Metabolic response patterns in brain microdialysis fluids and serum during interstitial cisplatin treatment of high-grade glioma

Understanding serine and glycine metabolism in cancer: a path towards precision medicine to improve patient's outcomes

In this perspective, we highlight and reflect on the current knowledge with respect to serine/glycine metabolism in cancer, therapeutic resistance, and precision medicine opportunities for therapeutic targeting and treatment follow-up. Cancer subtypes with high mortality rates include lung cancer and glioblastomas. In order to improve future therapeutic opportunities, patient stratification need to be performed to select patients that might benefit from adjuvant serine/glycine targeting compounds. In an effort to identify the group of patients for stratification purposes, we analyzed publicly available TCGA patient datasets to test associations between serine/glycine metabolism enzyme expression and important cancer drivers in lung cancer and glioblastoma. These patients presenting serine/glycine pathway overexpression might benefit from adjuvant sertraline treatment in the future.

In vivo photopharmacological inhibition of hippocampal activity via multimodal probes - perspective and opening steps on experimental and computational challenges

Neurological conditions such as epilepsy can have a significant impact on people's lives. Here, we discuss a new perspective for the study/treatment of these conditions using photopharmacology. A multimodal, intracranial implant that incorporates fluidic channels for localised drug delivery, electrodes for recording and stimulation, and a light source for photoswitching is used for in vivo administration and deactivation of a photoresponsive AMPA antagonist. We review current advancements in the relevant disciplines and show experimentally that the inhibition of seizure-like events induced in the hippocampus by electrical stimulation can be altered upon switching the drug with light. We discuss the interconnection of the drug's photopharmacological properties with the design of the device by modelling light penetration into the rat brain with Monte Carlo simulations. This work delivers a new perspective, including initial experimental and computational efforts on in vivo photopharmacology to understand and eventually treat neurological conditions.

Blood based metabolic markers of glioma from pre-diagnosis to surgery

Gliomas are highly complex and metabolically active brain tumors associated with poor prognosis. Recent reports have found altered levels of blood metabolites during early tumor development, suggesting that tumor development could be detected several years before clinical manifestation. In this study, we performed metabolite analyses of blood samples collected from healthy controls and future glioma patients, up to eight years before glioma diagnosis, and on the day of glioma surgery. We discovered that metabolites related to early glioma development were associated with an increased energy turnover, as highlighted by elevated levels of TCA-related metabolites such as fumarate, malate, lactate and pyruvate in pre-diagnostic cases. We also found that metabolites related to glioma progression at surgery were primarily high levels of amino acids and metabolites of amino acid catabolism, with elevated levels of 11 amino acids and two branched-chain alpha-ketoacids, ketoleucine and ketoisoleucine. High amino acid turnover in glioma tumor tissue is currently utilized for PET imaging, diagnosis and delineation of tumor margins. By examining blood-based metabolic progression patterns towards disease onset, we demonstrate that this high amino acid turnover is also detectable in a simple blood sample. These findings provide additional insight of metabolic alterations during glioma development and progression.

LAPTM4B counteracts ferroptosis via suppressing the ubiquitin-proteasome degradation of SLC7A11 in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related deaths worldwide, necessitating the identification of novel therapeutic targets. Lysosome Associated Protein Transmembrane 4B (LAPTM4B) is involved in biological processes critical to cancer progression, such as regulation of solute carrier transporter proteins and metabolic pathways, including mTORC1. However, the metabolic processes governed by LAPTM4B and its role in oncogenesis remain unknown. In this study, we conducted unbiased metabolomic screens to uncover the metabolic landscape regulated by LAPTM4B. We observed common metabolic changes in several knockout cell models suggesting of a role for LAPTM4B in suppressing ferroptosis. Through a series of cell-based assays and animal experiments, we demonstrate that LAPTM4B protects tumor cells from erastin-induced ferroptosis both in vitro and in vivo. Mechanistically, LAPTM4B suppresses ferroptosis by inhibiting NEDD4L/ZRANB1 mediated ubiquitination and subsequent proteasomal degradation of the cystine-glutamate antiporter SLC7A11. Furthermore, metabolomic profiling of cancer cells revealed that LAPTM4B knockout leads to a significant enrichment of ferroptosis and associated metabolic alterations. By integrating results from cellular assays, patient tissue samples, an animal model, and cancer databases, this study highlights the clinical relevance of the LAPTM4B-SLC7A11-ferroptosis signaling axis in NSCLC progression and identifies it as a potential target for the development of cancer therapeutics.

