Malignant mesothelioma: New insights into a rare disease

LAG3 is an independent prognostic biomarker and potential target for immune checkpoint inhibitors in malignant pleural mesothelioma: a retrospective study

BACKGROUND

Lymphocyte-activation gene 3 (LAG3) is an immune checkpoint receptor; novel LAG3 immune checkpoint inhibitors (ICIs) exhibit therapeutic activity in melanoma. The role of LAG3and ICIs of LAG3 are unknown in malignant pleural mesothelioma (MPM). This study aimed to uncover the prognostic landscape of LAG3 in multiple cancers and investigate the potential of using LAG3 as an ICIs target in patients with MPM.

METHODS

We used The Cancer Genome Atlas (TCGA) cohort for assessing mRNA expression and our cohort for immunohistochemical expression. TCGA cohort were analyzed using the Wilcoxon rank-sum test to compare mRNA expression between normal and tumor tissues in multiple cancers. We used 86 MPM cases from TCGA and 38 MPM cases from our cohort to analyze the expression of LAG3 in tumor-infiltrating lymphocytes. The mean LAG3 mRNA expression was set as the cut-off and samples were classified as positive/negative for immunohistochemical expression. Overall survival (OS) of patients with MPM was determined using the Kaplan-Meier method based on LAG3 mRNA and immunohistochemical expression. OS analysis was performed using the multivariate Cox proportional hazards model. The correlation of LAG3 expression and mRNA expression of tumor immune infiltration cells (TIICs) gene markers were estimated using Spearman correlation. To identify factors affecting the correlation of LAG3 mRNA expression, a multivariate linear regression model was performed.

RESULTS

LAG3 mRNA was associated with prognosis in multiple cancers. Elevated LAG3 mRNA expression was correlated with a better prognosis in MPM. LAG3 expression was detected immunohistochemically in the membrane of infiltrating lymphocytes in MPM. LAG3 immunohistochemical expression was correlated with a better prognosis in MPM. The multivariate Cox proportional hazards model revealed that elevated LAG3 immunohistochemical expression indicated a better prognosis. In addition, LAG3 mRNA expression was correlated with the expression of various gene markers of TIICs, the most relevant to programmed cell death 1 (PD-1) with the multivariate linear regression model in MPM.

CONCLUSIONS

LAG3 expression was correlated with prognosis in multiple cancers, particularly MPM; LAG3 is an independent prognostic biomarker of MPM. LAG3 regulates cancer immunity and is a potential target for ICIs therapy. PD-1 and LAG3 inhibitors may contribute to a better prognosis in MPM.

TRIAL REGISTRATION

This study was registered with UMIN000049240 (registration day: August 19, 2022) and approved by the Institutional Review Board (approval date: August 22, 2022; approval number: 2022-0048) at Tokyo Women's Medical University.

Identification of genes and pathways involved in malignant pleural mesothelioma using bioinformatics methods

Background

Malignant pleural mesothelioma (MPM) is a rare tumor in the pleura. This study was carried out to identify key genes and pathways that may be involved in MPM.

Methods

Microarray datasets GSE51024 and GSE2549 were analyzed for differentially expressed genes (DEGs) between normal and MPM tissues. The identified DEGs were subjected to functional analyses using bioinformatics tools.

Results

A total of 276 DEGs were identified, consisting of 187 downregulated and 79 upregulated genes. Gene ontology and Kyoto encyclopedia of genes and genomes pathway enrichment analysis indicated that the DEGs were enriched in extracellular structure organization, extracellular matrix, and ECM−receptor interaction. Due to high degree of connectivity among 24 hub genes, EZH2 and HMMR are likely to play roles in the carcinogenesis and progression of MPM. The two genes were found over-expressed in MPM tissues. Patients with elevated EZH2 and HMMR expressions had poor overall survival.

Conclusions

EZH2 and HMMR are identified to be the hub genes for MPM and they may be further characterized to better understand the molecular mechanisms underlying the carcinogenesis of MPM.

The influence of genetic variability in IL1B and MIR146A on the risk of pleural plaques and malignant mesothelioma

Background

Asbestos exposure is associated with the development of pleural plaques as well as malignant mesothelioma (MM). Asbestos fibres activate macrophages, leading to the release of inflammatory mediators including interleukin 1 beta (IL-1β). The expression of IL-1β may be influenced by genetic variability of IL1B gene or regulatory microRNAs (miRNAs). This study investigated the effect of polymorphisms in IL1B and MIR146A genes on the risk of developing pleural plaques and MM.

Subjects and methods

In total, 394 patients with pleural plaques, 277 patients with MM, and 175 healthy control subjects were genotyped for IL1B and MIR146A polymorphisms. Logistic regression was used in statistical analysis.

