ASPM-associated stem cell proliferation is involved in malignant progression of gliomas and constitutes an attractive therapeutic target

<p>Abstract</p> <p>Background</p> <p>ASPM (<it>Abnormal Spindle-like Microcephaly associated</it>) over-expression was recently implicated in the development of malignant gliomas.</p> <p>Results</p> <p>To better characterize the involvement of ASPM in gliomas, we investigated the mRNA expression in 175 samples, including 8 WHO Grade II, 75 WHO Grade III and 92 WHO Grade IV tumors. <it>Aspm </it>expression was strongly correlated with tumor grade and increased at recurrence when compared to the initial lesion, whatever the initial grade of the primary tumor. ASPM expression also increased over serial passages in gliomaspheres <it>in vitro </it>and in mouse xenografts <it>in vivo</it>. Lentivirus-mediated shRNA silencing of ASPM resulted in dramatic proliferation arrest and cell death in two different gliomasphere models.</p> <p>Conclusion</p> <p>These data suggest that ASPM is involved in the malignant progression of gliomas, possibly through expansion of a cancer stem cell compartment, and is an attractive therapeutic target in glioblastoma multiforme.</p

RNA-sequencing of IDH-wild-type glioblastoma with chromothripsis identifies novel gene fusions with potential oncogenic properties

International audienceGlioblastoma (GBM) is the most frequent and most aggressive form of glioma. It is characterized by marked genomic instability, which suggests that chromothripsis (CT) might be involved in GBM initiation. Recently, CT has emerged as an alternative mechanism of cancer development, involving massive chromosome rearrangements in a one-step catastrophic event. The aim of the study was to detect CT in GBM and identify novel gene fusions in CT regions. One hundred and seventy IDH-wild-type GBM were screened for CT patterns using whole-genome single nucleotide polymorphism (SNP) arrays. RNA sequencing was performed in 52 GBM with CT features to identify gene fusions within CT regions. Forty tumors (40/52, 77%) harbored at least one gene fusion within CT regions. We identified 120 candidate gene fusions, 30 of which with potential oncogenic activities. We validated 11 gene fusions, which involved the most recurrent fusion partners (EGFR, SEPT14, VOPP1 and CPM), by RT-PCR and Sanger sequencing. The occurrence of CT points to underlying gene fusions in IDH-wild-type GBM. CT provides exciting new research avenues in this highly aggressive cancer

Traitement par tolvaptan dans la polykystose rénale autosomique dominante : aspects pratiques

International audienc

Mutational analysis of Rac2 in gliomas.

International audienc

No association of MDM2 SNP309 with risk of glioblastoma and prognosis

The MDM2 SNP309 variant has been shown to increase MDM2 expression and to be associated with tumor formation. In glioblastomas, the P53/MDM2 pathway is of crucial importance and MDM2 amplification is related to poor prognosis. However, we show here that MDM2 SNP309 is not associated with glioblastoma risk, and is not a prognostic factor

IDH Mutations: Genotype-Phenotype Correlation and Prognostic Impact

IDH1/2 mutation is the most frequent genomic alteration found in gliomas, affecting 40% of these tumors and is one of the earliest alterations occurring in gliomagenesis. We investigated a series of 1305 gliomas and showed that IDH mutation is almost constant in 1p19q codeleted tumors. We found that the distribution of IDH1R132H, IDH1nonR132H, and IDH2 mutations differed between astrocytic, mixed, and oligodendroglial tumors, with an overrepresentation of IDH2 mutations in oligodendroglial phenotype and an overrepresentation of IDH1nonR132H in astrocytic tumors. We stratified grade II and grade III gliomas according to the codeletion of 1p19q and IDH mutation to define three distinct prognostic subgroups: 1p19q and IDH mutated, IDH mutated—which contains mostly TP53 mutated tumors, and none of these alterations. We confirmed that IDH mutation with a hazard ratio = 0.358 is an independent prognostic factor of good outcome. These data refine current knowledge on IDH mutation prognostic impact and genotype-phenotype associations

NOTCH2 is neither rearranged nor mutated in t(1;19) positive oligodendrogliomas.

