Greillier L, Marco S, Barlesi F.

Service d’Oncologie Multidisciplinaire et Innovations Thérapeutiques, Université de la Méditerranée-Assistance Publique Hôpitaux de Marseille, Marseille, France.

Abstract

Malignant pleural mesothelioma (MPM) is an aggressive tumor with poor prognosis, whose exposure to asbestos fibers is the main etiology. The incidence of MPM is anticipated to increase worldwide during the first half of this century. MPM is notoriously refractory to most treatments, and the only standard of care is cisplatin and antifolate first-line chemotherapy. The urgent need for additional therapeutic agents, in parallel with advances in the knowledge of the molecular events of oncogenesis, has resulted in the development of the so-called ‘targeted agents’ that specifically inhibit critical pathways in malignant cells and in their microenvironment. We carried out a comprehensive review of the literature from January 2000 to May 2010 on studies that assessed targeted agents for the systemic treatment of MPM. Although tyrosine kinase inhibitors directed against the epidermal growth factor and the platelet-derived growth factor receptors did not show significant clinical activity in phase II studies, some other targeted therapies seemed promising, notably histone deacetylase inhibitors and antiangiogenic agents. However, none of these has yet reached daily practice. That is the reason why efforts must continue in the area of clinical and translational research for MPM.

Ou WB, Hubert C, Corson JM, Bueno R, Flynn DL, Sugarbaker DJ, Fletcher JA.

Department of Pathology, Brigham and Women’s Hospital, Boston, MA, USA.

Abstract

The receptor tyrosine kinases (RTKs) epidermal growth factor receptor (EGFR) and MET are activated in subsets of mesothelioma, suggesting that these kinases might represent novel therapeutic targets in this notoriously chemotherapy-resistant cancer. However, clinical trials have shown little activity for EGFR inhibitors in mesothelioma. Despite the evidence for RTK activation in mesothelioma pathogenesis, it is unclear whether transforming activity is dependent on an individual kinase oncoprotein or the coordinated activity of multiple kinases. Using phospho-RTK and immunoblot assays, we herein demonstrate activation of multiple RTKs (EGFR, MET, AXL, and ERBB3) in individual mesothelioma cell lines but not in normal mesothelioma cells. Inhibition of mesothelioma multi-RTK signaling was accomplished using combinations of RTK direct inhibitors or by inhibition of the RTK chaperone, heat shock protein 90 (HSP90). Multi-RTK inhibition by the HSP90 inhibitor 17-allyloamino-17-demethoxygeldanamycin (17-AAG) had a substantially greater effect on mesothelioma proliferation and survival compared with inhibition of individual activated RTKs. HSP90 inhibition also suppressed phosphorylation of downstream signaling intermediates (AKT, mitogen-activated protein kinase, and S6); upregulated the p53, p21, and p27 cell cycle checkpoints; induced G(2) phase arrest; induced caspase 3/7 activity; and led to an increase in the sub-G(1) apoptotic population. These compelling proapoptotic and antiproliferative responses indicate that HSP90 inhibition warrants clinical evaluation as a novel therapeutic strategy in mesothelioma.

KaoSubramanian J, Corrales L, Soulieres D, Morgensztern D, Govindan R.

*Division of Oncology, Department of Medicine, Washington University School of Medicine; †Department of Medicine, Alvin J Siteman Cancer Center at Washington University School of Medicine, St Louis, Missouri; and ‡Department of Medicine, Centre Hospitalier de l’Université de Montréal, Montreal, Canada.

Abstract

Globally, lung cancer remains the most common cause of cancer-related death. In recent years, it has become clear that development of rational molecular targeted therapies is critical to improve the outcomes of patients with lung cancer. A better understanding of the tumor biology is crucial to achieve this goal. Several new findings in the field of tumor biology were presented at the 46th Annual Meeting of the American Society of Clinical Oncology. Novel genetic mutations were identified in pleural mesothelioma using array-based technologies. Several studies on the development and testing of new molecular diagnostic tests to detect epidermal growth factor receptor tyrosine kinase mutations and EML4-ALK (Echinoderm Microtubule-associated Protein like 4 Anaplastic Lymphoma Receptor Tyrosine Kinase) fusion gene were presented as well.

Foster JM, Gatalica Z, Lilleberg S, Haynatzki G, Loggie BW.

