Project description:Introduction: single-cell RNA sequencing identified multiple subpopulations in childhood posterior fossa ependymoma. The contribution of individual neoplastic subpopulations to bulk tumor transcriptome-based molecular classification and patient outcome was estimated by deconvolution in a cohort of clinically-annotated primary and recurrent EPN samples. The abundance of EPN subpopulations was estimated in primary EPN samples and showed that the ratio of subpopulation fractions dictated assignment to the two main transcriptomic classification subgroups in childhood posterior fossa ependymoma. Longitudinal analysis revealed that subpopulation fractions changed between presentation and recurrence. Outcome analyses demonstrated that a different proportions of subpopulations were associated with differential survival.
Project description:Ependymoma (EPN) is a brain tumor commonly presenting in childhood that remains fatal in the majority of children. Intra-tumoral cellular heterogeneity in bulk tumor samples significantly confounds our understanding of EPN biology, impeding development of effective therapy. We used single-cell RNA sequencing to identify four neoplastic cell subpopulations in posterior fossa EPN patient samples that underlie traditional subgroup classification and harbor divergent lineage trajectories and clinical outcomes. Neoplastic subpopulations expressed gene signatures associated with normal ependyma, ependymoma, and mesenchymal phenotypes, consequently named ciliated (CEC), transportive (TEC), undifferentiated (UEC), and mesenchymal ependymoma cells (MEC). The abundance of EPN subpopulations as estimated by deconvolution of EPN bulk tumor transcriptomes showed that the ratio of MEC and CEC cell fractions dictated assignment to the two main classification subgroups in PFA. Longitudinal analysis revealed evolution of subpopulation fractions, notably MEC and CEC, which changed between presentation and recurrence. Outcome analyses demonstrated that a higher proportion of UEC or MEC subpopulations was associated with shorter survival, whereas CEC was associated with longer survival. Unsupervised pseudotime analysis revealed divergent subpopulation lineages. The first lineage conformed to a classic cancer stem cell trajectory where UEC progenitors differentiate sequentially to TECs and then CECs. In the second trajectory MECs arise from UECs via TECs, potentially in response to hypoxia-mediated cellular stress, a process that we recreated in vitro in a hypoxia treated EPN cell line. Our study reveals the existence of significant, unappreciated cellular heterogeneity in EPN and provides important resolution of EPN tumor biology.
Project description:We compared molecular characteristics of primary and recurrent pediatric ependymoma to identify sub-group specific differences. Gene expression profiles were used to identify unique immunobiologic sub-types of posterior fossa pediatric ependymoma. Gene expression profiles were generated from surgical tumor (ependymoma) (n=65) using Affymetrix HG-U133plus2 chips (Platform GPL570). Normalization was performed on our entire cohort of ependymoma. Of the 65 samples, a sub-set of 58 were used in the corresponding manuscript. Excluded samples are noted. Gene expression profiles were filtered to obtain gene expression of key immune cell markers. Comparative analyses between tumor samples were used to identifiy unique immunobiology between posterior fossa sub-groups.
Project description:Pediatric ependymoma has relatively low frequencies of DNA mutations, which suggest that epigenetics may drive tumors. However, the epigenetic mechanisms for recurrent ependymoma are still poorly understood. Here, we performed longitudinal and comprehensive DNA methylation and gene expression analysis for recurrent pediatric ependymoma tumors from 10 patients, total 46 DNA methylomes (including primary tumors and matched recurrent tumors; normal pediatric brain tissues and PDOX tumors). Both RELA and PFA tumors maintained the subtype DNA methylation signatures during repeated relapses. We further identified the potential DNA methylation predictors, drivers and boosters and their potential regulated genes for recurrent ependymoma tumors. Increased DNA methylation levels within H3K4me1 enriched regions indicates disturbed functions of LSD1 gene in recurrent ependymoma tumors. Combining novel LSD1 inhibitor SYC-836 with radiation (XRT) significantly prolonged animal survival times in PDOX models of recurrent PFA ependymoma. Our PDOX models provide a unique platform for preclinical testing drugs and development of new therapy for pediatric recurrent ependymoma.
Project description:We compared molecular characteristics of primary and recurrent pediatric ependymoma to identify sub-group specific differences. Gene expression profiles were used to identify unique immunobiologic sub-types of posterior fossa pediatric ependymoma.
Project description:YAP1 gene fusions have been observed in a subset of paediatric ependymomas. Here we show that, ectopic expression of active nuclear YAP1 (nlsYAP5SA) in ventricular zone neural progenitor cells using conditionally-induced NEX/NeuroD6-Cre is sufficient to drive brain tumour formation in mice. Neuronal differentiation is inhibited in the hippocampus. Deletion of YAP1’s negative regulators LATS1 and LATS2 kinases in NEX-Cre lineage in double conditional knockout mice also generates similar tumours, which are rescued by deletion of YAP1 and its paralog TAZ. YAP1/TAZ-induced mouse tumours display molecular and ultrastructural characteristics of human ependymoma. RNA sequencing and quantitative proteomics of mouse tumours demonstrate similarities to YAP1-fusion induced supratentorial ependymoma. Finally, we find that transcriptional cofactor HOPX is upregulated in mouse models and in human YAP1-fusion induced ependymoma, supporting their similarity. Our results show that uncontrolled YAP1/TAZ activity in neuronal precursor cells leads to ependymoma-like tumours in mice.
Project description:Background: A methylation-based classification of ependymoma has recently found broad application. However, the diagnostic advantage and implications for treatment decisions remain unclear. Here, we retrospectively evaluate the impact of surgery and radiotherapy on outcome after molecular reclassification of adult intracranial ependymomas. Methods: Tumors diagnosed as intracranial ependymomas from 170 adult patients collected from eight diagnostic institutions were subjected to DNA methylation profiling. Molecular classes, patient characteristics, and treatment were retrospectively correlated with progression-free survival (PFS). Results: The classifier indicated an ependymal tumor in 73.5%, a different tumor entity in 10.6% and non-classifiable tumors in 15.9% of cases, respectively. The most prevalent molecular classes were posterior fossa ependymoma group B (EPN-PFB, 32.9%), posterior fossa subependymoma (PF-SE, 25.9%), and supratentorial ZFTA fusion-positive ependymoma (EPN-ZFTA, 11.2%). With a median follow-up of 60.0 months, the 5- and 10-year-PFS rates were 64.5% and 41.8% for EPN-PFB, 67.4% and 45.2% for PF-SE and 60.3% and 60.3% for EPN-ZFTA. In EPN-PFB, but not in other molecular classes, gross total resection (p=0.009) and postoperative radiotherapy (p=0.007) were significantly associated with improved PFS in multivariable analysis. Histological tumor grading (WHO 2 vs. 3) was not a predictor of prognosis within molecularly defined ependymoma classes. Conclusions: DNA methylation profiling improves diagnostic accuracy and risk stratification in adult intracranial ependymoma. The molecular class of PF-SE is unexpectedly prevalent among adult tumors with ependymoma histology and relapsed as frequently as EPN-PFB, despite the supposed benign nature. Gross total resection and radiotherapy may represent key factors in determining the outcome of EPN-PFB patients.