Review of pemetrexed in combination with cisplatin for the treatment of malignant pleural mesothelioma

Laser ablation-inductively coupled plasma-mass spectrometry analysis reveals differences in chemotherapeutic drug distribution in surgically resected pleural mesothelioma

AIMS

Pleural mesothelioma (PM) is a highly aggressive thoracic tumour with poor prognosis. Although reduced tissue drug accumulation is one of the key features of platinum (Pt) resistance, little is known about Pt distribution in human PM.

METHODS

We assessed Pt levels of blood samples and surgically resected specimens from 25 PM patients who had received neoadjuvant Pt-based chemotherapy (CHT). Pt levels and tissue distributions were measured by laser ablation-inductively coupled plasma-mass spectrometry and correlated with clinicopathological features.

RESULTS

In surgically resected PM specimens, mean Pt levels of nontumourous (fibrotic) areas were significantly higher (vs tumourous regions, P = 0.0031). No major heterogeneity of Pt distribution was seen within the tumourous areas. Pt levels correlated neither with the microvessel area nor with apoptosis rate in the tumourous or nontumourous regions. A significant positive correlation was found between serum and both full tissue section and tumourous area mean Pt levels (r = 0.532, P = 0.006, 95% confidence interval [95% CI] 0.161-0.771 and r = 0.415, P = 0.039, 95% CI 0.011-0.702, respectively). Furthermore, a significant negative correlation was detected between serum Pt concentrations and elapsed time from the last cycle of CHT (r = -0.474, P = 0.017, 95% CI -0.738--0.084). Serum Pt levels correlated negatively with overall survival (OS) (P = 0.029).

CONCLUSIONS

There are major differences in drug distribution between tumourous and nontumourous areas of PM specimens. Serum Pt levels significantly correlate with full section and tumourous area average Pt levels, elapsed time from the last CHT cycle, and OS. Further studies investigating clinicopathological factors that modulate tissue Pt concentration and distribution are warranted.

The Immunological Landscape of M1 and M2 Macrophages and Their Spatial Distribution in Patients with Malignant Pleural Mesothelioma

BACKGROUND

Several tumor-associated macrophages (TAMs) have shown promise as prognosticators in cancer. Our aim was to validate the importance of TAMs in malignant pleural mesothelioma (MPM) using a two-stage design.

METHODS

We explored The Cancer Genome Atlas (TCGA-MESO) to select immune-relevant macrophage genes in MPM, including M1/M2 markers, as a discovery cohort. This computational cohort was used to create a multiplex immunofluorescence panel. Moreover, a cohort of 68 samples of MPM in paraffin blocks was used to validate the macrophage phenotypes and the co-localization and spatial distribution of these immune cells within the TME and the stromal or tumor compartments.

RESULTS

The discovery cohort revealed six immune-relevant macrophage genes (CD68, CD86, CD163, CD206, ARG1, CD274), and complementary genes were differentially expressed by M1 and M2 phenotypes with distinct roles in the tumor microenvironment and were associated with the prognosis. In addition, immune-suppressed MPMs with increased enrichment of CD68, CD86, and CD163 genes and high densities of M2 macrophages expressing CD163 and CD206 proteins were associated with worse overall survival (OS). Interestingly, below-median distances from malignant cells to specific M2a and M2c macrophages were associated with worse OS, suggesting an M2 macrophage-driven suppressive component in these tumors.

CONCLUSIONS

The interactions between TAMs in situ and, particularly, CD206+ macrophages are highly relevant to patient outcomes. High-resolution technology is important for identifying the roles of macrophage populations in tissue specimens and identifying potential therapeutic candidates in MPM.

Mesothelin expression remodeled the immune-matrix tumor microenvironment predicting the risk of death in patients with malignant pleural mesothelioma

Background

The combination of immunobiological agents with immune checkpoint proteins is a promising treatment for malignant pleural mesothelioma (MPM). Mesothelin and anti-PD-L1 antibody-drug conjugates specifically target malignant neoplastic cells, inhibit the migration and invasion of neoplastic cells, and restore the immune landscape. In this study, we confirmed the importance of mesothelin and examined the relationship between mesothelin and the immune landscape of the tumor microenvironment (TME) in two MPM cohorts.

Methods

The discovery cohort included 82 MPM cases. Tissue microarray slides were generated, and samples were processed for hematoxylin & eosin staining, immunohistochemistry, and immunofluorescence assays. The relationship between mesothelin, biomarkers of histogenesis, histological aggressiveness, PD-L1, immune cells (CD4, CD8, CD20, CD68), and collagen type I and type V fibers was evaluated by quantitative digital analyses. The outcome was the survival time until death from disease recurrence. The exploratory cohort included 87 malignant mesothelioma (MESO) patients from The Cancer Genome Atlas database.

Results

Most patients were male (70.7%) with a history of asbestos exposure (53.7%) and with the epithelioid subtype (89%). Surgical resection was performed in 85.4% of patients, and 14.6% received chemotherapy; 59.8% of patients died from disease extension to the mediastinum. Low tumor mesothelin expression was associated with tumor necrosis and nuclear grade 1, whereas high mesothelin expression was significantly associated with the epithelioid histotype and high density of T cells CD8+, macrophages CD68+, and collagen type I fibers. Cox multivariate analysis showed a high risk of death for non-operated patients [hazard ratio (HR), 3.42 (1.15-10.16)] with low tumor mesothelin levels [HR, 2.58 (1.09-6.10)] and high PD-L1 and low infiltration of T cells CD4+ [HR, 3.81 (1.58-9.18)]. In the exploratory cohort, low mesothelin and high COL1A1 and COL5A1 expression were associated with poor overall survival.

Conclusion

Tumor mesothelin expression associated with the TME immune landscape predicts the risk of death for patients with MPM and could be a new target for immunotherapy in MPM.

Induction of metallothionein expression by supplementation of zinc induces resistance against platinum-based treatment in malignant pleural mesothelioma

Background

Malignant pleural mesothelioma (MPM) is an aggressive tumor with a dismal prognosis. Currently, multimodality treatment including chemotherapy with cisplatin or carboplatin in combination with pemetrexed offers the best options. Detoxification of heavy metals in the cell by metallothioneins (MT) is associated with early failure to platin-based chemotherapy. The induction of MTs gene expression or its enzyme results in saturation by exposure to metal ions such as zinc or cadmium. Its therapeutically effect is still not analyzed in depth.

Methods

In our study, we investigated three MPM cell lines and one fibroblast cell line in the course of cisplatin treatment and supplementation of zinc. Cell state analyses via an enzyme-activity based assay were performed. With this, we were able to analyze apoptosis, necrosis and viability of cells. Additionally, we tested treated cells for changes in metallothionein IIA (MT2A) expression by using quantitative realtime polymerase chain reaction.

Results

Zinc supplementation induces gene expression of MT2A. Overall, a zinc dose-dependent induction of apoptosis under platin-based treatment could be observed. This effect could be verified in all analyzed cell lines in varying intensity.