Division of Surgical Oncology, Creighton University Medical Center, Creighton University, Omaha, NE 68131, USA. jasonfoster@creighton.edu

Abstract

Malignant peritoneal mesotheliomas (MPM) are rare tumors representing 20% of all malignant mesothelioma cases. The median survival for these tumors is less than a year, and like other peritoneal surface malignancies, this is due primarily to intra-abdominal recurrence and progression. Currently there is a paucity of information about the biology of these tumors and molecular perturbations that are involved in tumor formation. Elucidation of mutations and biological pathways active in these tumors may identify valuable prognostic markers, as well as facilitate the development of novel therapies. In this study, we investigate the predictive value of epidermal growth factor receptor (EGFR) mutations in achieving optimal resectability. Twenty-nine patients with MPM were evaluated at a single tertiary care center and their tumors were probed for point mutations in the catalytic TK domain of epidermal growth factor receptor (mut+). All specimens were examined for somatic mutations by polymerase chain reaction amplification, and all variants were confirmed by multiple independent amplifications. Twenty-five patients were treated with cytoreductive surgery with or without intraperitoneal hyperthermic chemotherapy and complete clinical data including age, sex, cytoreductive score, mutation, and survival were available for comparison of the mut+ and mut- groups. The median age was 56 years, 71% of the patients were male, and the median follow-up time was 14.5 months. Mutations were found in 31% (9 of 29) of the tumors. Seven of these mutations were novel, and one was the L858R mutation described in non-small-cell lung cancer. Of the 25 patients managed surgically, 7 had mut+ and 18 wild type (mut-) disease. Optimal resectability was achieved in 7 (100%) of 7 of mut+ group and 9 (50%) of 18 mut- (p = .026). All mut+ patients are alive with a mean follow-up time of 24 months, whereas 5 (28%) of 18 of the mut- group are dead of disease with a mean follow-up time of 7 months (p = .27). In an analysis of covariance model, only optimal resectability (p = .04) was found to be predictive of survival. EGFR-TK seems to be a common site for mutation in MPM, with mutations being identified in 31% of patients. The EGFR mutations identified included the L858R activating mutation, as well as eight novel EGFR-TK catalytic domain point mutations. These mutations were predictive of optimal resectability, which was the only variable found to be predictive of survival. With longer follow-up, mut+ may not only be predictive of survival but may represent a subset of patients whose disease may be responsive to TK-inhibitor therapy. Experiments confirming the activating properties of the novel mutations are warranted.

Kindler HL.

Section of Hematology/Oncology, University of Chicago, Chicago, IL 60637, USA. hkindler@medicine.bsd.uchicago.edu

Abstract

Systemic therapy is the only treatment option for the majority of mesothelioma patients, for whom age, co-morbid medical illnesses, non-epithelial histology, and locally advanced disease often preclude surgery. For many years, chemotherapy had a minimal impact on the natural history of this cancer, engendering considerable nihilism. Countless drugs were evaluated, most of which achieved response rates below 20% and median survival of <1 year. Several factors have hampered the evaluation of systemic regimens in patients with mesothelioma. The disease is uncommon, affecting only about 2500 Americans annually. Thus, most clinical trials are small, and randomized studies are challenging to accrue. There is significant heterogeneity within the patient populations of these small trials, for several reasons. Since all of the staging systems for mesothelioma are surgically based, it is almost impossible to accurately determine the stage of a patient who has not been resected. Patients
with very early stage disease may be lumped together with far more advanced patients in the same study. The disease itself is heterogenous, with many different prognostic factors, most notably three pathologic subtypes—epithelial, sarcomatoid, and biphasic—that have different natural histories, and varying responses to treatment. Finally, response assessment is problematic, since pleural-based lesions are difficult to measure accurately and reproducibly. Assessment criteria often vary between trials, making some cross-trial comparisons difficult to interpret. Despite these limitations, in recent years, there has been a surge of optimism regarding systemic treatment of this disease. Several cytotoxic agents have been shown to generate reproducible responses, improve quality of life, or prolong survival in mesothelioma. Drugs with single-agent activity include pemetrexed, raltitrexed, vinorelbine, and vinflunine. The addition of pemetrexed or raltitrexed to cisplatin prolongs survival.
The addition of cisplatin to pemetrexed, raltitrexed, gemcitabine, irinotecan, or vinorelbine improves response rate. The combination of pemetrexed plus cisplatin is considered the benchmark front-line regimen for this disease, based on a phase III trial in 456 patients that yielded a response rate of 41% and a median survival of 12.1 months. Vitamin supplementation with folic acid is essential to decrease toxicity, though recent data suggests that there may be an optimum dose of folic acid that should be administered; higher doses may diminish the effectiveness of pemetrexed. There are also several unresolved questions about the duration and timing of treatment with pemetrexed that are the subject of planned clinical trials. It is essential to recognize that the improvements observed with the pemetrexed/cisplatin combination, though real, are still modest. Other active drugs or drug combinations may be more appropriate for specific individuals, and further research is still needed
to improve upon these results. Since the majority of mesotheliomas in the United States occur in the elderly, non-cisplatin-containing pemetrexed combinations may be more appropriate for some patients. Now that effective agents have been developed for initial treatment, several classical cytotoxic drugs and many novel agents are being evaluated in the second-line setting. These include drugs targeted against the epidermal growth factor, platelet-derived growth factor, vascular endothelial growth factor, src kinase, histone deacetylase, the proteasome, and mesothelin. Given the progress made in recent years, there is reason to believe that more effective treatments will continue to be developed.

