Malignant Pleural Mesothelioma Microenvironment Research Articles

Identification and Characterisation of Infiltrating Immune Cells in Malignant Pleural Mesothelioma Using Spatial Transcriptomics

Increasing evidence strongly supports the key role of the tumour microenvironment in response to systemic therapy, particularly immune checkpoint inhibitors (ICIs). The tumour microenvironment is a complex tapestry of immune cells, some of which can suppress T-cell immunity to negatively impact ICI therapy. The immune component of the tumour microenvironment, although poorly understood, has the potential to reveal novel insights that can impact the efficacy and safety of ICI therapy. Successful identification and validation of these factors using cutting-edge spatial and single-cell technologies may enable the development of broad acting adjunct therapies as well as personalised cancer immunotherapies in the near future. In this paper we describe a protocol built upon Visium (10x Genomics) spatial transcriptomics to map and characterise the tumour-infiltrating immune microenvironment in malignant pleural mesothelioma. Using ImSig tumour-specific immune cell gene signatures and BayesSpace Bayesian statistical methodology, we were able to significantly improve immune cell identification and spatial resolution, respectively, improving our ability to analyse immune cell interactions within the tumour microenvironment.

336P Spatial characterisation of immune microenvironment in malignant pleural mesothelioma

Following the result of Checkmate 743, dual checkpoint inhibition is a standard of care for unresectable malignant pleural mesothelioma (MPM). There is an ongoing need for potential predictive biomarkers for both efficacy and toxicity. To determine how the tumour microenvironment impacts ICI treatment outcomes and irAEs, we have designed a pilot study to determine the role of tumour-infiltrating immune cells on Ipilimumab (IPI) + Nivolumab (NIVO) treatment.

T-cell infiltration in matched samples from malignant pleural mesothelioma (MPM) during evolution of disease.

e20595 Background: MPM is an aggressive cancer associated with asbestos exposure. Chemotherapy has been a mainstay of therapy and recently immunotherapy has been associated with survival improvements. Chemotherapy and immunotherapy influence the tumor microenvironment and some reports have shown increased of TIL after chemotherapy in MPM. The purpose of this study was to determine dynamic changes in the tumor immune environment during mesothelioma evolution and after systemic therapies in paired samples. Methods: We examined 20 matched formalin-fixed paraffin embedded tissue samples from 10 patients (p) with MPM taken at diagnosis and at disease progression (follow-up), including untreated and treated with chemotherapy or immunotherapy. Tissue densities (number of cells/mm2) of key immune effector cells such as total lymphocytes (CD3), cytotoxic T cells (CD8), regulatory T cells (FOXP3) and monocytes/macrophages (CD163) were quantified by image analysis using multiplexed immunohistochemistry (IHC). PD-L1 expression in both tumor cells and immune cells was analysed by singleplex IHC and quantified using the CPS score. Results: Median age was 62 years (range 53-84), 7 p were male and all p presented epithelioid histology. Three matched samples belong to patients that did not receive any systemic treatment between biopsies and the other 7 pair of samples belong to patients treated with chemotherapy +/- immunotherapy. The median interval between paired biopsies was 12 m (3-33 m). Median overall survival was 27.8 months (1 m-NR). Median densities of T cells and macrophages in diagnostic and matched follow-up samples were: CD3+:982 vs 712; CD8+:422 vs 334, FOXP3+: 22 vs 25 and CD163+: 2086 vs 1706. Median PD-L1 CPS was 2.5 and 4 in diagnostic and follow-up samples, respectively. In p receiving treatment between sample pairs, the median densities in diagnostic and follow-up matched samples were: CD3+:979 vs 407; CD8+:467 vs 225, FOXP3+: 25 vs 15, CD163+: 1583 vs 1508, and PD-L1: 2 and 1. In p without any systemic treatment between sample pairs, the median densities were CD3+:1645 vs 2397; CD8+:376 vs 1605, FOXP3+: 19 vs 121, CD163+: 2102 vs 2377, and PD-L1: 3 vs 25. Conclusions: In our small series with paired samples from MPM p, we observed immune cells infiltration changes during MPM evolution with a trend towards a decrease after systemic therapy. Further investigation in tumor microenvironment in MPM to define the most appropriate time for immunotherapy is needed.

Mesothelioma Malignancy and the Microenvironment: Molecular Mechanisms.

