Human Malignant Mesothelioma Cell Research Articles

Abstract 1336: Verification of the effect of human allogeneic iPS cell-derived gene-engineered NK cells (eNK cells HLCN061) on mesothelioma

Abstract Malignant pleural mesothelioma is a malignant tumor that is caused by exposure to asbestos. Because it is a rare cancer, there are few drugs that can be used to treat it. Healios is developing iPSC-derived NK cells (eNK cells) (HLCN061) engineered with NKG2D, DAP10, IL-15, CD16, CCL19, and CCR2B genes for the treatment of refractory solid tumors. This study evaluated the antitumor effect of eNK cells against human malignant pleural mesothelioma cell lines.(Method) The antitumor effect of eNK cells on human malignant pleural mesothelioma cell lines in vitro was evaluated using the Viability/Cytotoxicity Multiplex Assay Kit (WST-8/LDH).In vivo, immunodeficient mice were subcutaneously inoculated with human malignant pleural mesothelioma cell lines. After subcutaneous tumor formation, eNK cells were inoculated into or near the tumor, the size of the subcutaneous tumor was measured, and the tumor volume was compared with that of an untreated group. After the study was completed, the tumors were removed and the tumors in the untreated group and the eNK cell-administered group were analyzed using RNA-seq.(Results) The antitumor effect of eNK cells against human malignant pleural mesothelioma cell lines was confirmed in vitro. In a mouse subcutaneous tumor model, the eNK cell treatment group suppressed tumor growth compared to the untreated group (p≦0.05). RNA-seq showed increased expression of granulysin, IL2RB, cathepsin W, etc. in subcutaneous tumors treated with eNK cells. Citation Format: Seiji Matsumoto, Yoshiko Fujita, Kumiko Goto, Yuka Sato, Fusako Nishigaki, Yasuyuki Higashi, Hironobu Kimura, Kouichi Tamura. Verification of the effect of human allogeneic iPS cell-derived gene-engineered NK cells (eNK cells HLCN061) on mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1336.

Effects of microRNA-106b on migration and invasion of human malignant pleural mesothelioma cell NCI-H2452

Objective: To investigate the inhibitory effect of microRNA-106b in the process of migration and invasion of human malignant pleural mesothelioma cell NCI-H2452. Methods: In April 2017, the expression level of miRNA-106b in malignant pleural mesothelioma cells (NCI-H2452, MSTO-211H, NCI-H2052) and normal mesothelial cells MeT-5A was detected and analyzed. Using NCI-H2452 cells as a model, the NCI-H2452 cell model with miRNA-106b overexpression was established by transfecting miRNA-106b mimics. The expression level of miRNA-106b in the cells was detected by real-time fluorescent quantitative PCR. The effect of miRNA-106b on the migration and invasion ability of NCI-H2452 cells was analyzed. The gene expression data of malignant mesothelioma and the downstream target gene data of miRNA-106b in public databases were analyzed to screen the downstream target genes of miRNA-106b in mesothelioma cells that affect cell migration and invasion ability, and to verify the expression of this gene in NCI-H2452 cells with miRNA-106b overexpression. Results: The expression of miRNA-106b in three MPM cells was decreased compared with MeT-5A cells (P<0.001) . The expression level of miRNA-106b was significantly increased after transfection of miRNA-106b mimics (P<0.001) . The scratch migration levels of the experimental group were 28.45%±4.37%, 38.12%±4.82% and 50.06%±8.92% at 24h, 31h and 48h, respectively. Compared with the control group, the migration level decreased by 37.48%±2.65%, 49.21%±3.45% and 68.14%±3.81% (P<0.01) . The number of cell migration and invasion decreased in the experimental group compared with the control group (P<0.001) . Public databases were used to screen and analyze the possibility that TCF21 gene, as a downstream target gene, could affect the migration and invasion ability of MPM cells. The expression level of TCF21 gene was increased after transfection of miRNA-106b mimics in NCI-H2452 cells (P=0.009) . Conclusion: MiRNA-106b can inhibit the migration and invasion of NCI-H2452 cells and increase the expression of TCF21 gene.

Long-Chain Acyl Coenzyme A Dehydrogenase, a Key Player in Metabolic Rewiring/Invasiveness in Experimental Tumors and Human Mesothelioma Cell Lines.

