The role of ASCT2 in cancer: A review

Tumor Metabolism: A New Field for the Treatment of Glioma

The clinical treatment of glioma remains relatively immature. Commonly used clinical treatments for gliomas are surgery combined with chemotherapy and radiotherapy, but there is a problem of drug resistance. In addition, immunotherapy and targeted therapies also suffer from the problem of immune evasion. The advent of metabolic therapy holds immense potential for advancing more efficacious and tolerable therapies against this aggressive disease. Metabolic therapy alters the metabolic processes of tumor cells at the molecular level to inhibit tumor growth and spread, and lead to better outcomes for patients with glioma that are insensitive to conventional treatments. Moreover, compared with conventional therapy, it has less impact on normal cells, less toxicity and side effects, and higher safety. The objective of this review is to examine the changes in metabolic characteristics throughout the development of glioma, enumerate the current methodologies employed for studying tumor metabolism, and highlight the metabolic reprogramming pathways of glioma along with their potential molecular mechanisms. Importantly, it seeks to elucidate potential metabolic targets for glioblastoma (GBM) therapy and summarize effective combination treatment strategies based on various studies.

Asparagine transport through SLC1A5/ASCT2 and SLC38A5/SNAT5 is essential for BCP-ALL cell survival and a potential therapeutic target

B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) blasts strictly depend on the transport of extra-cellular asparagine (Asn), yielding a rationale for L-asparaginase (ASNase) therapy. However, the carriers used by ALL blasts for Asn transport have not been identified yet. Exploiting RS4;11 cells as BCP-ALL model, we have found that cell Asn is lowered by either silencing or inhibition of the transporters ASCT2 or SNAT5. The inhibitors V-9302 (for ASCT2) and GluγHA (for SNAT5) markedly lower cell proliferation and, when used together, suppress mTOR activity, induce autophagy and cause a severe nutritional stress, leading to a proliferative arrest and a massive cell death in both the ASNase-sensitive RS4;11 cells and the relatively ASNase-insensitive NALM-6 cells. The cytotoxic effect is not prevented by coculturing leukaemic cells with primary mesenchymal stromal cells. Leukaemic blasts of paediatric ALL patients express ASCT2 and SNAT5 at diagnosis and undergo marked cytotoxicity when exposed to the inhibitors. ASCT2 expression is positively correlated with the minimal residual disease at the end of the induction therapy. In conclusion, ASCT2 and SNAT5 are the carriers exploited by ALL cells to transport Asn, and ASCT2 expression is associated with a lower therapeutic response. ASCT2 may thus represent a novel therapeutic target in BCP-ALL.

The tRNA Gm18 methyltransferase TARBP1 promotes hepatocellular carcinoma progression via metabolic reprogramming of glutamine

Cancer cells rely on metabolic reprogramming to sustain the prodigious energetic requirements for rapid growth and proliferation. Glutamine metabolism is frequently dysregulated in cancers and is being exploited as a potential therapeutic target. Using CRISPR/Cas9 interference (CRISPRi) screening, we identified TARBP1 (TAR (HIV-1) RNA Binding Protein 1) as a critical regulator involved in glutamine reliance of cancer cell. Consistent with this discovery, TARBP1 amplification and overexpression are frequently observed in various cancers. Knockout of TARBP1 significantly suppresses cell proliferation, colony formation and xenograft tumor growth. Mechanistically, TARBP1 selectively methylates and stabilizes a small subset of tRNAs, which promotes efficient protein synthesis of glutamine transporter-ASCT2 (also known as SLC1A5) and glutamine import to fuel the growth of cancer cell. Moreover, we found that the gene expression of TARBP1 and ASCT2 are upregulated in combination in clinical cohorts and their upregulation is associated with unfavorable prognosis of HCC (hepatocellular carcinoma). Taken together, this study reveals the unexpected role of TARBP1 in coordinating the tRNA availability and glutamine uptake during HCC progression and provides a potential target for tumor therapy.

Elevated SLC1A5 associated with poor prognosis and therapeutic resistance to transarterial chemoembolization in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a common malignant tumor, and glutamine is vital for tumor cells. The role of glutamine transporter SLC1A5 in tumor progression and transarterial chemoembolization (TACE) efficacy is under study. This research seeks to determine the impact of SLC1A5 expression on the prognosis and TACE efficacy of HCC and elucidate its mechanisms.

METHODS

SLC1A5 expression in HCC, correlation with patient outcomes, and response to TACE were studied in an open access liver cancer dataset and confirmed in our cohort. Additionally, the correlation between SLC1A5 expression and hypoxia, angiogenesis and immune infiltration was analyzed and verified by immunohistochemistry, immunofluorescence and transcriptome sequencing. Liver cancer cell lines with SLC1A5 expression knockdown or overexpression were constructed, and cell proliferation, colony formation, apoptosis, migration and drug sensitivity as well as in vivo xenograft tumor were measured. A gene set enrichment analysis was conducted to determine the signaling pathway influenced by SLC1A5, and a western blot analysis was performed to detect protein expression alterations.

RESULTS

SLC1A5 expression was higher in HCC tissue and associated with poor survival and TACE resistance. Hypoxia could stimulate the upregulation of glutamine transport, angiogenesis and SLC1A5 expression. The SLC1A5 expression was positively correlated with hypoxia and angiogenesis-related genes, immune checkpoint pathways, macrophage, Tregs, and other immunosuppressive cells infiltration. Knockdown of SLC1A5 decreased proliferation, colony formation, and migration, but increased apoptosis and increased sensitivity to chemotherapy drugs. Downregulation of SLC1A5 resulted in a decrease in Vimentin and N-cadherin expression, yet an increase in E-cadherin expression. Upregulation of SLC1A5 increased Vimentin and N-cadherin expression, while decreasing E-cadherin. Overexpression of β-catenin in SLC1A5-knockdown HCC cell lines could augment Vimentin and N-cadherin expression, suppress E-cadherin expression, and increase the migration and drug resistance.

