Interaction of brain fatty acid-binding protein with the polyunsaturated fatty acid environment as a potential determinant of poor prognosis in malignant glioma

Proteomics of tumor and serum samples from isocitrate dehydrogenase-wildtype glioblastoma patients: is the detoxification of reactive oxygen species associated with shorter survival?

Proteomics has been little used for the identification of novel prognostic and/or therapeutic markers in isocitrate dehydrogenase (IDH)-wildtype glioblastoma (GB). In this study, we analyzed 50 tumor and 30 serum samples from short- and long-term survivors of IDH-wildtype GB (STS and LTS, respectively) by data-independent acquisition mass spectrometry (DIA-MS)-based proteomics, with the aim of identifying such markers. DIA-MS identified 5422 and 826 normalized proteins in tumor and serum samples, respectively, with only three tumor proteins and 26 serum proteins displaying significant differential expression between the STS and LTS groups. These dysregulated proteins were principally associated with the detoxification of reactive oxygen species (ROS). In particular, GB patients in the STS group had high serum levels of malate dehydrogenase 1 (MDH1) and ribonuclease inhibitor 1 (RNH1) and low tumor levels of fatty acid-binding protein 7 (FABP7), which may have enabled them to maintain low ROS levels, counteracting the effects of the first-line treatment with radiotherapy plus concomitant and adjuvant temozolomide. A blood score built on the levels of MDH1 and RNH1 expression was found to be an independent prognostic factor for survival based on the serum proteome data for a cohort of 96 IDH-wildtype GB patients. This study highlights the utility of circulating MDH1 and RNH1 biomarkers for determining the prognosis of patients with IDH-wildtype GB. Furthermore, the pathways driven by these biomarkers, and the tumor FABP7 pathway, may constitute promising therapeutic targets for blocking ROS detoxification to overcome resistance to chemoradiotherapy in potential GB STS.

Steady-State Delivery and Chemical Modification of Food Nutrients to Improve Cancer Intervention Ability

Cancer is a crucial global health problem, and prevention is an important strategy to reduce the burden of the disease. Daily diet is the key modifiable risk factor for cancer, and an increasing body of evidence suggests that specific nutrients in foods may have a preventive effect against cancer. This review summarizes the current evidence on the role of nutrients from foods in cancer intervention. It discusses the potential mechanisms of action of various dietary components, including phytochemicals, vitamins, minerals, and fiber. The findings of epidemiological and clinical studies on their association with cancer risk are highlighted. The foods are rich in bioactive compounds such as carotenoids, flavonoids, and ω-3 fatty acids, which have been proven to have anticancer properties. The effects of steady-state delivery and chemical modification of these food's bioactive components on anticancer and intervention are summarized. Future research should focus on identifying the specific bioactive compounds in foods responsible for their intervention effects and exploring the potential synergistic effects of combining different nutrients in foods. Dietary interventions that incorporate multiple nutrients and whole foods may hold promise for reducing the risk of cancer and improving overall health.

FABP7 drives an inflammatory response in human astrocytes and is upregulated in Alzheimer's disease

Alzheimer's disease (AD), the most common cause of dementia in the elderly, is characterized by the accumulation of intracellular neurofibrillary tangles, extracellular amyloid plaques, and neuroinflammation. In partnership with microglial cells, astrocytes are key players in the regulation of neuroinflammation. Fatty acid binding protein 7 (FABP7) belongs to a family of conserved proteins that regulate lipid metabolism, energy homeostasis, and inflammation. FABP7 expression is largely restricted to astrocytes and radial glia-like cells in the adult central nervous system. We observed that treatment of primary hippocampal astrocyte cultures with amyloid β fragment 25-35 (Aβ25-35) induces FABP7 upregulation. In addition, FABP7 expression is upregulated in the brain of APP/PS1 mice, a widely used AD mouse model. Co-immunostaining with specific astrocyte markers revealed increased FABP7 expression in astrocytes. Moreover, astrocytes surrounding amyloid plaques displayed increased FABP7 staining when compared to non-plaque-associated astrocytes. A similar result was obtained in the brain of AD patients. Whole transcriptome RNA sequencing analysis of human astrocytes differentiated from induced pluripotent stem cells (i-astrocytes) overexpressing FABP7 identified 500 transcripts with at least a 2-fold change in expression. Gene Ontology enrichment analysis identified (i) positive regulation of cytokine production and (ii) inflammatory response as the top two statistically significant overrepresented biological processes. We confirmed that wild-type FABP7 overexpression induces an NF-κB-driven inflammatory response in human i-astrocytes. On the other hand, the expression of a ligand-binding impaired mutant FABP7 did not induce NF-κB activation. Together, our results suggest that the upregulation of FABP7 in astrocytes could contribute to the neuroinflammation observed in AD.

Fatty acid-binding proteins 3, 7, and 8 bind cholesterol and facilitate its egress from lysosomes

Cholesterol from low-density lipoprotein (LDL) can be transported to many organelle membranes by non-vesicular mechanisms involving sterol transfer proteins (STPs). Fatty acid-binding protein (FABP) 7 was identified in our previous study searching for new regulators of intracellular cholesterol trafficking. Whether FABP7 is a bona fide STP remains unknown. Here, we found that FABP7 deficiency resulted in the accumulation of LDL-derived cholesterol in lysosomes and reduced cholesterol levels on the plasma membrane. A crystal structure of human FABP7 protein in complex with cholesterol was resolved at 2.7 Å resolution. In vitro, FABP7 efficiently transported the cholesterol analog dehydroergosterol between the liposomes. Further, the silencing of FABP3 and 8, which belong to the same family as FABP7, caused robust cholesterol accumulation in lysosomes. These two FABP proteins could transport dehydroergosterol in vitro as well. Collectively, our results suggest that FABP3, 7, and 8 are a new class of STPs mediating cholesterol egress from lysosomes.

13C-SpaceM: Spatial single-cell isotope tracing reveals heterogeneity of de novo fatty acid synthesis in cancer

Metabolism has emerged as a key factor in homeostasis and disease including cancer. Yet, little is known about the heterogeneity of metabolic activity of cancer cells due to the lack of tools to directly probe it. Here, we present a novel method, 13C-SpaceM for spatial single-cell isotope tracing of glucose-dependent de novo lipogenesis. The method combines imaging mass spectrometry for spatially-resolved detection of 13C6-glucose-derived 13C label incorporated into esterified fatty acids with microscopy and computational methods for data integration and analysis. We validated 13C-SpaceM on a spatially-heterogeneous normoxia-hypoxia model of liver cancer cells. Investigating cultured cells, we revealed single-cell heterogeneity of lipogenic acetyl-CoA pool labelling degree upon ACLY knockdown that is hidden in the bulk analysis and its effect on synthesis of individual fatty acids. Next, we adapted 13C-SpaceM to analyze tissue sections of mice harboring isocitrate dehydrogenase (IDH)-mutant gliomas. We found a strong induction of de novo fatty acid synthesis in the tumor tissue compared to the surrounding brain. Comparison of fatty acid isotopologue patterns revealed elevated uptake of mono-unsaturated and essential fatty acids in the tumor. Furthermore, our analysis uncovered substantial spatial heterogeneity in the labelling of the lipogenic acetyl-CoA pool indicative of metabolic reprogramming during microenvironmental adaptation. Overall, 13C-SpaceM enables novel ways for spatial probing of metabolic activity at the single cell level. Additionally, this methodology provides unprecedented insight into fatty acid uptake, synthesis and modification in normal and cancerous tissues.

Overcoming biological barriers BBB/BBTB by designing PUFA functionalised lipid-based nanocarriers for glioblastoma targeted therapy

A major obstacle for chemotherapeutics in Glioblastoma (GB) is to reach the tumour cells due to the presence of the blood-brain barrier (BBB) and chemoresistance of anticancer drugs. The present study reports two polyunsaturated fatty acids, gamma-linolenic acid (GLA) and alpha-linolenic acid (ALA) appended nanostructured lipid carriers (NLCs) of a CNS negative chemotherapeutic drug docetaxel (DTX) for targeted delivery to GB. The ligand appended DTX-NLCs demonstrated particle size < 160 nm, PDI < 0.29 and a negative surface charge. The successful linkage of GLA (41 %) and ALA (30 %) ligand conjugation to DTX- NLCs was confirmed by diminished surface amino groups on the NLCs, lower surface charge and FTIR profiling. Fluorophore labelled GLA-DTX-NLCs and ALA-DTX-NLCs permeated the in-vitro 3D BBB model with Papp values of 1.8 × 10-3 and 1.9 × 10-3 cm/s respectively. Following permeation, both formulations showed enhanced uptake by GB immortalised cells while ALA-DTX-NLCs showed higher uptake in patient-derived GB cells as evidenced in an in-vitro 3D blood brain tumour barrier (BBTB) model. Both surface functionalised formulations showed higher internalisation in GB cells as compared to bare DTX-NLCs. ALA-DTX-NLCs and GLA-DTX-NLCs showed 13.9-fold and 6.8-fold higher DTX activity respectively at 24 h as indicated by IC50 values when tested in patient-derived GB cells. ALA-DTX-NLCs displayed better efficacy than GLA-DTX-NLCs when tested against 3D tumour spheroids and patient-derived cells. These novel formulations will contribute widely to overcoming biological barriers for treating glioblastoma.

