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Tumor type and cell type-specific gene expression alterations in diverse pediatric central nervous system tumors identified using single nuclei RNA-seq

ABSTRACT: Central nervous system (CNS) tumors are the leading cause of pediatric cancer death, and these patients have an increased risk for developing secondary neoplasms. Due to the low prevalence of pediatric CNS tumors, major advances in targeted therapies have been lagging compared to other adult tumors. We collected single nuclei RNA-seq data from 35 pediatric CNS tumors and three non-tumoral pediatric brain tissues (84,700 nuclei) and characterized tumor heterogeneity and transcriptomic alterations. We distinguished cell subpopulations associated with specific tumor types including radial glial cells in ependymomas and oligodendrocyte precursor cells in astrocytomas. In tumors, we observed pathways important in neural stem cell-like populations, a cell type previously associated with therapy resistance. Lastly, we identified transcriptomic alterations among pediatric CNS tumor types compared to non-tumor tissues, while accounting for cell type effects on gene expression. Our results suggest potential tumor type and cell type-specific targets for pediatric CNS tumor treatment.

ORGANISM(S): Homo sapiens

PROVIDER: GSE241396 | GEO | 2023/12/31

REPOSITORIES: GEO

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Project description:Ependymomas are neuroepithelial tumors of the central nervous system (CNS), presenting in both adults and children but accounting for almost 10% of all pediatric CNS tumors and up to 30% of CNS tumors in children under 3 years (Bouffet et al., 2009; McGuire et al., 2009; Rodriguez et al., 2009). In children, most ependymomas arise in the posterior fossa, while most adult ependymomas present around the lower spinal cord and spinal nerve roots. Ependymomas display a wide range of morphological features, and several variants are listed in the World Health Organization (WHO) classification (Ellison et al., 2016). These variants are assigned to three WHO grades (I-III), but the clinical utility of this classification is acknowledged to be limited (Ellison et al., 2011). An increasing understanding of the genomic landscape of ependymoma and the discovery of distinct molecular groups by DNA methylation or gene expression profiling have begun to refine approaches to disease classification and prognostication, but have yet to be translated into clinical routine (Hoffman et al., 2014; Mack et al., 2014; Pajtler et al., 2017; Pajtler et al., 2015; Parker et al., 2014; Wani et al., 2012; Witt et al., 2011). Our comprehensive study of DNA methylation profiling across the entire disease demonstrated three molecular groups for each major anatomic compartment: supratentorial (ST), posterior fossa (PF), and spinal (SP) (Pajtler et al., 2015). In the ST compartment, two molecular groups (ST-EPN-RELA and ST-EPN-YAP1) align with tumors harboring specific genetic alterations, RELA and YAP1 fusion genes, which were initially discovered in a whole genome sequencing study (Parker et al., 2014). Among PF ependymomas, two of three molecular groups, PFA (PF-EPN-A) and PFB (PF-EPN-B), account for nearly all tumors; PF-SE tumors are rare, generally showing the morphology of a subependymoma (Pajtler et al., 2015). PFA tumors are found mainly in infants and young children (median age ≈ 3yrs) and have a relatively poor outcome, while PFB tumors are generally found in young adults (median age ≈ 30yrs) and are associated with a better prognosis (Pajtler et al., 2015; Witt et al., 2011). PFA tumors show few copy number alterations (CNAs), while PFB tumors harbor multiple CNAs that tend to affect entire chromosomes. While recurrent structural variants (SVs) are found in ST ependymomas, recurrent SVs or other mutations, such as single nucleotide variants (SNVs) and insertions or deletions (indels), have not been identified in PF ependymomas to date (Mack et al., 2014; Parker et al., 2014).

Project description:Genomic technologies have unmasked molecularly distinct subgroups among tumors of the same histological type; but understanding the biologic basis of these subgroups has proved difficult since their defining alterations are often numerous, and the cellular origins of most cancers remain unknown. We sought to decipher complex genomic data sets by matching the genetic alterations contained within these, with candidate cells of origin, to generate accurate disease models. Using an integrated genomic analysis we first identified subgroups of human ependymoma: a form of neural tumor that arises throughout the central nervous system (CNS). Validated alterations included amplifications and homozygous deletions of genes not yet implicated in ependymoma. Matching the transcriptomes of human ependymoma subgroups to those of distinct types of mouse radial glia (RG)—neural stem cells (NSCs) that we identified previously to be a candidate cell of origin of ependymoma - allowed us to select RG types most likely to represent cells of origin of disease subgroups. The transcriptome of human cerebral ependymomas that amplify EPHB2 and delete INK4A/ARF matched most closely that of embryonic cerebral Ink4a/Arf-/- RG: remarkably, activation of EphB2 signaling in this RG type, but not others, generated highly penetrant ependymomas that modeled accurately the histology and transcriptome of one human cerebral tumor subgroup (subgroup ‘D’). Further comparative genomic analysis revealed selective alterations in the copy number and expression of genes that regulate neural differentiation, particularly synaptogenesis, in both mouse and human subgroup ‘D’ ependymomas; pinpointing this pathway as a previously unknown target of ependymoma tumorigenesis. Our data demonstrate the power of comparative genomics to sift complex genetic data sets to identify key molecular alterations in cancer subgroups. [human mRNA] samples: 83 human ependynoma primary tumors were collected and clustered into distinct classes by unsupervised methods and then compared to mouse model data. [mouse mRNA] samples: 192 mouse tumors and cell lines were collected and clustered into distinct classes by unsupervised methods and then compared to human tumors. [human miRNA] samples: 64 human ependynoma primary tumors were collected and miRNA expression was assesed and compared to genomic expression

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Tumor type and cell type-specific gene expression alterations in diverse pediatric central nervous system tumors identified using single nuclei RNA-seq

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