Project description:Brain tumors are among the most malignant cancers and can arise from neural stem cells or oligodendrocyte progenitor cells (OPCs). Glioma-propagating cells (GPCs) that have stem-like properties have been derived from tumor variants such as glioblastoma multiforme (GBM) and oligodendroglial tumors, the latter being more chemosensitive with better prognosis. It has been suggested that such differences in chemosensitivity arise from the different profiles of OPCs versus neural stem cells. We thus explored if GPCs derived from these glioma variants can serve as reliable in vitro culture systems for studies. We utilized gene expression analyses, since GBM and oligodendrogliomas can be molecularly classified. Accordingly, we derived a gene signature distinguishing oligodendroglial GPCs from GBM GPCs collated from different studies, which was enriched for the Wnt, Notch and TGF-beta pathways. Using a novel method in glioma biology, the Connectivity Map, we mapped the strength of gene signature association with patient gene expression profiles in 2 independent glioma databases [GSE16011, http://caintegrator-info.nci.nih.gov/rembrandt]. Our gene signature consistently stratified survival in glioma patients. This data would suggest that in vitro low passage GPCs are similarly driven by transcriptomic changes that characterize the favorable outcome of oligodendrogliomas over GBM. Additionally, the gene signature was associated with the 1p/19q co-deletion status, the current clinical indicator of chemosensitivity. Our gene signature detects molecular heterogeneity in oligodendroglioma patients that cannot be accounted for by histology or the 1p/19q status alone, and highlights the limitation of morphology-based histological analyses in tumor classification, consequently impacting on treatment decisions. Total RNA obtained from primary neurosphere culture from brain tumor specimens of 6 patients were compared. Replicate arrays were performed for all 6 neurosphere cultures.

Project description:Aims: We explore the role of elevated O2-:H2O2 ratio as a prosurvival signal in glioma-propagating cells (GPCs). We hypothesize that depleting this ratio sensitizes GPCs to apoptotic triggers. Results: We observed that elevated O2-:H2O2 ratio conferred enhanced resistance in GPCs, and depletion of this ratio by pharmacological and genetic methods sensitized cells to apopotic triggers. We established the ROS Index as a quantitative measure of normalized O2-:H2O2 ratio and determined its utility in predicting chemosensitivity. Importantly, mice implanted with GPCs of reduced ROS Index demonstrated extended survival. Analysis of tumor sections revealed effective targeting of CD133- and nestin-expressing neural precursors. Furthermore, we established the Connectivity Map to interrogate a gene signature derived from varied ROS Index for patterns of association with individual patient gene expression in 2 clinical databases. We showed that patients with reduced ROS Index demonstrate better survival. These data provide clinical evidence for the viability of our O2-:H2O2-mediated chemosensitivity profiles. Innovation and Conclusion: Gliomas are notoriously recurrent and highly infiltrative, and have been shown to arise from stem-like cells. We implicate elevated O2-:H2O2 ratio as a prosurvival signal in GPC self-renewal and proliferation. The ROS Index provides quantification of O2-:H2O2-mediated chemosensitivity, an advancement in a previously qualitative field. Intriguingly, glioma patients with reduced ROS Index correlate with longer survival and the Proneural molecular classification, a feature frequently associated with tumors of better prognosis. These data emphasize the feasibility of manipulating the O2-:H2O2 ratio as a therapeutic strategy. Total RNA from primary neurosphere culture of brain tumor specimens treated with DPI and DDC as well as non-treated CD133+ and CD133- fractions were compared. Specimens were obtained from 3 patients and replicate arrays were performed for all 3 neurosphere cultures.

Project description:Purpose: The most clearly established genetic hallmark in oligodendroglial tumors (OTs) is the combined loss of 1p/19q, a molecular alteration characteristic of tumors responding to therapy. Markers of tumoral progression have not yet been studied. Experimental Design: Novel markers of tumoral progression in OTs were sought through gene expression profiling analysis. Results: Unsupervised hierarchical cluster analysis classified OTs into two main groups associated with tumoral grade, independent of histological subtype and 1p/19q status. Differential gene expression analysis between low- and high-grade OTs revealed that only cell cycle-related genes were significantly upregulated in high-grade OTs. Among the deregulated genes, NDRG2 downregulation was detected in high-grade OTs with combined loss of 1p/19q. Expression analysis revealed low transcript levels of NDRG2 relative to non-tumoral brain tissue in 45% (9/20) of high-grade OTs. Furthermore, the low transcript levels of NDRG2 were significantly associated with a worse clinical outcome in patients. Transcript levels of NDRG2 were associated with promoter hypermethylation, which was detected in 38.4% (10/26) of high-grade OTs. The treatment of glioma cell lines T98 and LN18 with demethylating agents increased the mRNA expression levels of NDRG2 relative to the control cell line. Additionally, cell proliferation was significantly reduced and cell cycle was arrested in G1 phase after treatment with demethylating agents. Conclusions: Taken together, our results suggest that NDRG2 is a candidate tumor suppressor gene in OTs whose inactivation could be involved in tumoral progression and worse patient survival. The microarray study involved 28 glioma samples including oligodendrogliomas and oligoastrocytomas WHO grade II and III. Six non-tumoral brain tissues were used as controls, two of which were purchased from Stratagene (La Jolla, CA) and Clontech (Mountain View, CA). RNAs from several cell lines (Universal Human RNA, Stratagene, La Jolla, CA) was used as a standard reference in all hybridizations

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Stem-like glioma-propagating cells contribute to molecular heterogeneity and survival outcome in oligodendroglial tumors

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