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.

Gnoni A, Marech I, Silvestris N, Vacca A, Lorusso V.

Medical Oncology Unit, Hospital Vito Fazzi – Lecce, Italy. vitolorusso@inwind.it.

Abstract

Dasatinib (BMS-354825, Sprycel®) is an oral, multitargeted inhibitor of receptor tyrosine kinases (RTKs), including BCR-ABL fusion protein, stem cell factor receptor (c-KIT), platelet-derived growth factor receptor (PDGFR), and Src family kinases (SFKs). Several early- and late-phase clinical trials for chronic myelogeneous leukaemia (CML) have demonstrated the direct inhibition of BCR-ABL fusion protein and SFKs, which led to dasatinib approval by the Food and Drug Administration (FDA) and the European Union for the treatment of imatinib-resistant or -intolerant CML, and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL). Phase III dose-optimization study was performed to compare different regimens, stating that dasatinib 100 mg once daily is now the recommended schedule for patients with chronic CML, and 140 mg once daily for patients with accelerated phase or myeloid or lymphoid blast phase CML, and for patients with Ph+ ALL until progression. Because of the myriad of critical roles of SFKs in biological processes, SFKs inhibition could induce numerous biological responses. Ongoing clinical trials evaluate dasatinib in the treatment of several solid tumours, including gastrointestinal stromal tumours (GIST), prostate cancer, malignant pleural mesothelioma, sarcomas, NSCLC, colorectal cancer, glioblastoma and other haematologic malignances as multiple myeloma. Ongoing pre-clinical studies assess the therapeutic potential of dasatinib in other solid tumours, including melanoma, head and neck cancer, breast cancer and ovarian cancer. Dasatinib is generally well tolerated. Myelosuppression is the common adverse event which is, however, reversible by dose reduction, discontinuation, or interruption. Thrombocytopenia is more significant than neutropenia and associated to gastrointestinal bleeding and CNS haemorrhage. The most common non-haematologic adverse events include gastrointestinal symptoms (diarrhoea, nausea, vomiting, abdominal pain and anorexia), headache, peripheral edema, and pleural effusion. In respect of these encouraging studies investigating dasatinib in the treatment of patients with GIST, prostate cancer, multiple myeloma and sarcomas, ongoing phase III clinical trials warrant the drug evaluation as recommended agent for the treatment of these diseases, also in association with chemoterapy or other targeted therapies.

Shapiro GI, Tibes R, Gordon MS, Wong BY, Eder JP, Borad MJ, Mendelson DS, Vogelzang NJ, Bastos BR, Weiss GJ, Fernandez C, Sutherland W, Sato H, Pierceall WE, Weaver D, Slough S, Wasserman E, Kufe DW, Von Hoff DD, Kawabe T, Sharma S.

Department of Medical Oncology, Dana Farber Cancer Institute.

Abstract

Purpose: Two phase I dose-escalation studies were conducted to determine the maximum tolerated dose (MTD) and safety profile of the G2 checkpoint abrogator CBP501, as a single agent and in combination with cisplatin.

Experimental Design: Patients with advanced solid tumors were treated with CBP501 alone (D1/D8/D15, q4w, from 0.9 mg/m²), or with cisplatin (both on D1, q3w, from 3.6 mg/m² CBP501, 50 mg/m² cisplatin). Dose escalation proceeded if dose-limiting toxicity (DLT) was observed in ≤1 of 3-6 patients; CBP501 dose increments were implemented according to the incidence of toxicity. MTD was determined from DLTs occurring during the first two cycles.

Results: In the combination study, the DLT was a histamine-release syndrome (HRS) occurring 10-60 minutes after initiating infusion that was attenuated by prophylaxis comprising dexamethasone, diphenhydramine, ranitidine and loratadine. The MTD was 25 mg/m² CBP501 and 75 mg/m² cisplatin, with 2 patients at the highest dose (36.4 mg/m² CBP501, 75 mg/m² cisplatin) experiencing grade 3 HRS. The only DLT with monotherapy was transient G3 rise of troponin in one patient. Grade 3-4 treatment-related events were rare. Promising activity was observed with CBP501/cisplatin, mainly in ovarian and mesothelioma patients who had previously progressed on platinum-containing regimens. Among ovarian cancer patients, low expression of DNA repair proteins was associated with partial response or stable disease.

