ABSTRACT
ASCT2 (alanine serine cysteine transporter 2), a member of the solute carrier 1 family, mediates Na+-dependent exchange of small neutral amino acids across cell membranes. ASCT2 was shown to be highly expressed in tumor cells, making it a promising target for anticancer therapies. In this study, we explored the binding mechanism of the high-affinity competitive inhibitor L-cis hydroxyproline biphenyl ester (Lc-BPE) with ASCT2, using electrophysiological and rapid kinetic methods. Our investigations reveal that Lc-BPE binding requires one or two Na+ ions initially bound to the apo-transporter with high affinity, with Na1 site occupancy being more critical for inhibitor binding. In contrast to the amino acid substrate bound form, the final, third Na+ ion cannot bind, due to distortion of its binding site (Na2), thus preventing the formation of a translocation-competent complex. Based on the rapid kinetic analysis, the application of Lc-BPE generated outward transient currents, indicating that despite its net neutral nature, the binding of Lc-BPE in ASCT2 is weakly electrogenic, most likely because of asymmetric charge distribution within the amino acid moiety of the inhibitor. The preincubation with Lc-BPE also led to a decrease of the turnover rate of substrate exchange and a delay in the activation of substrate-induced anion current, indicating relatively slow Lc-BPE dissociation kinetics. Overall, our results provide new insight into the mechanism of binding of a prototypical competitive inhibitor to the ASCT transporters.
Subject(s)
Amino Acid Transport System ASC , Minor Histocompatibility Antigens , Amino Acid Transport System ASC/metabolism , Amino Acid Transport System ASC/antagonists & inhibitors , Amino Acid Transport System ASC/genetics , Amino Acid Transport System ASC/chemistry , Kinetics , Minor Histocompatibility Antigens/metabolism , Minor Histocompatibility Antigens/genetics , Minor Histocompatibility Antigens/chemistry , Humans , Sodium/metabolism , Sodium/chemistry , Animals , Binding, CompetitiveABSTRACT
As a conformationally restricted amino acid, hydroxy-l-proline is a versatile scaffold for the synthesis of diverse multi-functionalized pyrrolidines for probing the ligand binding sites of biological targets. With the goal to develop new inhibitors of the widely expressed amino acid transporters SLC1A4 and SLC1A5 (also known as ASCT1 and ASCT2), we synthesized and functionally screened synthetic hydroxy-l-proline derivatives using electrophysiological and radiolabeled uptake methods against amino acid transporters from the SLC1, SLC7, and SLC38 solute carrier families. We have discovered a novel class of alkoxy hydroxy-pyrrolidine carboxylic acids (AHPCs) that act as selective high-affinity inhibitors of the SLC1 family neutral amino acid transporters SLC1A4 and SLC1A5. AHPCs were computationally docked into a homology model and assessed with respect to predicted molecular orientation and functional activity. The series of hydroxyproline analogs identified here represent promising new agents to pharmacologically modulate SLC1A4 and SLC1A5 amino acid exchangers which are implicated in numerous pathophysiological processes such as cancer and neurological diseases.
Subject(s)
Amino Acid Transport System ASC , Drug Discovery , Minor Histocompatibility Antigens , Animals , Humans , Amino Acid Transport System ASC/antagonists & inhibitors , Amino Acid Transport System ASC/chemistry , HEK293 Cells , Minor Histocompatibility Antigens/metabolism , Minor Histocompatibility Antigens/chemistry , Molecular Docking Simulation , Proline/chemistry , Proline/analogs & derivatives , Pyrrolidines/chemistry , Pyrrolidines/pharmacology , Pyrrolidines/chemical synthesis , Structure-Activity RelationshipABSTRACT
Pancreatic cancer is a highly fatal disease, and existing treatment methods are ineffective, so it is urgent to develop new effective treatment strategies. The high dependence of pancreatic cancer cells on glucose and glutamine suggests that disrupting this dependency could serve as an alternative strategy for pancreatic cancer therapy. We identified the vital genes glucose transporter 1 (GLUT1) and alanine-serine-cysteine transporter 2 (ASCT2) through bioinformatics analysis, which regulate glucose and glutamine metabolism in pancreatic cancer, respectively. Human serum albumin nanoparticles (HSA NPs) for delivery of GLUT1 and ASCT2 inhibitors, BAY-876/V-9302@HSA NPs, were prepared by a self-assembly process. This nanodrug inhibits glucose and glutamine uptake of pancreatic cancer cells through the released BAY-876 and V-9302, leading to nutrition deprivation and oxidative stress. The inhibition of glutamine leads to the inhibition of the synthesis of the glutathione, which further aggravates oxidative stress. Both of them lead to a significant increase in reactive oxygen species, activating caspase 1 and GSDMD and finally inducing pyroptosis. This study provides a new effective strategy for orthotopic pancreatic cancer treatment by dual starvation-induced pyroptosis. The study for screening metabolic targets using bioinformatics analysis followed by constructing nanodrugs loaded with inhibitors will inspire future targeted metabolic therapy for pancreatic cancer.
