Calabrò L, Sigalotti L, Fonsatti E, Bertocci E, Di Giacomo AM, Danielli R, Cutaia O, Colizzi F, Covre A, Mutti L, Natali PG, Maio M.

Division of Medical Oncology and Immunotherapy, Department of Oncology, University Hospital of Siena, Istituto Toscano Tumori, Siena, Italy.

Abstract

No treatment prolongs the survival of malignant mesothelioma (MM) patients. Since MM elicits anti-tumor host’s immune responses, immunotherapy represents a promising strategy for its control. Immunomodulatory antibodies against components of the B7 family of immunomodulatory molecules that regulate T cell activation are being investigated in human malignancies including MM. The expression of B7-H3, a new component of the B7 family was investigated in primary cultures of human mesothelial cells (HMC) and in MM cell lines by flow cytometry and molecular analyses, and in MM tissues by immunohistochemistry. The role of DNA hypomethylating agents in modulating levels of B7-H3 expression in MM cells was also studied. Reverse transcriptase-polymerase chain reaction (RT-PCR) demonstrated that B7-H3 mRNA was consistently detectable in mesothelial and MM cells investigated; however, real-time quantitative RT-PCR analyses showed highly heterogeneous levels of B7-H3 mRNA among investigated MM cells. The analysis of B7-H3 protein expression indicated that comparable levels of B7-H3 were expressed on both cell types. Treatment with the DNA hypomethylating agent 5-aza-2′-deoxycytidine did not significantly affect the expression of B7-H3 mRNA in MM cells. In vivo, while B7-H3 was expressed in all 13 tumor biopsies of the epithelial variant, with high levels in 54% of cases, it was rarely detectable in spindle type MM in which 1/5 biopsies weakly expressed B7-H3. These findings suggest that B7-H3 is a promising target for new immunotherapeutic strategies in MM, with particular emphasis in the epithelial variant.

Keywords: B7-H3; Mesothelioma; B7 family; Immunotherapy

Kim S, Buchlis G, Fridlender ZG, Sun J, Kapoor V, Cheng G, Haas A, Cheung HK, Zhang X, Corbley M, Kaiser LR, Ling L, Albelda SM.

Thoracic Oncology Research Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6160, USA.

Abstract

Locally produced transforming growth factor-beta (TGF-beta) promotes tumor-induced immunosuppression and contributes to resistance to immunotherapy. This article explores the potential for increased efficacy when combining immunotherapies with TGF-beta suppression using the TGF-beta type I receptor kinase inhibitor SM16. Adenovirus expressing IFN-beta (Ad.IFN-beta) was injected intratumorally once in established s.c. AB12 (mesothelioma) and LKR (lung cancer) tumors or intratracheally in a Kras orthotopic lung tumor model. Mice bearing TC1 (lung cancer) tumors were vaccinated with two injections of adenovirus expressing human papillomavirus-E7 (HPV-E7; Ad.E7). SM16 was administered orally in formulated chow. Tumor growth was assessed and cytokine expression and cell populations were measured in tumors and spleens by real-time PCR and flow cytometry. SM16 potentiated the efficacy of both immunotherapies in each of the models and caused changes in the tumor microenvironment. The combination of SM16 and Ad.IFN-beta increased the number of intratumoral leukocytes (including macrophages, natural killer cells, and CD8(+) cells) and increased the percentage of T cells expressing the activation marker CD25. SM16 also augmented the antitumor effects of Ad.E7 in the TC1 flank tumor model. The combination did not increase HPV-E7 tetramer-positive CD8(+) T cells in the spleens but did induce a marked increase in the tumors. Tumors from SM16-treated mice showed increased mRNA and protein for immunostimulatory cytokines and chemokines, as well as endothelial adhesion molecules, suggesting a mechanism for the increased intratumoral leukocyte trafficking. Blockade of the TGF-beta signaling pathway augments the antitumor effects of Ad.IFN-beta immune-activating or Ad.E7 vaccination therapy. The addition of TGF-beta blocking agents in clinical trials of immunotherapies may increase efficacy.

van der Most RG, Currie AJ, Mahendran S, Prosser A, Darabi A, Robinson BW, Nowak AK, Lake RA.