Cross-species investigations of cancer invasiveness are a new approach that has already identified new biomarkers which are potentially useful for improving tumor diagnosis and prognosis in clinical medicine and veterinary science. In this study, we combined proteomic analysis of four experimental rat malignant mesothelioma (MM) tumors with analysis of ten patient-derived cell lines to identify common features associated with mitochondrial proteome rewiring. A comparison of significant abundance changes between invasive and non-invasive rat tumors gave a list of 433 proteins, including 26 proteins reported to be exclusively located in mitochondria. Next, we analyzed the differential expression of genes encoding the mitochondrial proteins of interest in five primary epithelioid and five primary sarcomatoid human MM cell lines; the most impressive increase was observed in the expression of the long-chain acyl coenzyme A dehydrogenase (ACADL). To evaluate the role of this enzyme in migration/invasiveness, two epithelioid and two sarcomatoid human MM cell lines derived from patients with the highest and lowest overall survival were studied. Interestingly, sarcomatoid vs. epithelioid cell lines were characterized by higher migration and fatty oxidation rates, in agreement with ACADL findings. These results suggest that evaluating mitochondrial proteins in MM specimens might identify tumors with higher invasiveness.

Expression of CD24 gene in human malignant pleural mesothelioma and its relationship with prognosis

Objective: To investigate the expression of CD24 gene in human malignant pleural mesothelioma (MPM) cells and tissues, and evaluate its relationship with clinicopathological characteristics and clinical prognosis of MPM patients. Methods: In February 2021, UALCAN database was used to analyze the correlation between CD24 gene expression and clinicopathological characteristics in 87 cases of MPM patients. The TIMER 2.0 platform was used to explore the relationship between the expression of CD24 in MPM and tumor immune infiltrating cells. cBioportal online tool was used to analyze the correlation between CD24 and MPM tumor marker gene expression. RT-qPCR was used to analyze the expressions of CD24 gene in human normal pleural mesothelial cell lines LP9 and MPM cell lines NCI-H28 (epithelial type), NCI-H2052 (sarcoma type), and NCI-H2452 (biphasic mixed type). RT-qPCR was performed to detect the expressions of CD24 gene in 18 cases of MPM tissues and matched normal pleural tissues. The expression difference of CD24 protein in normal mesothelial tissue and MPM tissue was analyzed by immunohistochemistry. A Kaplan-Meier model was constructed to explore the influence of CD24 gene expression on the prognosis of MPM patients, and Cox regression analysis of prognostic factors in MPM patients was performed. Results: The CD24 gene expression without TP53 mutation MPM patients was significantly higher than that of patients in TP53 mutation (P<0.05). The expression of CD24 gene in MPM was positively correlated with B cells (r(s)=0.37, P<0.001). The expression of CD24 gene had a positive correlation with the expressions of thrombospondin 2 (THBS2) (r(s)=0.26, P<0.05), and had a negative correlation with the expression of epidermal growth factor containing fibulin like extracellular matrix protein 1 (EFEMP1), mesothelin (MSLN) and calbindin 2 (CALB2) (r(s)=-0.31, -0.52, -0.43, P<0.05). RT-qPCR showed that the expression level of CD24 gene in MPM cells (NCI-H28, NCI-H2052 and NCI-H2452) was significantly higher than that in normal pleural mesothelial LP9 cells. The expression level of CD24 gene in MPM tissues was significantly higher than that in matched normal pleural tissues (P<0.05). Immunohistochemistry showed that the expressions of CD24 protein in epithelial and sarcoma MPM tissues were higher than those of matched normal pleural tissues. Compared with low expression of CD24 gene, MPM patients with high expression of CD24 gene had lower overall survival (HR=2.100, 95%CI: 1.336-3.424, P<0.05) and disease-free survival (HR=1.800, 95%CI: 1.026-2.625, P<0.05). Cox multivariate analysis showed that compared with the biphasic mixed type, the epithelial type was a protective factor for the prognosis of MPM patients (HR=0.321, 95%CI: 0.172-0.623, P<0.001). Compared with low expression of CD24 gene, high expression of CD24 gene was an independent risk factor for the prognosis of MPM patients (HR=2.412, 95%CI: 1.291-4.492, P=0.006) . Conclusion: CD24 gene and protein are highly expressed in MPM tissues, and the high expression of CD24 gene suggests poor prognosis in MPM patients.

