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

Pleural mesothelioma (PMe): The evolving molecular knowledge of a rare and aggressive cancer

Mesothelioma is a type of late-onset cancer that develops in cells covering the outer surface of organs. Although it can affect the peritoneum, heart, or testicles, it mainly targets the lining of the lungs, making pleural mesothelioma (PMe) the most common and widely studied mesothelioma type. PMe is caused by exposure to fibres of asbestos, which when inhaled leads to inflammation and scarring of the pleura. Despite the ban on asbestos by most Western countries, the incidence of PMe is on the rise, also facilitated by a lack of specific symptomatology and diagnostic methods. Therapeutic options are also limited to mainly palliative care, making this disease untreatable. Here we present an overview of biological aspects underlying PMe by listing genetic and molecular mechanisms behind its onset, aggressive nature, and fast-paced progression. To this end, we report on the role of deubiquitinase BRCA1-associated protein-1 (BAP1), a tumour suppressor gene with a widely acknowledged role in the corrupted signalling and metabolism of PMe. This review aims to enhance our understanding of this devastating malignancy and propel efforts for its investigation.

Unraveling tumor microenvironment heterogeneity in malignant pleural mesothelioma identifies biologically distinct immune subtypes enabling prognosis determination

Background

Malignant pleural mesothelioma (MPM) is a rare and intractable disease exhibiting a remarkable intratumoral heterogeneity and dismal prognosis. Although immunotherapy has reshaped the therapeutic strategies for MPM, patients react with discrepant responsiveness.

Methods

Herein, we recruited 333 MPM patients from 5 various cohorts and developed an in-silico classification system using unsupervised Non-negative Matrix Factorization and Nearest Template Prediction algorithms. The genomic alterations, immune signatures, and patient outcomes were systemically analyzed across the external TCGA-MESO samples. Machine learning-based integrated methodology was applied to identify a gene classifier for clinical application.

Results

The gene expression profiling-based classification algorithm identified immune-related subtypes for MPMs. In comparison with the non-immune subtype, we validated the existence of abundant immunocytes in the immune subtype. Immune-suppressed MPMs were enriched with stroma fraction, myeloid components, and immunosuppressive tumor-associated macrophages (TAMs) as well exhibited increased TGF-β signature that informs worse clinical outcomes and reduced efficacy of anti-PD-1 treatment. The immune-activated MPMs harbored the highest lymphocyte infiltration, growing TCR and BCR diversity, and presented the pan-cancer immune phenotype of IFN-γ dominant, which confers these tumors with better drug response when undergoing immune checkpoint inhibitor (ICI) treatment. Genetically, BAP1 mutation was most commonly found in patients of immune-activated MPMs and was associated with a favorable outcome in a subtype-specific pattern. Finally, a robust 12-gene classifier was generated to classify MPMs with high accuracy, holding promise value in predicting patient survival.

Conclusions

We demonstrate that the novel classification system can be exploited to guide the identification of diverse immune subtypes, providing critical biological insights into the mechanisms driving tumor heterogeneity and responsible for cancer-related patient prognoses.

Novel Therapeutic Targets and Immune Dysfunction in Malignant Pleural Mesothelioma

Advances in the treatment of malignant pleural mesothelioma (MPM) have been disappointing, despite the apparent need for new therapeutic options for this rare and devastating cancer. Drug resistance is common and surgical intervention has brought benefits only to a subset of patients. MPM is a heterogenous disease with a surprisingly low mutation rate and recent sequencing efforts have confirmed alterations in a limited number of tumor suppressors that do not provide apparent insights into the molecular mechanisms that drive this malignancy. There is increasing evidence that epigenetic regulation leads to immune evasion and transformation in MPM. Further, the low efficacy of immune checkpoint inhibitors is consistent with a suppression of genes involved in the anti-tumor immune response. We review three promising emerging therapeutic targets (STAT3, KDM4A, heparanase) and highlight their potential effects on the immune response.

