Expression and prognostic significance of hypoxia-inducible factor 1α (HIF-1α) in malignant pleural mesothelioma (MPM)

Chronic Inflammation, Oxidative Stress and Metabolic Plasticity: Three Players Driving the Pro-Tumorigenic Microenvironment in Malignant Mesothelioma

Malignant pleural mesothelioma (MPM) is a lethal and rare cancer, even if its incidence has continuously increased all over the world. Asbestos exposure leads to the development of mesothelioma through multiple mechanisms, including chronic inflammation, oxidative stress with reactive oxygen species (ROS) generation, and persistent aberrant signaling. Together, these processes, over the years, force normal mesothelial cells' transformation. Chronic inflammation supported by "frustrated" macrophages exposed to asbestos fibers is also boosted by the release of pro-inflammatory cytokines, chemokines, growth factors, damage-associated molecular proteins (DAMPs), and the generation of ROS. In addition, the hypoxic microenvironment influences MPM and immune cells' features, leading to a significant rewiring of metabolism and phenotypic plasticity, thereby supporting tumor aggressiveness and modulating infiltrating immune cell responses. This review provides an overview of the complex tumor-host interactions within the MPM tumor microenvironment at different levels, i.e., soluble factors, metabolic crosstalk, and oxidative stress, and explains how these players supporting tumor transformation and progression may become potential and novel therapeutic targets in MPM.

The Genes-Stemness-Secretome Interplay in Malignant Pleural Mesothelioma: Molecular Dynamics and Clinical Hints

MPM has a uniquely poor somatic mutational landscape, mainly driven by environmental selective pressure. This feature has dramatically limited the development of effective treatment. However, genomic events are known to be associated with MPM progression, and specific genetic signatures emerge from the exceptional crosstalk between neoplastic cells and matrix components, among which one main area of focus is hypoxia. Here we discuss the novel therapeutic strategies focused on the exploitation of MPM genetic asset and its interconnection with the surrounding hypoxic microenvironment as well as transcript products and microvesicles representing both an insight into the pathogenesis and promising actionable targets.

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.

Splicing deregulation, microRNA and Notch aberrations: fighting the three-headed dog to overcome drug resistance in malignant mesothelioma

INTRODUCTION

Malignant mesothelioma (MMe) is an aggressive rare cancer of the mesothelium, associated with asbestos exposure. MMe is currently an incurable disease at all stages mainly due to resistance to treatments. It is therefore necessary to elucidate key mechanisms underlying chemoresistance, in an effort to exploit them as novel therapeutic targets.

AREAS COVERED

Chemoresistance is frequently elicited by microRNA (miRNA) alterations and splicing deregulations. Indeed, several miRNAs, such as miR-29c, have been shown to exert oncogenic or oncosuppressive activity. Alterations in the splicing machinery might also be involved in chemoresistance. Moreover, the Notch signaling pathway, often deregulated in MMe, plays a key role in cancer stem cells formation and self-renewal, leading to drug resistance and relapses.

EXPERT OPINION

The prognosis of MMe in patients varies among different tumors and patient characteristics, and novel biomarkers and therapies are warranted. This work aims at giving an overview of MMe, with a special focus on state-of-the-art treatments and new therapeutic strategies against vulnerabilities emerging from studies on epigenetics factors. Besides, this review is also the first to discuss the interplay between miRNAs and alternative splicing as well as the role of Notch as new promising frontiers to overcome drug resistance in MMe.

Interfering with Tumor Hypoxia for Radiotherapy Optimization

Hypoxia in solid tumors is an important predictor of treatment resistance and poor clinical outcome. The significance of hypoxia in the development of resistance to radiotherapy has been recognized for decades and the search for hypoxia-targeting, radiosensitizing agents continues. This review summarizes the main hypoxia-related processes relevant for radiotherapy on the subcellular, cellular and tissue level and discusses the significance of hypoxia in radiation oncology, especially with regard to the current shift towards hypofractionated treatment regimens. Furthermore, we discuss the strategies to interfere with hypoxia for radiotherapy optimization, and we highlight novel insights into the molecular pathways involved in hypoxia that might be utilized to increase the efficacy of radiotherapy.

Genomics and Functional Genomics of Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a rare, aggressive cancer of the mesothelial cells lining the pleural surface of the chest wall and lung. The etiology of MPM is strongly associated with prior exposure to asbestos fibers, and the median survival rate of the diagnosed patients is approximately one year. Despite the latest advancements in surgical techniques and systemic therapies, currently available treatment modalities of MPM fail to provide long-term survival. The increasing incidence of MPM highlights the need for finding effective treatments. Targeted therapies offer personalized treatments in many cancers. However, targeted therapy in MPM is not recommended by clinical guidelines mainly because of poor target definition. A better understanding of the molecular and cellular mechanisms and the predictors of poor clinical outcomes of MPM is required to identify novel targets and develop precise and effective treatments. Recent advances in the genomics and functional genomics fields have provided groundbreaking insights into the genomic and molecular profiles of MPM and enabled the functional characterization of the genetic alterations. This review provides a comprehensive overview of the relevant literature and highlights the potential of state-of-the-art genomics and functional genomics research to facilitate the development of novel diagnostics and therapeutic modalities in MPM.