Methodological and analytical considerations for intra-operative microdialysis

BACKGROUND

Microdialysis is a technique that can be utilized to sample the interstitial fluid of the central nervous system (CNS), including in primary malignant brain tumors known as gliomas. Gliomas are mainly accessible at the time of surgery, but have rarely been analyzed via interstitial fluid collected via microdialysis. To that end, we obtained an investigational device exemption for high molecular weight catheters (HMW, 100 kDa) and a variable flow rate pump to perform microdialysis at flow rates amenable to an intra-operative setting. We herein report on the lessons and insights obtained during our intra-operative HMW microdialysis trial, both in regard to methodological and analytical considerations.

METHODS

Intra-operative HMW microdialysis was performed during 15 clinically indicated glioma resections in fourteen patients, across three radiographically diverse regions in each patient. Microdialysates were analyzed via targeted and untargeted metabolomics via ultra-performance liquid chromatography tandem mass spectrometry.

RESULTS

Use of albumin and lactate-containing perfusates impacted subsets of metabolites evaluated via global metabolomics. Additionally, focal delivery of lactate via a lactate-containing perfusate, induced local metabolic changes, suggesting the potential for intra-operative pharmacodynamic studies via reverse microdialysis of candidate drugs. Multiple peri-operatively administered drugs, including levetiracetam, cefazolin, caffeine, mannitol and acetaminophen, could be detected from one microdialysate aliquot representing 10 min worth of intra-operative sampling. Moreover, clinical, radiographic, and methodological considerations for performing intra-operative microdialysis are discussed.

CONCLUSIONS

Intra-operative HMW microdialysis can feasibly be utilized to sample the live human CNS microenvironment, including both metabolites and drugs, within one surgery. Certain variables, such as perfusate type, must be considered during and after analysis. Trial registration NCT04047264.

Alterations in cellular metabolism under different grades of glioma staging identified based on a multi-omics analysis strategy

Glioma is a type of brain tumor closely related to abnormal cell metabolism. Firstly, multiple combinatorial sequencing studies have revealed this relationship. Genomic studies have identified gene mutations and gene expression disorders related to the development of gliomas, which affect cell metabolic pathways. In addition, transcriptome studies have revealed the genes and regulatory networks that regulate cell metabolism in glioma tissues. Metabonomics studies have shown that the metabolic pathway of glioma cells has changed, indicating their distinct energy and nutritional requirements. This paper focuses on the retrospective analysis of multiple groups combined with sequencing to analyze the changes in various metabolites during metabolism in patients with glioma. Finally, the changes in genes, regulatory networks, and metabolic pathways regulating cell metabolism in patients with glioma under different metabolic conditions were discussed. It is also proposed that multi-group metabolic analysis is expected to better understand the mechanism of abnormal metabolism of gliomas and provide more personalized methods and guidance for early diagnosis, treatment, and prognosis evaluation of gliomas.

Precise Construction of Dual-Promising Anticancer Drugs Associated with Gold Nanomaterials on Glioma Cancer Cells

Multiple chemodrugs with nanotechnology have proven to be an effective cancer treatment technique. When taken combined, cabazitaxel (CTX) and cisplatin (PT) have more excellent cytotoxic effects than drugs used alone in the chemotherapy of several different cancers. However, several severe side effects are associated with using these chemotherapy drugs in cancer patients. Gold nanomaterials (AuNMs) are promising as drug carriers because of their small diameter, easy surface modifications, good biocompatibility, and strong cell penetration. This work aimed to determine the CTX and PT encapsulated with AuNMs against human glioma U87 cancer cells. The fabrication of the AuNMs achieved a negative surface charge, polydispersity index, and the mean sizes. The combined cytotoxic effect of CTX and PT bound to AuNMs was greater than that of either drug alone when tested on U87 cells. The half inhibitory concentration (IC50) values for free PT were 54.7 μg/mL (at 24 h) and 4.8 g μg/mL (at 72 h). Results acquired from the MTT assay show cell growth decreases time- and concentration-dependent AuNMs, free CTX, free PT, and AuNMs@CTX/PT-induced cytotoxicity and, ultimately, the cell death of U87 cells via apoptosis. The biochemical apoptosis staining techniques investigated the cells' morphological changes of the cells (acridine orange and ethidium bromide (AO-EB) and nuclear staining (DAPI) techniques). The AO-EB and nuclear staining results reveal that the NPs effectively killed cancer cells. Furthermore, the flow cytometry analysis examined the mode of cell death. Therefore, AuNMs@CTX/PT has excellent potential in the cancer therapy of different cancer cells.

