Transcriptomic analysis of glioblastoma multiforme providing new insights into GPR17 signaling communication

A2A receptor antagonist 4-(2-((6-Amino-9-ethyl-8-(furan-2-yl)-9H-purin-2-yl)amino)ethyl)phenol, a promising adenosine derivative for glioblastoma treatment

Adenosine, a pervasive signaling molecule mediated by its interaction with G-protein-coupled receptor subtypes, especially the A2A adenosine receptor (A2AAR), plays a crucial role in cancer treatment. Recently, A2AAR targeting adenosine analogs have been proposed as a potential therapeutic target for cancer treatment. However, the molecules targeting A2AAR and their mode of action in inhibiting glioblastoma cell progression remain unknown. We synthesized six adenosine derivatives substituted at the 9-, 2- and/or N6- and/or 8- positions, and their anti-proliferative efficacy against the GBM cell lines LN229 and SNB19 was assessed. Molecular dynamic simulation integrated with experimental analyses, including cell cycle arrest, apoptosis assay, ligand binding assay, absorption, distribution, metabolism, excretion and toxicity (ADMET) profiling, PAMPA assay, and 3D spheroid analysis, were performed to identify the interaction efficacy of the potential derivative with A2AAR and its ability to prevent GBM cell progression. The most potent A2AAR derivative (ANR), 4-(2-((6-Amino-9-ethyl-8-(furan-2-yl)-9H-purin-2-yl)amino)ethyl)phenol (ANR 672) inhibits 5'-N-Ethylcarboxamidoadenosine (NECA)-induced cAMP validating the antagonistic property with higher cytotoxicity effect against GBM cells. ANR 672 showed higher affinity toward A2AAR (Ki = 1.02 ± 0.06 nM) and exhibited significant IC50 concentrations of ∼ 60-80 µM, than FDA approved drug istredefylline. The A2AAR-ANR 672 interaction profile showed well-defined hydrogen bonds and hydrophobic contacts, indicating a typical binding mechanism inside the receptor pocket and a higher degree of conformational flexibility than the A2AAR-Istradefylline complex. The antagonist effect of ANR 672 blocked the A2AAR signaling pathway, leading to necrosis-mediated cell death and cell cycle arrest at the S-phase in both the GBM cells. ANR 672 treated 3D tumour spheroids analysis with real-time spheroid volume and cell proliferation analysis revealed the potential ability of ANR 672 against GBM cell growth. Drug-likeness assessments also showed favorable pharmacokinetic profiles for ANR 672. Further validation of blood-brain barrier crossing potential revealed that ANR 672 possesses moderate permeability. Our findings shed light on how ANR 672 exerts its GBM-suppressive effect through the interaction of A2AAR. These preclinical results suggest that A2AAR blockade could be a unique strategy for treating GBM.

Discovery of Anthranilic Acid Derivatives as Antagonists of the Pro-Inflammatory Orphan G Protein-Coupled Receptor GPR17

The G protein-coupled receptor 17 (GPR17) is an orphan receptor involved in inflammatory diseases. GPR17 antagonists have been proposed for the treatment of multiple sclerosis due to their potential to induce remyelination. Potent, selective antagonists are required to enable target validation. In the present study, we describe the discovery of a novel class of GPR17 antagonists based on an anthranilic acid scaffold. The compounds' potencies were evaluated in calcium mobilization and radioligand binding assays, and structure-activity relationships were analyzed. Selected antagonists were additionally studied in cAMP and G protein activation assays. The most potent antagonists were 5-methoxy-2-(5-(3'-methoxy-[1,1'-biphenyl]-2-yl)furan-2-carboxamido)benzoic acid (52, PSB-22269, Ki 8.91 nM) and its 3'-trifluoromethyl analog (54, PSB-24040, Ki 83.2 nM). Receptor-ligand docking studies revealed that the compounds' binding site is characterized by positively charged arginine residues and a lipophilic pocket. These findings yield valuable insights into this poorly characterized receptor providing a basis for future drug development.

