Target In Malignant Pleural Mesothelioma Research Articles

POLD1 Is Required for Cell Cycle Progression by Overcoming DNA Damage in Malignant Pleural Mesothelioma.

The prognosis of patients with malignant pleural mesothelioma (MPM) remains poor due to lack of effective therapeutic targets. DNA damage caused by long-time exposure to asbestos fibers has been associated with the development of MPM, with mutations at genes encoding DNA damage repair (DDR)-related molecules frequently expressed in patients with MPM. The present study was designed to identify novel therapeutic targets in MPM using large public databases, such as The Cancer Genome Atlas (TCGA) and Genotype Tissue Expression project (GTEx) focused on DDR pathways. The correlations between mRNA expression levels of DDR-related genes and overall survival (OS) were analyzed in mesothelioma patients in TCGA mesothelioma (TCGA-MESO) datasets. The anti-tumor effects of small interfering RNAs (siRNA) against DDR-related genes associated with OS were subsequently tested in MPM cell lines. High levels of mRNA encoding DNA polymerase delta 1, catalytic subunit (POLD1) were significantly associated with reduced OS in patients with MPM (p<0.001, Log-rank test). In addition, siRNA targeting POLD1 (siPOLD1) caused cell cycle arrest at the G1/S checkpoint and induced apoptosis involving accumulation of DNA damage in MPM cell lines. POLD1 plays essential roles in overcoming DNA damage and cell cycle progression at the G1/S checkpoint in MPM cells. These findings suggest that POLD1 may be a novel therapeutic target in MPM.

Chronic Inflammation, Oxidative Stress and Metabolic Plasticity: Three Players Driving the Pro-Tumorigenic Microenvironment in Malignant Mesothelioma.

Malignant pleural mesothelioma (MPM) is a lethal and rare cancer, even if its incidence has continuously increased all over the world. Asbestos exposure leads to the development of mesothelioma through multiple mechanisms, including chronic inflammation, oxidative stress with reactive oxygen species (ROS) generation, and persistent aberrant signaling. Together, these processes, over the years, force normal mesothelial cells' transformation. Chronic inflammation supported by "frustrated" macrophages exposed to asbestos fibers is also boosted by the release of pro-inflammatory cytokines, chemokines, growth factors, damage-associated molecular proteins (DAMPs), and the generation of ROS. In addition, the hypoxic microenvironment influences MPM and immune cells' features, leading to a significant rewiring of metabolism and phenotypic plasticity, thereby supporting tumor aggressiveness and modulating infiltrating immune cell responses. This review provides an overview of the complex tumor-host interactions within the MPM tumor microenvironment at different levels, i.e., soluble factors, metabolic crosstalk, and oxidative stress, and explains how these players supporting tumor transformation and progression may become potential and novel therapeutic targets in MPM.

AXL and MET Tyrosine Kinase Receptors Co-Expression as a Potential Therapeutic Target in Malignant Pleural Mesothelioma.

Malignant pleural mesothelioma (MPM) is a highly lethal malignancy that unfortunately cannot benefit from molecularly targeted therapies. Although previous results showed the pivotal role of various receptor tyrosine kinases (RTKs) in MPM tumorigenesis, the treatment with a single inhibitor targeting one specific RTK has been shown to be ineffective in MPM patients. The main aim of the present study was to investigate the potential role of AXL and MET receptors in MPM and the possible efficacy of treatment with AXL and MET multitarget inhibitors. Immunohistochemical and FISH analyses were performed in a wide series of formalin-fixed paraffin-embedded MPM samples to detect the expression of two receptors and the potential gene amplification. In vitro studies were performed to evaluate putative correlations between the target's expression and the cell sensitivity to AXL-MET multitarget inhibitors. In our series, 10.4% of cases showed a co-expression of AXL and MET, regardless of their ligand expression, and the gene amplification. Furthermore, our in vitro results suggest that the concomitant pharmacological inhibition of AXL and MET may affect the proliferative and aggressiveness of MPM cells. In conclusion, the subset of MPM patients with AXL-MET co-activation could benefit from treatment with specific multitarget inhibitors.