Results

We found no association between MIR146A and IL1B genotypes, and the risk of pleural plaques. MIR146A rs2910164 was significantly associated with a decreased risk of MM (OR = 0.31, 95% CI = 0.13–0.73, p = 0.008). Carriers of two polymorphic alleles had a lower risk of developing MM, even after adjustment for gender and age (OR = 0.34, 95% CI = 0.14–0.85, p = 0.020). Among patients with known asbestos exposure, carriers of at least one polymorphic IL1B rs1143623 allele also had a lower risk of MM in multivariable analysis (OR = 0.50, 95% CI = 0.28–0.92, p = 0.025). The interaction between IL1B rs1143623 and IL1B rs1071676 was significantly associated with an increased risk of MM (p = 0.050).

Conclusions

Our findings suggest that genetic variability of inflammatory mediator IL-1β could contribute to the risk of developing MM, but not pleural plaques.

Analysis of angiogenic and stromal biomarkers in a large malignant mesothelioma cohort

BACKGROUND

Malignant mesothelioma (MM) is an aggressive malignancy of the pleura and other mesothelial membranes. Agents targeting vascular endothelial growth factor (VEGF) such as bevacizumab; and multi-kinase inhibitors such as nintedanib [angiokinase inhibitor of VEGF, platelet-derived growth factor (PDGF) receptor and fibroblast growth factor receptor (FGFR)] have recently demonstrated efficacy in MM.

METHODS

Tissue microarrays (TMAs) were created from formalin-fixed, paraffin-embedded tissue samples obtained from 326 patients with MM who were treated surgically. PDGF-CC, FGFR-1, VEGF and CD31 expression were analysed by immunohistochemical (IHC) staining. The H-score method assigned a score of 0-300 to each sample, based on the percentage of cells stained at different intensities. CD31 was evaluated via Chalkley's method to evaluate microvessel density. We evaluated the association between expression of the biomarkers, clinicopathological factors and outcomes, in patients with MM.

RESULTS

CD31 high (≥5) was seen in only 31/302 (10.3%) irrespective of histology. PDGF-CC high (≥150) was seen in 203 /310 (65%) of all samples. VEGF high (≥80) was seen in 219/322 (68%) of all MM with 143/209 (68%) of epithelioid histology. FGFR-1 high (≥40) was seen in 127/310 (41%) of all MM. There was no association of VEGF and FGFR-1 IHC with survival nor differences between histological subtypes. There was a non-significant trend towards poorer survival in epithelioid tumours with increased PDGF-CC expression (OS 18.5 vs 13.2 months; HR 0.7928; 95% CI 0.5958 to 1.055, P = 0.1110). High CD31 score was associated with significantly poorer survival (OS 12 vs 8.6 months; HR 0.48; 95% CI 0.2873 to 0.7941, P = 0.0044). Of the 31 patients with high CD31 scores; 23/31 (74%) were also high for PDGF-CC and 20/31 (64%) with high VEGF scores. CD31 was found to be an independent prognostic factor in multivariate analysis (HR 1.540; 95% CI 1.018 to 2.330; p = 0.041).

CONCLUSIONS

High CD31 was an independent poor prognostic factor and high PDGF-CC expression was associated with poor survival in MM. Abrogating these pathways may have prognostic implications.

The influence of genetic variability of DNA repair mechanisms on the risk of malignant mesothelioma

Background Malignant mesothelioma (MM) is a rare aggressive tumour of mesothelium caused by asbestos exposure. It has been suggested that the genetic variability of proteins involved in DNA repair mechanisms affects the risk of MM. This study investigated the influence of functional polymorphisms in ERCC1 and XRCC1 genes, the interactions between these polymorphisms as well as the interactions between these polymorphisms and asbestos exposure on MM risk. Patients and methods In total, 237 cases with MM and 193 controls with no asbestos-related disease were genotyped for ERCC1 and XRCC1 polymorphisms. Results ERCC1 rs3212986 polymorphism was significantly associated with a decreased risk of MM (odds ratio [OR] = 0.61; 95% confidence interval [CI] = 0.41-0.91; p = 0.014). No associations were observed between other genetic polymorphisms and MM risk. Interactions between polymorphisms did not significantly influence MM risk. Interaction between ERCC1 rs11615 and asbestos exposure significantly influenced MM risk (OR = 3.61; 95% CI = 1.12-11.66; p = 0.032). Carriers of polymorphic ERCC1 rs11615 allele who were exposed to low level of asbestos had a decreased risk of MM (OR = 0.40; 95% CI = 0.19-0.84; p = 0.016). Interactions between other polymorphisms and asbestos exposure did not significantly influence MM risk. Conclusions Our findings suggest that the genetic variability of DNA repair mechanisms could contribute to the risk of developing MM.

