4. Discussion
GBM is incurable cancer characterized by poor survival rates and a high recurrence rate caused by glial cells that surround and support neurons. In terms of treatment resistance, complexity, and lethality, it is one of the deadliest types of cancer. Even though surgery followed by radiotherapy and chemotherapy are the standard treatments for GBM, its prognosis is dismal, with a median survival time of only 15 months [
44]
. In spite of extensive research into the pathogenesis of GBM, the disease continues to have a poor outcome due to a lack of understanding of genetic risk factors. Gene sequencing studies have made it possible to learn much more about GBM genetics and epigenetics in recent years [
45]. Identifying practical molecular biomarkers is crucial to help clinicians treat glioma patients as effectively as possible. Due to changes in miRNA target binding sites and the miRNA processing machinery in tumor cells, miRNAs have been discovered to be intimately associated with malignancies. The most significant benefit of biomarkers is their assistance in clinical decision-making [
46]. A significant approach for diagnosing and treating GBM is to use molecular biomarkers. In the current study, genes, miRNAs, and metabolites were used to develop a panel of predictive biomarkers for GBM.
Based on the biological pathways, the identified genes in the GBM biomarker panel were classified into different signaling pathways such as the AKT (MYC, BMI1, EGFR, PIK3CA, and PTK2, UBC), the inflammation (IRAK1 and APP), the P53 (HDAC1, P53, and TRIM28), the WNT (CTNNB1), and the mitochondrial signaling pathways (DAB1, PINK1, and RELN). The Akt pathway, or PI3K-Akt pathway, plays an imperative role in fundamental cellular processes such as protein synthesis, proliferation, and survival. Additionally, AKT regulates angiogenesis and metabolism [
47]. Most human cancers are associated with a transcription factor called
MYC, a member of the bHLHZip family. Some cellular functions are controlled by
MYC, including cell growth and proliferation, differentiation, and programmed cell death. There are also numerous human tumors with elevated levels of
MYC, including GBM [
48]. There is a correlation between Myc expression and glioma grade, and 60 to 80% of GBM exhibit elevated Myc [
49,
50]. Moreover, it was shown that the inhibition of Myc in gliomas reduces proliferation and increases apoptosis [
51]. The
BMI-1 is another important gene related to the AKT signaling pathway. The
BMI1 gene belongs to the polycomb group (PcG) gene family and is a transcriptional repressor of several genes that govern cell proliferation and differentiation throughout life [
52,
53,
54,
55,
56]. It was first discovered that BMI1 cooperated with the oncogene
c-MYC during murine lymphomagenesis [
57,
58]. BMI1 has been shown to regulate glioblastoma stem cells (GSCs) via differential gene networks in CD133
POS brain tumor-initiating cells [
59]. According to the results of another study, GSCs were targeted via the combination of BMI1 and EZH2. It was found that proneural GSCs are preferentially sensitive to EZH2 disruption, while mesenchymal GSCs are more sensitive to BMI1 inhibition. EZH2 and BMI1 targeting proved more effective than either agent alone in GBM due to the presence of both proneural and mesenchymal GSCs in GBM [
60].
GBM pathogenesis is also affected by
EGFR. Oncogenes such as
EGFR are frequently amplified in GBMs. There is evidence that
EGFR overexpression is associated with more aggressive GBM phenotypes in most primary GBMs, as well as some secondary GBMs [
61]. An analysis of the TCGA GBM database uncovered a subgroup with
EGFR amplification and
TP53 mutations that are almost mutually exclusive, suggesting EGFR is involved in regulating the function of wild-type
p53 (wt-
p53). EGFR signaling inhibits the function of wt-p53 in GBM by facilitating the interaction between p53 and DNA-dependent protein kinase catalytic subunit (DNA-PKcs) [
62]. The overexpression of YT521-B homology domain family 2 (YTHDF2) clinically was correlated with poor prognosis in a glioma patient. As a result of EGFR activation in most GBMs, YTHDF2 is overexpressed through the EGFR/SRC/ERK pathway. Signaling through EGFR/SRC/ERK stabilizes YTHDF2 by phosphorylating serine 39 and threonine 381 [
63].
For AKT to be activated, phosphatidylinositol 3-kinase (PI3K) must first be activated, which is activated by several upstream signaling pathways, including insulin receptors, receptor tyrosine kinases, G protein-coupled receptors, and cytokine receptors. Infiltrative gliomas frequently activate the PI3K signaling pathway, which promotes the growth and survival of cells. It has been reported that 6–15% of glioblastomas contain activating mutations in the
PIK3CA. There is evidence that
PIK3CA activating mutations are associated with an earlier recurrence of GBM in adults and a shorter survival time [
64]. PTK2, also known as focal adhesion kinase 1 (Fak1), is associated with focal adhesions and mediates signal transduction from integrin receptors to the MAPK and PI3k/Akt pathways [
65,
66]. PTEN may dephosphorylate PTK2, thereby regulating cell spreading, migration, and invasion [
67]. Furthermore, a strong expression of the PTK2 protein was demonstrated by immunohistochemical analysis in most anaplastic astrocytomas and glioblastomas [
68]. Also, elevated PTK2 protein levels were detected in astrocytic gliomas [
69]. Ubiquitin-dependent mechanisms could be exploited therapeutically for GBM. It was indicated that the ubiquitin system is involved in core signaling pathways, including EGFR, TGF-β, p53, and stemness-related pathways in GBM [
70]. In addition, it was shown that inhibition of ubiquitin signaling could reverse metabolic reprogramming and suppresses GBM growth. The regulation of protein stability by the ubiquitin-proteasome system (UPS) represents an important control mechanism of cell growth. UPS deregulation is mechanistically linked to the development and progression of various human cancers, including GBM. Praja2, a RING E3 ubiquitin ligase, is preferentially expressed in primary GBM lesions, expressing the wild-type isocitrate dehydrogenase 1 gene (IDH1). The researchers found that praja2 ubiquitylates and degrades the kinase suppressor of Ras 2 (KSR2). As a consequence, praja2 restrains the activity of downstream AMP-dependent protein kinase in GBM cells and attenuates oxidative metabolism [
71].