Subject(s)
Glucose , Glutamine , Pancreatic Neoplasms , Pyroptosis , Pancreatic Neoplasms/drug therapy , Pancreatic Neoplasms/metabolism , Pancreatic Neoplasms/pathology , Humans , Glutamine/chemistry , Glutamine/metabolism , Glucose/metabolism , Pyroptosis/drug effects , Amino Acid Transport System ASC/metabolism , Amino Acid Transport System ASC/antagonists & inhibitors , Nanoparticles/chemistry , Glucose Transporter Type 1/metabolism , Glucose Transporter Type 1/antagonists & inhibitors , Cell Line, Tumor , Antineoplastic Agents/pharmacology , Antineoplastic Agents/chemistry , Minor Histocompatibility Antigens/metabolism , Amino Acid Transport System y+ABSTRACT
BACKGROUND: Mitochondrial dynamics play a fundamental role in determining stem cell fate. However, the underlying mechanisms of mitochondrial dynamics in the stemness acquisition of cancer cells are incompletely understood. METHODS: Metabolomic profiling of cells were analyzed by MS/MS. The genomic distribution of H3K27me3 was measured by CUT&Tag. Oral squamous cell carcinoma (OSCC) cells depended on glucose or glutamine fueling TCA cycle were monitored by 13C-isotope tracing. Organoids and tumors from patients and mice were treated with DRP1 inhibitors mdivi-1, ferroptosis inducer erastin, or combination with mdivi-1 and erastin to evaluate treatment effects. RESULTS: Mitochondria of OSCC stem cells own fragment mitochondrial network and DRP1 is required for maintenance of their globular morphology. Imbalanced mitochondrial dynamics induced by DRP1 knockdown suppressed stemness of OSCC cells. Elongated mitochondria increased α-ketoglutarate levels and enhanced glutaminolysis to fuel the TCA cycle by increasing glutamine transporter ASCT2 expression. α-KG promoted the demethylation of histone H3K27me3, resulting in downregulation of SNAI2 associated with stemness and EMT. Significantly, suppressing DRP1 enhanced the anticancer effects of ferroptosis. CONCLUSION: Our study reveals a novel mechanism underlying mitochondrial dynamics mediated cancer stemness acquisition and highlights the therapeutic potential of mitochondria elongation to increase the susceptibility of cancer cells to ferroptosis.
Subject(s)
Carcinoma, Squamous Cell , Dynamins , Ferroptosis , Glutamine , Mitochondria , Mitochondrial Dynamics , Mouth Neoplasms , Neoplastic Stem Cells , Ferroptosis/drug effects , Humans , Mouth Neoplasms/pathology , Mouth Neoplasms/metabolism , Mouth Neoplasms/genetics , Mouth Neoplasms/drug therapy , Animals , Dynamins/antagonists & inhibitors , Dynamins/genetics , Dynamins/metabolism , Mice , Glutamine/metabolism , Mitochondria/metabolism , Mitochondria/drug effects , Neoplastic Stem Cells/metabolism , Neoplastic Stem Cells/pathology , Neoplastic Stem Cells/drug effects , Cell Line, Tumor , Mitochondrial Dynamics/drug effects , Carcinoma, Squamous Cell/pathology , Carcinoma, Squamous Cell/metabolism , Carcinoma, Squamous Cell/genetics , Carcinoma, Squamous Cell/drug therapy , Citric Acid Cycle/drug effects , Amino Acid Transport System ASC/metabolism , Amino Acid Transport System ASC/genetics , Amino Acid Transport System ASC/antagonists & inhibitors , Ketoglutaric Acids/metabolism , Quinazolinones/pharmacology , Minor Histocompatibility Antigens/metabolism , Minor Histocompatibility Antigens/genetics , Piperazines/pharmacology , Squamous Cell Carcinoma of Head and Neck/pathology , Squamous Cell Carcinoma of Head and Neck/metabolism , Squamous Cell Carcinoma of Head and Neck/genetics , Squamous Cell Carcinoma of Head and Neck/drug therapyABSTRACT
Breast cancer (BC) is the most frequently diagnosed cancer in women. Increasing evidence suggests that circular RNA (circRNA) exerts critical functions in BC progression. However, the roles of circRNA septin 9 (circSEPT9) in BC development and the underneath mechanism remain largely unclear so far. In this work, the RNA levels of circSEPT9, microRNA-149-5p (miR-149-5p) and solute carrier family 1 member 5 (SLC1A5) were detected by quantitative real-time polymerase chain reaction. Western blot was performed to check protein expression. Glutamine uptake, cell proliferation and cell apoptosis were investigated by glutamine uptake, cell counting kit-8, cell colony formation, 5-Ethynyl-29-deoxyuridine, flow cytometry analysis or DNA content quantitation assay. The interactions of miR-149-5p with circSEPT9 and SLC1A5 were identified by a dual-luciferase reporter assay. Mouse model assay was carried out to analyze the effect of circSEPT9 on tumor formation in vivo. Results showed that circSEPT9 and SLC1A5 expression were significantly upregulated, while miR-149-5p was downregulated in BC tissues and cells as compared with paracancerous normal breast tissues and human normal breast cells. Knockdown of circSEPT9 or SLC1A5 inhibited glutamine uptake and cell proliferation, but induced cell apoptosis in BC cells. SLC1A5 overexpression relieved circSEPT9 silencing-induced repression of BC cell malignancy. In mechanism, circSEPT9 regulated SLC1A5 expression by sponging miR-149-5p. In support, circSEPT9 knockdown led to delayed tumor tumorigenesis in vivo. In summary, these results indicates that circSEPT9 may act an oncogenic role in BC malignant progression by regulating miR-149-5p/SLC1A5 pathway, providing a novel mechanism responsible for BC development.