Establishment and characterization of NCC‑DMM1‑C1, a novel patient‑derived cell line of desmoplastic malignant pleural mesothelioma

Desmoplastic malignant pleural mesothelioma (DMM) is a rare histological variant of malignant pleural mesothelioma, which is a highly aggressive neoplasm of the mesothelium. DMM is associated with distant metastases and short survival. Effective treatments for DMM are not established and the development of histotype-tailored treatments is difficult due to the rarity of the disease. Although patient-derived cancer models are crucial tools for the development of novel therapeutics, they are difficult to obtain for DMM; no DMM cell lines or xenografts are available from public biobanks and only two cell lines have been reported. Thus, the present study aimed to establish a novel cell line of DMM as a resource for drug screening. A cell line of DMM was established, designated as NCC-DMM1-C1, using surgically resected tumor tissues from a 73-year-old male patient with DMM. Characteristics of NCC-DMM1-C1 cells were examined, such as growth, spheroid formation and invasion capability. Drug targets and anti-cancer drugs with anti-proliferative efficacy were examined using a comprehensive kinase activity assay and drug screening of 213 anti-cancer agents, respectively. NCC-DMM1-C1 exhibited fast growth, spheroid formation and invasion capability, suggesting that the NCC-DMM1-C1 cells retained the aggressive features of DMM. NCC-DMM1-C1 cells and the tumor tissue shared common activity profiles of kinases, which included FES, Wee1, platelet-derived growth factor receptor-β and Src. The drug screening revealed that bortezomib, fostamatinib, gemcitabine, homoharringtonine and vinorelbine had anti-proliferative effects, which have not been previously reported for DMM. It was concluded that NCC-DMM1-C1 cells may be a useful tool for the study of DMM.

Essential role of the histone lysine demethylase KDM4A in the biology of malignant pleural mesothelioma (MPM)

BACKGROUND

Malignant pleural mesothelioma (MPM) is a highly aggressive cancer with a dismal prognosis. There is increasing interest in targeting chromatin regulatory pathways in difficult-to-treat cancers. In preliminary studies, we found that KDM4A (lysine-specific histone demethylase 4) was overexpressed in MPM.

METHODS

KDM4A protein expression was determined by immunohistochemistry or immunoblotting. Functional inhibition of KDM4A by targeted knockdown and small molecule drugs was correlated to cell growth using cell lines and a xenograft mouse model. Gene expression profiling was performed to identify KDM4A-dependent signature pathways.

RESULTS

Levels of KDM4A were found to be significantly elevated in MPM patients compared to normal mesothelial tissue. Inhibiting the enzyme activity efficiently reduced cell growth in vitro and reduced tumour growth in vivo. KDM4A inhibitor-induced apoptosis was further enhanced by the BH3 mimetic navitoclax. KDM4A expression was associated with pathways involved in cell growth and DNA repair. Interestingly, inhibitors of the DNA damage and replication checkpoint regulators CHK1 (prexasertib) and WEE1 (adavosertib) within the DNA double-strand break repair pathway, cooperated in the inhibition of cell growth.

CONCLUSIONS

The results establish a novel and essential role for KDM4A in growth in preclinical models of MPM and identify potential therapeutic approaches to target KDM4A-dependent vulnerabilities.

Small Molecule Inhibitors of TEAD Auto-palmitoylation Selectively Inhibit Proliferation and Tumor Growth of NF2-deficient Mesothelioma

Mutations in the neurofibromatosis type 2 (NF2) gene that limit or abrogate expression of functional Merlin are common in malignant mesothelioma. Merlin activates the Hippo pathway to suppress nuclear translocation of YAP and TAZ, the major effectors of the pathway that associate with the TEAD transcription factors in the nucleus and promote expression of genes involved in cell proliferation and survival. In this article, we describe the discovery of compounds that selectively inhibit YAP/TAZ-TEAD promoted gene transcription, block TEAD auto-palmitoylation, and disrupt interaction between YAP/TAZ and TEAD. Optimization led to potent analogs with excellent oral bioavailability and pharmacokinetics that selectively inhibit NF2-deficient mesothelioma cell proliferation in vitro and growth of subcutaneous tumor xenografts in vivo These highly potent and selective TEAD inhibitors provide a way to target the Hippo-YAP pathway, which thus far has been undruggable and is dysregulated frequently in malignant mesothelioma and in other YAP-driven cancers and diseases.