Impact of hypoxia on chemoresistance of mesothelioma mediated by the proton-coupled folate transporter, and preclinical activity of new anti-LDH-A compounds

BACKGROUND

Expression of proton-coupled folate transporter (PCFT) is associated with survival of mesothelioma patients treated with pemetrexed, and is reduced by hypoxia, prompting studies to elucidate their correlation.

METHODS

Modulation of glycolytic gene expression was evaluated by PCR arrays in tumour cells and primary cultures growing under hypoxia, in spheroids and after PCFT silencing. Inhibitors of lactate dehydrogenase (LDH-A) were tested in vitro and in vivo. LDH-A expression was determined in tissue microarrays of radically resected malignant pleural mesothelioma (MPM, N = 33) and diffuse peritoneal mesothelioma (DMPM, N = 56) patients.

RESULTS

Overexpression of hypoxia marker CAIX was associated with low PCFT expression and decreased MPM cell growth inhibition by pemetrexed. Through integration of PCR arrays in hypoxic cells and spheroids and following PCFT silencing, we identified the upregulation of LDH-A, which correlated with shorter survival of MPM and DMPM patients. Novel LDH-A inhibitors enhanced spheroid disintegration and displayed synergistic effects with pemetrexed in MPM and gemcitabine in DMPM cells. Studies with bioluminescent hypoxic orthotopic and subcutaneous DMPM athymic-mice models revealed the marked antitumour activity of the LDH-A inhibitor NHI-Glc-2, alone or combined with gemcitabine.

CONCLUSIONS

This study provides novel insights into hypoxia/PCFT-dependent chemoresistance, unravelling the potential prognostic value of LDH-A, and demonstrating the preclinical activity of LDH-A inhibitors.

Malignant Pleural Mesothelioma: Genetic and Microenviromental Heterogeneity as an Unexpected Reading Frame and Therapeutic Challenge

Mesothelioma is a malignancy of serosal membranes including the peritoneum, pleura, pericardium and the tunica vaginalis of the testes. Malignant mesothelioma (MM) is a rare disease with a global incidence in countries like Italy of about 1.15 per 100,000 inhabitants. Malignant Pleural Mesothelioma (MPM) is the most common form of mesothelioma, accounting for approximately 80% of disease. Although rare in the global population, mesothelioma is linked to industrial pollutants and mineral fiber exposure, with approximately 80% of cases linked to asbestos. Due to the persistent asbestos exposure in many countries, a worldwide progressive increase in MPM incidence is expected for the current and coming years. The tumor grows in a loco-regional pattern, spreading from the parietal to the visceral pleura and invading the surrounding structures that induce the clinical picture of pleural effusion, pain and dyspnea. Distant spreading and metastasis are rarely observed, and most patients die from the burden of the primary tumor. Currently, there are no effective treatments for MPM, and the prognosis is invariably poor. Some studies average the prognosis to be roughly one-year after diagnosis. The uniquely poor mutational landscape which characterizes MPM appears to derive from a selective pressure operated by the environment; thus, inflammation and immune response emerge as key players in driving MPM progression and represent promising therapeutic targets. Here we recapitulate current knowledge on MPM with focus on the emerging network between genetic asset and inflammatory microenvironment which characterize the disease as amenable target for novel therapeutic approaches.

Antiangiogeneic Strategies in Mesothelioma

There is a strong rationale for inhibiting angiogenesis in mesothelioma. Vascular endothelial growth factor (VEGF) is an autocrine growth factor in mesothelioma and a potent mitogen for mesothelial cells. Further, the abnormal tumor vasculature promotes raised interstitial pressure and hypoxia, which may be detrimental to both penetration and efficacy of anticancer agents. Antiangiogenic agents have been trialed in mesothelioma for close to two decades, with early phase clinical trials testing vascular targeting agents, the VEGF-A targeting monoclonal antibody bevacizumab, and numerous tyrosine kinase inhibitors, many with multiple targets. None of these have shown efficacy which has warranted further development as single agents in any line of therapy. Whilst a randomized phase II trial combining the multitargeted tyrosine kinase inhibitor nintedanib with platinum/pemetrexed chemotherapy was positive, these results were not confirmed in a subsequent phase III study. The combination of cisplatin and pemetrexed with bevacizumab, in appropriately selected patients, remains the only anti-angiogenic combination showing efficacy in mesothelioma. Extensive efforts to identify biomarkers of response have not yet been successful.

The Immune Microenvironment in Mesothelioma: Mechanisms of Resistance to Immunotherapy

Although mesothelioma is the consequence of a protracted immune response to asbestos fibers and characterized by a clear immune infiltrate, novel immunotherapy approaches show less convincing results as compared to those seen in melanoma and non-small cell lung cancer. The immune suppressive microenvironment in mesothelioma is likely contributing to this therapy resistance. Therefore, it is important to explore the characteristics of the tumor microenvironment for explanations for this recalcitrant behavior. This review describes the stromal, cytokine, metabolic, and cellular milieu of mesothelioma, and attempts to make connection with the outcome of immunotherapy trials.

What can independent research for mesothelioma achieve to treat this orphan disease?