Design, synthesis and anticancer evaluation of novel arylhydrazones of active methylene compounds

Nerve growth factor (NGF) and its receptor, tropomyosin kinase receptor kinase type A (TrkA) is emerging as an important target for Glioblastoma (GBM) treatment. TrkA is the cancer biomarker majorly involved in tumor invasion and migration into nearby normal tissue. However, currently, available Trk inhibitors exhibit many adverse effects in cancer patients, thus demanding a novel class of ligands to regulate Trk signaling. Here, we exploited the role of TrkA (NTRK1) expression from the 651 datasets of brain tumors. RNA sequence analysis identified overexpression of NTRK1 in GBM, recurrent GBM as well in Oligoastrocytoma patients. Also, TrkA expression tends to increase over the higher grades of GBM. TrkA protein targeting hydrazone derivatives, R48, R142, and R234, were designed and their mode of interaction was studied using molecular docking and dynamic simulation studies. Ligands' stability and binding assessment reveals R48, 2 2-(2-(2-hydroxy-4-nitrophenyl) hydrazineylidene)-1-phenylbutane-1,3-dione, as a potent ligand that interacts well with TrkA's hydrophobic residues, Ile, Phe, Leu, Ala, and Val. R48- TrkA exhibits stable binding potentials with an average RMSD value <0.8 nm. R48 obeyed Lipinski's rule of five and possessed the best oral bioavailability, suggesting R48 as a potential compound with drug-likeness properties. In-vitro analysis also revealed that R48 exhibited a higher cytotoxicity effect for U87 GBM cells than TMZ with the IC50 value of 68.99 μM. It showed the lowest percentage of cytotoxicity to the non-cancerous TrkA expressing MEF cells. However, further SiRNA analysis validates the non-specific binding of R48, necessitating structural alteration for the development of R48-based TrkA inhibitor for GBM therapeutics.

Pharmacogenomic Analysis of Combined Therapies against Glioblastoma Based on Cell Markers from Single-Cell Sequencing

Glioblastoma is the most common and aggressive form of primary brain cancer and the lack of viable treatment options has created an urgency to develop novel treatments. Personalized or predictive medicine is still in its infancy stage at present. This research aimed to discover biomarkers to inform disease progression and to develop personalized prophylactic and therapeutic strategies by combining state-of-the-art technologies such as single-cell RNA sequencing, systems pharmacology, and a polypharmacological approach. As predicted in the pyroptosis-related gene (PRG) transcription factor (TF) microRNA (miRNA) regulatory network, TP53 was the hub gene in the pyroptosis process in glioblastoma (GBM). A LASSO Cox regression model of pyroptosis-related genes was built to accurately and conveniently predict the one-, two-, and three-year overall survival rates of GBM patients. The top-scoring five natural compounds were parthenolide, rutin, baeomycesic acid, luteolin, and kaempferol, which have NFKB inhibition, antioxidant, lipoxygenase inhibition, glucosidase inhibition, and estrogen receptor agonism properties, respectively. In contrast, the analysis of the cell-type-specific differential expression-related targets of natural compounds showed that the top five subtype cells targeted by natural compounds were endothelial cells, microglia/macrophages, oligodendrocytes, dendritic cells, and neutrophil cells. The current approach-using the pharmacogenomic analysis of combined therapies-serves as a model for novel personalized therapeutic strategies for GBM treatment.

Benzenesulfonamide Analogs: Synthesis, Anti-GBM Activity and Pharmacoprofiling

The tropomyosin receptor kinase A (TrkA) family of receptor tyrosine kinases (RTKs) emerge as a potential target for glioblastoma (GBM) treatment. Benzenesulfonamide analogs were identified as kinase inhibitors possessing promising anticancer properties. In the present work, four known and two novel benzenesulfonamide derivatives were synthesized, and their inhibitory activities in TrkA overexpressing cells, U87 and MEF cells were investigated. The cytotoxic effect of benzenesulfonamide derivatives and cisplatin was determined using trypan blue exclusion assays. The mode of interaction of benzenesulfonamides with TrkA was predicted by docking and structural analysis. ADMET profiling was also performed for all compounds to calculate the drug likeness property. Appropriate QSAR models were developed for studying structure-activity relationships. Compound 4-[2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl]-N-(5-methyl-1,3,4-thiadiazol-2-yl)benzenesulfon-amide (AL106) and 4-[2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)hydrazinyl]-N-(5-methyl-1,3,4-thiadiazol-2-yl)benzenesulfonamide (AL107) showed acceptable binding energies with the active sites for human nerve growth factor receptor, TrkA. Here, AL106 was identified as a potential anti-GBM compound, with an IC50 value of 58.6 µM with a less toxic effect in non-cancerous cells than the known chemotherapeutic agent, cisplatin. In silico analysis indicated that AL106 formed prominent stabilizing hydrophobic interactions with Tyr359, Ser371, Ile374 and charged interactions with Gln369 of TrkA. Furthermore, in silico analysis of all benzenesulfonamide derivatives revealed that AL106 has good pharmacokinetics properties, drug likeness and toxicity profiles, suggesting the compound may be suitable for clinical trial. Thus, benzenesulfonamide analog, AL106 could potentially induce GBM cell death through its interaction with TrkA and might be an attractive strategy for developing a drug targeted therapy to treat glioblastoma.

