HDAC Inhibition with Valproate Improves Direct Cytotoxicity of Monocytes against Mesothelioma Tumor Cells

peer reviewedThe composition of the tumor microenvironment (TME) mediates the outcome of chemo- and immunotherapies in malignant pleural mesothelioma (MPM). Tumor-associated macrophages (TAMs) and monocyte myeloid-derived immunosuppressive cells (M-MDSCs) constitute a major fraction of the TME. As central cells of the innate immune system, monocytes exert well-characterized functions of phagocytosis, cytokine production, and antibody-dependent cell-mediated cytotoxicity (ADCC). The objective of this study was to evaluate the ability of monocytes to exert a direct cytotoxicity by cell-to-cell contact with MPM cells. The experimental model is based on cocultures between human blood-derived monocytes sorted by negative selection and mesothelioma cell lines. Data show (i) that blood-derived human monocytes induce tumor cell death by direct cell-to-cell contact, (ii) that VPA is a pharmacological enhancer of this cytotoxic activity, (iii) that VPA increases monocyte migration and their aggregation with MPM cells, and (iv) that the molecular mechanisms behind VPA modulation of monocytes involve a downregulation of the membrane receptors associated with the M2 phenotype, i.e., CD163, CD206, and CD209. These conclusions, thus, broaden our understanding about the molecular mechanisms involved in immunosurveillance of the tumor microenvironment and open new prospects for further improvement of still unsatisfactory MPM therapies

Contribution of lysine deacetylases to the therapy of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare cancer arising from mesothelial cells from the pleura. The first line chemotherapy of the epithelioid subtype of MPM is based on a combined regimen of cisplatin and an antifolate (pemetrexed). Recently, immunotherapy with two checkpoint inhibitors (PD-1, nivolumab and CTLA-4, ipilimumab) showed promising results for the sarcomatoid subtype. Despite this major breakthrough, the median overall survival of patients only reached 18.1 months, compared to 14 months in standard chemotherapy. With an objective response rate of 40%, only a subset of patients benefits from immunotherapy. Therefore, options for second line treatment are still mandatory. We previously proposed a therapy based on the combination of a topoisomerase inhibitor (doxorubicin) and a lysine deacetylase inhibitor (valproate, VPA) (Scherpereel et al, European Respiratory Journal 37:129-135). We identified one of the key determinants that modulates the chemoresistance (Staumont et al, Cancers 12:1484). In this study, we aimed to further investigate the mechanisms involved by analyzing the effect of VPA on the tumor microenvironment and more particularly on the interactions between monocytes and tumor cells. We showed that VPA affects the viability of doxorubicin-treated mesothelioma cells and promotes their apoptosis. The use of caspase and calpeptin inhibitors demonstrated that apoptosis occurs through a caspase-dependent mechanism involving both intrinsic and extrinsic pathway. Western blot analysis revealed that the combination of VPA and doxorubicin increases the expression of clived-Bid, Bax and cytochrome c while decreasing the expression of Bcl-2 and Bcl-XL. Transcriptomic analysis unveiled that epithelioid mesothelioma cells express more p21, Fas, Bbc3 and TP53INP1 upon treatment compared to the sarcomatoid subtype. To investigate the role of the microenvironment, we designed two models to study the influence of tumor-associated monocytes. Mesothelioma cells were co-cultured with THP-1 monocytes differentiated in presence of PMA. Flow cytometry, confocal microscopy and live imaging demonstrated that THP-1-derived monocytes are able to interact and kill tumor cells. Furthermore, VPA promotes the interaction between monocytes and tumor cells and fosters the cytotoxic activity of monocytes. In contrast to PMA, VPA does not affect the motility of THP-1 monocytes. These observations were validated and extended to primary monocytes isolated from peripheral blood. Increased cytotoxicity of primary monocytes is correlated with a reduced frequency of CD16+ cells. In this model, VPA augments the average speed of primary monocytes. Finally, RNA sequencing highlighted the key mechanisms involved in monocyte antitumor activity. In conclusion, we demonstrate that VPA directly affects the survival of tumor cells and indirectly modulates the cytotoxic activity of monocytes in the microenvironment

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In silico assessment data of allergenicity and cross-reactivity of NP24 epitopes from Solanum lycopersicum (Tomato) fruit

This paper describes data on allergies caused by food (vegetable) and their negative impact on the nutritional balance of the human body. Allergic responses to vegetables such as tomatoes, capsicum and spinach are next to fish, eggs and nuts. Epitopes such as NP24 (allergens) are one of the salt-induced allergenic proteins found in the thaumatin-like protein (TLP) family. The mechanism of allergenicity of TLP found in Solanum lycopersicum (Tomato) fruit is poorly studied. Here we demonstrated allergenicity conferred by the NP24 protein found in Tomato. The data on the cross-reactivity of NP24 protein was generated using Allergen Online and Allermatch tools. Tomato allergenic protein epitope shows a significant identity of with allergens reported in Capsicum, Olive, Kiwi, Tobacco and Banana allergens. Hence, the datasets of sequences, comparative analysis and homology epitope mapping over three dimensional (3D) structures revealed that NP24 has higher cross-reactivity to Capsicum and Tobacco proteins. Thus, this data probably act as limelight for planning wet lab experiments. Keywords: NP24 protein, Epitope mapping, Fruit and vegetable allergies, Oral allergy syndrome, IgE antibod

Activation of DNA Damage Tolerance Pathways May Improve Immunotherapy of Mesothelioma

