Basic fibroblast growth factor in mesothelioma pleural effusions: correlation with patient survival and angiogenesis

Circulating FGF18 is decreased in pleural mesothelioma but not correlated with disease prognosis

BACKGROUND

Pleural mesothelioma (PM) is a relatively rare malignancy with limited treatment options and dismal prognosis. We have previously found elevated FGF18 expression in PM tissue specimens compared with normal mesothelium. The objective of the current study was to further explore the role of FGF18 in PM and evaluate its suitability as a circulating biomarker.

METHODS

FGF18 mRNA expression was analyzed by real-time PCR in cell lines and in silico in datasets from the Cancer Genome Atlas (TCGA). Cell lines overexpressing FGF18 were generated by retroviral transduction and cell behavior was investigated by clonogenic growth and transwell assays. Plasma was collected from 40 PM patients, six patients with pleural fibrosis, and 40 healthy controls. Circulating FGF18 was measured by ELISA and correlated to clinicopathological parameters.

RESULTS

FGF18 showed high mRNA expression in PM and PM-derived cell lines. PM patients with high FGF18 mRNA expression showed a trend toward longer overall survival (OS) in the TCGA dataset. In PM cells with low endogenous FGF18 expression, forced overexpression of FGF18 resulted in reduced growth but increased migration. Surprisingly, despite the high FGF18 mRNA levels observed in PM, circulating FGF18 protein was significantly lower in PM patients and patients with pleural fibrosis than in healthy controls. No significant association of circulating FGF18 with OS or other disease parameters of PM patients was observed.

CONCLUSIONS

FGF18 is not a prognostic biomarker in PM. Its role in PM tumor biology and the clinical significance of decreased plasma FGF18 in PM patients warrant further investigation.

Chemical pleurodesis - a review of mechanisms involved in pleural space obliteration

Chemical pleurodesis is a therapeutic procedure applied to create the symphysis between the parietal and visceral pleura by intrapleural administration of various chemical agents (e.g. talk, tetracycline, iodopovidone, etc.). The two major clinical conditions treated with chemical pleurodesis are recurrent pleural effusion (PE) and recurrent spontaneous pneumothorax. Although the history of chemical pleurodesis began over a century ago, detailed data on the mechanisms of action of sclerosing agents are highly incomplete. The following article aims to present the state of knowledge on this subject.It is believed that mesothelial cells are the main structural axis of pleurodesis. In response to sclerosing agents they secrete a variety of mediators including chemokines such as interleukin 8 (IL-8) and monocyte chemoattractant protein (MCP-1), as well as growth factors - vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF) and transforming growth factor- β (TGF-β). Numerous data suggest that intact mesothelial cells and the above cytokines play a crucial role in the initiation and maintenance of different pathways of pleural inflammation and pleural space obliteration.It seems that the process of pleurodesis is largely nonspecific to the sclerosant and involves the same ultimate pathways including activation of pleural cells, coagulation cascade, fibrin chain formation, fibroblast proliferation and production of collagen and extracellular matrix components. Of these processes, the coagulation cascade with decreased fibrinolytic activity and increased fibrinogenesis probably plays a pivotal role, at least during the early response to sclerosant administration.A better understanding of various pathways involved in pleurodesis may be a prerequisite for more effective and safe use of various sclerosants and for the development of new, perhaps more personalized therapeutic approaches.

Expression of FGFR1-4 in Malignant Pleural Mesothelioma Tissue and Corresponding Cell Lines and its Relationship to Patient Survival and FGFR Inhibitor Sensitivity

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.

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.

Latest developments in our understanding of the pathogenesis of mesothelioma and the design of targeted therapies

Malignant mesothelioma is an aggressive cancer whose pathogenesis is causally linked to occupational exposure to asbestos. Familial clusters of mesotheliomas have been observed in settings of genetic predisposition. Mesothelioma incidence is anticipated to increase worldwide in the next two decades. Novel treatments are needed, as current treatment modalities may improve the quality of life, but have shown modest effects in improving overall survival. Increasing knowledge on the molecular characteristics of mesothelioma has led to the development of novel potential therapeutic strategies, including: molecular targeted approaches, that is the inhibition of vascular endothelial growth factor with bevacizumab; immunotherapy with chimeric monoclonal antibody, immunotoxin, antibody drug conjugate, vaccine and viruses; inhibition of asbestos-induced inflammation, that is aspirin inhibition of HMGB1 activity may decrease or delay mesothelioma onset and/or growth. We elaborate on the rationale behind new therapeutic strategies, and summarize available preclinical and clinical results, as well as efforts still ongoing.

