Luciano Mutti

Guidelines of the European Respiratory Society and the European Society of Thoracic Surgeons for the management of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare tumour but with increasing incidence and a poor prognosis. In 2008, the European Respiratory Society/European Society of Thoracic Surgeons Task Force brought together experts to propose practical and up-to-dated guidelines on the management of MPM. To obtain an earlier and reliable diagnosis of MPM, the experts recommend performing thoracoscopy, except in cases of pre-operative contraindication or pleural symphysis. The standard staining procedures are insufficient in ∼10% of cases. Therefore, we propose using specific immunohistochemistry markers on pleural biopsies. In the absence of a uniform, robust and validated staging system, we advice use of the most recent TNM based classification, and propose a three step pre-treatment assessment. Patients performance status and histological subtype are currently the only prognostic factors of clinical importance in the management of MPM. Other potential parameters should be recorded at baseline and reported in clinical trials. MPM exhibits a high resistance to chemotherapy and only a few patients are candidates for radical surgery. New therapies and strategies have been reviewed. Because of limited data on the best combination treatment, we emphasise that patients who are considered candidates for a multimodal approach should be included in a prospective trial at a specialised centre.

Tremelimumab for patients with chemotherapy-resistant advanced malignant mesothelioma: an open-label, single-arm, phase 2 trial

BACKGROUND Monoclonal antibodies to cytotoxic T-lymphocyte antigen 4 (CTLA4) have therapeutic activity in different tumour types. We aimed to investigate the efficacy, safety, and immunological activity of the anti-CTLA4 monoclonal antibody, tremelimumab, in advanced malignant mesothelioma. METHODS In our open-label, single-arm, phase 2 study, we enrolled patients aged 18 years or older with measurable, unresectable malignant mesothelioma and progressive disease after a first-line platinum-based regimen. Eligible patients had to have a life expectancy of 3 months or more, an Eastern Cooperative Oncology Group performance status of 2 or less, and no history of autoimmune disease. Patients received tremelimumab 15 mg/kg intravenously once every 90 days until progressive disease or severe toxicity. The primary endpoint was the proportion of patients who achieved an objective response (complete or partial response), with a target response rate of 17% according to the modified Response Evaluation Criteria in Solid Tumors (RECIST) for pleural malignant mesothelioma or standard RECIST 1.0 for peritoneal malignant mesothelioma. Analyses were done according to intention to treat. This trial is registered with EudraCT, number 2008-005171-95, and ClinicalTrials.gov, number NCT01649024. FINDINGS Between May 27, 2009, and Jan 10, 2012, we enrolled 29 patients. All patients received at least one dose of tremelimumab (median two doses, range one to nine). No patients had a complete response and two patients (7%) had a durable partial response (one lasting 6 months and one lasting 18 months); one partial response occurred after initial progressive disease. Thus, the study did not reach its primary endpoint. However, we noted disease control in nine (31%) patients and a median progression-free survival of 6·2 months (95% CI 1·3-11·1) and a median overall survival of 10·7 months (0·0-21·9). 27 patients (93%) had at least one grade 1-2 treatment-emergent adverse event (mainly cutaneous rash, pruritus, colitis, or diarrhoea), and four patients (14%) had at least one grade 3-4 treatment-emergent adverse event (two gastrointestinal, one neurological, two hepatic, and one pancreatic). INTERPRETATION Although the effect size was small in our phase 2 trial, tremelimumab seemed to have encouraging clinical activity and an acceptable safety and tolerability profile in previously treated patients with advanced malignant mesothelioma. FUNDING Associazione Italiana per la Ricerca sul Cancro, Istituto Toscano Tumori, Pfizer, and Fondazione Buzzi Unicem.

Clinical Significance of Serum Mesothelin in Patients with Mesothelioma and Lung Cancer

Purpose: High levels of serum-soluble mesothelin family proteins (SMRP) have been found to be associated with malignant mesothelioma (MM), but not lung cancer (LC). To verify the clinical role of this marker for both these tumors, we tested serum SMRP in the largest population of thoracic cancers ever assembled. Experimental Design: SMRP blood concentrations were measured in 107 patients with MM, 215 patients with LC, 130 patients with benign respiratory diseases (BRD), and 262 controls. Statistical comparison between mean serum SMRP levels in all groups was done and receiver operating characteristic curves were constructed to evaluate the performance of this marker. Results: SMRP levels were significantly higher in patients with MM and LC than in patients with benign respiratory diseases and controls (P < 0.001). The area under the receiver operating characteristic curve for serum SMRP discriminating MM and controls was 0.77 (95% confidence interval, 0.71-0.83), with a best cutoff of 1.00 nmol/L (sensitivity, 68.2%; specificity, 80.5%). In both MM and LC, serum SMRP levels did not differ significantly between early and late stages. High SMRP levels proved to be an independent negative prognostic factor in patients with MM. Conclusions: Our data confirm that serum SMRP is a promising marker for the diagnosis, prognosis, and clinical monitoring of MM. We found that serum SMRP dosage may prove helpful in LC diagnosis as well. These data may also have positive repercussions on secondary preventive medical strategies for workers previously exposed to asbestos.