Diagnosis of mesothelioma with deep learning

Malignant mesothelioma (MM) is a rare but aggressive cancer. The definitive diagnosis of MM is critical for effective treatment and has important medicolegal significance. However, the definitive diagnosis of MM is challenging due to its composite epithelial/mesenchymal pattern. The aim of the current study was to develop a deep learning method to automatically diagnose MM. A retrospective analysis of 324 participants with or without MM was performed. Significant features were selected using a genetic algorithm (GA) or a ReliefF algorithm performed in MATLAB software. Subsequently, the current study constructed and trained several models based on a backpropagation (BP) algorithm, extreme learning machine algorithm and stacked sparse autoencoder (SSAE) to diagnose MM. A confusion matrix, F-measure and a receiver operating characteristic (ROC) curve were used to evaluate the performance of each model. A total of 34 potential variables were analyzed, while the GA and ReliefF algorithms selected 19 and 5 effective features, respectively. The selected features were used as the inputs of the three models. SSAE and GA+SSAE demonstrated the highest performance in terms of classification accuracy, specificity, F-measure and the area under the ROC curve. Overall, the GA+SSAE model was the preferred model since it required a shorter CPU time and fewer variables. Therefore, the SSAE with GA feature selection was selected as the most accurate model for the diagnosis of MM. The deep learning methods developed based on the GA+SSAE model may assist physicians with the diagnosis of MM.

BAMLET kills chemotherapy-resistant mesothelioma cells, holding oleic acid in an activated cytotoxic state

Malignant pleural mesothelioma is an aggressive cancer with poor prognosis. Here we have investigated in vitro efficacy of BAMLET and BLAGLET complexes (anti-cancer complexes consisting of oleic acid and bovine α-lactalbumin or β-lactoglobulin respectively) in killing mesothelioma cells, determined BAMLET and BLAGLET structures, and investigated possible biological mechanisms. We performed cell viability assays on 16 mesothelioma cell lines. BAMLET and BLAGLET having increasing oleic acid content inhibited human and rat mesothelioma cell line proliferation at decreasing doses. Most of the non-cancer primary human fibroblasts were more resistant to BAMLET than were human mesothelioma cells. BAMLET showed similar cytotoxicity to cisplatin-resistant, pemetrexed-resistant, vinorelbine-resistant, and parental rat mesothelioma cells, indicating the BAMLET anti-cancer mechanism may be different to drugs currently used to treat mesothelioma. Cisplatin, pemetrexed, gemcitabine, vinorelbine, and BAMLET, did not demonstrate a therapeutic window for mesothelioma compared with immortalised non-cancer mesothelial cells. We demonstrated by quantitative PCR that ATP synthase is downregulated in mesothelioma cells in response to regular dosing with BAMLET. We sought structural insight for BAMLET and BLAGLET activity by performing small angle X-ray scattering, circular dichroism, and scanning electron microscopy. Our results indicate the structural mechanism by which BAMLET and BLAGLET achieve increased cytotoxicity by holding increasing amounts of oleic acid in an active cytotoxic state encapsulated in increasingly unfolded protein. Our structural studies revealed similarity in the molecular structure of the protein components of these two complexes and in their encapsulation of the fatty acid, and differences in the microscopic structure and structural stability. BAMLET forms rounded aggregates and BLAGLET forms long fibre-like aggregates whose aggregation is more stable than that of BAMLET due to intermolecular disulphide bonds. The results reported here indicate that BAMLET and BLAGLET may be effective second-line treatment options for mesothelioma.

Trophoblast Glycoprotein is Associated With a Favorable Outcome for Mesothelioma and a Target for Antibody Drug Conjugates

INTRODUCTION

The prognosis for patients with mesothelioma is poor, which prompts the need for the development of better treatment options. Antibody drug conjugates (ADCs) are gaining interest as a therapeutic strategy in mesothelioma. Trophoblast glycoprotein (5T4) is an oncofetal protein overexpressed in mesothelioma with low expression in normal tissue and therefore a good candidate for ADC treatment. Here, we evaluated and manipulated 5T4 as a suitable antigen for ADC targeted therapy in patients with mesothelioma.

METHODS

Expression of the 5T4 antigen is evaluated in (primary) mesothelioma cell lines and biopsy specimens, and correlated with clinical outcome. Internalization was assessed in 5T4 expressing cells. The cytotoxicity of three different 5T4-targeting ADCs was tested on (primary) mesothelioma cells.

RESULTS

5T4 was expressed in 10 of 12 (primary) cell lines. Most biopsy specimens stained positive for the 5T4 antigen, with marked differences in staining intensity and percentage of positive cells. High expression correlated with long progression-free survival. Both free antibody and ADCs targeting 5T4 were internalized and entered lysosomal compartments. Cytotoxicity experiments showed that cell lines with a high expression for 5T4 were sensitive to two of three ADCs. Lack of efficacy for the third ADC could be restored by neutralizing lysosomal compartments with chloroquine.