CONCLUSIONS

Elevated SLC1A5 was linked to TACE resistance and survival shortening in HCC patients. SLC1A5 was positively correlated with hypoxia, angiogenesis, and immunosuppression. SLC1A5 may mediate HCC cell migration and drug resistance via Epithelial-mesenchymal transition (EMT) pathway.

Metabolic reprogramming in the CLL TME; potential for new therapeutic targets

Chronic lymphocytic leukemia (CLL) cells circulate between peripheral (PB) blood and lymph node (LN) compartments, and strictly depend on microenvironmental factors for proliferation, survival and drug resistance. All cancer cells display metabolic reprogramming and CLL is no exception - though the inert status of the PB CLL cells has hampered detailed insight into these processes. We summarize previous work on reactive oxygen species (ROS), oxidative stress, and hypoxia, as well as the important roles of Myc, and PI3K/Akt/mTor pathways. In vitro co-culture systems and gene expression analyses have provided a partial picture of CLL LN metabolism. New broad omics techniques allow to obtain molecular and also single-cell level understanding of CLL plasticity and metabolic reprogramming. We summarize recent developments and describe the new concept of glutamine addiction for CLL, which may hold therapeutic promise.

Targeting metabolism to enhance immunotherapy within tumor microenvironment

Cancer metabolic reprogramming has been considered an emerging hallmark in tumorigenesis and the antitumor immune response. Like cancer cells, immune cells within the tumor microenvironment or premetastatic niche also undergo extensive metabolic reprogramming, which profoundly impacts anti-tumor immune responses. Numerous evidence has illuminated that immunosuppressive TME and the metabolites released by tumor cells, including lactic acid, Prostaglandin E2 (PGE2), fatty acids (FAs), cholesterol, D-2-Hydroxyglutaric acid (2-HG), adenosine (ADO), and kynurenine (KYN) can contribute to CD8+ T cell dysfunction. Dynamic alterations of these metabolites between tumor cells and immune cells can similarly initiate metabolic competition in the TME, leading to nutrient deprivation and subsequent microenvironmental acidosis, which impedes immune response. This review summarizes the new landscape beyond the classical metabolic pathways in tumor cells, highlighting the pivotal role of metabolic disturbance in the immunosuppressive microenvironment, especially how nutrient deprivation in TME leads to metabolic reprogramming of CD8+ T cells. Likewise, it emphasizes the current therapeutic targets or strategies related to tumor metabolism and immune response, providing therapeutic benefits for tumor immunotherapy and drug development in the future. Cancer metabolic reprogramming has been considered an emerging hallmark in tumorigenesis and the antitumor immune response. Dynamic alterations of metabolites between tumor cells and immune cells initiate metabolic competition in the TME, leading to nutrient deprivation and subsequent microenvironmental acidosis, which impedes immune response.

The Role of Metabolic Reprogramming in the Tumor Immune Microenvironment: Mechanisms and Opportunities for Immunotherapy in Hepatocellular Carcinoma

As one of the emerging hallmarks of tumorigenesis and tumor progression, metabolic remodeling is common in the tumor microenvironment. Hepatocellular carcinoma (HCC) is the third leading cause of global tumor-related mortality, causing a series of metabolic alterations in response to nutrient availability and consumption to fulfill the demands of biosynthesis and carcinogenesis. Despite the efficacy of immunotherapy in treating HCC, the response rate remains unsatisfactory. Recently, research has focused on metabolic reprogramming and its effects on the immune state of the tumor microenvironment, and immune response rate. In this review, we delineate the metabolic reprogramming observed in HCC and its influence on the tumor immune microenvironment. We discuss strategies aimed at enhancing response rates and overcoming immune resistance through metabolic interventions, focusing on targeting glucose, lipid, or amino acid metabolism, as well as systemic regulation.

Discovery and Synthesis of Hydroxy-l-Proline Blockers of the Neutral Amino Acid Transporters SLC1A4 (ASCT1) and SLC1A5 (ASCT2)

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.

Immunological Aspects of Cancer Cell Metabolism

Cancer cells adeptly manipulate their metabolic processes to evade immune detection, a phenomenon intensifying the complexity of cancer progression and therapy. This review delves into the critical role of cancer cell metabolism in the immune-editing landscape, highlighting how metabolic reprogramming facilitates tumor cells to thrive despite immune surveillance pressures. We explore the dynamic interactions within the tumor microenvironment (TME), where cancer cells not only accelerate their glucose and amino acid metabolism but also induce an immunosuppressive state that hampers effective immune response. Recent findings underscore the metabolic competition between tumor and immune cells, particularly focusing on how this interaction influences the efficacy of emerging immunotherapies. By integrating cutting-edge research on the metabolic pathways of cancer cells, such as the Warburg effect and glutamine addiction, we shed light on potential therapeutic targets. The review proposes that disrupting these metabolic pathways could enhance the response to immunotherapy, offering a dual-pronged strategy to combat tumor growth and immune evasion.

ASCT2-Targeting Antibody-Drug Conjugate MEDI7247 in Adult Patients with Relapsed/Refractory Hematological Malignancies: A First-in-Human, Phase 1 Study

BACKGROUND

MEDI7247 is a first-in-class antibody-drug conjugate (ADC) consisting of an anti-sodium-dependent alanine-serine-cysteine transporter 2 antibody-conjugated to a pyrrolobenzodiazepine dimer.

OBJECTIVE

This first-in-human phase 1 trial evaluated MEDI7247 in patients with hematological malignancies.

PATIENTS AND METHODS

Adults with acute myeloid leukemia (AML), multiple myeloma (MM), or diffuse large B-cell lymphoma (DLBCL) relapsed or refractory (R/R) to standard therapies, or for whom no standard therapy exists, were eligible. Primary endpoints were safety and determination of the maximum tolerated dose (MTD). Secondary endpoints included assessments of antitumor activity, pharmacokinetics (PK), and immunogenicity.