Mitochondrial complex III bypass complex I to induce ROS in GPR17 signaling activation in GBM

Guanine nucleotide binding protein (G protein) coupled receptor 17 (GPR17) plays crucial role in Glioblastoma multiforme (GBM) cell signaling and is primarily associated with reactive oxidative species (ROS) production and cell death. However, the underlying mechanisms by which GPR17 regulates ROS level and mitochondrial electron transport chain (ETC) complexes are still unknown. Here, we investigate the novel link between the GPR17 receptor and ETC complex I and III in regulating level of intracellular ROS (ROSi) in GBM using pharmacological inhibitors and gene expression profiling. Incubation of 1321N1 GBM cells with ETC I inhibitor and GPR17 agonist decreased the ROS level, while treatment with GPR17 antagonist increased the ROS level. Also, inhibition of ETC III and activation of GPR17 increased the ROS level whereas opposite function was observed with antagonist interaction. The similar functional role was also observed in multiple GBM cells, LN229 and SNB19, where ROS level increased in the presence of Complex III inhibitor. The level of ROS varies in Complex I inhibitor and GPR17 antagonist treatment conditions suggesting that ETC I function differs depending on the GBM cell line. RNAseq analysis revealed that ∼ 500 genes were commonly expressed in both SNB19 and LN229, in which 25 genes are involved in ROS pathway. Furthermore, 33 dysregulated genes were observed to be involved in mitochondria function and 36 genes of complex I-V involved in ROS pathway. Further analysis revealed that induction of GPR17 leads to loss of function of NADH dehydrogenase genes involved in ETC I, while cytochrome b and Ubiquinol Cytochrome c Reductase family genes in ETC III. Overall, our findings suggest that mitochondrial ETC III bypass ETC I to increase ROS_i in GPR17 signaling activation in GBM and could provide new opportunities for developing targeted therapy for GBM.

Structural analysis of human G-protein-coupled receptor 17 ligand binding sites

The human G protein coupled membrane receptor (GPR17), the sensor of brain damage, is identified as a biomarker for many neurological diseases. In human brain tissue, GPR17 exist in two isoforms, long and short. While cryo-electron microscopy technology has provided the structure of the long isoform of GPR17 with Gi complex, the structure of the short isoform and its activation mechanism remains unclear. Recently, we theoretically modeled the structure of the short isoform of GPR17 with Gi signaling protein and identified novel ligands. In the present work, we demonstrated the presence of two distinct ligand binding sites in the short isoform of GPR17. The molecular docking of GPR17 with endogenous (UDP) and synthetic ligands (T0510.3657, MDL29950) found the presence of two distinct binding pockets. Our observations revealed that endogenous ligand UDP can bind stronger in two different binding pockets as evidenced by glide and autodock vina scores, whereas the other two ligand's binding with GPR17 has less docking score. The analysis of receptor-UDP interactions shows complexes' stability in the lipid environment by 100 ns atomic molecular dynamics simulations. The amino acid residues VAL83, ARG87, and PHE111 constitute ligand binding site 1, whereas site 2 constitutes ASN67, ARG129, and LYS232. Root mean square fluctuation analysis showed the residues 83, 87, and 232 with higher fluctuations during molecular dynamics simulation in both binding pockets. Our findings imply that the residues of GPR17's two binding sites are crucial, and their interaction with UDP reveals the protein's hidden signaling and communication properties. Furthermore, this finding may assist in the development of targeted therapies for the treatment of neurological diseases.