Comprehensive genomic and tumour immune profiling reveals potential therapeutic targets in malignant pleural mesothelioma

BackgroundMalignant pleural mesothelioma (MPM) has a poor overall survival with few treatment options. Whole genome sequencing (WGS) combined with the immune features of MPM offers the prospect of identifying changes that could inform future clinical trials.MethodsWe analysed somatic mutations from 229 MPM samples, including previously published data and 58 samples that had undergone WGS within this study. This was combined with RNA-seq analysis to characterize the tumour immune environment.ResultsThe comprehensive genome analysis identified 12 driver genes, including new candidate genes. Whole genome doubling was a frequent event that correlated with shorter survival. Mutational signature analysis revealed SBS5/40 were dominant in 93% of samples, and defects in homologous recombination repair were infrequent in our cohort. The tumour immune environment contained high M2 macrophage infiltrate linked with MMP2, MMP14, TGFB1 and CCL2 expression, representing an immune suppressive environment. The expression of TGFB1 was associated with overall survival. A small subset of samples (less than 10%) had a higher proportion of CD8 T cells and a high cytolytic score, suggesting a ‘hot’ immune environment independent of the somatic mutations.ConclusionsWe propose accounting for genomic and immune microenvironment status may influence therapeutic planning in the future.

A3 Adenosine and P2X7 Purinergic Receptors as New Targets for an Innovative Pharmacological Therapy of Malignant Pleural Mesothelioma.

Human malignant pleural mesothelioma (MPM) is a rare, but aggressive tumor of the serosal cavities whose 5-year survival rate is 15%. At present, there are no effective therapies for MPM. Although recent findings suggest that A3 adenosine (A3AR) and P2X7 (P2X7R) receptors can be employed as antitumoral pharmacological targets in MPM, their potential role in a combined therapy is currently unknown. The A3AR agonist Cl-IB-MECA and the P2X7 receptor antagonist AZ10606120, as a single compound or in combination, were investigated in vitro for their anti-tumor activities. Assays were carried out in MPM cell lines IST-Mes2 and MPP89 and in primary human normal mesothelial cells (HMCs), as control. Single treatment with Cl-IB-MECA reduced cell proliferation and favored a pro-apoptotic effect in both MPP89 and IST-Mes2 cell lines, whereas AZ10606120 inhibited cell proliferation and induced apoptosis in IST-Mes2, only. The combined treatment with Cl-IB-MECA and AZ10606120 reduced cell proliferation and favored apoptosis in MPP89 and IST-Mes2 cell lines, whereas no synergistic effect was detected. These data cumulatively suggest the absence of a synergistic effect in combined targeting of A3 adenosine and P2X7 receptors of MPM cell lines. This study may stimulate further investigations aimed at determining new combinations of antitumor compounds and more effective therapeutic strategies against MPM.

Hitting the Bull's-Eye: Mesothelin's Role as a Biomarker and Therapeutic Target for Malignant Pleural Mesothelioma.

Simple SummaryMesothelioma is a deadly disease with a dismal prognosis. Since its discovery, mesothelin, a cell surface protein, has been a promising biomarker and therapeutic target due to its overexpression in mesothelioma and limited expression in normal cells. This review summarizes the clinical studies that have examined mesothelin as a biomarker and therapeutic target in mesothelioma and explores future perspectives in its role to improve patient management.Malignant pleural mesothelioma (MPM) is an aggressive cancer with limited treatment options and poor prognosis. MPM originates from the mesothelial lining of the pleura. Mesothelin (MSLN) is a glycoprotein expressed at low levels in normal tissues and at high levels in MPM. Many other solid cancers overexpress MSLN, and this is associated with worse survival rates. However, this association has not been found in MPM, and the exact biological role of MSLN in MPM requires further exploration. Here, we discuss the current research on the diagnostic and prognostic value of MSLN in MPM patients. Furthermore, MSLN has become an attractive immunotherapy target in MPM, where better treatment strategies are urgently needed. Several MSLN-targeted monoclonal antibodies, antibody–drug conjugates, immunotoxins, cancer vaccines, and cellular therapies have been tested in the clinical setting. The biological rationale underpinning MSLN-targeted immunotherapies and their potential to improve MPM patient outcomes are reviewed.

C1q-HA Matrix Regulates the Local Synthesis of Hyaluronan in Malignant Pleural Mesothelioma by Modulating HAS3 Expression.