RESULTS

As of 26 March 2020, 67 patients were treated (AML: n = 27; MM: n = 18; DLBCL: n = 22). The most common MEDI7247-related adverse events (AEs) were thrombocytopenia (41.8%), neutropenia (35.8%), and anemia (28.4%). The most common treatment-related grade 3/4 AEs were thrombocytopenia (38.8%), neutropenia (34.3%), and anemia (22.4%). Anticancer activity (number of responders/total patients evaluated) was observed in 11/67 (16.4%) patients. No correlation was observed between ASCT2 expression and clinical response. Between-patient variability of systemic exposure of MEDI7247 ADC and total antibody were high (AUCinf geometric CV%: 62.3-134.2, and 74.8-126.1, respectively). SG3199 (PBD dimer) plasma concentrations were below the limit of quantification for all patients after Study Day 8. Anti-drug antibody (ADA) prevalence was 7.7%, ADA incidence was 1.9%, and persistent-positive ADA was 5.8%.

CONCLUSIONS

Thrombocytopenia and neutropenia limited repeat dosing. Although limited clinical activity was detected, the dose-escalation phase was stopped early without establishing an MTD. The study was registered with ClinicalTrials.gov (NCT03106428).

Receptor-recognition and antiviral mechanisms of retrovirus-derived human proteins

Human syncytin-1 and suppressyn are cellular proteins of retroviral origin involved in cell-cell fusion events to establish the maternal-fetal interface in the placenta. In cell culture, they restrict infections from members of the largest interference group of vertebrate retroviruses, and are regarded as host immunity factors expressed during development. At the core of the syncytin-1 and suppressyn functions are poorly understood mechanisms to recognize a common cellular receptor, the membrane transporter ASCT2. Here, we present cryo-electron microscopy structures of human ASCT2 in complexes with the receptor-binding domains of syncytin-1 and suppressyn. Despite their evolutionary divergence, the two placental proteins occupy similar positions in ASCT2, and are stabilized by the formation of a hybrid β-sheet or 'clamp' with the receptor. Structural predictions of the receptor-binding domains of extant retroviruses indicate overlapping binding interfaces and clamping sites with ASCT2, revealing a competition mechanism between the placental proteins and the retroviruses. Our work uncovers a common ASCT2 recognition mechanism by a large group of endogenous and disease-causing retroviruses, and provides high-resolution views on how placental human proteins exert morphological and immunological functions.

Cuscuta chinensis flavonoids alleviate ovarian damage in offspring female mice induced by BPA exposure during pregnancy by regulating the central carbon metabolism pathway

Pregnancy is a sensitive window period for bisphenol A (BPA) exposure. BPA can pass through the placenta and cause reproductive damage in offspring female mice. Even BPA that is not metabolized during lactation can be passed through milk. Cuscuta chinensis flavonoids (CCFs) can alleviate reproductive damage caused by BPA, but the mechanism of action is unclear. To investigate the potential mitigating impact of CCFs on ovarian damage resulting from BPA exposure during pregnancy, we administered BPA and CCFs to pregnant mice during the gestational period spanning from 0.5 to 17.5 days. Aseptic collection of serum and ovaries from female mice was conducted on postnatal day 21 (PND21). Serum hormone levels and tissue receptor levels were quantified utilizing ELISA and PCR, while ovaries underwent sequencing and analysis through transcriptomics and metabolomics techniques. Additionally, the assessment of ovarian oxidative stress levels was carried out as part of the comprehensive analysis. The results showed that CCFs administration mitigated the adverse effects induced by BPA exposure on ovarian index, hormone levels, receptor expression, and mRNA expression levels in female offspring mice. The joint analysis of transcriptome and metabolome revealed 48 enriched pathways in positive ion mode and 44 enriched pathways in negative ion mode. Among them, the central carbon metabolism pathway is significantly regulated by BPA and CCFs. The screened sequencing results were verified through qPCR and biochemical kits. In this study, CCFs may participate in the central carbon metabolism pathway by reducing the expression of Kit proto-oncogene (Kit), hexokinase 1 gene (Hk1) and pyruvate kinase M (Pkm) mRNA and increasing the expression of h-ras proto-oncogene (Hras), sirtuin 3 (Sirt3), sirtuin 6 (Sirt6) and TP53 induced glycolysis regulatory phosphatase gene (Tigar) mRNA, thereby resisting the effects of BPA on the body. At the same time, the metabolic levels of D-Fructose 1,6-bisphosphate and L-Asparagine tend to be stable. Moreover, CCFs demonstrated a capacity to diminish the BPA-induced escalation in reactive oxygen species (ROS) and malondialdehyde (MDA). Simultaneously, it exhibited the ability to elevate levels of glutathione (GSH) and catalase (CAT), thereby effectively preventing peroxidation. In summary, CCFs alleviate BPA-induced ovarian damage in offspring female mice by regulating the central carbon metabolism pathway. This study will improve the information on BPA reproductive damage antagonist drugs and provide a theoretical basis for protecting animal reproductive health.

CircCPA4 induces ASCT2 expression to promote tumor property of non-small cell lung cancer cells in a miR-145-5p-dependent manner

BACKGROUND

Non-small cell lung cancer (NSCLC) is a type of lung cancer that occurs in the cells of the respiratory tract, and its development is influenced by the regulation of circular RNAs (circRNAs). However, the role of circRNA carboxypeptidase A4 (circCPA4) in the progression of NSCLC and the underlying mechanism remain relatively clear.

METHODS

The study utilized both real-time quantitative polymerase chain reaction (RT-qPCR) and western blot techniques to evaluate the levels of circCPA4, microRNA-145-5p (miR-145-5p), alanine, serine, or cysteine-preferring transporter 2 (ASCT2). To assess cell proliferation, cell counting kit-8 (CCK8) and 5-ethynyl-2'-deoxyuridine (EdU) assays were performed. Apoptosis was determined using flow cytometry, while cell migration and invasive capacity were evaluated through transwell and wound-healing assays. Intracellular levels of glutamine, glutamate, and α-KG were measured using specific kits. The relationship between miR-145-5p and circCPA4 or ASCT2 was confirmed using dual-luciferase reporter assay and RNA immunoprecipitation assay.