MicroRNA Signature of Malignant Mesothelioma with Potential Diagnostic and Prognostic Implications

MicroRNAs (miRNAs) post-transcriptionally regulate the expression of target genes, and may behave as oncogenes or tumor suppressors. Human malignant mesothelioma is an asbestos-related cancer, with poor prognosis and low median survival. Here we report, for the first time, a cross-evaluation of miRNA expression in mesothelioma (MPP-89, REN) and human mesothelial cells (HMC-telomerase reverse transcriptase). Microarray profiling, confirmed by real-time quantitative RT-PCR, revealed a differential expression of miRNAs between mesothelioma and mesothelial cells. In addition, a computational analysis combining miRNA and gene expression profiles allowed the accurate prediction of genes potentially targeted by dysregulated miRNAs. Several predicted genes belong to terms of Gene Ontology (GO) that are associated with the development and progression of mesothelioma. This suggests that miRNAs may be key players in mesothelioma oncogenesis. We further investigated miRNA expression on a panel of 24 mesothelioma specimens, representative of the three histotypes (epithelioid, biphasic, and sarcomatoid), by quantitative RT-PCR. The expression of miR-17-5p, miR-21, miR-29a, miR-30c, miR-30e-5p, miR-106a, and miR-143 was significantly associated with the histopathological subtypes. Notably, the reduced expression of two miRNAs (miR-17-5p and miR-30c) correlated with better survival of patients with sarcomatoid subtype. Our preliminary analysis points at miRNAs as potential diagnostic and prognostic markers of mesothelioma, and suggests novel tools for the therapy of this malignancy.

Bortezomib inhibits nuclear factor-kappaB dependent survival and has potent in vivo activity in mesothelioma.

Purpose: Purpose of this study has been the assessment of nuclear factor-κB (NF-κB) as a survival factor in human mesothelial cells (HMC), transformed HMC and malignant mesothelioma (MMe) cells. We aimed at verifying whether the proteasome inhibitor Bortezomib could abrogate NF-κB activity in MMe cells, leading to tumor cell death and may be established as a novel treatment for this aggressive neoplasm. Experimental Design: In HMC and MMe cells, NF-κB nuclear translocation and DNA binding were studied by electrophoretic mobility shift assay, following treatment with tumor necrosis factor-α (TNF-α). The IKK inhibitor Bay11-7082 was also tested to evaluate its effects on HMC, transformed HMC, and MMe cell viability upon exposure to asbestos fibers. Following Bortezomib treatment, cytotoxicity of MMe cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, whereas apoptosis and cell-cycle blockade were investigated by high-content analysis. Bortezomib was also given to mice bearing i.p. xenografts of MMe cells, and its effects on tumor growth were evaluated. Results: Here, we show that NF-κB activity is a constitutive survival factor in transformed HMC, MMe cells, and acts as a survival factor in HMC exposed to asbestos fibers. Bortezomib inhibits NF-κB activity in MMe cells and induces cell cycle blockade and apoptosis in vitro as well as tumor growth inhibition in vivo. Conclusions: Inhibition of NF-κB constitutive activation in MMe cells by Bortezomib resulted in in vitro cytotoxicity along with apoptosis and in vivo tumor regression. Our results support the use of Bortezomib in the treatment of MMe and has led to a phase II clinical trial currently enrolling in Europe.

SV40 Enhances the Risk of Malignant Mesothelioma among People Exposed to Asbestos: A Molecular Epidemiologic Case-Control Study

We conducted a case-control study on asbestos exposure and presence of SV40 in tumor samples of malignant mesotheliomas (MMs) and bladder urotheliomas (BUs). PCR analysis revealed the presence of SV40 DNA (SV40+) in eight (42.1%) MMs and 6 (33.3%) BUs. The odds ratio for MM Asb- and SV40+ was 0.4 [95% confidence interval (95% CI), 0.03-4.0], for Asb+ and SV40- was 3.6 (95% CI, 0.6-21.0), and for Asb+ and SV40+ was 12.6 (95% CI, 1.2-133.9). Our results suggest that SV40 increases the risk of MM among individuals exposed to asbestos.

SV40-Dependent AKT Activity Drives Mesothelial Cell Transformation after Asbestos Exposure

Human malignant mesothelioma is an aggressive cancer generally associated with exposure to asbestos, although SV40 virus has been involved as a possible cofactor by a number of studies. Asbestos fibers induce cytotoxicity in human mesothelial cells (HMC), although cell survival activated by key signaling pathways may promote transformation. We and others previously reported that SV40 large T antigen induces autocrine loops in HMC and malignant mesothelioma cells, leading to activation of growth factor receptors. Now we show that SV40 induces cell survival via Akt activation in malignant mesothelioma and HMC cells exposed to asbestos. Consequently, prolonged exposure to asbestos fibers progressively induces transformation of SV40-positive HMC. As a model of SV40/asbestos cocarcinogenesis, we propose that malignant mesothelioma originates from a subpopulation of transformed stem cells and that Akt signaling is a novel therapeutic target to overcome malignant mesothelioma resistance to conventional therapies.