Baldi A, Mottolese M, Vincenzi B, Campioni M, Mellone P, Di Marino M, di Crescenzo VG, Visca P, Menegozzo S, Spugnini EP, Citro G, Ceribelli A, Mirri A, Chien J, Shridhar V, Ehrmann M, Santini M, Facciolo F.

Department of Biochemistry and Biophysics, Section of Pathology, Second University of Naples, Via L Armanni 5, 80138 Naples, Italy. alfonsobaldi@tiscali.it

Abstract

Aims: The objective of our study was to analyze the potential prognostic value of the expression of the serine protease HtrA1 and of EGFR in 70 malignant mesotheliomas.

Materials & methods: Immunohistochemistry was used to determine the expression of HtrA1 and EGFR. Univariate and multivariate analyses were used to correlate expression of these molecular factors in combination with available clinicopathologic data to patient survival.

Results: A positive, statistically significant relationship has been recorded between HtrA1 expression level and survival (p < 0.0001). By contrast, a negative relationship has been identified between EGFR expression and survival (p = 0.02). Moreover, extension of the tumor (T) and involvement of lymph nodes (N) advanced status (p = 0.001 and 0.002, respectively), as well as the sarcomatoid histotype (p = 0.005), correlated significantly with poor survival. Finally, by a multivariate Cox regression analysis, the only immunohistochemical parameter that resulted to influence overall survival was HtrA1 (p = 0.0001). Interestingly, the prognostic value of HtrA1 expression was completely independent from EGFR expression (p < 0.0001).

Conclusion: This is the first study of the relationship between HtrA1 expression and survival of mesothelioma patients. The data obtained strongly indicate the utilization of HtrA1 expression as a prognostic parameter for mesothelioma and suggest this serine protease as a possible molecular target for the treatment of malignant mesotheliomas.

Okuda K, Sasaki H, Kawano O, Yukiue H, Yokoyama T, Yano M, Fujii Y.

Department of Oncology, Immunology and Surgery, Nagoya City University Graduate School of Medical Science, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, 467-8601, Japan.

Abstract

Epidermal growth factor receptor (EGFR) is overexpressed in a variety of epithelial malignancies. In lung cancer cases, EGFR gene mutation at the kinase domain and EGFR gene amplification are reported to be predictors of the response to EGFR tyrosine kinase inhibitors. In malignant pleural mesothelioma (MPM), the role of EGFR is less clear. We studied EGFR gene mutation, amplification and protein expression in 25 Japanese patients with MPM. None had previously reported EGFR mutations detected by the TaqMan PCR assay. Using immunohistochemistry, 8/25 (32%) cases were positive for the EGFR protein. The cases of sarcomatous type and desmoplastic type were all negative. Fluorescence in situ hybridization analysis revealed three low polysomy cases and one high polysomy case. The low polysomy cases included one biphasic type and two epithelial
types, and the high polysomy case was epithelial type. These four cases expressed EGFR protein. In MPM, EGFR seems to play a role in a limited subset of patients. To identify possible candidates for EGFR tyrosine kinase in inhibitor therapy, the information on the EGFR gene status may be valuable.

Keywords: Malignant pleural mesothelioma, Epidermal growth factor receptor, Amplification, FISH, Immunohistochemistry

Ogino H, Yano S, Kakiuchi S, Yamada T, Ikuta K, Nakataki E, Goto H, Hanibuchi M, Nishioka Y, Ryan A, Sone S.

Department of Internal Medicine and Molecular Therapeutics, Institute of Health Biosciences, University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan.