Simple SummaryIn the tumor microenvironment, interaction among tumor cells, immune cells, stromal cells, and the extracellular matrix is vital to support pro-tumor mechanisms such as drug resistance and metastases. Malignant pleural mesothelioma has a unique and complex tumor microenvironment. Several reports underlined the key role of immune and stromal cells in tumorigenesis and progression of mesothelioma. These non-cancer cells, via a reciprocal informational exchange with tumor cells, established a chronic inflammatory microenvironment that support the malignancy and the chemoresistant phenotype of the tumor. The knowledge of the cellular and molecular mechanisms underlying tumor microenvironment interconnection was recently considered a crucial point for the design of more effective therapeutic strategies. In this review, we summarize the molecular mechanisms by which stroma and immune cells support the malignancy of mesothelioma and their potential therapeutic targeting.Several studies have reported that cellular and soluble components of the tumor microenvironment (TME) play a key role in cancer-initiation and progression. Considering the relevance and the complexity of TME in cancer biology, recent research has focused on the investigation of the TME content, in terms of players and informational exchange. Understanding the crosstalk between tumor and non-tumor cells is crucial to design more beneficial anti-cancer therapeutic strategies. Malignant pleural mesothelioma (MPM) is a complex and heterogenous tumor mainly caused by asbestos exposure with few treatment options and low life expectancy after standard therapy. MPM leukocyte infiltration is rich in macrophages. Given the failure of macrophages to eliminate asbestos fibers, these immune cells accumulate in pleural cavity leading to the establishment of a unique inflammatory environment and to the malignant transformation of mesothelial cells. In this inflammatory landscape, stromal and immune cells play a driven role to support tumor development and progression via a bidirectional communication with tumor cells. Characterization of the MPM microenvironment (MPM-ME) may be useful to understand the complexity of mesothelioma biology, such as to identify new molecular druggable targets, with the aim to improve the outcome of the disease. In this review, we summarize the known evidence about the MPM-ME network, including its prognostic and therapeutic relevance.

96 The impact of radiographic tumor thickness on the complexity of the tumor immune microenvironment in malignant pleural mesothelioma

BackgroundMalignant pleural mesothelioma (MPM) is a rare and aggressive cancer associated with exposure to asbestos with limited treatment strategies and poor prognosis.1 There is no curative treatment for MPM, and patients follow standard treatment options.2,3 Radiographic tumor thickness (TT) has recently emerged as a surrogate marker associated with overall survival,4 however, the influence of TT on the complexity of the immune component within tumor microenvironment is unknown. Our aim was to perform comprehensive profiling of the tumor immune microenvironment (TIME) relative to the TT to understand of this relationship to guide the design of novel treatment strategies.MethodsTumor specimens (n=29) were obtained from surgically managed MPM patients. Analysis was performed based on the median tumor thickness of 80mm, which defined thick vs thin groups. Additional analysis used TT as a continuous variable for correlations with immune features. The immune cell composition in the TIME was determined by flow cytometry (n=23). Transcriptomic profiling (n=20) was assessed using Nanostring nCounter Tumor Signaling 360 panel. Expanded tumor-infiltrating lymphocytes (TIL) were utilized for further characterization by 10x Genomics single cell RNA-seq profiling (n=8) and cytotoxicity assays (n=18). Level of significance was determined using unpaired non-parametric statistical test.ResultsFresh tumor tissue cytometry showed substantial differences in the immune profiles for thick versus thin tumors, highlighting a relationship of the TT and its immune composition. Thin tumors contained more Tregs, and higher OX40 expression (p=0.081 for non-Treg CD4+ and p<0.05 for CD8+ T cells), CTLA4, LAG3, TIGIT and Ki67 in TIL, while PD-1 expression was not associated with TT. Gene expression profiling suggested an impaired adaptive immune response in thin tumors compared to thick tumors characterized by the exhausted CD8 score (p=0.0252), T-cell co-stimulation score (p=0.0387) and TNF superfamily member score (p=0.0159) and a subset with a myeloid immune evasion score (p=0.0387). TIL expansion was not impacted by baseline TT. However, TIL cytotoxicity, as measured in a redirected lysis assay, showed IFN-gamma response was negatively correlated with baseline TT (p=0.023, R2=0.28). Expanded TIL clustering based upon single cell profiling is underway.ConclusionsUtilizing multi-platform immune profiling approaches, we observed a distinct relationship between the TT and immune signatures. Understanding underlying immune signatures underpinning the biology of thick versus thin MPM tumors provides insights to potential responsiveness to immune-based therapies and may inform on the design for future novel strategies relative to the disease extent based on TT.ReferencesBibby AC, Tsim S, Kanellakis N, Ball H, Talbot DC, Blyth KG, Maskell NA, Psallidas I. Malignant pleural mesothelioma: an update on investigation, diagnosis and treatment. Eur Respir Rev 2016;25(142):472–86.Faig J, Howard S, Levine EA, Casselman G, Hesdorffer M, Ohar JA. Changing pattern in malignant mesothelioma survival. Transl Oncol 2015;8(1):35–9.Alpert N, van Gerwen M, Taioli E. Epidemiology of mesothelioma in the 21st century in Europe and the United States, 40 years after restricted/banned asbestos use. Transl Lung Cancer R 2020;9:S28-S38.de Perrot M, Dong Z, Bradbury P, Patsios D, Keshavjee S, Leighl NB, Hope A, Feld R, Cho J. Impact of tumour thickness on survival after radical radiation and surgery in malignant pleural mesothelioma. Eur Respir J 2017;49(3).Ethics ApprovalThis study was approved by the University of Texas MD Anderson Cancer Center‘s IRB; approval number LAB08-0380; participants gave informed consent before taking part.

