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Background Glioblastoma (GBM) exhibits profound intratumoral genetic heterogeneity. Each tumor comprises multiple genetically distinct clonal populations with different therapeutic sensitivities. This has implications for targeted therapy and genetically informed paradigms. Contrast-enhanced (CE)-MRI and conventional sampling techniques have failed to resolve this heterogeneity, particularly for nonenhancing tumor populations. This study explores the feasibility of using multiparametric MRI and texture analysis to characterize regional genetic heterogeneity throughout MRI-enhancing and nonenhancing tumor segments. Methods We collected multiple image-guided biopsies from primary GBM patients throughout regions of enhancement (ENH) and nonenhancing parenchyma (so called brain-around-tumor, [BAT]). For each biopsy, we analyzed DNA copy number variants for core GBM driver genes reported by The Cancer Genome Atlas. We co-registered biopsy locations with MRI and texture maps to correlate regional genetic status with spatially matched imaging measurements. We also built multivariate predictive decision-tree models for each GBM driver gene and validated accuracies using leave-one-out-cross-validation (LOOCV). Results We collected 48 biopsies (13 tumors) and identified significant imaging correlations (univariate analysis) for 6 driver genes: EGFR, PDGFRA, PTEN, CDKN2A, RB1, and TP53. Predictive model accuracies (on LOOCV) varied by driver gene of interest. Highest accuracies were observed for PDGFRA (77.1%), EGFR (75%), CDKN2A (87.5%), and RB1 (87.5%), while lowest accuracy was observed in TP53 (37.5%). Models for 4 driver genes (EGFR, RB1, CDKN2A, and PTEN) showed higher accuracy in BAT samples (n = 16) compared with those from ENH segments (n = 32). Conclusion MRI and texture analysis can help characterize regional genetic heterogeneity, which offers potential diagnostic value under the paradigm of individualized oncology.

Glioblastoma (GBM) is the most common and deadly malignancy of the central nervous system in adults with a median survival of about 15 months after diagnosis. Its aggressive and highly infiltrative nature renders the current standard treatment of maximal surgical resection, radiation, and chemotherapy relatively ineffective. Identifying the molecular events that regulate GBM migration/invasion is required to develop more effective therapeutic regimens to treat GBM. Expression of TROY, an orphan receptor of the TNFR superfamily, increases with increasing glial tumor grade, inversely correlates with patient survival, stimulates GBM cell invasion in vitro and in vivo, and increases resistance to temozolomide and radiation therapy. Conversely, silencing TROY expression inhibits GBM cell invasion, increases sensitivity to temozolomide, and prolongs survival in a preclinical intracranial xenograft model. Thus, the TROY signaling pathway represents an attractive therapeutic target. We previously reported that increased TROY expression strongly activates NF-kB. We have identified for the first time that TROY forms a unique signaling complex with JAK1. Interaction with TROY stimulates phosphorylation of JAK1 and significantly increases the activation of STAT3. TROY specifically associates with JAK1 as it does not associate with other JAK family members. Co-immunoprecipitation analysis demonstrated that TROY interacts with JAK1 through its cytoplasmic domain as a TROY variant without its extracellular domain associates with JAK1 while a TROY variant without a cytoplasmic domain fails to bind JAK1. Luciferase reporter assay confirmed that full length TROY or a variant lacking the extracellular domain are able to induce STAT3 activation, but not a TROY variant lacking the cytoplasmic domain. Pharmacological inhibition of JAK1 by the FDA approved inhibitor ruxolitinib or knockdown of JAK1 by siRNAs significantly inhibited TROY-induced STAT3 activation and GBM cell migration. Together, our data indicate that the TROY-JAK1 complex represents an unappreciated therapeutic target to inhibit glioma invasion and decrease therapeutic resistance.

Glioblastoma (GBM) is among the most genetically heterogeneous, treatment resistant, and lethal of all human cancers. A significant hurdle to effective treatment of GBM is the aggressive invasion of tumor cells into surrounding healthy brain tissue that invariably leads to tumor recurrence, brain injury, and patient death. These invasive cells preclude complete surgical resection and exhibit marked resistance to chemotherapeutics. As invasion is a universal property of GBM, studies focused on the invasive cell population and on the development of therapies that target them are greatly needed in order to significantly improve the survival of GBM patients. We have previously showed that SGEF (ARHGEF26), a RhoG-specific guanine exchange factor is overexpressed in high-grade brain tumors and correlates with poor patient survival. Here we report that SGEF is critical for promoting GBM invasion and survival by modulation of the DNA repair mechanism. Upon TMZ treatment, SGEF accumulated in the nucleus and mediated BRCA1 binding to γH2AX, and knockdown of SGEF expression in GBM cells impaired the phosphorylation of BRCA1 and CHK1. In addition, GBM cells with stable knockdown of SGEF expression showed enhanced susceptibility to TMZ induced cell death. Re-expression of SGEF in these cells rescued BRCA1 phosphorylation and glioma cell resistance to TMZ. Thus, our data showed an important role for SGEF in mediating GBM cell survival.

Glioblastoma (GB) is among the most genetically heterogeneous, treatment resistant, and lethal of all human cancers. A significant hurdle to effective treatment of GB is the aggressive invasion of tumor cells into surrounding healthy brain tissue that invariably leads to tumor recurrence, brain injury, and patient death. Median survival following recurrence drops to approximately 8 months and overall 2 year survival rates have remained relatively unchanged for more than 25 years. There is presently a limited amount of information available regarding the biological properties of invasive rim cells. As invasion is a universal property of GB, studies focused on this cell population and on the development of therapies that target them are sorely needed in order to significantly improve the survival of GB patients. Comprehensive genomic analyses of GB core specimens and invasive rim components, have helped identify genes and signaling pathways that are frequently altered in GB and brain-invaded regions. Through gene expression analysis on GB patient tumors harboring a wide set of genetic aberrations, we have reported that expression of Fn14, a type I transmembrane receptor of the TNFR super family, is low in normal brain tissue but is highly expressed by infiltrating glioma cells. Increased Fn14 mediated signaling increases GB cell migration/invasion and survival in vitro while knockdown of Fn14 expression increases sensitivity to temozolomide in an intracranial xenograft model, which substantiates its potential as a target to inhibit GB cell invasion and decrease resistance. Amplification and overexpression of the epidermal growth factor (EGFR) is the most common genetic alteration observed in GB. Greater than half of GB tumors with amplification of EGFR also exhibit rearrangements in the EGFR gene resulting in expression of mutated forms of the EGFR, the most common of which is EGFRvIII. EGFR and EGFRvIII cooperate to promote tumor progression and invasion, in part, through activation of the Stat3-signaling pathway; however, the signaling mechanism(s) by which EGFRvIII induces GB invasion and survival differs from EGFR. Preliminary investigation into the mechanistic basis of Fn14 signaling in GB cells revealed that EGFRvIII induces expression of Fn14 and that EGFRvIII mediated GB cell invasion is dependent upon Fn14 expression. EGFRvIII-mediated induction of Fn14 expression is dependent upon Stat5 and requires activation of Src, whereas EGFR regulation of Fn14 is also dependent upon MEK/ERK-Stat3 activation. In addition, Stat5 activation by IL2 is required to induce Fn14 expression, indicating involvement of the microenvironment. Notably, treatment of EGFRvIII expressing GB cells with the Stat5 inhibitor pimozide blocked Stat5 phosphorylation and Fn14 expression positioning Stat5 as a therapeutic target for treatment of invasive GB cells.