Conclusions

MT expression is induced by zinc in a dose-dependent manner and inhibits a successful cisplatin therapy. Therefore, heavy metal exposure during cisplatin therapy, e.g., via cigarette smoke, might be an important factor. This should be considered in further therapeutic approaches.

One Third of Malignant Pleural Mesothelioma Shows High Immunohistochemical Expression of MSLN or CXCR4 Which Indicates Potent Candidates for Endo-Radiotherapy

Malignant pleural mesothelioma (MPM) is a mainly asbestos-related tumour associated with a very poor prognosis. Therapeutic approaches include multimodal therapy and chemotherapeutics, with cisplatin being the drug of choice, but response rates of only up to 14% indicate very poor outcomes. Effective treatment options are lacking. Besides the diagnostic usage of radioligands in positron emission tomography (PET)/computed tomography (CT), the endo-radioligand therapy with Lu177 has been proven as a powerful tool in cancer therapy. Mesothelin (MSLN) and C-XC chemokine receptor 4 (CXCR4) are membrane-bound proteins, expressed in certain cancers, and thus are promising targets for endo-radiotherapy. A significant portion of high MSLN- or CXCR4-expressing tumors within the MPM may open the field for this sophisticated treatment approach in the near future. Formalin-fixed, paraffin-embedded (FFPE) tumour specimens from 105 patients suffering from MPM and treated at the Lung Cancer Centre of Essen and at the Helios Klinikum Emil von Behring Berlin were screened. The tumour samples were arranged in tissue microarrays. We immunohistochemically stained the tumour samples against MSLN and CXCR4. The protein expressions of the stainings were scored by a pathologist by using a semiquantitative method. The data obtained were correlated with the clinical outcome. Overall, 77.1% of the analysed tumours showed CXCR4 protein expression (25.7% of them at high expression level (Score 3)). 48.6% of all samples showed an overall strong staining (Score ≥ 2), 59% of the investigated tumours showed MSLN protein expression (10.5% of them at high expression (Score 3)), and 36.2% of all samples showed an overall strong staining (Score ≥ 2). Our results show significant tissue expression levels, for both CXCR4 and MSLN protein, in a major portion of clinical MPM samples. One-third of patients showed outstanding immunoexpression of at least one of these markers, making them interesting candidates for radioligand-based PET/CT diagnostics and follow-up and furthermore may profit from endo-radiotherapy.

A Narrative Review-Management of Malignant Pleural Effusion Related to Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive, almost universally fatal cancer with limited therapeutic options. Despite efforts, a real breakthrough in treatment and outcomes has been elusive. Pleural effusion with significant breathlessness and pain is the most typical presentation of individuals with MPM. Although thoracentesis provides relief of breathlessness, most such pleural effusions recur rapidly, and a definitive procedure is often required to prevent a recurrence. Unfortunately, the optimal treatment modality for individuals with recurrent MPM-related effusion is unclear, and considerable variation exists in practice. In addition, non-expandable lung is common in pleural effusions due to MPM and makes effective palliation of symptoms more difficult. This review delves into the latest advances in the available management options (both surgical and non-surgical) for dealing with pleural effusion and non-expandable lung related to MPM. We discuss factors that determine the choice of definitive procedures that need to be tailored to the individual patient.

YAP/TAZ activation predicts clinical outcomes in mesothelioma and is conserved in in vitro model of driver mutations

The Hippo signalling pathway is dysregulated across a wide range of cancer types and, although driver mutations that directly affect the core Hippo components are rare, a handful is found within pleural mesothelioma (PM). PM is a deadly disease of the lining of the lung caused by asbestos exposure. By pooling the largest-scale clinical datasets publicly available, we here interrogate associations between the most prevalent driver mutations within PM and Hippo pathway disruption in patients, while assessing correlations with a variety of clinical markers. This analysis reveals a consistent worse outcome in patients exhibiting transcriptional markers of YAP/TAZ activation, pointing to the potential of leveraging Hippo pathway transcriptional activation status as a metric by which patients may be meaningfully stratified. Preclinical models recapitulating disease are transformative in order to develop new therapeutic strategies. We here establish an isogenic cell-line model of PM, which represents the most frequently mutated genes and which faithfully recapitulates the molecular features of clinical PM. This preclinical model is developed to probe the molecular basis by which the Hippo pathway and key driver mutations affect cancer initiation and progression. Implementing this approach, we reveal the role of NF2 as a mechanosensory component of the Hippo pathway in mesothelial cells. Cellular NF2 loss upon physiological stiffnesses analogous to the tumour niche drive YAP/TAZ-dependent anchorage-independent growth. Consequently, the development and characterisation of this cellular model provide a unique resource to obtain molecular insights into the disease and progress new drug discovery programs together with future stratification of PM patients.

Immunotherapy combined with antiangiogenic agents in patients with advanced malignant pleural mesothelioma: A case report

BACKGROUND

Malignant pleural mesothelioma has limited therapeutic options and a poor outcome. Antiangiogenic agents might increase the efficacy of immunotherapy as second-line treatment of advanced-stage malignancies.

CASE SUMMARY

A patient with stage IIIB pleural mesothelioma received second-line treatment with a combination of pembrolizumab, bevacizumab and chemotherapy following standard chemotherapy under the guidance of second-generation sequencing. He achieved a partial response after four cycles of treatment with progression-free survival of 5 mo. Pembrolizumab was suspended due to grade 2 immunerelated pneumonia, which was resolved by oral glucocorticoids. However, disease progression was observed after immunotherapy rechallenge and anlotinib therapy. The patient had disease progression, multiorgan dysfuntion and died suddenly in October 2019.

CONCLUSION

The combination of immune checkpoint inhibitor, anti-angiogenic agents and chemotherapy showed effective response for advanced pleural mesothelioma, but with adverse reactions.

Use of an antagonist of HMGB1 in mice affected by malignant mesothelioma: a preliminary ultrasound and optical imaging study

Background

Malignant mesothelioma (MM) is an aggressive tumor, with a poor prognosis, usually unresectable due to late diagnosis, mainly treated with chemotherapy. BoxA, a truncated form of “high mobility group box 1” (HMGB1), acting as an HMGB1 antagonist, might exert a defensive action against MM. We investigated the potential of BoxA for MM treatment using experimental 40-MHz ultrasound and optical imaging (OI) in a murine model.

Methods

Murine MM cells infected with a lentiviral vector expressing the luciferase gene were injected into the peritoneum of 14 BALB/c mice (7 × 10⁴ AB1-B/c-LUC cells). These mice were randomized to treatment with BoxA (n = 7) or phosphate-buffered saline (controls, n = 7). The experiment was repeated with 40 mice divided into two groups (n = 20 + 20) and treated as above to confirm the result and achieve greater statistical power. Tumor presence was investigated by experimental ultrasound and OI; suspected peritoneal masses underwent histopathology and immunohistochemistry examination.