Identification of a derivative of the alkaloid emetine as an inhibitor of the YAP-TEAD interaction and its potential as an anticancer agent.

TEAD is a transcription factor responsible for the output of the tumor suppressor Hippo pathway. The transcriptional activity of TEAD requires molecular interaction with its transcriptional coactivator, YAP. Aberrant activation of TEAD is deeply involved in tumorigenesis and is associated with poor prognosis, suggesting that inhibitors targeting the YAP-TEAD system are promising as antitumor agents. In this study, we identified NPD689, an analog of the natural product alkaloid emetine, as an inhibitor of the YAP-TEAD interaction. NPD689 suppressed the transcriptional activity of TEAD and reduced the viability of human malignant pleural mesothelioma and non-small cell lung cancer cells but not the viability of normal human mesothelial cells. Our results suggest that NPD689 is not only a new useful chemical tool for elucidating the biological role of the YAP-TEAD system but also has potential as a starting compound for developing a cancer therapeutic agent that targets the YAP-TEAD interaction.

Small RNA-Seq Transcriptome Profiling of Mesothelial and Mesothelioma Cell Lines Revealed microRNA Dysregulation after Exposure to Asbestos-like Fibers

Environmental exposure to fibers of respirable size has been identified as a risk for public health. Experimental evidence has revealed that a variety of fibers, including fluoro-edenite, can develop chronic respiratory diseases and elicit carcinogenic effects in humans. Fluoro-edenite (FE) is a silicate mineral first found in Biancavilla (Sicily, Italy) in 1997. Environmental exposure to its fibers has been correlated with a cluster of malignant pleural mesotheliomas. This neoplasm represents a public health problem due to its long latency and to its aggression not alerted by specific symptoms. Having several biomarkers providing us with data on the health state of those exposed to FE fibers or allowing an early diagnosis on malignant pleural mesothelioma, still asymptomatic patients, would be a remarkable goal. To these purposes, we reported the miRNA transcriptome in human normal mesothelial cell line (MeT-5A) and in the human malignant mesothelioma cell line (JU77) exposed and not exposed to FE fibers. The results showed a difference in the number of deregulated miRNAs between tumor and nontumor samples both exposed and not exposed to FE fibers. As a matter of fact, the effect of exposure to FE fibers is more evident in the expression of miRNA in the tumor samples than in the nontumor samples. In the present paper, several pathways involved in the pathogenesis of malignant pleural mesothelioma have been analyzed. We especially noticed the involvement of pathways that have important functions in inflammatory processes, angiogenesis, apoptosis, and necrosis. Besides this amount of data, further studies will be designed for the selection of the most significant miRNAs to test and validate their diagnostic potential, alone or in combination with other protein biomarkers, in high-risk individuals' liquid biopsy to have a noninvasive tool of diagnosis for this neoplasm.

Combined treatment with inhibitors of ErbB Receptors and Hh signaling pathways is more effective than single treatment in reducing the growth of malignant mesothelioma both in vitro and in vivo

Malignant mesothelioma (MM) is a rare orphan aggressive neoplasia with low survival rates. Among the other signaling pathways, ErbB receptors and Hh signaling are deregulated in MM. Thus, molecules involved in these signaling pathways could be used for targeted therapy approaches. The aim of this study was to evaluate the effects of inhibitors of Hh- (GANT-61) and ErbB receptors (Afatinib)-mediated signaling pathways, when used alone or in combination, on growth, cell cycle, cell death and autophagy, modulation of molecules involved in transduction pathways, in three human MM cell lines of different histotypes. The efficacy of the combined treatment was also evaluated in a murine epithelioid MM cell line both in vitro and in vivo. This study demonstrated that combined treatment with two inhibitors counteracting the activation of two different signaling pathways involved in neoplastic transformation and progression, such as those activated by ErbB and Hh signaling, is more effective than the single treatments in reducing MM growth in vitro and in vivo. This study may have clinical implications for the development of targeted therapy approaches for MM.

