Malignant pleural mesothelioma: current treatments and emerging drugs

EGFR-targeted pemetrexed therapy of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare malignancy with poor prognosis, for which chemotherapy with pemetrexed (PEM) is among the few clinical treatments. PEM suffers, however, fast clearance, moderate drug exposure, and dose-limiting toxicities. Here, we report on epidermal growth factor receptor (EGFR)-targeted disulfide-crosslinked biodegradable chimaeric polymersomes (EGFR-CPs) to firmly load PEM and boost chemotherapy of MPM. EGFR-CPs encapsulating 8.7-16.4 wt.% PEM (EGFR-CPs-PEM) showed diameters of 62-65 nm and reduction-responsive drug release property. EGFR-CPs-PEM was more efficiently taken up by EGFR-overexpressed MSTO-211H cells, inducing about 4.7-fold enhanced anticancer activity compared with non-targeted CPs-PEM control. Intriguingly, the in vivo experiments in MSTO-211H xenograft mouse model revealed that EGFR-CPs-PEM brought about superior tumor deposition and penetration to CPs-PEM, and significantly more potent tumor repression than CPs-PEM and free PEM. This polymersome-enabled EGFR-targeted delivery of PEM offers an appealing therapeutic strategy for MPM.

Pyruvate Treatment Restores the Effectiveness of Chemotherapeutic Agents in Human Colon Adenocarcinoma and Pleural Mesothelioma Cells

Emerging evidence supports the idea that a dysfunction in cell metabolism could sustain a resistant phenotype in cancer cells. As the success of chemotherapeutic agents is often questioned by the occurrence of multidrug resistance (MDR), a multiple cross-resistance towards different anti-cancer drugs represent a major obstacle to cancer treatment. The present study has clarified the involvement of the carbon metabolites in a more aggressive tumor colon adenocarcinoma phenotype and in a chemoresistant mesothelioma, and the role of pyruvate treatment in the reversion of the potentially related resistance. For the first time, we have shown that human colon adenocarcinoma cells (HT29) and its chemoresistant counterpart (HT29-dx) displayed different carbon metabolism: HT29-dx cells had a higher glucose consumption compared to HT29 cells, whereas human malignant mesothelioma (HMM) cells showed a lower glucose consumption compared to HT29 cells, accompanied by a lower pyruvate production and, consequently, a higher production of lactate. When treated with pyruvate, both HT29-dx and HMM cells exhibited a re-established accumulation of doxorubicin and a lower survival ability, a decreased activity of multidrug resistance protein 1 (MRP1) and a restored mitochondrial respiratory chain function, improving the effectiveness of the chemotherapeutic agents in these resistant cancer cells.

WWW mesothelioma information: Surfing on unreliable waters. A cross-sectional study into the content and quality of online informational resources for mesothelioma patients

OBJECTIVE

Malignant Mesothelioma (MM) is a rare asbestos related disease mostly diagnosed in low-skilled patients. The decision-making process for MM treatment is complicated, making an adequate provision of information necessary. The objective of this study is to assess the content and quality of online informational resources available for Dutch MM patients.

METHODS

The first 100 hits of a Google search were studied using the JAMA benchmarks, the Modified Information Score (MIS) and the International Patient Decision Aid Standard Scoring (IPDAS).

RESULTS

A total of 37 sources were included. Six of the 37 resources were published by hospitals. On average, the informational resources scored 37 points on the MIS (scale 0-100). The resources from a (bio)medical sources scored the best on this scale. However, on the domain of use of language, these resources scored the worst.

CONCLUSIONS

The current level of medical content and quality of online informational resources for patient with MM is below average and cannot be used as decision-aids for patients.

PRACTICE IMPLICATIONS

The criteria used in this article could be used for future improvements of online informational resources for patients, both online, offline and through health education in the care path.

