Identification of a Prognostic Microenvironment-Related Gene Signature in Glioblastoma Patients Treated with Carmustine Wafers

SIMPLE SUMMARY: Carmustine wafer (CW) implantation into the resection cavity of patients operated for glioblastoma (GBM) was approved as an adjuvant treatment before the Stupp Protocol. Although contrasting clinical results limited its use, our retrospective study on 116 GBM treated with CW showed a significant benefit in terms of OS in a subgroup of patients. Since GBM growth, progression, and drug resistance are supported by the surrounding environment, and since the tumor microenvironment (TME) is the source of druggable targets, we hypothesized that the TME of patients who benefited from CW could have different characteristics compared to patients who did not show any advantage. Exploiting a human in vitro model of glioma microenvironment and a transcriptomic approach, we found a different gene signature suggesting the importance of developing in vitro models that mimic the properties of human cancers and that can help to study individual patient characteristics at the cellular and molecular level. ABSTRACT: Despite the state-of-the-art treatment, patients diagnosed with glioblastoma (GBM) have a median overall survival (OS) of 14 months. The insertion of carmustine wafers (CWs) into the resection cavity as adjuvant treatment represents a promising option, although its use has been limited due to contrasting clinical results. Our retrospective evaluation of CW efficacy showed a significant improvement in terms of OS in a subgroup of patients. Given the crucial role of the tumor microenvironment (TME) in GBM progression and response to therapy, we hypothesized that the TME of patients who benefited from CW could have different properties compared to that of patients who did not show any advantage. Using an in vitro model of the glioma microenvironment, represented by glioma-associated-stem cells (GASC), we performed a transcriptomic analysis of GASC isolated from tumors of patients responsive and not responsive to CW to identify differentially expressed genes. We found different transcriptomic profiles, and we identified four genes, specifically down-regulated in GASC isolated from long-term survivors, correlated with clinical data deposited in the TCGA–GBM dataset. Our results highlight that studying the in vitro properties of patient-specific glioma microenvironments can help to identify molecular determinants potentially prognostic for patients treated with CW

Carmustine wafers implantation in patients with newly diagnosed high grade glioma: is it still an option?

Background: The implantation protocol for Carmustine Wafers (CWs) in high grade glioma (HGG) was developed to offer a bridge between surgical resection and adjuvant treatments, such as radio- and chemotherapy. In the last years, however, a widespread use of CWs has been limited due to uncertainties regarding efficacy, in addition to increased risk of infection and elevated costs of treatment. Objective: The aims of our study were to investigate the epidemiology of patients that underwent surgery for HGG with CW implantation, in addition to the assessment of related complications, long-term overall survival (OS), and associated prognostic factors. Methods: Three different medical databases were screened for conducting a systematic review of the literature, according to the PRISMA statement guidelines, evaluating the role of BCNU wafer implantation in patients with newly diagnosed HGG. The search query was based on a combination of medical subject headings (MeSH): "high grade glioma " [MeSH] AND "Carmustine " [MeSH] and free text terms: "surgery " OR "BCNU wafer " OR "Gliadel " OR "systemic treatment options " OR "overall survival. " Results: The analysis of the meta-data demonstrated that there was a significant advantage in using CWs in newly diagnosed GBM in terms of OS, and a very low heterogeneity among the included studies [mean difference 2.64 (95% CI 0.85, 4.44); p = 0.004; I2149 = 0%]. Conversely, no significant difference between the two treatment groups in terms of PFS wad detected (p = 0.55). The analysis of complications showed a relatively higher rate in Carmustine implanted patients, although this difference was not significant (p = 0.53). Conclusions: This meta-analysis seems to suggest that CWs implantation plays a significant role in improving the OS, when used in patients with newly diagnosed HGG. To minimize the risk of side effects, however, a carful patient selection based mainly on patient age and tumor volume should be desirable

Role of microenvironment in glioma invasion: What we learned from in vitro models

The invasion properties of glioblastoma hamper a radical surgery and are responsible for its recurrence. Understanding the invasion mechanisms is thus critical to devise new therapeutic strategies. Therefore, the creation of in vitro models that enable these mechanisms to be studied represents a crucial step. Since in vitro models represent an over-simplification of the in vivo system, in these years it has been attempted to increase the level of complexity of in vitro assays to create models that could better mimic the behaviour of the cells in vivo. These levels of complexity involved: 1. The dimension of the system, moving from two-dimensional to three-dimensional models; 2. The use of microfluidic systems; 3. The use of mixed cultures of tumour cells and cells of the tumour micro-environment in order to mimic the complex cross-talk between tumour cells and their micro-environment; 4. And the source of cells used in an attempt to move from commercial lines to patient-based models. In this review, we will summarize the evidence obtained exploring these different levels of complexity and highlighting advantages and limitations of each system used

Systemic T cells immunosuppression of glioma stem cell-derived exosomes is mediated by monocytic myeloid-derived suppressor cells