Dysregulation of microRNAs and tRNA-derived ncRNAs in mesothelial and mesothelioma cell lines after asbestiform fiber exposure

Experimental evidence demonstrated that fluoro-edenite (FE) can develop chronic respiratory diseases and elicit carcinogenic effects. Environmental exposure to FE fibers is correlated with malignant pleural mesothelioma (MPM). An early diagnosis of MPM, and a comprehensive health monitoring of the patients exposed to FE fibers are two clinical issues that may be solved by the identification of specific biomarkers. We reported the microRNA (miRNA) and transfer RNA-derived non coding RNA (tRNA-derived ncRNA) transcriptome in human normal mesothelial and malignant mesothelioma cell lines exposed or not exposed to several concentration FE fibers. Furthermore, an interactive mesothelioma-based network was derived by using NetME tool. In untreated condition, the expression of miRNAs and tRNA-derived ncRNAs in tumor cells was significantly different with respect to non-tumor samples. Moreover, interesting and significant changes were found after the exposure of both cells lines to FE fibers. The network-based pathway analysis showed several signaling and metabolic pathways potentially involved in the pathogenesis of MPM. From papers analyzed by NetME, it is clear that many miRNAs can positively or negatively influence various pathways involved in MPM. For the first time, the analysis of tRNA-derived ncRNAs molecules in the context of mesothelioma has been made by using in vitro systems. Further studies will be designed to test and validate their diagnostic potential in high-risk individuals' liquid biopsies.

A Redox-Silent Analogue of Tocotrienol May Break the Homeostasis of Proteasomes in Human Malignant Mesothelioma Cells by Inhibiting STAT3 and NRF1.

6-O-Carboxypropyl-alpha-tocotrienol (α-T3E) is a multi-target redox-silent analogue of tocotrienol that exhibits cytotoxicity against many cancer cells, including malignant mesothelioma (MM) cells. α-T3E has several molecular targets to effectively induce cytotoxicity against MM cells; however, the mechanisms underlying this cytotoxicity remain unclear. In the present study, we demonstrated that the α-T3E-dependent disruption of the homeostasis of proteasomes strongly induced endoplasmic reticulum (ER) stress, which resulted in effective cytotoxicity against MM cells. The α-T3E-dependent disruption of the homeostasis of proteasomes depended on decreases in proteasome subunits via the inactivation of signal transducer and activator of transcription 3 (STAT3) and nuclear factor erythroid 2 related factor-1 (NRF1), which inhibited protease activity, such as chymotrypsin-like activity, in proteasomes. The α-T3E-dependent inhibition of this activity also induced severe ER stress and ultimately resulted in effective cytotoxicity against MM cells with chemoresistance. The present results indicate that α-T3E acts as an effective anti-mesothelioma agent by disrupting the homeostasis of proteasomes through the simultaneous inactivation of STAT3 and NRF1.

3-Imino derivative-sulfahydantoins: Synthesis, in vitro antibacterial and cytotoxic activities and their DNA interactions

Sulfahydantoins are five-membered rings found in the structure of chemicals that exhibit antibacterial, anti-inflammatory, and anticonvulsant properties. They also activate serine protease enzymes that catalyze the hydrolysis of peptide bonds. Five 3-imino sulfahydantoin compounds were synthesized by using Strecker synthesis reaction with minor modifications. We used reflux of various aldehydes with excess sulfamide in 85% methanol in the presence of sodium cyanide. The spectroscopic properties of these compounds were studied in detail. Antibacterial activities of all synthesized new compounds against four Gram-positive (Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Streptococcus mutans) and four Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella Enteritidis) bacteria were investigated by disc diffusion and microdilution method. pBR322 plasmid DNA binding abilities of compounds were investigated in vitro by agarose gel electrophoresis. In addition, the cytotoxic activities of the compounds against the human malignant pleural mesothelioma (SPC212) cell line were determined by the MTT method. The remarkable result in this study is that the synthesized compounds, especially 4b, 4d, and 4e, have significant biological activities. It has been demonstrated that these compounds, which cause DNA damage, also have an important antibacterial effect on both Gram-negative and Gram-positive bacteria when results compared with the control group antibiotics. Compound 4e exhibited the highest antibacterial potency against Streptococcus mutans (24.33 ± 0.57) from Gram-positive bacteria and Pseudomonas aeruginosa (24.66 ± 1.15) from Gram-negative bacteria. At the same time, MTT results determined that compounds 4b, 4d, and 4e showed cytotoxic activity against the SPC212 cells. In particular, compound 4b had a high cytotoxic effect, and the IC50 value was determined as 6.25 µM.

IL-27 Mediates PD-L1 Expression and Release by Human Mesothelioma Cells.

