Recent Advances in Liquid Biopsy of Brain Cancers

Development of an organ-on-chip model for the detection of volatile organic compounds as potential biomarkers of tumour progression

Early detection of tumours remains a significant challenge due to their invasive nature and the limitations of current monitoring techniques. Liquid biopsies have emerged as a minimally invasive diagnostic approach, wherein volatile organic compounds (VOCs) show potential as compelling candidates. However, distinguishing tumour-specific VOCs is difficult due to the presence of gases from non-tumour tissues and environmental factors. Therefore, it is essential to develop preclinical models that accurately mimic the intricate tumour microenvironment to induce cellular metabolic changes and secretion of tumour-associated VOCs. In this study, a microfluidic device was used to recreate the ischaemic environment within solid tumours for the detection of tumour-derived VOCs. The system represents a significant advance in understanding the role of VOCs as biomarkers for early tumour detection and holds the potential to improve patient prognosis; particularly for inaccessible and rapidly progressing tumours such as glioblastoma.

Beyond blood: Advancing the frontiers of liquid biopsy in oncology and personalized medicine

Liquid biopsy is emerging as a pivotal tool in precision oncology, offering a noninvasive and comprehensive approach to cancer diagnostics and management. By harnessing biofluids such as blood, urine, saliva, cerebrospinal fluid, and pleural effusions, this technique profiles key biomarkers including circulating tumor DNA, circulating tumor cells, microRNAs, and extracellular vesicles. This review discusses the extended scope of liquid biopsy, highlighting its indispensable role in enhancing patient outcomes through early detection, continuous monitoring, and tailored therapy. While the advantages are notable, we also address the challenges, emphasizing the necessity for precision, cost-effectiveness, and standardized methodologies in its broader application. The future trajectory of liquid biopsy is set to expand its reach in personalized medicine, fueled by technological advancements and collaborative research.

Immunohistochemistry Detection of Histone H3 K27M Mutation in Human Glioma Tissue

The presence of the histone 3 (H3) K27M mutation in diffuse midline glioma has implications for diagnosis, prognosis, and treatment, making rapid and accurate H3 K27M characterization vital for optimal treatment. This study evaluated an immunohistochemical assay using a commercially available monoclonal anti-H3 K27M in human central nervous system tumors. H3 K27M-positive glioma specimens were obtained from clinical sites with prior H3 K27M testing using local methods; negative control glioblastoma tissue was obtained from a tissue library. Specimens were stained with a rabbit anti-H3 K27M monoclonal antibody; slides were evaluated for the proportion of H3 K27M-positive tumor cells and staining intensity by a board-certified pathologist. H-score was calculated for each sample. Sensitivity, specificity, accuracy, repeatability, and reproducibility were evaluated. Fifty-one central nervous system specimens were stained (H3 K27M, n=41; H3 wild type, n=10). All H3 K27M-mutant specimens had positive nuclear staining, and most specimens had an H-score ≥150 (31/40, 77.5%). No nuclear staining occurred in H3 wild-type specimens; all cores in the normal tissue microarray were negative. Results were 100% sensitive, specific, and accurate for H3 K27M detection relative to local methods. Repeatability and reproducibility analyses were 100%, with a high degree of concordance for staining intensity. H3 K27M antigen was stable for at least 12 months at ambient temperature. Immunohistochemistry using a commercially available anti-H3 K27M monoclonal antibody provides a highly sensitive, specific, and stable method of establishing H3 K27M status in human glioma; this method may facilitate diagnosis in cases where sequencing is not feasible or available.

Liquid Biopsies for Monitoring Medulloblastoma: Circulating Tumor DNA as a Biomarker for Disease Progression and Treatment Response

Pediatric brain tumors, including medulloblastoma (MB), represent a significant challenge in clinical oncology. Early diagnosis, accurate monitoring of therapeutic response, and the detection of minimal residual disease (MRD) are crucial for improving outcomes in these patients. This review aims to explore recent advancements in liquid biopsy techniques for monitoring pediatric brain tumors, with a specific focus on medulloblastoma. The primary research question is how liquid biopsy techniques can be effectively utilized for these purposes. Liquid biopsies, particularly the analysis of circulating tumor DNA (ctDNA) in cerebrospinal fluid (CSF), are investigated as promising noninvasive tools. This comprehensive review examines the components of liquid biopsies, including ctDNA, cell-free DNA (cfDNA), and microRNA (miRNA). Their applications in diagnosis, prognosis, and MRD assessment are critically assessed. The review also discusses the role of liquid biopsies in categorizing medulloblastoma subgroups, risk stratification, and the identification of therapeutic targets. Liquid biopsies have shown promising applications in the pediatric brain tumor field, particularly in medulloblastoma. They offer noninvasive means of diagnosis, monitoring treatment response, and detecting MRD. These biopsies have played a pivotal role in subgroup classification and risk stratification of medulloblastoma patients, aiding in the identification of therapeutic targets. However, challenges related to sensitivity and specificity are noted. In conclusion, this review highlights the growing importance of liquid biopsies, specifically ctDNA analysis in CSF, in pediatric brain tumor management, with a primary focus on medulloblastoma. Liquid biopsies have the potential to revolutionize patient care by enabling early diagnosis, accurate monitoring, and MRD detection. Nevertheless, further research is essential to validate their clinical utility fully. The evolving landscape of liquid biopsy applications underscores their promise in improving outcomes for pediatric brain tumor patients.