Inflammation plays a crucial role in tumor development, which is why interleukin-1 receptor-associated kinases (
IRAK), indispensable mediators of interleukin-1 receptor (IL1R) and Toll-like receptor (TLR)-inflammatory signaling, may contribute to the biological function of human cancers. According to the study,
IRAK expression was extensively altered and related to patient survival in pan-cancer. Furthermore,
in vitro and
in vivo studies have demonstrated that the highest expressed form of
IRAK1 in low-grade gliomas (LGG) inhibits cell apoptosis and increases malignancy [
72]. In mammals, amyloid precursor protein (APP) and amyloid precursor-like protein 1 (APLP1) and amyloid precursor-like protein 2 (APLP2) are highly conserved [
73]. Neuronal homeostasis, development, and neural transmission are critical functions of APP and APLP in Alzheimer's disease (AD). Cyclooxygenase-2 (COX-2), cytosolic phospholipase, interleukin-1β (IL-1β), and the β-amyloid precursor protein of proinflammatory and neurodegenerative genes were found to be up-regulated in the American Tissue Culture Collection of glioma and GBM. It has been shown that these genes are associated with inflammatory signaling cascades and gliosis in AD. Molecular genetic studies of the pathogenic signaling axis of βAPP–COX-2–CPL–IL-1β could reveal additional new therapeutic targets for the treatment of this devastating and lethal neurological condition [
74]. In addition, GBM is positively associated with mortality in AD [
75]. In glioma mouse models, immunostaining revealed that amyloid-β (1–42) deposition is observed in glioma tumors and nearby blood vessels. APLP2 is also closely related to gliomas and can be detected using thioflavin [
76].
There is an up-regulation of the HDAC class I isoforms HDAC1 and HDAC2 in GBM cell lines, compared with non-neoplastic brain tissues [
77,
78]. GBM cells are inhibited from proliferating, migrating, and invading when
HDAC1 and
HDAC2 expressions are silenced. Similarly, HDAC3 is overexpressed in aggressive glioma cell lines and is associated with poor prognosis and OS of GBM patients [
79]. A selective histone deacetylase inhibitor was shown to induce autophagy and cell death in GBM cells by downregulating SCNN1A [
80]. The HDAC family was clinically significant for gliomas. A significant correlation was found between most members of the HDAC family and glioma grade, IDH1 mutation, and 1p/19q co-deletion. Among the HDAC1-related signatures for precise prognosis prediction in glioma, HDAC1 indicates prognosis and immune infiltration [
81]. GBM is commonly associated with
TP53 mutations, which are associated with poorer prognoses and a poorer response to conventional therapies (chemoradiotherapy). Approximately 84% of GBM patients exhibit dysregulation of the p53-ARF-MDM2 pathway, a finding that is confirmed in 94% of GBM cell lines adopted for
in vitro assays [
82,
83]. There is a transcriptional co-repressor known as TRIM28 that is involved in the regulation of cancer. The expression of TRIM28 in gliomas was significantly higher than in non-glioma controls [
84]. Further, expression of TRIM28 was positively correlated with tumor malignancy and associated with poor OS and progression-free survival (PF). The results of another study indicated that TRIM28 promotes the proliferation of GBM cells and activates autophagy [
85]. Diverse cellular functions are mediated by PI3K/Akt-WNT signaling interactions in GBM, including cell proliferation, EMT, metabolism, and angiogenesis [
47]. Canonical WNT signaling plays an important role in cell proliferation and development, and its aberrant activation has been linked to tumorigenesis [
47]. The main effector of the WNT canonical pathway is CTNNB1/β-catenin, which has cooperative properties with transcription factors from the TCF/LEF (transcription factor/lymphoid enhancer binding factor) families to control gene expression via WNT signaling [
86]. A study has shown that inhibiting WNT-CTNNB1 signaling enhances the SQSTM1 expression and sensitizes GBM cells to autophagy blockers [
87].
According to the study, both RELN and its main downstream effector, DAB1, are silenced in GBM compared to non-neoplastic tissue, and their mRNA expression is inversely correlated with the grade of the disease [
88]. According to the results of another study, reelin, and DAB1 transcripts were more abundant in the peritumoral area and in peritumoral-derived CSCs that originated from the GBM tumor core. It is possible that reelin signaling plays a role in the pathology of GBM and in the recurrence of tumors that typically originate from the peritumoral region [
89]. There is evidence that PINK1 is an important regulator of the Warburg effect and a negative regulator of the growth of GBM. Loss of PINK1 contributes to the Warburg effect by stabilizing hypoxia-inducible factor-1A (HIF-1A) and reducing pyruvate kinase muscle isozyme 2 (PKM2) activity, both critical regulators of aerobic glycolysis. Through FOXO3a, a master regulator of oxidative stress and superoxide dismutase 2, PINK1 suppresses ROS and tumor growth. A loss of PINK1 has been observed in many human brain tumors, including GBM, and has been correlated with poor patient survival. In orthotopic mouse xenograft models and a transgenic drosophila GBM model, PINK1 overexpression attenuates GBM growth
in vivo. In this regard, PINK1 is a negative regulator of growth and the Warburg effect in GBM [
90]. A loss-of-function mutation in PINK1 causes mitochondrial defects and the degeneration of dopaminergic neurons, a hallmark of Parkinson's disease (PD). As opposed to this, increased expression of PINK1 was observed in different cancers, suggesting that PINK1 plays a role in neurodegeneration and tumorigenesis [
91]. Mitophagy, a selective autophagy of mitochondria, is crucial for quality control since it can efficiently degrade, remove and recycle malfunctioning or damaged mitochondria [
92]. It has been demonstrated that rapamycin, an inhibitor of mTOR, can rescue mitochondrial alterations. Specifically, rapamycin induces the expression of genes that promote mitochondrial autophagy (
PINK1, PARKIN, ULK1, and
AMBRA1) and mitochondrial fission (
FIS1, and DRP1) [
93]. In addition, it has been demonstrated that platelet-derived growth factor (PDGF) signaling induces N6-methyladenosine (m
6A) accumulation in GSCs to regulate mitophagy. A PDGF ligand stimulates the transcription of early growth response 1 (EGR1), which promotes the proliferation and self-renewal of GSCs by inducing methyltransferase-like 3 (METTL3). Through the regulation of m
6A modification of optineurin (OPTN), the PDGF-METTL3 axis inhibits mitophagy. In GBM patients, forced expression of OPTN mimics inhibition of PDGF, and higher OPTN levels predict a longer survival time [
94].