Results

In the first experiment, none of the 7 controls survived beyond day 27, whereas 4/7 BoxA-treated mice (57.1%) survived up to day 70. In the second experiment, 6/20 controls (30.0%) and 16/20 BoxA-treated mice (80.0%) were still alive at day 34 (p = 0.004). In both experiments, histology confirmed the malignant nature of masses detected using experimental ultrasound and OI.

Conclusion

In our preclinical experience on a murine model, BoxA seems to exert a protective role toward MM. Both experimental ultrasound and OI proved to be reliable techniques for detecting MM peritoneal masses.

Optimization of a Luciferase-Expressing Non-Invasive Intrapleural Model of Malignant Mesothelioma in Immunocompetent Mice

Malignant Pleural Mesothelioma (MPM) is an aggressive tumor of the pleural lining that is usually identified at advanced stages and resistant to current therapies. Appropriate pre-clinical mouse tumor models are of pivotal importance to study its biology. Usually, tumor cells have been injected intraperitoneally or subcutaneously. Using three available murine mesothelioma cell lines with different histotypes (sarcomatoid, biphasic, epithelioid), we have set up a simplified model of in vivo growth orthotopically by inoculating tumor cells directly in the thorax with a minimally invasive procedure. Mesothelioma tumors grew along the pleura and spread on the superficial areas of the lungs, but no masses were found outside the thoracic cavity. As observed in human MPM, tumors were highly infiltrated by macrophages and T cells. The luciferase-expressing cells can be visualized in vivo by bioluminescent optical imaging to precisely quantify tumor growth over time. Notably, the bioluminescence signal detected in vivo correctly matched the tumor burden quantified with classical histology. In contrast, the subcutaneous or intraperitoneal growth of these mesothelioma cells was considered either non-representative of the human disease or unreliable to precisely quantify tumor load. Our non-invasive in vivo model of mesothelioma is simple and reproducible, and it reliably recapitulates the human disease.

Screening of Pleural Mesothelioma Cell Lines for Kinase Activity May Identify New Mechanisms of Therapy Resistance in Patients Receiving Platin-Based Chemotherapy

Background

Malignant pleural mesothelioma (MPM) is a rare, predominantly asbestos-related and biologically highly aggressive tumor associated with a dismal prognosis. Multimodal therapy consisting of platinum-based chemotherapy is the treatment of choice. The reasons underlying the rather poor efficacy of platinum compounds remain largely unknown. Kinase activity might influence cellular response to these regimens.

Materials and Methods

For this exploratory study, we screened MPM cell lines (NCI-H2452, NCI-H2052, and MSTO-211H) differing in response to cisplatin and benign control fibroblasts (MRC-5) for overall phosphorylation patterns as well as kinase activity with respect to cellular response to cisplatin-based therapeutics. We analysed the cell lines for cellular kinases in a high-throughput manner using the highly innovative technique PamGene. Cell state analysis including apoptosis, necrosis, and cell viability was performed by using enzyme activity and fluorescent-based assays.

Results

Cisplatin alters cellular phosphorylation patterns affecting cell cycle, migration, adhesion, signal transduction, immune modulation, and apoptosis. In cisplatin-responsive cell lines, phosphorylation of AKT1 and GSK3B was decreased but could not be influenced in cisplatin-resistant NCI-H2452 cells. Cisplatin-responsive cell lines showed increased phosphorylation levels of JNK1/2/3 but decreased phosphorylation in cisplatin-resistant NCI-H2452 cells.

Conclusion

Kinase phosphorylation and activity might play a crucial role in cellular response to cytostatic agents. Cisplatin influences phosphorylation patterns with distinct features in cisplatin-resistant cells. These alterations exert a significant impact on cell cycle, migration, adhesion, signal transduction, immune modulation, and apoptosis of the respective tumor cells. Based on our results, the induction of p38 or JNK1/3, or inhibition of AKT1 by, for example, BIA-6, might offer a positive synergistic effect by induction of an apoptotic response to cisplatin-based treatment, thus potentially enhancing the clinical outcome of MPM patients.

Droplet digital PCR as a novel system for the detection of microRNA‑34b/c methylation in circulating DNA in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare malignancy arising from the pleura that is difficult to diagnose, contributing to its dismal prognosis. Previously, we reported that the degree of microRNA (miR)‑34b/c methylation in circulating DNA is associated with the development of MPM. Herein, we present a newly developed droplet digital PCR (ddPCR)‑based assay for the detection of miR‑34b/c methylation in circulating DNA in patients with MPM. We originally prepared two probes within a short amplicon of 60 bp, designing one from the positive strand and the other from the complementary strand. The two probes functioned cooperatively, and our established assay detected DNA methylation accurately in the preliminary validation. We subsequently verified this assay using clinical samples. Serum samples from 35 cases of MPM, 29 cases of pleural plaque and 10 healthy volunteers were collected from 3 different institutions and used in this study. We divided the samples into 2 groups (group A, n=33; group B, n=41). A receiver‑operating characteristic curve analysis using the samples in group A determined the optimal cut‑off value for the diagnosis of MPM, with a sensitivity of 76.9% and a specificity of 90%. On the other hand, the use of the same criterion yielded a sensitivity of 59.1% and a specificity of 100% in group B, and corresponding values of 65.7 and 94.9% for the entire cohort, indicating a moderate sensitivity and a high specificity. In addition, when the analysis was focused on stage II or more advanced MPM, the sensitivity improved to 81.8%, suggesting the possibility that the methylated allele frequency in MPM may be associated with the stage of disease progression. On the whole, the findings of this study indicate that miR‑34b/c methylation in circulating DNA is a promising biomarker for the prediction of disease progression in patients with MPM.

Interplay of non-coding RNAs and approved antimetabolites such as gemcitabine and pemetrexed in mesothelioma

Gemcitabine and pemetrexed are clinically approved antimetabolites for the therapy of mesothelioma diseases. These drugs are often applied in combination with platinum complexes and other drugs. The activity of antimetabolites depended on the expression levels of certain non-coding RNAs, in particular, of small microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). The development of tumor resistance towards antimetabolites was regulated by non-coding RNAs. An overview of the interplay between gemcitabine/pemetrexed antimetabolites and non-coding RNAs in mesothelioma is provided. Further to this, various non-coding RNA-modulating agents are discussed which displayed positive effects on gemcitabine or pemetrexed treatment of mesothelioma diseases. A detailed knowledge of the connections of non-coding RNAs with antimetabolites will be constructive for the design of improved therapies in future.