Glioma Metabolic Feedback In Situ: A First-In-Human Pharmacodynamic Trial of Difluoromethylornithine + AMXT-1501 Through High-Molecular Weight Microdialysis

BACKGROUND AND OBJECTIVES

No new drug has improved survival for glioblastoma since temozolomide in 2005, due in part to the relative inaccessibility of each patient's individualized tumor biology and its response to therapy. We have identified a conserved extracellular metabolic signature of enhancing high-grade gliomas enriched for guanidinoacetate (GAA). GAA is coproduced with ornithine, the precursor to protumorigenic polyamines through ornithine decarboxylase (ODC). AMXT-1501 is a polyamine transporter inhibitor that can overcome tumoral resistance to the ODC inhibitor, difluoromethylornithine (DFMO). We will use DFMO with or without AMXT-1501 to identify candidate pharmacodynamic biomarkers of polyamine depletion in patients with high-grade gliomas in situ . We aim to determine (1) how blocking polyamine production affects intratumoral extracellular guanidinoacetate abundance and (2) the impact of polyamine depletion on the global extracellular metabolome within live human gliomas in situ.

METHODS

DFMO, with or without AMXT-1501, will be administered postoperatively in 15 patients after clinically indicated subtotal resection for high-grade glioma. High-molecular weight microdialysis catheters implanted into residual tumor and adjacent brain will be used for postoperative monitoring of extracellular GAA and polyamines throughout therapeutic intervention from postoperative day (POD) 1 to POD5. Catheters will be removed on POD5 before discharge.

EXPECTED OUTCOMES

We anticipate that GAA will be elevated in tumor relative to adjacent brain although it will decrease within 24 hours of ODC inhibition with DFMO. If AMXT-1501 effectively increases the cytotoxic impact of ODC inhibition, we expect an increase in biomarkers of cytotoxicity including glutamate with DFMO + AMXT-1501 treatment when compared with DFMO alone.

DISCUSSION

Limited mechanistic feedback from individual patients' gliomas hampers clinical translation of novel therapies. This pilot Phase 0 study will provide in situ feedback during DFMO + AMXT-1501 treatment to determine how high-grade gliomas respond to polyamine depletion.

Blood-brain barrier disruption defines the extracellular metabolome of live human high-grade gliomas

The extracellular microenvironment modulates glioma behaviour. It remains unknown if blood-brain barrier disruption merely reflects or functionally supports glioma aggressiveness. We utilised intra-operative microdialysis to sample the extracellular metabolome of radiographically diverse regions of gliomas and evaluated the global extracellular metabolome via ultra-performance liquid chromatography tandem mass spectrometry. Among 162 named metabolites, guanidinoacetate (GAA) was 126.32x higher in enhancing tumour than in adjacent brain. 48 additional metabolites were 2.05-10.18x more abundant in enhancing tumour than brain. With exception of GAA, and 2-hydroxyglutarate in IDH-mutant gliomas, differences between non-enhancing tumour and brain microdialysate were modest and less consistent. The enhancing, but not the non-enhancing glioma metabolome, was significantly enriched for plasma-associated metabolites largely comprising amino acids and carnitines. Our findings suggest that metabolite diffusion through a disrupted blood-brain barrier may largely define the enhancing extracellular glioma metabolome. Future studies will determine how the altered extracellular metabolome impacts glioma behaviour.