Conclusions: CBP501 is well tolerated in patients as monotherapy and with cisplatin. At the recommended phase 2 dose (RP2D) the combination is feasible and HRS manageable with prophylaxis. Evidence of anti-tumor activity was observed in platinum-resistant patients.

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.

Yano S, Li Q, Wang W, Yamada T, Takeuchi S, Nakataki E, Ogino H, Goto H, Nishioka Y, Sone S.

Division of Medical Oncology, Cancer Research Institute, Kanazawa University. Kanazawa, Ishikawa 920-0934.

Abstract

Malignant pleural mesothelioma (MPM), arises from the mesothelial cells, is difficult to be diagnosed at an early stage, and is refractory to conventional chemotherapy and radiotherapy. Therefore, the establishment of novel effective therapies is necessary to improve the prognosis for many patients with this disease. Recent studies have demonstrated that angiogenesis plays a significant role in MPM progression, suggesting the importance of tumor vessels as therapeutic targets. To explore molecular pathogenesis and evaluate the efficacy of vascular targeting therapy in MPM, we developed orthotopic implantation SCID mouse models of MPM. We found that selective VEGF inhibitors were effective only in the treatment of high-VEGF-producing MPM models. On the other hand, multiple kinase inhibitor E7080, with inhibitory activity against various angiogenic cytokine receptors, suppressed the progression and prolonged survival of both high-VEGF-producing and low-VEGF-producing MPM models. Further understanding of the functional characteristics of tumor angiogenesis may be essential to improve targeting therapies in MPM. In this review, we introduce current status of clinical strategies and novel therapeutic approaches against angiogenesis in MPM.

Nie HG, Tucker T, Su XF, Na T, Peng JB, Smith PR, Idell S, Ji HL.

Biochemistry, University of Texas Health Science Center at Tyler, Texas Lung Injury Institute, Tyler, Texas, United States; Pharmacology, China Medical University, School of Pharmaceutical Sciences, Shenyang, China.

Abstract

Pleural effusions are commonly clinical disorders, resulting from the imbalance between pleural fluid turnover and re-absorption. The mechanisms underlying pleural fluid clearance across the mesothelium remain to be elucidated. We hypothesized that ENaC is expressed and forms the molecular basis of the amiloride-sensitive resistance in human mesothelial cells. Our RT-PCR results showed that four ENaC subunits, namely, [alpha], [beta], [gamma], and two [delta] ENaC subunits are expressed in human primary pleural mesothelial cells, a human mesothelioma cell line (M9K), and mouse pleural tissue. In addition, Western blotting and immunofluorescence microscopy studies revealed that [alpha], [beta], [gamma], and [delta] ENaC subunits are expressed in primary human mesothelial cells and M9K cells at the protein level. An amiloride-inhibitable short-circuit current was detected in M9K monolayers and mouse pleural tissues when mounted in Ussing chambers. Whole-cell patch clamp recordings showed an ENaC-like channel with an amiloride IC₅₀ of 12 M in M9K cells. This cation channel has a high affinity for extracellular Na+ ions (Km: 53mM). The ion selectivity of this channel to cations follows the same order as ENaC: Li⁺ > Na⁺ > K⁺. The unitary Li⁺ conductance was 15 pS in on-cell patches. Four ENaC subunits form a functional Na⁺ channels when co-injected into Xenopus oocytes. Furthermore, we found that both forskolin and cGMP increased the short-circuit currents in mouse pleural tissues. Taken together, our data demonstrate that the ENaC channels are biochemically and functionally expressed in human pleural mesothelial cells, and can be up-regulated by cAMP and cGMP.

Keywords: Ussing chamber, protein kinase, human primary mesothelial cells, amiloride

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.

Faoro, Leonardo a; Loganathan, Sivakumar a; Westerhoff, Maria b; Modi, Rahul a; Husain, Aliya N. b; Tretiakova, Maria b; Seiwert, Tanguy a; Kindler, Hedy L. a; Vokes, Everett E. a; Salgia, Ravi a