Subject(s)
Amino Acid Transport System ASC/genetics , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , MicroRNAs/metabolism , Minor Histocompatibility Antigens/genetics , RNA, Circular/metabolism , Amino Acid Transport System ASC/antagonists & inhibitors , Amino Acid Transport System ASC/metabolism , Animals , Apoptosis/genetics , Base Sequence , Cell Line, Tumor , Cell Proliferation/genetics , Dipeptides/pharmacology , Disease Progression , Female , Gene Silencing/drug effects , Glutamine/metabolism , Humans , Mice, Inbred BALB C , Mice, Nude , MicroRNAs/genetics , Minor Histocompatibility Antigens/metabolism , Protein Binding/drug effects , RNA, Circular/genetics , RNA, Messenger/genetics , RNA, Messenger/metabolismABSTRACT
ASCT2 (SLC1A5) is a sodium-dependent neutral amino acid transporter that controls amino acid homeostasis in peripheral tissues. In cancer, ASCT2 is up-regulated where it modulates intracellular glutamine levels, fueling cell proliferation. Nutrient deprivation via ASCT2 inhibition provides a potential strategy for cancer therapy. Here, we rationally designed stereospecific inhibitors exploiting specific subpockets in the substrate binding site using computational modeling and cryo-electron microscopy (cryo-EM). The final structures combined with molecular dynamics simulations reveal multiple pharmacologically relevant conformations in the ASCT2 binding site as well as a previously unknown mechanism of stereospecific inhibition. Furthermore, this integrated analysis guided the design of a series of unique ASCT2 inhibitors. Our results provide a framework for future development of cancer therapeutics targeting nutrient transport via ASCT2, as well as demonstrate the utility of combining computational modeling and cryo-EM for solute carrier ligand discovery.
Subject(s)
Amino Acid Transport System ASC/antagonists & inhibitors , Binding, Competitive , Computational Chemistry , Cryoelectron Microscopy/methods , Glutamine/metabolism , Pharmaceutical Preparations/administration & dosage , Amino Acid Transport System ASC/metabolism , Binding Sites , Drug Design , Humans , Minor Histocompatibility Antigens/metabolism , Molecular Docking Simulation , Pharmaceutical Preparations/chemistry , Protein Binding , Protein Domains , Protein Structure, Tertiary , Structure-Activity RelationshipABSTRACT
Cancer cells are metabolically vigorous and are superior in the uptake of nutrients and in the release of the tumor microenvironment (TME)-specific metabolites. They create an acidic, hypoxic, and nutrient-depleted TME that makes it difficult for the cytotoxic immune cells to adapt to the metabolically hostile environment. Since a robust metabolism in immune cells is required for optimal anti-tumor effector functions, the challenges caused by the TME result in severe defects in the invasion and destruction of the established tumors. There have been many recent developments in NK and T cell-mediated immunotherapy, such as engineering them to express chimeric antigen receptors (CARs) to enhance tumor-recognition and infiltration. However, to defeat the tumor and overcome the limitations of the TME, it is essential to fortify these novel therapies by improving the metabolism of the immune cells. One potential strategy to enhance the metabolic fitness of immune cells is to upregulate the expression of nutrient transporters, specifically glucose and amino acid transporters. In particular, the amino acid transporters SLC1A5 and SLC7A5 as well as the ancillary subunit SLC3A2, which are required for efficient uptake of glutamine and leucine respectively, could strengthen the metabolic capabilities and effector functions of tumor-directed CAR-NK and T cells. In addition to enabling the influx and efflux of essential amino acids through the plasma membrane and within subcellular compartments such as the lysosome and the mitochondria, accumulating evidence has demonstrated that the amino acid transporters participate in sensing amino acid levels and thereby activate mTORC1, a master metabolic regulator that promotes cell metabolism, and induce the expression of c-Myc, a transcription factor essential for cell growth and proliferation. In this review, we discuss the regulatory pathways of these amino acid transporters and how we can take advantage of these processes to strengthen immunotherapy against cancer.