OA13.03 Type M1 and Type M2 Macrophages Are Associated With Patient Survival in Malignant Pleural Mesothelioma

Previous studies have demonstrated the prognostic role of the immunological tumor microenvironment in malignant pleural mesothelioma (MPM). Tumor-infiltrating macrophages form the major component of the leucocytes in MPM tumor microenvironment. Macrophages can be divided into two main phenotypes: type M1 macrophages have an anti-tumorigenic function and type M2 macrophages a pro-tumorigenic function promoting tumor development. The macrophage phenotypes affect the biological behavior of MPM and may provide potential therapeutic targets.

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.

Characterization of the immune microenvironment in malignant pleural mesothelioma reveals prognostic subgroups of patients

Malignant pleural mesothelioma (MPM) is a rare tumor with an extremely poor prognosis. Its pathogenesis is related to an immune response against asbestos fibers. The T-lymphocytes, including CD8POS and CD4POS cells, are an important part of the MPM immune microenvironment, and likely contribute to the therapy resistance observed in these tumors. Here, we sought to characterize the MPM-specific lymphocytes subpopulations within the tumor immune microenvironment to identify novel clinically relevant immunologic subtypes of tumors. Representative formalin-fixed, paraffin-embedded (FFPE) tissue blocks of 88 MPMs were included in tissue microarrays and subjected to tumor-infiltrating lymphocytes (TILs) quantification and subtyping by immunohistochemistry (IHC) with antibodies specific for CD4, CD8, and CD19. Further, PD-L1 (clone 22C3) expression was assessed by IHC as a combined positive score (CPS). Our data show that PD-L1 expression by tumor cells or the presence of a sarcomatoid component is related to increased stromal TILs presence in MPM. Survival analyses showed that low CD4POS and high CD8POS stromal TILs are associated with poor patients’ survival. In MPMs with PD-L1 CPS > 1, stromal CD8HIGH was a poor prognostic factor, akin stromal CD4POS peritumoral TILs correlated with a worse prognosis. Furthermore, we demonstrated that a high CD4POS/CD8POS ratio in the tumor immune microenvironment is an independent prognostic factor for survival. Finally, we provided evidence that the characterization of the stromal immune landscape of MPM predicts responses to chemotherapy in subgroups of MPM. The results of this study provide novel insights into the clinical scenario of immune-related biomarkers in MPM.

Tumor-associated macrophage-derived inflammatory cytokine enhances malignant potential of malignant pleural mesothelioma.