FADS2 function at the major cancer hotspot 11q13 locus alters fatty acid metabolism in cancer

Dysregulation of fatty acid metabolism and de novo lipogenesis is a key driver of several cancer types through highly unsaturated fatty acid (HUFA) signaling precursors such as arachidonic acid. The human chromosome 11q13 locus has long been established as the most frequently amplified in a variety of human cancers. The fatty acid desaturase genes (FADS1, FADS2 and FADS3) responsible for HUFA biosynthesis localize to the 11q12-13.1 region. FADS2 activity is promiscuous, catalyzing biosynthesis of several unsaturated fatty acids by Δ6, Δ8, and Δ4 desaturation. Our main aim here is to review known and putative consequences of FADS2 dysregulation due to effects on the 11q13 locus potentially driving various cancer types. FADS2 silencing causes synthesis of sciadonic acid (5Z,11Z,14Z-20:3) in MCF7 cells and breast cancer in vivo. 5Z,11Z,14Z-20:3 is structurally identical to arachidonic acid (5Z,8Z,11Z,14Z-20:4) except it lacks the internal Δ8 double bond required for prostaglandin and leukotriene synthesis, among other eicosanoids. Palmitic acid has substrate specificity for both SCD and FADS2. Melanoma, prostate, liver and lung cancer cells insensitive to SCD inhibition show increased FADS2 activity and sapienic acid biosynthesis. Elevated serum mead acid levels found in hepatocellular carcinoma patients suggest an unsatisfied demand for arachidonic acid. FADS2 circular RNAs are at high levels in colorectal and lung cancer tissues. FADS2 circular RNAs are associated with shorter overall survival in colorectal cancer patients. The evidence thusfar supports an effort for future research on the role of FADS2 as a tumor suppressor in a range of neoplastic disorders.

The Multifunctional Family of Mammalian Fatty Acid-Binding Proteins

Fatty acid-binding proteins (FABPs) are small lipid-binding proteins abundantly expressed in tissues that are highly active in fatty acid (FA) metabolism. Ten mammalian FABPs have been identified, with tissue-specific expression patterns and highly conserved tertiary structures. FABPs were initially studied as intracellular FA transport proteins. Further investigation has demonstrated their participation in lipid metabolism, both directly and via regulation of gene expression, and in signaling within their cells of expression. There is also evidence that they may be secreted and have functional impact via the circulation. It has also been shown that the FABP ligand binding repertoire extends beyond long-chain FAs and that their functional properties also involve participation in systemic metabolism. This article reviews the present understanding of FABP functions and their apparent roles in disease, particularly metabolic and inflammation-related disorders and cancers.

Lipid Metabolic Regulatory Crosstalk Between Cancer Cells and Tumor-Associated Macrophages

In the tumor microenvironment, tumor-associated macrophages (TAMs) are one of the most abundant cell populations, playing key roles in tumorigenesis, chemoresistance, immune evasion, and metastasis. There is an important interaction between TAMs and cancer cells: on the one hand, tumors control the function of infiltrating macrophages, contributing to reprogramming of TAMs, and on the other hand, TAMs affect the growth of cancer cells. This review focuses on lipid metabolism changes in the complex relationship between cancer cells and TAMs. We discuss how lipid metabolism in cancer cells affects macrophage phenotypic and metabolic changes and, subsequently, how altered lipid metabolism of TAMs influences tumor progression. Identifying the metabolic changes that influence the complex interaction between tumor cells and TAMs is also an important step in exploring new therapeutic approaches that target metabolic reprogramming of immune cells to enhance their tumoricidal potential and bypass therapy resistance. Our work may provide new targets for antitumor therapies.

Lipid metabolism in malignant tumor brain metastasis: reprogramming and therapeutic potential

INTRODUCTION

Brain metastasis is a highly traumatic event in the progression of malignant tumors, often symbolizing higher mortality. Metabolic alterations are hallmarks of cancer, and the mask of lipid metabolic program rearrangement in cancer progression is gradually being unraveled.

AREAS COVERED

In this work, we reviewed clinical and fundamental studies related to lipid expression and activity changes in brain metastases originating from lung, breast, and cutaneous melanomas, respectively. Novel roles of lipid metabolic reprogramming in the development of brain metastasis from malignant tumors were identified and its potential as a therapeutic target was evaluated. Published literature and clinical studies in databases consisting of PubMed, Embase, Scopus and www.ClinicalTrials.gov from 1990 to 2022 were searched.

EXPERT OPINION

Lipid metabolic reprogramming in brain metastasis is involved in de novo lipid synthesis within low lipid availability environments, regulation of lipid uptake and storage, metabolic interactions between brain tumors and the brain microenvironment, and membrane lipid remodeling, in addition to being a second messenger for signal transduction. Although some lipid metabolism modulators work efficiently in preclinical models, there is still a long way to go from laboratory to clinic. This area of research holds assurance for the organ-targeted treatment of brain metastases through drug-regulated metabolic targets and dietary interventions.

Targeting fatty acid oxidation via Acyl-CoA binding protein hinders glioblastoma invasion

The diffuse nature of Glioblastoma (GBM) tumors poses a challenge to current therapeutic options. We have previously shown that Acyl-CoA Binding Protein (ACBP, also known as DBI) regulates lipid metabolism in GBM cells, favoring fatty acid oxidation (FAO). Here we show that ACBP downregulation results in wide transcriptional changes affecting invasion-related genes. In vivo experiments using patient-derived xenografts combined with in vitro models demonstrated that ACBP sustains GBM invasion via binding to fatty acyl-CoAs. Blocking FAO mimics ACBP^KD-induced immobility, a cellular phenotype that can be rescued by increasing FAO rates. Further investigation into ACBP-downstream pathways served to identify Integrin beta-1, a gene downregulated upon inhibition of either ACBP expression or FAO rates, as a mediator for ACBP's role in GBM invasion. Altogether, our findings highlight a role for FAO in GBM invasion and reveal ACBP as a therapeutic vulnerability to stall FAO and subsequent cell invasion in GBM tumors.

4-Hydroxynonenal Modulates Blood-Brain Barrier Permeability In Vitro through Changes in Lipid Composition and Oxidative Status of Endothelial Cells and Astrocytes

Blood brain barrier (BBB) is a dynamic interface responsible for proper functioning of brain, but also a major obstacle for effective treatment of neurological diseases. Increased levels of free radicals, in high ferrous and high lipid content surrounding, induce lipid peroxidation, leading to production of 4-hydroxynonenal (HNE). HNE modifies all key proteins responsible for proper brain functioning thus playing a major role in the onset of neurological diseases. To investigate HNE effects on BBB permeability, we developed two in vitro BBB models-'physiological' and 'pathological'. The latter mimicked HNE modified extracellular matrix under oxidative stress conditions in brain pathologies. We showed that exogenous HNE induce activation of antioxidative defense systems by increasing catalase activity and glutathione content as well as reducing lipid peroxide levels in endothelial cells and astrocytes of 'physiological' model. While in 'pathological' model, exogenous HNE further increased lipid peroxidation levels of endothelial cells and astrocytes, followed by increase in Nrf2 and glutathione levels in endothelial cells. At lipid composition level, HNE caused increase in ω3 polyunsaturated fatty acid (PUFA) level in endothelial cells, followed by decrease in ω3 PUFA level and increase in monounsaturated fatty acid level in astrocytes. Using these models, we showed for the first time that HNE in 'pathological' model can reduce BBB permeability.

