BackgroundTumor heterogeneity is a major obstacle for finding effective treatment of Glioblastoma (GBM). Based on global expression analysis, GBM can be classified into distinct subtypes: Proneural, Neural, Classical and Mesenchymal. The signatures of these different tumor subtypes may reflect the phenotypes of cells giving rise to them. However, the experimental evidence connecting any specific subtype of GBM to particular cells of origin is lacking. In addition, it is unclear how different genetic alterations interact with cells of origin in determining tumor heterogeneity. This issue cannot be addressed by studying end-stage human tumors.Methodology/Principal FindingsTo address this issue, we used retroviruses to deliver transforming genetic lesions to glial progenitors in adult mouse brain. We compared the resulting tumors to human GBM. We found that different initiating genetic lesions gave rise to tumors with different growth rates. However all mouse tumors closely resembled the human Proneural GBM. Comparative analysis of these mouse tumors allowed us to identify a set of genes whose expression in humans with Proneural GBM correlates with survival.Conclusions/SignificanceThis study offers insights into the relationship between adult glial progenitors and Proneural GBM, and allows us to identify molecular alterations that lead to more aggressive tumor growth. In addition, we present a new preclinical model that can be used to test treatments directed at a specific type of GBM in future studies.

Indolent T-cell lymphoproliferative disorders of the gastrointestinal tract are rare clonal T-cell diseases that more commonly occur in the intestines and have a protracted clinical course. Different immunophenotypic subsets have been described, but the molecular pathogenesis and cell of origin of these lymphocytic proliferations is poorly understood. Hence, we performed targeted next-generation sequencing and comprehensive immunophenotypic analysis of 10 indolent T-cell lymphoproliferative disorders of the gastrointestinal tract, which comprised CD4+ (n=4), CD8+ (n=4), CD4+/CD8+ (n=1) and CD4-/CD8-(n=1) cases. Genetic alterations, including recurrent mutations and novel rearrangements, were identified in 8/10 (80%) lymphoproliferative disorders. The CD4+, CD4+/CD8+, and CD4-/CD8-cases harbored frequent alterations of the JAK-STAT pathway genes (5/6, 82%); STAT3 mutations (n=3), SOCS1 deletion (n=1) and STAT3-JAK2 rearrangement (n=1), and 4/6 (67%) had concomitant mutations in epigenetic modifier genes (TET2, DNMT3A, KMT2D). Conversely, 2/4 (50%) of the CD8+ cases exhibited structural alterations involving the 3' untranslated region of the IL2 gene. Longitudinal genetic analysis revealed stable mutational profiles in 4/5 (80%) cases and acquisition of mutations in one case were a harbinger of disease transformation. The CD4+ and CD4+/CD8+ lymphoproliferative disorders displayed heterogeneous Th1 (T-bet+), Th2 (GATA3+) or hybrid Th1/Th2 (T-bet+/GATA3+) profiles, while the majority of CD8+ disorders and the CD4-/CD8-disease showed a type-2 polarized (GATA3+) effector T-cell (Tc2) phenotype. Additionally, CD103 expression was noted in 2/4 CD8+ cases. Our findings provide insights into the pathogenetic bases of indolent T-cell lymphoproliferative disorders of the 4 gastrointestinal tract and confirm the heterogeneous nature of these diseases.Detection of shared and distinct genetic alterations of the JAK-STAT pathway in certain immunophenotypic subsets warrants further mechanistic studies to determine whether therapeutic targeting of this signaling cascade is efficacious for a proportion of patients with these recalcitrant diseases.