Introduction: Malignant pleural mesothelioma (MPM) is a rare neoplasm with a poor prognosis, as current therapies are ineffective. Despite the increased understanding of the molecular biology of mesothelioma, there is still a lack of drugs that dramatically enhance patient survival. Area Covered: This review discusses recent and complete clinical trials supported by the NIH, other U.S. Federal agencies, universities and organizations found on clinicaltrials.gov. Firstly, chemotherapy-based trials are described, followed by immunotherapy and multitargeted therapy. Then we introduce drug repositioning and the use of drug docking as tools to find new interesting molecules. Finally, we highlight potential molecular pathways that may play a role in mesothelioma biology and therapy. Expert Opinion: Numerous biases are present in the clinical trials due to a restricted number of cases, inappropriate endpoints and inaccurate stratification of patients which delay the finding of a treatment for MPM. The most crucial issue of independent research for MPM is the lack of more substantive funding to translate these findings to the clinical setting. However, this approach is not necessarily scientific given the low mutational load of mesothelioma relative to other cancers, and therefore patients need a more solid rationale to have a good chance of successful treatment.

Hypoxia promotes acquisition of aggressive phenotypes in human malignant mesothelioma

BACKGROUND

Hypoxia is a hallmark of the solid tumor microenvironment and is associated with poor outcomes in cancer patients. The present study was performed to investigate mechanisms underlying the hypoxia-induced phenotypic changes using human malignant mesothelioma (HMM) cells.

METHODS

Hypoxic conditions were achieved by incubating HMM cells in the air chamber. The effect of hypoxia on phenotype changes in HMM cells was investigated by performing in vitro clonogenicity, drug resistance, migration, and invasion assays. Signaling pathways and molecules involved in the more aggressive behaviors of HMM cells under hypoxia were investigated. A two-tailed unpaired Student's t-test or one-way ANOVA with Bonferroni post-test correction was used in this study.

RESULTS

Hypoxic conditions upregulated hypoxia-inducible factor 1 alpha (HIF-1α) and HIF-2α in parallel with the upregulation of its target, Glut-1, in HMM cells. In vitro clonogenicity of HMM cells was significantly increased in hypoxic conditions, but the proliferation of cells at a high density in hypoxia was lower than that in normoxic conditions. The expression levels of HIF-2α and Oct4 were increased in hypoxic HMM cells. The percentage of cells with high CD44 expression was significantly higher in HMM cells cultured in hypoxia than those cultured in normoxia. Hypoxia significantly enhanced the resistance of HMM cells to cisplatin, which occurred through cytoprotection against cisplatin-induced apoptosis. While cisplatin treatment decreased the ratio of Bcl-2 to Bax in normoxic condition, hypoxia conversely increased the ratio in HMM cells treated with cisplatin. Hypoxia increased the mobility and invasiveness of HMM cells. Epithelial to mesenchymal transition was promoted, which was indicated by the repression of E-cadherin and the concomitant increase of vimentin in HMM cells.

CONCLUSIONS

The data illustrated that hypoxic conditions augmented the aggressive phenotypes of HMM cells at the biological and molecular levels. The present study provides valuable background information beginning to understand aggressiveness of HMM in tumor microenvironments, suggesting that a control measure for tumor hypoxia may be an effective therapeutic strategy to reduce the aggressiveness of cancer cells in HMM patients.

The Effect of Aquaporin 1-Inhibition on Vasculogenic Mimicry in Malignant Mesothelioma

Malignant mesothelioma (MM) is an aggressive malignancy of the serosal membranes, with poor overall survival and quality of life. Limited targeted treatment strategies exist due to restricted knowledge of pathogenic pathways. Vasculogenic mimicry (VM) is a newly described phenomenon associated with increased aggressiveness in other malignancies, and has been characterized in MM. Normal mesothelium expresses aquaporin 1 (AQP1) and retained expression has been associated with improved survival in MM. AQP1 is expressed by normal vascular endothelium and is involved in mediating MM cell motility and proliferation. We investigated the role of AQP1 in VM, and its interaction with the pro-angiogenic factor vascular endothelial growth factor A (VEGFA), which is variably expressed in MM. Matrigel VM assays were performed using NCI-H226 and NCI-H28 MM cell lines and primary cells in hypoxia and normoxia. The synthetic blocker AqB050 and siRNA were used to inhibit AQP1, and bevacizumab was used to inhibit VEGF. Inhibition of AQP1 resulted in increased VEGFA secretion by MM cells and reduced VM in MM cell lines in hypoxia but not normoxia. No change in VM was seen in MM primary cells. Combined inhibition of AQP1 and VEGF had no effect on VM in normoxia. In a heterotopic xenograft mouse model, AqB050 treatment did not alter vessel formation. AQP1 may interact with VEGFA and play a role in VM, especially under hypoxic conditions, but the heterogeneity of MM cells may result in different dominant pathways between patients.

Targeting mesothelin receptors with drug-loaded bacterial nanocells suppresses human mesothelioma tumour growth in mouse xenograft models