RESULTS

CircCPA4 and ASCT2 RNA levels were elevated, while miR-145-5p was downregulated in both NSCLC tissues and cells. Depletion of circCPA4 significantly inhibited NSCLC cell proliferation, migration, invasion, and intracellular levels of glutamine, glutamate, and α-KG, and promoted apoptosis. Moreover, circCPA4 knockdown delayed tumor growth in vivo. Furthermore, circCPA4 was found to bind to miR-145-5p, thereby regulating the progression of NSCLC in vitro. ASCT2 was also identified as a downstream target of miR-145-5p, and its upregulation rescued the effects of miR-145-5p overexpression on NSCLC cell processes.

CONCLUSION

CircCPA4 knockdown inhibited tumor property of NSCLC cells by modulating the miR-145-5p/ASCT2 axis.

Exploiting the Achilles' heel of cancer: disrupting glutamine metabolism for effective cancer treatment

Cancer cells have adapted to rapid tumor growth and evade immune attack by reprogramming their metabolic pathways. Glutamine is an important nitrogen resource for synthesizing amino acids and nucleotides and an important carbon source in the tricarboxylic acid (TCA) cycle and lipid biosynthesis pathway. In this review, we summarize the significant role of glutamine metabolism in tumor development and highlight the vulnerabilities of targeting glutamine metabolism for effective therapy. In particular, we review the reported drugs targeting glutaminase and glutamine uptake for efficient cancer treatment. Moreover, we discuss the current clinical test about targeting glutamine metabolism and the prospective direction of drug development.

Cryo-electron microscopy-based drug design

Structure-based drug design (SBDD) has gained popularity owing to its ability to develop more potent drugs compared to conventional drug-discovery methods. The success of SBDD relies heavily on obtaining the three-dimensional structures of drug targets. X-ray crystallography is the primary method used for solving structures and aiding the SBDD workflow; however, it is not suitable for all targets. With the resolution revolution, enabling routine high-resolution reconstruction of structures, cryogenic electron microscopy (cryo-EM) has emerged as a promising alternative and has attracted increasing attention in SBDD. Cryo-EM offers various advantages over X-ray crystallography and can potentially replace X-ray crystallography in SBDD. To fully utilize cryo-EM in drug discovery, understanding the strengths and weaknesses of this technique and noting the key advancements in the field are crucial. This review provides an overview of the general workflow of cryo-EM in SBDD and highlights technical innovations that enable its application in drug design. Furthermore, the most recent achievements in the cryo-EM methodology for drug discovery are discussed, demonstrating the potential of this technique for advancing drug development. By understanding the capabilities and advancements of cryo-EM, researchers can leverage the benefits of designing more effective drugs. This review concludes with a discussion of the future perspectives of cryo-EM-based SBDD, emphasizing the role of this technique in driving innovations in drug discovery and development. The integration of cryo-EM into the drug design process holds great promise for accelerating the discovery of new and improved therapeutic agents to combat various diseases.

Design strategies and recent development of bioactive modulators for glutamine transporters

Glutamine transporters are integral to the metabolism of glutamine in both healthy tissues and cancerous cells, playing a pivotal role in maintaining amino acid balance, synthesizing biomolecules, and regulating redox equilibrium. Their critical functions in cellular metabolism make them promising targets for oncological therapies. Recent years have witnessed substantial progress in the field of glutamine transporters, marked by breakthroughs in understanding of their protein structures and the discovery of novel inhibitors, prodrugs, and radiotracers. This review provides a comprehensive update on the latest advancements in modulators targeting the glutamine transporter, with special attention given to LAT1 and ASCT2. It also discusses innovative approaches in drug design aimed at these transporters.

Exploring Amino Acid Transporters as Therapeutic Targets for Cancer: An Examination of Inhibitor Structures, Selectivity Issues, and Discovery Approaches

Amino acid transporters are abundant amongst the solute carrier family and have an important role in facilitating the transfer of amino acids across cell membranes. Because of their impact on cell nutrient distribution, they also appear to have an important role in the growth and development of cancer. Naturally, this has made amino acid transporters a novel target of interest for the development of new anticancer drugs. Many attempts have been made to develop inhibitors of amino acid transporters to slow down cancer cell growth, and some have even reached clinical trials. The purpose of this review is to help organize the available information on the efforts to discover amino acid transporter inhibitors by focusing on the amino acid transporters ASCT2 (SLC1A5), LAT1 (SLC7A5), xCT (SLC7A11), SNAT1 (SLC38A1), SNAT2 (SLC38A2), and PAT1 (SLC36A1). We discuss the function of the transporters, their implication in cancer, their known inhibitors, issues regarding selective inhibitors, and the efforts and strategies of discovering inhibitors. The goal is to encourage researchers to continue the search and development within the field of cancer treatment research targeting amino acid transporters.

LAMP2A overexpression in colorectal cancer promotes cell growth and glycolysis via chaperone‑mediated autophagy

Lysosome-associated membrane protein type 2A (LAMP2A) is a key protein in the chaperone-mediated autophagy (CMA) pathway and has been demonstrated to be involved in the pathogenesis of a number of tumors. However, the role of CMA in colorectal cancer cell proliferation, metastasis and cell survival during oxidative stress and oxaliplatin resistance remains to be elucidated. In the present study, elevated expression of LAMP2A was observed in colon cancer tissues. Then, CMA activity was increased in SW480 and HT29 colorectal cancer cells with a LAMP2A overexpression vector and CMA activity was decreased using a LAMP2A short interfering RNA vector. MTT and colony formation assays showed that the colorectal cancer cell proliferation ability and cell viability following treatment with H2O2 or oxaliplatin were decreased significantly after LAMP2A knockdown and increased significantly after LAMP2A overexpression. Wound healing assays and Transwell invasion assays demonstrated that downregulation of LAMP2A expression inhibited the cell migration and invasion abilities of colorectal cancer and that upregulation of LAMP2A expression promoted cell migration and invasion. Extracellular acidification rate (ECAR) assay and lactate determination assay showed that glycolysis in colorectal cancer cells was significantly downregulated after LAMP2A knockdown and significantly upregulated after LAMP2A overexpression. Inhibition of glycolysis by 2-DG markedly attenuated LAMP2A-induced chemoresistance in colorectal cancer cells. Collectively, these data indicated that CMA can promote colorectal cancer cell proliferation, metastasis and cell survival during oxidative stress and oxaliplatin resistance and that the mechanism is related to the glycolytic pathway, which may provide a new therapeutic target for colorectal cancer patients.