Abstract

Malignant pleural mesothelioma (MPM) is a disease with few therapeutic options. Protein kinase C beta (PKC[beta]) is involved in important cellular functions. Enzastaurin (LY317615.HCl) is a novel inhibitor of PKC in clinical development. MPM cell lines (7) and patient tumor tissues (24) were evaluated for expression of PKC[beta] by immunoblotting and immunohistochemistry, respectively. In-vitro cell growth assays were performed with enzastaurin with or without cisplatin. Cell migration was evaluated with the wound healing assay. Downstream signaling (survival and focal adhesion pathways) was studied by immunoblotting for related molecules in the presence of phorbol ester with or without enzastaurin. Expression for PKC[beta]1 was seen in all cases, with a mean integrated optical density of 152.5 (standard deviation=95.47, n=24), whereas PKC[beta]2 expression was less intense, with a mean integrated optical density of 11.45 (standard deviation=16.27, n=21). There was a trend toward lower overall survival among patients expressing above-median PKC[beta]1 (P=0.064), but not PKC[beta]2. Robust expression of PKC[beta]1 and low expression of PKC[beta]2 were observed in MPM cell lines. Treatment of MPM cell lines with enzastaurin revealed an IC50 of 5 [mu]mol/l, and strong synergism was observed when combined with cisplatin. Wound healing assay revealed that treatment of H2461 cells with enzastaurin reduced migration by 59.2%. Enzastaurin treatment led to disruption of F-actin architecture. Downstream signaling showed reduced phosphorylation of AKT, FAK (focal adhesion kinase), p130Cas, S6 ribosomal protein, and paxillin. PKC[beta]1 was expressed in the majority of MPM samples. Enzastaurin has preclinical activity against MPM, and exhibited synergism with cisplatin. PKC[beta] inhibition in MPM might be able to reduce the invasiveness of MPM by affecting cytoskeletal function.

Lazzarini R, Moretti S, Orecchia S, Betta PG, Procopio A, Catalano A.

Department of Molecular Pathology and Innovative Therapies, Marche University, Ancona, Italy.

Abstract

Purpose: The p21 cyclin-dependent kinase inhibitor was frequently expressed in human malignant pleural mesothelioma (MPM) tissues as well as cell lines. Recent data indicate that p21 keeps tumor cells alive after DNA damage, favoring a survival advantage. In this study, we assessed the possibility of p21 suppression as a therapeutic target for MPM.

Experimental Design: We established two different MPM-derived (from H28 and H2052 cells) subclones using vector-based short hairpin RNA (shRNA). Then, chemosensitivity against low doses of antineoplastic DNA-damaging agents was investigated by colony formation assays, and furthermore, the type of cell response induced by these drugs was analyzed. To examine the effect of p21 shRNA on chemosensitivity in vivo, tumor formation assays in nude mice were done.

Results: In colony formation assay, the IC₅₀ of doxorubicin was 33 ± 3.0 nmol/L in p21 shRNA-transfected cells with respect to 125 ± 10 nmol/L of control vector–transfected cells. This enhancement of growth inhibition was achieved by converting a senescence-like growth arrest to apoptosis in response to doxorubicin, etoposide, and CPT11. In the in vivo assays, CPT11 and loss-of-expression of p21 in combination led to considerable suppression of tumor growth associated with a substantially enhanced apoptotic response, whereas CPT11 alone was ineffective at inducing these responses.

Conclusions: These results indicated that p21 might play an important role in chemosensitivity to anticancer agents, and the suppression of its expression might be a potential therapeutic target for MPM.

Cipriani NA, Abidoye OO, Vokes E, Salgia R.

Section of Hematology/Oncology, Department of Medicine, University of Chicago Medical Center, Chicago, IL 60637, United States; Department of Pathology, and University of Chicago Cancer Research Center, University of Chicago Medical Center, Chicago, IL 60637, United States.

Abstract

The receptor tyrosine kinase MET has been studied of a large variety of human cancers, including lung and mesothelioma. The MET receptor and its ligand HGF (hepatocyte growth factor) play important roles in cell growth, survival and migration, and dysregulation of the HGF-MET pathway leads to oncogenic changes including tumor proliferation, angiogenesis and metastasis. In small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), and malignant pleural mesothelioma (MPM), MET is dysregulated via overexpression, constitutive activation, gene amplification, ligand-dependent activation, mutation or epigenetic mechanisms. New drugs targeted against MET and HGF are currently being investigated in vitro and in vivo, with promising results. These drugs function at a variety of steps within the HGF-MET pathway, including MET expression at the RNA or protein level, the ligand-receptor interaction, and tyrosine kinase function. This paper will review the structure, function, mechanisms of tumorigenesis, and potential for therapeutic inhibition of the MET receptor in lung cancer and mesothelioma.