Human malignant mesothelioma is a chemoresistant tumour that develops from mesothelial cells, commonly associated with asbestos exposure. Malignant mesothelioma incidence rates in European countries are still rising and Australia has one of the highest burdens of malignant mesothelioma on a population basis in the world. Therapy using systemic delivery of free cytotoxic agents is associated with many undesirable side effects due to non-selectivity, and is thus dose-limited which limits its therapeutic potential. Therefore, increasing the selectivity of anti-cancer agents has the potential to dramatically enhance drug efficacy and reduce toxicity. EnGeneIC Dream Vectors (EDV) are antibody-targeted nanocells which can be loaded with cytotoxic drugs and delivered to specific cancer cells via bispecific antibodies (BsAbs) which target the EDV and a cancer cell-specific receptor, simultaneously. BsAbs were designed to target doxorubicin-loaded EDVs to cancer cells via cell surface mesothelin (MSLN). Flow cytometry was used to investigate cell binding and induction of apoptosis, and confocal microscopy to visualize internalization. Mouse xenograft models were used to assess anti-tumour effects in vivo, followed by immunohistochemistry for ex vivo evaluation of proliferation and necrosis. BsAb-targeted, doxorubicin-loaded EDVs were able to bind to and internalize within mesothelioma cells in vitro via MSLN receptors and induce apoptosis. In mice xenografts, the BsAb-targeted, doxorubicin-loaded EDVs suppressed the tumour growth and also decreased cell proliferation. Thus, the use of MSLN-specific antibodies to deliver encapsulated doxorubicin can provide a novel and alternative modality for treatment of mesothelioma.

Malignant Mesothelioma, BAP1 Immunohistochemistry, and VEGFA: Does BAP1 Have Potential for Early Diagnosis and Assessment of Prognosis?

Malignant mesothelioma (MM) is an aggressive malignancy of the serosal membranes. Early diagnosis and accurate prognostication remain problematic. BAP1 is a tumour suppressor gene commonly mutated in MM. Germline BAP1 mutation has been associated with early onset and less aggressive disease compared with sporadic MM. Sporadic BAP1 mutations are common and are associated with improved survival in MM, contrary to other malignancies. This study investigated the prognostic role of BAP1 in matched cytology and surgical specimens and aimed to investigate the association between BAP1 and the established prognostic marker VEGFA from a cohort of 81 patients. BAP1 mutation was found in 58% of histology and 59% of cytology specimens. Loss of BAP1 expression in both surgical and cytology specimens was significantly associated with poorer survival in a multivariate analysis when controlling for known prognostic indicators. Increased levels of VEGFA in pleural effusions were associated with poor survival. We conclude that the prognostic significance of BAP1 mutations in MM cannot be determined in isolation of other prognostic factors, which may vary between patients. Pathologists should employ caution when commenting on prognostic implications of BAP1 status of MM patients in diagnostic pathology reports, but it may be useful for early diagnosis.

A specific inhibitor of lactate dehydrogenase overcame the resistance toward gemcitabine in hypoxic mesothelioma cells, and modulated the expression of the human equilibrative transporter-1

Malignant pleural mesothelioma (MPM) is a very hypoxic malignancy, and hypoxia has been associated with resistance towards gemcitabine. The muscle-isoform of lactate dehydrogenase (LDH-A) constitutes a major checkpoint for the switch to anaerobic glycolysis. Therefore we investigated the combination of a new LDH-A inhibitor (NHI-1) with gemcitabine in MPM cell lines. Under hypoxia (O₂ tension of 1%) the cell growth inhibitory effects of gemcitabine, were reduced, as demonstrated by a 5- to 10-fold increase in IC₅₀s. However, the simultaneous addition of NHI-1 was synergistic (combination index < 1). Flow cytometry demonstrated that hypoxia caused a G1 arrest, whereas the combination of NHI-1 significantly increased gemcitabine-induced cell death. Finally, the mRNA expression levels of the human equilibrative transporter-1 (hENT1) were significantly down-regulated under hypoxia, but treatment with NHI-1 was associated with a recovery of hENT1 expression. In conclusion, our data show that hypoxia increased MPM resistance to gemcitabine. However, cell death induction and modulation of the key transporter in gemcitabine uptake may contribute to the synergistic interaction of gemcitabine with the LDH-A inhibitor NHI-1 and support further studies for the rational development of this combination.

Switching off malignant mesothelioma: exploiting the hypoxic microenvironment

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

MDM2 and HIF1alpha expression levels in different histologic subtypes of malignant pleural mesothelioma: correlation with pathological and clinical data

Malignant pleural mesothelioma (MPM) is an aggressive tumor with poor prognosis and limited treatment options. Sarcomatoid/biphasic mesotheliomas are characterized by more aggressive behaviour and a poorer prognosis compared with the epithelioid subtype. To date prognostic and tailored therapeutic biomarkers are lacking. The present study analyzed the expression levels of MDM2 and HIF1alpha in different histologic subtypes from chemonaive MPM patients. Diagnostic biopsies of MPM patients from four Italian cancer centers were centrally collected and analyzed. MDM2 and HIF1alpha expression levels were investigated through immunohistochemistry and RT-qPCR. Pathological assessment of necrosis, inflammation and proliferation index was also performed. Molecular markers, pathological features and clinical characteristics were correlated to overall survival (OS) and progression free survival (PFS). Sixty MPM patients were included in the study (32 epithelioid and 28 non-epithelioid). Higher levels of MDM2 (p < 0.001), HIF1alpha (p = 0.013), necrosis (p = 0.013) and proliferation index (p < 0.001) were seen mainly in sarcomatoid/biphasic subtypes. Higher levels of inflammation were significantly associated with epithelioid subtype (p = 0.044). MDM2 expression levels were correlated with HIF1alpha levels (p = 0.0001), necrosis (p = 0.008) and proliferation index (p = 0.009). Univariate analysis showed a significant correlation of non-epithelioid histology (p = 0.04), high levels of necrosis (p = 0.037) and proliferation index (p = 0.0002) with shorter PFS. Sarcomatoid/biphasic and epithelioid mesotheliomas showed different MDM2 and HIF1alpha expression levels and were characterized by different levels of necrosis, proliferation and inflammation. Further studies are warranted to confirm a prognostic and predictive role of such markers and features.