Impact of metallothionein-knockdown on cisplatin resistance in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare, but aggressive tumor with dismal prognosis. Platinum-based chemotherapy is regularly used as part of multimodality therapy. The expression of metallothioneins (MT) has been identified as a reason for cisplatin resistance, which often leads to early therapy failure or relapse. Thus, knockdown of MT expression may improve response to cisplatin treatment. The MT gene- and protein expression of the MPM-cell lines MSTO-211H, NCI-H2052 and NCI-H2452 and the human fibroblast cell line MRC-5, as well as their sensitivity to cisplatin treatment have been evaluated. Knockdown of MT1A, 1B and 2A expression was induced by RNA interference. MT expression was measured using quantitative real-time PCR. An in vitro Assay based on enzyme activity was used to detect cell viability, necrosis and apoptosis before and after incubation with cisplatin. MT2A gene expression could be detected in all MPM cell lines, showing the highest expression in NCI-H2452 and NCI-H2052, whereas gene expression levels of MT1A and MT1B were low or absent. The immunohistochemically protein expression of MT-I/II reflect MT2A gene expression levels. Especially for MSTO-211H cell presenting low initial MT2A levels, a strong induction of MT2A expression could be observed during cisplatin treatment, indicating a cell line-specific and platin-dependent adaption mechanism. Additionally, a MT2A-dependent cellular evasion of apoptosis during cisplatin could be observed, leading to three different MT based phenotypes. MSTO-211H cells showed lower apoptosis rates at an increased expression level of MT2A after cisplatin treatment (from sixfold to fourfold). NCI-H2052 cells showed no changes in MT2A expression, while apoptosis rate is the highest (8-12-fold). NCI-H2452 cells showed neither changes in alteration rate of MT2A expression nor changes in apoptosis rates, indicating an MT2A-independent resistance mechanism. Knockdown of MT2A expression levels resulted in significantly induced apoptotic rates during cisplatin treatment with strongest induction of apoptosis in each of the MPM cell lines, but in different markedness. A therapeutic meaningful effect of MT2A knockdown and subsequent cisplatin treatment could be observed in MSTO-211H cells. The present study showed MT2A to be part of the underlying mechanism of cisplatin resistance in MPM. Especially in MSTO-211H cells we could demonstrate major effects by knockdown of MT2A expression, verifying our hypothesis of an MT driven resistance mechanism. We could prove the inhibition of MT2A as a powerful tool to boost response rates to cisplatin-based therapy in vitro. These data carry the potential to enhance the clinical outcome and management of MPM in the future.

Deep Sequencing Analysis Identified a Specific Subset of Mutations Distinctive of Biphasic Malignant Pleural Mesothelioma

Malignant Pleural Mesothelioma (MPM) is a heterogeneous disease. Morphologically, three different phenotypes are distinguishable: epithelioid (e-), sarcomatoid (s-) and biphasic (biph-) MPM, the latest, being a mixture of e- and s-MPM cells. Being an intermediate entity, management of biph-MPM, remains debatable and controversial, with different guidelines recommending distinct approaches. Identification of biph-MPM associated genetic alterations, through deep sequencing analysis, may provide useful tools to understand these lesions. A retrospective cohort of 69 surgically resected MPMs, 39 biph-MPMs (56.5%) and 30 e-MPMs (43.5%) was selected. A separate set of 16 biph-MPM was used as validation set. Deep sequencing analysis on an MPM-specific custom panel (MPM_geneset) comprising 1041 amplicons spanning 34 genes was performed. A total of 588 variants and 5309 mutational events were detected. In total, 91.3% of MPMs showed at least one mutation and 76.8% showed co-occurrence of more than one alteration. Mutations in MXRA5 (p = 0.05) and NOD2 (p = 0.018) were significantly associated with biph-MPM both in the training and validation cohort and correlated with the extent of the sarcomatoid component. Mutations in NOD2 and XRCC6 correlated with patients’ survival. We demonstrated that biph-MPM are associated with a specific mutation set, and that genetic analysis at diagnosis may improve patients’ risk stratification.