Malignant pleural mesothelioma (MPM) is an asbestos‐related aggressive malignant neoplasm. Due to the difficulty of achieving curative surgical resection in most patients with MPM, a combination chemotherapy of cisplatin and pemetrexed has been the only approved regimen proven to improve the prognosis of MPM. However, the median overall survival time is at most 12 mo even with this regimen. There has been therefore a pressing need to develop a novel chemotherapeutic strategy to bring about a better outcome for MPM. We found that expression of interleukin‐1 receptor (IL‐1R) was upregulated in MPM cells compared with normal mesothelial cells. We also investigated the biological significance of the interaction between pro‐inflammatory cytokine IL‐1β and the IL‐1R in MPM cells. Stimulation by IL‐1β promoted MPM cells to form spheroids along with upregulating a cancer stem cell marker CD26. We also identified tumor‐associated macrophages (TAMs) as the major source of IL‐1β in the MPM microenvironment. Both high mobility group box 1 derived from MPM cells and the asbestos‐activated inflammasome in TAMs induced the production of IL‐1β, which resulted in enhancement of the malignant potential of MPM. We further performed immunohistochemical analysis using clinical MPM samples obtained from patients who were treated with the combination of platinum plus pemetrexed, and found that the overexpression of IL‐1R tended to correlate with poor overall survival. In conclusion, the interaction between MPM cells and TAMs through a IL‐1β/IL‐1R signal could be a promising candidate as the target for novel treatment of MPM (Hyogo College of Medicine clinical trial registration number: 2973).

Potential Diagnostic and Prognostic Role of Microenvironment in Malignant Pleural Mesothelioma

IntroductionA comprehensive analysis of the immune cell infiltrate collected from pleural fluid and from biopsy specimens of malignant pleural mesothelioma (MPM) may contribute to understanding the immune-evasion mechanisms related to tumor progression, aiding in differential diagnosis and potential prognostic stratification. Until now such approach has not routinely been verified. MethodsWe enrolled 275 patients with an initial clinical diagnosis of pleural effusion. Specimens of pleural fluids and pleural biopsy samples used for the pathologic diagnosis and the immune phenotype analyses were blindly investigated by multiparametric flow cytometry. The results were analyzed using the Kruskal-Wallis test. The Kaplan-Meier and log-rank tests were used to correlate immune phenotype data with patients’ outcome. ResultsThe cutoffs of intratumor T-regulatory (>1.1%) cells, M2-macrophages (>36%), granulocytic and monocytic myeloid-derived suppressor cells (MDSC; >5.1% and 4.2%, respectively), CD4 molecule–positive (CD4+) programmed death 1–positive (PD-1+) (>5.2%) and CD8+PD-1+ (6.4%) cells, CD4+ lymphocyte activating 3–positive (LAG-3+) (>2.8% ) and CD8+LAG-3+ (>2.8%) cells, CD4+ T cell immunoglobulin and mucin domain 3–positive (TIM-3+) (>2.5%), and CD8+TIM-3+ (>2.6%) cells discriminated MPM from pleuritis with 100% sensitivity and 89% specificity. The presence of intratumor MDSC contributed to the anergy of tumor-infiltrating lymphocytes. The immune phenotype of pleural fluid cells had no prognostic significance. By contrast, the intratumor T-regulatory and MDSC levels significantly correlated with progression-free and overall survival, the PD-1+/LAG-3+/TIM-3+ CD4+ tumor-infiltrating lymphocytes correlated with overall survival. ConclusionsA clear immune signature of pleural fluids and tissues of MPM patients may contribute to better predict patients’ outcome.

Increased sensitivity to apoptosis upon endoplasmic reticulum stress-induced activation of the unfolded protein response in chemotherapy-resistant malignant pleural mesothelioma

BackgroundStandard treatment for advanced malignant pleural mesothelioma (MPM) is a cisplatin/pemetrexed (MTA) regimen; however, this is confronted by drug resistance. Proteotoxic stress in the endoplasmic reticulum (ER) is a hallmark of cancer and some rely on this stress signalling in response to cytotoxic chemotherapeutics. We hypothesise that ER stress and the adaptive unfolded protein response (UPR) play a role in chemotherapy resistance of MPM.MethodsIn vitro three-dimensional (3D) and ex vivo organotypic culture were used to enrich a chemotherapy-resistant population and recapitulate an in vivo MPM microenvironment, respectively. Markers of ER stress, the UPR and apoptosis were assessed at mRNA and protein levels. Cell viability was determined based on acid phosphatase activity.ResultsMPM cells with de novo and/or acquired chemotherapy resistance displayed low ER stress, which rendered the cells hypersensitive to agents that induce ER stress and alter the UPR. Bortezomib, an FDA-approved proteasome inhibitor, selectively impairs chemotherapy-resistant MPM cells by activating the PERK/eIF2α/ATF4-mediated UPR and augmenting apoptosis.ConclusionsWe provide the first evidence for ER stress and the adaptive UPR signalling in chemotherapy resistance of MPM, which suggests that perturbation of the UPR by altering ER stress is a novel strategy to treat chemotherapy-refractory MPM.