Immunotherapy advances for mesothelioma treatment

INTRODUCTION

Mesothelioma is a rare type of cancer that is strongly tied to asbestos exposure. Despite application of different modalities such as chemotherapy, radiotherapy and surgery, patient prognosis remains very poor and therapies are ineffective. Much research currently focuses on the application of novel approaches such as immunotherapy towards this disease. Areas covered: The types, stages and aetiology of mesothelioma are detailed, followed by a discussion of the current treatment options such as radiotherapy, surgery, and chemotherapy. A description of innate and adaptive immunity and the principles and justification of immunotherapy is also included. Clinical trials for different immunotherapeutic modalities are described, and lastly the article closes with an expert commentary and five-year view, the former of which is summarised below. Expert commentary: Current efforts for novel mesothelioma therapies have been limited by attempting to apply treatments from other cancers, an approach which is not based on a solid understanding of mesothelioma biology. In our view, the influence of the hostile, hypoxic microenvironment and the gene expression and metabolic changes that resultantly occur should be characterised to improve therapies. Lastly, clinical trials should focus on overall survival rather than surrogate endpoints to avoid bias and inaccurate reflections of treatment effects.

Expression and activity of eIF6 trigger malignant pleural mesothelioma growth in vivo

eIF6 is an antiassociation factor that regulates the availability of active 80S. Its activation is driven by the RACK1/PKCβ axis, in a mTORc1 independent manner. We previously described that eIF6 haploinsufficiency causes a striking survival in the Eμ-Myc mouse lymphoma model, with lifespans extended up to 18 months. Here we screen for eIF6 expression in human cancers. We show that Malignant Pleural Mesothelioma tumors (MPM) and a MPM cell line (REN cells) contain high levels of hyperphosphorylated eIF6. Enzastaurin is a PKC beta inhibitor used in clinical trials. We prove that Enzastaurin treatment decreases eIF6 phosphorylation rate, but not eIF6 protein stability. The growth of REN, in vivo, and metastasis are reduced by either Enzastaurin treatment or eIF6 shRNA. Molecular analysis reveals that eIF6 manipulation affects the metabolic status of malignant mesothelioma cells. Less glycolysis and less ATP content are evident in REN cells depleted for eIF6 or treated with Enzastaurin (Anti-Warburg effect). We propose that eIF6 is necessary for malignant mesothelioma growth, in vivo, and can be targeted by kinase inhibitors.

Inhibition of autophagy potentiates pemetrexed and simvastatin-induced apoptotic cell death in malignant mesothelioma and non-small cell lung cancer cells

Pemetrexed, a multitarget antifolate used to treat malignant mesothelioma and non-small cell lung cancer (NSCLC), has been shown to stimulate autophagy. In this study, we determined whether autophagy could be induced by pemetrexed and simvastatin cotreatment in malignant mesothelioma and NSCLC cells. Furthermore, we determined whether inhibition of autophagy drives apoptosis in malignant mesothelioma and NSCLC cells. Malignant mesothelioma MSTO-211H and A549 NSCLC cells were treated with pemetrexed and simvastatin alone and in combination to evaluate their effect on autophagy and apoptosis. Cotreatment with pemetrexed and simvastatin induced greater caspase-dependent apoptosis and autophagy than either drug alone in malignant mesothelioma and NSCLC cells. 3-Methyladenine (3-MA), ATG5 siRNA, bafilomycin A, and E64D/pepstatin A enhanced the apoptotic potential of pemetrexed and simvastatin, whereas rapamycin and LY294002 attenuated their induction of caspase-dependent apoptosis. Our data indicate that pemetrexed and simvastatin cotreatment augmented apoptosis and autophagy in malignant mesothelioma and NSCLC cells. Inhibition of pemetrexed and simvastatin-induced autophagy was shown to enhance apoptosis, suggesting that this could be a novel therapeutic strategy against malignant mesothelioma and NSCLC.

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.

Pemetrexed induces apoptosis in malignant mesothelioma and lung cancer cells through activation of reactive oxygen species and inhibition of sirtuin 1