A Novel T Cell-Engaging Bispecific Antibody for Treating Mesothelin-Positive Solid Tumors

As mesothelin is overexpressed in various types of cancer, it is an attractive target for therapeutic antibodies. T-cell bispecific antibodies bind to target cells and engage T cells via binding to CD3, resulting in target cell killing by T-cell activation. However, the affinity of the CD3-binding arm may influence CD3-mediated plasma clearance or antibody trapping in T-cell-containing tissues. This may then affect the biodistribution of bispecific antibodies. In this study, we used scFab and knob-into-hole technologies to construct novel IgG-based 1 + 1 MG1122-A and 2 + 1 MG1122-B bispecific antibodies against mesothelin and CD3ε. MG1122-B was designed to be bivalent to mesothelin and monovalent to CD3ε, using a 2 + 1 head-to-tail format. Activities of the two antibodies were evaluated in mesothelin-positive tumor cells in vitro and xenograft models in vivo. Although both antibodies exhibited target cell killing efficacy and produced regression of xenograft tumors with CD8+ T-cell infiltration, the antitumor efficacy of MG1122-B was significantly higher. MG1122-B may improve tumor targeting because of its bivalency for tumor antigen. It may also reduce systemic toxicity by limiting the activation of circulating T cells. Thus, MG1122-B may be useful for treating mesothelin-positive solid tumors.

Bortezomib sensitivity is tissue dependent and high expression of the 20S proteasome precludes good response in malignant pleural mesothelioma

Background

Bortezomib is an approved proteasome inhibitor for the treatment of certain lymphoma subtypes. Two clinical trials investigated bortezomib in patients with malignant pleural mesothelioma (MPM) and failed to improve outcome. We present a potential explanation for this event.

Methods

171 patients with MPM were analyzed for their mRNA expression of proteasomal subunits PSMA1, PSMA5, PSMB1, PSMB2, PSMB4 and PSMB5 via qPCR (n=84) or sequencing (n=87 TCGA/cBioPortal data set “Mesothelioma”). Outcome and subunit expression were correlated. Four mesothelial and one fibroblast cell line were treated with bortezomib and cisplatin. Cellular response was measured after 0, 6, 12, 24, 48 and 72 hrs. Enzyme activity of proteasomal subunits was assessed via functional enzyme activity assays.

Results

Patients with MPM presented with elevated expression of proteasomal subunits compared to benign controls (p<0.001). PSMB4 correlated with outcome (Cox propotiortional-hazards model (COXPH): p<0.0175, TCGA/cBioPortal data). In cell lines, apoptosis was the main event with a peak after 48 hr incubation for bortezomib or cisplatin. Only two cell lines with comparably low proteasome activity (PSMB2 and PSMB5) responded to 50 nM and 100 nM bortezomib better than to cisplatin (MRC-5, NCI-H2052). MSTO-211H responded to cisplatin only, whereas the other two cell lines were considered therapy resistant (Met-5A, NCI-H2452).

Interpretation

Two clinical trials testing bortezomib in MPM failed, although MPM presents with high proteasome expression, which predicts bortezomib sensitivity in several tumors. Bortezomib induced apoptosis in MPM cell lines with low proteasome activity only. Bortezomib is not suitable for the treatment of MPM, and biomarker-based stratification could have improved both clinical trials.

Trial registration

NCT00513877 and NCT00458913

Gene expression profiling of homologous recombination repair pathway indicates susceptibility for olaparib treatment in malignant pleural mesothelioma in vitro

BACKGROUND

Malignant pleural mesothelioma (MPM) is a tumour arising from pleural cavities with poor prognosis. Multimodality treatment with pemetrexed combined with cisplatin shows unsatisfying response-rates of 40%. The reasons for the rather poor efficacy of chemotherapeutic treatment are largely unknown. However, it is conceivable that DNA repair mechanisms lead to an impaired therapy response. We hypothesize a major role of homologous recombination (HR) for genome stability and survival of this tumour. Therefore, we analysed genes compiled under the term "BRCAness". An inhibition of this pathway with olaparib might abrogate this effect and induce apoptosis.