Subject(s)
Amino Acid Transport System ASC/antagonists & inhibitors , Amino Acids/metabolism , Antineoplastic Agents/therapeutic use , Fusion Regulatory Protein 1, Heavy Chain/antagonists & inhibitors , Immunotherapy, Adoptive , Large Neutral Amino Acid-Transporter 1/drug effects , Neoplasms/drug therapy , Tumor Microenvironment , Amino Acid Transport System ASC/metabolism , Animals , Energy Metabolism/drug effects , Fusion Regulatory Protein 1, Heavy Chain/metabolism , Humans , Killer Cells, Natural/immunology , Killer Cells, Natural/metabolism , Killer Cells, Natural/transplantation , Large Neutral Amino Acid-Transporter 1/metabolism , Minor Histocompatibility Antigens/metabolism , Molecular Targeted Therapy , Neoplasms/immunology , Neoplasms/metabolism , Neoplasms/pathology , Receptors, Chimeric Antigen/genetics , Receptors, Chimeric Antigen/metabolism , T-Lymphocytes/immunology , T-Lymphocytes/metabolism , T-Lymphocytes/transplantationABSTRACT
Proteasome inhibitors (PIs), used in the treatment of plasma cell myeloma (PCM), interfere with the degradation of misfolded proteins leading to activation of unfolded protein response (UPR) and cell death. However, despite initial strong antimyeloma effects, PCM cells eventually develop acquired resistance to PIs. The pleiotropic role of Ê-glutamine (Gln) in cellular functions makes inhibition of Gln metabolism a potentially good candidate for combination therapy. Here, we show that PCM cells, both sensitive and resistant to PIs, express membrane Gln transporter (ASCT2), require extracellular Gln for survival, and are sensitive to ASCT2 inhibitors (ASCT2i). ASCT2i synergistically potentiate the cytotoxic activity of PIs by inducing apoptosis and modulating autophagy. Combination of ASCT2 inhibitor V9302 and proteasome inhibitor carfilzomib upregulates the intracellular levels of ROS and oxidative stress markers and triggers catastrophic UPR as shown by upregulated spliced Xbp1 mRNA, ATF3 and CHOP levels. Moreover, analysis of RNA sequencing revealed that the PI in combination with ASCT2i reduced the levels of Gln metabolism regulators such as MYC and NRAS. Analysis of PCM patients' data revealed that upregulated ASCT2 and other Gln metabolism regulators are associated with advanced disease stage and with PIs resistance. Altogether, we identified a potent therapeutic approach that may prevent acquired resistance to PIs and may contribute to the improvement of treatment of patients suffering from PCM.
Subject(s)
Amino Acid Transport System ASC/antagonists & inhibitors , Antineoplastic Combined Chemotherapy Protocols/pharmacology , Bortezomib/pharmacology , Glutamine/analogs & derivatives , Glutamine/metabolism , Multiple Myeloma/drug therapy , Oligopeptides/pharmacology , Proteasome Endopeptidase Complex/metabolism , Proteasome Inhibitors/pharmacology , Amino Acid Transport System ASC/genetics , Amino Acid Transport System ASC/metabolism , Apoptosis/drug effects , Autophagy/drug effects , Cell Line, Tumor , Drug Resistance, Neoplasm , Drug Synergism , Endoplasmic Reticulum Stress/drug effects , Glutamine/pharmacology , Humans , Minor Histocompatibility Antigens/genetics , Minor Histocompatibility Antigens/metabolism , Multiple Myeloma/enzymology , Multiple Myeloma/genetics , Multiple Myeloma/pathology , Oxidative Stress/drug effects , Unfolded Protein Response/drug effectsABSTRACT
Cancer cells are metabolically reprogrammed to support their high rates of proliferation, continuous growth, survival, invasion, metastasis, and resistance to cancer treatments. Among changes in cancer cell bioenergetics, the role of glutamine metabolism has been receiving increasing attention. Increased glutaminolysis in cancer cells is associated with increased expression of membrane transporters that mediate the cellular uptake of glutamine. ASCT2 (Alanine, Serine, Cysteine Transporter 2) is a Na+-dependent transmembrane transporter overexpressed in cancer cells and considered to be the primary transporter for glutamine in these cells. The possibility of inhibiting ASCT2 for antineoplastic therapy is currently under investigation. In this article, we will present the pharmacological agents currently known to act on ASCT2, which have been attracting attention in antineoplastic therapy research. We will also address the impact of ASCT2 inhibition on the prognosis of some cancers. We conclude that ASCT2 inhibition and combination of ASCT2 inhibitors with other anti-tumor therapies may be a promising antineoplastic strategy. However, more research is needed in this area.