Adding Value to Liquid Biopsy for Brain Tumors: The Role of Imaging

Clinical management in neuro-oncology has changed to an integrative approach that incorporates molecular profiles alongside histopathology and imaging findings. While the World Health Organization (WHO) guideline recommends the genotyping of informative alterations as a routine clinical practice for central nervous system (CNS) tumors, the acquisition of tumor tissue in the CNS is invasive and not always possible. Liquid biopsy is a non-invasive approach that provides the opportunity to capture the complex molecular heterogeneity of the whole tumor through the detection of circulating tumor biomarkers in body fluids, such as blood or cerebrospinal fluid (CSF). Despite all of the advantages, the low abundance of tumor-derived biomarkers, particularly in CNS tumors, as well as their short half-life has limited the application of liquid biopsy in clinical practice. Thus, it is crucial to identify the factors associated with the presence of these biomarkers and explore possible strategies that can increase the shedding of these tumoral components into biological fluids. In this review, we first describe the clinical applications of liquid biopsy in CNS tumors, including its roles in the early detection of recurrence and monitoring of treatment response. We then discuss the utilization of imaging in identifying the factors that affect the detection of circulating biomarkers as well as how image-guided interventions such as focused ultrasound can help enhance the presence of tumor biomarkers through blood-brain barrier (BBB) disruption.

The Current Landscape of Glioblastoma Biomarkers in Body Fluids

Glioblastoma (GBM) is a highly aggressive and lethal primary brain cancer that necessitates early detection and accurate diagnosis for effective treatment and improved patient outcomes. Traditional diagnostic methods, such as imaging techniques and tissue biopsies, have limitations in providing real-time information and distinguishing treatment-related changes from tumor progression. Liquid biopsies, used to analyze biomarkers in body fluids, offer a non-invasive and dynamic approach to detecting and monitoring GBM. This article provides an overview of GBM biomarkers in body fluids, including circulating tumor cells (CTCs), cell-free DNA (cfDNA), cell-free RNA (cfRNA), microRNA (miRNA), and extracellular vesicles. It explores the clinical utility of these biomarkers for GBM detection, monitoring, and prognosis. Challenges and limitations in implementing liquid biopsy strategies in clinical practice are also discussed. The article highlights the potential of liquid biopsies as valuable tools for personalized GBM management but underscores the need for standardized protocols and further research to optimize their clinical utility.

Plasma PD-L1 as a biomarker in the clinical management of glioblastoma multiforme-a retrospective cohort study

Background and objectives

Glioblastoma multiforme (GBM) is the most aggressive, malignant, and therapy-resistant tumor of the brain. Blockade therapy targeting the programmed cell death protein 1 (PD-1)/programmed death ligand (PD-L1) axis is currently under investigation for the clinical management of the GBM. This study has quantified the plasma levels of PD-L1 as a biomarker for the clinical management of GBM.

Methods

A cohort (n = 128) of Pakistani adult glioblastoma patients together with age- and sex-matched healthy controls was used for quantification of pre-surgery levels of plasma PD-L1. PD-L1 protein and mRNA were measured by PD-L1 platinum enzyme-linked immunosorbent assay and quantitative real-time PCR, respectively. Receiver operating characteristic (ROC) curve analysis was used to compute area under the curve (AUC) for specificity and sensitivity analyses. The Kaplan-Meier survival analysis was employed to compute overall survival.

Results

PD-L1 protein and mRNA were significantly higher in GBM compared to the healthy controls (p < 0.0001). Mean PD-L1 concentration for the GBM was found to be 48.98 ± 2.290 pg/ml compared to 27.63 ± 1.281 pg/ml for controls. Gene expression analysis showed statistically significant upregulation (p < 0.0001) of PD-L1 in blood of GBM compared to healthy controls. Plasma PD-L1 showed an AUC of 0.840 (p < 0.0001; 95% CI = 0.7716 to 0.9090) where a cutoff value higher than 46 pg/ml demonstrated 100% specificity and 57.81% sensitivity. Higher pre-surgery levels of PD-L1 were found to be associated with overall poor survival [p < 0.0001; HR (log-rank) = 0.08; 95% CI = 0.04 to 0.15]. Age, gender, and ethnic background were not found to be associated with plasma PD-L1 levels.

