Astrocytic, oligodendroglial and mixed gliomas are the commonest gliomas in adults. They have distinct phenotypes and clinical courses, but as they exist as a continuous histological spectrum, differentiating them can be difficult. Co-deletions of total 1p and 19q are found in the majority of oligodendrogliomas and considered as a diagnostic marker and a prognostic indicator. The 1p status of astrocytomas has not yet been thoroughly examined. Using a chromosome 1 tile path array, we investigated 108 adult astrocytic tumours for copy number alterations. Total 1p deletions were rare (2%), however partial deletions involving 1p36 were frequently identified in anaplastic astrocytomas (22%) and glioblastomas (34%). Multivariate analysis showed that patients with total 1p deletions had significantly longer survival (P ¼ 0.005). In nine glioblastomas homozygous deletions at 1p36 were identified. No somatic mutations were found among the five genes located in the homozygously deleted region. However, the CpG island of TNFRSF9 was hypermethylated in 19% of astrocytic tumours and 87% of glioma cell lines. TNFRSF9 expression was upregulated after demethylation of glioma cell lines. Akt3 amplifications were found in four glioblastomas. Our results indicate that 1p deletions are common anaplastic astrocytomas and glioblastomas but are distinct from the 1p abnormalities in oligodendrogliomas.
We studied the status of chromosomes 1 and 19 in 363 astrocytic and oligodendroglial tumors. Whereas the predominant pattern of copy number abnormality was a concurrent loss of the entire 1p and 19q regions (total 1p/19q loss) among oligodendroglial tumors and partial deletions of 1p and/or 19q in astrocytic tumors, a subset of apparently astrocytic tumors also had total 1p/19q loss. The presence of total 1p/19q loss was associated with longer survival of patients with all types of adult gliomas independent of age and diagnosis (P = .041). The most commonly deleted region on 19q in astrocytic tumors spans 885 kb in 19q13.33-q13.41, which is telomeric to the previously proposed region. Novel regions of homozygous deletion, including a part of DPYD (1p21.3) or the KLK cluster (19q13.33), were observed in anaplastic oligodendrogliomas. Amplifications encompassing AKT2 (19q13.2) or CCNE1 (19q12) were identified in some glioblastomas. Deletion mapping of the centromeric regions of 1p and 19q in the tumors that had total 1p/19q loss, indicating that the breakpoints lie centromeric to NOTCH2 within the pericentromeric regions of 1p and 19q. Thus, we show that the copy number abnormalities of 1p and 19q in human gliomas are complex and have distinct patterns that are prognostically predictive independent of age and pathological diagnosis. An accurate identification of total 1p/19q loss and discriminating this from other 1p/19q changes is, however, critical when the 1p/19q copy number status is used to stratify patients in clinical trials.
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