Apoptosis In Human Glioblastoma Cells Research Articles

Functionalized Glycomers as Growth Inhibitors and Inducers of Apoptosis in Human Glioblastoma Cells

The effects of functionalized aryl beta-D-glycopyranosides (glycomers) on the proliferation, survival, and apoptosis of human glioblastoma cells in culture were evaluated as a way to control tumor progression. The results showed that inhibition of growth and/or induction of apoptosis can be achieved by these molecules in human glioblastoma cells. Inhibition of DNA synthesis precedes induction of apoptosis and growth inhibition. The substituents at C-1, C-2, C-3,C-4, and C-6 on the pyranosidic scaffold are important to modulate the action and the efficacy of these molecules. Human fibroblasts and brain-derived endothelial cells were less sensitive to glycomers than tumor cells. Thus, functionalized aryl beta-D-glycopyranosides represent a new class of molecules potentially able to control the progression of brain tumors.

Static magnetic fields affect calcium fluxes and inhibit stress-induced apoptosis in human glioblastoma cells.

Epidemiologic data revealed increased brain tumor incidence in workers exposed to magnetic fields (MFs), raising concerns about the possible link between MF exposure and cancer. However, MFs seem to be neither mutagenic nor tumorigenic. The mechanism of their tumorigenic effect has not been elucidated. To evaluate the interference of MFs with physical (heat shock, HS) and chemical (etoposide, VP16) induced apoptoses, respectively, we exposed a human glioblastoma primary culture to 6 mT static MF. We investigated cytosolic Ca(2+) ([Ca(2+)](i)) fluxes and extent of apoptosis as key endpoints. The effect of MFs on HS- and VP16-induced apoptoses in primary glioblastoma cultures from four patients was also tested. Static MFs increased the [Ca(2+)](i) from a basal value of 124 +/- 4 nM to 233 +/- 43 nM (P < 0.05). MF exposure dramatically reduced the extent of HS- and VP16-induced apoptoses in all four glioblastoma primary cultures analyzed by 56% (range, 28-87%) and 44% (range, 38-48%), respectively. However, MF alone did not exert any apoptogenic activity. Differences were observed across the four cultures with regard to apoptotic induction by HS and VP16 and to MF apoptotic reduction, with an individual variability with regard to apoptotic sensitivity. The ability of static MFs to reduce the extent of damage-induced apoptosis in glioblastoma cells might allow the survival of damaged and possibly mutated cells.

Blockage of Ca(2+)-permeable AMPA receptors suppresses migration and induces apoptosis in human glioblastoma cells.

Glioblastoma multiforme is the most undifferentiated type of brain tumor, and its prognosis is extremely poor. Glioblastoma cells exhibit highly migratory and invasive behavior, which makes surgical intervention unsuccessful. Here, we showed that glioblastoma cells express Ca(2+)-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-type glutamate receptors assembled from the GluR1 and/or GluR4 subunits, and that their conversion to Ca(2+)-impermeable receptors by adenovirus-mediated transfer of the GluR2 cDNA inhibited cell locomotion and induced apoptosis. In contrast, overexpression of Ca(2+)-permeable AMPA receptors facilitated migration and proliferation of the tumor cells. These findings indicate that Ca(2+)-permeable AMPA receptors have crucial roles in growth of glioblastoma. Blockage of these Ca(2+)-permeable receptors may be a useful therapeutic strategy for the prevention of glioblastoma invasion.

Glycerol restores heat-induced p53-dependent apoptosis of human glioblastoma cells bearing mutant p53

BackgroundWe have previously reported that glycerol acts as a chemical chaperone to restore the expression of WAF1 in some human cancer cell lines bearing mutant p53. Since the expression of WAF1 is up-regulated by activated wildtype p53, glycerol appears to restore wtp53 function. The aim of the present study is to examine the restoration of heat-induced p53-dependent apoptosis by glycerol in human glioblastoma cells (A-172) transfected with a vector carrying a mutant p53 gene (A-172/mp53 cells) or neo control vector (A-172/neo cells).ResultsA-172/mp53 cells showed heat resistance compared with A-172/neo cells but A-172/mp53 cells in turn became heat sensitive when pre-treated with glycerol before heat treatment. The accumulation of Bax in the A-172/mp53 cells was induced by heating with glycerol pre-treatment, but not without it, whereas the accumulation in the A-172/neo cells was induced in both cases. Furthermore, mp53 extracted from heated cells came to bind to the sequence specific region after heating combined with glycerol pre-treatment. The phosphorylation of mp53 at serine15 was suppressed by an inhibitor of the phosphatidylinositol 3-kinase (PI3-K) family.ConclusionThese results suggest that glycerol is effective in inducing conformational change of phosphorylated p53 and restoring mp53 to wtp53 function, leading to enhanced heat sensitivity through the induction of apoptosis. This novel tool for enhancement of heat sensitivity in cancer cells bearing mp53 may be applicable for p53-targeted hyperthermia, because mutation or inactivation of p53 is observed in approximately 50% of human cancers.