CONCLUSIONS

The 5T4 antigen is expressed in mesothelioma and 5T4-based ADCs are internalized in lysosomes. Two of three ADCs were capable of killing the mesothelioma cells; the third ADC required additional lysosomal neutralization for its effect. 5T4-based ADCs would be a selective strategy for the treatment of mesothelioma.

Current status of malignant mesothelioma with liver involvement in China: A brief report and review of the literature

Primary and secondary intrahepatic malignant mesothelioma (PIHMM & SIHMM) caused by Peritoneal mesothelioma (PM) are extremely rare tumors and their clinicopathological characteristics remain unclear. The current study presented a case of a 63-year-old female with PIHMM and a literature review of Chinese case reports of SIHMM and PIHMM was performed. The patient received curative left hemihepatectomy because of a 5.5 × 5.0 × 4.0 cm mass occupying the II, III and the lateral portion of the IV segments and meanwhile tightly infiltrating the diaphragm (yellow arrow) was also observed. The pathological diagnosis was epithelial type PIHMM. Immunohistochemistry revealed that the tumor was positive for Calretinin, CK5/6, WT-1 and D2-40(N). The literature review included 11 studies and 6 case reports with a total of 293 PM patients accompanied with 31 SIHMM cases and then 3 case reports of PIHMM. SIHMM and PIHMM are extremely rare, easy to misdiagnose malignant tumors. Immunohistochemistry should be performed strictly in accordance with guidelines, which is crucial for pathological diagnosis. Comprehensive treatment of surgery combined with chemotherapy are mainstream methods for SIHMM and PIHMM. Also, exact survival data should be carefully explored so that objective evaluation of the efficacy of the treatment could be achieved.

Isolated thoracic perfusion with chemofiltration for progressive malignant pleural mesothelioma

Introduction

Therapy of malignant pleural mesothelioma and especially the adequate role of surgery in this context remain the subject of controversial discussions. Radical surgery in particular, which is associated with substantial morbidity, failed to translate into a definite survival advantage. We report on interim results of an ongoing Phase II study of regional chemotherapy in terms of isolated thoracic perfusion with chemofiltration (ITP-F).

Patients and methods

Twenty-eight patients (25 male, 3 female, mean age 63.4 years) with advanced pleural mesothelioma were included in this study. Isolation of the chest was achieved by insertion of a venous and arterial stop-flow balloon catheter via a femoral access. The aorta and inferior vena cava were blocked at the level of the diaphragm and the upper arms were blocked by pneumatic cuffs. Chemotherapy, consisting of 60 mg/m² cisplatin and 15 mg/m² mitoxantrone, was administered directly into the aorta. The isolated circuit was maintained for 15 minutes followed bŷ45 minutes of chemofiltration with a hemoprocessor until 5 L of filtrate were reached. The endpoints of the study were overall survival and quality of life (QoL).

Results

Out of 28 patients enrolled in the study, 5 had prior surgeries, 10 patients had systemic chemotherapy, and 5 patients additional irradiation. In all patients in restaging, clinical progress was noted. In all, 162 cycles were administered. Due to chemofiltration, toxicity was within tolerable limits, revealing World Health Organization grade I leucopenia and thrombocytopenia in 9 patients and mucositis grade I in 6 patients. The major surgical complication was inguinal lymphatic fistula in 40% of the cases. Gastrointestinal toxicity and/or neurotoxicity were never observed. One-year survival was 49%, 2-year and 3-year survival was 31%, and 5-year survival was 18%. Median overall survival was 12 months and progression-free survival 9 months.

Conclusion

ITP-F for patients with advanced pleural mesothelioma, progressive after standard therapies, is an effective and well-tolerated treatment modality, offering comparably long survival data at a good QoL.

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.

The Potential Protective Effects of Polyphenols in Asbestos-Mediated Inflammation and Carcinogenesis of Mesothelium

Malignant Mesothelioma (MM) is a tumor of the serous membranes linked to exposure to asbestos. A chronic inflammatory response orchestrated by mesothelial cells contributes to the development and progression of MM. The evidence that: (a) multiple signaling pathways are aberrantly activated in MM cells; (b) asbestos mediated-chronic inflammation has a key role in MM carcinogenesis; (c) the deregulation of the immune system might favor the development of MM; and (d) a drug might have a better efficacy when injected into a serous cavity thus bypassing biotransformation and reaching an effective dose has prompted investigations to evaluate the effects of polyphenols for the therapy and prevention of MM. Dietary polyphenols are able to inhibit cancer cell growth by targeting multiple signaling pathways, reducing inflammation, and modulating immune response. The ability of polyphenols to modulate the production of pro-inflammatory molecules by targeting signaling pathways or ROS might represent a key mechanism to prevent and/or to contrast the development of MM. In this review, we will report the current knowledge on the ability of polyphenols to modulate the immune system and production of mediators of inflammation, thus revealing an important tool in preventing and/or counteracting the growth of MM.