A major contributing factor to glioma development and progression is its ability to evade the immune system. Nano-meter sized vesicles, exosomes, secreted by glioma-stem cells (GSC) can act as mediators of intercellular communication to promote tumor immune escape. Here, we investigated the immunomodulatory properties of GCS-derived exosomes on different peripheral immune cell populations. Healthy donor peripheral blood mononuclear cells (PBMCs) stimulated with anti-CD3, anti-CD28 and IL-2, were treated with GSC-derived exosomes. Phenotypic characterization, cell proliferation, Th1/Th2 cytokine secretion and intracellular cytokine production were analysed by distinguishing among effector T cells, regulatory T cells and monocytes. In unfractionated PBMCs, GSC-derived exosomes inhibited T cell activation (CD25 and CD69 expression), proliferation and Th1 cytokine production, and did not affect cell viability or regulatory T-cell suppression ability. Furthermore, exosomes were able to enhance proliferation of purified CD4+ T cells. In PBMCs culture, glioma-derived exosomes directly promoted IL-10 and arginase-1 production and downregulation of HLA-DR by unstimulated CD14+ monocytic cells, that displayed an immunophenotype resembling that of monocytic myeloid-derived suppressor cells (Mo-MDSCs). Importantly, the removal of CD14+ monocytic cell fraction from PBMCs restored T-cell proliferation. The same results were observed with exosomes purified from plasma of glioblastoma patients. Our results indicate that glioma-derived exosomes suppress T-cell immune response by acting on monocyte maturation rather than on direct interaction with T cells. Selective targeting of Mo-MDSC to treat glioma should be considered with regard to how immune cells allow the acquirement of effector functions and therefore counteracting tumor progression

Semaphorin-7A on Exosomes: A Promigratory Signal in the Glioma Microenvironment

Exosomes are one of the most important mediators of the cross talk occurring between glioma stem cells (GSCs) and the surrounding microenvironment. We have previously shown that exosomes released by patient-derived glioma-associated stem cells (GASC) are able to increase, in vitro, the aggressiveness of both GSC and glioblastoma cell lines. To understand which molecules are responsible for this tumour-supporting function, we performed a descriptive proteomic analysis of GASC-exosomes and identified, among the others, Semaphorin7A (SEMA7A). SEMA7A was described as a promigratory cue in physiological and pathological conditions, and we hypothesised that it could modulate GSC migratory properties. Here, we described that SEMA7A is exposed on GASC-exosomes' surface and signals to GSC through Integrin \u3b21. This interaction activates focal adhesion kinase into GSC and increases their motility, in our patient-based in vitro model. Our findings suggest SEMA7A-\u3b21-integrin as a new target to disrupt the communication between GSCs and the supporting microenvironment

Size-dependent cellular uptake of exosomes

The ability of exosomes to elicit specific cellular responses suggests that they may be increasingly used as therapeutics. Their vesicular nature makes them suitable as potential nanocarriers for drugs or nucleic acids delivery. Here we address the question whether the method of preparation of enriched exosomal fractions can affect their uptake by cells and their ability to trigger a response. We compared ultracentrifugation and polymer-based precipitation methods on supernatants of glioma-associated stem cells isolated from a high-grade glioma patient. We determined particle size distributions after purification and their correlation with uptake, proliferation and migration in glioblastoma cell cultures. Our findings indicate that polymer-based precipitation leads to smaller particle size distributions, faster uptake by target cells and increased cellular motility. The different effect that isolation method-dependent populations of particles have on cell motility suggests their size distribution could also profoundly affect exosome therapeutic potential

Role of Microenvironment in Glioma Invasion: What We Learned from In Vitro Models

The invasion properties of glioblastoma hamper a radical surgery and are responsible for its recurrence. Understanding the invasion mechanisms is thus critical to devise new therapeutic strategies. Therefore, the creation of in vitro models that enable these mechanisms to be studied represents a crucial step. Since in vitro models represent an over-simplification of the in vivo system, in these years it has been attempted to increase the level of complexity of in vitro assays to create models that could better mimic the behaviour of the cells in vivo. These levels of complexity involved: 1. The dimension of the system, moving from two-dimensional to three-dimensional models; 2. The use of microfluidic systems; 3. The use of mixed cultures of tumour cells and cells of the tumour micro-environment in order to mimic the complex cross-talk between tumour cells and their micro-environment; 4. And the source of cells used in an attempt to move from commercial lines to patient-based models. In this review, we will summarize the evidence obtained exploring these different levels of complexity and highlighting advantages and limitations of each system used

Human Adipose-Derived Stem Cells in Madelung’s Disease: Morphological and Functional Characterization

Madelung Disease (MD) is a syndrome characterized by the accumulation of aberrant symmetric adipose tissue deposits. The etiology of this disease is yet to be elucidated, even though the presence of comorbidities, either genetic or environmental, has been reported. For this reason, establishing an in vitro model for MD is considered crucial to get insights into its physiopathology. We previously established a protocol for isolation and culture of stem cells from diseased tissues. Therefore, we isolated human adipose-derived stem cells (ASC) from MD patients and compared these cells with those isolated from healthy subjects in terms of surface phenotype, growth kinetic, adipogenic differentiation potential, and molecular alterations. Moreover, we evaluated the ability of the MD-ASC secretome to affect healthy ASC. The results reported a difference in the growth kinetic and surface markers of MD-ASC compared to healthy ASC but not in adipogenic differentiation. The most commonly described mitochondrial mutations were not observed. Still, MD-ASC secretome was able to shift the healthy ASC phenotype to an MD phenotype. This work provides evidence of the possibility of exploiting a patient-based in vitro model for better understanding MD pathophysiology, possibly favoring the development of novel target therapies