Heterogeneous Contributing Factors in MPM Disease Development and Progression: Biological Advances and Clinical Implications.

Malignant pleural mesothelioma (MPM) tumors are remarkably aggressive and most patients only survive for 5–12 months; irrespective of stage; after primary symptoms appear. Compounding matters is that MPM remains unresponsive to conventional standards of care; including radiation and chemotherapy. Currently; instead of relying on molecular signatures and histological typing; MPM treatment options are guided by clinical stage and patient characteristics because the mechanism of carcinogenesis has not been fully elucidated; although about 80% of cases can be linked to asbestos exposure. Several molecular pathways have been implicated in the MPM tumor microenvironment; such as angiogenesis; apoptosis; cell-cycle regulation and several growth factor-related pathways predicted to be amenable to therapeutic intervention. Furthermore, the availability of genomic data has improved our understanding of the pathobiology of MPM. The MPM genomic landscape is dominated by inactivating mutations in several tumor suppressor genes; such as CDKN2A; BAP1 and NF2. Given the complex heterogeneity of the tumor microenvironment in MPM; a better understanding of the interplay between stromal; endothelial and immune cells at the molecular level is required; to chaperone the development of improved personalized therapeutics. Many recent advances at the molecular level have been reported and several exciting new treatment options are under investigation. Here; we review the challenges and the most up-to-date biological advances in MPM pertaining to the molecular pathways implicated; progress at the genomic level; immunological progression of this fatal disease; and its link with developmental cell pathways; with an emphasis on prognostic and therapeutic treatment strategies.

Complement Protein C1q Binds to Hyaluronic Acid in the Malignant Pleural Mesothelioma Microenvironment and Promotes Tumor Growth.

C1q is the first recognition subcomponent of the complement classical pathway, which acts toward the clearance of pathogens and apoptotic cells. C1q is also known to modulate a range of functions of immune and non-immune cells, and has been shown to be involved in placental development and sensorial synaptic pruning. We have recently shown that C1q can promote tumor by encouraging their adhesion, migration, and proliferation in addition to angiogenesis and metastasis. In this study, we have examined the role of human C1q in the microenvironment of malignant pleural mesothelioma (MPM), a rare form of cancer commonly associated with exposure to asbestos. We found that C1q was highly expressed in all MPM histotypes, particularly in epithelioid rather than in sarcomatoid histotype. C1q avidly bound high and low molecular weight hyaluronic acid (HA) via its globular domain. C1q bound to HA was able to induce adhesion and proliferation of mesothelioma cells (MES) via enhancement of ERK1/2, SAPK/JNK, and p38 phosphorylation; however, it did not activate the complement cascade. Consistent with the modular organization of the globular domain, we demonstrated that C1q may bind to HA through ghA module, whereas it may interact with human MES through the ghC. In conclusion, C1q highly expressed in MPM binds to HA and enhances the tumor growth promoting cell adhesion and proliferation. These data can help develop novel diagnostic markers and molecular targets for MPM.

Distribution and function of the complement protein C1q in malignant pleural mesothelioma microenvironment

Malignant pleural mesothelioma (MPM) is an asbestos-related cancer with a median survival of 12 months. The MPM incidence is 1–6/100,000 and is increasing as a result of historic asbestos exposure in industrialized countries and continued use of asbestos in developing countries. Lack of accurate biomarkers makes diagnosis, prognostication and treatment prediction of MPM challenging. The aim of this review is to identify the front line of MPM biomarkers with current or potential clinical impact. Literature search using the PubMed and PLoS One databases, the related-articles function of PubMed and the reference lists of associated publications until April 26th 2015 revealed a plethora of candidate biomarkers. The current gold standard of MPM diagnosis is a combination of two positive and two negative immunohistochemical markers in the epithelioid and biphasic type, but sarcomatous type do not have specific markers, making diagnosis more difficult. Mesothelin in serum and pleural fluid may serve as adjuvant diagnostic with high specificity but low sensitivity. Circulating proteomic and microRNA signatures, fibulin-3, tumor cell gene-ratio test, transcriptomic, lncRNA, glycopeptides, pleural fluid FISH assay, hyaluronate/N-ERC mesothelin and deformability cytometry may be important future markers. Putative predictive markers for pemetrexed–platinum are tumor TS and TYMS, for vinorelbine the ERCC1, beta-tubuline class III and BRCA1. Mutations of the BAP1 gene are potential markers of MPM susceptibility. In conclusion, the current status of MPM biomarkers is not satisfactory but encouraging as more sensitive and specific non-invasive markers are emerging. However, prospective validation is needed before clinical application.