Advances in computational and translational approaches for malignant glioma

Gliomas are the most common primary brain tumors in adults and carry a dismal prognosis for patients. Current standard-of-care for gliomas is comprised of maximal safe surgical resection following by a combination of chemotherapy and radiation therapy depending on the grade and type of tumor. Despite decades of research efforts directed towards identifying effective therapies, curative treatments have been largely elusive in the majority of cases. The development and refinement of novel methodologies over recent years that integrate computational techniques with translational paradigms have begun to shed light on features of glioma, previously difficult to study. These methodologies have enabled a number of point-of-care approaches that can provide real-time, patient-specific and tumor-specific diagnostics that may guide the selection and development of therapies including decision-making surrounding surgical resection. Novel methodologies have also demonstrated utility in characterizing glioma-brain network dynamics and in turn early investigations into glioma plasticity and influence on surgical planning at a systems level. Similarly, application of such techniques in the laboratory setting have enhanced the ability to accurately model glioma disease processes and interrogate mechanisms of resistance to therapy. In this review, we highlight representative trends in the integration of computational methodologies including artificial intelligence and modeling with translational approaches in the study and treatment of malignant gliomas both at the point-of-care and outside the operative theater in silico as well as in the laboratory setting.

Low-grade glioma risk SNP rs11706832 is associated with type I interferon response pathway genes in cell lines

Genome-wide association studies (GWAS) have contributed to our understanding of glioma susceptibility. To date, 25 risk loci for development of any of the glioma subtypes are known. However, GWAS studies reveal little about the molecular processes that lead to increased risk, especially for non-coding single nucleotide polymorphisms (SNP). A particular SNP in intron 2 of LRIG1, rs11706832, has been shown to increase the susceptibility for IDH1 mutated low-grade gliomas (LGG). Leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) is important in cancer development as it negatively regulates the epidermal growth factor receptor (EGFR); however, the mechanism responsible for this particular risk SNP and its potential effect on LRIG1 are not known. Using CRISPR-CAS9, we edited rs11706832 in HEK293T cells. Four HEK293T clones with the risk allele were compared to four clones with the non-risk allele for LRIG1 and SLC25A26 gene expression using RT-qPCR, for global gene expression using RNA-seq, and for metabolites using gas chromatography-mass spectrometry (GC-MS). The experiment did not reveal any significant effect of the SNP on the expression levels or splicing patterns of LRIG1 or SLC25A26. The global gene expression analysis revealed that the risk allele C was associated with upregulation of several mitochondrial genes. Gene enrichment analysis of 74 differentially expressed genes in the genome revealed a significant enrichment of type I interferon response genes, where many genes were downregulated for the risk allele C. Gene expression data of IDH1 mutated LGGs from the cancer genome atlas (TCGA) revealed a similar under expression of type I interferon genes associated with the risk allele. This study found the expression levels and splicing patterns of LRIG1 and SLC25A26 were not affected by the SNP in HEK293T cells. However, the risk allele was associated with a downregulation of genes involved in the innate immune response both in the HEK293T cells and in the LGG data from TCGA.

Quantitative monitoring and modelling of retrodialysis drug delivery in a brain phantom

A vast number of drug molecules are unable to cross the blood-brain barrier, which results in a loss of therapeutic opportunities when these molecules are administered by intravenous infusion. To circumvent the blood-brain barrier, local drug delivery devices have been developed over the past few decades such as reverse microdialysis. Reverse microdialysis (or retrodialysis) offers many advantages, such as a lack of net volume influx to the intracranial cavity and the ability to sample the tumour's micro-environment. However, the translation of this technique to efficient drug delivery has not been systematically studied. In this work, we present an experimental platform to evaluate the performance of microdialysis devices in reverse mode in a brain tissue phantom. The mass of model drug delivered is measured by computing absorbance fields from optical images. Concentration maps are reconstructed using a modern and open-source implementation of the inverse Abel transform. To illustrate our method, we assess the capability of a commercial probe in delivering methylene blue to a gel phantom. We find that the delivery rate can be described by classical microdialysis theory, except at low dialysate flow rates where it is impacted by gravity, and high flow rates where significant convection to the gel occurs. We also show that the flow rate has an important impact not only on the overall size of the drug plume, but also on its shape. The numerical tools developed for this study have been made freely available to ensure that the method presented can be used to rapidly and inexpensively optimise probe design and protocol parameters before proceeding to more in-depth studies.