Simple SummaryMalignant pleural mesothelioma (MPM) is a rare and aggressive tumor characterized by poor prognosis due to late diagnosis and the absence of efficient first-line treatments. Hyaluronic acid (HA) and the complement protein C1q represent two pivotal players in the MPM tumor microenvironment by acting in association with effects on cancer cell adhesion, migration and proliferation. The aim of the current study is to prove HA production by MPM primary cells and to understand whether HA metabolism modulation could be considered a potential target for future therapeutic approaches in MPM.Increased hyaluronic acid (HA) production is often associated with cancer progression. In malignant pleural mesothelioma (MPM), HA is found at elevated levels in pleural effusions and sera of patients, and it has been widely debated whether MPM cells are able to produce HA by themselves or through the release of growth factors stimulating other cells. Another key component of the MPM microenvironment is C1q, which can act as a pro-tumorigenic factor favoring cell adhesion, migration and proliferation. The aim of the current study was to prove that MPM primary cells are able to synthesize HA and to inquire the stimulus given by C1q–HA matrix to HA synthesis. We confirmed the presence of a HA coat and cable-like structures around MPM primary cells, as well as an intracellular pool, mainly localized in the cytoplasmic and perinuclear region. After evaluating HA synthase (HAS) enzymes’ basal expression in MPM primary cells, we found that C1q bound to HA was able to impinge upon HA homeostasis by upregulating HAS3 both at the mRNA and the protein levels. High expression of HAS3 has been correlated with a shorter life expectancy in MPM by bioinformatical analysis. These data confirmed that C1q bound to HA may exert pro-tumorigenic activity and identified HAS3 as a potential target in MPM.

Identification of CD24 as a potential diagnostic and therapeutic target for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive malignancy of the pleura that is currently incurable due to the lack of an effective early diagnostic method and specific medication. The CDKN2A (p16) and NF2 genes are both frequently mutated in MPM. To understand how these mutations contribute to MPM tumor growth, we generated NF2/p16 double-knockout (DKO) cell clones using human MeT-5A and HOMC-B1 mesothelial cell lines. Cell growth and migration activities were significantly increased in DKO compared with parental cells. cDNA microarray analysis revealed differences in global gene expression profiles between DKO and parental cells. Quantitative PCR and western blot analyses showed upregulation of CD24 concomitant with increased phosphorylation of AKT, p70S6K, and c-Jun in DKO clones. This upregulation was abrogated by exogenous expression of NF2 and p16. CD24 knockdown in DKO cells significantly decreased TGF-β1 expression and increased expression of E-cadherin, an epithelial–mesenchymal transition marker. CD24 was highly expressed in human mesothelioma tissues (28/45 cases, 62%) and associated with the loss of NF2 and p16. Public data analysis revealed a significantly shorter survival time in MPM patients with high CD24 gene expression levels. These results strongly indicate the potential use of CD24 as a prognostic marker as well as a novel diagnostic and therapeutic target for MPM.

UHRF1 Is a Novel Druggable Epigenetic Target in Malignant Pleural Mesothelioma.

Ubiquitin-like with plant homeodomain and ring finger domains 1 (UHRF1) encodes a master regulator of DNA methylation that has emerged as an epigenetic driver in human cancers. To date, no studies have evaluated UHRF1 expression in malignant pleural mesothelioma (MPM). This study was undertaken to explore the therapeutic potential of targeting UHRF1 in MPM. Microarray, real-time quantitative reverse transcription-polymerase chain reaction, immunoblot, and immunohistochemistry techniques were used to evaluate UHRF1 expression in normal mesothelial cells (NMCs) cultured with or without asbestos, MPM lines, normal pleura, and primary MPM specimens. The impact of UHRF1 expression on MPM patient survival was evaluated using two independent databases. RNA-sequencing, proliferation, invasion, and colony formation assays, and murine xenograft experiments were performed to evaluate gene expression and growth of MPM cells after biochemical or pharmacologic inhibition of UHRF1 expression. UHRF1 expression was significantly higher in MPM lines and specimens relative to NMC and normal pleura. Asbestos induced UHRF1 expression in NMC. The overexpression of UHRF1 was associated with decreased overall survival in patients with MPM. UHRF1 knockdown reversed genomewide DNA hypomethylation, and inhibited proliferation, invasion, and clonogenicity of MPM cells, and growth of MPM xenografts. These effects were phenocopied by the repurposed chemotherapeutic agent, mithramycin. Biochemical or pharmacologic up-regulation of p53 significantly reduced UHRF1 expression in MPM cells. RNA-sequencing experiments exhibited the pleiotropic effects of UHRF1 down-regulation and identified novel, clinically relevant biomarkers of UHRF1 expression in MPM. UHRF1 is an epigenetic driver in MPM. These findings support the efforts to target UHRF1 expression or activity for mesothelioma therapy.