Pemetrexed is a multitargeted antifolate used for the treatment of malignant mesothelioma and non-small cell lung cancer (NSCLC). However, the mechanism by which pemetrexed induces apoptosis remains unclear. In the present study, we investigated the involvement of reactive oxygen species (ROS) and sirtuin 1 (SIRT1) in pemetrexed-induced apoptosis in MSTO-211 malignant mesothelioma cells and A549 NSCLC cells. Pemetrexed enhanced caspase-dependent apoptosis, induced intracellular ROS generation, and downregulated SIRT1 in the MSTO-211 and A549 cells. Pemetrexed-induced apoptosis, which was prevented by pretreatment with N-acetyl-cysteine (NAC), was mediated by effects on the mitochondria, including mitochondrial membrane potential transition (MPT) and cytosolic release of cytochrome c, and also involved regulation of SIRT1 expression. Interference with SIRT1 expression using siRNA enhanced pemetrexed-induced apoptosis through mitochondrial dysfunction and ROS generation, whereas resveratrol, an activator of SIRT1, protected against pemetrexed-induced apoptosis. These results show that pemetrexed induces apoptosis in MSTO-211 mesothelioma cells and A549 NSCLC cells through mitochondrial dysfunction mediated by ROS accumulation and SIRT1 downregulation.

Evaluation of imaging techniques for the assessment of tumour progression in an orthotopic rat model of malignant pleural mesothelioma†

OBJECTIVES

An orthotopic rat tumour recurrence model for malignant pleural mesothelioma (MPM) provides clinical similarity to patients and is useful for drug testing combined with surgical intervention. Importantly, a reliable imaging method is required allowing for noninvasive and repetitive evaluation of the tumour load. We compared the tumour load assessed by bioluminescence and magnetic resonance imaging (MRI) to the macroscopic tumour volume as a reference standard.

METHODS

A total of 500,000 syngeneic rat MPM cells transfected with luciferase were implanted underneath the parietal pleura of immunocompetent rats (n=13). From the second day after implantation, bioluminescence measurements of the tumour load expressed as the maximum bioluminescent intensity (photon/second) were performed daily after intraperitoneal injection of the luciferase substrate, d-luciferin, to observe the first occurrence of tumour. Six days after the first detection of tumour, bioluminescence, MRI and macroscopic tumour volume measurement were conducted. For MRI, a 4.7-Tesla small animal imager equipped with a 1H whole-body rat coil was employed using T2-weighted fast spin-echo sequences. Tumour burden (mm3) was quantified from magnetic resonance transverse images by two independent readers by manual segmentation. Finally, the tumour burden assessed by bioluminescence and MRI was correlated (Pearson's correlation) with the macroscopic measurement of tumour (ellipsoid) volume.

RESULTS

In all rats, a single tumour nodule was found at the inoculation site with a median macroscopic volume of 46 mm3 (18-377 mm3). For tumour burden quantification of MRIs, we observed good interobserver correlation (R2=0.81, P<0.0001) as well as significant association with the macroscopic tumour volume (R2=0.59, P=0.002). However, the signal intensity of bioluminescence did not correspond to the macroscopic tumour volume (R2=0.01, P=0.76).

CONCLUSIONS

MRI is a reliable and reproducible noninvasive in vivo imaging method for MPM tumour burden assessment for the present MPM model.

Enhanced apoptosis by pemetrexed and simvastatin in malignant mesothelioma and lung cancer cells by reactive oxygen species-dependent mitochondrial dysfunction and Bim induction

Pemetrexed is a multitarget antifolate currently used for the treatment of malignant mesothelioma and non-small cell lung cancer (NSCLC). Statins, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors used primarily for hyperlidpidemia, have been studied for their antiproliferative and pro-apoptotic effects. However, the effects of simvastatin on pemetrexed-induced apoptosis have not been investigated. In this study, we investigated whether combination treatment with pemetrexed and simvastatin potentiates the apoptotic activity above that is seen with either drug alone in malignant mesothelioma and NSCLC cells. We found that the combination of pemetrexed and simvastatin induced more extensive caspase-dependent apoptosis than either drug alone in malignant mesothelioma cells (MSTO-211) or NSCLC cells (A549). In addition, reactive oxygen species (ROS) generation in cells treated with both pemetrexed and simvastatin was markedly increased compared to cells treated with either pemetrexed or simvastatin alone. Combination treatment also increased the loss of mitochondrial membrane potential, increased cytosolic release of cytochrome c, and altered expression of inhibitor of apoptosis proteins (IAP) and B-cell lymphoma-2 (Bcl-2) families of apoptosis related proteins. On the other hand, pretreatment with N-acetylcysteine (NAC) prevented apoptosis and mitochondrial dysfunction by pemetrexed and simvastatin. In addition, Bim siRNA conferred protection against apoptosis induced by pemetrexed and simvastatin. These results suggest that combination of pemetrexed and simvastatin potentiates their apoptotic activity beyond that of either drug alone in malignant mesothelioma and lung cancer cells. This activity is mediated through ROS-dependent mitochondrial dysfunction and Bim induction.

