Ivy Glioblastoma Atlas Project

http://glioblastoma.alleninstitute.org/

The Ivy Glioblastoma Atlas Project is a foundational resource for exploring the anatomic and genetic basis of glioblastoma at the cellular and molecular levels.

It is a collaborative partnership between the Ben and Catherine Ivy Foundation, the Allen Institute for Brain Science, and the Ben and Catherine Ivy Center for Advanced Brain Tumor Treatment.

This project was supported by the Ben and Catherine Ivy Foundation (PIs: Ralph Puchalski, PhD, Allen Institute for Brain Science and Greg Foltz, MD, Swedish Neuroscience Institute).

Glioblastoma multiforme (GBM), an aggressive brain tumor, is characterized histologically by the presence of a necrotic center surrounded by so-calledpseudopalisading cells. Pseudopalisading necrosis has long been used as a prognostic feature. However, the underlying molecular mechanism regulating the progression of GBMs remains unclear.

Wang et al., hypothesized that the gene expression profilings of individual cancers, specifically necrosis-related genes, would provide objective information that would allow for the creation of a prognostic index. Gene expression profiles of necrotic and nonnecrotic areas were obtained from the Ivy Glioblastoma Atlas Project (IVY GAP) database to explore the differentially expressed genes.A robust signature of seven genes was identified as a predictor for glioblastoma and low-grade glioma (GBM/LGG) in patients from The Cancer Genome Atlas (TCGA) cohort. This set of genes was able to stratify GBM/LGG and GBM patients into high-risk and low-risk groups in the training set as well as the validation set. The TCGA, Repository for Molecular Brain Neoplasia Data (Rembrandt), and GSE16011 databases were then used to validate the expression level of these seven genes in GBMs and LGGs. Finally, the differentially expressed genes (DEGs) in the high-risk and low-risk groups were subjected to gene ontology enrichment, Kyoto Encyclopedia of Genes and Genomes pathway, and gene set enrichment analyses, and they revealed that these DEGs were associated with immune and inflammatory responses. In conclusion, the study identified a novel seven-gene signature that may guide the prognostic prediction and development of therapeutic applications ¹⁾.

The Cancer Genome Atlas and Ivy Glioblastoma Atlas Project data demonstrated that IL-8 transcript expression is negatively correlated with GBM patient survival (p = 0.001) and positively correlated with that of genes associated with the GIC phenotypes, such as KLF4, c-Myc, and HIF2α (p < 0.001). Immunohistochemical analysis of patient samples demonstrated elevated IL-8 expression in about 60% of recurrent GBM tumors relative to matched primary tumors and this expression also positively correlates with time to recurrence. Exposure to IL-8 significantly enhanced the self-renewing capacity of PDX GBM (average threefold, p < 0.0005), as well as increasing the expression of GIC markers in the CXCR2 population. Furthermore, IL-8 knockdown significantly delayed PDX GBM tumor growth in vivo (p < 0.0005). Finally, guided by in silico analysis of TCGA data, we examined the effect of therapy-induced IL-8 expression on the epigenomic landscape of GBM cells and observed increased trimethylation of H3K9 and H3K27. Our results show that autocrine IL-8 alters cellular plasticity and mediates alterations in histone status. These findings suggest that IL-8 signaling participates in regulating GBM adaptation to therapeutic stress and therefore represents a promising target for combination with conventional chemotherapy in order to limit GBM recurrence ²⁾.

Immunohistochemical staining and the RNA-seq (sequencing) data from the IVY Glioblastoma Atlas Project showed FGF13 expression in glioma cells in the invasive edges of tumor specimens. Also, the intracellular distribution was mainly in the cytoplasm of tumor cells and colocalized with tubulin. Overexpression of FGF13 stabilized tubulin dynamics in vitro and knockdown of FGF13 decreased glioma invasion both in vitro and in vivo and prolonged overall survival of several xenograft models. FGF13 was negatively regulated by hypoxic condition. Silencing of FGF13 also decreased in vivo bevacizumab-induced glioma invasion. In conclusion, FGF13 regulated glioma cell invasion and bevacizumab-induced glioma invasion, and could be a novel target for glioma treatment ³⁾.

In support of potential clinical relevance, expression of selected GSC-enriched ion channels evaluated in human glioblastoma databases of The Cancer Genome Atlas and Ivy Glioblastoma Atlas Project correlated with patient survival times. Finally, genetic knockdown as well as pharmacological inhibition of individual or classes of GSC-enriched ion channels constrained growth of GSCs compared to normal neural stem cells. This first-in-kind global examination characterizes ion channels enriched in GSCs and explores their potential clinical relevance to glioblastoma molecular subtypes, gene mutations, survival outcomes, regional tumor expression, and experimental responses to loss-of-function. Together, the data support the potential biological and therapeutic impact of ion channels on GSC malignancy and provide strong rationale for further examination of their mechanistic and therapeutic importance ⁴⁾.