Immunotherapy based on two checkpoint inhibitors (ICI), programmed cell death 1 (PD-1, Nivolumab) and cytotoxic T-lymphocyte 4 (CTLA-4, Ipilimumab), has provided a significant improvement in overall survival for malignant mesothelioma (MM). Despite this major breakthrough, the median overall survival of patients treated with the two ICIs only reached 18.1 months vs. 14 months in standard chemotherapy. With an objective response rate of 40%, only a subset of patients benefits from immunotherapy. A critical step in the success of immunotherapy is the presentation of tumor-derived peptides by the major histocompatibility complex I (MHC-I) of tumor cells. These neoantigens are potentially immunogenic and trigger immune responses orchestrated by cytotoxic cells. In MM, tumor development is nevertheless characterized by a low mutation rate despite major structural chromosomal rearrangements driving oncogenesis (BAP1, NF2, CDKN2AB). In this opinion, we propose to investigate an approach based on the mechanisms of the DNA damage tolerance (DDT) pathways to increase the frequency of non-synonymous mutations. The idea is to transiently activate the error-prone DDT in order to generate neoantigens while preserving a fully competent antitumor immune response

TGFα Promotes Chemoresistance of Malignant Pleural Mesothelioma

Background: There is no standard chemotherapy for refractory or relapsing malignant pleural mesothelioma (MPM). Our previous reports nevertheless indicated that a combination of an anthracycline (doxorubicin) and a lysine deacetylase inhibitor (valproic acid, VPA) synergize to induce the apoptosis of MPM cells and reduce tumor growth in mouse models. A Phase I/II clinical trial indicated that this regimen is a promising therapeutic option for a proportion of MPM patients. Methods: The transcriptomes of mesothelioma cells were compared after Illumina HiSeq 4000 sequencing. The expression of differentially expressed genes was inhibited by RNA interference. Apoptosis was determined by cell cycle analysis and Annexin V/7-AAD labeling. Protein expression was assessed by immunoblotting. Preclinical efficacy was evaluated in BALB/c and NOD-SCID mice. Results: To understand the mechanisms involved in chemoresistance, the transcriptomes of two MPM cell lines displaying different responses to VPA-doxorubicin were compared. Among the differentially expressed genes, transforming growth factor alpha (TGFα) was associated with resistance to this regimen. The silencing of TGFα by RNA interference correlated with a significant increase in apoptosis, whereas the overexpression of TGFα desensitized MPM cells to the apoptosis induced by VPA and doxorubicin. The multi-targeted inhibition of histone deacetylase (HDAC), HER2 and TGFα receptor (epidermal growth factor receptor/EGFR) improved treatment efficacy in vitro and reduced tumor growth in two MPM mouse models. Finally, TGFα expression but not EGFR correlated with patient survival. Conclusions: Our data show that TGFα but not its receptor EGFR is a key factor in resistance to MPM chemotherapy. This observation may contribute to casting light on the promising but still controversial role of EGFR signaling in MPM therapy

Image_3_Excess of blood eosinophils prior to therapy correlates with worse prognosis in mesothelioma.tiff

BackgroundOnly a fraction of patients with malignant pleural mesothelioma (MPM) will respond to chemo- or immunotherapy. For the majority, the condition will irremediably relapse after 13 to 18 months. In this study, we hypothesized that patients’ outcome could be correlated to their immune cell profile. Focus was given to peripheral blood eosinophils that, paradoxically, can both promote or inhibit tumor growth depending on the cancer type.MethodsThe characteristics of 242 patients with histologically proven MPM were retrospectively collected in three centers. Characteristics included overall survival (OS), progression-free survival (PFS), overall response rate (ORR) and disease control rate (DCR). The mean absolute eosinophil counts (AEC) were determined by averaging AEC data sets of the last month preceding the administration of chemo- or immunotherapy.ResultsAn optimal cutoff of 220 eosinophils/µL of blood segregated the cohort into two groups with significantly different median OS after chemotherapy (14 and 29 months above and below the threshold, p = 0.0001). The corresponding two-year OS rates were 28% and 55% in the AEC ≥ 220/µL and AEC ConclusionIn conclusion, baseline AEC ≥ 220/µL preceding therapy is associated with worse outcome and quicker relapse in MPM.</p

Table_1_Excess of blood eosinophils prior to therapy correlates with worse prognosis in mesothelioma.pdf

BackgroundOnly a fraction of patients with malignant pleural mesothelioma (MPM) will respond to chemo- or immunotherapy. For the majority, the condition will irremediably relapse after 13 to 18 months. In this study, we hypothesized that patients’ outcome could be correlated to their immune cell profile. Focus was given to peripheral blood eosinophils that, paradoxically, can both promote or inhibit tumor growth depending on the cancer type.MethodsThe characteristics of 242 patients with histologically proven MPM were retrospectively collected in three centers. Characteristics included overall survival (OS), progression-free survival (PFS), overall response rate (ORR) and disease control rate (DCR). The mean absolute eosinophil counts (AEC) were determined by averaging AEC data sets of the last month preceding the administration of chemo- or immunotherapy.ResultsAn optimal cutoff of 220 eosinophils/µL of blood segregated the cohort into two groups with significantly different median OS after chemotherapy (14 and 29 months above and below the threshold, p = 0.0001). The corresponding two-year OS rates were 28% and 55% in the AEC ≥ 220/µL and AEC ConclusionIn conclusion, baseline AEC ≥ 220/µL preceding therapy is associated with worse outcome and quicker relapse in MPM.</p