Malignant pleural mesothelioma: current and future perspectives

Mesothelioma still remains an occupational related cancer with severe outcome. It is usually diagnosed at advanced stage since it does not demonstrate early symptoms. Several efforts have been made towards removing all materials inducing mesothelioma in the work setting and new work protection measures have been applied. Although we have new targeted treatments and radical surgery as arrows in the quiver, the type of mesothelioma and early diagnosis still remain the best treatment approach. Novel treatment modalities have been explored and several others are already on the way. In the current review we will present current data for mesothelioma and future perspectives.

Synergistic inhibition of mesothelioma cell growth by the combination of clofarabine and resveratrol involves Nrf2 downregulation

We previously reported that MSTO-211H cells have a higher capacity to regulate Nrf2 activation in response to changes in the cellular redox environment. To further characterize its biological significance, the response of Nrf2, a transcription factor that regulates ARE-containing genes, on the synergistic cytotoxic effect of clofarabine and resveratrol was investigated in mesothelioma cells. The combination treatment showed a marked growth-inhibitory effect, which was accompanied by suppression of Nrf2 activation and decreased expression of heme oxygenase-1 (HO-1). While transient overexpression of Nrf2 conferred protection against the cytotoxicity caused by their combination, knockdown of Nrf2 expression using siRNA enhanced their cytotoxic effect. Pretreatment with Ly294002, a PI3K inhibitor, augmented the decrease in HO-1 level by their combination, whereas no obvious changes were observed in Nrf2 levels. Altogether, these results suggest that the synergistic cytotoxic effect of clofarabine and resveratrol was mediated, at least in part, through suppression of Nrf2 signaling.

Preclinical demonstration of synergistic Active Nutrients/Drug (AND) combination as a potential treatment for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a poor prognosis disease lacking adequate therapy. We have previously shown that ascorbic acid administration is toxic to MPM cells. Here we evaluated a new combined therapy consisting of ascorbate/epigallocatechin-3-gallate/gemcitabine mixture (called AND, for Active Nutrients/Drug). In vitro effects of AND therapy on various MPM cell lines revealed a synergistic cytotoxic mechanism. In vivo experiments on a xenograft mouse model for MPM, obtained by REN cells injection in immunocompromised mice, showed that AND strongly reduced the size of primary tumor as well as the number and size of metastases, and prevented abdominal hemorrhage. Kaplan Meier curves and the log-rank test indicated a marked increase in the survival of AND-treated animals. Histochemical analysis of dissected tumors showed that AND induced a shift from cell proliferation to apoptosis in cancer cells. Lysates of tumors from AND-treated mice, analyzed with an antibody array, revealed decreased TIMP-1 and -2 expressions and no effects on angiogenesis regulating factors. Multiplex analysis for signaling protein phosphorylation exhibited inactivation of cell proliferation pathways. The complex of data showed that the AND treatment is synergistic in vitro on MPM cells, and blocks in vivo tumor progression and metastasization in REN-based xenografts. Hence, the AND combination is proposed as a new treatment for MPM.

Phase II trial of neoadjuvant pemetrexed plus cisplatin followed by surgery and radiation in the treatment of pleural mesothelioma

Background

Malignant pleural mesothelioma is an aggressive tumor that has a poor prognosis and is resistant to unimodal approaches. Multimodal treatment has provided encouraging results.

Methods

Phase II, open-label study of the combination of chemotherapy (pemetrexed 500 mg/m²+cisplatin 75 mg/m² IV every 21 days × 3 cycles), followed by surgery (en-bloc extrapleural pneumonectomy, 3–8 weeks after chemotherapy) and hemithoracic radiation (total radiation beam 54 Gy, received 4–8 weeks post-surgery). The primary endpoint was event-free survival, defined as the time from enrollment to time of first observation of disease progression, death due to any cause, or early treatment discontinuation.

