognostic, and predictive tools and their role in guiding highly personalized patient-centered management, and to the translation of novel research findings to practical techniques for routine pathologic practice.

Malignant peritoneal mesothelioma: clinical aspects, and therapeutic perspectives

Malignant peritoneal mesothelioma (MPM) is a rare disease with a wide clinical spectrum. It arises from the peritoneal lining and commonly presents with diffuse, extensive spread throughout the abdomen and, more rarely, metastatic spread beyond the abdominal cavity. Computed tomography, magnetic resonance imaging and positron-emission tomography are important diagnostic tools used for the preoperative staging of MPM. The definitive diagnosis is based on histopathological analysis, mainly via immunohistochemistry. In this regard, paired-box gene 8 negativity represents a useful diagnostic biomarker for differentiating MPM from ovarian carcinoma. In addition, BRCA1-associated protein-1 (BAP1) loss is specific to MPM and allows it to be distinguished from both benign mesothelial lesions and ovarian serous tumors. Cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) has become an increasingly important therapeutic approach, while systemic therapies are still being developed. Histology, Ki-67, completeness of cytoreduction, age, sex, and baseline thrombocytosis are commonly used to optimize patient selection for CRS with HIPEC. Additionally, it is well recognized that, compared to other subtypes, an epithelial morphology is associated with a favorable prognosis, whereas baseline thrombocytosis predicts an aggressive biologicalbehavior. Platelets and other immunologic cytokines have been evaluated as potential novel therapeutic targets. Epigenetic modifiers, including BAP1, SETD2 and DDX3X, are crucial in mesothelial tumorigenesis and provide opportunities for targeted treatment. Overexpression of the closely interacting phosphoinositide 3-kinase (PI3K) and the mammalian target of rapamycin (mTOR) pathways appears crucial in regulation of the malignant phenotype. The use of targeted therapies with PI3K-mTOR-based inhibitors requires further clinical assessment as a novel approach.

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.

Dysregulated Expression of the MicroRNA miR-137 and Its Target YBX1 Contribute to the Invasive Characteristics of Malignant Pleural Mesothelioma

INTRODUCTION

Malignant pleural mesothelioma (MPM) is an aggressive malignancy linked to asbestos exposure. On a genomic level, MPM is characterized by frequent chromosomal deletions of tumor suppressors, including microRNAs. MiR-137 plays a tumor suppressor role in other cancers, so the aim of this study was to characterize it and its target Y-box binding protein 1 (YBX1) in MPM.

METHODS

Expression, methylation, and copy number status of miR-137 and its host gene MIR137HG were assessed by polymerase chain reaction. Luciferase reporter assays confirmed a direct interaction between miR-137 and Y-box binding protein 1 gene (YBX1). Cells were transfected with a miR-137 inhibitor, miR-137 mimic, and/or YBX1 small interfering RNA, and growth, colony formation, migration and invasion assays were conducted.

RESULTS

MiR-137 expression varied among MPM cell lines and tissue specimens, which was associated with copy number variation and promoter hypermethylation. High miR-137 expression was linked to poor patient survival. The miR-137 inhibitor did not affect target levels or growth, but interestingly, it increased miR-137 levels by means of mimic transfection suppressed growth, migration, and invasion, which was linked to direct YBX1 downregulation. YBX1 was overexpressed in MPM cell lines and inversely correlated with miR-137. RNA interference-mediated YBX1 knockdown significantly reduced cell growth, migration, and invasion.

CONCLUSIONS

MiR-137 can exhibit a tumor-suppressive function in MPM by targeting YBX1. YBX1 knockdown significantly reduces tumor growth, migration, and invasion of MPM cells. Therefore, YBX1 represents a potential target for novel MPM treatment strategies.

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).

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.

The RENAPE observational registry: rationale and framework of the rare peritoneal tumors French patient registry

Background

Rare peritoneal cancers represent complex clinical situations requiring a specific and multidisciplinary management. Because of their rarity, lack of awareness and knowledge often leads to diagnostic delays and misdiagnosis. And patients are not systematically referred to expert centers as they should be. Clinicians and researchers also face unique challenges with these rare cancers, because it is hard to conduct adequately powered, controlled trials in such small patient population. This is how an observational patient registry constitutes a key instrument for the development of epidemiological and clinical research in the field of these rare cancers. It is the appropriate tool to pool scarce data for epidemiological research and to assess the impact of diagnostic and therapeutic strategies. We aimed to provide the outlines and the framework of the RENAPE observational registry and share our experience in the establishment of a national patient registry.

Results

The RENAPE observational registry has been launched in 2010 thanks to institutional supports. It concerns only patients with a histological diagnosis confirming a peritoneal surface malignancy. A web secured clinical database has been implemented based on data management procedures according to the principles of international recommendations and regulatory statements. A virtual tumor bank is linked in order to the conduct translational studies. Specialized working groups have been established to continuously upgrade and evolve the common clinical and histological data elements following the last classifications and clinical practices. They contribute also to standardize clinical assessment and homogenize practices.

Conclusions

The RENAPE Registry may improve awareness and understanding of the rare peritoneal tumors into the incidence, prevalence, recurrence, survival and mortality rates, as well as treatment practices thereby enabling therapeutic intervention to be evaluated and ultimately optimized.

Trial registration

ClinicalTrials.gov Identifier: NCT02834169

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.