Abstract

Malignant pleural mesothelioma (MPM) is an aggressive malignancy with a poor prognosis, therefore development of novel effective therapies is urgent. In the present study, we investigated the therapeutic efficacy of vandetanib (ZD6474), an inhibitor of VEGFR-2, EGFR and RET tyrosine kinases, in an orthotopic model of MPM. We found that a human MPM cell line, EHMES-10, expressed RET/PTC3 oncogenic rearrangement and a large amount of VEGF. Vandetanib induced the apoptosis and inhibited the proliferation of EHMES-10 cells in vitro (IC₅₀ = 0.3 μM). Once-daily oral treatment with vandetanib inhibited tumor angiogenesis, and reduced significantly the growth of thoracic tumors and the production of pleural effusions, resulting in the prolonged survival of mice in EHMES-10 orthograft model. In contrast, the selective EGFR tyrosine kinase inhibitor, gefitinib, had no effect against EHMES-10 cells both in vitro and in vivo. Our results suggest that using vandetanib to target RET-dependent tumor cell proliferation and survival and VEGFR-2-dependent tumor angiogenesis may be promising against MPM expressing RET oncogenic rearrangement and VEGF.

Keywords: Malignant pleural mesothelioma; Vandetanib; VEGF; RET; Tyrosine kinase inhibitors

Kothmaier H, Quehenberger F, Halbwedl I, Morbini P, Demirag F, Zeren H, Comin CE, Murer B, Cagle PT, Attanoos R, Gibbs AR, Gallateau-Salle F, Popper HH.

Institute of Pathology, Medical University of Graz, Austria.

Abstract

Malignant pleural mesothelioma (MPM) is an asbestos-related tumour difficult to detect early and treat effectively. Asbestos causes genetic modifications and cell signalling events that favour the resistance of MPM to apoptosis and chemotherapy. Only a small number of patients, approximately 10%, survive more than 3 years. The aim of our study was to assess possible differences within signalling pathways between short-term survivors (survival <3 years; STS) and long-term survivors (survival >3 years; LTS) of MPM. In order to do this, 37 antibodies detecting proteins engaged in cell signalling pathways, enforcing proliferation, anti-apoptosis, angiogenesis, and other cellular activities were investigated by tissue microarray (TMA) technology. Epidermal growth factor receptor (EGFR) is expressed stronger in LTS whereas platelet derived growth factor receptor (PDGFR) signalling is more abundant in STS. The expression of TIE2/Tek, a receptor tyrosine kinases involved in angiogenesis, is differentially regulated via PDGFR and thus is more important in STS. Anti-apoptosis is upregulated in STS by signal transducer and activator of transcription 1 (STAT1)-survivin and related molecules, but not in LTS. Our study provides novel insights into the regulatory mechanisms of signalling pathways in MPM, which differentially promote tumour growth in LTS and STS. We demonstrate that small scale proteomics can be carried out by a powerful linkage of TMA, immunohistochemistry, and statistical methods to identify proteins which might be relevant targets for therapeutic intervention.

Watzka SB, Setinek U, Huber M, Cantonati H, Lax F, Watson S, Weigel G, Mueller MR.

Otto Wagner Hospital, Vienna, Austria.

Abstract

Integrin-linked kinase (ILK) is a protein kinase that links integrins and growth factors to a range of signalling pathways. ILK expression and activity are increased in a variety of human cancers. However, little is known regarding the role of ILK in malignant pleural mesothelioma (MPM). In this study, we assessed the expression of ILK in samples of human MPM, and compared it with the expression of epidermal growth factor receptor (EGFR). Thirty-four samples of human malignant mesothelioma were stained with a polyclonal antibody against ILK. Two independent observers evaluated the morphological pattern and intensity of staining. The findings have been compared with the patient’s characteristics. Most MPM and mesothelial cell proliferation samples (87.9%) showed cytoplasmic ILK staining of varying intensity. Normal mesothelial cells and normal lung parenchyma did not stain for ILK at all. Conversely, the percentage of positive EGFR staining was somewhat lower (75.8%). The ILK-positive patients were significantly older than the ILK-negative patients. Here we report for the first time that ILK is indeed expressed in malignant mesothelioma. For further validation of a causal association between ILK and neoplastic mesothelial transformation, these immunohistochemical results should be supplemented with clinical and molecular biological data.

Keywords: Mesothelioma; Integrin-linked kinase; Immunohistochemistry; Epidermal growth factor receptor.