Results

Fifty-four treatment-naïve patients with T1-3 N0-2 malignant pleural mesothelioma were enrolled, 52 (96.3%) completed chemotherapy, 45 (83.3%) underwent surgery, 22 (40.7%) completed the whole treatment including 90-day post-radiation follow-up. The median event-free survival was 6.9 months (95%CI: 5.0-10.5), median overall survival was 15.5 months (95%CI 11.0-NA) while median time-to-tumor response was 4.8 months (95%CI: 2.5-8.0). Eighteen (33.3%) and 13 (24.1%) patients were still event-free after 1 and 2 years, respectively. The most common treatment-emergent adverse events were nausea (63.0%), anemia (51.9%) and hypertension (42.6%).

Following two cardiopulmonary radiation-related deaths the protocol was amended (21 [38.9%] patients were already enrolled in the study): the total radiation beam was reduced from 54 Gy to 50.4 Gy and a more accurate selection of patients was recommended.

Conclusions

The combination of pemetrexed plus cisplatin followed by surgery and hemithoracic radiation is feasible and has a manageable toxicity profile in carefully selected patients. It may be worthy of further investigation.

Trial registration

Clinicaltrial.com registrationID #NCT00087698.

Epigallocatechin-3-gallate induces mesothelioma cell death via H2 O2 -dependent T-type Ca2+ channel opening

Malignant mesothelioma (MMe) is a highly aggressive, lethal tumour requiring the development of more effective therapies. The green tea polyphenol epigallocathechin-3-gallate (EGCG) inhibits the growth of many types of cancer cells. We found that EGCG is selectively cytotoxic to MMe cells with respect to normal mesothelial cells. MMe cell viability was inhibited by predominant induction of apoptosis at lower doses and necrosis at higher doses. EGCG elicited H(2) O(2) release in cell cultures, and exogenous catalase (CAT) abrogated EGCG-induced cytotoxicity, apoptosis and necrosis. Confocal imaging of fluo 3-loaded, EGCG-exposed MMe cells showed significant [Ca(2+) ](i) rise, prevented by CAT, dithiothreitol or the T-type Ca(2+) channel blockers mibefradil and NiCl(2) . Cell loading with dihydrorhodamine 123 revealed EGCG-induced ROS production, prevented by CAT, mibefradil or the Ca(2+) chelator BAPTA-AM. Direct exposure of cells to H(2) O(2) produced similar effects on Ca(2+) and ROS, and these effects were prevented by the same inhibitors. Sensitivity of REN cells to EGCG was correlated with higher expression of Ca(v) 3.2 T-type Ca(2+) channels in these cells, compared to normal mesothelium. Also, Ca(v) 3.2 siRNA on MMe cells reduced in vitro EGCG cytotoxicity and abated apoptosis and necrosis. Intriguingly, Ca(v) 3.2 expression was observed in malignant pleural mesothelioma biopsies from patients, but not in normal pleura. In conclusion, data showed the expression of T-type Ca(2+) channels in MMe tissue and their role in EGCG selective cytotoxicity to MMe cells, suggesting the possible use of these channels as a novel MMe pharmacological target.

Natural diterpenes from coffee, cafestol and kahweol induce apoptosis through regulation of specificity protein 1 expression in human malignant pleural mesothelioma

Background

Malignant pleural mesothelioma (MPM) is a highly aggressive cancer with a very poor prognosis. Several clinical studies such as immunotherapy, gene therapy and molecular targeting agents have been tried for treatment of malignant mesothelioma, however, there is no application for effective clinical treatment. Coffee has various biological functions such as anti-oxidant, anti-inflammatory, anti-mutagenic and anti-carcinogenic activities. The therapeutic activities of the bioactive compounds in coffee was sugested to influence intracellular signaling of MPM. Regarding to the cancer-related functions, In this study, suppression of Sp1 protein level followed by induction of MSTO-211H cell apoptosis by cafestol and kahweol were investigated in oreder to determine Sp1's potential as a significant target for human MPM therapy as well.

Methods

Cells were treated separately with final concentration of cafestol and kahweol and the results were analyzed by MTS assay, DAPI staining, PI staining, luciferase assay, RT-PCR, and immunoblotting.

