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Targeting the GD3 acetylation pathway selectively induces apoptosis in glioblastoma.

ABSTRACT: The expression of ganglioside GD3, which plays crucial roles in normal brain development, decreases in adults but is upregulated in neoplastic cells, where it regulates tumor invasion and survival. Normally a buildup of GD3 induces apoptosis, but this does not occur in gliomas due to formation of 9-O-acetyl GD3 by the addition of an acetyl group to the terminal sialic acid of GD3; this renders GD3 unable to induce apoptosis. Using human biopsy-derived glioblastoma cell cultures, we have carried out a series of molecular manipulations targeting GD3 acetylation pathways. Using immunocytochemistry, flow cytometry, western blotting, and transwell assays, we have shown the existence of a critical ratio between GD3 and 9-O-acetyl GD3, which promotes tumor survival. Thus, we have demonstrated for the first time in primary glioblastoma that cleaving the acetyl group restores GD3, resulting in a reduction in tumor cell viability while normal astrocytes remain unaffected. Additionally, we have shown that glioblastoma viability is reduced due to the induction of mitochondrially mediated apoptosis and that this occurs after mitochondrial membrane depolarization. Three methods of cleaving the acetyl group using hemagglutinin esterase were investigated, and we have shown that the baculovirus vector transduces glioma cells as well as normal astroctyes with a relatively high efficacy. A recombinant baculovirus containing hemagglutinin esterase could be developed for the clinic as an adjuvant therapy for glioma.

SUBMITTER: Birks SM

PROVIDER: S-EPMC3158019 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Targeting the GD3 acetylation pathway selectively induces apoptosis in glioblastoma.

Birks Suzanne M SM Danquah John Owusu JO King Linda L Vlasak Reinhardt R Gorecki Dariusz C DC Pilkington Geoffrey J GJ

Neuro-oncology 20110731 9

The expression of ganglioside GD3, which plays crucial roles in normal brain development, decreases in adults but is upregulated in neoplastic cells, where it regulates tumor invasion and survival. Normally a buildup of GD3 induces apoptosis, but this does not occur in gliomas due to formation of 9-O-acetyl GD3 by the addition of an acetyl group to the terminal sialic acid of GD3; this renders GD3 unable to induce apoptosis. Using human biopsy-derived glioblastoma cell cultures, we have carried ...[more]

PMID: 21807667

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Project description:BACKGROUND:Inhibition of p38 MAPK signalling leads to glioblastoma multiform (GBM) tumourigenesis. Nevertheless, the molecular mechanism that induces p38 MAPK signalling pathway silencing during GBM genesis has yet to be determined. Identifying new factors that can regulate p38 MAPK signalling is important for tumour treatment. METHODS:Flow cytometry, TUNEL assays, immunofluorescence, JC-1 assays, and western blot analyses were used to detect the apoptosis of GBM cells. The specific methods used to detect autophagy levels in GBM cells were western blot analysis, LC3B protein immunofluorescence, LC3B puncta assays and transmission electron microscopy. The functions of these critical molecules were further confirmed in vivo by intracranial xenografts in nude mice. Tumour tissue samples and clinical information were used to identify the correlation between RND2 and p62 and LC3B expression, survival time of patients, and tumour volumes in clinical patients. RESULTS:By summarizing data from the TCGA database, we found that expression of the small GTPase RND2 was significantly increased in human glioblastomas. Our study demonstrated that RND2 functions as an endogenous repressor of the p38 MAPK phosphorylation complex. RND2 physically interacted with p38 and decreased p38 phosphorylation, thereby inhibiting p38 MAPK signalling activities. The forced expression of RND2 repressed p38 MAPK signalling, which inhibited glioblastoma cell autophagy and apoptosis in vitro and induced tumour growth in the xenografted mice in vivo. By contrast, the downregulation of RND2 enhanced p38 MAPK signalling activities and promoted glioma cell autophagy and apoptosis. The inhibition of p38 phosphorylation abolished RND2 deficiency-mediated GBM cell autophagy and apoptosis. Most importantly, our study found that RND2 expression was inversely correlated with patient survival time and was positively correlated with tumour size. CONCLUSIONS:Our findings revealed a new function for RND2 in GBM cell death and offered mechanistic insights into the inhibitory effects of RND2 with regard to the regulation of p38 MAPK activation.

Project description:Dcf1 has been demonstrated to play vital roles in many CNS diseases, it also has a destructive role on cell mitochondria in glioma cells and promotes the autophagy. Hitherto, it is unclear whether the viability of glioblastoma cells is affected by Dcf1, in particular Dcf1 possesses broad localization on different organelles, and the organelles interaction frequently implicated in cancer cells survival. Surgically excised WHO grade IV human glioblastoma tissues were collected and cells isolated for culturing. RT-PCR and DNA sequencing assay to estimate the abundance and mutation of Dcf1. iTRAQ sequencing and bioinformatic analysis were performed. Subsequently, immunoprecipitation assay to evaluate the degradation of HistoneH2A isomers by UBA52 ubiquitylation. Transmission electron microscopy (TEM) was applied to observe the structure change of mitochondria and autophagosome. Organelle isolated assay to determine the distribution of protein. Cell cycle and apoptosis were evaluated by flow cytometric assays. Dcf1 was downregulated in WHO grade IV tumor without mutation, and overexpression of Dcf1 was found to significantly regulate glioblastoma cells. One hundred and seventy-six differentially expressed proteins were identified by iTRAQ sequencing. Furthermore, we confirmed that overexpression of Dcf1 destabilized the structure of the nucleosome via UBA52 ubiquitination to downregulate HistoneH2A.X but not macroH2A or HistoneH2A.Z, decreased the mitochondrial DNA copy number and inhibited the mitochondrial biogenesis, thus causing mitochondrial destruction and dysfunction in order to supply cellular energy and induce mitophagy preferentially but not apoptosis. Dcf1 also has disrupted the integrity of lysosomes to block autolysosome degradation and autophagy and to increase the release of Cathepsin B and D from lysosomes into cytosol. These proteins cleaved and activated BID to induce glioblastoma cells apoptosis. In this study, we demonstrated that unmutated Dcf1 expression is negatively related to the malignancy of glioblastoma, Dcf1 overexpression causes nucleosomes destabilization, mitochondria destruction and dysfunction to induce mitophagy preferentially, and block autophagy by impairing lysosomes to induce apoptosis in glioblastoma.

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Targeting the GD3 acetylation pathway selectively induces apoptosis in glioblastoma.

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Targeting the GD3 acetylation pathway selectively induces apoptosis in glioblastoma.

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