Molecular modeling and dynamics studies of the synthetic small molecule agonists with GPR17 and P2Y1 receptor

The human Guanine Protein coupled membrane Receptor 17 (hGPR17), an orphan receptor that activates uracil nucleotides and cysteinyl leukotrienes is considered as a crucial target for the neurodegenerative diseases. Yet, the detailed molecular interaction of potential synthetic ligands of GPR17 needs to be characterized. Here, we have studied a comparative analysis on the interaction specificity of GPR17-ligands with hGPR17 and human purinergic G protein-coupled receptor (hP2Y1) receptors. Previously, we have simulated the interaction stability of synthetic ligands such as T0510.3657, AC1MLNKK, and MDL29951 with hGPR17 and hP2Y1 receptor in the lipid environment. In the present work, we have comparatively studied the protein-ligand interaction of hGPR17-T0510.3657 and P2Y1-MRS2500. Sequence analysis and structural superimposition of hGPR17 and hP2Y1 receptor revealed the similarities in the structural arrangement with the local backbone root mean square deviation (RMSD) value of 1.16 Å and global backbone RMSD value of 5.30 Å. The comparative receptor-ligand interaction analysis between hGPR17 and hP2Y1 receptor exposed the distinct binding sites in terms of geometrical properties. Further, the molecular docking of T0510.3657 with the hP2Y1 receptor have shown non-specific interaction. The experimental validation also revealed that Gi-coupled activation of GPR17 by specific ligands leads to the adenylyl cyclase inhibition, while there is no inhibition upon hP2Y1 activation. Overall, the above findings suggest that T0510.3657-GPR17 binding specificity could be further explored for the treatment of numerous neuronal diseases. Communicated by Ramaswamy H. Sarma.

Alkylaminophenol and GPR17 Agonist for Glioblastoma Therapy: A Combinational Approach for Enhanced Cell Death Activity

Drug resistance and tumor heterogeneity limits the therapeutic efficacy in treating glioblastoma, an aggressive infiltrative type of brain tumor. GBM cells develops resistance against chemotherapeutic agent, temozolomide (TMZ), which leads to the failure in treatment strategies. This enduring challenge of GBM drug resistance could be rational by combinatorial targeted therapy. Here, we evaluated the combinatorial effect of phenolic compound (2-(3,4-dihydroquinolin-1(2H)-yl)(p-tolyl)methyl)phenol (THTMP), GPR17 agonist 2-({5-[3-(Morpholine-4-sulfonyl)phenyl]-4-[4-(trifluoromethoxy)phenyl]-4H-1,2,4-triazol-3-yl}sulfanyl)-N-[4-(propan-2-yl)phenyl]acetamide (T0510.3657 or T0) with the frontline drug, TMZ, on the inhibition of GBM cells. Mesenchymal cell lines derived from patients' tumors, MMK1 and JK2 were treated with the combination of THTMP + T0, THTMP + TMZ and T0 + TMZ. Cellular migration, invasion and clonogenicity assays were performed to check the migratory behavior and the ability to form colony of GBM cells. Mitochondrial membrane permeability (MMP) assay and intracellular calcium, [Ca2+]i, assay was done to comprehend the mechanism of apoptosis. Role of apoptosis-related signaling molecules was analyzed in the induction of programmed cell death. In vivo validation in the xenograft models further validates the preclinical efficacy of the combinatorial drug. GBM cells exert better synergistic effect when exposed to the cytotoxic concentration of THTMP + T0, than other combinations. It also inhibited tumor cell proliferation, migration, invasion, colony-forming ability and cell cycle progression in S phase, better than the other combinations. Moreover, the combination of THTMP + T0 profoundly increased the [Ca2+]i, reactive oxygen species in a time-dependent manner, thus affecting MMP and leading to apoptosis. The activation of intrinsic apoptotic pathway was regulated by the expression of Bcl-2, cleaved caspases-3, cytochrome c, HSP27, cIAP-1, cIAP-2, p53, and XIAP. The combinatorial drug showed promising anti-tumor efficacy in GBM xenograft model by reducing the tumor volume, suggesting it as an alternative drug to TMZ. Our findings indicate the coordinated administration of THTMP + T0 as an efficient therapy for inhibiting GBM cell proliferation.

Targeting Orphan G Protein-Coupled Receptor 17 with T0 Ligand Impairs Glioblastoma Growth

Simple Summary

Glioblastoma multiforme (GBM), or glioblastoma chemotherapy, has one of the poorest improvements across all types of cancers. Despite the different rationales explored in targeted therapy for taming the GBM aggressiveness, its phenotypic plasticity, drug toxicity, and adaptive resistance mechanisms pose many challenges in finding an effective cure. Our manuscript reports the expression and prognostic role of orphan receptor GPR17 in glioma, the molecular mechanism of action of the novel ligand of GPR17, and provides evidence how the T0 agonist promotes glioblastoma cell death through modulation of the MAPK/ERK, PI3K–Akt, STAT, and NF-κB pathways. The highlights are as follows: GPR17 expression is associated with greater survival for both low-grade glioma (LGG) and GBM; GA-T0, a potent GPR17 receptor agonist, causes significant GBM cell death and apoptosis; GPR17 signaling promotes cell cycle arrest at the G1 phase in GBM cells; key genes are modulated in the signaling pathways that inhibit GBM cell proliferation; and GA-T0 crosses the blood–brain barrier and reduces tumor volume.