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.

miR-193a-3p is a potential tumor suppressor in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an asbestos-induced cancer with poor prognosis that displays characteristic alterations in microRNA expression. Recently it was reported that the expression of a subset of microRNAs can distinguish between MPM and adenocarcinoma of the lung. However, the functional importance of these changes has yet to be investigated. We compared expression of miR-192, miR-193a-3p and the miR-200 family in normal pleura and MPM tumor specimens and found a statistically significant reduction in the levels of miR-193a-3p (3.1-fold) and miR-192 (2.8-fold) in MPM. Transfection of MPM cells with a miR-193a-3p mimic resulted in inhibition of growth and an induction of apoptosis and necrosis in vitro. The growth inhibitory effects of miR-193a-3p were associated with a decrease in MCL1 expression and were recapitulated by RNAi-mediated MCL1 silencing. Targeted delivery of miR-193a-3p mimic using EDV minicells inhibited MPM xenograft tumour growth, and was associated with increased apoptosis. In conclusion, miR-193a-3p appears to have importance in the biology of MPM and may represent a target for therapeutic intervention.

Critical review about MDM2 in cancer: Possible role in malignant mesothelioma and implications for treatment

The tumor suppressor p53 regulates genes involved in DNA repair, metabolism, cell cycle arrest, apoptosis and senescence. p53 is mutated in about 50% of the human cancers, while in tumors with wild-type p53 gene, the protein function may be lost because of overexpression of Murine Double Minute 2 (MDM2). MDM2 targets p53 for ubiquitylation and proteasomal degradation. p53 reactivation through MDM2 inhibitors seems to be a promising strategy to sensitize p53 wild-type cancer cells to apoptosis. Moreover, additional p53-independent molecular functions of MDM2, such as neoangiogenesis promotion, have been suggested. Thus, MDM2 might be a target for anticancer treatment because of its antiapoptotic and proangiogenetic role. Malignant pleural mesothelioma (MPM) is an aggressive asbestos-related tumor where wild-type p53 might be present. The present review gives a complete landscape about the role of MDM2 in cancer pathogenesis, prognosis and treatment, with particular focus on Malignant Pleural Mesothelioma.

Hydrogen peroxide promotes epithelial to mesenchymal transition and stemness in human malignant mesothelioma cells

Reactive oxygen species (ROS) are known to promote mesothelial carcinogenesis that is closely associated with asbestos fibers and inflammation. Epithelial to mesenchymal cell transition (EMT) is an important process involved in the progression of tumors, providing cancer cells with aggressiveness. The present study was performed to determine if EMT is induced by H2O2 in human malignant mesothelioma (HMM) cells. Cultured HMM cells were treated with H2O2, followed by measuring expression levels of EMT-related genes and proteins. Immunohistochemically, TWIST1 expression was confined to sarcomatous cells in HMM tissues, but not in epithelioid cells. Treatment of HMM cells with H2O2 promoted EMT, as indicated by increased expression levels of vimentin, SLUG and TWIST1, and decreased E-cadherin expression. Expression of stemness genes such as OCT4, SOX2 and NANOG was also significantly increased by treatment of HMM cells with H2O2. Alteration of these genes was mediated via activation of hypoxia inducible factor 1 alpha (HIF-1α) and transforming growth factor beta 1 (TGF-β1). Considering that treatment with H2O2 results in excess ROS, the present study suggests that oxidative stress may play a critical role in HMM carcinogenesis by promoting EMT processes and enhancing the expression of stemness genes.

Microspheres targeted with a mesothelin antibody and loaded with doxorubicin reduce tumor volume of human mesotheliomas in xenografts

Background

Malignant mesotheliomas (MMs) are chemoresistant tumors related to exposure to asbestos fibers. The long latency period of MM (30-40 yrs) and heterogeneity of tumor presentation make MM difficult to diagnose and treat at early stages. Currently approved second-line treatments following surgical resection of MMs include a combination of cisplatin or carboplatin (delivered systemically) and pemetrexed, a folate inhibitor, with or without subsequent radiation. The systemic toxicities of these treatments emphasize the need for more effective, localized treatment regimens.

Methods

Acid-prepared mesoporous silica (APMS) microparticles were loaded with doxorubicin (DOX) and modified externally with a mesothelin (MB) specific antibody before repeated intraperitoneal (IP) injections into a mouse xenograft model of human peritoneal MM. The health/weight of mice, tumor volume/weight, tumor necrosis and cell proliferation were evaluated in tumor-bearing mice receiving saline, DOX high (0.2 mg/kg), DOX low (0.05 mg/kg), APMS-MB, or APMS-MB-DOX (0.05 mg/kg) in saline.

Results

Targeted therapy (APMS-MB-DOX at 0.05 mg/kg) was more effective than DOX low (0.05 mg/kg) and less toxic than treatment with DOX high (0.2 mg/kg). It also resulted in the reduction of tumor volume without loss of animal health and weight, and significantly decreased tumor cell proliferation. High pressure liquid chromatography (HPLC) of tumor tissue confirmed that APMS-MB-DOX particles delivered DOX to target tissue.