There were three categories of miRNAs identified in the GBM biomarker panel: Proliferation (hsa-mir-221-3p), invasion (hsa-mir-15a-5p and hsa-let-7b-5p), and proliferation and invasion (hsa-mir-30a-5p and hsa-mir-130a-3p). In various types of human cancer, including GBM, miR-221, and miR-222 (miR-221/222) are frequently up-regulated. MiR-221/222 regulates cell growth and cell cycle progression through targeting of p27 and p57, according to recent studies. In GBM, miR-221/222, which targets the p53 upregulated modulator of apoptosis (PUMA), was reported to induce cell survival [
95]. There is evidence that chronic miR-221/222-mediated downregulation of MGMT may result in cells being unable to repair genetic damage. The presence of miR-221/222 oncogenic potential may improve the prognosis of GBM [
96]. Furthermore, decreased EGFR and increased miR-221 were associated with increased resistance to temozolomide (TMZ) and radiotherapy in GBM [
97], compared to normal brain tissues (NBTs). MiR-30a-5p is overexpressed in glioma cell lines and glioma samples, with its expression level positively correlated with tumor grade [
98]. WWP1 (WW domain containing E3 ubiquitin-protein ligase 1) has also been shown to suppress NF-κB activation, which is strongly associated with the development of glioma. Moreover, the study's results have revealed the positive feedback loop of miR-30a-5p-WWP1-NF-κB in regulating glioma development [
99]. According to researchers, Wnt/β-catenin–miR-30a-5p–NCAM regulatory axis plays an essential role in controlling glioma cell invasion and tumorigenesis. It was shown that the Wnt/β-catenin pathway activates miR-30a-5p through the direct binding of β-catenin/TCF4 to two sites in the promoter region of miR-30a-5p. As well, miR-30a-5p can inhibit the expression of neural cell adhesion molecule (NCAM) by directly targeting two sites in the 3′-untranslated regions (3′-UTR) of NCAM mRNA [
100].
The proliferation and invasion of GBM cells are mediated by several critical molecules, such as cell adhesion molecule 1 (CADM1). CADM1 expression is decreased in GBM patients and GBM cell lines, and CADM1 overexpression inhibits the proliferation of GBM cells [
101,
102]. According to these findings, CADM1 effectively suppresses the proliferation of GBM. MiR15a5p was shown to promote the proliferation and invasion of T98G GBM cells by targeting CADM1 [
103]. The specificity protein 1 (Sp1) is aberrantly expressed in GBM and involved in the development and metastasis of the disease. In GBM cell lines, researchers found that the Sp1 expression was upregulated while miR-130a-3p expression was downregulated. Further, increased levels of miR-130a-3p inhibited GBM cell proliferation, migration, and TMZ resistance [
104]. The study also demonstrated that hsa-let-7b-5p could inhibit glioma cell migration, invasion, and cell cycle [
105].
In the GBM biomarker panel, five categories of metabolites were identified: Lipid metabolism (cholesterol), glutamate metabolism (glutamate and GABA), tricarboxylic acid (TCA) cycle (alanine), urea cycle (arginine), and Leloir cycle (galactose). There is a link between metabolic syndrome and several types of cancer, including GBM. An analysis of a New Zealand cohort of GBM patients showed that metabolic syndrome is associated with reduced OS. In light of this finding, there is a greater likelihood that GBM results from metabolic pathogenesis [
106]. According to studies, lipid metabolism plays a critical role in the pathogenesis of GBM. Among the members of the apolipoprotein family, apolipoprotein C1 (ApoC1) is crucial for the metabolism of both very-low-density lipoprotein (VLDL) and high-density lipoprotein (HDL) cholesterols. Recent research has indicated that ApoC1 may be a viable therapeutic target for solid malignancies. Based on the study's findings, Apoc1 could enhance glioma metastasis by increasing EMT and activating STAT3 [
107]. In another study, the level of serum LDL cholesterol pre-surgery was a prognostic factor for the outcome of patients with GBM [
108]. Cholesterol is another important molecule that would have the potential role of repurposed drugs. Due to the discovery that many cancers, including GBM, reprogrammed cholesterol metabolism, cholesterol metabolism has become a promising potential target for therapy. As GBM cells require external cholesterol for survival, as well as lipid droplets for rapid growth, different strategies have been proposed to inhibit cholesterol metabolism, including inhibition of cholesterol uptake and promotion of cholesterol efflux by activating liver X receptors (LXRs), disruption of cellular cholesterol trafficking, inhibition of SREBP signaling, inhibition of cholesterol esterification, and may potentially counteract with glial tumor growth [
109,
110]. There is an association between obesity-related pathologies of the central nervous system (CNS) like neuroinflammation and reactive gliosis and a high-fat diet (HFD)-related elevation of saturated fatty acids like palmitic acid (PA) in neurons and astrocytes of the brain. In neurons and astrocytes, PA causes apoptosis by increasing oxidative stress. As a result of these findings, it appears that HFD may cause neuronal and astrocytic damage, suggesting that CNS pathologies involving neuroinflammation and reactive gliosis may be associated with HFD [
111]. It has also been demonstrated that lipid accumulation and oxidation play a role in GBM. Monounsaturated fatty acids have been found to promote GBM proliferation by modulating triglyceride metabolism [
112]. A knockdown of carnitine palmitoyltransferase 1A (CPT1A), a critical enzyme in fatty acid oxidation (FAO), also reduced tumor growth and increased survival, according to
in vivo studies [
113].