Biodistribution and Tumor Uptake of 67Ga-Nimotuzumab in a Malignant Pleural Mesothelioma Xenograft

Malignant pleural mesothelioma (MPM) is the most common tumor of the pulmonary pleura. It is a rare and aggressive malignancy, generally associated with continuous occupational exposure to asbestos. Only a multimodal-approach to treatment, based on surgical resection, chemotherapy and/or radiation, has shown some benefits. However, the survival rate remains low. Nimotuzumab (h-R3), an anti-EGFR (epidermal growth factor receptor) humanized antibody, is proposed as a promising agent for the treatment of MPM. The aim of this research was to implement a procedure for nimotuzumab radiolabeling to evaluate its biodistribution and affinity for EGF (epidermal growth factor) receptors present in a mesothelioma xenograft. Nimotuzumab was radiolabeled with 67Ga; radiolabel efficiency, radiochemical purity, serum stability, and biodistribution were evaluated. Biodistribution and tumor uptake imaging studies by microSPECT/CT in mesothelioma xenografts revealed constant nimotuzumab uptake at the tumor site during the first 48 h after drug administration. In vivo studies using MPM xenografts showed a significant uptake of this radioimmunoconjugate, which illustrates its potential as a biomarker that could promote its theranostic use in patients with MPM.

Safety of Same-Day Vitamin B12 Supplementation in Patients Receiving Pemetrexed for the Treatment of Non-Small-Cell Lung Cancer or Pleural Mesothelioma: A Retrospective Analysis

BACKGROUND

Pemetrexed is a folate analog inhibitor for the treatment of non-small-cell lung cancer (NSCLC) and malignant pleural mesothelioma. Folic acid and vitamin B12 supplementation before initiating pemetrexed is necessary because of high rates of cytopenias without supplementation. However, the timing of supplementation has not been thoroughly investigated.

PATIENTS AND METHODS

This was a single-center, retrospective study investigating patients receiving pemetrexed from January 1, 2012, to June 30, 2015, who received same-day vitamin B12 supplementation versus ≥ 1 day before pemetrexed. The objective was to evaluate safety outcomes in patients who received vitamin B12 on the same day as pemetrexed (group A) versus vitamin B12 ≥ 1 day (group B) before pemetrexed.

RESULTS

Two hundred eighty-one patients met the inclusion criteria: 137 patients in group A (same-day administration of vitamin B12) and 144 patients in group B (median time of vitamin B12 administration before pemetrexed, 7 days; range, 1-42 days). Mean changes in hematologic indices from cycle (C) 1 to C2 or C2 to C3 did not differ significantly between groups. There were no significant differences in clinical events between C1 and C2 or C2 and C3 requiring supportive care. There was a significant difference noted in treatment delay in C3 [28/114 (24.6%) group A vs. 14/118 (11.9%) group B, P = .0164]. In group A, significant predictors of delay in C3 were baseline hemoglobin (mean 13.3 g/dL vs. 12.4 g/dL, P = .0137) and ANC (mean 6 × 10⁹/L vs. 5 × 10⁹/L, P = .0003).

CONCLUSION

Same-day vitamin B12 and pemetrexed administration is a safe practice in NSCLC and malignant pleural mesothelioma patients.

Inhibition of MDM2 via Nutlin-3A: A Potential Therapeutic Approach for Pleural Mesotheliomas with MDM2-Induced Inactivation of Wild-Type P53

Previously, our group demonstrated that nuclear expression of E3 ubiquitin ligase (MDM2) in malignant pleural mesothelioma (MPM) is significantly associated with decreased overall survival. A possible explanation may be that overexpression of MDM2 leads to a proteasomal degradation of TP53 that eventually results in a loss of TP53-induced apoptosis and senescence. It is well known from other tumor entities that restoration of TP53 activity, e.g., by MDM2 inhibition, results in an instant TP53-induced stress and/or DNA damage response of cancer cells. Nutlin-3A (a cis-imidazoline analogue) has been described as a potent and selective MDM2 inhibitor preventing MDM2-TP53-interaction by specific binding to the hydrophobic TP53-binding pocket of MDM2. In the present study, the effects of MDM2 inhibition in MPM via Nutlin-3A and standard platinum based chemotherapeutic agents were comparatively tested in three MPM cell lines (NCI-H2052, MSTO-211H, and NCI-H2452) showing different expression profiles of TP53, MDM2, and its physiological inhibitor of MDM2—P14/ARF. Our in vitro experiments on MPM cell lines revealed that Nutlin-3A in combination with cisplatin resulted in up to 9.75 times higher induction of senescence (p=0.0050) and up to 5 times higher apoptosis rate (p=0.0067) compared to the commonly applied cisplatin and pemetrexed regimens. Thus Nutlin-3A, a potent inhibitor of MDM2, is associated with a significant induction of senescence and apoptosis in MPM cell lines, making Nutlin-3A a promising substance for a targeted therapy in the subgroup of MPM showing MDM2 overexpression.

Increased sensitivity to apoptosis upon endoplasmic reticulum stress-induced activation of the unfolded protein response in chemotherapy-resistant malignant pleural mesothelioma

BACKGROUND

Standard treatment for advanced malignant pleural mesothelioma (MPM) is a cisplatin/pemetrexed (MTA) regimen; however, this is confronted by drug resistance. Proteotoxic stress in the endoplasmic reticulum (ER) is a hallmark of cancer and some rely on this stress signalling in response to cytotoxic chemotherapeutics. We hypothesise that ER stress and the adaptive unfolded protein response (UPR) play a role in chemotherapy resistance of MPM.

METHODS

In vitro three-dimensional (3D) and ex vivo organotypic culture were used to enrich a chemotherapy-resistant population and recapitulate an in vivo MPM microenvironment, respectively. Markers of ER stress, the UPR and apoptosis were assessed at mRNA and protein levels. Cell viability was determined based on acid phosphatase activity.

RESULTS

MPM cells with de novo and/or acquired chemotherapy resistance displayed low ER stress, which rendered the cells hypersensitive to agents that induce ER stress and alter the UPR. Bortezomib, an FDA-approved proteasome inhibitor, selectively impairs chemotherapy-resistant MPM cells by activating the PERK/eIF2α/ATF4-mediated UPR and augmenting apoptosis.

CONCLUSIONS

We provide the first evidence for ER stress and the adaptive UPR signalling in chemotherapy resistance of MPM, which suggests that perturbation of the UPR by altering ER stress is a novel strategy to treat chemotherapy-refractory MPM.

Immunohistochemically detectable metallothionein expression in malignant pleural mesotheliomas is strongly associated with early failure to platin-based chemotherapy

Background

Malignant pleural mesothelioma (MPM) is a biologically highly aggressive tumor arising from the pleura with a dismal prognosis. Cisplatin is the drug of choice for the treatment of MPM, and carboplatin seems to have comparable efficacy. Nevertheless, cisplatin treatment results in a response rate of merely 14% and a median survival of less than seven months. Due to their role in many cellular processes, methallothioneins (MTs) have been widely studied in various cancers. The known heavy metal detoxifying effect of MT-I and MT-II may be the reason for heavy metal drug resistance of various cancers including MPM.