Exploring the Role of Lipid-Binding Proteins and Oxidative Stress in Neurodegenerative Disorders: A Focus on the Neuroprotective Effects of Nutraceutical Supplementation and Physical Exercise

The human brain is primarily composed of lipids, and their homeostasis is crucial to carry on normal neuronal functions. In order to provide an adequate amount of lipid transport in and out of the central nervous system, organisms need a set of proteins able to bind them. Therefore, alterations in the structure or function of lipid-binding proteins negatively affect brain homeostasis, as well as increase inflammation and oxidative stress with the consequent risk of neurodegeneration. In this regard, lifestyle changes seem to be protective against neurodegenerative processes. Nutraceutical supplementation with antioxidant molecules has proven to be useful in proving cognitive functions. Additionally, regular physical activity seems to protect neuronal vitality and increases antioxidant defenses. The aim of the present review was to investigate mechanisms that link lipid-binding protein dysfunction and oxidative stress to cognitive decline, also underlining the neuroprotective effects of diet and exercise.

Fatty Acid-Binding Proteins in Psoriasis-A Review

Psoriasis is one of the most common skin diseases in dermatological practice. It affects about 1–3% of the general population and is associated with different comorbidities, especially metabolic syndrome. Fatty-acid-binding proteins (FABPs) are a family of cytosolic proteins which are an important link in lipid metabolism and transport; moreover, they have different tissue specificity and properties. So far, ten FABPs have been discovered and seven have been investigated in psoriasis. In this review, we discuss the nature of all FABPs and their role in psoriasis. FABPs have different organ and tissue expression, and hence various functions, and may be markers of different disorders. Considering the concentration of a few of them tends to be elevated in psoriasis, it confirms the current perception of psoriasis as a multiorgan disorder associated with plenty of comorbidities. Some FABPs may be also further investigated as biomarkers of psoriasis organ complications. FABP-1 and FABP-5 may become potential markers of metabolic complications and inflammation in psoriasis. FABP-7 could perhaps be further investigated as an indicator of the neurodegenerative processes in psoriatic patients.

Current knowledge of protein palmitoylation in gliomas

Malignant tumor cells can obtain proliferative benefits from deviant metabolic networks. Emerging evidence suggests that lipid metabolism are dramatically altered in gliomas and excessive fatty acd accumulation is detrimentally correlated with the prognosis of glioma patients. Glioma cells possess remarkably high levels of free fatty acids, which, in turn, enhance post-translational modifications (e.g. palmitoylation). Our and other groups found that palmitoylational modification is essential for remaining intracellular homeostasis and cell survival. Disrupting the balance between palmitoylation and depalmitoylation affects glioma cell viability, apoptosis, invasion, self-renew and pyroptosis. In this review, we focused on summarizing roles and relevant mechanisms of protein palmitoylational modification in gliomas.

Intestinal fatty acid binding protein: A rising therapeutic target in lipid metabolism

Fatty acid binding proteins (FABPs) are key proteins in lipid transport, and the isoforms are segregated according to their tissue origins. Several isoforms, such as adipose-FABP and epidermal-FABP, have been shown to participate in multiple pathologic processes due to their ubiquitous expression. Intestinal fatty acid binding protein, also termed FABP2 or I-FABP, is specifically expressed in the small intestine. FABP2 can traffic lipids from the intestinal lumen to enterocytes and bind superfluous fatty acids to maintain a steady pool of fatty acids in the epithelium. As a lipid chaperone, FABP2 can also carry lipophilic drugs to facilitate targeted transport. When the integrity of the intestinal epithelium is disrupted, FABP2 is released into the circulation. Thus, it can potentially serve as a clinical biomarker. In this review, we discuss the pivotal role of FABP2 in intestinal lipid metabolism. We also summarize the molecular interactions that have been reported to date, highlighting the clinical prospects of FABP2 research.

A Dichotomous Role for FABP7 in Sleep and Alzheimer's Disease Pathogenesis: A Hypothesis

Fatty acid binding proteins (FABPs) are a family of intracellular lipid chaperone proteins known to play critical roles in the regulation of fatty acid uptake and transport as well as gene expression. Brain-type fatty acid binding protein (FABP7) is enriched in astrocytes and has been implicated in sleep/wake regulation and neurodegenerative diseases; however, the precise mechanisms underlying the role of FABP7 in these biological processes remain unclear. FABP7 binds to both arachidonic acid (AA) and docosahexaenoic acid (DHA), resulting in discrete physiological responses. Here, we propose a dichotomous role for FABP7 in which ligand type determines the subcellular translocation of fatty acids, either promoting wakefulness aligned with Alzheimer's pathogenesis or promoting sleep with concomitant activation of anti-inflammatory pathways and neuroprotection. We hypothesize that FABP7-mediated translocation of AA to the endoplasmic reticulum of astrocytes increases astrogliosis, impedes glutamatergic uptake, and enhances wakefulness and inflammatory pathways via COX-2 dependent generation of pro-inflammatory prostaglandins. Conversely, we propose that FABP7-mediated translocation of DHA to the nucleus stabilizes astrocyte-neuron lactate shuttle dynamics, preserves glutamatergic uptake, and promotes sleep by activating anti-inflammatory pathways through the peroxisome proliferator-activated receptor-γ transcriptional cascade. Importantly, this model generates several testable hypotheses applicable to other neurodegenerative diseases, including amyotrophic lateral sclerosis and Parkinson's disease.

Identification of FABP7 as a Potential Biomarker for Predicting Prognosis and Antiangiogenic Drug Efficacy of Glioma

Objective

Glioma is a common malignant tumor of the central nervous system with extremely poor prognosis. An efficient molecular marker for diagnosis and treatment is urgently needed. Fatty acid binding protein 7(FABP7), which regulates intracellular lipid metabolism, is highly expressed in nervous system tumors, but its prognostic value remains undetermined. The present study investigated the relationship between FABP7 expression and prognosis in glioma patients by bioinformatics analysis, as well as immunohistochemically evaluating the effect of FABP7 expression on the efficacy of antiangiogenic drugs.

Methods

Gene expression and clinical data on patients with glioma were collected from the China Glioma Genome Atlas (CGGA) database, The Cancer Genome Atlas (TCGA), and the Gene Expression Omnibus (GEO) databases. Levels of FABP7 expression and their association with the clinicopathologic characteristics of glioma patients were analyzed in the CGGA database. The relationships between FABP7 expression and clinical findings, such as survival and prognostic, were determined and used for nomogram construction. Mechanisms of action of FABP7 were assessed using GSEA software. FABP7 expression in the tissues of glioma patients treated with apatinib was evaluated immunohistochemically.

Results

FABP7 was highly expressed in glioma samples, with higher FABP7 expression associated with poorer patient prognosis and more advanced clinicopathological features. Bioinformatics analysis, including survival, receiver operating characteristic curve, and univariate and multivariate Cox analyses, showed that FABP7 was independently prognostic of outcomes in glioma patients. GSEA analysis showed that FABP7 was associated with angiogenesis, with FABP7 having correlation coefficients > 0.4 with seven factors in the angiogenic pathway, POSTN, TIMP1, PDGFA, FGFR1, S100A4, COL5A2, and STC1, and the expression of these factors related to patient prognosis. Immunohistochemistry showed that FABP7 expression was higher in glioma patients with poor survival after apatinib treatment.

Conclusions

High FABP7 expression is associated with poor prognosis in glioma patients. FABP7, which is important for glioma angiogenesis, may serve as an independent prognostic predictor in glioma patients.

Unconventional Protein Secretion in Brain Tumors Biology: Enlightening the Mechanisms for Tumor Survival and Progression

Non-canonical secretion pathways, collectively known as unconventional protein secretion (UPS), are alternative secretory mechanisms usually associated with stress-inducing conditions. UPS allows proteins that lack a signal peptide to be secreted, avoiding the conventional endoplasmic reticulum-Golgi complex secretory pathway. Molecules that generally rely on the canonical pathway to be secreted may also use the Golgi bypass, one of the unconventional routes, to reach the extracellular space. UPS studies have been increasingly growing in the literature, including its implication in the biology of several diseases. Intercellular communication between brain tumor cells and the tumor microenvironment is orchestrated by various molecules, including canonical and non-canonical secreted proteins that modulate tumor growth, proliferation, and invasion. Adult brain tumors such as gliomas, which are aggressive and fatal cancers with a dismal prognosis, could exploit UPS mechanisms to communicate with their microenvironment. Herein, we provide functional insights into the UPS machinery in the context of tumor biology, with a particular focus on the secreted proteins by alternative routes as key regulators in the maintenance of brain tumors.

