Glioblastomas within the Subventricular Zone Are Region-Specific Enriched for Mesenchymal Transition Markers: An Intratumoral Gene Expression Analysis

Stem the blood flow: beneficial impact of bevacizumab on survival of subventricular zone glioblastoma patients

PURPOSE

Angiogenesis is a crucial step in tumorigenesis of glioblastoma (GBM). Bevacizumab, an anti-vascular endothelial growth factor drug, is approved for second-line therapy for GBM. Glioma stem cells, presumably the cell of origin of GBM, take an active role in angiogenesis. The subventricular zone (SVZ) is the brain's largest reservoir of neural stem cells, and GBM near this region (SVZ GBM) is associated with a poor prognosis. This study aims to evaluate the potential impact of second-line bevacizumab treatment on survival in patients with SVZ GBM.

METHODS

The electronic medical records of adult patients with newly diagnosed SVZ GDM under treated between 1/2011 and 12/2021 were retrospectively reviewed. Clinical, surgical, radiological, and outcome parameters were compared between patients treated with bevacizumab after first relapse to patients without such treatment.

RESULTS

The cohort included 67 patients. 45 (67.1%) were treated with bevacizumab after the first relapse while 22 (32.9%) were not. The only statistically significant difference between groups was the rate of re-surgery, which was higher in the non-bevacizumab group (40.9% vs. 15.6%; p = 0.023), indicating that the groups were quite homogenous. In general, bevacizumab as a second-line treatment did not affect OS in SVZ GBM cases. However, it significantly prolongs survival time from 1st relapse by an average of more than 4 months, including after adjustment to re-surgery variable (HR = 0.57, 95% CI 0.34-0.94, p = 0.028 and HR = 0.57, 95%CI = 0.34-0.97, PV = 0.038; respectively). Furthermore, when adjusting to time from diagnosis to 1st relapse, bevacizumab treatment was also associated with prolonged OS (HR = 0.58; p = 0.043). In a subgroup analysis, comparing patients treated with both re-surgery and bevacizumab to patients treated in any other way, patients with the combined treatment had the longest mean OS of the entire cohort (22.16 ± 7.81 m vs. 13.60 ± 6.86, p = 0.049; HR = 0.361 95%CI 0.108-1.209, p = 0.085).

CONCLUSIONS

The use of bevacizumab as a second-line therapy in SVZ GBM cases may positively affect survival after relapse, even when given as a monotherapy. Additionally, in certain yet-to-be-identified sub-populations, bevacizumab may even extend overall survival. Further research is required to accurately identify SVZ GBM patients who would benefit most from anti-angiogenic therapy.

Development of Zika Virus E Variants for Pseudotyping Retroviral Vectors Targeting Glioblastoma Cells

A fundamental idea for targeting glioblastoma cells is to exploit the neurotropic properties of Zika virus (ZIKV) through its two outer envelope proteins, prM and E. This study aimed to develop envelope glycoproteins for pseudotyping retroviral vectors that can be used for efficient tumor cell infection. Firstly, the retroviral vector pNLlucAM was packaged using wild-type ZIKV E to generate an E-HIVluc pseudotype. E-HIVluc infection rates for tumor cells were higher than those of normal prME pseudotyped particles and the traditionally used vesicular stomatitis virus G (VSV-G) pseudotypes, indicating that protein E alone was sufficient for the formation of infectious pseudotyped particles. Secondly, two envelope chimeras, E41.1 and E41.2, with the E wild-type transmembrane domain replaced by the gp41 transmembrane and cytoplasmic domains, were constructed; pNLlucAM or pNLgfpAM packaged with E41.1 or E41.2 constructs showed infectivity for tumor cells, with the highest rates observed for E41.2. This envelope construct can be used not only as a tool to further develop oncolytic pseudotyped viruses for therapy, but also as a new research tool to study changes in tumor cells after the transfer of genes that might have therapeutic potential.