National Centre for Asbestos Related Diseases, School of Medicine and Pharmacology, University of Western Australia, Perth, Australia. robbertvdm@gmail.com

Abstract

Tumor cell death potentially engages with the immune system. However, the efficacy of anti-tumor chemotherapy may be limited by tumor-driven immunosuppression, e.g., through CD25+ regulatory T cells. We addressed this question in a mouse model of mesothelioma by depleting or reconstituting CD25+ regulatory T cells in combination with two different chemotherapeutic drugs. We found that the efficacy of cyclophosphamide to eradicate established tumors, which has been linked to regulatory T cell depletion, was negated by adoptive transfer of CD25+ regulatory T cells. Analysis of post-chemotherapy regulatory T cell populations revealed that cyclophosphamide depleted cycling (Ki-67(hi)) T cells, including foxp3+ regulatory CD4+ T cells. Ki-67(hi) CD4+ T cells expressed increased levels of two markers, TNFR2 and ICOS, that have been associated with a maximally suppressive phenotype according to recently published studies. This suggest that cyclophosphamide depletes a population of maximally suppressive regulatory T cells, which may explain its superior anti-tumor efficacy in our model. Our data suggest that regulatory T cell depletion could be used to improve the efficacy of anti-cancer chemotherapy regimens. Indeed, we observed that the drug gemcitabine, which does not deplete cycling regulatory T cells, eradicates established tumors in mice only when CD25+ CD4+ T cells are concurrently depleted. Cyclophosphamide could be used to achieve regulatory T cell depletion in combination with chemotherapy.

Keywords: Tumor immunity – Regulatory CD4+ T cells – Chemotherapy – Mesothelioma – Gemcitabine – Cyclophosphamide

Inami K, Kajino K, Abe M, Hagiwara Y, Maeda M, Suyama M, Watanabe S, Hino O.

Department of Pathology and Oncology, Juntendo University School of Medicine, Tokyo 113-8421, Japan.

Abstract

ERC/mesothelin gene (MSLN) encodes a precursor protein, which is cleaved by proteases to generate N-ERC/mesothelin and C-ERC/mesothelin. N-ERC/mesothelin is a soluble protein, also known as megakaryocyte-potentiating factor, which is released into extracellular space. N-ERC/mesothelin is known to be a serum marker of mesothelioma. We have previously developed an enzyme-linked immunosorbent assay system for N-ERC/mesothelin, which can detect mesothelioma. C-ERC/mesothelin is expressed in normal mesothelial cell, pancreatic cancers, ovarian cancers, mesotheliomas and some other cancers. Pancreatic ductal carcinoma remains a fatal disease because its diagnosis often occurs very late. In this study, we examined ERC/mesothelin expression in human pancreatic cancer cell lines (MIA-PaCa2, PK-1, KP-3, TCC-PAN2, PK-59 and PK-45H) by reverse transcription-polymerase chain reaction and immunoblotting and N-ERC/mesothelin concentration in the supernatant of cultured cancer cells by the ELISA system.
We also investigated C-ERC/mesothlein expression in human pancreatic ductal carcinoma tissues by immunostaining using 5B2 anti-mesothelin monoclonal antibody and N-ERC/mesothelin concentration in sera obtained from patients with pancreatic ductal carcinoma via ELISA. In vitro, N-ERC/mesothelin concentration in cell culture medium nearly correlated with the expression level of C-ERC/mesothelin. Although C-ERC/mesothelin was frequently expressed in human pancreatic ductal carcinoma, serum N-ERC/mesothelin concentration of cancer patients was equivalent to healthy controls. N-ERC/mesothelin was not useful as a serum marker of pancreatic ductal carcinoma, but because of frequent expression, C-ERC/mesothelin might be useful as a target of molecular imaging and immunotherapy.

Stoppoloni D, Cardillo I, Verdina A, Vincenzi B, Menegozzo S, Santini M, Sacchi A, Baldi A, Galati R.

Laboratory D, Department for the Development of Therapeutic Programs, Centro Ricerca Sperimentale, Regina Elena Cancer Institute, Rome, Italy.

Abstract

Background:
The human embryonic lethal abnormal vision (ELAV)-like protein HuR is a messenger RNA (mRNA)-binding protein that controls the stability of certain transcripts, including cyclooxygenase2 (COX-2).