Polyunsaturated Fatty Acid-Enriched Lipid Fingerprint of Glioblastoma Proliferative Regions Is Differentially Regulated According to Glioblastoma Molecular Subtype

Glioblastoma (GBM) represents one of the deadliest tumors owing to a lack of effective treatments. The adverse outcomes are worsened by high rates of treatment discontinuation, caused by the severe side effects of temozolomide (TMZ), the reference treatment. Therefore, understanding TMZ’s effects on GBM and healthy brain tissue could reveal new approaches to address chemotherapy side effects. In this context, we have previously demonstrated the membrane lipidome is highly cell type-specific and very sensitive to pathophysiological states. However, little remains known as to how membrane lipids participate in GBM onset and progression. Hence, we employed an ex vivo model to assess the impact of TMZ treatment on healthy and GBM lipidome, which was established through imaging mass spectrometry techniques. This approach revealed that bioactive lipid metabolic hubs (phosphatidylinositol and phosphatidylethanolamine plasmalogen species) were altered in healthy brain tissue treated with TMZ. To better understand these changes, we interrogated RNA expression and DNA methylation datasets of the Cancer Genome Atlas database. The results enabled GBM subtypes and patient survival to be linked with the expression of enzymes accounting for the observed lipidome, thus proving that exploring the lipid changes could reveal promising therapeutic approaches for GBM, and ways to ameliorate TMZ side effects.

Fatty Acids, CD36, Thrombospondin-1, and CD47 in Glioblastoma: Together and/or Separately?

Glioblastoma (GBM) is one of the most aggressive tumors of the central nervous system, characterized by a wide range of inter- and intratumor heterogeneity. Accumulation of fatty acids (FA) metabolites was associated with a low survival rate in high-grade glioma patients. The diversity of brain lipids, especially polyunsaturated fatty acids (PUFAs), is greater than in all other organs and several classes of proteins, such as FA transport proteins (FATPs), and FA translocases are considered principal candidates for PUFAs transport through BBB and delivery of PUFAs to brain cells. Among these, the CD36 FA translocase promotes long-chain FA uptake as well as oxidated lipoproteins. Moreover, CD36 binds and recognizes thrombospondin-1 (TSP-1), an extracellular matrix protein that was shown to play a multifaceted role in cancer as part of the tumor microenvironment. Effects on tumor cells are mediated by TSP-1 through the interaction with CD36 as well as CD47, a member of the immunoglobulin superfamily. TSP-1/CD47 interactions have an important role in the modulation of glioma cell invasion and angiogenesis in GBM. Separately, FA, the two membrane receptors CD36, CD47, and their joint ligand TSP-1 all play a part in GBM pathogenesis. The last research has put in light their interconnection/interrelationship in order to exert a cumulative effect in the modulation of the GBM molecular network.

Hepatic transcriptome analysis identifies genes, polymorphisms and pathways involved in the fatty acids metabolism in sheep

Fatty acids (FA) in ruminants, especially unsaturated FA (USFA) have important impact in meat quality, nutritional value, and flavour quality of meat, and on consumer’s health. Identification of the genetic factors controlling the FA composition and metabolism is pivotal to select sheep that produce higher USFA and lower saturated (SFA) for the benefit of sheep industry and consumers. Therefore, this study was aimed to investigate the transcriptome profiling in the liver tissues collected from sheep with divergent USFA content in longissimus muscle using RNA deep-sequencing. From sheep (n = 100) population, liver tissues with higher (n = 3) and lower (n = 3) USFA content were analysed using Illumina HiSeq 2500. The total number of reads produced for each liver sample were ranged from 21.28 to 28.51 million with a median of 23.90 million. Approximately, 198 genes were differentially regulated with significance level of p-adjusted value <0.05. Among them, 100 genes were up-regulated, and 98 were down-regulated (p<0.01, FC>1.5) in the higher USFA group. A large proportion of key genes involved in FA biosynthesis, adipogenesis, fat deposition, and lipid metabolism were identified, such as APOA5, SLC25A30, GFPT1, LEPR, TGFBR2, FABP7, GSTCD, and CYP17A. Pathway analysis revealed that glycosaminoglycan biosynthesis- keratan sulfate, adipokine signaling, galactose metabolism, endocrine and other factors-regulating calcium metabolism, mineral metabolism, and PPAR signaling pathway were playing important regulatory roles in FA metabolism. Importantly, polymorphism and association analyses showed that mutation in APOA5, CFHR5, TGFBR2 and LEPR genes could be potential markers for the FA composition in sheep. These polymorphisms and transcriptome networks controlling the FA variation could be used as genetic markers for FA composition-related traits improvement. However, functional validation is required to confirm the effect of these SNPs in other sheep population in order to incorporate them in the sheep breeding program.

Inhibition of FABP6 Reduces Tumor Cell Invasion and Angiogenesis through the Decrease in MMP-2 and VEGF in Human Glioblastoma Cells

Malignant glioma is one of the most lethal cancers with rapid progression, high recurrence, and poor prognosis in the central nervous system. Fatty acid-binding protein 6 (FABP6) is a bile acid carrier protein that is overexpressed in colorectal cancer. This study aimed to assess the involvement of FABP6 expression in the progression of malignant glioma. Immunohistochemical analysis revealed that FABP6 expression was higher in glioma than in normal brain tissue. After the knockdown of FABP6, a decrease in the migration and invasion abilities of glioma cells was observed. The phosphorylation of the myosin light chain was inhibited, which may be associated with migration ability. Moreover, expression levels of invasion-related proteins, matrix metalloproteinase-2 (MMP-2) and cathepsin B, were reduced. Furthermore, tube formation was inhibited in the human umbilical vein endothelial cells with a decreased concentration of vascular endothelial growth factor (VEGF) in the conditioned medium after the knockdown of FABP6. The phosphorylation of the extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p65 were also decreased after FABP6 reduction. Finally, the bioluminescent images and immunostaining of MMP-2, cluster of differentiation 31 (CD31), and the VEGF receptor 1 (VEGFR1) revealed attenuated tumor progression in the combination of the FABP6-knocked-down and temozolomide (TMZ)-treated group in an orthotopic xenograft mouse tumor model. This is the first study that revealed the impact of FABP6 on the invasion, angiogenesis, and progression of glioma. The results of this study show that FABP6 may be a potential therapeutic target combined with TMZ for malignant gliomas.

FABP7 Facilitates Uptake of Docosahexaenoic Acid in Glioblastoma Neural Stem-like Cells

Glioblastoma (GBM) is an aggressive tumor with a dismal prognosis. Neural stem-like cells contribute to GBM's poor prognosis by driving drug resistance and maintaining cellular heterogeneity. GBM neural stem-like cells express high levels of brain fatty acid-binding protein (FABP7), which binds to polyunsaturated fatty acids (PUFAs) ω-6 arachidonic acid (AA) and ω-3 docosahexaenoic acid (DHA). Similar to brain, GBM tissue is enriched in AA and DHA. However, DHA levels are considerably lower in GBM tissue compared to adult brain. Therefore, it is possible that increasing DHA content in GBM, particularly in neural stem-like cells, might have therapeutic value. Here, we examine the fatty acid composition of patient-derived GBM neural stem-like cells grown as neurosphere cultures. We also investigate the effect of AA and DHA treatment on the fatty acid profiles of GBM neural stem-like cells with or without FABP7 knockdown. We show that DHA treatment increases DHA levels and the DHA:AA ratio in GBM neural stem-like cells, with FABP7 facilitating the DHA uptake. We also found that an increased uptake of DHA inhibits the migration of GBM neural stem-like cells. Our results suggest that increasing DHA content in the GBM microenvironment may reduce the migration/infiltration of FABP7-expressing neural stem-like cancer cells.

Metabolic Remodeling in Glioma Immune Microenvironment: Intercellular Interactions Distinct From Peripheral Tumors

During metabolic reprogramming, glioma cells and their initiating cells efficiently utilized carbohydrates, lipids and amino acids in the hypoxic lesions, which not only ensured sufficient energy for rapid growth and improved the migration to normal brain tissues, but also altered the role of immune cells in tumor microenvironment. Glioma cells secreted interferential metabolites or depriving nutrients to injure the tumor recognition, phagocytosis and lysis of glioma-associated microglia/macrophages (GAMs), cytotoxic T lymphocytes, natural killer cells and dendritic cells, promoted the expansion and infiltration of immunosuppressive regulatory T cells and myeloid-derived suppressor cells, and conferred immune silencing phenotypes on GAMs and dendritic cells. The overexpressed metabolic enzymes also increased the secretion of chemokines to attract neutrophils, regulatory T cells, GAMs, and dendritic cells, while weakening the recruitment of cytotoxic T lymphocytes and natural killer cells, which activated anti-inflammatory and tolerant mechanisms and hindered anti-tumor responses. Therefore, brain-targeted metabolic therapy may improve glioma immunity. This review will clarify the metabolic properties of glioma cells and their interactions with tumor microenvironment immunity, and discuss the application strategies of metabolic therapy in glioma immune silence and escape.