The excitatory neurotransmitter glutamate plays a significant role in the proliferation, growth, and movement of brain tumor cells. Glutaminase produces a large amount of glutamate in glioma cells, which converts glutamate from glutamine and increases intracellular Ca
2+ through P2 × 7Rs [
114]. Moreover, high levels of glutamate have been found to cause brain edema and seizures in glioma patients. In GBM cells, GLAST, a glutamate-aspartate transporter expressed by astrocytes and involved in glutamate uptake, is highly expressed on the plasma membrane. There is a significant correlation between its expression and shortened patient survival. GBM xenografts were shown to be restricted in their progression and invasion when GLAST expression was inhibited [
115]. NADH shuttles, such as the malate-aspartate shuttle (MAS) and the glycerol-3-phosphate shuttle, can shuttle the reducing equivalents of cytosolic NADH into mitochondria. NADH shuttles are crucial in increasing mitochondrial energy production, as is widely accepted. An interesting finding revealed that NADH shuttles have a primary function in cancer cells, to maintain glycolysis by reducing cytosolic NADH/NAD
+ ratios. A widely used MAS inhibitor, AOAA (aminooxy acetic acid), decreased intracellular ATP levels, altered the cell cycle, and increased the apoptosis and necrosis of C6 glioma cells, without affecting the survival of primary astrocyte cultures [
116]. Glutamate and glutamine are linked to the proline pathway. L-proline is a multifunctional amino acid that plays an essential role in primary metabolism and physiological functions. Proline is oxidized to glutamate in the mitochondria, and the FAD-containing enzyme proline oxidase (PO) catalyzes the first step in the L-proline degradation pathway. It was shown that PO might play a regulatory role in glutamatergic neurotransmission by affecting the cellular concentration of glutamate [
117]. Study results indicate that serine and glycine levels are higher in low-nutrient regions of GBM tumors than in other regions. A study of the metabolic and functional properties of GBM cells revealed that serine availability and 1C metabolism support the survival of glioma cells, following glutamine deprivation. The synthesis of serine was mediated by autophagy rather than glycolysis [
118].
ATP by glycolysis and the TCA cycle are associated with oxidative phosphorylation (OXPHOS) through the breakdown of pyruvate or fatty acids to meet the growing energy demand of cancer cells. Recently, it was shown that SMI EPIC-0412 could effectively perturb the TCA cycle, which participated in the combination therapy of cytosolic phospholipase A2 (cPLA2)-inhibitor AACOCF3, and hexokinase II (HK2)-inhibitor 2-DG to disrupt the GBM energy metabolism for targeted metabolic treatments. ATP production was significantly declined in glioma cells when treated with monotherapy (EPIC-0412 or AACOCF3), dual therapy (EPIC-0412 + AACOCF3), or triple therapy (EPIC-0412 + AACOCF3 +2-DG) regimen [
119]. In the TCA cycle, glutamate is recycled to synthesize glutamate, which in turn is converted to GABA. Neurotransmitters, such as GABA, are thought to play a crucial role in GBM behavior. LGGs may be inhibited by GABA
AR activation through depolarization of the membrane caused by Na
+–K
+–2Cl
− co-transporter NKCC1. It is possible, however, that the decreased number of mRNA encoding GABA
AR subunits and loss of GABA
AR in GBM may indicate a relationship between the number of functional GABA
AR and the severity of the disease [
120,
121,
122]. In addition, GBM may counteract the attenuation of GABA on cell proliferation through a decrease in the expression of GABA
AR [
123,
124].
It has also been demonstrated that succinic semialdehyde dehydrogenase (SSADH) expression may contribute to the oxidation and/or consumption of GABA in gliomas; GABA oxidation capacity may also contribute to tumor proliferation and worse outcomes. Further, the IDH mutation, as well as the production of D-2-hydroxyglutarate (2-HG), inhibits the oxidation of GABA in glioma cells [
125]. Additionally, it was shown that GBM patients with high expression of glycolysis-related genes such as HK2 and PKM2, and low expression of mitochondrial metabolism-related genes, such as SDHB and COX5A, which are associated with TCA cycle and oxidative phosphorylation (OXPHOS), respectively, had poor patient survival. In contrast to LGG, expression levels of genes involved in mitochondrial oxidative metabolism in GBM are markedly increased; however, they are lower than those in normal brains [
126]. It has been shown that dysregulated alanine could serve as a potential predictive marker for glioma [
127]. Alanine, a glucogenic amino acid, enters the metabolic stream through enzymatic conversion to pyruvate to provide energy and replenish the nutrient reservoir for rapidly proliferating tumor cells [
128]. It is used to make proteins, and transfer RNA (tRNA) plays an important role in the epigenetic regulation of gene expression in tumors. A number of cell processes are mediated by tRNAs, including cell proliferation, signaling pathways, and stress responses, suggesting that tRNAs may also play a role in tumorigenesis and cancer progression [
129]. As tRNA methyltransferase 1 (METTL1) levels increase with increasing glioma grade, the expression levels of METTL1 may be used to predict the prognosis of gliomas [
130]. There has also been a link between the synthesis of tRNA in GBM and
de novo GTP biosynthesis due to the increased expression of
Impdh2 [
131]. It has also been shown that the upregulation of
Impdh2 is positively correlated with an increase in glioma malignancy and negatively correlated with the survival of patients [
131].