Abstract 3954: Validation of the extracellular matrix protein fibulin-3 as a molecular target in malignant pleural mesothelioma

Abstract Malignant pleural mesothelioma (MPM) is a rare and aggressive tumor of the pleura with poor prognosis and limited therapeutic options. Fibulin-3 (gene EFEMP1) is an extracellular matrix protein found in the parenchyma and pleural effusions of MPM, which has been proposed as prognostic biomarker complementing diagnostic biomarkers -such as mesothelin- for this cancer type. However, the functions and potential mechanisms of fibulin-3 in MPM remain completely unknown. To further define the relevance of fibulin-3 in MPM we performed gain- and loss-of-function experiments by respectively overexpressing fibulin-3 in normal mesothelial cells or knocking down its expression in MPM cells, followed by evaluation of cell viability, colony formation, invasion and chemoresistance. We also evaluated changes in gene expression and signaling mechanisms after fibulin-3 downregulation. Furthermore, a novel anti-fibulin-3 antibody was developed and tested for its ability to recognize fibulin-3 in mesothelioma, inhibit pro-tumoral signaling, and disrupt tumor growth in orthotopic MPM models. Fibulin-3 downregulation decreased viability, clonogenic capacity, and invasiveness of MPM cell lines, whereas overexpression of this protein increased the same phenotypic traits in normal mesothelial cells. At the molecular level, fibulin-3 regulated the activation of PI3K/Akt and NFkB signaling and correlated with a gene expression signature required for cell adhesion and motility, matching its cellular effects. Loco-regional delivery of anti-fibulin-3 had a marked cytostatic effect and significantly increased median survival and the number of long-term surviving animals with stable disease. Our work reveals that fibulin-3 is a relevant therapeutic target in mesothelioma, adding to its relevance as prognostic biomarker and encouraging further development of anti-fibulin-3 targeted therapies for this cancer type. Citation Format: Arivazhagan Roshini, Chandra Goparaju, Mohan S. Nandhu, Sharon L. Longo, John A. Longo, Joan Chou, Frank A. Middleton, Harvey I. Pass, Mariano S. Viapiano. Validation of the extracellular matrix protein fibulin-3 as a molecular target in malignant pleural mesothelioma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3954.

Endoplasmic Reticulum Stress Signaling as a Therapeutic Target in Malignant Pleural Mesothelioma.

Malignant pleural mesothelioma (MPM) is a lethal cancer with limited treatment options. No targeted therapy has emerged yet. Here, we performed an integrated molecular characterization of patient tumors in the TCGA dataset, and discovered that endoplasmic reticulum (ER) stress and the adaptive unfolded protein response (UPR) signaling are characteristically deregulated in MPM. Consequently, pharmacological perturbation of ER stress/UPR axis by HA15, an agent that induces persistent proteotoxic stress in the ER, selectively suppresses the viability of MPM cells including those refractory to standard chemotherapy. Mechanically, HA15 augments the already high basal level of ER stress in MPM cells, embarks pro-apoptotic malfunctional UPR and autophagy, which eventually induces cell death in MPM. Importantly, HA15 exerts anti-MPM effectiveness in a mouse model of patient-derived xenografts (PDX) without eliciting overt toxicity when compared to chemotherapy. Our results revealed that programs orchestrating ER stress/UPR signaling represent therapeutic vulnerabilities in MPM and validate HA15 as a promising agent to treat patients with MPM, naïve or resistant to chemotherapy.