Methods

105 patients were retrospectively analyzed immunohistochemically for their MT expression levels. Survival analysis was done by Cox-regression, and statistical significance determined using likelihood ratio, Wald test and Score (logrank) tests.

Results

Cox-regression analyses were done in a linear and logarithmic scale revealing a significant association between expression of MT and shortened overall survival (OS) in a linear (p=0.0009) and logarithmic scale (p=0.0003). Reduced progression free survival (PFS) was also observed for MT expressing tumors (linear: p=0.0134, log: p=0.0152).

Conclusion

Since both, overall survival and progression-free survival are negatively correlated with detectable MT expression in MPM, our results indicate a possible resistance to platin-based chemotherapy associated with MT expression upregulation, found exclusively in progressive MPM samples. Initial cell culture studies suggest promoter DNA hypomethylation and expression of miRNA-566 a direct regulator of copper transporter SLC31A1 and a putative regulator of MT1A and MT2A gene expression, to be responsible for the drug resistance.

Four immunohistochemical assays to measure the PD-L1 expression in malignant pleural mesothelioma

Immune checkpoint inhibitors (ICIs) targeting the PD-1/PD-L1 pathway are expected to be a novel therapy for combating future increases in numbers of malignant pleural mesothelioma (MPM) patients. However, the PD-L1 expression, which is a predictor of the response to ICIs, is unclear in MPM. We studied the PD-L1 expression using four immunohistochemical assays (SP142, SP263, 28-8 and 22C3) in 32 MPM patients. The PD-L1 expression in tumor cells and immune cells was evaluated to clarify the rate of PD-L1 expression and the concordance among the four assays in MPM. The positivity rate of PD-L1 expression was 53.1% for SP142, 28.1% for SP263, 53.1% for 28-8, and 56.3% for 22C3. Nine cases were positive and 10 were negative for all assays. Discordance among the four assays was found in 13 cases. The concordance rates between SP142 and 22C3 and between 28-8 and 22C3 were the highest (84.4%). The concordance rates between SP263 and the other three assays were low (71.9% to 75.0%). The PD-L1 expression in MPM was almost equivalent for three of the assays. Given the cut-off values set in our study, these findings suggested that these assays, except for SP263, can be used for accurate PD-L1 immunostaining in MPM.

Folic acid phenotype (FAP) is a superior biomarker predicting response to pemetrexed-based chemotherapy in malignant pleural mesothelioma

BACKGROUND

Malignant pleural mesothelioma (MPM) is a rare tumor linked to a dismal prognosis. Even the most effective chemotherapeutical regime of pemetrexed combined with cisplatin leads to a remission-rate of only about 40%. The reasons for the rather poor efficacy remain largely unknown.

RESULTS

Phenotypes were significantly associated with progression (p=0.0279) and remission (p=0.0262). Cox-regression revealed significant associations between SLC19A1/TYMS-ratio (p=0.0076) as well as FPGS/TYMS-ratio (p=0.0026) and OS. For differentiation by risk-groups, COXPH identified a strong correlation (p=0.0008).

METHODS

56 MPM specimens from patients treated with pemetrexed were used for qPCR analysis. Phenotypes and risk groups were defined by their expression levels of members of the folic acid metabolism and correlated to survival and objective response.

CONCLUSION

Our results indicate that the balance between folic acid uptake, activation and metabolism plays a crucial role in response to pemetrexed-based chemotherapy and the prognosis of MPM patients. Implementing this marker profile in MPM stratification may help to individualize MPM-therapy more efficiently.

Chemotherapy treatment in malignant pleural mesothelioma: a difficult history

Malignant pleural mesothelioma (MPM) is a rare neoplasm that typically arises from mesothelial surfaces of the pleural cavity. Despite treatment improvements, it carries a dismal prognosis. The majority of patients either have unresectable disease or are not candidates for surgery due to medical comorbidities or old age. For such patients, chemotherapy (CT) represents the gold-standard treatment. To date, combination CT with cisplatin plus pemetrexed represents the most widely used regimen in first-line setting for patients with unresectable MPM. Other first-line options are currently available, including the use of raltitrexed instead of pemetrexed combined with platinum. In this review, we discuss the role of CT in MPM mainly focusing on the results of the trials conducted in first-line setting.

Retrospective study of hypersensitivity reactions to chemotherapeutic agents in a thoracic oncology service

WHAT IS KNOWN AND OBJECTIVE

With the increasing use of cancer chemotherapy agents, hypersensitivity reactions are commonly encountered. The allergic clinical symptoms are variable and unpredictable. The aim of this study was to identify the characteristics of hypersensitivity reactions and to assess the value of skin tests for platinum salts and pemetrexed in the treatment of patients with non-small cell lung cancers or malignant pleural mesothelioma.

METHODS

A single-centre retrospective study was performed for 2 years. Patients treated with the drugs of interest for an advanced or metastatic non-small cell lung cancers or malignant pleural mesothelioma and who experienced hypersensitivity reactions symptoms were eligible for this study. Clinical symptoms of hypersensitivity reactions, population characteristics and administered chemotherapy regimens were identified.

RESULTS

The hypersensitivity reactions frequency was rare (1.2%) and concerned 17 patients in our study. Typical clinical features of immediate hypersensitivity reactions associated with treatment were observed for nine patients (anaphylactic reactions for three cases, angioedema and hypotension associated with asthenia and heat in one case, respectively, and other cutaneous symptoms in the remaining four cases). Skin tests were positive in three patients, but only for platinum salts. The outcome after reintroduction of a negatively tested platinum salt allowed us to calculate a negative predictive value for platinum salt skin tests of 100%. For pemetrexed, skin tests were negative for all patients.

WHAT IS NEW AND CONCLUSION

Skin tests could be used to diagnose hypersensitivity reactions with platinum salts or to evaluate the possibility of cross-reactions between two platinum salts. A negative skin test may predict with reasonable reliability the absence of future hypersensitivity reactions in case of reintroduction of drug infusion. Because the IgE-mediated mechanism has never been demonstrated for pemetrexed, skin tests are not valid and have no diagnostic value for this molecule. Because hypersensitivity reactions are potentially fatal adverse events, we recommend that patients who experience a hypersensitivity reactions onset should be monitored closely and clinicians must be aware of hypersensitivity reaction signs.