Conclusions

Data suggest that targeted therapy results in greater chemotherapeutic efficacy with fewer adverse side effects than administration of DOX alone. Targeted microparticles are an attractive option for localized drug delivery.

CD146 and insulin-like growth factor 2 mRNA-binding protein 3 predict prognosis of asbestos-induced rat mesothelioma

Malignant mesothelioma (MM), which is associated with asbestos exposure, is one of the most deadly tumors in humans. Early MM is concealed in the serosal cavities and lacks specific clinical symptoms. For better treatment, early detection and prognostic markers are necessary. Recently, CD146 and insulin-like growth factor 2 mRNA-binding protein 3 (IMP3) were reported as possible positive markers of MM to distinguish from reactive mesothelia in humans. However, their application on MM of different species and its impact on survival remain to be elucidated. To disclose the utility of these molecules as early detection and prognostic markers of MM, we injected chrysotile or crocidolite intraperitoneally to rats, thus obtaining 26 peritoneal MM and establishing 11 cell lines. We immunostained CD146 and IMP3 using paraffin-embedded tissues and cell blocks and found CD146 and IMP3 expression in 58% (15/26) and 65% (17/26) of MM, respectively, but not in reactive mesothelia. There was no significant difference in both immunostainings for overexpression among the three histological subtypes of MM and the expression of CD146 and IMP3 was proportionally associated. Furthermore, the overexpression of CD146 and/or IMP3 was proportionally correlated with shortened survival. These results suggest that CD146 and IMP3 are useful diagnostic and prognostic markers of MM.

Curcumin reverses cis-platin resistance and promotes human lung adenocarcinoma A549/DDP cell apoptosis through HIF-1α and caspase-3 mechanisms

Curcumin, a yellow pigment derived from Curcuma longa Linn, has been favored by the Eastern as dietary ingredients for centuries. During the past decade, extensive investigations have revealed curcumin sensitized various chemotherapeutic agents in human breast, colon, pancreas, gastric, liver, brain and hematological malignant disorders in vivo and in vitro. Several pathways and specific targets including NF-κB, STAT3, COX-2, Akt and multidrug resistant protein have been identified to facilitate curcumin as a chemosensitizer. Recent studies suggest HIF-1α participated in the development of drug resistance in cancer cells and targeting HIF-1α either by RNAi or siRNA successfully overcame chemotherapeutic resistance. To investigate the mechanism basis of curcumin as a chemosensitizer in lung cancer, we examined curcumin's effects on HIF-1α in cis-platin (DDP) sensitive A549 and resistant A549/DDP cell lines by RT-PCR and Western blot. HIF-1α in A549/DDP cells was found to be overexpressed at both mRNA and protein levels together with a poor response to DDP. Results from transient transfection and flow cytometry showed the HIF-1α abnormality contributed to DDP resistance in A549/DDP lung cancer cells. Combined curcumin and DDP treatment markedly inhibited A549/DDP cells proliferation, reversed DDP resistance and triggered apoptotic death by promoting HIF-1α degradation and activating caspase-3, respectively. Expression of HIF-1α-dependent P-gp also seemed to decrease as response to curcumin in a dose-dependent manner. Our findings shed light on drug resistant reversing effect of curcumin in lung cancer cells by inhibiting HIF-1α expression and activating caspase-3.

Investigational approaches for mesothelioma

Malignant pleural mesothelioma (MPM) is a rare, aggressive tumor with a poor prognosis. In view of the poor survival benefit from first-line chemotherapy and the lack of subsequent effective treatment options, there is a strong need for the development of more effective treatment approaches for patients with MPM. This review will provide a comprehensive state of the art of new investigational approaches for mesothelioma. In an introductory section, the etiology, epidemiology, natural history, and standard of care treatment for MPM will be discussed. This review provide an update of the major clinical trials that impact mesothelioma treatment, discuss the impact of novel therapeutics, and provide perspective on where the clinical research in mesothelioma is moving. The evidence was collected by a systematic analysis of the literature (2000-2011) using the databases Medline (National Library of Medicine, USA), Embase (Elsevier, Netherlands), Cochrane Library (Great Britain), National Guideline Clearinghouse (USA), HTA Database (International Network of Agencies for Health Technology Assessment - INAHTA), NIH database (USA), International Pleural Mesothelioma Program - WHOLIS (WHO Database), with the following keywords and filters: mesothelioma, guidelines, treatment, surgery, chemotherapy, radiotherapy, review, investigational, drugs. Currently different targeted therapies and biologicals are under investigation for MPM. It is important that the molecular biologic research should first focus on mesothelioma-specific pathways and biomarkers in order to have more effective treatment options for this disease. The use of array technology will be certainly an implicit gain in the identification of new potential prognostic or biomarkers or important pathways in the MPM pathogenesis. Probably a central mesothelioma virtual tissue bank may contribute to the ultimate goal to identify druggable targets and to develop personalized treatment for the MPM patients.