The Role of Tumor Metabolic Reprogramming in Tumor Immunity

The occurrence and development of tumors require the metabolic reprogramming of cancer cells, namely the alteration of flux in an autonomous manner via various metabolic pathways to meet increased bioenergetic and biosynthetic demands. Tumor cells consume large quantities of nutrients and produce related metabolites via their metabolism; this leads to the remodeling of the tumor microenvironment (TME) to better support tumor growth. During TME remodeling, the immune cell metabolism and antitumor immune activity are affected. This further leads to the escape of tumor cells from immune surveillance and therefore to abnormal proliferation. This review summarizes the regulatory functions associated with the abnormal biosynthesis and activity of metabolic signaling molecules during the process of tumor metabolic reprogramming. In addition, we provide a comprehensive description of the competition between immune cells and tumor cells for nutrients in the TME, as well as the metabolites required for tumor metabolism, the metabolic signaling pathways involved, and the functionality of the immune cells. Finally, we summarize current research targeted at the development of tumor immunotherapy. We aim to provide new concepts for future investigations of the mechanisms underlying the metabolic reprogramming of tumors and explore the association of these mechanisms with tumor immunity.

A Novel ASCT2 Inhibitor, C118P, Blocks Glutamine Transport and Exhibits Antitumour Efficacy in Breast Cancer

BACKGROUND

The microtubule protein inhibitor C118P shows excellent anti-breast cancer effects. However, the potential targets and mechanisms of C118P in breast cancer remain unknown.

METHODS

Real-time cellular analysis (RTCA) was used to detect cell viability. Apoptosis and the cell cycle were detected by flow cytometry. Computer docking simulations, surface plasmon resonance (SPR) technology, and microscale thermophoresis (MST) were conducted to study the interaction between C118P and alanine-serine-cysteine transporter 2 (ASCT2). Seahorse XF technology was used to measure the basal oxygen consumption rate (OCR). The effect of C118P in the adipose microenvironment was explored using a co-culture model of adipocytes and breast cancer cells and mouse cytokine chip.

RESULTS

C118P inhibited proliferation, potentiated apoptosis, and induced G2/M cell cycle arrest in breast cancer cells. Notably, ASCT2 was validated as a C118P target through reverse docking, SPR, and MST. C118P suppressed glutamine metabolism and mediated autophagy via ASCT2. Similar results were obtained in the adipocyte-breast cancer microenvironment. Adipose-derived interleukin-6 (IL-6) promoted the proliferation of breast cancer cells by enhancing glutamine metabolism via ASCT2. C118P inhibited the upregulation of ASCT2 by inhibiting the effect of IL-6 in co-cultures.

CONCLUSION

C118P exerts an antitumour effect against breast cancer via the glutamine transporter ASCT2.

A Carbonic Anhydrase IX/SLC1A5 Axis Regulates Glutamine Metabolism Dependent Ferroptosis in Hypoxic Tumor Cells

The ability of tumor cells to alter their metabolism to support survival and growth presents a challenge to effectively treat cancers. Carbonic anhydrase IX (CAIX) is a hypoxia-induced, metabolic enzyme that plays a crucial role in pH regulation in tumor cells. Recently, through a synthetic lethal screen, we identified CAIX to play an important role in redox homeostasis. In this study, we show that CAIX interacts with the glutamine (Gln) transporter, solute carrier family 1 member 5 (SLC1A5), and coordinately functions to maintain redox homeostasis through the glutathione/glutathione peroxidase 4 (GSH/GPX4) axis. Inhibition of CAIX increases Gln uptake by SLC1A5 and concomitantly increases GSH levels. The combined inhibition of CAIX activity and Gln metabolism or the GSH/GPX4 axis results in an increase in lipid peroxidation and induces ferroptosis, both in vitro and in vivo. Thus, this study demonstrates cotargeting of CAIX and Gln metabolism as a potential strategy to induce ferroptosis in tumor cells.

Targeting Pulmonary Fibrosis by SLC1A5-Dependent Glutamine Transport Blockade

The neutral amino acid glutamine plays a central role in TGF-β (transforming growth factor-β)-induced myofibroblast activation and differentiation. Cells take up glutamine mainly through a transporter expressed on the cell surface known as solute carrier SLC1A5 (solute carrier transporter 1A5). In the present work, we demonstrated that profibrotic actions of TGF-β are mediated, at least in part, through a metabolic maladaptation of SLC1A5 and that targeting SLC1A5 abrogates multiple facets of fibroblast activation. This approach could thus represent a novel therapeutic strategy to treat patients with fibroproliferative diseases. We found that SLC1A5 was highly expressed in fibrotic lung fibroblasts and fibroblasts isolated from idiopathic pulmonary fibrosis lungs. The expression of profibrotic targets, cell migration, and anchorage-independent growth by TGF-β required the activity of SLC1A5. Loss or inhibition of SLC1A5 function enhanced fibroblast susceptibility to autophagy; suppressed mTOR, HIF (hypoxia-inducible factor), and Myc signaling; and impaired mitochondrial function, ATP production, and glycolysis. Pharmacological inhibition of SLC1A5 by the small-molecule inhibitor V-9302 shifted fibroblast transcriptional profiles from profibrotic to fibrosis resolving and attenuated fibrosis in a bleomycin-treated mouse model of lung fibrosis. This is the first study, to our knowledge, to demonstrate the utility of a pharmacological inhibitor of glutamine transport in fibrosis, providing a framework for new paradigm-shifting therapies targeting cellular metabolism for this devastating disease.