Super resolution microscopy reveals DHA-dependent alterations in glioblastoma membrane remodelling and cell migration

Brain fatty acid binding protein (FABP7; B-FABP) promotes glioblastoma (GBM) cell migration and is associated with tumor infiltration, properties associated with a poor prognosis in GBM patients. FABP7-expressing neural stem-like cells are known to drive tumor migration/infiltration and resistance to treatment. We have previously shown that FABP7's effects on cell migration can be reversed when GBM cells are cultured in medium supplemented with the omega-3 fatty acid, docosahexaenoic acid (DHA). Here, we use super-resolution imaging on patient-derived GBM stem-like cells to examine the importance of FABP7 and its fatty acid ligands in mitigating GBM cell migration. As FABPs are involved in fatty acid transport from membrane to cytosol, we focus on the effect of FABP7 and its ligand DHA on GBM membrane remodeling, as well as FABP7 nanoscale domain formation on GBM membrane. Using quantitative plasma membrane lipid order imaging, we show that FABP7 expression in GBM cells correlates with increased membrane lipid order, with DHA dramatically decreasing lipid order. Using super-resolution stimulated emission depletion (STED) microscopy, we observe non-uniform distribution of FABP7 on the surface of GBM cells, with FABP7 forming punctate nanoscale domains of ∼100 nm in diameter. These nanodomains are particularly enriched at the migrating front of GBM cells. Interestingly, FABP7 nanodomains are disrupted when GBM cells are cultured in DHA-supplemented medium. We demonstrate a tight link between cell migration, a higher membrane lipid order and increased FABP7 nanoscale domains. We propose that DHA-mediated disruption of membrane lipid order and FABP7 nanodomains forms the basis of FABP7/DHA-mediated inhibition of cell migration in GBM.

Omega-3 effects on electrocorticographic patterns of adult Wistar rats exposed to ionizing radiation

This study aimed to assess the effect of supplementation with omega-3 in Wistar rats exposed to ionizing radiation in a dose of 18 Gy on the cortical electrical activity, using mathematical methods such as the power spectrum (PS) and the detrended fluctuation analysis (DFA) in the evaluation of the electrocorticogram (ECoG) record. The PS analysis showed that in non-irradiated animals but supplemented with omega-3 there was a decrease in the power of the beta rhythm, while the DFA applied to different frequency ranges of the ECoG showed a significant increase in the long-range correlation only for the theta wave when compared with non-supplemented animals. In the evaluation of the radiation effect through the PS, an increase in the power of the theta rhythm was observed in both groups (non-supplemented and supplemented animals) only when they were evaluated one week after irradiation. The DFA method also showed difference in this wave. The PS and DFA methods applied to the ECoG record allowed a quantitative analysis of the cortical electrical activity in rats in response to the omega-3 effects, ionizing radiation, or both.

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PUFA omega-3 can act as a modulator of the cortical activity in rats.

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Ionizing radiation exposure promoted later effect in theta and beta waves.

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3. The power spectrum and the DFA allowed a quantitative analysis of the ECoG in rats.

M2 macrophage-derived exosomal microRNAs inhibit cell migration and invasion in gliomas through PI3K/AKT/mTOR signaling pathway

Background

Glioma, the most common primary brain tumor, account Preparing figures for 30 to 40% of all intracranial tumors. Herein, we aimed to study the effects of M2 macrophage-derived exosomal microRNAs (miRNAs) on glioma cells.

Methods

First, we identified seven differentially expressed miRNAs in infiltrating macrophages and detected the expression of these seven miRNAs in M2 macrophages. We then selected hsa-miR-15a-5p (miR-15a) and hsa-miR-92a-3p (miR-92a) for follow-up studies, and confirmed that miR-15a and miR-92a were under-expressed in M2 macrophage exosomes. Subsequently, we demonstrated that M2 macrophage-derived exosomes promoted migration and invasion of glioma cells, while exosomal miR-15a and miR-92a had the opposite effects on glioma cells. Next, we performed the target gene prediction in four databases and conducted target gene validation by qRT-PCR, western blot and dual luciferase reporter gene assays.

Results

The results revealed that miR-15a and miR-92a were bound to CCND1 and RAP1B, respectively. Western blot assays demonstrated that interference with the expression of CCND1 or RAP1B reduced the phosphorylation level of AKT and mTOR, indicating that both CCND1 and RAP1B can activate the PI3K/AKT/mTOR signaling pathway.

Conclusion

Collectively, these findings indicate that M2 macrophage-derived exosomal miR-15a and miR-92a inhibit cell migration and invasion of glioma cells through PI3K/AKT/mTOR signaling pathway.

Supplementary information

The online version contains supplementary material available at 10.1186/s12967-021-02766-w.

Identification of Core Genes and Screening of Potential Targets in Glioblastoma Multiforme by Integrated Bioinformatic Analysis

Glioblastoma multiforme is the most common primary intracranial malignancy, but its etiology and pathogenesis are still unclear. With the deepening of human genome research, the research of glioma subtype screening based on core molecules has become more in-depth. In the present study, we screened out differentially expressed genes (DEGs) through reanalyzing the glioblastoma multiforme (GBM) datasets GSE90598 from the Gene Expression Omnibus (GEO), the GBM dataset TCGA-GBM and the low-grade glioma (LGG) dataset TCGA-LGG from the Cancer Genome Atlas (TCGA). A total of 150 intersecting DEGs were found, of which 48 were upregulated and 102 were downregulated. These DEGs from GSE90598 dataset were enriched using the overrepresentation method, and multiple enriched gene ontology (GO) function terms were significantly correlated with neural cell signal transduction. DEGs between GBM and LGG were analyzed by gene set enrichment analysis (GSEA), and the significantly enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways involved in synapse signaling and oxytocin signaling pathways. Then, a protein-protein interaction (PPI) network was constructed to assess the interaction of proteins encoded by the DEGs. MCODE identified 2 modules from the PPI network. The 11 genes with the highest degrees in module 1 were designated as core molecules, namely, GABRD, KCNC1, KCNA1, SYT1, CACNG3, OPALIN, CD163, HPCAL4, ANK3, KIF5A, and MS4A6A, which were mainly enriched in ionic signaling-related pathways. Survival analysis of the GSE83300 dataset verified the significant relationship between expression levels of the 11 core genes and survival. Finally, the core molecules of GBM and the DrugBank database were assessed by a hypergeometric test to identify 10 drugs included tetrachlorodecaoxide related to cancer and neuropsychiatric diseases. Further studies are required to explore these core genes for their potentiality in diagnosis, prognosis, and targeted therapy and explain the relationship among ionic signaling-related pathways, neuropsychiatric diseases and neurological tumors.

[A Review of the Lipid Metabolism Reprogramming in Tumor Associated Macrophages]

Tumor associated macrophages (TAMs) are one of the most common types of stromal cells in solid tumors. They are closely related to the immunosuppressive status of tumor microenvironment and potentiate the malignant progress of tumors. Studies have shown that metabolism in tumor associated macrophages has been reprogrammed and involved in the regulation of their own polarization and corresponding functions and phenotypes. Metabolic reprogramming refers to the alteration of key enzymes activity, substrate and its associated metabolites' concentration in a certain metabolic pathway, which accounts for the disorder of original metabolic states. In this paper, we mainly concentrated on the lipid metabolic reprogramming of TAMs, including triglycerides, fatty acids and their derivatives, cholesterol, phospholipids, and their regulations on tumor progression. However, the metabolism of tumor and tumor microenvironment cells is highly heterogeneous. It is worthy of further exploration on the similarities and differences of lipid metabolism reprogramming between stromal cells and tumor cells, and the mechanism of how reprogramming modulates cell activity. It will be a new strategy for immunotherapy of tumor with metabolic intervention to accurately target the lipid metabolism reprogramming of TAMs, so as to promote the polarization of TAMs to M1 like macrophages, when synthetically considering the diverse types of tumors and different stages of development.

