PTPRD and CNTNAP2 as markers of tumor aggressiveness in oligodendrogliomas

Oligodendrogliomas are typically associated with the most favorable prognosis among diffuse gliomas. However, many of the tumors progress, eventually leading to patient death. To characterize the changes associated with oligodendroglioma recurrence and progression, we analyzed two recurrent oligodendroglioma tumors upon diagnosis and after tumor relapse based on whole-genome and RNA sequencing. Relapsed tumors were diagnosed as glioblastomas with an oligodendroglioma component before the World Health Organization classification update in 2016. Both patients died within 12 months after relapse. One patient carried an inactivating POLE mutation leading to a clearly hypermutated progressed tumor. Strikingly, both relapsed tumors carried focal chromosomal rearrangements in PTPRD and CNTNAP2 genes with associated decreased gene expression. TP53 mutation was also detected in both patients after tumor relapse. In The Cancer Genome Atlas (TCGA) diffuse glioma cohort, PTPRD and CNTNAP2 expression decreased by tumor grade in oligodendrogliomas and PTPRD expression also in IDH-mutant astrocytomas. Low expression of the genes was associated with poor overall survival. Our analysis provides information about aggressive oligodendrogliomas with worse prognosis and suggests that PTPRD and CNTNAP2 expression could represent an informative marker for their stratification.publishedVersionPeer reviewe

<i>MYCN</i> amplification drives an aggressive form of spinal ependymoma

Spinal ependymal tumors form a histologically and molecularly heterogeneous group of tumors with generally good prognosis. However, their treatment can be challenging if infiltration of the spinal cord or dissemination throughout the central nervous system (CNS) occurs and, in these cases, clinical outcome remains poor. Here, we describe a new and relatively rare subgroup of spinal ependymal tumors identified using DNA methylation profiling that is distinct from other molecular subgroups of ependymoma. Copy number variation plots derived from DNA methylation arrays showed MYCN amplification as a characteristic genetic alteration in all cases of our cohort (n = 13), which was subsequently validated using fluorescence in situ hybridization. The histological diagnosis was anaplastic ependymoma (WHO Grade III) in ten cases and classic ependymoma (WHO Grade II) in three cases. Histological re-evaluation in five primary tumors and seven relapses showed characteristic histological features of ependymoma, namely pseudorosettes, GFAP- and EMA positivity. Electron microscopy revealed cilia, complex intercellular junctions and intermediate filaments in a representative sample. Taking these findings into account, we suggest to designate this molecular subgroup spinal ependymoma with MYCN amplification, SP-EPN-MYCN. SP-EPN-MYCN tumors showed distinct growth patterns with intradural, extramedullary localization mostly within the thoracic and cervical spine, diffuse leptomeningeal spread throughout the whole CNS and infiltrative invasion of the spinal cord. Dissemination was observed in 100% of cases. Despite high-intensity treatment, SP-EPN-MYCN showed significantly worse median progression free survival (PFS) (17 months) and median overall survival (OS) (87 months) than all other previously described molecular spinal ependymoma subgroups. OS and PFS were similar to supratentorial ependymoma with RELA-fusion (ST-EPN-RELA) and posterior fossa ependymoma A (PF-EPN-A), further highlighting the aggressiveness of this distinct new subgroup. We, therefore, propose to establish SP-EPN-MYCN as a new molecular subgroup in ependymoma and advocate for testing newly diagnosed spinal ependymal tumors for MYCN amplification

Evaluation of Storage Tubes for Combined Analysis of Circulating Nucleic Acids in Liquid Biopsies

In the last decade, circulating nucleic acids such as microRNAs (miRNAs) and cell-free DNA (cfDNA) have become increasingly important in serving as potential novel biomarkers for a variety of human diseases. If cell-free nucleic acids are to become routinely used in diagnostics, the difference in plasma miRNA and cfDNA levels between healthy and diseased subjects must exceed pre-analytical and analytical variability. Until now, few studies have addressed the time limitations of pre-processing or explored the potential use of long-term blood storage tubes, which might need to be implemented in real-life diagnostics. In this study, we analyzed the stability of four breast cancer-associated miRNAs and two cancer-associated genes under various storage conditions, to test their limitations for potential application in clinical diagnostics. In two consecutive experiments, we tested the limits of conventional EDTA tubes, as well as long-term storage blood collection tubes (BCTs) from four different manufacturers. We found that circulating miRNAs are relatively stable when stored in EDTA monovettes for up to 12 h before processing. When stored in BCTs, circulating miRNAs and cfDNA are stable for up to 7 days, depending on the manufacturer. Norgen tubes were superior for cfDNA yield, while Streck tubes performed the worst in our study with hemolysis induction. In conclusion, plasma prepared from whole blood is suitable for the quantification of both cf-miRNAs and cfDNA simultaneously

PTPRD and CNTNAP2 as markers of tumor aggressiveness in oligodendrogliomas.

Oligodendrogliomas are typically associated with the most favorable prognosis among diffuse gliomas. However, many of the tumors progress, eventually leading to patient death. To characterize the changes associated with oligodendroglioma recurrence and progression, we analyzed two recurrent oligodendroglioma tumors upon diagnosis and after tumor relapse based on whole-genome and RNA sequencing. Relapsed tumors were diagnosed as glioblastomas with an oligodendroglioma component before the World Health Organization classification update in 2016. Both patients died within 12 months after relapse. One patient carried an inactivating POLE mutation leading to a clearly hypermutated progressed tumor. Strikingly, both relapsed tumors carried focal chromosomal rearrangements in PTPRD and CNTNAP2 genes with associated decreased gene expression. TP53 mutation was also detected in both patients after tumor relapse. In The Cancer Genome Atlas (TCGA) diffuse glioma cohort, PTPRD and CNTNAP2 expression decreased by tumor grade in oligodendrogliomas and PTPRD expression also in IDH-mutant astrocytomas. Low expression of the genes was associated with poor overall survival. Our analysis provides information about aggressive oligodendrogliomas with worse prognosis and suggests that PTPRD and CNTNAP2 expression could represent an informative marker for their stratification

Cross-Species Genomics Reveals Oncogenic Dependencies in ZFTA/C11orf95 Fusion-Positive Supratentorial Ependymomas

Molecular groups of supratentorial ependymomas comprise tumors with ZFTA-RELA or YAP1-involving fusions and fusion-negative subependymoma. However, occasionally supratentorial ependymomas cannot be readily assigned to any of these groups due to lack of detection of a typical fusion and/or ambiguous DNA methylation-based classification. An unbiased approach with a cohort of unprecedented size revealed distinct methylation clusters composed of tumors with ependymal but also various other histologic features containing alternative translocations that shared ZFTA as a partner gene. Somatic overexpression of ZFTA-associated fusion genes in the developing cerebral cortex is capable of inducing tumor formation in vivo, and cross-species comparative analyses identified GLI2 as a key downstream regulator of tumorigenesis in all tumors. Targeting GLI2 with arsenic trioxide caused extended survival of tumor-bearing animals, indicating a potential therapeutic vulnerability in ZFTA fusion-positive tumors. SIGNIFICANCE: ZFTA-RELA fusions are a hallmark feature of supratentorial ependymoma. We find that ZFTA acts as a partner for alternative transcriptional activators in oncogenic fusions of supratentorial tumors with various histologic characteristics. Establishing representative mouse models, we identify potential therapeutic targets shared by ZFTA fusion-positive tumors, such as GLI2.This article is highlighted in the In This Issue feature, p. 2113