Advances in systemic therapy for malignant mesothelioma: future perspectives

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

miRNA regulation is important for DNA damage repair and recognition in malignant pleural mesothelioma

Platin-containing regimes are currently considered as state-of-the-art therapies in malignant pleural mesotheliomas (MPM) but show dissatisfying response rates ranging from 6 to 16% only. Still, the reasons for the rather poor efficacy remain largely unknown. A clear stratification of patients based on new biomarkers seems to be a promising approach to enhance clinical management, which would be a long-needed improvement for MPM patients but does not seem likely soon unless new biomarkers can be validated. Twenty-four formalin-fixed, paraffin-embedded (FFPE) tumour specimens were subjected to a miRNA expression screening of 800 important miRNAs using digital quantification via the nCounter technique (NanoString). We defined a small subset of miRNAs regulating the key enzymes involved in the repair of platin-associated DNA damage. Particularly, the TP53 pathway network for DNA damage recognition as well as genes related to the term "BRCAness" are the main miRNA targets within this context. The TP53 pathway network for DNA damage recognition as well as genes related to the term "BRCAness" are the main players for risk stratification in patients suffering from this severe disease. Taking the specific molecular profile of the tumour into account can help to enhance the clinical management prospectively and to smooth the way to better response prediction.

microRNAs are differentially regulated between MDM2-positive and negative malignant pleural mesothelioma

Background

Malignant pleural mesothelioma (MPM) is a highly aggressive tumour first-line treated with a combination of cisplatin and pemetrexed. MDM2 and P14/ARF (CDKN2A) are upstream regulators of TP53 and may contribute to its inactivation. In the present study, we now aimed to define the impact of miRNA expression on this mechanism.

Material and Methods

24 formalin-fixed paraffin-embedded (FFPE) tumour specimens were used for miRNA expression analysis of the 800 most important miRNAs using the nCounter technique (NanoString). Significantly deregulated miRNAs were identified before a KEGG-pathway analysis was performed.

Results

17 miRNAs regulating TP53, 18 miRNAs regulating MDM2, and 11 miRNAs directly regulating CDKN2A are significantly downregulated in MDM2-expressing mesotheliomas. TP53 is downregulated in MDM2-negative tumours through miRNAs with a miSVR prediction score of 11.67, RB1 with a prediction score of 8.02, MDM2 with a prediction score of 4.50 and CDKN2A with a prediction score of 1.27.

Conclusion

MDM2 expression seems to impact miRNA expression levels in MPM. Especially, miRNAs involved in TP53-signaling are strongly decreased in MDM2-positive mesotheliomas. A better understanding of its tumour biology may open the chance for new therapeutic approaches and thereby augment patients' outcome.

Metabolic response assessment with 18F-FDG-PET/CT is superior to modified RECIST for the evaluation of response to platinum-based doublet chemotherapy in malignant pleural mesothelioma

PURPOSE

Efficient monitoring of tumor responsiveness to chemotherapy is essential to mitigate high mortality risks and cytotoxic effects of chemotherapeutics. However, there is no consensus on the most suitable diagnostic technique/parameters for assessing response to chemotherapy in malignant pleural mesothelioma (MPM). We compared the tumor responsiveness of MPM patients as assessed using modified RECIST (mRECIST) criteria and integrated 18F-FDG-PET/CT.

METHODS

Histologically confirmed MPM patients (N=82) who were treated with three cycles of cisplatin and pemetrexed, or carboplatin and pemetrexed, were included. mRECIST and integrated 18F-FDG-PET/CT were used to evaluate MPM tumor response to chemotherapy. Metabolic non-responders were defined as those with a 25% or greater increase in SUVmax compared with the previous value. Time to progression (TTP) and overall survival (OS) were compared between metabolic-responders and non-responders.

RESULTS

After three cycles of chemotherapy, 62(75.6%) of the patients were classified as having SD, 15 (18%) with partial remission (PR), and 5 (6%) with progressive disease (PD), based on mRECIST criteria. The cumulative median OS was 728.0days (95% confidence interval [CI]: 545.9-910.1) and cumulative median TTP was 365.0days (95% CI: 296.9-433.1). For the 82 patients, the disease control rate was 93.9%, whereas the metabolic response rate was only 71.9% (p<0.001). All PD and PR patients were found to be metabolic responders on 18F-FDG-PET/CT; however, among the 62mRECIST SD patients, 18 (29%) were classified as metabolic non-responders. The median TTP for metabolic responders was 13.7 months, while it was 10.0 months for non-responders(p<0.001). Metabolic responders had a trend toward longer OS, although the difference did not reach statistical significance (metabolic responders:33.9 months; non-responders: 21.6 months; p>0.05).

CONCLUSION

Several mRECIST-confirmed SD MPM patients may be classified as metabolic non-responders on18F-FDGPET/CT. Metabolic response is significantly correlated with the median TTP, suggesting it should be included in the evaluation of the response to chemotherapy in MPM patients classified as mRECIST SD, to identify non-responders.

Calretinin but not caveolin-1 correlates with tumour histology and survival in malignant mesothelioma

Malignant mesothelioma (MM) continues to be a disease with poor prognosis and limited treatment options. Calretinin and caveolin-1 expression by tumour in MM have recently been described to be associated with tumour histology, differentiation and consequently survival. In a large, well annotated cohort, we studied both of these biomarkers and explored their association with clinicopathological parameters and survival. A retrospective search of patients with MM who underwent surgery at the Austin Hospital in Melbourne, Australia, was conducted. Clinical history and outcome data were retrieved from patient records. Tissue microarrays (TMAs) were constructed and stained for calretinin and caveolin-1. 'H scores' were derived, taking intensity and distribution of staining, and the cohort was dichotomised using median values for both markers. In the 329 patients evaluated, median age was 67 years. Males outnumbered females by 5:1. Epithelioid histology 202/319 (62.9%) was the most common, followed by biphasic 72/319 (21.8%) and sarcomatoid 45/319 (13.6%); histology could not be confirmed in 10 patients. Calretinin expression was detected in 246 of the 324 (76%) evaluable patients and high expression was associated with epithelioid histology (p < 0.0001). Caveolin-1 was expressed in 298 (94%) of 317 evaluable patients which was much higher compared to its expression in a cohort of lung adenocarcinomas (8/58, 13.7%). However, no association with histology was found (p = 0.409). When taken as a continuous variable, calretinin expression was found to be an independent predictor of survival, alongside histology, neutrophil-lymphocyte ratio, weight loss and stage. No prognostic value was demonstrable for caveolin-1 expression and calretinin/caveolin-1 ratio. There was no relationship between calretinin and caveolin-1 expression. In MM, increased calretinin expression is associated with epithelioid histology and better survival. Caveolin-1 is a sensitive MM marker and is expressed in a high proportion of cases but lacks association with histology and survival.

Screening of Pleural Mesotheliomas for DNA-damage Repair Players by Digital Gene Expression Analysis Can Enhance Clinical Management of Patients Receiving Platin-Based Chemotherapy

Background: Malignant pleural mesothelioma (MPM) is a rare, predominantly asbestos-related and biologically highly aggressive tumour leading to a dismal prognosis. Multimodality therapy consisting of platinum-based chemotherapy is the treatment of choice. The reasons for the rather poor efficacy of platinum compounds remain largely unknown.

Material and Methods: For this exploratory mRNA study, 24 FFPE tumour specimens were screened by digital gene expression analysis. Based on data from preliminary experiments and recent literature, a total of 366 mRNAs were investigated using a Custom CodeSet from NanoString. All statistical analyses were calculated with the R i386 statistical programming environment.