P2.04-44 Combined Immune Checkpoint Blockade in Mesothelioma: In Vivo Investigation of in Vitro Data

Malignant pleural mesothelioma (MPM) is an aggressive cancer that is causally associated with asbestos exposure. Due to its aggressive nature and despite the effectiveness of conventional anti-cancer treatment, the prognosis of patients diagnosed with MPM remains dismal, highlighting the urgent need for new therapeutic strategies. Our group and others have recently demonstrated PD-1 and PD-L1 expression in MPM patients, providing rationale to evaluate their suitability as immunotherapeutic targets in MPM. Tree human cell lines representative for the epithelioid and sarcomatoid subtypes of MPM were placed in allogeneic co-cultures with healthy donor peripheral blood mononuclear cells. The co-cultures were treated with the following immune checkpoint blocking antibodies: anti PD-1 (Nivolumab®, BMS) or anti PD-L1 (Durvalumab®, AstraZeneca) in combination with anti TIM-3 or anti LAG-3. Supernatant was collected and enzyme-linked immunosorbent assays and multiplex electrochemo-luminescence were used to look at the secretion of 7 cytokines, being IFNγ, IL-2/5/6/10, IL-1band TNF-α, as well as the enzyme granzyme B. Significant differences were found for the secretion of IFNγ, granzyme B, IL-2, IL-5 and IL-10. Though the differences were not always significant for the 3 MPM cell lines, the same trends were observed among them. Interestingly, highest concentrations of the aforementioned cytokines were all noticed for monotherapy treatment with anti PD-1, anti PD-L1 or or their combination with anti TIM-3. In vivo investigation of PD-1, PD-L1 and TIM-3 blockade, alone or in combination is required for validation of our in vitro results and is currently ongoing. Our data show that treatment with anti PD-1, anti PD-L1 or their respective combination with anti TIM-3 resulted in the highest secretion of cytokines and granzyme B, suggesting that these treatments stimulate the antitumor response the most. Results of our in vivo validation are awaited in order to confirm our in vitro findings.

P2.06-06 Y-box Binding Protein-1, a Potential Target in Malignant Pleural Mesothelioma, Drives Growth Through Distinct Mechanisms

P2.06-06 Y-box Binding Protein-1, a Potential Target in Malignant Pleural Mesothelioma, Drives Growth Through Distinct Mechanisms

Abstract 2136: Doublecortin-like Kinase 1 (DCLK1) correlates with the cell proliferation in malignant pleural mesothelioma

Abstract Background: Malignant pleural mesothelioma (MPM) is a refractory disease with poor prognosis despite multimodality therapy. Because standard therapy is unsatisfactory, it is expected to establish a novel strategy such as molecular-targeting therapy for MPM. Doublecortin-like kinase 1 (DCLK1), a microtubule-associated protein, is one of the tumor-specific stem cell marker and is revealed that the cell survival is reduced by inhibiting this protein in pancreatic and colorectal cancers. DCLK1 is known to have several isoforms named as isoform #1-#4, although the significance of them in MPM has not been clarified. We hypothesized that DCLK1 was a potential therapeutic target for MPM.&amp;lt;Materials and Methods: Immunohistochemical staining was performed using surgically resected formalin-fixed paraffin-embedded tissue of MPM to evaluate the expression of DCLK1. Additionally, MPM cell lines were analyzed to characterize the protein and mRNA expression of DCLK1 by western blotting and RT-PCR. The expression of DCLK1 isoforms were selectively knocked down by small interfering RNA (siRNA) and cell viability was analyzed by colony formation and cell count assays. Results: Immunohistochemical staining demonstrated that the expression of DCLK1 in MPM specimens was positive in 24 out of 27 samples (89%). Western blotting and RT-PCR revealed that DCLK1 was expressed in seven out of nine MPM cell lines. The results of RT-PCR revealed that isoform #2 and isoform #4 of DCLK1 were expressed in H2052, isoform #4 was expressed in H28, and isoform #2 was expressed in YUMC44 cell lines. Expressions of DCLK1 isoforms were selectively suppressed by isoform-specific siRNAs. Colony formation and cell count assays revealed that siRNA-mediated knockdown of both isoforms #2 and #4 suppressed cell growth compared to knockdown by negative control siRNA and knockdown of only isoform #2 or #4. Conclusion: Our results demonstrate that simultaneous knockdown of both isoforms #2 and #4of DCLK1 results in the inhibition of cell growth and suggest its potential as a therapeutic target in MPM. Citation Format: Akihiro Miura, Hiromasa Yamamoto, Hiroyuki Tao, Ken Suzawa, Syunsaku Miyauchi, Kota Araki, Yuta Takahashi, Eisuke Kurihara, Yusuke Ogoshi, Kazuhiko Shien, Junichi Soh, Kazunori Okabe, Shuta Tomida, Masakiyo Sakaguchi, Shinichi Toyooka. Doublecortin-like Kinase 1 (DCLK1) correlates with the cell proliferation in malignant pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2136.