Fas/CD95-mediated apoptosis in human glioblastoma cells: a target for sensitisation to topoisomerase I inhibitors

The expression of the death receptor Fas/CD95 is cell type-specific and can be modulated by different cytotoxic treatments. In spite of a frequent expression of Fas/CD95 in high-grade gliomas, these tumours are typically refractory to conventional therapy. Using a human glioblastoma cell line (GBM), we explored the possibility of modulating susceptibility to Fas/CD95-mediated apoptosis following cytotoxic treatment. GBM cells were sensitive to the antiproliferative effects of topoisomerase I inhibitors (topotecan and a novel lipophilic analog CPT83) and taxol, less sensitive to cisplatin and, in any case, rather resistant to drug-induced apoptosis. This pattern of cellular response was consistent with p53 mutation. GBM cells expressed low levels of Fas/CD95, which was associated with low susceptibility to antibody-stimulated Fas/CD95-mediated apoptosis. A significant up-regulation of Fas/CD95 expression was detected after exposure to topotecan and CPT83, whereas cisplatin induced a low increase and taxol did not modify Fas/CD95 expression. In addition, after treatment with topoisomerase I inhibitors, the up-regulation of Fas/CD95 resulted in an increased susceptibility of GBM cells to antibody-stimulated Fas/CD95-mediated apoptosis, while no synergistic effects were detected after treatment with cisplatin or taxol. Our data suggest that Fas/CD95 up-regulation can be a common response to DNA damage, whereas sensitisation to Fas/CD95-mediated apoptosis appears to be dependent on the type of DNA damage and on the pathway of cellular response. The observed effects might have important therapeutic implications for the design of novel therapeutic strategies in the treatment of malignant gliomas.

Connexin 43 (cx43) enhances chemotherapy‐induced apoptosis in human glioblastoma cells

Connexin 43 (cx43) enhances chemotherapy‐induced apoptosis in human glioblastoma cells

Connexin 43 (cx43) enhances chemotherapy-induced apoptosis in human glioblastoma cells

Stable re-expression of connexin 43 (cx43) in human glioblastoma suppresses transformation and tumorigenicity. The present study was designed to examine the role of cx43 in chemotherapy-induced apoptosis. Expression of cx43 in human glioblastoma cells significantly increased sensitivity to several common chemotherapeutic agents, including etoposide, paclitaxel (Taxol) and doxorubicin, compared with control-transfected cells. The increased sensitivity to chemotherapeutic agents resulted from apoptosis as evidenced by Hoechst dye staining, TUNEL assay and annexin V assay. These cx43-mediated effects were coupled with decreased expression of the specific apoptosis inhibitor bcl-2. Over-expression of bcl-2 in cx43-transfected cells partially confers the resistance to apoptosis induced by etoposide, suggesting that the cx43-mediated apoptosis to chemotherapeutic agents is regulated in part through the down-regulation of bcl-2 expression. Furthermore, the cx43-mediated apoptosis in response to chemotherapeutic drugs may not be linked to increased gap junctional communication in cx43-transfected cells. Our results demonstrate a new role of cx43 in the mediation of apoptosis during chemotherapy.

Participation of Bcl-2/Bax-alpha in glutamate-induced apoptosis of human glioblastoma cells.

Glutamate has been shown to function as a toxic agent in neuronal and glial cells, as well as an excitatory neurotransmitter throughout the central nervous system. In the present study, we examined the effect of increasing glutamate concentration on the induction of apoptosis in the two human glioblastoma cell lines GB-4 and GB-12. Glutamate exposure caused cell death of GB-4 and GB-12 in a dose-dependent manner. The cells were found to die via apoptosis in response to glutamate based on the following criteria: propidium iodide (PI) staining, H-E staining, electron microscopic analysis, and the TdT-mediated dUTP-biotin nick end labeling (TUNEL) method. The glutamate-induced apoptosis appears to involve the modulation of Bcl-2 family gene products such as Bcl-2, Bcl-xL, and Bax-alpha. Both Bcl-2 and Bcl-xL were down-regulated by glutamate at 24 h and further at 48 h. The apoptosis-promoting product p21 Bax-alpha was also down-regulated in GB-12 but slightly up-regulated in GB-4, accompanied by generation of variant form of p18 Bax-alpha in both cell lines. These findings suggest that glutamate toxicity results in cellular death via an apoptotic mechanism which appears to involve the Bcl-2/Bax-alpha molecular complex.