The combined deletion of 1p and 19q chromosomal arms is frequent in oligodendrogliomas (OD) and has recently been shown to be mediated by an unbalanced t(1;19) translocation. Recent studies of 1p/19q co-deleted OD suggest that the NOTCH2 gene is implicated in oligodendrocyte differentiation and may be involved in this rearrangement. The objective of the present study was to analyze the NOTCH2 locus either as a chromosomal translocation locus that may be altered by the 1p/19q recurrent rearrangement or as a gene that may be inactivated by a two hit process. We performed an array-CGH analysis of 15 ODs presenting 1p/19q co-deletion using a high-density oligonucleotide microarray spanning 1p and 19q pericentromeric regions with 377 bp average probe spacing. We showed that the 1p deletion extends to the centromere of chromosome 1 and includes the entire NOTCH2 gene. No internal rearrangement of this gene was observed. This strongly suggests that the t(1;19) translocation does not lead to an abnormal NOTCH2 structure. The analysis of the entire NOTCH2 coding sequence was performed in four cases and did not reveal any mutation therefore indicating that NOTCH2 does not harbor genetic characteristics of a tumor suppressor gene. Finally, the detailed analysis of chromosome 19 pericentromeric region led to the identification of two breakpoint clusters at 19p12 and 19q11-12. Interestingly, these two regions share a large stretch of homology. Together with previous observations of similarities between chromosome 1 and 19 alphoid sequences, this suggests that the t(1;19) translocation arises from complex intra and interchromosomal rearrangements.This is the first comprehensive deletion mapping by high density oligo-array of the 1p/19q co-deletion in oligodendroglioma tumors using a methodological approach superior to others previously applied. As such this paper provides clear evidence that the NOTCH2 gene is not physically rearranged by t(1;19) translocation of oligodendroglioma tumors

Mitochondrial DNA copy number as a prognostic marker is age-dependent in adult glioblastoma

International audienceBackground: Glioblastoma (GBM) is the most common and aggressive form of glioma. GBM frequently displays chromosome (chr) 7 gain, chr 10 loss and/or EGFR amplification (chr7+/chr10-/EGFRamp). Overall survival (OS) is 15 months after treatment. In young adults, IDH1/2 mutations are associated with longer survival. In children, histone H3 mutations portend a dismal prognosis. Novel reliable prognostic markers are needed in GBM. We assessed the prognostic value of mitochondrial DNA (mtDNA) copy number in adult GBM.Methods: mtDNA copy number was assessed using real-time quantitative PCR in 232 primary GBM. Methylation of POLG and TFAM genes, involved in mtDNA replication, was assessed by bisulfite-pyrosequencing in 44 and 51 cases, respectively.Results: Median age at diagnosis was 56.6 years-old and median OS, 13.3 months. 153/232 GBM (66 %) displayed chr7+/chr10-/EGFRamp, 23 (9.9 %) IDH1/2 mutation, 3 (1.3 %) H3 mutation and 53 (22.8 %) no key genetic alterations. GBM were divided into two groups, "Low" (n = 116) and "High" (n = 116), according to the median mtDNA/nuclear DNA ratio (237.7). There was no significant difference in OS between the two groups. By dividing the whole cohort according to the median age at diagnosis, OS was longer in the "High" vs "Low" subgroup (27.3 vs 15 months, P = .0203) in young adult GBM (n = 117) and longer in the "Low" vs "High" subgroup (14.5 vs 10.2 months, P = .0116) in older adult GBM (n = 115). POLG was highly methylated, whereas TFAM remained unmethylated.Conclusion: mtDNA copy number may be a novel prognostic biomarker in GBM, its impact depending on age

Tumor and Endothelial Cell Hybrids Participate in Glioblastoma Vasculature

International audienceBackground. Recently antiangiogenic therapy with bevacizumab has shown a high but transient efficacy in glioblastoma (GBM). Indeed , GBM is one of the most angiogenic human tumors and endothelial proliferation is a hallmark of the disease. We therefore hypothesized that tumor cells may participate in endothelial proliferation of GBM. Materials and Methods. We used EGFR FISH Probe to detect EGFR amplification and anti-CD31 , CD105 , VE-cadherin , and vWF to identify endothelial cells. Endothelial and GBM cells were grown separately , labeled with GFP and DsRed lentiviruses , and then cocultured with or without contact. Results. In a subset of GBM tissues , we found that several tumor endothelial cells carry EGFR amplification , characteristic of GBM tumor cells. This observation was reproduced in vitro : when tumor stem cells derived from GBM were grown in the presence of human endothelial cells , a fraction of them acquired endothelial markers (CD31 , CD105 , VE-cadherin , and vWF). By transduction with GFP and DsRed expressing lentiviral vectors , we demonstrate that this phenomenon is due to cell fusion and not transdifferentiation. Conclusion. A fraction of GBM stem cells thus has the capacity to fuse with endothelial cells and the resulting hybrids may participate in tumor microvascular proliferation and in treatment resistance