Malignant pleural mesothelioma (MPM) is a devastating malignancy with limited therapeutic options. Fibroblast growth factor receptors (FGFR) and their ligands were shown to contribute to MPM aggressiveness and it was suggested that subgroups of MPM patients could benefit from FGFR-targeted inhibitors. In the current investigation, we determined the expression of all four FGFRs (FGFR1–FGFR4) by immunohistochemistry in tissue samples from 94 MPM patients. From 13 of these patients, we were able to establish stable cell lines, which were subjected to FGFR1–4 staining, transcript analysis by quantitative RT-PCR, and treatment with the FGFR inhibitor infigratinib. While FGFR1 and FGFR2 were widely expressed in MPM tissue and cell lines, FGFR3 and FGFR4 showed more restricted expression. FGFR1 and FGFR2 showed no correlation with clinicopathologic data or patient survival, but presence of FGFR3 in 42% and of FGFR4 in 7% of patients correlated with shorter overall survival. Immunostaining in cell lines was more homogenous than in the corresponding tissue samples. Neither transcript nor protein expression of FGFR1–4 correlated with response to infigratinib treatment in MPM cell lines. We conclude that FGFR3 and FGFR4, but not FGFR1 or FGFR2, have prognostic significance in MPM and that FGFR expression is not sufficient to predict FGFR inhibitor response in MPM cell lines.

Solitary fibrous tumor of the pleura (SFT) is a rare disease. Besides surgery combined with radiotherapy in nondisseminated stages, curative options are currently absent. Out of fourteen primo-cell cultures, established from surgical SFT specimens, two showed stable in vitro growth. Both cell models harbored the characteristic NAB2-STAT6 fusion and were further investigated by different preclinical methods assessing cell viability, clone formation, and protein regulation upon single-drug treatment or in response to selected treatment combinations. Both fusion-positive cell models showed—in line with the clinical experience and the literature—a low to moderate response to most of the tested cytotoxic and targeted agents. However, the multi-tyrosine kinase inhibitors ponatinib and dasatinib, as well as the anti-sarcoma compound trabectedin, revealed promising activity against SFT growth. Furthermore, both cell models spontaneously presented strong FGFR downstream signaling targetable by ponatinib. Most interestingly, the combination of either ponatinib or dasatinib with trabectedin showed synergistic effects. In conclusion, this study identified novel trabectedin-based treatment combinations with clinically approved tyrosine kinase inhibitors, using two newly established NAB2-STAT6 fusion-positive cell models. These findings can be the basis for anti-SFT drug repurposing approaches in this rare and therapy-refractory disease.

Reactive oxygen species (ROS)-induced aberrant oncogenic signalling has been proposed to mediate the progression and development of pleural mesothelioma (PM). In this study, we demonstrate how ROS promote oncogenic signalling, especially in the context of cell migration and immune evasion via YB-1 phosphorylation in mesothelial and PM cell models. Xanthine (X)- and xanthine oxidase (XO)-generated ROS exposure led to increased migration and a more elongated cell shape in mesothelial and PM cells in live-cell videomicroscopy analyses. These effects were associated with the enhanced phosphorylation of ERK, AKT, and YB-1 and the elevated gene expression of PD-L1 and PD-L2, which were analysed with immunoblotting and quantitative real-time RT-PCR, respectively. The pharmacological inhibition of AKT (ipatasertib), MEK (trametinib), and RSK (BI-D1870) resulted in the reversal of ROS-induced effects, with the strongest effects observed upon the inhibition of YB-1 phosphorylation by BI-D1870. The results suggest that ROS exposure has a strong impact on cell migration and immune evasion not only in PM cells but also in mesothelial cells, from which PM arises. Interfering with ROS-responsive kinase pathways, particularly YB-1 phosphorylation, could counteract pro-migratory and immune-evasive effects in PM.

Reactive oxygen species (ROS)-induced aberrant oncogenic signaling has been proposed to mediate the progression and development of pleural mesothelioma (PM). Here we demonstrate how ROS initiates oncogenic signaling especially in the context of cell migration and immune evasion via YB-1 phosphorylation in mesothelial and PM cell models. Xanthine (X) and xanthine oxidase (XO)-generated ROS exposure led to increased migration and more elongated cell shape in mesothelial and PM cells in live cell videomicroscopy analyses. These effects were associated with enhanced phosphorylation of ERK, AKT and YB-1, alongside elevated gene expression of PD-L1 and PD-L2, which were analysed with immunoblotting and quantitative real-time RT-PCR, respectively. Pharmacological inhibition of AKT (ipatasertib), MEK (trametinib) or RSK (BI-D1870) resulted in reversal of ROS-induced effects, with the strongest effects observed upon inhibition of YB-1 phosphorylation by BI-D1870. The results suggest that ROS exposure has a strong impact on cell migration and immune evasion not only in PM cells but also in mesothelial cells, from which PM arises. Interfering with ROS responsive kinase pathways, particularly YB-1 phosphorylation, could counteract pro-migratory and immune evasive effects in PM.

Background/Objectives: Malignant pleural mesothelioma (MPM) remains challenging to treat, with a poor prognosis. As controversy about clinical management continues, predictive biomarkers for patient selection to indicate the benefit of treatment modalities are urgently needed. Methods: In a retrospective analysis of 195 patients between 1994 and 2020 at the Department of Thoracic Surgery, Medical University of Vienna, Austria, the Mesothelioma Systemic Inflammation Score (MSIS)—consisting of pretreatment neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), C-reactive protein (CRP), and fibrinogen—was tested for its prognostic and predictive significance. The prognostic impact of MSIS was subsequently validated in an independent cohort of 80 patients treated at the Department of Thoracic Surgery, Karl Landsteiner Institute for Clinical and Translational Thoracic Surgery Research, Clinic Floridsdorf, Vienna, Austria. Results: Median overall survival (OS) was 14 months for the entire cohort (95% CI: 11.4–16.6). Patients undergoing multimodality treatment including macroscopic complete resection had a longer OS (22.3 months, 95% CI: 18.6–26.0; p < 0.001). In multivariable analysis, MSIS (p < 0.001), disease stage (p = 0.001), and the type of treatment (p = 0.004) were confirmed as independent predictors for OS. Higher MSIS was associated with shorter OS (p < 0.001). Significant survival benefit of multimodality regimens including surgery was limited to patients with low MSIS. Among patients with low (≤ 2) MSIS, multimodality therapy was associated with significantly prolonged OS when compared with chemo- and/or radiotherapy alone (25.8 months [95% CI: 16.4–35.3] vs. 14.4 months [95% CI: 10.4–18.4], p < 0.001). In contrast, among patients with elevated MSIS, no survival benefit was achieved by surgery over conservative treatment (11.8 months [95% CI: 8.3–15.3] vs. 8.2 months [95% CI: 5.2–11.3], p = 0.233). The ability of MSIS to predict survival was equivalent between the baseline and the independent validation cohort (p < 0.001). Conclusions: The Mesothelioma Systemic Inflammation Score was found to be an independent prognostic score in pleural mesothelioma, predicting benefit from macroscopic complete resection as part of multimodality treatment in distinct patients.