Pleural mesothelial cells in pleural and lung diseases

During development, the mesoderm maintains a complex relationship with the developing endoderm giving rise to the mature lung. Pleural mesothelial cells (PMCs) derived from the mesoderm play a key role during the development of the lung. The pleural mesothelium differentiates to give rise to the endothelium and smooth muscle cells via epithelial-to-mesenchymal transition (EMT). An aberrant recapitulation of such developmental pathways can play an important role in the pathogenesis of disease processes such as idiopathic pulmonary fibrosis (IPF). The PMC is the central component of the immune responses of the pleura. When exposed to noxious stimuli, it demonstrates innate immune responses such as Toll-like receptor (TLR) recognition of pathogen associated molecular patterns as well as causes the release of several cytokines to activate adaptive immune responses. Development of pleural effusions occurs due to an imbalance in the dynamic interaction between junctional proteins, n-cadherin and β-catenin, and phosphorylation of adherens junctions between PMCs, which is caused in part by vascular endothelial growth factor (VEGF) released by PMCs. PMCs play an important role in defense mechanisms against bacterial and mycobacterial pleural infections, and in pathogenesis of malignant pleural effusion, asbestos related pleural disease and malignant pleural mesothelioma. PMCs also play a key role in the resolution of inflammation, which can occur with or without fibrosis. Fibrosis occurs as a result of disordered fibrin turnover and due to the effects of cytokines such as transforming growth factor-β, platelet-derived growth factor (PDGF), and basic fibroblast growth factor; which are released by PMCs. Recent studies have demonstrated a role for PMCs in the pathogenesis of IPF suggesting their potential as a cellular biomarker of disease activity and as a possible therapeutic target. Pleural-based therapies targeting PMCs for treatment of IPF and other lung diseases need further exploration.

Cytokines in pericardial effusion of patients with inflammatory pericardial disease

BACKGROUND

The role of inflammatory and angiogenic cytokines in patients with inflammatory pericardial effusion still remains uncertain.

METHODS

We assessed pericardial and serum levels of VEGF, bFGF, IL-1β and TNF-α by ELISA in patients with inflammatory pericardial effusion (PE) of autoreactive (n = 22) and viral (n = 11) origin, and for control in pericardial fluid (PF) and serum (n = 26) of patients with coronary artery disease (CAD) undergoing coronary artery bypass graft surgery.

RESULTS

VEGF levels were significantly higher in patients with autoreactive and viral PE than in patients with CAD in both PE (P = 0.006 for autoreactive and P < 0.001 for viral PE) and serum (P < 0.001 for autoreactive and P < 0.001 for viral PE). Pericardial bFGF levels were higher compared to serum levels in patients with inflammatory PE and patients with CAD (P ≤ 0.001 for CAD; P ≤ 0.001 for autoreactive PE; P = 0, 005 for viral PE). Pericardial VEGF levels correlated positively with markers of pericardial inflammation, whereas pericardial bFGF levels showed a negative correlation. IL-1β and TNF-α were detectable only in few PE and serum samples.

CONCLUSIONS

VEGF and bFGF levels in pericardial effusion are elevated in patients with inflammatory PE. It is thus possible that VEGF and bFGF participate in the pathogenesis of inflammatory pericardial disease.

Pleural mesothelioma instigates tumor-associated fibroblasts to promote progression via a malignant cytokine network

The tumor microenvironment is crucial to the progression of various malignancies. Malignant pleural mesothelioma (MPM), which originates from the pleura, grows aggressively in the thoracic cavity. Here we describe an orthotopic implantation SCID mouse model of MPM and demonstrate that α-SMA-positive fibroblast-like cells accumulate in the tumors produced by the human MPM cell lines MSTO-211H and Y-Meso-14. We assessed the interaction between MPM cells and their microenvironments, focusing on tumor-associated fibroblasts. MSTO-211H and Y-Meso-14 cells produced fibroblast growth factor-2 (FGF-2) and/or platelet-derived growth factor-AA (PDGF-AA); they also enhanced growth, migration, and production of hepatocyte growth factor (HGF) by human lung fibroblast MRC-5 cells. MRC-5 cells stimulated HGF-mediated growth and migration of MSTO-211H and Y-Meso-14 cells in an in vitro coculture system. In the orthotopic model, tumor formation by MSTO-211H and Y-Meso-14 cells was significantly inhibited by TSU-68, an inhibitor of FGF, VEGF, and PDGF receptors; imatinib, an inhibitor of PDGF receptors; and NK4, an antagonist of HGF. Histological analyses of clinical specimens from 51 MPM patients revealed considerable tumor-associated fibroblasts infiltration and expression of HGF, together with FGF-2 or PDGF-AA, in tumors. These findings indicate that MPM instigates tumor-associated fibroblasts, promoting tumor progression via a malignant cytokine network. Regulation of this cytokine network may be therapeutically useful for controlling MPM.