Orotate phosphoribosyltransferase is overexpressed in malignant pleural mesothelioma: Dramatically responds one case in high OPRT expression

Objective: Malignant pleural mesothelioma (MPM) is a rare and aggressive, treatment-resistant cancer. Pemetrexed, an inhibitor of thymidylate synthase (TS), is used worldwide for MPM as a first-line chemotherapy regimen. However, there is little consensus for a second-line chemotherapy. S-1, a highly effective dihydropyrimidine dehydrogenase (DPD)-inhibitory fluoropyrimidine, mainly acts via a TS inhibitory mechanism similar to pemetrexed. Orotate phosphoribosyltransferase (OPRT) is a key enzyme related to the first step activation of 5-fluorouracil (5-FU) for inhibiting RNA synthesis. We investigated 5-FU related-metabolism proteins, especially focusing on OPRT expression, in MPM Methods and Patients: Fifteen MPM patients who were diagnosed between July 2004 and December 2013 were enrolled. We examined the protein levels of 5-FU metabolism-related enzymes (TS, DPD, OPRT, and thymidine phosphorylase [TP]) in 14 cases Results: High TS, DPD, OPRT, and TP expressions were seen in 28.6%, 71.4%, 85.7%, and 35.7% of patients, respectively. We found that OPRT expression was extremely high in MPM tissue. We experienced one remarkable case of highly effective S-1 combined therapy for pemetrexed refractory MPM. This case also showed high OPRT protein expression Conclusion: The present study suggests that OPRT expression is high in MPM tumors. Although pemetrexed is mainly used for MPM chemotherapy as a TS inhibitor, S-1 has potential as an anticancer drug not only as a TS inhibitor but also inhibiting RNA synthesis through the OPRT pathway. This is the first report investigating OPRT protein expressions in MPM.

Pemetrexed Maintenance Therapy Following Bevacizumab-Containing First-Line Chemotherapy in Advanced Malignant Pleural Mesothelioma: A Case Report and Literatures Review

Malignant pleural mesothelioma (MPM) is a lethal disease with poor prognosis. The combination of cisplatin and pemetrexed has been confirmed as the standard of care for nonoperable MPM. Data have shown that the adoption of pemetrexed maintenance therapy (PMT) following first-line treatment appears extremely promising.We describe a 57-year-old man diagnosed as advanced MPM. We treated this patient with PMT after first-line cisplatin-based bevacizumab-containing chemotherapy and residual tumor disappeared after 6 course of PMT. A perfect response and a long progression-free survival (PFS) were reached with tumor mass disappearing and 14 months duration of PFS.This case suggests that adding bevacizumab to standard first-line chemotherapy is feasible and that PMT could be promising and useful for treating advanced MPM. We further entail a review of the literature on the first-line treatment, continuation maintenance therapy, switch maintenance therapy, and second-line treatment of patients with advanced MPM.

Malignant Peritoneum Mesothelioma with Hepatic Involvement: A Single Institution Experience in 5 Patients and Review of the Literature

Malignant peritoneal mesothelioma with invasion of the liver is an invariably fatal disease. We aimed to clarify the characteristics of malignant peritoneal mesothelioma cases with liver involvement. The clinical presentation, computed tomography images, and immunohistochemical and histopathological features of 5 patients with malignant peritoneal mesothelioma and liver involvement were evaluated. The diagnosis was established by imaging and immune profiles of the tumours. A review of 8 cases with primary or invading malignant mesothelioma in liver is presented. All 5 mesothelioma cases were asbestos-related. CT images of malignant peritoneal mesothelioma with the liver involvement typically showed that the lesion grew inside the liver along the capsule and was possibly accompanied by capsule breakthrough and extrahepatic infiltration. The tumours exhibited a common epithelioid appearance in all 5 patients and most cases revealed positive Cal, CK, and MC with negative CEA and HeP. Different from our findings, the review of literature revealed that most malignant mesothelioma of liver was due to primary intrahepatic malignant mesothelioma. Finally, we concluded that the diagnosis of malignant peritoneal mesothelioma cases with liver invasion is reliably achieved by the history of asbestos exposure, the characteristic CT imaging, and immune profiles of the tumours.

Response evaluation in mesothelioma: Beyond RECIST

Malignant pleural mesothelioma (MPM) typically demonstrates a non-spherical growth pattern, so it is often difficult to accurately categorize change in tumour burden using size-based tumour response criteria (e.g., WHO (World Health Organisation), RECIST (Response Evaluation Criteria in Solid Tumours) and modified RECIST). Functional imaging techniques are applied to derive quantitative measurements of tumours, which reflect particular aspects of the tumour pathophysiology. By quantifying how these measurements change with treatment, it is possible to observe treatment effects. In this review, we survey the existing roles of CT and MRI for the management of MPM, including the currently applied size measurement criteria for the assessment of treatment response. New functional imaging techniques, such as positron emission tomography (PET), diffusion-weighted MRI (DWI) and dynamic contrast-enhanced MRI (DCE-MRI) that may potentially improve the assessment of treatment response will be highlighted and discussed.

