Impairing temozolomide resistance driven by glioma stem-like cells with adjuvant immunotherapy targeting O-acetyl GD2 ganglioside.

Stem cell chemoresistance remains challenging the efficacy of the front-line temozolomide against glioblastoma. Novel therapies are urgently needed to fight those cells in order to control tumor relapse. Here, we report that anti-O-acetyl-GD2 adjuvant immunotherapy controls glioma stem-like cell-driven chemoresistance. Using patient-derived glioblastoma cells, we found that glioma stem-like cells overexpressed O-acetyl-GD2. As a result, monoclonal antibody 8B6 immunotherapy significantly increased temozolomide genotoxicity and tumor cell death in vitro by enhancing temozolomide tumor uptake. Furthermore, the combination therapy decreased the expression of the glioma stem-like cell markers CD133 and Nestin and compromised glioma stem-like cell self-renewal capabilities. When tested in vivo, adjuvant 8B6 immunotherapy prevented the extension of the temozolomide-resistant glioma stem-like cell pool within the tumor bulk in vivo and was more effective than the single agent therapies. This is the first report demonstrating that anti-O-acetyl-GD2 monoclonal antibody 8B6 targets glioblastoma in a manner that control temozolomide-resistance driven by glioma stem-like cells. Together our results offer a proof of concept for using anti-O-acetyl GD2 reagents in glioblastoma to develop more efficient combination therapies for malignant gliomas.

Mitochondria transfer from tumor-activated stromal cells (TASC) to primary Glioblastoma cells.

The tumor microenvironment (TME) controls many aspects of cancer development but little is known about its effect in Glioblastoma (GBM), the main brain tumor in adults. Tumor-activated stromal cell (TASC) population, a component of TME in GBM, was induced in vitro by incubation of MSCs with culture media conditioned by primary cultures of GBM under 3D/organoid conditions. We observed mitochondrial transfer by Tunneling Nanotubes (TNT), extracellular vesicles (EV) and cannibalism from the TASC to GBM and analyzed its effect on both proliferation and survival. We created primary cultures of GBM or TASC in which we have eliminated mitochondrial DNA [Rho 0 (ρ0) cells]. We found that TASC, as described in other cancers, increased GBM proliferation and resistance to standard treatments (radiotherapy and chemotherapy). We analyzed the incorporation of purified mitochondria by ρ0 and ρ+ cells and a derived mathematical model taught us that ρ+ cells incorporate more rapidly pure mitochondria than ρ0 cells.

Low-Dose Pesticide Mixture Induces Accelerated Mesenchymal Stem Cell Aging In Vitro.

The general population is chronically exposed to multiple environmental contaminants such as pesticides. We have previously demonstrated that human mesenchymal stem cells (MSCs) exposed in vitro to low doses of a mixture of seven common pesticides showed a permanent phenotype modification with a specific induction of an oxidative stress-related senescence. Pesticide mixture also induced a shift in MSC differentiation toward adipogenesis. Thus, we hypothesized that common combination of pesticides may induce a premature cellular aging of adult MSCs. Our goal was to evaluate if the prolonged exposure to pesticide mixture could accelerate aging-related markers and in particular deteriorate the immunosuppressive properties of MSCs. MSCs exposed to pesticide mixture, under long-term culture and obtained from aging donor, were compared by bulk RNA sequencing analysis. Aging, senescence, and immunomodulatory markers were compared. The protein expression of cellular aging-associated metabolic markers and immune function of MSCs were analyzed. Functional analysis of the secretome impacts on immunomodulatory properties of MSCs was realized after 21 days' exposure to pesticide mixture. The RNA sequencing analysis of MSCs exposed to pesticide showed some similarities with cells from prolonged culture, but also with the MSCs of an aged donor. Changes in the metabolic markers MDH1, GOT and SIRT3, as well as an alteration in the modulation of active T cells and modifications in cytokine production are all associated with cellular aging. A modified functional profile was found with similarities to aging process. Stem Cells 2019;37:1083-1094.