Advances in the biology of malignant pleural mesothelioma

Malignant pleural mesothelioma is a highly aggressive cancer with a very poor prognosis. Although the mechanism of carcinogenesis is not fully understood, approximately 80% of malignant pleural mesothelioma can be attributed to asbestos fiber exposure. This disease is largely unresponsive to conventional chemotherapy or radiotherapy, and most patients die within 10-17 months of their first symptoms. Currently, malignant pleural mesothelioma therapy is guided by clinical stage and patient characteristics rather than by the histological or molecular features of the tumor. Several molecular pathways involved in malignant pleural mesothelioma have been identified; these include cell cycle regulation, apoptosis, growth factor pathways, and angiogenesis. Unfortunately, several agents targeting these processes, including erlotinib, gefitinib, and imatinib, have proven ineffective in clinical trials. A greater understanding of the molecular pathways involved in malignant pleural mesothelioma is needed to develop better diagnostics, therapeutics, and preventative measures. Moreover, understanding the biological basis of mesothelioma progression may facilitate personalized treatment approaches, and early identification of poor prognostic indicators may help reduce the heterogeneity of the clinical response. This paper reviews advances in the molecular biology of malignant pleural mesothelioma in terms of pathogenesis, the major molecular pathways and the associated therapeutic strategies, and the roles of biomarkers.

Increase in gene dosage is a mechanism of HIF-1alpha constitutive expression in head and neck squamous cell carcinomas

The HIF-1alpha protein plays a key role in the cellular response to hypoxia via transcriptional regulation of genes involved in erythropoiesis, angiogenesis, and metabolism. Overexpression of HIF-1alpha is commonly found in solid tumors in significant association with increased patient mortality and resistance to therapy. The predominant mode of HIF-1alpha regulation by hypoxia occurs at the level of protein stability. In addition to hypoxia, HIF-1alpha protein stability and synthesis is regulated by nonhypoxic signals such as inactivation of tumor suppressors and activation of oncogenes. Here, we show that an increase in gene dosage may contribute to HIF-1alpha mRNA and protein overexpression in a nonhypoxic environment in head and neck squamous cell carcinomas (HNSCC). Increased HIF-1alpha gene dosage was found in one out of five HNSCC-derived cell lines and three out of 27 HNSCC primary tumors. Significantly, increased gene dosage in those samples was associated with high HIF-1alpha mRNA and protein levels. Normoxic overexpression of HIF-1alpha protein in HNSCC-derived cell lines was also paralleled by higher expression levels of HIF-1alpha target genes. Array CGH analysis confirmed the copy number increase of HIF-1alpha gene and revealed that the gene is contained within a region of amplification at 14q23-q24.2 both in the cell line and primary tumors. In addition, FISH analysis revealed the presence of 11-13 copies on a tetraploid background in SCC2 cells. These data suggest that increased HIF-1alpha gene dosage is a mechanism of HIF-1alpha protein overexpression in HNSCC that possibly prepares the cells for a higher activity in an intratumoral hypoxic environment.

New diagnostic and molecular characteristics of malignant mesothelioma

Malignant mesothelioma is a primary cancer of the serosal cavities, an anatomic site that is also frequently affected by metastatic disease, predominantly from primary carcinomas of the lung, breast, and ovary. Advances in immunohistochemistry have resulted in improved diagnostic sensitivity and specificity in the differential diagnosis between metastatic adenocarcinoma and malignant mesothelioma in both cytological and histological material. Recently, the author's group applied high throughput technology to the identification of new markers that may aid in differentiating malignant mesothelioma from ovarian and peritoneal serous carcinoma, tumors with closely related histogenesis and antigenic profile. In addition to the improved tools available for serosal cancer diagnosis, knowledge regarding the biology of malignant mesothelioma has been accumulating in recent years. This review presents current data regarding the diagnostic and biological aspects of malignant mesothelioma.

Biomarkers for malignant pleural mesothelioma: current status

Malignant pleural mesothelioma (MPM) is an aggressive tumor with poor prognosis, whose main etiology is exposure to asbestos fibers. The incidence of MPM is anticipated to increase worldwide during the first half of this century. For various reasons, MPM is difficult to diagnose and is notoriously refractory to most treatments. However, recently two active chemotherapy regimens have been demonstrated to significantly increase survival in patients with MPM, and several therapeutic agents and strategies are currently under evaluation.Researchers have actively sought MPM biomarkers for more than 20 years. Biomarkers would be helpful in managing three clinical aspects of MPM: early diagnosis, prognosis, and treatment outcome prediction. The aims of the present review are to summarize the published and recently presented data on MPM biomarkers and to identify the prospects for future translational research projects.Among the 'classical' diagnostic biomarkers measured in biological fluids, such as cytokeratins and cell surface antigens, none discriminate patients with MPM from those with other malignancies and nonmalignant diseases. Osteopontin, soluble mesothelin, and megakaryocyte potentiating factor (MPF) appear to be the most promising of the recent biomarkers, but are still subject to some limitations. Osteopontin lacks specificity for mesothelioma, while both soluble mesothelin and MPF lack sensitivity for detecting non-epithelial subtypes. Panels consisting of a small set of biomarkers do not improve the diagnostic yield, and results from molecular profiling are too preliminary to be brought into daily clinical practice. While a large number of biomarkers have been assessed in biological fluids and tumor tissue for their prognostic value, none have had a widespread impact on clinical practice. In contrast, data concerning predictive biomarkers are very limited, even though they are most interesting from the perspective of clinicians.Additional prospective studies, in large and independent samples of patients, with rigorous statistical methodology and standardized laboratory techniques are now warranted to validate and define the precise value of diagnostic and prognostic MPM biomarkers. Future research efforts should focus on biomarkers predictive of the efficacy and toxicity of standard chemotherapy. Translational research should be systematically incorporated into the design of clinical trials assessing new targeted agents in MPM.