Subject(s)
Amino Acid Transport System ASC/antagonists & inhibitors , Glutamine/metabolism , Neoplasms/drug therapy , Amino Acid Transport System ASC/physiology , Animals , Antibodies, Monoclonal/therapeutic use , Humans , Minor Histocompatibility Antigens/physiology , Neoplasms/metabolism , Oxidative StressABSTRACT
Muscle regeneration is sustained by infiltrating macrophages and the consequent activation of satellite cells1-4. Macrophages and satellite cells communicate in different ways1-5, but their metabolic interplay has not been investigated. Here we show, in a mouse model, that muscle injuries and ageing are characterized by intra-tissue restrictions of glutamine. Low levels of glutamine endow macrophages with the metabolic ability to secrete glutamine via enhanced glutamine synthetase (GS) activity, at the expense of glutamine oxidation mediated by glutamate dehydrogenase 1 (GLUD1). Glud1-knockout macrophages display constitutively high GS activity, which prevents glutamine shortages. The uptake of macrophage-derived glutamine by satellite cells through the glutamine transporter SLC1A5 activates mTOR and promotes the proliferation and differentiation of satellite cells. Consequently, macrophage-specific deletion or pharmacological inhibition of GLUD1 improves muscle regeneration and functional recovery in response to acute injury, ischaemia or ageing. Conversely, SLC1A5 blockade in satellite cells or GS inactivation in macrophages negatively affects satellite cell functions and muscle regeneration. These results highlight the metabolic crosstalk between satellite cells and macrophages, in which macrophage-derived glutamine sustains the functions of satellite cells. Thus, the targeting of GLUD1 may offer therapeutic opportunities for the regeneration of injured or aged muscles.
Subject(s)
Glutamine/metabolism , Macrophages/metabolism , Muscle, Skeletal/metabolism , Regeneration , Satellite Cells, Skeletal Muscle/metabolism , Aging/metabolism , Amino Acid Transport System ASC/antagonists & inhibitors , Amino Acid Transport System ASC/metabolism , Animals , Cell Differentiation , Cell Proliferation , Female , Glutamate Dehydrogenase/deficiency , Glutamate Dehydrogenase/genetics , Glutamate Dehydrogenase/metabolism , Glutamate-Ammonia Ligase/antagonists & inhibitors , Glutamate-Ammonia Ligase/metabolism , Macrophages/enzymology , Male , Mice , Minor Histocompatibility Antigens/metabolism , Muscle, Skeletal/cytology , Muscle, Skeletal/injuries , Muscle, Skeletal/pathology , Oxidation-Reduction , Satellite Cells, Skeletal Muscle/cytology , TOR Serine-Threonine KinasesABSTRACT
The dependency of cancer cells on glutamine may be exploited therapeutically as a new strategy for treating cancers that lack druggable driver genes. Here we found that human liver cancer was dependent on extracellular glutamine. However, targeting glutamine addiction using the glutaminase inhibitor CB-839 as monotherapy had a very limited anticancer effect, even against the most glutamine addicted human liver cancer cells. Using a chemical library, we identified V-9302, a novel inhibitor of glutamine transporter ASCT2, as sensitizing glutamine dependent (GD) cells to CB-839 treatment. Mechanically, a combination of CB-839 and V-9302 depleted glutathione and induced reactive oxygen species (ROS), resulting in apoptosis of GD cells. Moreover, this combination also showed tumor inhibition in HCC xenograft mouse models in vivo. Our findings indicate that dual inhibition of glutamine metabolism by targeting both glutaminase and glutamine transporter ASCT2 represents a potential novel treatment strategy for glutamine addicted liver cancers.