An Amplified Fatty Acid-Binding Protein Gene Cluster in Prostate Cancer: Emerging Roles in Lipid Metabolism and Metastasis

Treatment for early stage and localized prostate cancer (PCa) is highly effective. Patient survival, however, drops dramatically upon metastasis due to drug resistance and cancer recurrence. The molecular mechanisms underlying PCa metastasis are complex and remain unclear. It is therefore crucial to decipher the key genetic alterations and relevant molecular pathways driving PCa metastatic progression so that predictive biomarkers and precise therapeutic targets can be developed. Through PCa cohort analysis, we found that a fatty acid-binding protein (FABP) gene cluster (containing five FABP family members) is preferentially amplified and overexpressed in metastatic PCa. All five FABP genes reside on chromosome 8 at 8q21.13, a chromosomal region frequently amplified in PCa. There is emerging evidence that these FABPs promote metastasis through distinct biological actions and molecular pathways. In this review, we discuss how these FABPs may serve as drivers/promoters for PCa metastatic transformation using patient cohort analysis combined with a review of the literature.

Non-Coding and Regulatory RNAs as Epigenetic Remodelers of Fatty Acid Homeostasis in Cancer

Cancer cells commonly display metabolic fluctuations. Together with the Warburg effect and the increased glutaminolysis, alterations in lipid metabolism homeostasis have been recognized as a hallmark of cancer. Highly proliferative cancer cells upregulate de novo synthesis of fatty acids (FAs) which are required to support tumor progression by exerting multiple roles including structural cell membrane composition, regulators of the intracellular redox homeostasis, ATP synthesis, intracellular cell signaling molecules, and extracellular mediators of the tumor microenvironment. Epigenetic modifications have been shown to play a crucial role in human development, but also in the initiation and progression of complex diseases. The study of epigenetic processes could help to design new integral strategies for the prevention and treatment of metabolic disorders including cancer. Herein, we first describe the main altered intracellular fatty acid processes to support cancer initiation and progression. Next, we focus on the most important regulatory and non-coding RNAs (small noncoding RNA-sncRNAs-long non-coding RNAs-lncRNAs-and other regulatory RNAs) which may target the altered fatty acids pathway in cancer.

Fatty acid binding protein 7 mediates linoleic acid-induced cell death in triple negative breast cancer cells by modulating 13-HODE

Different fatty acids have distinct effects on the survival of breast cancer cells, which could be mediated by fatty acid binding proteins (FABPs), a family of lipid chaperones. Due to the diverse structures of the members of FABP family, each FABP demonstrates distinct binding affinities to different fatty acids. Of note, FABP7 is predominantly expressed in triple negative breast cancer (TNBC), the most aggressive subtype of breast cancer. Yet, the role of FABP7 in modulating the effects of fatty acids on TNBC survival was unclear. In contrast to the high expression of FABP7 in human TNBC tumours, FABP7 protein was undetectable in TNBC cell lines. Hence, a FABP7 overexpression model was used for this study, in which the transduced TNBC cell lines (MDA-MB-231 and Hs578T) were treated with various mono- and polyunsaturated fatty acids. Oleic acid (OA), docosahexaenoic acid (DHA) and arachidonic acid (AA) inhibited TNBC cell growth at high concentrations, with no differences resulted from FABP7 overexpression. Interestingly, overexpression of FABP7 augmented linoleic acid-induced cell death in MDA-MB-231 cells. The increased cell death may be explained by a decrease in 13-HODE, a pro-tumorigenic oxidation product of linoleic acid. The phenotype was, however, attenuated with a rescue treatment using 25 nM 13-HODE. The decrease in 13-HODE was potentially due to fatty acid partitioning modulated by FABP7, as demonstrated by a 3-fold increase in fatty acid oxidation. Our findings suggest that linoleic acid could be a potential therapeutic strategy for FABP7-overexpressing TNBC patients.

Disruption of hypoxia-inducible fatty acid binding protein 7 induces beige fat-like differentiation and thermogenesis in breast cancer cells

BACKGROUND

Humans produce heat through non-shivering thermogenesis, a metabolic process that occurs in inducible beige adipocytes expressing uncoupling protein 1 (UCP1). UCP1 dissipates the proton gradient of the mitochondrial inner membrane and converts that energy into heat. It is unclear whether cancer cells can exhibit autonomous thermogenesis. Previously, we found that the knockdown of hypoxia-inducible fatty acid binding protein 7 (FABP7) increased reactive oxygen species (ROS) in breast cancer cells. ROS are known to induce beige adipocyte differentiation.

METHODS

We investigated the association of tumor hypoxia, FABP7, and UCP1 across breast cancer patients using METABRIC and TCGA data sets. Furthermore, using a breast cancer cell line, HCC1806, we tested the effect of FABP7 knockdown on cellular physiology including thermogenesis.

RESULTS

We found a strong mutual exclusivity of FABP7 and UCP1 expression both in METABRIC and in TCGA, indicating major metabolic phenotypic differences. FABP7 was preferentially distributed in poorly differentiated-, estrogen receptor (ER) negative tumors. In contrast, UCP1 was highly expressed in normal ducts and well-differentiated-, ER positive-, less hypoxic tumors. In the cell line-based experiments, UCP1 and its transcriptional regulators were upregulated upon FABP7 knockdown. UCP1 was induced in about 20% of cancer cells, and the effect was increased further in hypoxia. UCP1 depolarized mitochondrial membranes at the site of expression. UCP1 induction was associated with the increase in proton leak, glycolysis, and maximal respiration, mimicking the typical energy profile of beige adipocytes. Most importantly, UCP1 induction elevated cancer cell temperature associated with increased vulnerability to hypoxia and γ-irradiation.

CONCLUSIONS

We demonstrated that breast cancer cells can undergo thermogenesis through UCP1 induction. Disrupting FABP7-mediated fatty acid metabolism can unlock UCP1-mediated thermogenesis, potentially making it possible to develop therapies to target thermogenesis. Further study would be warranted to investigate the effect of rise in temperature of cancer cells on patients' outcomes and the relationship to other metabolic pathways.

FABP7 upregulation induces a neurotoxic phenotype in astrocytes

Fatty acid binding proteins (FABPs) are key regulators of lipid metabolism, energy homeostasis, and inflammation. They participate in fatty acid metabolism by regulating their uptake, transport, and availability of ligands to nuclear receptors. In the adult brain, FABP7 is especially abundant in astrocytes that are rich in cytoplasmic granules originated from damaged mitochondria. Mitochondrial dysfunction and oxidative stress have been implicated in the neurodegenerative process observed in amyotrophic lateral sclerosis (ALS), either as a primary cause or as a secondary component of the pathogenic process. Here we investigated the expression of FABP7 in animal models of human superoxide dismutase 1 (hSOD1)-linked ALS. In the spinal cord of symptomatic mutant hSOD1-expressing mice, FABP7 is upregulated in gray matter astrocytes. Using a coculture model, we examined the effect of increased FABP7 expression in astrocyte-motor neuron interaction. Our data show that FABP7 overexpression directly promotes an NF-κB-driven pro-inflammatory response in nontransgenic astrocytes that ultimately is detrimental for motor neuron survival. Addition of trophic factors, capable of supporting motor neuron survival in pure cultures, did not prevent motor neuron loss in cocultures with FABP7 overexpressing astrocytes. In addition, astrocyte cultures obtained from symptomatic hSOD1-expressing mice display upregulated FABP7 expression. Silencing endogenous FABP7 in these cultures decreases the expression of inflammatory markers and their toxicity toward cocultured motor neurons. Our results identify a key role of FABP7 in the regulation of the inflammatory response in astrocytes and identify FABP7 as a potential therapeutic target to prevent astrocyte-mediated motor neuron toxicity in ALS.

FADS1 promotes the progression of laryngeal squamous cell carcinoma through activating AKT/mTOR signaling

Metabolic abnormality is the major feature of laryngeal squamous cell carcinoma (LSCC), however, the underlying mechanism remain largely elusive. Fatty acid desaturase 1 (FADS1), as the key rate-limiting enzyme of polyunsaturated fatty acids (PUFAs), catalyzes dihomo-gamma-linolenic acid (DGLA) to arachidonic acid (AA). In this study, we reported that the expression of FADS1 was upregulated in LSCC, high FADS1 expression was closely associated with the advanced clinical features and poor prognosis of the recurrent LSCC patients after chemotherapy. Liquid chromatograph-mass spectrometry (LC-MS) analysis revealed that FADS1 overexpression induced greater conversion of DGLA to AA, suggesting an increased activity of FADS1. Similarly, the level of prostaglandin E2 (PGE₂), a downstream metabolite of AA, was also elevated in cancerous laryngeal tissues. Functional assays showed that FADS1 knockdown suppressed the proliferation, migration and invasion of LSCC cells, while FADS1 overexpression had the opposite effects. Bioinformatic analysis based on microarray data found that FADS1 could activate AKT/mTOR signaling. This hypothesis was further validated by both in vivo and in vitro assays. Hence, our data has supported the viewpoint that FADS1 is a potential promoter in LSCC progression, and has laid the foundation for further functional research on the PUFA dietary supplementation interventions targeting FADS1/AKT/mTOR pathway for LSCC prevention and treatment.

