Glioblastoma cells secrete extra-cellular vesicles (EVs) containing microRNAs (miRNAs). Analysis of these EV miRNAs in the bio-fluids of afflicted patients represents a potential platform for ...biomarker development. However, the analytic algorithm for quantitative assessment of EV miRNA remains under-developed. Here, we demonstrate that the reference transcripts commonly used for quantitative PCR (including GAPDH, 18S rRNA, and hsa-miR-103) were unreliable for assessing EV miRNA. In this context, we quantitated EV miRNA in absolute terms and normalized this value to the input EV number. Using this method, we examined the abundance of miR-21, a highly over-expressed miRNA in glioblastomas, in EVs. In a panel of glioblastoma cell lines, the cellular levels of miR-21 correlated with EV miR-21 levels (p<0.05), suggesting that glioblastoma cells actively secrete EVs containing miR-21. Consistent with this hypothesis, the CSF EV miR-21 levels of glioblastoma patients (n=13) were, on average, ten-fold higher than levels in EVs isolated from the CSF of non-oncologic patients (n=13, p<0.001). Notably, none of the glioblastoma CSF harbored EV miR-21 level below 0.25 copies per EV in this cohort. Using this cut-off value, we were able to prospectively distinguish CSF derived from glioblastoma and non-oncologic patients in an independent cohort of twenty-nine patients (Sensitivity=87%; Specificity=93%; AUC=0.91, p<0.01). Our results suggest that CSF EV miRNA analysis of miR-21 may serve as a platform for glioblastoma biomarker development.
Diffusion Weighted Imaging (DWI), which is based on Echo Planar Imaging (EPI) protocols, is becoming increasingly important for neurosurgical applications. However, its use in this context is limited ...in part by significant spatial distortion inherent to EPI.
We evaluated an efficient algorithm for EPI distortion correction (EPIC) across 814 DWI scans from 250 brain tumor patients and quantified the magnitude of geometric distortion for whole brain and multiple brain regions.
Evaluation of the algorithm's performance revealed significantly higher mutual information between T1-weighted pre-contrast images and corrected b = 0 images than the uncorrected b = 0 images (p < 0.001). The distortion magnitude across all voxels revealed a median EPI distortion effect of 2.1 mm, ranging from 1.2 mm to 5.9 mm, the 5th and 95th percentile, respectively. Regions adjacent to bone-air interfaces, such as the orbitofrontal cortex, temporal poles, and brain stem, were the regions most severely affected by DWI distortion.
Using EPIC to estimate the degree of distortion in 814 DWI brain tumor images enabled the creation of a topographic atlas of DWI distortion across the brain. The degree of displacement of tumors boundaries in uncorrected images is severe but can be corrected for using EPIC. Our results support the use of distortion correction to ensure accurate and careful application of DWI to neurosurgical practice.
Tumor-released RNA may mediate intercellular communication and serve as biomarkers. Here we develop a protocol enabling quantitative, minimally biased analysis of extracellular RNAs (exRNAs) ...associated with microvesicles, exosomes (collectively called EVs), and ribonucleoproteins (RNPs). The exRNA complexes isolated from patient-derived glioma stem-like cultures exhibit distinct compositions, with microvesicles most closely reflecting cellular transcriptome. exRNA is enriched in small ncRNAs, such as miRNAs in exosomes, and precisely processed tRNA and Y RNA fragments in EVs and exRNPs. EV-enclosed mRNAs are mostly fragmented, and UTRs enriched; nevertheless, some full-length mRNAs are present. Overall, there is less than one copy of non-rRNA per EV. Our results suggest that massive EV/exRNA uptake would be required to ensure functional impact of transferred RNA on brain recipient cells and predict the most impactful miRNAs in such conditions. This study also provides a catalog of diverse exRNAs useful for biomarker discovery and validates its feasibility on cerebrospinal fluid.
Abstract
TARGET POPULATION
These recommendations apply to adult patients newly diagnosed with multiple (more than 1) brain metastases.
QUESTION 1
In what circumstances should whole brain radiation ...therapy be recommended to improve tumor control and survival in patients with multiple brain metastases?
RECOMMENDATION
Level 2: It is recommended that whole brain radiation therapy can be added to stereotactic radiosurgery to improve local and distant control keeping in mind the potential for worsened neurocognitive outcomes and that there is unlikely to be a significant impact on overall survival.
QUESTION 2
In what circumstances should stereotactic radiosurgery be recommended to improve tumor control and survival in patients with multiple brain metastases?
RECOMMENDATIONS
Level 1: In patients with 2 to 3 brain metastases not amenable to surgery, the addition of stereotactic radiosurgery to whole brain radiation therapy is not recommended to improve survival beyond that obtained with whole brain radiation therapy alone.
Level 3: The use of stereotactic radiosurgery alone is recommended to improve median overall survival for patients with more than 4 metastases having a cumulative volume < 7 cc.
QUESTION 3
In what circumstances should surgery be recommended to improve tumor control and survival in patients with multiple brain metastases?
RECOMMENDATION
Level 3: In patients with multiple brain metastases, tumor resection is recommended in patients with lesions inducing symptoms from mass effect that can be reached without inducing new neurological deficit and who have control of their cancer outside the nervous system.
The full guideline can be found at https://www.cns.org/guidelines/guidelines-treatment-adults-metastatic-brain-tumors/chapter_6.
Glioblastoma is the most common form of adult brain cancer and remains one of the deadliest of human cancers. The current standard-of-care involves maximal tumor resection followed by treatment with ...concurrent radiation therapy and the chemotherapy temozolomide. Recurrence after this therapy is nearly universal within 2 years of diagnosis. Notably, >80% of recurrence is found in the region adjacent to the resection cavity. The need for improved local control in this region, thus remains unmet. The FDA approval of 5-aminolevulinic acid (5-ALA) for fluorescence guided glioblastoma resection renewed interests in leveraging this agent as a means to administer photodynamic therapy (PDT). Here we review the general principles of PDT as well as the available literature on PDT as a glioblastoma therapeutic platform.
The complex interaction between glioblastoma and its microenvironment has been recognized for decades. Among various immune profiles, the major population is tumor-associated macrophage, with ...microglia as its localized homolog. The present definition of such myeloid cells is based on a series of cell markers. These good sentinel cells experience significant changes, facilitating glioblastoma development and protecting it from therapeutic treatments. Huge, complicated mechanisms are involved during the overall processes. A lot of effort has been dedicated to crack the mysterious codes in macrophage/microglia recruiting, activating, reprogramming, and functioning. We have made our path. With more and more key factors identified, a lot of new therapeutic methods could be explored to break the ominous loop, to enhance tumor sensitivity to treatments, and to improve the prognosis of glioblastoma patients. However, it might be a synergistic system rather than a series of clear, stepwise events. There are still significant challenges before the light of truth can shine onto the field. Here, we summarize recent advances in this field, reviewing the path we have been on and where we are now.
Recent studies suggest both normal and cancerous cells secrete vesicles into the extracellular space. These extracellular vesicles (EVs) contain materials that mirror the genetic and proteomic ...content of the secreting cell. The identification of cancer-specific material in EVs isolated from the biofluids (e.g., serum, cerebrospinal fluid, urine) of cancer patients suggests EVs as an attractive platform for biomarker development. It is important to recognize that the EVs derived from clinical samples are likely highly heterogeneous in make-up and arose from diverse sets of biologic processes. This article aims to review the biologic processes that give rise to various types of EVs, including exosomes, microvesicles, retrovirus like particles, and apoptotic bodies. Clinical pertinence of these EVs to neuro-oncology will also be discussed.
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