Changes in CA15-3, S100B, and IGF-1 in glioma and their predictive value for treatment efficacy

OBJECTIVE

To analyze the changes of carbohydrate antigen 153 (CA15-3), S-100 calcium-binding protein B (S100B) and insulin-like growth factor-1 (IGF-1) in the treatment of patients with high-grade glioma and their predictive value for efficacy.

METHODS

In this retrospective the PG and CG study, 74 patients with glioma who were treated in the Affiliated Hospital of Yan'an University from January 2015 to January 2017 were labeled as the patient group (PG); the other 70 patients who underwent craniocerebral trauma surgery during the same period were selected as the control group (CG). The expressions of CA15-3, S100B and IGF-1 in the PG and CG were compared. The relationship between CA15-3, S100B, IGF-1, and the pathologic data of patients was analyzed. The expression differences of CA15-3, S100B, and IGF-1 were compared between low-grade glioma patients and high-grade glioma patients and their diagnostic value was analyzed. The values of CA15-3, S100B, and IGF-1 expression for predicting treatment efficacy were analyzed.

RESULTS

Expressions of CA15-3, S100B, and IGF-1 in glioma patients were markedly higher than those in the CG (P<0.0001). The proportion of grade III+IV patients with high expression of CA15-3, S100B, and IGF-1 was higher than in grade II patients (P<0.05), and the expressions of CA15-3, S100B and IGF-1 in low-grade glioma patients were lower than in high-grade glioma (P<0.01). The AUCs of CA15-3, S100B, and IGF-1 in differentiating different grades of glioma were 0.822, 0.722, and 0.768, respectively. Serum CA15-3, S100B and IGF-1 levels of the patients after treatment were significantly lower than those before treatment (P<0.0001). With the deterioration of clinical efficacy, serum levels of CA15-3, S100B, and IGF-1 gradually increased (P<0.05), and CA15-3, S100B and IGF-1 were positively correlated with therapeutic efficacy (P<0.05). AUCs of CA15-3, S100B, and IGF-1 for predicting the clinical efficacy in glioma patients were 0.824, 0.741, and 0.800, respectively.

CONCLUSION

CA15-3, S100B, and IGF-1 are highly expressed in patients with glioma. They are diagnostic indicators to distinguish patients with high-grade glioma, and have predictive value for treatment efficacy.

Proline Metabolism in Malignant Gliomas: A Systematic Literature Review

Simple Summary

Studies of various types of cancers have found proline metabolism to be a key player in tumor development, involved in basic metabolic pathways, regulating cell proliferation, survival, and signaling. Here, we systematically searched the literature to find data on proline metabolism in malignant glial tumors. Despite limited availability, existing studies have found several ways in which proline metabolism may affect the development of gliomas, involving the maintenance of redox balance, providing essential glutamate, and affecting major signaling pathways. Metabolomic profiling has revealed the importance of proline as a link to basic cell metabolic cycles and shown it to be correlated with overall survival. Emerging knowledge on the role of proline in general oncology encourages further studies on malignant gliomas.

Abstract

Background: Proline has attracted growing interest because of its diverse influence on tumor metabolism and the discovery of the regulatory mechanisms that appear to be involved. In contrast to general oncology, data on proline metabolism in central nervous system malignancies are limited. Materials and Methods: We performed a systematic literature review of the MEDLINE and EMBASE databases according to PRISMA guidelines, searching for articles concerning proline metabolism in malignant glial tumors. From 815 search results, we identified 14 studies pertaining to this topic. Results: The role of the proline cycle in maintaining redox balance in IDH-mutated gliomas has been convincingly demonstrated. Proline is involved in restoring levels of glutamate, the main glial excitatory neurotransmitter. Proline oxidase influences two major signaling pathways: p53 and NF- κB. In metabolomics studies, the metabolism of proline and its link to the urea cycle was found to be a prognostic factor for survival and a marker of malignancy. Data on the prolidase concentration in the serum of glioblastoma patients are contradictory. Conclusions: Despite a paucity of studies in the literature, the available data are interesting enough to encourage further research, especially in terms of extrapolating what we have learned of proline functions from other neoplasms to malignant gliomas.