METHODS

We investigated the response of three MPM cell lines and lung fibroblasts serving as a control to treatment with pemetrexed, cisplatin and olaparib. Furthermore, we aimed to find possible correlations between response and gene expression patterns associated with BRCAness phenotype. Therefore, 91 clinical MPM samples were digitally screened for gene expression patterns of HR members.

RESULTS

A BRCAness-dependent increase of apoptosis and senescence during olaparib-based treatment of BRCA-associated-protein 1 (BAP1)-mutated cell lines was observed. The gene expression pattern identified could be found in approx. 10% of patient samples. Against this background, patients could be grouped according to their defects in the HR system. Gene expression levels of Aurora Kinase A (AURKA), RAD50 as well as DNA damage-binding protein 2 (DDB2) could be identified as prognostic markers in MPM.

CONCLUSIONS

Defects in HR compiled under the term BRCAness are a common event in MPM. The present data can lead to a better understanding of the underlaying cellular mechanisms and leave the door wide open for new therapeutic approaches for this severe disease with infaust prognosis. Response to Poly (ADP-ribose)-Polymerase (PARP)-Inhibition could be demonstrated in the BAP1-mutated NCI-H2452 cells, especially when combined with cisplatin. Thus, this combination therapy might be effective for up to 2/3 of patients, promising to enhance patients' clinical management and outcome.

P2X7 targeting inhibits growth of human mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive tumor refractory to anti-blastic therapy. MPM cells show several genetic and biochemical defects, e.g. overexpression of oncogenes, downregulation of onco-suppressor genes, dysregulation of microRNA, or alteration of intracellular Ca²⁺ homeostasis and of apoptosis. No information is as yet available on purinergic signalling in this tumor. Signalling via the P2×7 (P2RX7 or P2×7R) purinergic receptor is attracting increasing attention as a pathway involved in cancer cell death or proliferation. In this report we show that the P2×7R is expressed by three MPM cell lines established from MPM patients but not by mesothelial cells from healthy subjects (healthy mesothelial cells, HMCs). MPM cell proliferation was inhibited by in vitro incubation in the presence of selective P2×7R antagonists, as well as by stimulation with the P2×7R agonist BzATP. Systemic administration of the selective P2×7R blocker AZ10606120 inhibited in vivo growth of MPM tumors whether implanted subcutaneously (s.c.) or intraperitoneally (i.p.). Our findings suggest that the P2×7R might be a novel target for the therapy of mesothelioma.

Chemosensitivity and resistance testing in malignant effusions with focus on primary malignant mesothelioma and metastatic adenocarcinoma

Cell based chemosensitivity and resistance testing is an attractive approach that offers functional measurement of drug response ex vivo with the ultimate goal to guide the choice of chemotherapy for various cancers. Thus, it has a great potential to select patients for the optimal treatment option, thereby offering a tool for personalized cancer therapy. Despite several decades of intensive scientific efforts ex-vivo tests are still not incorporated in the standard of care. Limited access to fresh tumor tissue, unsatisfactory models and single readout as endpoint constitute major hindrance. Thus, establishing and validating clinically useful and reliable model systems still remains a major challenge. Here we present malignant effusions as valuable sources for ex-vivo chemosensitivity and resistance testing. Accumulation of a malignant effusion in the pleura, peritoneum or pericardium is often the first diagnostic material for both primary malignant mesothelioma and a broad spectrum of metastatic adenocarcinoma originating from lung-, breast-, ovary- and gastro-intestinal organs as well as lymphoma. In contrast to biopsies, in these effusions malignant cells are easily accessible and often abundant. Effusion derived cells can occur dissociated or forming three-dimensional papillary structures that authentically recapitulate the biology of the corresponding tumor tissue and offer models for ex vivo testing. In addition, effusions have the advantage of being available prior to or concurrent with the pathological review, thus constituting an excellent source of viable cells for simultaneous molecular profiling, biomarker analysis and for establishing primary cells for studying tumor biology and resistance mechanisms. For a reliable test, however, a careful validation is needed, taking into account the inherited heterogeneity of malignant tumors, but also the complex interplay between malignant and benign cells, which are always present in this setting.