Zoledronic acid overcomes chemoresistance and immunosuppression of malignant mesothelioma

The human malignant mesothelioma (HMM) is characterized by a chemoresistant and immunosuppressive phenotype. An effective strategy to restore chemosensitivity and immune reactivity against HMM is lacking. We investigated whether the use of zoledronic acid is an effective chemo-immunosensitizing strategy.

We compared primary HMM samples with non-transformed mesothelial cells.

HMM cells had higher rate of cholesterol and isoprenoid synthesis, constitutive activation of Ras/extracellular signal-regulated kinase1/2 (ERK1/2)/hypoxia inducible factor-1α (HIF-1α) pathway and up-regulation of the drug efflux transporter P-glycoprotein (Pgp). By decreasing the isoprenoid supply, zoledronic acid down-regulated the Ras/ERK1/2/HIF-1α/Pgp axis and chemosensitized the HMM cells to Pgp substrates. The HMM cells also produced higher amounts of kynurenine, decreased the proliferation of T-lymphocytes and expanded the number of T-regulatory (Treg) cells. Kynurenine synthesis was due to the transcription of the indoleamine 1,2 dioxygenase (IDO) enzyme, consequent to the activation of the signal transducer and activator of transcription-3 (STAT3). By reducing the activity of the Ras/ERK1/2/STAT3/IDO axis, zoledronic acid lowered the kyurenine synthesis and the expansion of Treg cells, and increased the proliferation of T-lymphocytes.

Thanks to its ability to decrease Ras/ERK1/2 activity, which is responsible for both Pgp-mediated chemoresistance and IDO-mediated immunosuppression, zoledronic acid is an effective chemo-immunosensitizing agent in HMM cells.

Cisplatin in combination with Phenethyl Isothiocyanate (PEITC), a potential new therapeutic strategy for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a very aggressive form of cancer with a poor diagnosis and prognosis. The first line treatment for MPM is a combination of cisplatin and Pemetrexed, which displayed limited efficacy and severe side effects. The naturally occurring compound phenethyl isothiocyanate (PEITC) previously showed interesting anti-tumor properties on several cancer cell lines. We thus aim at evaluating PEITC used alone or in combination with cisplatin in order to improve MPM treatment.

Nine MPM cell lines and primary mesothelial cells (PMC), co-cultured or not with M2 macrophages present in MPM microenvironment, were used to assess PEITC and cisplatin anti-tumor properties. Compounds were used alone or in combination.

Both PEITC and cisplatin were cytotoxic on MPM cells in a dose dependent manner. We herein showed that PEITC-induced cytotoxicity was due to the generation of reactive oxygen species. Moreover, we showed that cisplatin-PEITC combination allowed the potentialization of both compounds' cytotoxic effects and prevented the emergence of resistant MPM cells. Interestingly, PMC were not sensitive to the combination. Finally, we showed that M2 macrophages did not alter the anti-tumor properties of the combination. Cisplatin-PEITC combination thus represents a promising strategy to induce a selective toxicity towards malignant cells.

Combinatorial anti-angiogenic gene therapy in a human malignant mesothelioma model

Anti-angiogenic gene therapy represents a promising strategy for cancer; however, it has rarely been tested in malignant mesothelioma, a highly aggressive tumor associated with asbestos with poor prognosis. In the present study, we investigated whether anti-angiogenic factors such as angiostatin, endostatin and the soluble form of vascular endothelial growth factor receptor 2 (sFlk1) were able to inhibit endothelial cell proliferation via lentivirus-mediated gene transfer into malignant mesothelioma cells in culture. We also assessed whether a dual-agent strategy had greater therapeutic benefit. Human malignant pleural mesothelioma MSTO-211H cells were transduced using lentiviral vectors that individually expressed angiostatin, endostatin and sFlk1 and linked to enhanced green fluorescent protein (EGFP) marker gene expression via an internal ribosome entry site. The lentivirus expressing EGFP alone was used as a control. The resultant cells designated as MSTO-A, MSTO-E, MSTO-F and MSTO-C were confirmed by western blot analysis and fluorescence microscopy to stably express the corresponding proteins. No differences were observed in the in vitro growth rates between any of these cells. However, co-culture of MSTO-A, MSTO-E and MSTO-F showed significant suppression of human umbilical endothelial cell growth in vitro compared with that of MSTO-C. Furthermore, a combination of any two among MSTO-A, MSTO-E and MSTO-F significantly enhanced efficacy. These results suggest that combinatorial anti-angiogenic gene therapy targeting different pathways of endothelial growth factor signaling has the potential for greater therapeutic efficacy than that of a single-agent regimen.