Arginine is another amino acid substrate actively metabolized by tumor cells to promote tumor growth and immunosuppression. L-arginine plays an important role in the urea cycle and modulates immune function and tumor metabolism. Arginase 1 (ARG1) and cytokine-inducible nitric oxide synthase (iNOS) are substrates for L-arginine. In the urea cycle, ARG1 converts L-arginine into urea and ornithine. The iNOS enzyme converts L-arginine to citrulline and nitric oxide (NO), which is necessary for the immune system to direct anti-tumor functions [
132,
133]. Arginine transporters appear to be in abundance in GBM, as evidenced by the accumulation of byproducts of arginine metabolism [
134,
135]. The results indicate that arginine metabolism is functional and may be sensitive to targeted depletion. Recent research demonstrated that pegylated human recombinant ARG1 depleted arginine in glioma cells and induced cytotoxicity [
136]. Likewise, these results demonstrate that radiotherapy's efficacy in treating GBM is potentiated by concomitant treatment with ADI-PEG20 in a non-arginine-auxotrophic cellular background (argininosuccinate synthase 1 positive). As a result of elevated NO, ADI-PEG20 enhanced the sensitivity of argininosuccinate synthetase 1-positive GBM to ionizing radiation, which generated cytotoxic peroxynitrites and promoted glioma-associated macrophage/microglial infiltration into tumors, changing their classical anti-inflammatory (protumor) phenotype into one of pro-inflammatory (anti-tumor) [
137].
The proliferation of GBM is dependent on the availability of extracellular nutrients. As a result of inadequate tumor perfusion, glucose, and glutamine are in short supply. Due to this metabolic remodeling, GBMs scavenge alternative nutrients from the tumor microenvironment to sustain their growth and proliferation. Glut3 and Glut14 are sugar transporters expressed in GBM. GBM cells are capable of scavenging galactose (Gal) from the circulation and extracellular space, as a suitable substrate for Glut3/Glut14. The Leloir pathway provides GBM cells with an alternative energy source by transporting and metabolizing Gal at physiological Glc concentrations [
138]. Additionally, D-galactose (D-gal), a reducing sugar, has been shown to induce senescence in GBM cells by inactivating the Yes-associated protein (YAP) and Cyclin-dependent kinase 6 (YAP-CDK6) signaling pathways [
139]. Another study examined the effects of 4-deoxy-4-fluoro galactose (4DFG), a galactose-based antimetabolite, on glioma metabolism
in vitro and
in vivo. In this study, they found that low concentrations of 4DFG (5 µM) could inhibit glycolytic and mitochondrial flux by approximately 12% [
140].
Figure 1.
An overview of the bioinformatics approaches used in this study. We created four gene lists from several different study levels. By merging these gene lists and performing various analyses, 11 genes and five key miRNAs were identified.
Figure 1.
An overview of the bioinformatics approaches used in this study. We created four gene lists from several different study levels. By merging these gene lists and performing various analyses, 11 genes and five key miRNAs were identified.
Figure 2.
Glioblastoma-related proteins identified by the NeDRex plugin.
Figure 2.
Glioblastoma-related proteins identified by the NeDRex plugin.
Figure 3.
Modules of disease identified by the MuST algorithm (A) and genes (B) that interconnect them. Five of the essential genes were identified: MYC, EGFR, PIK3CA, SUZ12, and SPRK2. Also, IRAK1, PTK2, and BMI1 represent bridging roles between disease modules.
Figure 3.
Modules of disease identified by the MuST algorithm (A) and genes (B) that interconnect them. Five of the essential genes were identified: MYC, EGFR, PIK3CA, SUZ12, and SPRK2. Also, IRAK1, PTK2, and BMI1 represent bridging roles between disease modules.
Figure 4.
Gene regulatory network obtained from eleven identified proteins. A wide range of interacting genes-miRNAs has been determined.
Figure 4.
Gene regulatory network obtained from eleven identified proteins. A wide range of interacting genes-miRNAs has been determined.
Figure 5.
The scheme of the relationship between the five identified miRNAs and their targets. hsa-mir-221-3p, and hsa-mir-30a-5p showed higher degree and betweenness centrality levels.
Figure 5.
The scheme of the relationship between the five identified miRNAs and their targets. hsa-mir-221-3p, and hsa-mir-30a-5p showed higher degree and betweenness centrality levels.
Figure 6.
The heatmap of the expression of eleven genes in normal brain tissue. A. Based on a microarray; B. Based on RNA-Seq.
Figure 6.
The heatmap of the expression of eleven genes in normal brain tissue. A. Based on a microarray; B. Based on RNA-Seq.
Figure 7.
The results of correlation analysis between eleven identified genes. Ten positive correlations were found between UBC (APP), HDAC1 (TP53, RBBP4, TRIM28, CTNNB1), RBBP4 (CTNNB1, TP53), TRIM28 (TP53, RBBP4, CSNK2A1), and eight negative correlations were found between RBBP4 (APP), PINK1 (TRIM28, RBBP4, TP53, HDAC1), and DAB1 (UBC, HDAC1, TP53).
Figure 7.