Opposite effects of Notch-1 and Notch-2 on mesothelioma cell survival under hypoxia are exerted through the Akt pathway

Malignant mesothelioma (MM) is a cancer of the lining of the lungs, heart, and intestine and is known to respond poorly to chemotherapy. Here we show that malignant mesothelial cells have an elevated Notch signaling pathway compared with normal human mesothelial cells. We studied the role of Notch in MM under normoxic and hypoxic conditions, the latter condition best recapitulating the MM microenvironment. Genetic and chemical modulation of the Notch pathway indicated that MM cells are dependent on Notch signaling. More specifically, this signaling was Notch-1 dependent as the result of its negative transcriptional regulation on phosphatase and tensin homologue (PTEN), which led to activation of the prosurvival phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway. Our study also provides evidence that whereas Notch-1 is elevated in the malignant setting, Notch-2 is diminished. This differential expression of the two Notch isoforms benefits cancer cell survival because reexpression of Notch-2 was toxic to MM cells. The mechanism of Notch-2 toxicity to MM cells countered that of Notch-1, as it was the result of positive transcriptional regulation of PTEN and inhibition of the PI3K/Akt/mTOR signaling pathway. These results provide new insight into the role of Notch in MM and suggest that Notch pathway inhibitors may be useful in the treatment of this deadly disease.

Targeting alpha7-nicotinic receptor for the treatment of pleural mesothelioma

Human malignant pleural mesothelioma (MPM) is a dreadful disease and there is still no standard therapy available for a consistent therapeutic approach. This research is aimed at the evaluation of the potential therapeutic effect of a specific nicotinic receptor (nAChR) antagonist, namely alpha-Cobratoxin (alpha-CbT). Its effectiveness was tested in mesothelioma cell lines and in primary mesothelioma cells in vitro, as well as in vivo, in orthotopically xenotransplanted NOD/SCID mice. Cells showed alpha7-nAChR expression and their growth was significantly inhibited by alpha-CbT. Severe induction of apoptosis was observed after exposure to alpha-CbT [IC(80-90)]. Apoptosis was characterised by: change in mitochondrial potential, caspase-3 cleavage, down-regulation of mRNA and protein for survivin, XIAP, IAP1, IAP2 and Bcl-XL, inhibition by caspase-3 inhibitor. In vivo, the alpha-CbT acute LD(50) was 0.15 mg/kg. The LD(100) [0.24 mg/kg] induced fatal respiratory failure and massive kidney necrosis. Phase II experiments with 0.12 ng/kg alpha-CbT (1/1000 of LD(10)) were done in 53 xenotransplanted mice, inhibiting tumour development as confirmed by chest X-ray examinations, autopsy and microscopical findings. The growth of human proliferating T lymphocytes and of mesothelial cells in primary culture was not affected by alpha-CbT. Non-immunogenic derivatives of the alpha-CbT molecule need to be developed for possible human use.

Advances in the systemic therapy of malignant pleural mesothelioma

Malignant pleural mesothelioma is an aggressive thoracic malignancy associated with exposure to asbestos, and its incidence is anticipated to increase during the first half of this century. Chemotherapy is the mainstay of treatment, yet sufficiently robust evidence to substantiate the current standard of care has emerged only in the past 5 years. This Review summarizes the evidence supporting the clinical activity of chemotherapy, discusses the use of end points for its assessment and examines the influence of clinical and biochemical prognostic factors on the natural history of malignant pleural mesothelioma. Early-phase clinical trials of second-line and novel agents are emerging from an increased understanding of mesothelioma cell biology. Coupled with high-quality translational research, such developments have real potential to improve the outlook of patients at a time of increasing incidence.

Genomic profiling of malignant pleural mesothelioma with array-based comparative genomic hybridization shows frequent non-random chromosomal alteration regions including JUN amplification on 1p32

Genome-wide array-based comparative genomic hybridization analysis of malignant pleural mesotheliomas (MPM) was carried out to identify regions that display DNA copy number alterations. Seventeen primary tumors and nine cell lines derived from 22 individuals were studied, some of them originating from the same patients. Regions of genomic aberrations observed in >20% of individuals were 1q, 5p, 7p, 8q24 and 20p with gains, and 1p36.33, 1p36.1, 1p21.3, 3p21.3, 4q22, 4q34-qter, 6q25, 9p21.3, 10p, 13q33.2, 14q32.13, 18q and 22q with losses. Two regions at 1p32.1 and 11q22 showed a high copy gain. The 1p32.1 region contained a protooncogene, JUN, and we further demonstrated overexpression of JUN with real-time polymerase chain reaction analysis. As MPM cell lines did not overexpress JUN, our findings suggested that induction of JUN expression was involved in the development of MPM cells in vivo, which also might result in gene amplification in a subset of MPM. Meanwhile, the most frequent alteration was the 9p21.3 deletion, which includes the p16(INK4a)/p14(ARF) locus. With polymerase chain reaction analysis, we determined the extent of the homozygous deletion regions of the p16(INK4a)/p14(ARF) locus in MPM cell lines, which indicated that the deletion regions varied among cell lines. Our results with array comparative genomic hybridization analysis provide new insights into the genetic background of MPM, and also give some clues to develop a new molecular target therapy for MPM.