Surgical cytoreduction restores the antitumor efficacy of a Listeria monocytogenes vaccine in malignant pleural mesothelioma

Recent studies suggest that immunotherapy may offer a promising treatment strategy for early-stage malignant pleural mesothelioma (MPM), but advanced tumor burden may limit the efficacy of immunotherapy. Therefore, we hypothesized that surgical cytoreduction could restore the efficacy of vaccine-based immunotherapy for MPM. We developed a murine model of MPM through transduction of a mesothelioma cell line with mesothelin. We used this model to evaluate the efficacy of a Listeria monocytogenes vaccine expressing mesothelin. Tumor growth was significantly inhibited at four weeks in animals vaccinated two weeks prior to tumor cell inoculation as compared to those given an empty vector control (1371 ± 420 mm(3) versus 405 ± 139 mm(3); p < 0.01). Mice vaccinated one week prior to tumor challenge also displayed significant reduction in tumor volume (1227 ± 406 mm(3) versus 309 ± 173 mm(3); p < 0.01). The vaccine had no effect when administered concurrently with tumor challenge, or after tumors were established. Flow cytometry showed reduced mesothelin expression in large tumors, as well as tumor-associated immunosuppression due to increased myeloid derived suppressor cells (MDSCs). These factors may have limited vaccine efficacy for advanced disease. Surgical cytoreduction of established tumors restored the antitumor potency of the therapeutic vaccine, with significantly reduced tumor burden at post-operative day 18 (397 ± 103 mm(3) versus 1047 ± 258 mm(3); p < 0.01). We found that surgery reduced MDSCs to levels comparable to those in tumor-naïve mice. This study demonstrates that cytoreduction surgery restores the efficacy of cancer vaccines for MPM by reducing tumor-related immunosuppression that impairs immunotherapy.

Agonist activation of estrogen receptor beta (ERβ) sensitizes malignant pleural mesothelioma cells to cisplatin cytotoxicity

Background

Estrogen receptor (ER) β acts as a tumor suppressor in malignant mesotheliomas.

Methods

Here we explored the anti-proliferative and anti-tumorigenic efficacy of the selective ERβ agonist, KB9520, in human mesothelioma cell lines in vitro and in a mesothelioma mouse model in vivo.

Results

KB9520 showed significant anti-proliferative effect in ERβ positive human malignant pleural mesothelioma cells in vitro. Selective activation of ERβ with KB9520 sensitized the cells to treatment with cisplatin, resulting in enhanced growth inhibition and increased apoptosis. Furthermore, in CD1 nude mice mesothelioma tumor growth was significantly inhibited when KB9520 was added on top of the standard of care chemo combination cisplatin/pemetrexed, as compared to the cisplatin/pemetrexed alone group. Importantly, KB9520 exerted a protective effect to cisplatin toxicity in the non-malignant mesothelium derived MET5A cells.

Conclusions

Together, the data presented suggest that selective targeting of ERβ may be an efficacious stand-alone treatment option and/or become an important add-on to existing malignant mesothelioma therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-227) contains supplementary material, which is available to authorized users.

Systemic treatment of malignant pleural mesothelioma: new agents in clinical trials raise hope of relevant improvements

PURPOSE OF REVIEW

Malignant pleural mesothelioma (MPM) is a rare malignancy with limited therapeutic options and its incidence is still increasing in both Europe and the developing nations. Prognosis of MPM patients is poor even if the median survival durations have been slightly improved after the introduction of the up-to-date chemotherapy combination with pemetrexed and cisplatin. There is a continuing unmet need to develop better systemic treatment for this disease, but the rarity of the tumor type creates formidable challenges in clinical trial research.

RECENT FINDINGS

Better understanding of the molecular machinery of MPM leads to the design and synthesis of novel compounds targeted against pathways identified as crucial for MPM cell proliferation and metastasis. Most efforts aim at improving standard first-line therapy, or developing effective second-line treatments. Several classes of drugs are currently being explored either in combination with cisplatin and pemetrexed or as single agent for relapsed or progressive MPM.

SUMMARY

This review focuses on several ongoing or recently completed clinical trials investigating novel, promising agents as first-line or second-line therapy for advanced MPM.