The results of correlation analysis between eleven identified genes. Ten positive correlations were found between UBC (APP), HDAC1 (TP53, RBBP4, TRIM28, CTNNB1), RBBP4 (CTNNB1, TP53), TRIM28 (TP53, RBBP4, CSNK2A1), and eight negative correlations were found between RBBP4 (APP), PINK1 (TRIM28, RBBP4, TP53, HDAC1), and DAB1 (UBC, HDAC1, TP53).
Figure 10.
The association of the results of metabolic pathway enrichment analysis with 182 metabolites: (A) Based on the KEGG database, (B) Based on the SMPDB database.
Figure 10.
The association of the results of metabolic pathway enrichment analysis with 182 metabolites: (A) Based on the KEGG database, (B) Based on the SMPDB database.
Figure 11.
Gene-Metabolite Interaction Network. The factors involved in the relationship between TP53, CTNNB1, CSNK2A1, and RELN with APP were further investigated.
Figure 11.
Gene-Metabolite Interaction Network. The factors involved in the relationship between TP53, CTNNB1, CSNK2A1, and RELN with APP were further investigated.
Figure 12.
The Determination of the top 25 SNPs via the MetaboAnalyst 5.0 database.
Figure 12.
The Determination of the top 25 SNPs via the MetaboAnalyst 5.0 database.
Table 1.
Data collection using 78 signaling pathways.
Table 1.
Data collection using 78 signaling pathways.
1 |
VEGF signaling pathway- hsa04370 |
40 |
TNF signaling pathway-hsa04668 |
2 |
PI3K-Akt signaling pathway-hsa04151 |
41 |
Citrate cycle (T.C.A. cycle)-hsa00020 |
3 |
Ras signaling pathway- hsa04014 |
42 |
Glycolysis / Gluconeogenesis-hsa00010 |
4 |
TGF-beta signaling pathway- hsa04350 |
43 |
Oxidative phosphorylation-hsa00190 |
5 |
HIF-1 signaling pathway- hsa04066 |
44 |
Starch and sucrose metabolism-hsa00500 |
6 |
AMPK signaling pathway- hsa04152 |
45 |
Pentose phosphate pathway- hsa00030 |
7 |
MAPK signaling pathway - hsa04010 |
46 |
Pyruvate metabolism- hsa00620 |
8 |
Rap1 signaling pathway - hsa04015 |
47 |
Insulin signaling pathway- hsa04910 |
9 |
Wnt signaling pathway - hsa04310 |
48 |
Lysosome-hsa04142 |
10 |
Notch signaling pathway-hsa04330 |
49 |
Phospholipase D signaling pathway- hsa04072 |
11 |
Hedgehog signaling pathway -hsa04340 |
50 |
Mitophagy- hsa04137 |
12 |
Hippo signaling pathway -hsa04390 |
51 |
Signaling pathways regulating pluripotency of stem cells- hsa04550 |
13 |
JAK-STAT signaling pathway -hsa04630 |
52 |
Cell adhesion molecules- hsa04514 |
14 |
Apelin signaling pathway - hsa04371 |
53 |
Cell cycle -hsa04110 |
15 |
NF-kappa B signaling pathway-hsa04064 |
54 |
ECM-receptor interaction-hsa04512 |
16 |
TNF signaling pathway - hsa04668 |
55 |
PD-L1 expression and PD-1 checkpoint pathway in cancer- hsa05235 |
17 |
FoxO signaling pathway - hsa04068 |
56 |
Pathways in cancer-hsa05200 |
18 |
Phosphatidylinositol signaling system - hsa04070 |
57 |
Transcriptional misregulation in cancer-hsa05202 |
19 |
mTOR signaling pathway - hsa04150 |
58 |
Central carbon metabolism in cancer- hsa05230 |
20 |
p53 signaling pathway-hsa04115 |
59 |
IL-17 signaling pathway-hsa04657 |
21 |
Apoptosis-hsa04210 |
60 |
Necroptosis-hsa04217 |
22 |
Ubiquitin-mediated proteolysis- hsa04120 |
61 |
Cellular senescence - hsa04218 |
23 |
Cell cycle- hsa04110 |
62 |
Chemokine signaling pathway-hsa04062 |
24 |
Regulation of actin cytoskeleton - hsa04810 |
63 |
Transcriptional misregulation in cancer-hsa05202 |
25 |
Calcium signaling pathway- hsa04020 |
64 |
ECM-receptor interaction- hsa04512 |
26 |
T cell receptor signaling pathway- hsa04660 |
65 |
Proteoglycans in cancer-hsa05205 |
27 |
Focal adhesion- hsa04510 |
66 |
Choline metabolism in cancer-hsa05231 |
28 |
Adherens junction- hsa04520 |
67 |
PD-L1 expression and PD-1 checkpoint pathway in cancer-hsa05235 |
29 |
Gap junction-hsa04540 |
68 |
Ferroptosis-hsa04216 |
30 |
Tight junction- hsa04530 |
69 |
Cholesterol metabolism- map04979 |
31 |
Arachidonic acid metabolism- hsa00590 |
70 |
Lipid and atherosclerosis-map05417 |
32 |
Autophagy-hsa04140 |
71 |
Fat digestion and absorption - map04975 |
33 |
Regulation of lipolysis in adipocytes- hsa04923 |
72 |
Vitamin digestion and absorption - map04977 |
34 |
Cytokine-cytokine receptor interaction-hsa04060 |
73 |
Aldosterone synthesis and secretion - map04925 |
35 |
Proteasome- hsa03050 |
74 |
Primary bile acid biosynthesis - map00120 |
36 |
B cell receptor signaling pathway- hsa04662 |
75 |
Cortisol synthesis and secretion - map04927 |
37 |
Complement and coagulation cascades- hsa04610 |
76 |
Bile secretion - map04976 |
38 |
Toll-like receptor signaling pathway-hsa04620 |
77 |
Ovarian steroidogenesis - map04913 |
39 |
RIG-I-like receptor signaling pathway- hsa04622 |
78 |
Steroid biosynthesis - map00100 |
Table 2.