Integrated analysis of somatic mutations and immune microenvironment in malignant pleural mesothelioma

ABSTRACTTo investigate the link between the genomic landscape of cancer cells and immune microenvironment in tumor tissues, we characterized somatic mutations and tumor-infiltrating lymphocytes (TILs) in malignant pleural mesothelioma (MPM), including mutation/neoantigen load, spatial heterogeneity of somatic mutations of cancer cells and TILs (T-cell receptor β (TCRβ) repertoire), and expression profiles of immune-related genes using specimens of three different tumor sites (anterior, posterior, and diaphragm) obtained from six MPM patients. Integrated analysis identified the distinct patterns of somatic mutations and the immune microenvironment signatures both intratumorally and interindividually. MPM cases showed intratumoral heterogeneity in somatic mutations with unique TCRβ clonotypes of TILs that were restricted to each tumor site, suggesting the presence of a neoantigen-related immune response. Correlation analyses showed that higher neoantigen load was significantly correlated with stronger clonal expansion of TILs (p = 0.048) and a higher expression level of an immune-associated cytolytic factor (PRF1 (p = 0.0041) in tumor tissues), suggesting that high neoantigen loads in tumor cells might promote expansion of functional tumor-specific T cells in the tumor bed. Our results collectively indicate that MPM tumors constitute a diverse heterogeneity in both the genomic landscape and immune microenvironment, and that mutation/neoantigen load may affect the immune microenvironment in MPM tissues.

OA13.05 Somatic Genetic Alterations and Immune Microenvironment in Malignant Pleural Mesothelioma

The genomic landscape of malignant pleural mesothelioma (MPM) is not well understood. Advanced high-throughput sequencing technologies allow comprehensive characterization of genetic alterations. Knowledge of the somatic mutations and the immune microenvironment in patients with MPM will help to develop effective targeted therapies. We examined biopsy specimens from 12 MPM patients (8 epithelioid and 4 biphasic) that were removed during maximal cyto-reductive surgery. Specimens from 3 different sites (anterior, posterior and diaphragm, a total of 36 tissue samples) were studied through whole exome sequencing, T cell receptor (TCR) repertoire analysis of tumor-infiltrating T cells (TILs), and expression levels of immune-related genes. We also performed in silico prediction of potent neoantigens derived from non-synonymous somatic mutations in each specimen. For the comparison of tumor tissues from 3 different sites, we performed hierarchical clustering to assess the tumor heterogeneity and differences in immune environment. High mutation/neoantigen load was significantly correlated with higher clonal expansion of TILs (R=0.46) and high expression levels of immune-associated cytolytic factors, granzyme A (R=0.25) and perforin 1 (R=0.48), in tumor tissues. In the clustering analysis, heterogeneous MPM cases revealed unique neoantigens and clonotypes of TILs that were restricted to each of tumor site, suggesting infiltration of the neoantigen-specific T cells. Further sub-analysis according to histologic types showed that biphasic tumors had higher mutation/neoantigen load and stronger oligo-clonal T cell expansion (p=0.01) than epithelioid tumors. Our analysis demonstrated a significant correlation between somatic mutation/neoantigen load, clonality of TILs, and the immune-related tumor microenvironment in MPM. Our findings suggest that high mutation/neoantigen load in tumor cells might promote effective expansion and infiltration of functional (tumorocidal) T cells into the tumor bed. These findings provide a rationale for selecting MPM patients who can benefit from treatment with immune checkpoint blockades. This may accelerate development of the neoantigen targeting TCR-engineered T cell therapy for MPM.

Integrated analysis of somatic genetic alterations and immune microenvironment in malignant pleural mesothelioma.

e20080Background: Malignant pleural mesothelioma (MPM) is a rare, aggressive tumor and rapidly fatal when untreated. Advanced high-throughput sequencing technologies allow comprehensive characteriz...

