Oligodendroglioma cells shed microvesicles which contain TRAIL as well as molecular chaperones and induce cell death in astrocytes

Abstract

Abstract. Microvesicles (MVs) shed from G26/24 oligodendroglioma cells were previously reported to cause a reproducible, dose-dependent, inhibitory effect on neurite outgrowth, and eventually neuronal apoptosis, when added to primary cultures of rat cortical neurons. These effects were reduced but not abolished by functional monoclonal antibodies against Fas-L. In order to investigate whether MVs contain other factors able to induce cell death, we tested them for TRAIL and found clear evidence of its presence in the vesicles. This finding suggests the possibility that Fas-L and TRAIL cooperate in inducing brain cell death. Aimed at understanding the route through which the vesicles deliver their messages to the target cells, we labeled oligodendroglioma cells with radioactive methionine and then added the labeled vesicles shed from tumor cells to unlabeled astrocytes in culture. Here we report that labeled proteins were delivered to the test cells. In order to investigate whether astrocytes, like neurons, are sensitive to oligodendroglioma-derived vesicles, MVs were prepared from media conditioned by G26/24 oligodendroglioma cells and added to primary cultures of rat cortical astrocytes. These cells were clearly more resistant than neurons to microvesicle-induced damage: a high dose (40 µg) of shed MVs induced cell death in only about 40% of astrocytes. Finally, we demonstrated that Hsp70 is specifically enriched in MVs which also contain, even if at lower level, the Hsc70 constitutive chaperone. IntroductionA peculiar route for cell-to-cell communication could be mediated by extracellular membrane vesicles. Two distinct types of signaling vesicles have been identified up to now: i) vesicles with a diameter of 30-100 nm, known as exosomes, released from the cell by exocytosis of multivesicular bodies (MVBs), intracellular organelles of the endosomal system; ii) small vesicles, called shed vesicles (SVs), 100 nm -1 µm in diameter, released into the extracellular space by direct budding from the plasma membrane. Mixed vesicle populations, containing both shedding vesicles and exosomes, will be referred to as microvesicles (MVs) (1,2).Upon release, both types of microvesicles circulate in the extracellular space adjacent to the site of discharge where they can be broken down, often within a few minutes. Some of them, however, can move some distance by diffusion and can appear in biological fluids, such as cerebrospinal fluid, blood and urine. In some cases microvesicles deliver transmembrane signals which activate surface receptors (3); in other cases they function not only as messengers, but also as platforms necessary for the coordinate development of multisignaling processes (4). Being membrane-bound structures, microvesicles can fuse with their target cells. Because of these properties, MVs, which seem to be enriched in specific proteins and mRNAs (5), have been suggested to function in signaling as well as in the horizontal transfer of their membrane and/or cargo molecules (6).Different neural cells release MV...

Role of Exosomes/Microvesicles in the Nervous System and Use in Emerging Therapies

“…Parallel studies showed that the mRNA for EGFRvIII is also present in EMVs from mutant-positive tumor cells and can be detected in serum EMVs from patients who harbor the corresponding mutation in their tumors, thereby providing a biomarker for genetic status of the tumors (Skog et al, 2008). Others have shown that oligodendroglioma cells send out EMVs containing the apoptotic protein, TRAIL, which leads to death of normal astrocytes and neurons (Lo Cicero et al, 2011). …”

Glioblastoma extracellular vesicles: reservoirs of potential biomarkers

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Temozolomide sensitizes stem-like cells of glioma spheres to TRAIL-induced apoptosis via upregulation of casitas B-lineage lymphoma (c-Cbl) protein

“…Thus, new therapeutic approaches are urgently needed. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has great promise as an anticancer drug because of its potent proapoptotic effects on cancer cell and negligible toxicity on healthy cells, including human astrocytes [2]. Glioma stem cells, a self-renewing and tumorigenic subpopulation of glioma cells, have been implicated in the treatment resistance of glioblastoma (GBM) and could therefore be responsible for resistance to TRAIL-induced cell death observed in gliomas [3].…”