The identification of eleven critical genes through the integration of results and network analysis. The list of important genes is based on their centrality. Deg: Degree, Bet: Betweenness, Bri: Bridge, Cent: Centroid, Close: Closeness, and EiVe: EigenVector.
Table 2.
The identification of eleven critical genes through the integration of results and network analysis. The list of important genes is based on their centrality. Deg: Degree, Bet: Betweenness, Bri: Bridge, Cent: Centroid, Close: Closeness, and EiVe: EigenVector.
Gene Name |
description |
Deg |
Bet |
Bridg |
Cent |
Close |
EiVe |
UBC |
Ubiquitin C [Source: HGNC Symbol; Acc: HGNC:12468 |
+ |
+ |
-- |
-- |
+ |
+ |
HDAC1 |
Histone deacetylase 1 [Source: HGNC Symbol; Acc: HGNC:4852 |
+ |
-- |
-- |
-- |
+ |
+ |
CTNNB1 |
Catenin beta 1 [Source: HGNC Symbol; Acc: HGNC:2514 |
+ |
-- |
-- |
-- |
+ |
+ |
TRIM28 |
Tripartite motif-containing 28 [Source: HGNC Symbol; Acc: HGNC:16384 |
-- |
+ |
-- |
-- |
+ |
+ |
CSNK2A1 |
casein kinase two alpha 1 [Source: HGNC Symbol; Acc: HGNC:2457 |
-- |
-- |
-- |
-- |
+ |
+ |
RBBP4 |
RB binding protein 4, chromatin remodeling factor [Source: HGNC Symbol; Acc: HGNC:9887 |
+ |
-- |
-- |
-- |
-- |
-- |
TP53 |
Tumor protein p53 [Source:HGNC Symbol;Acc:HGNC:11998 |
+ |
-- |
-- |
-- |
-- |
-- |
APP |
Amyloid beta precursor protein [Source: HGNC Symbol; Acc: HGNC:620 |
-- |
+ |
-- |
-- |
-- |
-- |
DAB1 |
DAB1, reelin adaptor protein [Source: HGNC Symbol; Acc: HGNC:2661 |
-- |
+ |
-- |
-- |
-- |
-- |
PINK1 |
PTEN-induced putative kinase 1 [Source: HGNC Symbol; Acc: HGNC:14581 |
-- |
+ |
-- |
-- |
-- |
-- |
RELN |
Reelin |
literature review + miRNA-gene regulatory network |
Table 3.
The identification of five Key miRNAs by consideration of two parameters (degree and betweenness centralities).
Table 3.
The identification of five Key miRNAs by consideration of two parameters (degree and betweenness centralities).
Label |
Degree |
Betweenness |
hsa-mir-221-3p |
4 |
5682.13 |
hsa-mir-30a-5p |
4 |
2373.43 |
hsa-mir-15a-5p |
3 |
3710.08 |
hsa-mir-130a-3p |
3 |
3589.18 |
hsa-let-7b-5p |
2 |
2523.74 |
Table 4.
The expression status of eleven genes identified in GBM disease. Six genes represent a significantly increased expression in the GBM state, whereas four genes were downregulated. All eleven specific genes were altered during the primary stage of the tumor.
Table 4.
The expression status of eleven genes identified in GBM disease. Six genes represent a significantly increased expression in the GBM state, whereas four genes were downregulated. All eleven specific genes were altered during the primary stage of the tumor.
Gene Name |
Non- tumor |
GBM |
Pairwise t-test (GBM-Non-tumor) p.adj (p-value with Bonferroni correction) |
Primary |
Secondary |
Recurrent |
UBC |
-- |
+ |
1.8E-03 |
+ |
-- |
-- |
HDAC 1 |
-- |
+ |
7.8E-18 |
+ |
-- |
-- |
CTNNB1 |
-- |
+ |
6.0E-03 |
+ |
-- |
-- |
TRIM28 |
-- |
+ |
1.1E-03 |
+ |
-- |
-- |
CSNK2A1 |
-- |
+ |
6.9E-01 (ns) |
+ |
-- |
-- |
RBBP4 |
-- |
+ |
3.2E-05 |
+ |
-- |
-- |
TP53 |
-- |
+ |
1.6E-13 |
+ |
-- |
-- |
APP |
+ |
-- |
1.2E-03 |
+ |
-- |
-- |
DAB1 |
+ |
-- |
4.0E-04 |
+ |
-- |
-- |
PINK1 |
+ |
-- |
2.9E-10 |
+ |
-- |
-- |
RELN |
+ |
-- |
5.7E-08 |
+ |
-- |
-- |
Table 5.
The application of multiple criteria in the metabolic pathway analysis.
Table 5.
The application of multiple criteria in the metabolic pathway analysis.
Result |
Visualization methods |
Enrichment method |
Topology analysis |
Reference metabolome |
Pathway library |
1 |
Scatter plot |
Hypergeometric test |
Relative-betweenness centrality R-b C |
All compounds in the selected pathway library |
Homo sapiens (KEGG) |
2 |
Scatter plot |
Hypergeometric test |
Out-degree Centrality O-d C |
All combinations in the selected pathway library |
Homo sapiens (KEGG) |
3 |
Scatter plot |
Hypergeometric test |
Relative-betweenness centrality |
All compounds in the selected pathway library |
Homo sapiens (SMPDB) |
4 |
Scatter plot |
Hypergeometric test |
Out-degree Centrality |
All combinations in the selected pathway library |
Homo sapiens (SMPDB) |
Table 6.