Simple SummaryMalignant mesothelioma (MM), a rare and aggressive tumor, is related to asbestos exposure, which mediates a chronic inflammatory process involving the cytokine IL-6. Recent studies indicate that the PD-1/PD-L1 immune-suppressive axis is a clinically relevant target for therapy. The expression of PD-L1 in tumor cells is generally a cytokine-mediated effect. Here we show that the IL-6-related cytokine IL-27 is able to enhance PD-L1 expression and soluble (s)PD-L1 release by cultured MM cells, whereas IL-6 is ineffective. In agreement with previous findings, we found high IL-6 levels in pleural exudates from 77 MM patients which correlated with worse survival. More importantly, we also found sPD-L1 and IL-27 in the same samples. sPD-L1 and IL-27 levels showed a moderate albeit significant correlation and association with worse survival, which suggested a potential effect of IL-27 on PD-L1-mediated immune resistance in MM.Malignant mesothelioma (MM) is a rare tumor with an unfavorable prognosis. MM genesis involves asbestos-mediated local inflammation, supported by several cytokines, including IL-6. Recent data showed that targeting PD-1/PD-L1 is an effective therapy in MM. Here, we investigated the effects of IL-6 trans-signaling and the IL-6-related cytokine IL-27 on human MM cells in vitro by Western blot analysis of STAT1/3 phosphorylation. The effects on PD-L1 expression were tested by qRT-PCR and flow-cytometry and the release of soluble (s)PD-L1 by ELISA. We also measured the concentrations of sPD-L1 and, by multiplexed immunoassay, IL-6 and IL-27 in pleural fluids obtained from 77 patients in relation to survival. IL-27 predominantly mediates STAT1 phosphorylation and increases PD-L1 gene and surface protein expression and sPD-L1 release by human MM cells in vitro. IL-6 has limited activity, whereas a sIL-6R/IL-6 chimeric protein mediates trans-signaling predominantly via STAT3 phosphorylation but has no effect on PD-L1 expression and release. IL-6, IL-27, and sPD-L1 are present in pleural fluids and show a negative correlation with overall survival, but only IL-27 shows a moderate albeit significant correlation with sPD-L1 levels. Altogether these data suggest a potential role of IL-27 in PD-L1-driven immune resistance in MM.

Polyphenol Extract from Evening Primrose (Oenothera paradoxa) Inhibits Invasion Properties of Human Malignant Pleural Mesothelioma Cells.

Extracts from the defatted evening primrose (Oenothera paradoxa Hudziok) seeds are the source of a range of stable polyphenolic compounds, including ellagic acid, gallic acid, and catechin. Our studies evaluate, for the first time, the influence of evening primrose isopropanol extract (EPE) on malignant pleural mesothelioma (MPM) cells. MPM is rarely diagnosed, its high aggressiveness and frequently noted chemoresistance limit its treatment schemes and it is characterized by low prognostic features. Here, we demonstrate that EPE inhibited MPM growth in a dose-dependent manner in cells with increased invasion properties. Moreover, EPE treatment resulted in cell cycle arrest in the G2/M phase and increased apoptosis in invasive MPM cell lines. Additionally, EPE strongly limited invasion and MMP-7 secretion in MPM cancer cells. Our original data provide evidence about the potential anti-invasive effects of EPE in MPM therapy treatment.

Cross-Species Proteomics Identifies CAPG and SBP1 as Crucial Invasiveness Biomarkers in Rat and Human Malignant Mesothelioma.

Malignant mesothelioma (MM) still represents a devastating disease that is often detected too late, while the current effect of therapies on patient outcomes remains unsatisfactory. Invasiveness biomarkers may contribute to improving early diagnosis, prognosis, and treatment for patients, a task that could benefit from the development of high-throughput proteomics. To limit potential sources of bias when identifying such biomarkers, we conducted cross-species proteomic analyzes on three different MM sources. Data were collected firstly from two human MM cell lines, secondly from rat MM tumors of increasing invasiveness grown in immunocompetent rats and human MM tumors grown in immunodeficient mice, and thirdly from paraffin-embedded sections of patient MM tumors of the epithelioid and sarcomatoid subtypes. Our investigations identified three major invasiveness biomarkers common to the three tumor sources, CAPG, FABP4, and LAMB2, and an additional set of 25 candidate biomarkers shared by rat and patient tumors. Comparing the data to proteomic analyzes of preneoplastic and neoplastic rat mesothelial cell lines revealed the additional role of SBP1 in the carcinogenic process. These observations could provide new opportunities to identify highly vulnerable MM patients with poor survival outcomes, thereby improving the success of current and future therapeutic strategies.