Results

Viability of MSTO-211H and H28 cells were decreased, and apoptotic cell death was increased in MSTO-211H as a result of cafestol and kahweol treatment. Cafestol and kahweol increased Sub-G₁ population and nuclear condensation in MSTO-211H cells. Roles of Sp1 in cell proliferation and apoptosis of the MSTO-211H cells by the Sp1 inhibitor of Mithramycin A were previously confirmed. Cafestol and kahweol significantly suppressed Sp1 protein levels. Kahweol slightly attenuated Sp1 mRNA, while Cafestol did not affect in MSTO-211H cells. Cafestol and kahweol modulated the promoter activity and protein expression level of the Sp1 regulatory genes including Cyclin D1, Mcl-1, and Survivin in mesothelioma cells. Apoptosis signaling cascade was activated by cleavages of Bid, Caspase-3, and PARP with cafestol and by upregulation of Bax, and downregulation of Bcl-_xl by kahweol.

Conclusions

Sp1 can be a novel molecular target of cafestol and kahweol in human MPM.

Preclinical studies identify novel targeted pharmacological strategies for treatment of human malignant pleural mesothelioma

The incidence of human malignant pleural mesothelioma (hMPM) is still increasing worldwide. hMPM prognosis is poor even if the median survival time has been slightly improved after the introduction of the up-to-date chemotherapy. Nevertheless, large phase II/III trials support the combination of platinum derivatives and pemetrexed or raltitrexed, as preferred first-line schedule. Better understanding of the molecular machinery of hMPM will lead to the design and synthesis of novel compounds targeted against pathways identified as crucial for hMPM cell proliferation and spreading. Among them, several receptors tyrosine kinase show altered activity in subsets of hMPM. This observation suggests that these kinases might represent novel therapeutic targets in this chemotherapy-resistant disease. Over these foundations, several promising studies are ongoing at preclinical level and novel molecules are currently under evaluation as well. Yet, established tumour cell lines, used for decades to investigate the efficacy of anticancer agents, although still the main source of drug efficacy studies, after long-term cultures tend to biologically diverge from the original tumour, limiting the predictive potential of in vivo efficacy. Cancer stem cells (CSCs), a subpopulation of malignant cells capable of self-renewal and multilineage differentiation, are believed to play an essential role in cancer initiation, growth, metastasization and relapse, being responsible of chemo- and radiotherapy refractoriness. According to the current carcinogenesis theory, CSCs represent the tumour-initiating cell (TIC) fraction, the only clonogenic subpopulation able to originate a tumour mass. Consequently, the recently described isolation of TICs from hMPM, the proposed main pharmacological target for novel antitumoural drugs, may contribute to better dissect the biology and multidrug resistance pathways controlling hMPM growth.

Revisiting cutaneous adverse reactions to pemetrexed

Pemetrexed (Alimta®) is a multitargeted antifolate drug approved as a single agent or in combination with cisplatin for the treatment of a small number of malignancies including advanced and metastatic non-squamous non-small cell lung cancer (NSCLC), and malignant pleural mesothelioma. This review reports the recent peer-reviewed publications and original findings regarding cutaneous adverse reactions (CARs) to pemetrexed. Pemetrexed-related CARs are frequently reported under the unspecific term 'skin rash'. However, more specific diseases were tentatively identified as alopecias, urticarial vasculitis, acute generalized exanthematous pustulosis, toxic epidermal necrolysis, radiation recall dermatitis and pityriasis lichenoides. Most of the skin reactions occur shortly after pemetrexed administration. As with methotrexate-related CARs, the cell cycle arrest in the S phase may be regarded as a direct and major cause of the cytotoxic pathobiology. An adverse immune reaction is unlikely. In conclusion, pemetrexed is responsible for CARs exhibiting a variety of clinical presentations. Their origin is likely attributed to direct cytotoxicity following the cell cycle arrest in the S phase and cell necrosis.