The final results from the metabolic pathway analysis. Further discussion of two items from the KEGG database (nitrogen metabolism, alanine, aspartate, and glutamate metabolism), and three from the SMPDB database (alanine metabolism, aspartate metabolism, and malate-aspartate shuttle) due to vitality.
Table 6.
The final results from the metabolic pathway analysis. Further discussion of two items from the KEGG database (nitrogen metabolism, alanine, aspartate, and glutamate metabolism), and three from the SMPDB database (alanine metabolism, aspartate metabolism, and malate-aspartate shuttle) due to vitality.
KEGG Database |
SMPDB Database |
Result 1 |
R-b C impact |
FDR |
Result 2 |
O-d C impact |
FDR |
Result 3 |
R-b C impact |
FDR |
Result 4 |
O-d C impact |
FDR |
Final Decision (FD) |
Final Decision (FD) |
Final Decision (FD) |
Final Decision (FD) |
Nitrogen metabolism |
1 |
0.043213 |
Arginine biosynthesis |
0.8125 |
1.90E-07 |
Alanine metabolism |
1 |
0.010641 |
Malate-aspartate shuttle |
0.63333 |
0.013128 |
FD: + |
FD: -- |
FD: + |
FD: + |
Phenylalanine, tyrosine, and tryptophan biosynthesis |
1 |
0.12885 |
Alanine, aspartate and glutamate metabolism |
0.75 |
1.73E-07 |
Trehalose degradation |
0.84211 |
0.18355 |
Phosphatidylcholine biosynthesis |
0.56707 |
0.00011577 |
FD: -- |
FD: + |
FD: -- |
FD: -- |
Synthesis and degradation of ketone bodies |
0.86667 |
0.18716 |
Valine, leucine, and isoleucine biosynthesis |
0.75 |
8.82E-05 |
Aspartate metabolism |
0.8 |
0.0044894 |
Transfer of acetyl groups into mitochondria |
0.54167 |
0.010641 |
FD: -- |
FD: -- |
FD: + |
FD: -- |
Alanine, aspartate and glutamate metabolism |
0.81732 |
1.73E-07 |
Nitrogen metabolism |
0.75 |
0.043213 |
Glycerol phosphate shuttle |
0.7619 |
0.3023 |
Ammonia recycling |
0.49306 |
0.00011577 |
FD: + |
FD: + |
FD: -- |
FD: -- |
One-carbon pool by folate |
0.80793 |
0.46957 |
Phenylalanine, tyrosine, and tryptophan biosynthesis |
0.75 |
0.12885 |
Malate-Aspartate Shuttle |
0.71429 |
0.013128 |
Cardiolipin biosynthesis |
0.49057 |
0.013128 |
FD:-- |
FD:-- |
FD: + |
FD: -- |
Table 7.
The application of multiple criteria in the joint pathway analysis.
Table 7.
The application of multiple criteria in the joint pathway analysis.
Result |
Enrichment method |
Topology measure |
Integration method |
1 |
Hypergeometric test |
Degree centrality |
Combined score |
2 |
Betweenness centrality |
3 |
Closeness centrality |
Table 8.
The final results from joint pathway analysis. The two items (citrate cycle and arginine biosynthesis) observed in all three centralities were selected and discussed further.
Table 8.
The final results from joint pathway analysis. The two items (citrate cycle and arginine biosynthesis) observed in all three centralities were selected and discussed further.
Title |
Degree |
Betweenness |
Closeness |
Alanine, aspartate and glutamate metabolism |
+ |
+ |
-- |
Citrate cycle (TCA cycle) |
+ |
+ |
+ |
Arginine biosynthesis |
+ |
+ |
+ |
Synthesis and degradation of ketone bodies |
+ |
-- |
+ |
Pyruvate metabolism |
+ |
-- |
+ |
Purine metabolism |
+ |
+ |
-- |
Glutathione metabolism |
+ |
+ |
-- |
Pyrimidine metabolism |
+ |
+ |
-- |
Glycolysis or gluconeogenesis |
-- |
+ |
+ |
Table 9.
The summary of all results obtained from the pathway enrichment analysis at different levels of pathway, and joint pathway analyses.
Table 9.
The summary of all results obtained from the pathway enrichment analysis at different levels of pathway, and joint pathway analyses.
Enrichment Analysis |
Pathway analysis |
Joint pathway analysis |
Eleven Genes |
Five miRNAs |
182 Metabolites |
Mitophagy |
Fatty acid biosynthesis |
Aminoacyl-tRNA biosynthesis |
Nitrogen metabolism |
Citrate cycle (TCA cycle) |
Wnt signaling pathway |
Galactose metabolism |
Arginine biosynthesis |
Alanine, aspartate and glutamate metabolism |
Arginine biosynthesis |
|
Mucin-type O-glycan biosynthesis |
Alanine, aspartate and glutamate metabolism |
Malate-aspartate shuttle |
|
Autophagy |
Glutamate metabolism |
Urea cycle |
Arginine and proline metabolism |
Table 10.
The metabolites and SNPs from the mGWAS-Explorer database.
Table 10.
The metabolites and SNPs from the mGWAS-Explorer database.
Metabolite |
SNP |
HDL |
rs111929233, rs7298751 |
N6-acetyllysine |
rs12602273, rs12603869, rs12945970, rs12947788, rs12949655, rs12951053, rs1642782, rs17881556, rs1794284, rs2078486, rs5819163 |
Cholesterol |
rs35608584, rs111929233 |
Formate |
rs17520463 |
N, N-Dimethylglycine/Xylose |
rs41450451 |
X2.piperidinone |
rs75787097, rs75524270, rs79232054, rs145435197, rs74901488, rs117235978 |