Methods:
To investigate a possible contribution of dysregulation of mRNA stability to the progression of cancer and to COX-2 over expression in mesothelioma, the authors studied expression of COX-2 and HuR in 5 mesothelioma cell lines (MSTO, NCI, Ist-Mes1, Ist-Mes2, and MPP89) and in a group of 29 human mesothelioma specimens that were characterized previously for COX-2 expression.

Results:
All 5 cell lines expressed HuR, whereas COX-2 was not detectable in MSTO or NCI cells. Treatment with cytokines induced a shift in systolic HuR protein levels in MPP89 and Ist-Mes2 cells that was accompanied by an increase in the expression of COX-2 mRNA and protein. In Ist-Mes1 cells, cytokine stimulation did not cause the passage of HuR from nucleus to cytoplasm, and the synthesis of COX-2 did not increase. In tumor tissues, immunohistochemistry revealed a positive, statistically significant correlation between high COX-2 expression and cytoplasmic localization of HuR (P = .016). Moreover, on univariate analysis, overall survival was found to be influenced strongly by cytoplasmic HuR localization (P = .004).

Conclusions:
The current results suggested that HuR plays a role in tumor progression in mesothelioma and that COX-2 may be a target of its activity in neoplastic cells. Together, these observations indicate that strategies aiming toward the modulation of HuR may have a potential clinical benefit in mesothelioma.

Keywords: human embryonic lethal abnormal vision-like protein, cyclooxygenase-2, mesothelioma, prognosis, immunohistochemistry

Yamada T, Yano S, Ogino H, Ikuta K, Kakiuchi S, Hanibuchi M, Kanematsu T, Taniguchi T, Sekido Y, 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

Lysophosphatidic acid (LPA) is one of the simplest natural phospholipids. This phospholipid is recognized as an extracellular potent lipid mediator with diverse effects on various cells. Although LPA is shown to stimulate proliferation and motility via LPA receptors, LPA₁ and LPA₂, in several cancer cell lines, the role of LPA and LPA receptors for malignant pleural mesothelioma (MPM) has been unknown. MPM is an aggressive malignancy with a poor prognosis and the incidence is increasing and is expected to increase further for another 10–20 years worldwide. Therefore, the development of novel effective therapies is needed urgently. In this study, we investigated the effect of LPA on the proliferation and motility of MPM cells. We found that all 12 cell lines and four clinical samples of MPM expressed LPA₁, and some of them expressed LPA₂, LPA₃, LPA₄ and LPA₅. LPA stimulated the proliferation and motility of MPM cells in a dose-dependent manner. Moreover, LPA-induced proliferation was inhibited by Ki16425, an inhibitor of LPA₁, and small interfering RNA against LPA₁, but not LPA₂. Interestingly, LPA-induced motility was inhibited by small interfering RNA against LPA₂, but not LPA₁, unlike a number of previous reports. These results indicate that LPA is a critical factor on proliferation though LPA₁, and on motility though LPA₂ in MPM cells. Therefore, LPA and LPA receptors, LPA₂ as well as LPA₁, represent potential therapeutic targets for patients with MPM.

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.

Kusano K, Thomas TN, Fujiwara K.

Aab Cardiovascular Research Institute, University of Rochester School of Medicine and Dentistry, Rochester, New York 14586, USA.

Abstract

Protein-zero related (PZR) is an immunoglobulin V (IgV)-type immunoreceptor with two immunoreceptor tyrosine-based inhibitory motifs (ITIMs). PZR interacts with Src homology 2 domain-containing tyrosine phosphatase (SHP-2) via its tyrosine-phosphorylated ITIMs, for which c-Src is a putative kinase. Towards elucidating PZR function in endothelial cells (ECs), the authors cloned PZR from bovine aortic endothelial cells (BAECs) and characterized it. Mature bovine PZR had 94.8% and 92.7% sequence identity with canine and human proteins, respectively, and the two ITIM sequences were conserved among higher vertebrates. PZR was expressed in many cell types and was localized to cell contacts and intracellular granules in BAECs and mesothelioma (REN) cells. Coimmunoprecipitation revealed that PZR, Grb-2-associated binder-1 (Gab1), and platelet endothelial cell adhesion molecule-1 (PECAM-1) were three major SHP-2-binding proteins in BAECs. H(2)O(2) enhanced PZR tyrosine phosphorylation and PZR/SHP-2 interaction in ECs in a dose-and time-dependent manner. To see if tyrosine kinases other than Src are also capable of phosphorylating PZR, the authors cotransfected HEK293 cells with PZR and one of several tyrosine kinases and found that c-Src, c-Fyn, c-Lyn, Csk, and c-Abl, but not c-Fes, phosphorylated PZR and increased PZR/SHP-2 interaction. These results suggest that PZR is a cell adhesion protein that may be involved in SHP-2-dependent signaling at interendothelial cell contacts.