Conclusion

The study concludes that blood-based measurements of PD-L1 in GBM can be a promising prognostic marker and therapeutic target besides a rapid and relatively non-invasive screening tool for routine clinical management. Future work extending the analysis to larger cohorts through multi-center collaborations involving pre-treatment and post-treatment groups is required to fully explore the usefulness of circulating PD-L1 for effective clinical applications.

Technological and computational approaches to detect somatic mosaicism in epilepsy

Lesional epilepsy is a common and severe disease commonly associated with malformations of cortical development, including focal cortical dysplasia and hemimegalencephaly. Recent advances in sequencing and variant calling technologies have identified several genetic causes, including both short/single nucleotide and structural somatic variation. In this review, we aim to provide a comprehensive overview of the methodological advancements in this field while highlighting the unresolved technological and computational challenges that persist, including ultra-low variant allele fractions in bulk tissue, low availability of paired control samples, spatial variability of mutational burden within the lesion, and the issue of false-positive calls and validation procedures. Information from genetic testing in focal epilepsy may be integrated into clinical care to inform histopathological diagnosis, postoperative prognosis, and candidate precision therapies.

Cell-free DNA-based liquid biopsies in neurology

This article reviews recent developments in the application of cell-free DNA-based liquid biopsies to neurological diseases. Over the past few decades, an explosion of interest in the use of accessible biofluids to identify and track molecular disease has revolutionized the fields of oncology, prenatal medicine and others. More recently, technological advances in signal detection have allowed for informative analysis of biofluids that are typically sparse in cells and other circulating components, such as CSF. In parallel, advancements in epigenetic profiling have allowed for novel applications of liquid biopsies to diseases without characteristic mutational profiles, including many degenerative, autoimmune, inflammatory, ischaemic and infectious disorders. These events have paved the way for a wide array of neurological conditions to benefit from enhanced diagnostic, prognostic, and treatment abilities through the use of liquid biomarkers: a 'liquid biopsy' approach. This review includes an overview of types of liquid biopsy targets with a focus on circulating cell-free DNA, methods used to identify and probe potential liquid biomarkers, and recent applications of such biomarkers to a variety of complex neurological conditions including CNS tumours, stroke, traumatic brain injury, Alzheimer's disease, epilepsy, multiple sclerosis and neuroinfectious disease. Finally, the challenges of translating liquid biopsies to use in clinical neurology settings-and the opportunities for improvement in disease management that such translation may provide-are discussed.

A standardised methodology for the extraction and quantification of cell-free DNA in cerebrospinal fluid and application to evaluation of Alzheimer's disease and brain cancers

Cerebrospinal fluid (CSF) is a source of diagnostic biomarkers for a range of neurological conditions. Cell-free DNA (cfDNA) is detected in CSF and differences in the concentration of cell-free mitochondrial DNA have been reported in studies of neurodegenerative disorders including Alzheimer's disease (AD). However, the influence of pre-analytical steps has not been investigated for cfDNA in CSF and there is no standardised approach for quantification of total cfDNA (copies of nuclear genome or mitochondria-derived gene targets). In this study, the suitability of four extraction methods was evaluated: QIAamp Circulating Nucleic Acid (Qiagen), Quick-cfDNA Serum & Plasma (Zymo), NucleoSnap® DNA Plasma (Macherey-Nagel) and Plasma/Serum Circulating DNA Purification Mini (Norgen) kits, for cfDNA extraction from CSF of controls and AD dementia patients, utilising a spike-in control for extraction efficiency and fragment size. One of the optimal extraction methods was applied to a comparison of cfDNA concentrations in CSF from control subjects, AD dementia and primary and secondary brain tumour patients. Extraction efficiency based on spike-in recovery was similar in all three groups whilst both endogenous mitochondrial and nucleus-derived cfDNA was significantly higher in CSF from cancer patients compared to control and AD groups, which typically contained < 100 genome copies/mL. This study shows that it is feasible to measure low concentration nuclear and mitochondrial gene targets in CSF and that normalisation of extraction yield can help control pre-analytical variability influencing biomarker measurements.

Advances in nano-based materials for glioblastoma multiforme diagnosis: A mini-review

The development of nano-based materials for diagnosis enables a more precise prognosis and results. Inorganic, organic, or hybrid nanoparticles using nanomaterials, such as quantum dots, extracellular vesicle systems, and others, with different molecular compositions, have been extensively explored as a better strategy to overcome the blood-brain barrier and target brain tissue and tumors. Glioblastoma multiforme (GBM) is the most common and aggressive primary tumor of the central nervous system, with a short, established prognosis. The delay in early detection is considered a key challenge in designing a precise and efficient treatment with the most encouraging prognosis. Therefore, the present mini-review focuses on discussing distinct strategies presented recently in the literature regarding nanostructures’ use, design, and application for GBM diagnosis.