Results: CDC25A and PARP1 gene expression were correlated with lymph node spread, BRCA1 and TP73 expression levels with higher IMIG stage. NTHL1 and XRCC3 expression was associated with TNM stage. CHECK1 as well as XRCC2 expression levels were correlated with tumour progression in the overall cohort of patients. CDKN2A and MLH1 gene expression influenced overall survival in this collective. In the adjuvant treated cohort only, CDKN2A, CHEK1 as well as ERCC1 were significantly associated with overall survival. Furthermore, TP73 expression was associated with progression in this subgroup.

Conclusion: DNA-damage response plays a crucial role in response to platin-based chemotherapeutic regimes. In particular, CHEK1, XRCC2 and TP73 are strongly associated with tumour progression. ERCC1, MLH1, CDKN2A and most promising CHEK1 are prognostic markers for OS in MPM. TP73, CDKN2A, CHEK1 and ERCC1 seem to be also predictive markers in adjuvant treated MPMs. After a prospective validation, these markers may improve clinical and pathological practice, finally leading to a patients' benefit by an enhanced clinical management.

The resistance related to targeted therapy in malignant pleural mesothelioma: Why has not the target been hit yet?

Malignant pleural mesothelioma (MPM) is an aggressive tumor of the pleura with a poor prognosis. The most active first-line regimens are platinum compounds and pemetrexed. There is no standard second-line treatment in MPM. Advances in the understanding of tumor molecular biology have led to the development of several targeted treatments, which have been evaluated in clinical trials. Unfortunately none of the explored targeted treatments can currently be recommended as routine treatment in MPM. We reviewed the biological pathways involved in MPM, the clinical trials about targeted therapy, and possible related mechanisms of resistance. We suggest that specific genetic markers are needed as targets of selective therapy. By this way the selection of patients based on the molecular profile may facilitate a therapeutic strategy that allows the use of the most appropriate drug for each patient.

Synergistic anti-tumor efficacy of immunogenic adenovirus ONCOS-102 (Ad5/3-D24-GM-CSF) and standard of care chemotherapy in preclinical mesothelioma model

Malignant mesothelioma (MM) is a rare cancer type caused mainly by asbestos exposure. The median overall survival time of a mesothelioma cancer patient is less than 1-year from diagnosis. Currently there are no curative treatment modalities for malignant mesothelioma, however treatments such as surgery, chemotherapy and radiotherapy can help to improve patient prognosis and increase life expectancy. Pemetrexed-Cisplatin is the only standard of care (SoC) chemotherapy for malignant mesothelioma, but the median PFS/OS (progression-free survival/overall survival) from the initiation of treatment is only up to 12 months. Therefore, new treatment strategies against malignant mesothelioma are in high demand. ONCOS-102 is a dual targeting, chimeric oncolytic adenovirus, coding for human GM-CSF. The safety and immune activating properties of ONCOS-102 have already been assessed in phase 1 study (NCT01598129). In this preclinical study, we evaluated the antineoplastic activity of combination treatment with SoC chemotherapy (Pemetrexed, Cisplatin, Carboplatin) and ONCOS-102 in xenograft BALB/c model of human malignant mesothelioma. We demonstrated that ONCOS-102 is able to induce immunogenic cell death of human mesothelioma cell lines in vitro and showed anti-tumor activity in the treatment of refractory H226 malignant pleural mesothelioma (MPM) xenograft model. While chemotherapy alone showed no anti-tumor activity in the mesothelioma mouse model, ONCOS-102 was able to slow down tumor growth. Interestingly, a synergistic anti-tumor effect was seen when ONCOS-102 was combined with chemotherapy regimens. These findings give a rationale for the clinical testing of ONCOS-102 in combination with first-line chemotherapy in patients suffering from malignant mesothelioma.

Human malignant mesothelioma is recapitulated in immunocompetent BALB/c mice injected with murine AB cells

Malignant Mesothelioma is a highly aggressive cancer, which is difficult to diagnose and treat. Here we describe the molecular, cellular and morphological characterization of a syngeneic system consisting of murine AB1, AB12 and AB22 mesothelioma cells injected in immunocompetent BALB/c mice, which allows the study of the interplay of tumor cells with the immune system. Murine mesothelioma cells, like human ones, respond to exogenous High Mobility Group Box 1 protein, a Damage-Associated Molecular Pattern that acts as a chemoattractant for leukocytes and as a proinflammatory mediator. The tumors derived from AB cells are morphologically and histologically similar to human MM tumors, and respond to treatments used for MM patients. Our system largely recapitulates human mesothelioma, and we advocate its use for the study of MM development and treatment.

MDM2 is an important prognostic and predictive factor for platin-pemetrexed therapy in malignant pleural mesotheliomas and deregulation of P14/ARF (encoded by CDKN2A) seems to contribute to an MDM2-driven inactivation of P53

Background:

Malignant pleural mesothelioma (MPM) is a highly aggressive tumour that is first-line treated with a combination of cisplatin and pemetrexed. Until now, predictive and prognostic biomarkers are lacking, making it a non-tailored therapy regimen with unknown outcome. P53 is frequently inactivated in MPM, but mutations are extremely rare. MDM2 and P14/ARF are upstream regulators of P53 that may contribute to P53 inactivation.

Methods:

A total of 72 MPM patients were investigated. MDM2 immunoexpression was assessed in 65 patients. MDM2 and P14/ARF mRNA expression was analysed in 48 patients of the overall collective. The expression results were correlated to overall survival (OS) and progression-free survival (PFS).

Results:

OS and PFS correlated highly significantly with MDM2 mRNA and protein expression, showing a dismal prognosis for patients with elevated MDM2 expression (for OS: Score (logrank) test: P⩽0.002, and for PFS: Score (logrank) test; P<0.007). MDM2 was identified as robust prognostic and predictive biomarker for MPM on the mRNA and protein level. P14/ARF mRNA expression reached no statistical significance, but Kaplan–Meier curves distinguished patients with low P14/ARF expression and hence shorter survival from patients with higher expression and prolonged survival.

Conclusions:

MDM2 is a prognostic and predictive marker for a platin–pemetrexed therapy of patients with MPMs. Downregulation of P14/ARF expression seems to contribute to MDM2-overexpression-mediated P53 inactivation in MPM patients.

A microfluidic platform for chemoresistive testing of multicellular pleural cancer spheroids

This study reports on a microfluidic platform on which single multicellular spheroids from malignant pleural mesothelioma (MPM), an aggressive tumor with poor prognosis, can be loaded, trapped and tested for chemotherapeutic drug response. A new method to detect the spheroid viability cultured on the microfluidic chip as a function of the drug concentration is presented. This approach is based on the evaluation of the caspase activity in the supernatant sampled from the chip and tested using a microplate reader. This simple and time-saving method does only require a minimum amount of manipulations and was established for very low numbers of cells. This feature is particularly important in view of personalised medicine applications for which the number of cells obtained from the patients is low. MPM spheroids were continuously perfused for 48 hours with cisplatin, one of the standard chemotherapeutic drugs used to treat MPM. The 50% growth inhibitory concentration of cisplatin in perfused MPM spheroids was found to be twice as high as in spheroids cultured under static conditions. This chemoresistance increase might be due to the continuous support of nutrients and oxygen to the perfused spheroids.