Dissecting Intra-tumor Heterogeneity in the Glioblastoma Microenvironment Using Fluorescence-Guided Multiple Sampling

The treatment of the most aggressive primary brain tumor in adults, glioblastoma (GBM), is challenging due to its heterogeneous nature, invasive potential, and poor response to chemo- and radiotherapy. As a result, GBM inevitably recurs and only a few patients survive 5 years post-diagnosis. GBM is characterized by extensive phenotypic and genetic heterogeneity, creating a diversified genetic landscape and a network of biological interactions between subclones, ultimately promoting tumor growth and therapeutic resistance. This includes spatial and temporal changes in the tumor microenvironment, which influence cellular and molecular programs in GBM and therapeutic responses. However, dissecting phenotypic and genetic heterogeneity at spatial and temporal levels is extremely challenging, and the dynamics of the GBM microenvironment cannot be captured by analysis of a single tumor sample. In this review, we discuss the current research on GBM heterogeneity, in particular, the utility and potential applications of fluorescence-guided multiple sampling to dissect phenotypic and genetic intra-tumor heterogeneity in the GBM microenvironment, identify tumor and non-tumor cell interactions and novel therapeutic targets in areas that are key for tumor growth and recurrence, and improve the molecular classification of GBM.

Alterations in EGFR and PDGFRA are associated with the localization of contrast-enhancing lesions in glioblastoma

Background

Glioblastoma (GBM) is a malignant brain tumor, with radiological and genetic heterogeneity. We examined the association between radiological characteristics and driver gene alterations.

Methods

We analyzed the driver genes of 124 patients with IDH wild-type GBM with contrast enhancement using magnetic resonance imaging. We used a next-generation sequencing panel to identify mutations in driver genes and matched them with radiological information. Contrast-enhancing lesion localization of GBMs was classified into 4 groups based on their relationship with the subventricular zone (SVZ) and cortex (Ctx).

Results

The cohort included 69 men (55.6%) and 55 women (44.4%) with a mean age of 66.4 ± 13.3 years. EGFR and PDGFRA alterations were detected in 28.2% and 22.6% of the patients, respectively. Contrast-enhancing lesion touching both the SVZ and Ctx was excluded because it was difficult to determine whether it originated from the SVZ or Ctx. Contrast-enhancing lesions touching the SVZ but not the Ctx had significantly worse overall survival than non-SVZ lesions (441 days vs. 897 days, P = .002). GBM touching only the Ctx had a better prognosis (901 days vs. 473 days, P < .001) than non-Ctx lesions and was associated with EGFR alteration (39.4% vs. 13.2%, P = .015). Multiple contrast lesions were predominant in PDGFRA alteration and RB1-wild type (P = .036 and P = .031, respectively).

Conclusions

EGFR alteration was associated with cortical lesions. And PDGFRA alteration correlated with multiple lesions. Our results suggest that clarifying the association between driver genes and tumor localization may be useful in clinical practice, including prognosis prediction.

Disproportion in Pericyte/Endothelial Cell Proliferation and Mechanisms of Intussusceptive Angiogenesis Participate in Bizarre Vessel Formation in Glioblastoma

Glioblastoma (GBM) is the most malignant tumor in the brain. In addition to the vascular pattern with thin-walled vessels and findings of sprouting angiogenesis, GBM presents a bizarre microvasculature (BM) formed by vascular clusters, vascular garlands, and glomeruloid bodies. The mechanisms in BM morphogenesis are not well known. Our objective was to assess the role of pericyte/endothelial proliferation and intussusceptive angiogenic mechanisms in the formation of the BM. For this purpose, we studied specimens of 66 GBM cases using immunochemistry and confocal microscopy. In the BM, the results showed (a) transitional forms between the BM patterns, mostly with prominent pericytes covering all the abluminal endothelial cell (EC) surface of the vessels, (b) a proliferation index high in the prominent pericytes and low in ECs (47.85 times higher in pericytes than in ECs), (c) intravascular pillars (hallmark of intussusceptive angiogenesis) formed by transcapillary interendothelial bridges, endothelial contacts of opposite vessel walls, and vessel loops, and (d) the persistence of these findings in complex glomeruloid bodies. In conclusion, disproportion in pericyte/EC proliferation and mechanisms of intussusceptive angiogenesis participate in BM formation. The contributions have morphogenic and clinical interest since pericytes and intussusceptive angiogenesis can condition antiangiogenic therapy in GBM.