Inflammation precedes the development of human malignant mesotheliomas in a SCID mouse xenograft model

Asbestos fibers cause chronic inflammation that may be critical to the development of malignant mesothelioma (MM). Two human MM cell lines (Hmeso, PPM Mill) were used in a SCID mouse xenograft model to assess time-dependent patterns of inflammation and tumor formation. After intraperitoneal (IP) injection of MM cells, mice were euthanized at 7, 14, and 30 days, and peritoneal lavage fluid (PLF) was examined for immune cell profiles and human and mouse cytokines. Increases in human MM-derived IL-6, IL-8, bFGF, and VEGF were observed in mice at 7 days postinjection of either MM line, and a striking neutrophilia was observed at all time points. Free-floating tumor spheroids developed in mice at 14 days, and both spheroids and adherent MM tumor masses occurred in all mice at 30 days. Results suggest that inflammation and cytokine production precede and may be critical to the development of MMs.

Kinetics of host cell recruitment during dissemination of diffuse malignant peritoneal mesothelioma

Diffuse malignant mesothelioma is an aggressive tumor which displays a median survival of 11.2 months and a 5-year survival of less than 5% emphasizing the need for more effective treatments. This study uses an orthotopic model of malignant mesothelioma established in syngeneic, immunocompetent C57Bl/6 mice which produce malignant ascites and solid tumors that accurately replicate the histopathology of the human disease. Host stromal and immune cell accumulation within malignant ascites and solid tumors was determined using immunofluorescent labeling with confocal microscopy and fluorescence-activated cell sorting. An expression profile of cytokines and chemokines was produced using quantitative real-time PCR arrays. Tumor spheroids and solid tumors show progressive growth and infiltration with host stromal and immune cells including macrophages, endothelial cells, CD4(+) and CD8(+) lymphocytes, and a novel cell type, myeloid derived suppressor cells (MDSCs). The kinetics of host cell accumulation and inflammatory mediator expression within the tumor ascites divides tumor progression into two distinct phases. The first phase is characterized by progressive macrophage and T lymphocyte recruitment, with a cytokine profile consistent with regulatory T lymphocytes differentiation and suppression of T cell function. The second phase is characterized by decreased expression of macrophage chemotactic and T-cell regulating factors, an increase in MDSCs, and increased expression of several cytokines which stimulate differentiation of MDSCs. This cellular and expression profile suggests a mechanism by which host immune cells promote diffuse malignant mesothelioma progression.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (doi:10.1007/s12307-010-0048-1) contains supplementary material, which is available to authorized users.

Therapeutic effects of recombinant human endostatin adenovirus in a mouse model of malignant pleural effusion

PURPOSE

Malignant pleural effusion (MPE) is a common clinical problem in patients with advanced cancer. Evidence suggests that tumor-mediated angiogenesis and enhanced vascular permeability in the pleural wall are due to high levels of vascular endothelial growth factor (VEGF), which plays an important role in the pathogenesis of MPE. The present study was designed to test whether the recombinant adenovirus-mediated delivery of human endostatin (Ad-hEndo), one of the potent inhibitors of angiogenesis, would inhibit the formation and progression of MPE.

METHODS

We developed a novel mouse model of MPE by injecting Lewis lung carcinoma (LLC) cells directly into pleural cavity of C57BL/6 mice. To evaluate the therapeutic effects of endostatin in this MPE model, we injected the Ad-hEndo into the pleural cavity of MPE-bearing mice three times with the 3-day interval.

RESULTS

We found that this treatment resulted in significant reduction in pleural effusion volume, the number of pleural tumor foci, microvessel density, and vascular permeability, while it significantly prolonged the survival time. In addition, VEGF level of MPE in the group administered with the Ad-hEndo was obviously decreased as compared with that in the two control groups administered with null-adenovirus (Ad-null) or normal saline.

CONCLUSIONS

Our work provides a rationale for future studies toward evaluating the effectiveness of the adenovirus-based endostatin therapy for MPE.

Angiogenic factors and angiogenesis inhibitors in exudative pleural effusions

The angiogenesis system has been implicated in inflammatory and neoplastic processes; nevertheless, it has been little studied in relation to the pleural space. Our aim is to analyze pleural and plasma levels of the activators--vascular endothelial growth factor, basic fibroblastic growth factor, and inhibitors--endostatin and thrombospondin-1 and to estimate the association between these factors and related biochemical markers. We analyzed pleural fluid from 105 patients with one of the following types of pleural effusion: empyema or complicated parapneumonic, non-complicated parapneumonic, tuberculous, neoplastic and transudative. Angiogenesis activators were higher in exudates than in transudates (p < 0.001) and in empyema than in non-complicated parapneumonic patients (p < 0.001). Endostatin showed no significant differences. Trombospondin-1 showed higher levels in exudates than in transudates and in empyema than in non-complicated parapneumonic effusions (p < 0.001). In pleural exudates there was a positive correlation of angiogenesis activators and trombospondin-1 with low glucose and pH and high LDH. There was no correlation between pleural and plasma levels of the angiogenesis factors. We conclude that exudative pleural effusions showed higher vascular endothelial growth factor, basic-fibroblastic growth factor and trombospondin-1 values than transudative effusions that associated to low glucose and pH, and high LDH. There was no correlation between pleural and plasma concentrations, suggesting a compartmentalized response.