The Investigation of Lipoxygenases as Therapeutic Targets in Malignant Pleural Mesothelioma

Advanced malignant pleural mesothelioma (MPM) has an extremely poor prognosis with limited chemotherapy options, therefore the identification of new therapeutic targets would aid in disease management. Arachidonic acid is metabolised by cyclooxygenase and lipoxygenase enzymes. The lipoxygenase isoenzymes 5-LOX and 12-LOX have been implicated in carcinogenesis. We aimed to examine 5-LOX and 12-LOX protein expression in a large retrospective series of mesothelioma samples. Further to this, the in vitro cytotoxic effects of lipoxygenase pathway inhibitors were investigated in mesothelioma cells. Archival samples from 83 patients with MPM were examined by immunohistochemistry for expression of the 5-LOX and 12-LOX proteins. The MTS assay was used to assess cell viability following 72 h treatment with the lipoxygenase pathway inhibitors baicalein, licofelone, MK-886 and zileuton in the MPM cell lines NCI-H2052, NCI-H2452 and MSTO-211H. Positive 12-LOX protein expression was recorded in 69/83 (83%) and positive 5-LOX expression was observed in 56/77 (73%) of MPM tissue samples. Co-expression of 5-LOX with 12-LOX was seen in 46/78 (58%) of MPM samples. Positive expression of 5-LOX, 12-LOX and COX-2 proteins was identified in the NCI-H2052, NCI-H2452 and MSTO-211H MPM cell lines. Baicalein (12-LOX and 15-LOX inhibitor) was effective in 3/3 MPM cell lines at low concentrations with an IC50 range of 9.6 μM to 20.7 μM. We have demonstrated that the 5-LOX and 12-LOX proteins are expressed in a significant proportion of MPM samples (73% and 83% respectively) and may represent novel therapeutic targets in this disease. We have demonstrated that the inhibition of the LOX pathway using baicalein may be effective as a novel treatment for MPM, however further human pharmacokinetic studies are required in order to establish whether the concentration used in vitro is clinically achievable.

The FAK inhibitor BI 853520 inhibits spheroid formation and orthotopic tumor growth in malignant pleural mesothelioma

No tyrosine kinase inhibitors are approved for malignant pleural mesothelioma (MPM). Preclinical studies identified focal adhesion kinase (FAK) as a target in MPM. Accordingly, we assessed the novel, highly selective FAK inhibitor (BI 853520) in 2D and 3D cultures and in vivo. IC50 values were measured by adherent cell viability assay. Cell migration and 3D growth were quantified by video microscopy and spheroid formation, respectively. Phosphorylation of FAK, Akt, S6, and Erk was measured by immunoblot. The mRNA expression of the putative tumor stem cell markers SOX2, Nanog, CD44, ALDH1, c-myc, and Oct4 was analyzed by qPCR. Cell proliferation, apoptosis, and tumor tissue microvessel density (MVD) were investigated in orthotopic MPM xenografts. In all 12 MPM cell lines, IC50 exceeded 5 μM and loss of NF2 did not correlate with sensitivity. No synergism was found with cisplatin in adherent cells. BI 853520 decreased migration in 3 out of 4 cell lines. FAK phosphorylation was reduced upon treatment but activation of Erk, Akt, or S6 remained unaffected. Nevertheless, BI 853520 inhibited spheroid growth and significantly reduced tumor weight, cell proliferation, and MVD in vivo. BI 853520 has limited effect in adherent cultures but demonstrates potent activity in spheroids and in orthotopic tumors in vivo. Based on our findings, further studies are warranted to explore the clinical utility of BI 853520 in human MPM.Key messagesResponse to FAK inhibition in MPM is independent of NF2 expression or histotype.FAK inhibition strongly interfered with MPM spheroid formation.BI 853520 has been shown to exert anti-tumor effect in MPM.

Aminopeptidase N/CD13 as a potential therapeutic target in malignant pleural mesothelioma.