Tumor suppressor alterations cooperate to drive aggressive mesotheliomas with enriched cancer stem cells via a p53-miR-34a-c-Met axis

Malignant mesothelioma is a highly aggressive, asbestos-related cancer frequently marked by mutations of both NF2 and CDKN2A. We demonstrate that germline knockout of one allele of each of these genes causes accelerated onset and progression of asbestos-induced malignant mesothelioma compared with asbestos-exposed Nf2(+/-) or wild-type mice. Ascites from some Nf2(+/-);Cdkn2a(+/-) mice exhibited large tumor spheroids, and tail vein injections of malignant mesothelioma cells established from these mice, but not from Nf2(+/-) or wild-type mice, produced numerous tumors in the lung, suggesting increased metastatic potential of tumor cells from Nf2(+/-);Cdkn2a(+/-) mice. Intraperitoneal injections of malignant mesothelioma cells derived from Nf2(+/-);Cdkn2a(+/-) mice into severe combined immunodeficient mice produced tumors that penetrated the diaphragm and pleural cavity and harbored increased cancer stem cells (CSC). Malignant mesothelioma cells from Nf2(+/-);Cdkn2a(+/-) mice stained positively for CSC markers and formed CSC spheroids in vitro more efficiently than counterparts from wild-type mice. Moreover, tumor cells from Nf2(+/-);Cdkn2a(+/-) mice showed elevated c-Met expression/activation, which was partly dependent on p53-mediated regulation of miR-34a and required for tumor migration/invasiveness and maintenance of the CSC population. Collectively, these studies demonstrate in vivo that inactivation of Nf2 and Cdkn2a cooperate to drive the development of highly aggressive malignant mesotheliomas characterized by enhanced tumor spreading capability and the presence of a CSC population associated with p53/miR-34a-dependent activation of c-Met. These findings suggest that cooperativity between losses of Nf2 and Cdkn2a plays a fundamental role in driving the highly aggressive tumorigenic phenotype considered to be a hallmark of malignant mesothelioma.

The therapeutic efficacy of S-1 against orthotopically implanted human pleural mesothelioma cells in severe combined immunodeficient mice

Purpose

Malignant pleural mesothelioma (MPM) is a highly lethal neoplasm. S-1 has been developed as a novel oral antineoplastic agent based on the modulation of 5-fluorouracil (5-FU) bioactivity. This study was conducted to investigate the preclinical therapeutic effect of S-1 on MPM.

Methods

We used three human MPM cell lines, Y-MESO-14, NCI-H290 and MSTO-211H. In vitro proliferation of human MPM cells was determined by MTT assay. Human MPM cells were orthotopically implanted into thoracic cavity of SCID mice. Tumor-bearing mice were treated with S-1 or vehicle.

Results

The combination of 5-FU and 5-chloro-2,4-dihydroxypyridine (CDHP) was more effective than 5-FU alone in inhibiting MPM cell proliferation in vitro. This combination was most effective in Y-MESO-14 cells, which co-expressed high protein level of dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP). In vivo data showed that treatment with S-1 significantly reduced thoracic tumors and pleural effusion produced by Y-MESO-14 cells. Moreover, treatment with S-1 prolonged the survival of Y-MESO-14 cell-bearing SCID mice.

Conclusions

We demonstrated that S-1 was effective for inhibiting the proliferation of MPM cells, particularly with both DPD and TP expressions, suggesting that S-1 might be therapeutically effective for control of MPM.

Sorafenib inhibits ERK1/2 and MCL-1(L) phosphorylation levels resulting in caspase-independent cell death in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive, rapidly progressive malignancy without effective therapy. We evaluate sorafenib efficacy and impact on the cellular pro-survival machinery in vitro, efficacy of sorafenib as monotherapy and in combination with the naturally occurring death receptor agonist, TRAIL using human MPM cell lines, MSTO-211H, M30, REN, H28, H2052 and H2452. In vitro studies of the six MPM lines demonstrated single agent sensitivity to the multikinase inhibitor sorafenib and resistance to TRAIL. H28 and H2452 demonstrated augmented apoptosis with the addition of TRAIL to sorafenib in vitro. Treated cell lines demonstrated sorafenib-induced rapid dephosphorylation of AKT followed shortly by near complete dephosphorylation of the constitutively phosphorylated ERK1/2. Sorafenib therapy also decreased phosphorylation of B-Raf and mTOR in several cell lines. Within 3 h of sorafenib treatment, a number of known pro-survival molecules were dephosphorylated and/or downregulated in expression including MCL-1(L), c-FLIP(L), survivin and cIAP(1). These changes and eventual cell death did not elicit significant caspase-3 activation or PARP cleavage and pretreatment with the pan-caspase inhibitor, Z-VAD-FMK, did not block sorafenib efficacy but did block the effect of TRAIL monotherapy. Pre-treatment with Z-VAD-FMK did not block the synergistic effect of TRAIL and sorafenib in H28. In summary, single agent treatment with sorafenib results in widespread inhibition of the pro-survival machinery in vitro leading to cell death via a primarily caspase-independent mechanism. Combining sorafenib therapy with TRAIL, may be useful in order to provide a more efficient death signal and this synergistic effect appears to be caspase-independent. Pilot in vivo data demonstrates promising evidence of therapeutic efficacy in human tumor bearing xenograft nu/nu mice. We document single agent activity of sorafenib against MPM, unravel novel effects of sorafenib on anti-apoptotic signaling mediators, and suggest the combination of sorafenib plus TRAIL as possible therapy for clinical testing in MPM.

Immunotherapy and radiation therapy for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a particularly aggressive thoracic malignancy with limited survival following combination chemotherapy. As a result, there has been increased interested in immunotherapy for mesothelioma, both in the first-line and salvage settings. Early investigations of interleukin-2 (IL-2) and interferon alfa-2a/b have been limited by modest response rates and toxicity, whereas cytokine gene therapy is currently being investigated and shows early promise. The most prominent class of immunotherapies to be trialed with mesothelioma in the past half-decade has been immune checkpoint inhibitors (CPI). Early results are encouraging, particularly for agents targeting the PD-1/PD-L1 pathways. With the increasing recognition of the immune potential of mesothelioma, interest in the immunomodulatory properties of radiation therapy has emerged. The combination of immunotherapy and radiation therapy may allow for complimentary immunologic effects that can enhance antitumor response. This article reviews the existing literature on the efficacy of immunotherapy for MPM, describes the rationale for combining immunotherapy with radiation therapy, and discusses early literature on this treatment combination.