The role and mechanism of action of microRNA-122 in cancer: Focusing on the liver

microRNA-122 (miR-122) is a highly conserved microRNA that is predominantly expressed in the liver and plays a critical role in the regulation of liver metabolism. Recent studies have shown that miR-122 is involved in the pathogenesis of various types of cancer, particularly liver cancer. In this sense, The current findings highlighted the potential role of miR-122 in regulating many vital processes in cancer pathophysiology, including apoptosis, signaling pathway, cell metabolism, immune system response, migration, and invasion. These results imply that miR-122, which has been extensively studied for its biological functions and potential therapeutic applications, acts as a tumor suppressor or oncogene in cancer development. We first provide an overview and summary of the physiological function and mode of action of miR-122 in liver cancer. We will examine the various signaling pathways and molecular mechanisms through which miR-122 exerts its effects on cancer cells, including the regulation of oncogenic and tumor suppressor genes, the modulation of cell proliferation and apoptosis, and the regulation of metastasis. Most importantly, we will also discuss the potential diagnostic and therapeutic applications of miR-122 in cancer, including the development of miRNA-based biomarkers for cancer diagnosis and prognosis, and the potential use of miR-122 as a therapeutic target for cancer treatment.

ASCT2-mediated glutamine uptake promotes Th1 differentiation via ROS-EGR1-PAC1 pathway in oral lichen planus

Oral lichen planus (OLP) is a T cell-mediated autoimmune disease of oral mucosa concerning with the redox imbalance. Although glutamine uptake mediated by alanine-serine-cysteine transporter 2 (ASCT2) is critical to T cell differentiation, the exact mechanism remains ambiguous. Here, we elucidate a novel regulatory mechanism of ASCT2-mediated uptake in the differentiation and proliferation of T cells through maintaining redox balance in OLP. The results of immunohistochemistry (IHC) showed that both ASCT2 and glutaminase (GLS) were obviously upregulated compared to controls in OLP. Moreover, correlation analyses indicated that ASCT2 expression was significantly related to GLS level. Interestingly, the upregulation of glutamine metabolism in epithelial layer was consistent with that in lamina propria. Functional assays in vitro revealed the positive association between glutamine metabolism and lymphocytes infiltration. Additionally, multiplex immunohistochemistry (mIHC) uncovered a stronger colocalization among ASCT2 and CD4 and IFN-γ, which was further demonstrated by human Th1 differentiation assay in vitro. Mechanistically, targeting glutamine uptake through interference with ASCT2 using L-γ-Glutamyl-p-nitroanilide (GPNA) decreased the glutamine uptake of T cells and leaded to the accumulation of intracellular reactive oxygen species (ROS), which promoted dual specificity phosphatase 2 (DUSP2/PAC1) expression through activation of early growth response 1 (EGR1) to induce dephosphorylation of signal transducer and activator of transcription 3 (STAT3) and inhibit Th1 differentiation in turn. These results demonstrated that glutamine uptake mediated by ASCT2 induced Th1 differentiation by ROS-EGR1-PAC1 pathway, and restoring the redox dynamic balance through targeting ASCT2 may be a potential treatment for T cell-mediated autoimmune diseases.

Monocarboxylate Transporter-1 (MCT1)-Mediated Lactate Uptake Protects Pancreatic Adenocarcinoma Cells from Oxidative Stress during Glutamine Scarcity Thereby Promoting Resistance against Inhibitors of Glutamine Metabolism

Metabolic compartmentalization of stroma-rich tumors, like pancreatic ductal adenocarcinoma (PDAC), greatly contributes to malignancy. This involves cancer cells importing lactate from the microenvironment (reverse Warburg cells) through monocarboxylate transporter-1 (MCT1) along with substantial phenotype alterations. Here, we report that the reverse Warburg phenotype of PDAC cells compensated for the shortage of glutamine as an essential metabolite for redox homeostasis. Thus, oxidative stress caused by glutamine depletion led to an Nrf2-dependent induction of MCT1 expression in pancreatic T3M4 and A818-6 cells. Moreover, greater MCT1 expression was detected in glutamine-scarce regions within tumor tissues from PDAC patients. MCT1-driven lactate uptake supported the neutralization of reactive oxygen species excessively produced under glutamine shortage and the resulting drop in glutathione levels that were restored by the imported lactate. Consequently, PDAC cells showed greater survival and growth under glutamine depletion when utilizing lactate through MCT1. Likewise, the glutamine uptake inhibitor V9302 and glutaminase-1 inhibitor CB839 induced oxidative stress in PDAC cells, along with cell death and cell cycle arrest that were again compensated by MCT1 upregulation and forced lactate uptake. Our findings show a novel mechanism by which PDAC cells adapt their metabolism to glutamine scarcity and by which they develop resistance against anticancer treatments based on glutamine uptake/metabolism inhibition.

Engineering extracellular vesicles to deliver CRISPR ribonucleoprotein for gene editing

Clustered regularly interspaced palindromic repeats (CRISPR) is a gene editing tool with tremendous therapeutic potential. Recently, ribonucleoprotein (RNP) complex-based CRISPR systems have gained momentum due to their reduction of off-target editing. This has coincided with the emergence of extracellular vesicles (EVs) as a therapeutic delivery vehicle due to its low immunogenicity and high capacity for manipulation. EVs are cell-derived membranous nanoparticles which mediate the intercellular transfer of molecular components. Current technologies achieve CRISPR RNP encapsulation into EVs through EVs biogenesis, thereby avoiding unnecessary physical, chemical or biological manipulations to the vesicles directly. Herein, we identify sixteen EVs-based CRISPR RNP encapsulation strategies, each with distinct genetic features to encapsulate CRISPR RNP. According to the molecular mechanism facilitating the encapsulation process, there are six strategies of encapsulating Cas9 RNP into virus-like particles based on genetic fusion, seven into EVs based on protein tethering, and three based on sgRNA-coupled encapsulation. Additionally, the incorporation of a targeting moiety to the EVs membrane surface through EVs biogenesis confers tropism and increases delivery efficiency to specific cell types. The targeting moieties include viral envelope proteins, recombinant proteins containing a ligand peptide, single-chain fragment variable (scFv) antibodies, and integrins. However, current strategies still have a number of limitations which prevent their use in clinical trials. Among those, the incorporation of viral proteins for encapsulation of Cas9 RNP have raised issues of biocompatibility due to host immune response. Future studies should focus on genetically engineering the EVs without viral proteins, enhancing EVs delivery specificity, and promoting EVs-based homology directed repair. Nevertheless, the integration of CRISPR RNP encapsulation and tropism technologies will provide strategies for the EVs-based delivery of CRISPR RNP in gene therapy and disease treatment.

c-Myc protects hepatocellular carcinoma cell from ferroptosis induced by glutamine deprivation via upregulating GOT1 and Nrf2

BACKGROUND

Glutamine metabolism is critical for development of hepatocellular carcinoma (HCC), which makes it a novel promising treatment target. However, clinical evidence suggested glutamine withdrawal therapy does not achieved the desired tumor suppression. Therefore, it is valuable to investigate the survival mechanisms of tumors with glutamine deprivation.