Subject(s)
Antineoplastic Agents/pharmacology , Glutamine/metabolism , Liver Neoplasms/metabolism , Amino Acid Transport System ASC/antagonists & inhibitors , Animals , Apoptosis/drug effects , Benzeneacetamides/pharmacology , Carrier Proteins/antagonists & inhibitors , Cell Line, Tumor , Drug Synergism , Glutaminase/antagonists & inhibitors , Humans , Mice , Minor Histocompatibility Antigens , Reactive Oxygen Species/metabolism , Thiadiazoles/pharmacology , Xenograft Model Antitumor AssaysABSTRACT
Glutamine metabolism, described as major energy and building blocks supply to cell growth, has gained great attention. Alanine-Serine-Cysteine Transporter (ASCT2), which belongs to solute carried (SLC) family transporters and is encoded by the SLC1A5 gene serves as a significant role for glutamine transport. Indeed, ASCT2 is often overexpressed in highly proliferative cancer cells to fulfill enhanced glutamine demand. So far, ASCT2 has been proved to be a significant target during the carcinogenesis process, and emerging evidence reveals that ASCT2 inhibitors can provide a benefit strategy for cancer therapy. Herein, we describe the structure of ASCT2, and summarize its related regulatory factors which are associated with antitumor activity. Moreover, this review article highlights the remarkable reform of discovery and development for ASCT2 inhibitors. On the basis of case studies, our perspectives for targeting ASCT2 and development of ASCT2 antagonist are discussed in the final part.
Subject(s)
Amino Acid Transport System ASC/drug effects , Amino Acid Transport System ASC/genetics , Antineoplastic Agents/pharmacology , Minor Histocompatibility Antigens/drug effects , Minor Histocompatibility Antigens/genetics , Neoplasms/genetics , Amino Acid Transport System ASC/antagonists & inhibitors , Amino Acid Transport System ASC/chemistry , Animals , Carcinogenesis/drug effects , Carcinogenesis/genetics , Gene Expression Regulation , Humans , Minor Histocompatibility Antigens/chemistryABSTRACT
The purpose of the present study was to evaluate the anti-cancer property of Lobetyolin on colorectal cancer and explore its potential mechanism. Lobetyolin was incubated with HCT-116 cells in the absence or presence of ASCT2 inhibitor Benser or p53 inhibitor Pifithrin-α. The levels of glutamine, glutamic acid, α-ketoglutarate, ATP and GSH were determined to measure the glutamine metabolism. Annexin V-FITC/PI staining and TUNEL assay were applied to estimate the apoptotic condition. The levels of ASCT2 were examined by RT-qPCR, Western blot and immunofluorescence staining. The expressions of cleaved-caspase-3, caspase-3, cleaved-caspase-7, caspase-7, cleaved-PARP, PARP, p53, p21, bax and survivin were detected using Western blot analysis. As a result, the treatment with Lobetyolin effectively induced apoptosis and glutamine metabolism in HCT-116 cells through ASCT2 signalling. The inhibition of ASCT2 reduced the glutamine-related biomarkers and augmented the apoptotic process. We further found that the effect of Lobetyolin on HCT-116 was related to the expressions of p21 and bax, and transportation of p53 to nucleus. The inhibition of p53 by Pifithrin-α promoted the inhibitory effect of Lobetyolin on ASCT2-mediated apoptosis. Lobetyolin also exerted anti-cancer property in nude mice. In conclusion, the present work suggested that Lobetyolin could induce the apoptosis via the inhibition of ASCT2-mediated glutamine metabolism, which was possibly governed by p53.
Subject(s)
Amino Acid Transport System ASC/antagonists & inhibitors , Antineoplastic Agents/pharmacology , Apoptosis/physiology , Colonic Neoplasms/drug therapy , Glutamine/metabolism , Polyynes/pharmacology , Tumor Suppressor Protein p53/antagonists & inhibitors , Animals , Benzothiazoles/pharmacology , Cell Line, Tumor , Colonic Neoplasms/pathology , HCT116 Cells , Humans , Mice , Mice, Nude , Minor Histocompatibility Antigens , Toluene/analogs & derivatives , Toluene/pharmacologyABSTRACT
The Solute Carrier 1A (SLC1A) family includes two major mammalian transport systems-the alanine serine cysteine transporters (ASCT1-2) and the human glutamate transporters otherwise known as the excitatory amino acid transporters (EAAT1-5). The EAATs play a critical role in maintaining low synaptic concentrations of the major excitatory neurotransmitter glutamate, and hence they have been widely researched over a number of years. More recently, the neutral amino acid exchanger, ASCT2 has garnered attention for its important role in cancer biology and potential as a molecular target for cancer therapy. The nature of this role is still being explored, and several classes of ASCT2 inhibitors have been developed. However none have reached sufficient potency or selectivity for clinical use. Despite their distinct functions in biology, the members of the SLC1A family display structural and functional similarity. Since 2004, available structures of the archaeal homologues GltPh and GltTk have elucidated mechanisms of transport and inhibition common to the family. The recent determination of EAAT1 and ASCT2 structures may be of assistance in future efforts to design efficacious ASCT2 inhibitors. This review will focus on ASCT2, the present state of knowledge on its roles in tumour biology, and how structural biology is being used to progress the development of inhibitors.