Proteomic profiling of fatty acid binding proteins in muscular dystrophy

Introduction: Duchenne muscular dystrophy is a neuromuscular disorder, which is caused by abnormalities in the DMD gene that encodes the membrane cytoskeletal protein dystrophin. Besides progressive skeletal muscle wasting, dystrophinopathy also affects non-skeletal muscle tissues, including cells in the cardio-respiratory system, the central nervous system, the liver and the kidney.Areas covered: This review summarizes the proteomic characterization of a key class of lipid chaperones, the large family of fatty acid binding proteins, and their potential role in muscular dystrophy. Recent proteomic surveys using animal models and patient specimens are reviewed. Pathobiochemical changes in specific proteoforms of fatty acid binding protein in the multi-system pathology of dystrophinopathy are discussed.Expert opinion: The mass spectrometric identification of distinct changes in fatty acid binding proteins in muscle, heart, liver, kidney and serum demonstrates that considerable alterations occur in key steps of metabolite transport and fat metabolism in muscular dystrophy. These new findings might be helpful to further develop a comprehensive biomarker signature of metabolic changes in X-linked muscular dystrophy, which should improve (i) our understanding of complex pathobiochemical changes due to dystrophin deficiency, (ii) the identification of novel therapeutic targets, and (iii) the design of differential diagnostic, prognostic and therapy-monitoring approaches.

Role of fatty acid binding proteins (FABPs) in cancer development and progression

Fatty acid binding proteins (FABPs) are small, water soluble proteins that bind long chain fatty acids and other biologically active ligands to facilitate intracellular localization. Twelve FABP family members have been identified to date, with 10 isoforms expressed in humans. Functionally, FABPs are important in fatty acid metabolism and transport, with distinct family members having the capacity to influence gene transcription. Expression of FABPs is usually cell/tissue specific to one predominant FABP family member. Dysregulation of FABP expression can occur through genetic mutation and/or environmental-lifestyle influences. In addition to intracellular function, exogenous, circulating FABP expression can occur and is associated with specific disease states such as insulin resistance. A role for FABPs is increasingly being reported in tumor biology with elevated exogenous FABP expression being associated with tumor progression and invasiveness. However, a less clear role has been appreciated for dysregulated FABP expression during cell transformation and early expansion.

Role of FABP7 in tumor cell signaling

Lipids are major molecules for the function of organisms and are involved in the pathophysiology of various diseases. Fatty acids (FAs) signaling and their metabolism are some of the most important pathways in tumor development, as lipids serve as energetic sources during carcinogenesis. Fatty acid binding proteins (FABPs) facilitate FAs transport to different cell organelles, modulating their metabolism along with mediating other physiological activities. FABP7, brain-typed FABP, is thought to be an important molecule for cell proliferation in healthy as well as diseased organisms. Several studies on human tumors and tumor-derived cell lines put FABP7 in the center of tumorigenesis, and its high expression level has been reported to correlate with poor prognosis in different tumor types. Several types of FABP7-expressing tumors have shown an up-regulation of cell signaling activity, but molecular mechanisms of FABP7 involvement in tumorigenesis still remain elusive. In this review, we focus on the expression and function of FABP7 in different tumors, and possible mechanisms of FABP7 in tumor proliferation and migration.

ω-3 and ω-6 Fatty Acids Modulate Conventional and Atypical Protein Kinase C Activities in a Brain Fatty Acid Binding Protein Dependent Manner in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is a highly infiltrative brain cancer with a dismal prognosis. High levels of brain fatty acid binding protein (B-FABP) are associated with increased migration/infiltration in GBM cells, with a high ratio of arachidonic acid (AA) to docosahexaenoic acid (DHA) driving B-FABP-mediated migration. Since several protein kinase Cs (PKCs) are overexpressed in GBM and linked to migration, we explored a possible relationship between B-FABP and levels/activity of different PKCs, as a function of AA and DHA supplementation. We report that ectopic expression of B-FABP in U87 cells alters the levels of several PKCs, particularly PKCζ. Upon analysis of PKCζ RNA levels in a panel of GBM cell lines and patient-derived GBM neurospheres, we observed a trend towards moderate positive correlation (r = 0.624, p = 0.054) between B-FABP and PKCζ RNA levels. Analysis of PKC activity in U87 GBM cells revealed decreased typical PKC activity (23.4%) in B-FABP-expressing cells compared with nonexpressing cells, with no difference in novel and atypical PKC activities. AA and DHA modulated both conventional and atypical PKC activities in a B-FABP-dependent manner, but had no effect on novel PKC activity. These results suggest that conventional and atypical PKCs are potential downstream effectors of B-FABP/fatty acid-mediated alterations in GBM growth properties.

Anti-Inflammatory Effects of Omega-3 Fatty Acids in the Brain: Physiological Mechanisms and Relevance to Pharmacology

Classically, polyunsaturated fatty acids (PUFA) were largely thought to be relatively inert structural components of brain, largely important for the formation of cellular membranes. Over the past 10 years, a host of bioactive lipid mediators that are enzymatically derived from arachidonic acid, the main n-6 PUFA, and docosahexaenoic acid, the main n-3 PUFA in the brain, known to regulate peripheral immune function, have been detected in the brain and shown to regulate microglia activation. Recent advances have focused on how PUFA regulate the molecular signaling of microglia, especially in the context of neuroinflammation and behavior. Several active drugs regulate brain lipid signaling and provide proof of concept for targeting the brain. Because brain lipid metabolism relies on a complex integration of diet, peripheral metabolism, including the liver and blood, which supply the brain with PUFAs that can be altered by genetics, sex, and aging, there are many pathways that can be disrupted, leading to altered brain lipid homeostasis. Brain lipid signaling pathways are altered in neurologic disorders and may be viable targets for the development of novel therapeutics. In this study, we discuss in particular how n-3 PUFAs and their metabolites regulate microglia phenotype and function to exert their anti-inflammatory and proresolving activities in the brain.

Novel strategies of Raman imaging for brain tumor research

Raman diagnostics and imaging have been shown to be an effective tool for the analysis and discrimination of human brain tumors from normal structures. Raman spectroscopic methods have potential to be applied in clinical practice as they allow for identification of tumor margins during surgery. In this study, we investigate medulloblastoma (grade IV WHO) (n= 5), low-grade astrocytoma (grades I-II WHO) (n =4), ependymoma (n=3) and metastatic brain tumors (n= 1) and the tissue from the negative margins used as normal controls. We compare a high grade medulloblastoma, low grade astrocytoma and non-tumor samples from human central nervous system (CNS) tissue. Based on the properties of the Raman vibrational features and Raman images we provide a real–time feedback method that is label-free to monitor tumor metabolism that reveals reprogramming of biosynthesis of lipids, proteins, DNA and RNA. Our results indicate marked metabolic differences between low and high grade brain tumors. We discuss molecular mechanisms causing these metabolic changes, particularly lipid alterations in malignant medulloblastoma and low grade gliomas that may shed light on the mechanisms driving tumor recurrence thereby revealing new approaches for the treatment of malignant glioma. We have found that the high-grade tumors of central nervous system (medulloblastoma) exhibit enhanced level of β-sheet conformation and down-regulated level of α-helix conformation when comparing against normal tissue. We have found that almost all tumors studied in the paper have increased Raman signals of nucleic acids. This increase can be interpreted as increased DNA/RNA turnover in brain tumors. We have shown that the ratio of Raman intensities I₂₉₃₀/I₂₈₄₅ at 2930 and 2845 cm^-1 is a good source of information on the ratio of lipid and protein contents. We have found that the ratio reflects the different lipid and protein contents of cancerous brain tissue compared to the non-tumor tissue. We found that levels of the saturated fatty acids were significantly reduced in the high grade medulloblastoma samples compared with non-tumor brain samples and low grade astrocytoma. Differences were also noted in the n-6/n-3 polyunsaturated fatty acids (PUFA) content between medulloblastoma and non-tumor brain samples. The content of the oleic acid (OA) was significantly smaller in almost all brain high grade brain tumors than that observed in the control samples. It indicates that the fatty acid composition of human brain tumors differs from that found in non-tumor brain tissue. The iodine number N_I for the normal brain tissue is 60. For comparison OA has 87, docosahexaenoic acid (DHA) 464, α-linolenic acid (ALA) 274. The high grade tumors have the iodine numbers between that for palmitic acid, stearic acid, arachidic acid (N_I=0) and oleic acid (N_I=87). Most low grade tumors have N_I similar to that of OA. The iodine number for arachidonic acid (AA) (N_I=334) is much higher than those observed for all studied samples.