METHODS

The HCC cells were cultured in glutamine-free medium or supplemented with glutamine metabolites or ferroptosis inhibitors. The parameters related to ferroptosis and the activity of GSH synthesis-related enzymes of the HCC cells were detected by corresponding kits. The expressions of glutamate oxaloacetate transaminase 1 (GOT1), c-Myc and Nrf2 were detected by western blot and qRT-PCR. The chromatin immunoprecipitation and luciferase reporter assays were performed to investigate the correlation between c-Myc and GOT1. The siRNAs of c-Myc and GOT1 were used to explore their roles in GSH (GSH) synthesis and ferroptosis in vitro and in vivo.

RESULTS

Glutamine deprivation-induced ferroptosis did not completely inhibit HCC cells proliferation. Glutamine deprivation activated the expression of c-Myc, which promoted the transcription of GOT1 and Nrf2, consequently maintaining the GSH synthesis and inhibiting ferroptosis. In addition, combined inhibition of GOT1 with glutamine deprivation could result in better inhibition of HCC in vitro and in vivo.

CONCLUSIONS

In our work, the results indicate that GOT1 induced by c-Myc may play an important role in combating ferroptosis due to glutamine deprivation, making it a significant target in glutamine withdrawal therapy. This study provides a theoretical foundation for the clinical targeted therapy for HCC.

The SLC38A5/SNAT5 amino acid transporter: from pathophysiology to pro-cancer roles in the tumor microenvironment

SLC38A5/SNAT5 is a system N transporter that can mediate net inward or outward transmembrane fluxes of neutral amino acids coupled with Na+ (symport) and H+ (antiport). Its preferential substrates are not only amino acids with side chains containing amide (glutamine and asparagine) or imidazole (histidine) groups, but also serine, glycine, and alanine are transported by the carrier. Expressed in the pancreas, intestinal tract, brain, liver, bone marrow, and placenta, it is regulated at mRNA and protein levels by mTORC1 and WNT/β-catenin pathways, and it is sensitive to pH, nutritional stress, inflammation, and hypoxia. SNAT5 expression has been found to be altered in pathological conditions such as chronic inflammatory diseases, gestational complications, chronic metabolic acidosis, and malnutrition. Growing experimental evidence shows that SNAT5 is overexpressed in several types of cancer cells. Moreover, recently published results indicate that SNAT5 expression in stromal cells can support the metabolic exchanges occurring in the tumor microenvironment of asparagine-auxotroph tumors. We review the functional role of the SNAT5 transporter in pathophysiology and propose that, due to its peculiar operational and regulatory features, SNAT5 may play important pro-cancer roles when expressed either in neoplastic or in stromal cells of glutamine-auxotroph tumors.NEW & NOTEWORTHY The transporter SLC38A5/SNAT5 provides net influx or efflux of glutamine, asparagine, and serine. These amino acids are of particular metabolic relevance in several conditions. Changes in transporter expression or activity have been described in selected types of human cancers, where SNAT5 can mediate amino acid exchanges between tumor and stromal cells, thus providing a potential therapeutic target. This is the first review that recapitulates the characteristics and roles of the transporter in physiology and pathology.

Monitoring and modelling the glutamine metabolic pathway: a review and future perspectives

BACKGROUND

Analysis of the glutamine metabolic pathway has taken a special place in metabolomics research in recent years, given its important role in cell biosynthesis and bioenergetics across several disorders, especially in cancer cell survival. The science of metabolomics addresses the intricate intracellular metabolic network by exploring and understanding how cells function and respond to external or internal perturbations to identify potential therapeutic targets. However, despite recent advances in metabolomics, monitoring the kinetics of a metabolic pathway in a living cell in situ, real-time and holistically remains a significant challenge.

AIM

This review paper explores the range of analytical approaches for monitoring metabolic pathways, as well as physicochemical modeling techniques, with a focus on glutamine metabolism. We discuss the advantages and disadvantages of each method and explore the potential of label-free Raman microspectroscopy, in conjunction with kinetic modeling, to enable real-time and in situ monitoring of the cellular kinetics of the glutamine metabolic pathway.

KEY SCIENTIFIC CONCEPTS

Given its important role in cell metabolism, the ability to monitor and model the glutamine metabolic pathways are highlighted. Novel, label free approaches have the potential to revolutionise metabolic biosensing, laying the foundation for a new paradigm in metabolomics research and addressing the challenges in monitoring metabolic pathways in living cells.

CAFs targeted ultrasound-responsive nanodroplets loaded V9302 and GLULsiRNA to inhibit melanoma growth via glutamine metabolic reprogramming and tumor microenvironment remodeling

Despite rapid advances in metabolic therapies over the past decade, their efficacy in melanoma has been modest, largely due to the interaction between cancer-associated fibroblasts (CAFs) and cancer cells to promote cancer growth. Altering the tumor microenvironment (TME) is challenging and elusive. CAFs is critical for glutamine deprivation survival in melanoma. In this research, we assembled a CAFs-targeted, controlled-release nanodroplets for the combined delivery of the amino acid transporter ASCT2 (SLC1A5) inhibitor V9302 and GLULsiRNA (siGLUL). The application of ultrasound-targeted microbubble disruption (UTMD) allows for rapid release of V9302 and siGLUL, jointly breaking the glutamine metabolism interaction between CAFs and cancer cells on one hand, on the other hand, blocking activated CAFs and reducing the expression of extracellular matrix (ECM) to facilitate drug penetration. In addition, ultrasound stimulation made siGLUL more accessible to tumor cells and CAFs, downregulating GLUL expression in both cell types. FH-V9302-siGLUL-NDs also serve as contrast-enhanced ultrasound imaging agents for tumor imaging. Our study developed and reported FH-NDs as nanocarriers for V9302 and siGLUL, demonstrating that FH-V9302-siGLUL-NDs have potential bright future applications for integrated diagnostic therapy. Graphical Abstract.