Subject(s)
Amino Acid Transport System ASC/metabolism , Antineoplastic Agents/metabolism , Excitatory Amino Acid Transporter 3/metabolism , Excitatory Amino Acid Transporter 5/metabolism , Neoplasms/metabolism , Amino Acid Transport System ASC/antagonists & inhibitors , Amino Acid Transport System ASC/chemistry , Amino Acid Transport Systems/chemistry , Amino Acid Transport Systems/metabolism , Animals , Antineoplastic Agents/administration & dosage , Antineoplastic Agents/chemistry , Excitatory Amino Acid Transporter 3/chemistry , Excitatory Amino Acid Transporter 5/antagonists & inhibitors , Excitatory Amino Acid Transporter 5/chemistry , Humans , Neoplasms/drug therapy , Protein Structure, Tertiary , Structure-Activity RelationshipABSTRACT
KRAS mutations are detected in numerous human cancers, but there are few effective drugs for KRAS-mutated cancers. Transporters for amino acids and glucose are highly expressed on cancer cells, possibly to maintain rapid cell growth and metabolism. Alanine-serine-cysteine transporter 2 (ASCT2) is a primary transporter for glutamine in cancer cells. In this study, we developed a novel monoclonal antibody (mAb) recognizing the extracellular domain of human ASCT2, and investigated whether ASCT2 can be a therapeutic target for KRAS-mutated cancers. Rats were immunized with RH7777 rat hepatoma cells expressing human ASCT2 fused to green fluorescent protein (GFP). Splenocytes from the immunized rats were fused with P3X63Ag8.653 mouse myeloma cells, and selected and cloned hybridoma cells secreting Ab3-8 mAb were established. This mAb reacted with RH7777 transfectants expressing ASCT2-GFP proteins in a GFP intensity-dependent manner. Ab3-8 reacted with various human cancer cells, but not with non-cancer breast epithelial cells or ASCT2-knocked out HEK293 and SW1116 cells. In SW1116 and HCT116 human colon cancer cells with KRAS mutations, treatment with Ab3-8 reduced intracellular glutamine transport, phosphorylation of AKT and ERK, and inhibited in vivo tumor growth of these cells in athymic mice. Inhibition of in vivo tumor growth by Ab3-8 was not observed in HT29 colon and HeLa uterus cancer cells with wild-type KRAS. These results suggest that ASCT2 is an excellent therapeutic target for KRAS-mutated cancers.
Subject(s)
Amino Acid Transport System ASC/antagonists & inhibitors , Antibodies, Monoclonal/pharmacology , Antineoplastic Agents/pharmacology , Colorectal Neoplasms/drug therapy , Proto-Oncogene Proteins p21(ras)/genetics , Amino Acid Transport System ASC/genetics , Amino Acid Transport System ASC/metabolism , Animals , Antibodies, Monoclonal/isolation & purification , Antibodies, Monoclonal/therapeutic use , Antineoplastic Agents/isolation & purification , Antineoplastic Agents/therapeutic use , Cell Line, Tumor , Colorectal Neoplasms/genetics , Colorectal Neoplasms/pathology , Female , Gene Knockout Techniques , Glutamine/metabolism , HEK293 Cells , Humans , Mice , Minor Histocompatibility Antigens/genetics , Minor Histocompatibility Antigens/metabolism , Molecular Targeted Therapy/methods , Mutation , Xenograft Model Antitumor AssaysABSTRACT
Experiment and modeling were combined to understand inhibition of the alanine-serine-cysteine-1 (asc1) transporter. The structure-activity relationship (SAR) was explored with synthesis of analogues of BMS-466442. Direct target interaction and binding site location between TM helices 6 and 10 were confirmed via site directed mutagenesis. Computational modeling suggested the inhibitor binds via competitive occupation of the orthosteric site while also blocking the movement of TM helices that are required for transport.
Subject(s)
Amino Acid Transport System ASC/antagonists & inhibitors , Amino Acid Transport System y+/antagonists & inhibitors , Histidine/analogs & derivatives , Indoles/pharmacology , Animals , Binding Sites , Cells, Cultured , Histidine/pharmacology , Humans , Rats , Structure-Activity RelationshipABSTRACT
The neutral amino acid transporter alanine serine cysteine transporter 2 (ASCT2) belongs to the solute carrier 1 (SLC1) family of transport proteins and transports neutral amino acids, such as alanine and glutamine, into the cell in exchange with intracellular amino acids. This amino acid transport is sodium dependent, but not driven by the transmembrane Na+ concentration gradient. Glutamine transport by ASCT2 is proposed to be important for glutamine homoeostasis in rapidly growing cancer cells to fulfill the energy and nitrogen demands of these cells. Thus, ASCT2 is thought to be a potential anticancer drug target. However, the pharmacology of the amino acid binding site is not well established. Here, we report on the synthesis and characterization of a novel class of ASCT2 inhibitors based on an amino acid scaffold with a sulfonamide/sulfonic acid ester linker to a hydrophobic group. The compounds were designed based on an improved ASCT2 homology model using the human glutamate transporter hEAAT1 crystal structure as a modeling template. The compounds were shown to inhibit with a competitive mechanism and a potency that scales with the hydrophobicity of the side chain. The most potent compound binds with an apparent affinity, K i, of 8 ± 4 µM and can block the alanine response with a K i of 40 ± 23 µM at 200 µM alanine concentration. Computational analysis predicts inhibitor interactions with the binding site through molecular docking. In conclusion, the sulfonamide/sulfonic acid ester scaffold provides facile synthetic access to ASCT2 inhibitors with a potentially large variability in chemical space of the hydrophobic side chain. These inhibitors will be useful chemical tools to further characterize the role of ASCT2 in disease as well as improve our understanding of inhibition mechanisms of this transporter.