The tumoral and stromal immune microenvironment in malignant pleural mesothelioma: A comprehensive analysis reveals prognostic immune markers

Antitumor immune responses against solid malignancies correlate with improved patient survival. We conducted a comprehensive investigation of immune responses in tumor and tumor-associated stroma in epithelioid malignant pleural mesothelioma with the goal of characterizing the tumor immune microenvironment and identifying prognostic immune markers. We investigated 8 types of tumor-infiltrating immune cells within the tumor nest and tumor-associated stroma, as well as tumor expression of 5 cytokine/chemokine receptors in 230 patients. According to univariate analyses, high densities of tumoral CD4- and CD20-expressing lymphocytes were associated with better outcomes. High expression of tumor interleukin-7 (IL-7) receptor was associated with worse outcomes. According to multivariate analyses, stage and tumoral CD20 detection were independently associated with survival. Analysis of single immune cell infiltration for CD163+ tumor-associated macrophages did not correlate with survival. However, analysis of immunologically relevant cell combinations identified that: (1) high CD163+ tumor-associated macrophages and low CD8+ lymphocyte infiltration had worse prognosis than other groups and (2) low CD163+ tumor associated macrophages and high CD20+ lymphocyte infiltration had better prognosis than other groups. Multivariate analyses demonstrated that CD163/CD8 and CD163/CD20 were independent prognostic factors of survival. With a recent increase in immunotherapy investigations and clinical trials for malignant pleural mesothelioma patients, our observations that CD20+ B lymphocytes and tumor-associated macrophages are prognostic markers provide important information about the tumor microenvironment of malignant pleural mesothelioma.

Cisplatin in combination with Phenethyl Isothiocyanate (PEITC), a potential new therapeutic strategy for malignant pleural mesothelioma.

Malignant pleural mesothelioma (MPM) is a very aggressive form of cancer with a poor diagnosis and prognosis. The first line treatment for MPM is a combination of cisplatin and Pemetrexed, which displayed limited efficacy and severe side effects. The naturally occurring compound phenethyl isothiocyanate (PEITC) previously showed interesting anti-tumor properties on several cancer cell lines. We thus aim at evaluating PEITC used alone or in combination with cisplatin in order to improve MPM treatment. Nine MPM cell lines and primary mesothelial cells (PMC), co-cultured or not with M2 macrophages present in MPM microenvironment, were used to assess PEITC and cisplatin anti-tumor properties. Compounds were used alone or in combination. Both PEITC and cisplatin were cytotoxic on MPM cells in a dose dependent manner. We herein showed that PEITC-induced cytotoxicity was due to the generation of reactive oxygen species. Moreover, we showed that cisplatin-PEITC combination allowed the potentialization of both compounds' cytotoxic effects and prevented the emergence of resistant MPM cells. Interestingly, PMC were not sensitive to the combination. Finally, we showed that M2 macrophages did not alter the anti-tumor properties of the combination. Cisplatin-PEITC combination thus represents a promising strategy to induce a selective toxicity towards malignant cells.

Multimodality treatment of malignant pleural mesothelioma with or without immunotherapy: does it change anything?☆

The purpose of this study was to investigate immunological effector cells and angiogenesis in malignant pleural mesothelioma (MPM) patients, who underwent multimodality treatments. Clinical and pathological characteristics of 57 patients, with International Mesothelioma Interest Group stage II-III MPM, who underwent two different multimodality treatments (with and without immunotherapy) between 1999 and 2008 were analyzed. CD8+, CD4+ and Foxp3+ tumor-infiltrating lymphocytes, tryptase and chymase mast cells (MCs), CD34, number of microvessels and vascular endothelial growth factor were determined by immunohistochemistry. The histology was 51 epitheliomorf and 6 biphasic. The stage was III in 41 cases and II in 16 cases. With an average follow-up of 69 months (range 9-115) 14 patients are still alive and the overall median actuarial survival is 21.4 months. Tryptase MCs, CD8+ and Foxp3+ lymphocytes had significantly increased in the interleukin 2 (IL-2) treated group. Moreover, the number of microvessels was significantly lower in IL-2 treated patients. This study indicates that immunotherapy leads to an increase in cytotoxic CD8+ lymphocytes and tryptase MCs and to a decrease of the tumoral neoangiogenesis. Changes in MPM microenvironment induced by immunotherapy may play a major role in the local control of this disease and need further investigations.