The phytohormone forchlorfenuron decreases viability and proliferation of malignant mesothelioma cells in vitro and in vivo.

Malignant mesothelioma (MM) is one of the most aggressive cancer types with a patient’s life expectancy of typically less than one year upon diagnosis. The urgency of finding novel therapeutic approaches to treat mesothelioma is evident. Here we tested the effect of the plant-growth regulator forchlorfenuron (FCF), an inhibitor of septin function(s) in mammalian cells, on the viability and proliferation of MM cell lines, as well as other tumor cell lines derived from lung, prostate, colon, ovary, cervix and breast. Exposure to FCF strongly inhibited proliferation of human and mouse (most efficiently epithelioid) MM cells and all other tumor cells in a concentration-dependent manner and led to cell cycle arrest and cell death. The role of septin 7 (SEPT7), a presumably essential target of FCF in MM cells was confirmed by an shRNA strategy. FCF was robustly inhibiting tumor cell growth in vitro at low micromolar (IC50: ≈20-60µM) concentrations and more promisingly also in vivo. Initial experiments with FCF analogous revealed the importance of FCF’s chloride group for efficient cell growth inhibition. FCF’s rather low systemic toxicity might warrant for an extended search for other related and possibly more potent FCF analogues to target MM and putatively other septin-dependent tumors.

A Redox-Inactive Derivative of Tocotrienol Suppresses Tumor Growth of Mesothelioma Cells in a Xenograft Model.

Malignant mesothelioma (MM) is an aggressive cancer with poor prognosis. We focused on the anticancer activity of tocotrienol (T3) and have reported that a new redox-inactive T3 derivative (6-O-carboxypropyl-α-tocotrienol; T3E) exerts stronger inhibitory effects on MM cell growth than that of T3 in vitro. Furthermore, we have revealed some mechanisms of T3E that are involved in anti-MM effects. However, the effect of T3E in vivo remains unclear. In this study, we compared the plasma concentrations of T3E to that of T3 using mice to clarify differences in pharmacokinetics. Blood was sequentially collected after oral administration of T3 or T3E, and plasma concentrations were analyzed by HPLC. The area under the plasma T3 and T3E concentration-time curve from 0 to 24 h (AUC0-24 h) of T3E was two times higher than that of T3. In addition, we evaluated the effect of T3E oral administration on tumor growth using a xenograft model of mice that were transplanted with human MM cells (H2052 cell line). Tumor volume was significantly reduced without body weight loss in mice orally administered 150 mg/kg T3E once per 2 d for 10 d, which suggests that T3E has potential anti-MM effects.

Whole-genome sequencing of human malignant mesothelioma tumours and cell lines.

Pleural mesothelioma is a cancer of serosal surfaces caused by environmental exposure to asbestos. Clinical outcome remains poor and while trials of new treatments are ongoing it remains an understudied cancer. Mesothelioma cell lines can readily be grown from primary tumour and from tumour cells shed into pleural effusion with the latter representing a particularly valuable source of DNA in clinical settings, procurable without the need for additional invasive procedures. However, it is not well understood how accurately patient-derived cultured tumour cells represent the molecular characteristics of their primary tumour. We used whole-genome sequencing of primary tumour and matched cultured cells to comprehensively characterize mutations and structural alterations. Most cases had complex rearranged genomes with evidence of chromoanagenesis and rearrangements reminiscent of chromoplexy. Many of the identified driver mutations were structural, indicating that mesothelioma is often caused by structural alterations and catastrophic genomic events, rather than point mutations. Because the majority of genomic changes detected in tumours were also displayed by the genomes of cultured tumour cells, we conclude that low-passage cultured tumour cells are generally suitable for molecular characterization of mesothelioma and may be particularly useful where tissue samples with high tumour cell content are not available. However, the subclonal compositions of the cell lines did not fully recapitulate the subclonal diversity of the primary tumours. Furthermore, longitudinal acquisition of major alterations in subclonal cell populations was observed after long-term passaging. These two factors define limitations of tumour-derived cell lines as genomic substrate for clinical purposes.