Current issues in malignant pleural mesothelioma evaluation and management

Malignant pleural mesothelioma (MPM) is an uncommon disease most often associated with occupational asbestos exposure and is steadily increasing in worldwide incidence. Patients typically present at an older age, with advanced clinical stage and other medical comorbidities, making management quite challenging. Despite great efforts, the prognosis of MPM remains poor, especially at progression after initial treatment. Macroscopic complete resection of MPM can be achieved through extrapleural pneumonectomy (EPP) or extended (ie, radical) pleurectomy (e-P/D) in selected patients and can result in prolonged survival when incorporated into a multimodality approach. Given the morbidity associated with surgical resection of MPM, optimizing identification of appropriate patients is essential. Unfortunately, most patients are not candidates for EPP or e-P/D due to advanced stage, age, and/or medical comorbidity. Pemetrexed and platinum combination chemotherapy has become the cornerstone of therapy for patients with unresectable disease because the combination is associated with improved survival and quality of life in treated patients. However, MPM eventually becomes resistant to initial therapy, and benefit to further lines of therapy has not been substantiated in randomized clinical trials. Translational research has provided exciting insights into tumorigenesis, biomarkers, and immune response in MPM, leading to the development of multiple novel therapeutic agents that are currently in clinical trials. These advances hold the promise of a new era in the treatment of MPM and suggest that this disease will not be left behind in the war on cancer.

Establishing a panel of chemo-resistant mesothelioma models for investigating chemo-resistance and identifying new treatments for mesothelioma

Mesothelioma is inherently chemo-resistant with only 50% of patients responding to the standard of care treatments, and consequently it has a very grim prognosis. The aim of this study was to establish a panel of chemo-resistant mesothelioma models with clinically relevant levels of resistance as tools for investigating chemo-resistance and identifying new treatments for mesothelioma. Chemo-resistant cell lines were established in vitro and characterized in vivo using syngeneic Fischer rats. Tumors derived from all chemo-resistant cell lines were immunohistochemically classified as mesothelioma. Homozygous deletion of p16^INK4A/p14^ARF and increased expression of several ATP-binding cassette transporters were demonstrated, consistent with findings in human mesothelioma. Further, the acquisition of chemo-resistance in vitro resulted in changes to tumor morphology and overall survival. In conclusion, these models display many features corresponding with the human disease, and provide the first series of matched parental and chemo-resistant models for in vitro and in vivo mesothelioma studies.

STAT6 siRNA matrix-loaded gelatin nanocarriers: formulation, characterization, and ex vivo proof of concept using adenocarcinoma cells

The clinical utility of siRNA therapy has been hampered due to poor cell penetration, nonspecific effects, rapid degradation, and short half-life. We herewith proposed the formulation development of STAT6 siRNA (S6S) nanotherapeutic agent by encapsulating them within gelatin nanocarriers (GNC). The prepared nanoformulation was characterized for size, charge, loading efficiency, release kinetics, stability, cytotoxicity, and gene silencing assay. The stability of S6S-GNC was also assessed under conditions of varying pH, serum level, and using electrophoretic assays. In vitro cytotoxicity performance was evaluated in human adenocarcinoma A549 cells following MTT assay. The developed formulation resulted in an average particle size, surface charge, and encapsulation efficiency as 70 ± 6.5 nm, +10 ± 1.5 mV, and 85 ± 4.0%, respectively. S6S-GNC showed an insignificant (P < 0.05) change in the size and charge in the presence of buffer solutions (pH 6.4 to 8.4) and FBS (10% v/v). A549 cells were treated with native S6S, S6S-lipofectamine, placebo-GNC, and S6S-GNC using untreated cells as a control. It was observed that cell viability was decreased significantly with S6S-GNC by 55 ± 4.1% (P < 0.001) compared to native S6S (2.0 ± 0.55%) and S6S-lipofectamine complex (40 ± 3.1%). This investigation infers that gelatin polymer-based nanocarriers are a robust, stable, and biocompatible strategy for the delivery of siRNA.

Spontaneous mesotheliomas in F344/N rats are characterized by dysregulation of cellular growth and immune function pathways

Aged male Fischer 344/N rats are prone to developing spontaneous peritoneal mesotheliomas that arise predominantly from the tunica vaginalis of the testes. A definitive cause for the predominance of this neoplasm in F344/N rats is unknown. Investigation of the molecular alterations that occur in spontaneous rat mesotheliomas may provide insight into their pathogenesis as well enable a better understanding regarding the mechanisms underlying chemically induced mesothelioma in rodents. Mesothelial cell function represents a complex interplay of pathways related to host defense mechanisms and maintenance of cellular homeostasis. Global gene expression profiles of spontaneous mesotheliomas from vehicle control male F344/N rats from 2-year National Toxicology Program carcinogenicity bioassays were analyzed to determine the molecular features of these tumors and elucidate tumor-specific gene expression profiles. The resulting gene expression pattern showed that spontaneous mesotheliomas are associated with upregulation of various growth factors, oncogenes, cytokines, pattern recognition response receptors, and pathogen-associated molecular patterns receptors, and the production of reactive oxygen and nitrogen species, as well as downregulation of apoptosis pathways. Alterations in these pathways in turn trigger molecular responses that stimulate cell proliferation and promote tumor survival and progression.