In vitro screening of synergistic ascorbate-drug combinations for the treatment of malignant mesothelioma

Malignant mesothelioma (MMe) is a lethal tumor arising from the mesothelium of serous cavities as a result of exposure to asbestos. Current clinical standards consist of combined treatments, but an effective therapy has not been established yet and there is an urgent need for new curative approaches. Ascorbate is a nutrient that is also known as a remedy in the treatment of cancer. In the present study, we have tested the cytotoxicity of ascorbate to MMe cells in combination with drugs used in MMe therapy, such as cisplatin, etoposide, gemcitabine, imatinib, paclitaxel, and raltitrexed, as well as with promising antitumor compounds like taurolidine, α-tocopherol succinate, and epigallocatechin-3-gallate (EGCG). Dose-response curves obtained for each compound by applying the neutral red uptake (NRU) assay to MMe cells growing in vitro, allowed to obtain IC50 values for each compound used singularly. Thereafter, NRU data obtained from each ascorbate/drug combination were analyzed through Tallarida's isobolograms at the IC50 level (Tallarida, 2000), revealing synergistic interactions for ascorbate/gemcitabine and ascorbate/EGCG. These results were further confirmed through comparisons between theoretical additivity IC50 and observed IC50 from fixed-ratio dose-response curves, and over a broad range of IC levels, by using Chou and Talalay's combination index (Chou and Talalay, 1984). Synergistic interactions were also shown by examining apoptosis and necrosis rates, using the caspase 3 and lactic dehydrogenase assays, respectively. Hence, data indicate that ascorbate/gemcitabine and ascorbate/EGCG affect synergistically the viability of MMe cells and suggest their possible use in the clinical treatment of this problematic cancer.

Combined chemotherapy with cytotoxic and targeted compounds for the management of human malignant pleural mesothelioma

Human malignant pleural mesothelioma (hMPM) is an aggressive asbestos-associated cancer, the incidence of which is increasing and which, despite progress in diagnosis and therapy, continues to have a poor prognosis. Asbestos fibers induce aberrant cell signaling, leading to proto-oncogene activation and chemoresistance. In this review, we discuss the evolution of pharmacological management of hMPM up to the most recent advances. Monotherapy with single cytotoxic drugs achieves modest objective response rates, seldom reaching 30%. However, combination regimens using novel drugs and standard molecules are showing gradually improving responses and clinical benefits. Phase II/III studies have identified pemetrexed, a multitarget folate pathway inhibitor in combination with platinum derivatives, and the cisplatin/gemcitabine association as front-line chemotherapy for hMPM. Detailed knowledge of molecular mechanisms of signal transduction and neoangiogenesis in hMPM should aid in the design and screening of other promising compounds such as more efficacious receptor tyrosine kinase inhibitors.

Curcumin suppresses growth of mesothelioma cells in vitro and in vivo, in part, by stimulating apoptosis

Malignant pleural mesothelioma (MPM) is an aggressive, asbestos-related malignancy of the thoracic pleura. Although, platinum-based agents are the first line of therapy, there is an urgent need for second-line therapies to treat the drug-resistant MPM. Cell cycle as well as apoptosis pathways are frequently altered in MPM and thus remain attractive targets for intervention strategies. Curcumin, the major component in the spice turmeric, alone or in combination with other chemotherapeutics has been under investigation for a number of cancers. In this study, we investigated the biological and molecular responses of MPM cells to curcumin treatments and the mechanisms involved. Flow-cytometric analyses coupled with western immunoblotting and gene-array analyses were conducted to determine mechanisms of curcumin-dependent growth suppression of human (H2373, H2452, H2461, and H226) and murine (AB12) MPM cells. Curcumin inhibited MPM cell growth in a dose- and time-dependent manner while pretreatment of MPM cells with curcumin enhanced cisplatin efficacy. Curcumin activated the stress-activated p38 kinase, caspases 9 and 3, caused elevated levels of proapoptotic proteins Bax, stimulated PARP cleavage, and apoptosis. In addition, curcumin treatments stimulated expression of novel transducers of cell growth suppression such as CARP-1, XAF1, and SULF1 proteins. Oral administration of curcumin inhibited growth of murine MPM cell-derived tumors in vivo in part by stimulating apoptosis. Thus, curcumin targets cell cycle and promotes apoptosis to suppress MPM growth in vitro and in vivo. Our studies provide a proof-of-principle rationale for further in-depth analysis of MPM growth suppression mechanisms and their future exploitation in effective management of resistant MPM.

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.