Methods for intratumoral microdialysis probe targeting and validation in murine brain tumor models

BACKGROUND

Microdialysis is a well validated sampling technique that can be used for pharmacokinetic studies of oncological drugs targeting the central nervous system. This technique has also been applied to evaluate tumor metabolism and identify pharmacodynamic biomarkers of drug activity. Despite the potential utility of microdialysis for therapeutic discovery, variability in tumor size and location hamper routine use of microdialysis as a preclinical tool. Quantitative validation of microdialysis membrane location relative to radiographically evident tumor regions could facilitate rigorous preclinical studies. However, a widely accessible standardized workflow for preclinical catheter placement and validation is needed.

NEW METHOD

We provide methods for a workflow to yield tailored placement of microdialysis probes within a murine intracranial tumor and illustrate in an IDH1-mutant patient-derived xenograft (PDX) model. This detailed workflow uses a freely available on-line tool built within 3D-slicer freeware to target microdialysis probe placement within the tumor core and validate probe placement fully within the tumor.

RESULTS

We illustrate use of this workflow to validate microdialysis probe location relative to implanted IDH1-mutant PDXs, using the microdialysis probes to quantify levels of extracellular onco-metabolite D-2 hydroxyglutarate.

COMPARISON WITH EXISTING METHODS

Previous methods have used 3D slicer to reliably measure tumor volumes. Prior microdialysis studies have targeted expected tumor locations without validation.

CONCLUSIONS

The new method offers a streamlined and freely available workflow in 3D slicer to optimize and validate microdialysis probe placement within a murine brain tumor.

Metabolic control of cancer progression as novel targets for therapy

Metabolism is an important part of tumorigenesis as well as progression. The various cancer metabolism pathways, such as glucose metabolism and glutamine metabolism, directly regulate the development and progression of cancer. The pathways by which the cancer cells rewire their metabolism according to their needs, surrounding environment and host tissue conditions are an important area of study. The regulation of these metabolic pathways is determined by various oncogenes, tumor suppressor genes, as well as various constituent cells of the tumor microenvironment. Expanded studies on metabolism will help identify efficient biomarkers for diagnosis and strategies for therapeutic interventions and countering ways by which cancers may acquire resistance to therapy.

Shining a light on metabolic vulnerabilities in non-small cell lung cancer

Metabolic reprogramming is a hallmark of cancer which contributes to essential processes required for cell survival, growth, and proliferation. Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and its genomic classification has given rise to the design of therapies targeting tumors harboring specific gene alterations that cause aberrant signaling. Lung tumors are characterized with having high glucose and lactate use, and high heterogeneity in their metabolic pathways. Here we review how NSCLC cells with distinct mutations reprogram their metabolic pathways and highlight the potential metabolic vulnerabilities that might lead to the development of novel therapeutic strategies.

Intratumoral retrograde microdialysis treatment of high-grade glioma with cisplatin

PURPOSE

This study evaluates the application of a microdialysis technique for interstitial chemotherapy using cisplatin in high-grade glioma.

METHOD

An in vitro study demonstrated that cisplatin can be administered through retrograde microdialysis and defined the recovery for cisplatin. In a subsequent phase I study, 1-4 microdialysis catheters were implanted in tumor tissue, brain adjacent to tumor (BAT) tissue, and subcutaneous tissue in 10 patients with recurrent high-grade glioma. Cisplatin was administered continuously in daily doses between 0.3 and 3.9 mg for 4 to12 days. Microdialysis samples were continuously collected and analyzed for glucose metabolites, glutamate, glycerol, and cisplatin concentrations. Treatment tolerability was evaluated through clinical monitoring. Quality of life was assessed using the EORTC-QLQ-C30 questionnaire for up to 3 months after treatment.

