Temporal and spatial stability of the EM/PM molecular subtypes in adult diffuse glioma.

Detailed characterizations of genomic alterations have not identified subtype-specific vulnerabilities in adult gliomas. Mapping gliomas into developmental programs may uncover new vulnerabilities that are not strictly related to genomic alterations. After identifying conserved gene modules co-expressed with EGFR or PDGFRA (EM or PM), we recently proposed an EM/PM classification scheme for adult gliomas in a histological subtype- and grade-independent manner. By using cohorts of bulk samples, paired primary and recurrent samples, multi-region samples from the same glioma, single-cell RNA-seq samples, and clinical samples, we here demonstrate the temporal and spatial stability of the EM and PM subtypes. The EM and PM subtypes, which progress in a subtype-specific mode, are robustly maintained in paired longitudinal samples. Elevated activities of cell proliferation, genomic instability and microenvironment, rather than subtype switching, mark recurrent gliomas. Within individual gliomas, the EM/PM subtype was preserved across regions and single cells. Malignant cells in the EM and PM gliomas were correlated to neural stem cell and oligodendrocyte progenitor cell compartment, respectively. Thus, while genetic makeup may change during progression and/or within different tumor areas, adult gliomas evolve within a neurodevelopmental framework of the EM and PM molecular subtypes. The dysregulated developmental pathways embedded in these molecular subtypes may contain subtype-specific vulnerabilities.

Elevated signature of a gene module coexpressed with CDC20 marks genomic instability in glioma.

Genomic instability (GI) drives tumor heterogeneity and promotes tumor progression and therapy resistance. However, causative factors underlying GI and means for clinical detection of GI in glioma are inadequately identified. We describe here that elevated expression of a gene module coexpressed with CDC20 (CDC20-M), the activator of the anaphase-promoting complex in the cell cycle, marks GI in glioma. The CDC20-M, containing 139 members involved in cell proliferation, DNA damage response, and chromosome segregation, was found to be consistently coexpressed in glioma transcriptomes. The coexpression of these genes was conserved across multiple species and organ systems, particularly in human neural stem and progenitor cells. CDC20-M expression was not correlated with the morphological subtypes, nor with the recently defined molecular subtypes of glioma. CDC20-M signature was an independent and robust predictor for poorer prognosis in over 1,000 patients from four large databases. Elevated CDC20-M signature enabled the identification of individual glioma samples with severe chromosome instability and mutation burden and of primary glioma cell lines with extensive mitotic errors leading to chromosome mis-segregation. AURKA, a core member of CDC20-M, was amplified in one-third of CDC20-M-high gliomas with gene-dosage-dependent expression. MLN8237, a Food and Drug Administration-approved AURKA inhibitor, selectively killed temozolomide-resistant primary glioma cells in vitro and prolonged the survival of a patient-derived xenograft mouse model with a high-CDC20-M signature. Our findings suggest that application of the CDC20-M signature may permit more selective use of adjuvant therapies for glioma patients and that dysregulated CDC20-M members may provide a therapeutic vulnerability in glioma.

LINC00261 Is an Epigenetically Regulated Tumor Suppressor Essential for Activation of the DNA Damage Response.

Lung cancer is the leading cause of cancer-related death in the United States. Long noncoding RNAs (lncRNA) are a class of regulatory molecules whose role in lung carcinogenesis is poorly understood. In this study, we profiled lncRNA expression in lung adenocarcinoma (LUAD) cell lines, compared their expression with that of purified alveolar epithelial type II cells (the purported cell of origin for LUAD), cross-referenced these with lncRNAs altered in the primary human tumors, and interrogated for lncRNAs whose expression correlated with patient survival. We identified LINC00261, a lncRNA with unknown function in LUAD, adjacent to the pioneering transcription factor FOXA2. Loss of LINC00261 was observed in multiple tumor types, including liver, breast, and gastric cancer. Reintroduction of LINC00261 into human LUAD cell lines inhibited cell migration and slowed proliferation by inducing G2-M cell-cycle arrest, while upregulating DNA damage pathway genes and inducing phosphorylation-mediated activation of components of the DNA damage pathway. FOXA2 was able to induce LINC00261 expression, and the entire locus underwent hypermethylation in LUAD, leading to loss of expression. We have thus identified an epigenetically deregulated lncRNA, whose loss of expression in LUAD promotes the malignant phenotype and blocks activation of the DNA damage machinery, predisposing lung cells to cancer development. SIGNIFICANCE: These findings identify LINC00261 as a tumor suppressor that blocks cellular proliferation by activating the DNA damage response and suggest that epigenetic therapy to inhibit DNA methylation may enhance treatment of LUAD. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/79/12/3050/F1.large.jpg.See related commentary by Davalos and Esteller, p. 3028.