Tumor cells hijack enteric glia to activate colon cancer stem cells and stimulate tumorigenesis.

BACKGROUND: Colon cancer stem cells (CSCs), considered responsible for tumor initiation and cancer relapse, are constantly exposed to regulatory cues emanating from neighboring cells present in the tumor microenvironment. Among these cells are enteric glial cells (EGCs) that are potent regulators of the epithelium functions in a healthy intestine. However, whether EGCs impact CSC-driven tumorigenesis remains unknown. METHODS: Impact of human EGC primary cultures or a non-transformed EGC line on CSCs isolated from human primary colon adenocarcinomas or colon cancer cell lines with different p53, MMR system and stemness status was determined using murine xenograft models and 3D co-culture systems. Supernatants of patient-matched human primary colon adenocarcinomas and non-adjacent healthy mucosa were used to mimic tumor versus healthy mucosa secretomes and compare their effects on EGCs. FINDINGS: Our data show that EGCs stimulate CSC expansion and ability to give rise to tumors via paracrine signaling. Importantly, only EGCs that were pre-activated by tumor epithelial cell-derived soluble factors increased CSC tumorigenicity. Pharmacological inhibition of PGE2 biosynthesis in EGCs or IL-1 knockdown in tumor epithelial cells prevented EGC acquisition of a pro-tumorigenic phenotype. Inhibition of PGE2 receptor EP4 and EGFR in CSCs inhibited the effects of tumor-activated EGCs. INTERPRETATION: Altogether, our results show that EGCs, once activated by the tumor, acquire a pro-tumorigenic phenotype and stimulate CSC-driven tumorigenesis via a PGE2/EP4/EGFR-dependent pathway. FUNDING: This work was supported by grants from the French National Cancer Institute, La Ligue contre le Cancer, the 'Région des Pays de la Loire' and the UNC Lineberger Comprehensive Cancer Center.

Efficient Mitochondrial Glutamine Targeting Prevails Over Glioblastoma Metabolic Plasticity.

Purpose: Glioblastoma (GBM) is the most common and malignant form of primary human brain tumor in adults, with an average survival at diagnosis of 18 months. Metabolism is a new attractive therapeutic target in cancer; however, little is known about metabolic heterogeneity and plasticity within GBM tumors. We therefore aimed to investigate metabolic phenotyping of primary cultures in the context of molecular tumor heterogeneity to provide a proof of concept for personalized metabolic targeting of GBM.Experimental Design: We have analyzed extensively several primary GBM cultures using transcriptomics, metabolic phenotyping assays, and mitochondrial respirometry.Results: We found that metabolic phenotyping clearly identifies 2 clusters, GLNHigh and GLNLow, mainly based on metabolic plasticity and glutamine (GLN) utilization. Inhibition of glutamine metabolism slows the in vitro and in vivo growth of GLNHigh GBM cultures despite metabolic adaptation to nutrient availability, in particular by increasing pyruvate shuttling into mitochondria. Furthermore, phenotypic and molecular analyses show that highly proliferative GLNHigh cultures are CD133neg and display a mesenchymal signature in contrast to CD133pos GLNLow GBM cells.Conclusions: Our results show that metabolic phenotyping identified an essential metabolic pathway in a GBM cell subtype, and provide a proof of concept for theranostic metabolic targeting. Clin Cancer Res; 23(20); 6292-304. ©2017 AACR.

Targeting and killing glioblastoma with monoclonal antibody to O-acetyl GD2 ganglioside.

There are still unmet medical needs in the treatment of glioblastoma, the most common and the most aggressive glioma of all brain tumors. Here, we found that O-acetyl GD2 is expressed in surgically resected human glioblastoma tissue. In addition, we demonstrated that 8B6 monoclonal antibody specific for O-acetylat GD2 could effectively inhibit glioblastoma cell proliferation in vitro and in vivo. Taken together, these results indicate that O-acetylated GD2 represents a novel antigen for immunotherapeutic-based treatment of high-grade gliomas.