Targeting the C-terminus of galectin-9 induces mesothelioma apoptosis and M2 macrophage depletion

ABSTRACT Galectin-9 has emerged as a promising biological target for cancer immunotherapy due to its role as a regulator of macrophage and T-cell differentiation. In addition, its expression in tumor cells modulates tumor cell adhesion, metastasis, and apoptosis. Malignant mesothelioma (MM) is an aggressive neoplasm of the mesothelial cells lining the pleural and peritoneal cavities, and in this study, we found that both human MM tissues and mouse MM cells express high levels of galectin-9. Using a novel monoclonal antibody (mAb) (Clone P4D2) that binds the C-terminal carbohydrate recognition domain (CRD) of galectin-9, we demonstrate unique agonistic properties resulting in MM cell apoptosis. Furthermore, the P4D2 mAb reduced tumor-associated macrophages differentiation toward a protumor phenotype. Importantly, these effects exerted by the P4D2 mAb were observed in both human and mouse in vitro experiments and not observed with another antigalectin-9 specific mAb (clone P1D9) that engages the N-terminus CRD of galectin-9. In syngeneic murine models of MM, P4D2 mAb treatment inhibited tumor growth and improved survival, with tumors from P4D2-treated mice exhibited reduced infiltration of tumor-associated M2 macrophages. This was consistent with an increased production of inducible nitric oxide synthase, which is a major enzyme-regulating macrophage inflammatory response to cancer. These data suggest that using an antigalectin 9 mAb with agonistic properties similar to those exerted by galectin-9 may provide a novel multitargeted strategy for the treatment of mesothelioma and possibly other galectin-9 expressing tumors.

Glucose starvation induces resistance to metformin through the elevation of mitochondrial multidrug resistance protein 1.

Metformin, a drug for type 2 diabetes mellitus, has shown therapeutic effects for various cancers. However, it had no beneficial effects on the survival rate of human malignant mesothelioma (HMM) patients. The present study was performed to elucidate the underlying mechanism of metformin resistance in HMM cells. Glucose‐starved HMM cells had enhanced resistance to metformin, demonstrated by decreased apoptosis and autophagy and increased cell survival. These cells showed abnormalities in mitochondria, such as decreased ATP synthesis, morphological elongation, altered mitochondrial permeability transition pore and hyperpolarization of mitochondrial membrane potential (MMP). Intriguingly, Mdr1 was significantly upregulated in mitochondria but not in cell membrane. The upregulated mitochondrial Mdr1 was reversed by treatment with carbonyl cyanide m‐chlorophenyl hydrazone, an MMP depolarization inducer. Furthermore, apoptosis and autophagy were increased in multidrug resistance protein 1 knockout HMM cells cultured under glucose starvation with metformin treatment. The data suggest that mitochondrial Mdr1 plays a critical role in the chemoresistance to metformin in HMM cells, which could be a potential target for improving its therapeutic efficacy.

Calretinin promotes invasiveness and EMT in malignant mesothelioma cells involving the activation of the FAK signaling pathway.

Calretinin (CR) is used as a positive marker for human malignant mesothelioma (MM) and is essential for mesothelioma cell growth/survival. Yet, the putative role(s) of CR during MM formation in vivo, binding partners or CR’s influence on specific signaling pathways remain unknown. We assessed the effect of CR overexpression in the human MM cell lines MSTO-211H and SPC111. CR overexpression augmented the migration and invasion of MM cells in vitro. These effects involved the activation of the focal adhesion kinase (FAK) signaling pathway, since levels of total FAK and phospho-FAK (Tyr397) were found up-regulated in these cells. CR was also implicated in controlling epithelial-to-mesenchymal transition (EMT), evidenced by changes of the cell morphology and up-regulation of typical EMT markers. Co-IP experiments revealed FAK as a new binding partner of CR. CR co-localized with FAK at focal adhesion sites; moreover, CR-overexpressing cells displayed enhanced nuclear FAK accumulation and an increased resistance towards the FAK inhibitor VS-6063. Finally, CR downregulation via a lentiviral shRNA against CR (CALB2) resulted in a significantly reduced tumor formation in vivo in an orthotopic xenograft mouse model based on peritoneal MM cell injection. Our results indicate that CR might be considered as a possible target for MM treatment.

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

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