Mithramycin Depletes Specificity Protein 1 and Activates p53 to Mediate Senescence and Apoptosis of Malignant Pleural Mesothelioma Cells

PURPOSE

Specificity protein 1 (SP1) is an oncogenic transcription factor overexpressed in various human malignancies. This study sought to examine SP1 expression in malignant pleural mesotheliomas (MPM) and ascertain the potential efficacy of targeting SP1 in these neoplasms.

EXPERIMENTAL DESIGN

qRT-PCR, immunoblotting, and immunohistochemical techniques were used to evaluate SP1 expression in cultured MPM cells and MPM specimens and normal mesothelial cells/pleura. MTS, chemotaxis, soft agar, β-galactosidase, and Apo-BrdUrd techniques were used to assess proliferation, migration, clonogenicity, senescence, and apoptosis in MPM cells following SP1 knockdown, p53 overexpression, or mithramycin treatment. Murine subcutaneous and intraperitoneal xenograft models were used to examine effects of mithramycin on MPM growth in vivo. Microarray, qRT-PCR, immunoblotting, and chromatin immunoprecipitation techniques were used to examine gene expression profiles mediated by mithramycin and combined SP1 knockdown/p53 overexpression and correlate these changes with SP1 and p53 levels within target gene promoters.

RESULTS

MPM cells and tumors exhibited higher SP1 mRNA and protein levels relative to control cells/tissues. SP1 knockdown significantly inhibited proliferation, migration, and clonogenicity of MPM cells. Mithramycin depleted SP1 and activated p53, dramatically inhibiting proliferation and clonogenicity of MPM cells. Intraperitoneal mithramycin significantly inhibited growth of subcutaneous MPM xenografts and completely eradicated mesothelioma carcinomatosis in 75% of mice. Mithramycin modulated genes mediating oncogene signaling, cell-cycle regulation, senescence, and apoptosis in vitro and in vivo. The growth-inhibitory effects of mithramycin in MPM cells were recapitulated by combined SP1 knockdown/p53 overexpression.

CONCLUSIONS

These findings provide preclinical rationale for phase II evaluation of mithramycin in patients with mesothelioma.

Comprehensive genomic analysis of malignant pleural mesothelioma identifies recurrent mutations, gene fusions and splicing alterations

We analyzed transcriptomes (n = 211), whole exomes (n = 99) and targeted exomes (n = 103) from 216 malignant pleural mesothelioma (MPM) tumors. Using RNA-seq data, we identified four distinct molecular subtypes: sarcomatoid, epithelioid, biphasic-epithelioid (biphasic-E) and biphasic-sarcomatoid (biphasic-S). Through exome analysis, we found BAP1, NF2, TP53, SETD2, DDX3X, ULK2, RYR2, CFAP45, SETDB1 and DDX51 to be significantly mutated (q-score ≥ 0.8) in MPMs. We identified recurrent mutations in several genes, including SF3B1 (∼2%; 4/216) and TRAF7 (∼2%; 5/216). SF3B1-mutant samples showed a splicing profile distinct from that of wild-type tumors. TRAF7 alterations occurred primarily in the WD40 domain and were, except in one case, mutually exclusive with NF2 alterations. We found recurrent gene fusions and splice alterations to be frequent mechanisms for inactivation of NF2, BAP1 and SETD2. Through integrated analyses, we identified alterations in Hippo, mTOR, histone methylation, RNA helicase and p53 signaling pathways in MPMs.

Zoledronic acid overcomes chemoresistance and immunosuppression of malignant mesothelioma

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

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

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

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

A novel link between FMR gene and the JNK pathway provides clues to possible role in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive form of thoracic cancer with poor prognosis. While some studies have identified the molecular alterations associated with MPM, little is known about their role in MPM. For example, fragile X mental retardation (FMR) gene is up-regulated in MPM but its role in MPM is unknown. Here, utilizing Drosophila genetics, I investigate the possible role FMR may be playing in MPM. I provide evidence which suggests that FMR may contribute to tumorigenesis by up-regulating a matrix metalloprotease (MMP) and by degrading the basement membrane (BM), both important for tumor metastasis. I also demonstrate a novel link between FMR and the JNK pathway and suggest that the effects of FMR in MPM could in part be mediated by up-regulation of the JNK pathway.