Cell biology-metabolic crosstalk in glioma

The renewed interest in cancer metabolism in recent years has been fuelled by the identification of the involvement of key oncogenes and tumour suppressor genes in the control of metabolic pathways. Many of these alterations lead to dramatic changes in bioenergetics, biosynthesis and redox balance within tumour cells. The complex relationship between tumour cell metabolism and the tumour microenvironment has turned this field of biochemistry and cell biology into a challenging and exciting area for study. In the case of gliomas the involvement of altered metabolic pathways including glycolysis, oxidative phosphorylation and glutaminolysis are pointing the way to new possibilities for treatment. The tumour-promoting effects of inflammation are an emerging hallmark of cancer and the role of the eicosanoids in gliomas is an area of active research to elucidate the importance of individual eicosanoids in glioma cell proliferation, migration and immune escape. In this review, the different aspects of metabolic reprogramming which occur in gliomas are highlighted and their relationship to glioma cell biology and the wider tumour microenvironment is described.

Long-Term Effect of Docosahexaenoic Acid Feeding on Lipid Composition and Brain Fatty Acid-Binding Protein Expression in Rats

Arachidonic (AA) and docosahexaenoic acid (DHA) brain accretion is essential for brain development. The impact of DHA-rich maternal diets on offspring brain fatty acid composition has previously been studied up to the weanling stage; however, there has been no follow-up at later stages. Here, we examine the impact of DHA-rich maternal and weaning diets on brain fatty acid composition at weaning and three weeks post-weaning. We report that DHA supplementation during lactation maintains high DHA levels in the brains of pups even when they are fed a DHA-deficient diet for three weeks after weaning. We show that boosting dietary DHA levels for three weeks after weaning compensates for a maternal DHA-deficient diet during lactation. Finally, our data indicate that brain fatty acid binding protein (FABP7), a marker of neural stem cells, is down-regulated in the brains of six-week pups with a high DHA:AA ratio. We propose that elevated levels of DHA in developing brain accelerate brain maturation relative to DHA-deficient brains.

ESI-MS/MS and MALDI-IMS Localization Reveal Alterations in Phosphatidic Acid, Diacylglycerol, and DHA in Glioma Stem Cell Xenografts

Glioblastoma (GBM) is the most common adult primary brain tumor. Despite aggressive multimodal therapy, the survival of patients with GBM remains dismal. However, recent evidence has demonstrated the promise of bone marrow-derived mesenchymal stem cells (BM-hMSCs) as a therapeutic delivery vehicle for anti-glioma agents due to their ability to migrate or home to human gliomas. While several studies have demonstrated the feasibility of harnessing the homing capacity of BM-hMSCs for targeted delivery of cancer therapeutics, it is now also evident, based on clinically relevant glioma stem cell (GSC) models of GBMs, that BM-hMSCs demonstrate variable tropism toward these tumors. In this study, we compared the lipid environment of GSC xenografts that attract BM-hMSCs (N = 9) with those that do not attract (N = 9) to identify lipid modalities that are conducive to homing of BM-hMSC to GBMs. We identified lipids directly from tissue by matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) and electrospray ionization-tandem mass spectrometry (ESI-MS/MS) of lipid extracts. Several species of signaling lipids, including phosphatidic acid (PA 36:2, PA 40:5, PA 42:5, and PA 42:7) and diacylglycerol (DAG 34:0, DAG 34:1, DAG 36:1, DAG 38:4, DAG 38:6, and DAG 40:6), were lower in attracting xenografts. Molecular lipid images showed that PA (36:2), DAG (40:6), and docosahexaenoic acid (DHA) were decreased within tumor regions of attracting xenografts. Our results provide the first evidence for lipid signaling pathways and lipid-mediated tumor inflammatory responses in the homing of BM-hMSCs to GSC xenografts. Our studies provide new fundamental knowledge on the molecular correlates of the differential homing capacity of BM-hMSCs toward GSC xenografts.

Global profiling of metabolic adaptation to hypoxic stress in human glioblastoma cells

Oncogenetic events and unique phenomena of the tumor microenvironment together induce adaptive metabolic responses that may offer new diagnostic tools and therapeutic targets of cancer. Hypoxia, or low oxygen tension, represents a well-established and universal feature of the tumor microenvironment and has been linked to increased tumor aggressiveness as well as resistance to conventional oncological treatments. Previous studies have provided important insights into hypoxia induced changes of the transcriptome and proteome; however, how this translates into changes at the metabolite level remains to be defined. Here, we have investigated dynamic, time-dependent effects of hypoxia on the cancer cell metabolome across all families of macromolecules, i.e., carbohydrate, protein, lipid and nucleic acid, in human glioblastoma cells. Using GC/MS and LC/MS/MS, 345 and 126 metabolites were identified and quantified in cells and corresponding media, respectively, at short (6 h), intermediate (24 h), and prolonged (48 h) incubation at normoxic or hypoxic (1% O₂) conditions. In conjunction, we performed gene array studies with hypoxic and normoxic cells following short and prolonged incubation. We found that levels of several key metabolites varied with the duration of hypoxic stress. In some cases, metabolic changes corresponded with hypoxic regulation of key pathways at the transcriptional level. Our results provide new insights into the metabolic response of glioblastoma cells to hypoxia, which should stimulate further work aimed at targeting cancer cell adaptive mechanisms to microenvironmental stress.

Enhanced anticancer properties of lomustine in conjunction with docosahexaenoic acid in glioblastoma cell lines

OBJECT

Glioblastoma is a rapidly infiltrating tumor that consistently rematerializes despite various forms of aggressive treatment. Brain tumors are commonly treated with alkylating drugs, such as lomustine, which are chemotherapeutic agents. Use of these drugs, however, is associated with serious side effects. To reduce the side effects, one approach is to combine lower doses of chemotherapeutic drugs with other nontoxic anticancer agents. In this study, using glioblastoma cell lines, the authors investigated the anticancer effects of lomustine, alone and in combination with docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid normally abundant in the brain and known for its anticancer potential.

METHODS

Cells were cultured from 3 human-derived tumor cell lines (U87-MG, DB029, and MHBT161) and supplemented with either DHA or lomustine to determine the growth inhibitory potential using WST-1, a mitochondrial functional indicator. Human-derived cerebral cortex microvascular endothelial cells served as a normal phenotypic control. Cellular incorporation of DHA was analyzed by gas chromatography. Using flow cytometric analysis, the DHA and/or lomustine effect on induction of apoptosis and/or necrosis was quantified; subsequently, the DHA and lomustine effect on cell cycle progression was also assessed. Western blot analysis confirmed the role of downstream cellular targets.

RESULTS

U87-MG growth was inhibited with the supplementation of either DHA (ED50 68.3 μM) or lomustine (ED50 68.1 μM); however, growth inhibition was enhanced when U87-MG cells were administered equimolar doses of each compound, resulting in nearly total growth inhibition at 50 μM. Gas chromatography analysis of the fatty acid profile in DHA-supplemented U87-MG cells resulted in a linear dose-dependent increase in DHA incorporation (< 60 μM). The combination of DHA and lomustine potently induced U87-MG apoptosis and necrosis as indicated by flow cytometric analysis. Activation of caspase-3 and poly (ADP-ribose) polymerase (PARP) was evident in lomustine-treated U87-MG cells, although this activation did not appear to be dependent on DHA supplementation. Additionally, lomustine-treated cells' growth arrested in the G2/M cell cycle stage, regardless of the presence of DHA. Similar to the U87-MG observations, the combination of DHA and lomustine resulted in growth inhibition of 2 additional human-derived glioblastoma cell lines, DB029 and MHBT161. Importantly, in primary human-derived cerebral cortex endothelial cells, this combination was only growth inhibitory (40.8%) at the highest dose screened (100 μM), which indicates a certain degree of selectivity toward glioblastoma.

CONCLUSIONS

Taken together, these data suggest a potential role for a combination therapy of lomustine and DHA for the treatment of glioblastomas.