Angiogenesis is a crucial factor in the progression of malignant pleural mesothelioma (MPM) and antiangiogenic strategies might be effective against MPM. Aminopeptidase N (APN)/CD13 promotes tumour angiogenesis and is associated with poor prognosis; however, its clinical significance in MPM remains unclear.In 37 consecutive patients with surgically resected MPM, we evaluated the association between immunohistochemical APN/CD13 expression in resected tumours and survival. Additionally, the antitumour and antiangiogenic effects of MT95-4, a fully humanised anti-APN/CD13 monoclonal antibody, were evaluated in mice orthotopically implanted with EHMES-10 (abundantly expressing APN/CD13) and MSTO-211H (scarcely expressing APN/CD13) MPM cells.High tumour APN/CD13 expression was associated with poor prognosis in MPM patients (p=0.04), and MT95-4 treatment reduced tumour growth and angiogenesis in mice harbouring EHMES-10 but not MSTO-211H cells. Furthermore, in mice harbouring EHMES-10 cells, MT95-4 combined with cisplatin more effectively suppressed tumour progression than cisplatin alone.Taken together, these results suggest that APN/CD13 is implicated in the aggressiveness of MPM. Here, MT95-4 treatment reduced tumour progression likely by inhibiting angiogenesis, suggesting APN/CD13 as a potential molecular target for MPM treatment. Additionally, combination treatment with MT95-4 and cisplatin could represent a promising approach to treating MPM exhibiting high APN/CD13 expression.

Abstract 30: S100A11 is a prominent therapeutic target in malignant pleural mesothelioma

Abstract [Background &amp; Purpose] Malignant pleural mesothelioma (MPM) is an aggressive tumor arising from the mesothelial cells that show a serious malignancy in thoracic cavity with a median survival time of 9-12 months. The therapeutic approaches in clinical standard are limited to surgery and chemotherapy for early and advanced stages, respectively. The strategies unfortunately provide only palliation, thus further advanced approach is required. S100A11, a Ca2+-binding small protein with two EF-hands, is frequently upregulated in various human cancer tissues. It has been reported that S100A11 plays an important role in progression of many cancers derived from thyroid, ovarian and lung tissues, but its roles and signature in MPM are poorly understood. In this study, we investigated the impact of S100A11 in MPM cell lines and resected tumors. [Material &amp; Methods] We explored the expression of S100A11 in 7 MPM cell lines (HP-1, H28, MSTO-211H, H2052, H290, H2452, and YUMC44) and 2 normal mesothelial cell lines (Met-5A and LP-9). We analyzed the effect of S100A11 on cell proliferation, colony formation, migration, invasion and downstream signaling. The efficacy of anti-S100A11 antibody on cell proliferation and downstream signaling was also determined. [Results] We found that S100A11 protein was consistently upregulated in 7 MPM cell lines at a significant level in comparison to 2 normal mesothelial cells. The same phenomenon was also confirmed in MPM tissue sections by immunohistochemistry, i.e., S100A11 was strongly stained at MPM cells, but not at surrounding normal lung cells. Specific knockdown of S100A11 by small interfering RNA turned the aggressive cells into the attenuated phenotypes for proliferation, invasion and migration. Those were notably observed in both 2 MPM cell lines (H2052 and H2452). Interestingly, we found that MPM cell lines but not normal cells actively secreted the S100A11 protein. To pursue this, we next tried to inhibit the function of the secreted S100A11. Administration of S100A11 neutralizing antibody significantly inhibited the proliferation of 4 MPM cell lines (H2052, H2452, H28, and H290). The antibody had no effect on the proliferation of only one MPM cell line, MSTO-211H, which showed no secretion of S100A11. Taken together, these results suggest that S100A11 secreted from MPM cells can be a prominent target for effective MPM therapy. [Conclusion] Our results suggest that S100A11 is a possible therapeutic target in MPM. Citation Format: Hiroki Sato, Hiromasa Yamamoto, Kei Namba, Hidejiro Torigoe, Takahiro Yoshioka, Kazuhiko Shien, Junichi Soh, Shinichi Toyooka. S100A11 is a prominent therapeutic target in malignant pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 30. doi:10.1158/1538-7445.AM2017-30

Abstract 5191: A combination of Stat3 inhibitor and radiation for the treatment of malignant pleural mesothelioma