Abstract

Glioblastoma, an invasive high-grade brain cancer, exhibits numerous treatment challenges. Amongst the current therapies, targeting functional receptors and active signaling pathways were found to be a potential approach for treating GBM. We exploited the role of endogenous expression of GPR17, a G protein-coupled receptor (GPCR), with agonist GA-T0 in the survival and treatment of GBM. RNA sequencing was performed to understand the association of GPR17 expression with LGG and GBM. RT-PCR and immunoblotting were performed to confirm the endogenous expression of GPR17 mRNA and its encoded protein. Biological functions of GPR17 in the GBM cells was assessed by in vitro analysis. HPLC and histopathology in wild mice and an acute-toxicity analysis in a patient-derived xenograft model were performed to understand the clinical implication of GA-T0 targeting GPR17. We observed the upregulation of GPR17 in association with improved survival of LGG and GBM, confirming it as a predictive biomarker. GA-T0-stimulated GPR17 leads to the inhibition of cyclic AMP and calcium flux. GPR17 signaling activation enhances cytotoxicity against GBM cells and, in patient tissue-derived mesenchymal subtype GBM cells, induces apoptosis and prevents proliferation by stoppage of the cell cycle at the G1 phase. Modulation of the key genes involved in DNA damage, cell cycle arrest, and in several signaling pathways, including MAPK/ERK, PI3K–Akt, STAT, and NF-κB, prevents tumor regression. In vivo activation of GPR17 by GA-T0 reduces the tumor volume, uncovering the potential of GA-T0–GPR17 as a targeted therapy for GBM treatment. Conclusion: Our analysis suggests that GA-T0 targeting the GPR17 receptor presents a novel therapy for treating glioblastoma.

Synthesis and Preclinical Validation of Novel Indole Derivatives as a GPR17 Agonist for Glioblastoma Treatment

The discovery of a potential ligand-targeting G protein-coupled receptor 17 (GPR17) is important for developing chemotherapeutic agents against glioblastoma multiforme (GBM). We used the integration of ligand- and structure-based cheminformatics and experimental approaches for identifying the potential GPR17 ligand for GBM treatment. Here, we identified a novel indoline-derived phenolic Mannich base as an activator of GPR17 using molecular docking of over 6000 indoline derivatives. One of the top 10 hit molecules, CHBC, with a glide score of -8.390 was synthesized through a multicomponent Petasis borono-Mannich reaction. The CHBC-GPR17 interaction leads to a rapid decrease of cAMP and Ca²⁺. CHBC exhibits the cytotoxicity effect on GBM cells in a dose-dependent manner with an IC₅₀ of 85 μM, whereas the known agonist MDL29,951 showed a negligible effect. Our findings suggest that the phenolic Mannich base could be a better GPR17 agonist than MDL29,951, and further uncovering their pharmacological properties could potentiate an inventive GBM treatment.

G-protein-coupled receptor GPR17 inhibits glioma development by increasing polycomb repressive complex 1-mediated ROS production

Glioma is the most common primary tumor in the central nervous system. However, the development of glioma and effective therapeutic strategies remain elusive. Here, we identify GPR17 as a potential target to treat glioma. Data mining with human LGG and GBM samples reveals that GPR17 is negatively correlated with glioma development. Overexpressing GPR17 inhibits glioma cell proliferation and induces apoptosis by raising ROS levels. GPR17-overexpressing glioma cells are less tumorigenic in the brain than in control cells. Mechanistically, GPR17 inhibits the transcription of RNF2, a key component in the PRC1 complex, through cAMP/PKA/NF-κB signaling, leading to reduced histone H2A monoubiquitination. ChIP-Seq and RNA-Seq analyses reveal KLF9 as a direct target of RNF2. KLF9 mediates the functions of GPR17 and RNF2 in glioma cells. Furthermore, activation of GPR17 by its agonist inhibits glioma formation. Our findings have thus identified GPR17 as a key regulator of glioma development and a potential therapeutic target for gliomas.