RESULTS

This in vitro study showed that cisplatin could be administrated with a recovery of 41-97%, depending on flowrate, type of catheter, and cisplatin concentration. During the treatment, patients were exposed to a total dose of 1.2-36.8 mg cisplatin. The concentration of cisplatin in BAT, serum, and subcutaneous tissue was close to detection level in all but two patients. A transient neurologic deterioration due to edema was commonly observed, but no systemic side effects were recorded. After onset of treatment, concentrations of glutamate and glycerol were significantly increased in tumor tissue but not in BAT, with a peak after 3 days, and consistent for the rest of the treatment. Five of the patients survived between 153 and 492 days after treatment.

CONCLUSION

This phase I study demonstrates that retrograde microdialysis can be used to administer cisplatin interstitially into high-grade glioma tissue. A high cytotoxicity was detected in tumor tissue, but not in the surrounding brain. Retrograde microdialysis appears to be a clinically useful method for intratumoral drug administration in high-grade glioma.

Identification of Pre-Diagnostic Metabolic Patterns for Glioma Using Subset Analysis of Matched Repeated Time Points

Simple Summary

Reprogramming of cellular metabolism is a major hallmark of cancer cells, and play an important role in tumor initiation and progression. The aim of our study is to discover circulating early metabolic markers of brain tumors, as discovery and development of reliable predictive molecular markers are needed for precision oncology applications. We use a study design tailored to minimize confounding factors and a novel machine learning and visualization approach (SMART) to identify a panel of 15 interlinked metabolites related to glioma development. The presented SMART strategy facilitates early molecular marker discovery and can be used for many types of molecular data.

Abstract

Here, we present a strategy for early molecular marker pattern detection—Subset analysis of Matched Repeated Time points (SMART)—used in a mass-spectrometry-based metabolomics study of repeated blood samples from future glioma patients and their matched controls. The outcome from SMART is a predictive time span when disease-related changes are detectable, defined by time to diagnosis and time between longitudinal sampling, and visualization of molecular marker patterns related to future disease. For glioma, we detect significant changes in metabolite levels as early as eight years before diagnosis, with longitudinal follow up within seven years. Elevated blood plasma levels of myo-inositol, cysteine, N-acetylglucosamine, creatinine, glycine, proline, erythronic-, 4-hydroxyphenylacetic-, uric-, and aceturic acid were particularly evident in glioma cases. We use data simulation to ensure non-random events and a separate data set for biomarker validation. The latent biomarker, consisting of 15 interlinked and significantly altered metabolites, shows a strong correlation to oxidative metabolism, glutathione biosynthesis and monosaccharide metabolism, linked to known early events in tumor development. This study highlights the benefits of progression pattern analysis and provide a tool for the discovery of early markers of disease.

Cerebral Microdialysis as a Tool for Assessing the Delivery of Chemotherapy in Brain Tumor Patients

The development of curative treatment for glioblastoma has been extremely challenging. Chemotherapeutic agents that have seemed promising have failed in clinical trials. Drugs that can successfully target cancer cells within the brain must first traverse the brain interstitial fluid. Cerebral microdialysis (CMD) is an invasive technique in which interstitial fluid can be directly sampled. CMD has primarily been used clinically in the setting of head trauma and subarachnoid hemorrhage. Our goal was to review the techniques, principles, and new data pertaining to CMD to highlight its use in neuro-oncology. We conducted a literature search using the PubMed database and selected studies in which the investigators had used CMD in either animal brain tumor models or clinical trials. The references were reviewed for additional information. Studies of CMD have shown its importance as a neurosurgical technique. CMD allows for the collection of pharmacokinetic data on drug penetrance across the blood-brain barrier and metabolic data to characterize the response to chemotherapy. Although no complications have been reported, the current CMD technique (as with any procedure) has risks and limitations, which we have described in the present report. Animal CMD experiments have been used to exclude central nervous system drug candidates from progressing to clinical trials. At present, patients undergoing CMD have been monitored in the intensive care unit, owing to the requisite tethering to the apparatus. This can be expected to change soon because of advances in microminiaturization. CMD is an extremely valuable, yet underused, technique. Future CMD applications will have central importance in assessing drug delivery to tumor cells in vivo, allowing a pathway to successful therapy for malignant brain tumors.

Metabolism and cancer: the future is now

In the last decade, the field of cancer metabolism transformed itself from being a description of the metabolic features of cancer cells to become a key component of cellular transformation. Now, the potential role of this field in cancer biology is ready to be unravelled.