Estrogen Receptor-β Affects the Prognosis of Human Malignant Mesothelioma

Malignant pleural mesothelioma is an asbestos-related neoplasm with poor prognosis, refractory to current therapies, the incidence of which is expected to increase in the next decades. Female gender was identified as a positive prognostic factor among other clinical and biological prognostic markers for malignant mesothelioma, yet a role of estrogen receptors (ERs) has not been studied. Our goal was to investigate ERs expression in malignant mesothelioma and to assess whether their expression correlates with prognosis. Immunohistochemical analysis revealed intense nuclear ERbeta staining in normal pleura that was reduced in tumor tissues. Conversely, neither tumors nor normal pleura stained positive for ERalpha. Multivariate analysis of 78 malignant mesothelioma patients with pathologic stage, histologic type, therapy, sex, and age at diagnosis indicated that ERbeta expression is an independent prognostic factor of better survival. Moreover, studies in vitro confirmed that treatment with 17beta-estradiol led to an ERbeta-mediated inhibition of malignant mesothelioma cell proliferation as well as p21(CIP1) and p27(KIP1) up-regulation. Consistently cell growth was suppressed by ERbeta overexpression, causing a G(2)-M-phase cell cycle arrest, paralleled by cyclin B1 and survivin down-regulation. Our data support the notion that ERbeta acting as a tumor suppressor is of high potential relevance to prediction of disease progression and to therapeutic response of malignant mesothelioma patients.

Genetic susceptibility to malignant pleural mesothelioma and other asbestos-associated diseases

Exposure to asbestos fibers is a major risk factor for malignant pleural mesothelioma (MPM), lung cancer, and other non-neoplastic conditions, such as asbestosis and pleural plaques. However, in the last decade many studies have shown that polymorphism in the genes involved in xenobiotic and oxidative metabolism or in DNA repair processes may play an important role in the etiology and pathogenesis of these diseases. To evaluate the association between diseases linked to asbestos and genetic variability we performed a review of studies on this topic included in the PubMed database. One hundred fifty-nine citations were retrieved; 24 of them met the inclusion criteria and were evaluated in the review. The most commonly studied GSTM1 polymorphism showed for all asbestos-linked diseases an increased risk in association with the null genotype, possibly linked to its role in the conjugation of reactive oxygen species. Studies focused on GSTT1 null and SOD2 Ala16Val polymorphisms gave conflicting results, while promising results came from studies on alpha1-antitrypsin in asbestosis and MPO in lung cancer. Among genetic polymorphisms associated to the risk of MPM, the GSTM1 null genotype and two variant alleles of XRCC1 and XRCC3 showed increased risks in a subset of studies. Results for the NAT2 acetylator status, SOD2 polymorphism and EPHX activity were conflicting. Major limitations in the study design, including the small size of study groups, affected the reliability of these studies. Technical improvements such as the use of high-throughput techniques will help to identify molecular pathways regulated by candidate genes.

Imatinib Mesylate Enhances Therapeutic Effects of Gemcitabine in Human Malignant Mesothelioma Xenografts

Purpose: Platelet-derived growth factor receptor β (PDGFRβ), frequently activated in malignant mesothelioma, is a promising cancer therapeutic target. Imatinib mesylate (STI571; Glivec) is a selective inhibitor of tyrosine kinases as bcr-abl, c-kit, c-fms, and PDGFRβ and enhances tumor drug uptake by reducing the interstitial fluid pressure. We previously showed that imatinib mesylate synergizes with gemcitabine and pemetrexed in PDGFRβ-positive mesothelioma cells. Here, we aimed at investigating these combined treatments in a novel mesothelioma model. Experimental Design: REN mesothelioma cells, infected with a lentiviral vector carrying the luciferase gene, were injected in the peritoneum of severe combined immunodeficient mice. This model allowed imaging of live animals treated with pemetrexed or gemcitabine chemotherapeutics, or with imatinib mesylate alone, as well as with a combination of gemcitabine and imatinib mesylate. Results: We show here that, consistent with our previous in vitro studies, gemcitabine inhibited tumor growth, whereas pemetrexed was ineffective, even at the highest dosage tested. Compared with monotreatment, the combination of gemcitabine with imatinib mesylate led to a further tumor growth inhibition and improved mice survival, by a decrease rate of tumor cell proliferation and an increase in number of apoptotic tumor cells. Conclusions: Imatinib mesylate enhances the therapeutic response to gemcitabine, in accordance with our previous in vitro data. These in vivo results validate imatinib mesylate and gemcitabine as a combination treatment of malignant mesothelioma, also in view of its known positive effects on tumor drug uptake. These evidences provide the rationale for the currently ongoing clinical trials.