Keywords: Cell Contacts; Endothelial Cells; ITIM; Protein Zero Related (PZR); SHP-2; Tyrosine Phosphorylation

Zervos MD, Bizekis C, Pass HI.

Department of Cardiothoracic Surgery, Division of Thoracic Surgery, New York University School of Medicine, New York, USA. zervom01@med.nyu.edu

Abstract

Purpose of review: Mesothelioma is an aggressive malignancy of the pleura with poor survival. There will be approximately 3000 cases of mesothelioma in the United States annually. Multimodality treatment including neoadjuvant chemotherapy in selected individuals followed by extrapleural pneumonectomy and radiation has been studied in recent trials for its effects on disease free and overall survival This review provides a general overview of malignant mesothelioma with a summary of the most significant articles from within the past year as well as from the past.

Recent findings: Areas of recent interest include the evaluation of osteopontin and mesothelin as new tumor markers for mesothelioma. New phase III trials have been performed to evaluate the use of combined chemotherapy regimens.

Summary: Malignant mesothelioma is a very difficult malignancy to treat. Patients with the disease usually have an occupational asbestos exposure, and in some, viral exposure with SV40. There have been many historical treatments including combinations of local control with surgery and radiation as well as attempts to prevent systemic failure with chemotherapy. Novel therapies including intrapleural chemotherapy, photodynamic therapy and hyperthermic perfusion have also been used with some success. Finally there are several attempts at immunomodulating and targeted treatments, which are in phase I/II trials.

Clayton A, Mitchell JP, Court J, Linnane S, Mason MD, Tabi Z.

Department of Oncology and Palliative Medicine, School of Medicine, Cardiff University, Velindre Cancer Centre, Whitchurch, Cardiff, United Kingdom;

Abstract

NKG2D is an activating receptor for NK, NKT, CD8⁺, and γδ⁺ T cells, whose aberrant loss in cancer is a key mechanism of immune evasion. Soluble NKG2D ligands and growth factors, such as TGFβ1 emanating from tumors, are mechanisms for down-regulating NKG2D expression. Cancers thereby impair the capacity of lymphocytes to recognize and destroy them. In this study, we show that exosomes derived from cancer cells express ligands for NKG2D and express TGFβ1, and we investigate the impact of such exosomes on CD8⁺ T and NK cell NKG2D expression and on NKG2D-dependent functions. Exosomes produced by various cancer cell lines in vitro, or isolated from pleural effusions of mesothelioma patients triggered down-regulation of surface NKG2D expression by NK cells and CD8⁺ T cells. This decrease was rapid, sustained, and resulted from direct interactions between exosomes and NK cells or CD8⁺ T cells. Other markers (CD4, CD8, CD56, CD16, CD94, or CD69) remained unchanged, indicating the selectivity and nonactivatory nature of the response. Exosomal NKG2D ligands were partially responsible for this effect, as down-modulation of NKG2D was slightly attenuated in the presence of MICA-specific Ab. In contrast, TGFβ1-neutralizing Ab strongly abrogated NKG2D down-modulation, suggesting exosomally expressed TGFβ as the principal mechanism. Lymphocyte effector function was impaired by pretreatment with tumor exosomes, as these cells exhibited poor NKG2D-dependent production of IFN-γ and poor NKG2D-dependent killing function. This hyporesponsiveness was evident even in the presence of IL-15, a strong inducer of NKG2D. Our data show that NKG2D is a likely physiological target for exosome-mediated immune evasion in cancer.