Abstract Background: Trimodality therapy, including surgery, is the treatment for patients with malignant pleural mesothelioma (MPM). However, the 5-year survival rate remains less than 40%. To improve the survival rate, we investigated Stat3 as a potential therapeutic target for MPM. Methods:Cell viability was assessed using Cell Counting Kit-8 (CCK-8: WST-8 Dojindo). MPM cells (NCI-H28, NCI-H226, NCI-H2052, NCI-H2452, MSTO-211H) were seeded into 96-well plates. After treatment with a Stat3 inhibitor (BBI-608 : napabucasin), Cell Counting Kit-8 solution was added to each well and absorbance was measured using a microplate reader. The level of phosphorylated Stat3 (p-Stat3) in cell lysates was measured by ELISA. ROS level in cells was measured by FACS analysis. In the in vivo study, H226 cells were injected subcutaneously in the flank region of nude mice randomly assigned to four treatment groups (5 mice/group)—(1) treatment with vehicle control, (2) treatment with Stat3 inhibitor, (3) radiation therapy (RT), and (4) Stat3 inhibitor and RT. Tumor size was measured twice/week. Results: Napabucasin decreased the viability of MPM cells (epithelioid, sarcoma, biphasic) in a dose-dependent manner. p-Stat3 levels decreased by 90% after treatment with 10 μM napabucasin in H226 cells. Napabucasin treatment induced more ROS production in MPM cells than did Pemetrexed. Moreover, combinatorial treatment with napabucasin and radiation (2 Gy, 5 Gy) induced more ROS production than did RT alone. In the mouse model, treatment with napabucasin alone significantly suppressed tumor growth (p &amp;lt; 0.05), but napabucasin and RT completely suppressed tumor growth. Conclusion:We showed that napabucasin inhibited proliferation of the MPM cells (epithelial, biphasic, sarcomatoid) and demonstrated that combination therapy with napabucasin and radiation completely suppressed tumor growth in a mouse model. Treatment with the napabucasin alone and the combination of napabucasin and RT induced high ROS production in MPM cells. Collectively, the combination of Stat3 inhibitor with Radiation Therapy (START) is a promising approach for the treatment of MPM.TheA combination of of Stat3 inhibitor and radiation with for the treatment of malignant pleural mesothelioma Citation Format: Seiji Matsumoto, Hiroshi Doi, Akihiro Fukuda, Tohoru Nakamichi, Ayumi Kuroda, Masaki Hashimoto, Teruhisa Takuwa, Nobuyuki Kondo, Seiki Hasegawa. A combination of Stat3 inhibitor and radiation for the treatment of malignant pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5191. doi:10.1158/1538-7445.AM2017-5191

A phase II trial of dovitinib in previously-treated advanced pleural mesothelioma: The Ontario Clinical Oncology Group

ObjectivesFollowing failure of a platinum-antifolate combination regimen, there is no standard therapy for advanced malignant pleural mesothelioma (MPM). The fibroblast growth factor receptor (FGFR) signaling pathways may be a relevant target in MPM. Dovitinib inhibits multiple tyrosine receptor kinases, predominantly the vascular endothelial growth factor receptors (VEGFR), but also FGFRs, and could be active in MPM. MethodsThis open-label multicentre phase II trial [NCT01769547] enrolled fit, consenting adult patients with advanced MPM who had previously received platinum-antifolate combination chemotherapy and up to one additional line of systemic therapy. Dovitinib was administered orally at 500mg/day for 5days on, 2days off, in 28-day cycles. Response was assessed every 2 cycles using RECIST 1.1 criteria modified for MPM. Correlative studies included FGFR-1 amplification on archival tumour and serum samples for circulating angiogenesis factors. The primary end-point was the proportion of patients progression-free at 3 months (PF3) using a two-stage design. Results12 patients (10 males, median age 67) were enrolled. The median number of cycles administered was 2.5 (range 1–8). One unconfirmed partial response was observed. PF3 was 50% (95% confidence interval 28.4% to 88.0%); although the criterion for proceeding to stage II accrual was met, the trial was halted due to a combination of minimal activity with several early progression events and poor tolerability in this patient population. One of 12 tumour specimens had low amplification of FGFR-1. ConclusionsDovitinib has minimal activity in previously-treated MPM. The role of the FGFR pathway in MPM remains unclear.