Subject(s)
Amino Acid Transport System ASC/antagonists & inhibitors , Membrane Transport Modulators/pharmacology , Molecular Docking Simulation , Sulfonamides/pharmacology , Sulfonic Acids/pharmacology , Amino Acid Transport System ASC/chemistry , Amino Acid Transport System ASC/metabolism , Binding Sites , Esters/chemistry , HEK293 Cells , Humans , Membrane Transport Modulators/chemistry , Minor Histocompatibility Antigens/chemistry , Minor Histocompatibility Antigens/metabolism , Protein Binding , Sulfonamides/chemistry , Sulfonic Acids/chemistryABSTRACT
The N-methyl-d-aspartate receptor coagonist d-serine is a substrate for the neutral amino acid transporters ASCT1 and ASCT2, which may regulate its extracellular levels in the central nervous system (CNS). We tested inhibitors of ASCT1 and ASCT2 for their effects in rodent models of schizophrenia and visual dysfunction, which had previously been shown to be responsive to d-serine. L-4-fluorophenylglycine (L-4FPG), L-4-hydroxyPG (L-4OHPG), and L-4-chloroPG (L-4ClPG) all showed high plasma bioavailability when administered systemically to rats and mice. L-4FPG showed good brain penetration with brain/plasma ratios of 0.7-1.4; however, values for L-4OHPG and L-4ClPG were lower. Systemically administered L-4FPG potently reduced amphetamine-induced hyperlocomotion in mice, whereas L-4OHPG was 100-fold less effective and L-4ClPG inactive at the doses tested. L-4FPG and L-4OHPG did not impair visual acuity in naive rats, and acute systemic administration of L-4FPG significantly improved the deficit in contrast sensitivity in blue light-treated rats caused by retinal degeneration. The ability of L-4FPG to penetrate the brain makes this compound a useful tool to further evaluate the function of ASCT1 and ASCT2 transporters in the CNS.
Subject(s)
Amino Acid Transport System ASC/antagonists & inhibitors , Schizophrenia/metabolism , Vision Disorders/metabolism , Animals , Brain/drug effects , Brain/metabolism , Glycine/pharmacology , Locomotion/drug effects , Male , Mice , Mice, Inbred C57BL , Minor Histocompatibility Antigens , Rats , Rats, Long-Evans , Rats, Sprague-Dawley , Receptors, N-Methyl-D-Aspartate/antagonists & inhibitors , Schizophrenia/drug therapy , Serine/pharmacology , Vision Disorders/drug therapyABSTRACT
Cisplatin is one of the most effective chemotherapeutic drugs used in the treatment of HCC, but many patients will ultimately relapse with cisplatin-resistant disease. Used in combination with cisplatin, resveratrol has synergistic effect of increasing chemosensitivity of cisplatin in various cancer cells. However, the mechanisms of resveratrol enhancing cisplatininduced toxicity have not been well characterized. Our study showed that resveratrol enhances cisplatin toxicity in human hepatoma cells via an apoptosis-dependent mechanism. Further studies reveal that resveratrol decreases the absorption of glutamine and glutathione content by reducing the expression of glutamine transporter ASCT2. Flow cytometric analyses demonstrate that resveratrol and cisplatin combined treatment leads to a significant increase in ROS production compared to resveratrol or cisplatin treated hepatoma cells alone. Phosphorylated H2AX (γH2AX) foci assay demonstrate that both resveratrol and cisplatin treatment result in a significant increase of γH2AX foci in hepatoma cells, and the resveratrol and cisplatin combined treatment results in much more γH2AX foci formation than either resveratrol or cisplatin treatment alone. Furthermore, our studies show that over-expression of ASCT2 can attenuate cisplatin-induced ROS production, γH2AX foci formation and apoptosis in human hepatoma cells. Collectively, our studies suggest resveratrol may sensitize human hepatoma cells to cisplatin chemotherapy via glutamine metabolism inhibition. [BMB Reports 2018; 51(9): 474-479].