Preclinical radiolabeling, in vivo biodistribution and positron emission tomography of a novel pyrrolobenzodiazepine (PBD)-based antibody drug conjugate targeting ASCT2

INTRODUCTION

Anti-ASCT2 antibody drug conjugate (ADC) MEDI7247 has been under development as a potential anti-cancer therapy for patients with selected relapsed/refractory hematological malignancies and advanced solid tumors by MedImmune. Although promising efficacy was observed in the clinic, pharmacokinetic (PK) analyses observed low exposure of MEDI7247 in phase I hematological patients. To investigate the biodistribution properties of MEDI7247, MEDI7247 and control antibodies were radiolabeled with zirconium-89 and in vitro and in vivo properties characterized.

METHODS

MEDI7247 (human anti-ASCT2 antibody conjugated with pyrrolobenzodiazepine (PBD)) and MEDI7519 (MEDI7247 without PBD drug conjugate) and an isotype control antibody drug conjugate construct were conjugated with p-isothiocyanatobenzyl-deferoxamine (Df) and radiolabeled with zirconium-89. In vitro studies included determining the radiochemical purity, protein integrity, immunoreactivity (Lindmo analysis), apparent antigen binding affinity for ASCT2-positive cells by Scatchard analysis and serum stability of the radiolabeled immunoconjugates. In vivo studies included biodistribution and PET/MRI imaging studies of the radiolabeled immunoconjugates in an ASCT2-positive tumor model, HT-29 colorectal carcinoma xenografts.

RESULTS

Conditions for the Df-conjugation and radiolabeling of antibody constructs were determined to produce active radioimmunoconjugates. In vivo biodistribution and whole body PET/MRI imaging studies of [89Zr]Zr-Df-MEDI7519 and [89Zr]Zr-Df-MEDI7247 radioimmunoconjugates in HT-29 colon carcinoma xenografts in BALB/c nude mice demonstrated specific tumor localization. However, more rapid blood clearance and non-specific localization in liver was observed for [89Zr]Zr-Df-MEDI7247 and [89Zr]Zr-Df-MEDI7519 compared to isotype control ADC. Except for liver and bone, other normal tissues demonstrated clearance reflecting the blood clearance for all three constructs and no other abnormal tissue uptake.

CONCLUSIONS AND ADVANCES IN KNOWLEDGE

Preclinical biodistribution analyses of [89Zr]Zr-Df-MEDI7247 and [89Zr]Zr-Df-MEDI7519 showed the biodistribution pattern of anti-ASCT2 ADC MEDI7247 was similar to parental MEDI7519, and both antibodies showed specific tumor uptake compared to an isotype control ADC. This study highlights an important role nuclear medicine imaging techniques can play in early preclinical assessment of drug specificity as part of the drug development pipeline.

SLC1A5 regulates cell proliferation and self-renewal through β-catenin pathway mediated by redox signaling in arsenic-treated uroepithelial cells

Arsenic exposure increases the risk of bladder cancer in humans, but its underlying mechanisms remain elusive. The alanine, serine, cysteine-preferring transporter 2 (ASCT2, SLC1A5) is frequently overexpressed in cancer cells. The aim of this study was to evaluate the effects of arsenic on SLC1A5, and to determine the role of SLC1A5 in the proliferation and self-renewal of uroepithelial cells. F344 rats were exposed to 87 mg/L NaAsO₂ or 200 mg/L DMA^V for 12 weeks. The SV-40 immortalized human uroepithelial (SV-HUC-1) cells were cultured in medium containing 0.5 μM NaAsO₂ for 40 weeks. Arsenic increased the expression levels of SLC1A5 and β-catenin both in vivo and in vitro. SLC1A5 promoted cell proliferation and self-renewal by activating β-catenin, which in turn was dependent on maintaining GSH/ROS homeostasis. Our results suggest that SLC1A5 is a potential therapeutic target for arsenic-induced proliferation and self-renewal of uroepithelial cells.

Targeting Glutamine Metabolism as an Attractive Therapeutic Strategy for Acute Myeloid Leukemia

OPINION STATEMENT

Relapse after chemotherapy and hematopoietic stem cell transplantation leads to adverse prognosis for acute myeloid leukemia (AML) patients. As a "conditionally essential amino acid," glutamine contributes to the growth and proliferation of AML cells. Glutamine-target strategies as new treatment approaches have been widely explored in AML treatment to improve outcome. Glutamine-target strategies including depletion of systemic glutamine and application of glutamine uptake inhibitors, glutamine antagonists/analogues, and glutaminase inhibitors. Because glutamine metabolism involved in multiple pathways in cells and each pathway of glutamine metabolism has many regulatory factors, therefore, AML therapy targeting glutamine metabolism should focus on how to inhibit multiple metabolic pathways without affecting normal cells and host immune to achieve effective treatment for AML.

Fine-tuning osteoclastogenesis: An insight into the cellular and molecular regulation of osteoclastogenesis

Osteoclasts, the bone-resorbing cells, are essential for the bone remodeling process and are involved in the pathophysiology of several bone-related diseases. The extensive corpus of in vitro research and crucial mouse model studies in the 1990s demonstrated the key roles of monocyte/macrophage colony-stimulating factor, receptor activator of nuclear factor kappa B ligand (RANKL) and integrin αvβ3 in osteoclast biology. Our knowledge of the molecular mechanisms by which these variables control osteoclast differentiation and function has significantly advanced in the first decade of this century. Recent developments have revealed a number of novel insights into the fundamental mechanisms governing the differentiation and functional activity of osteoclasts; however, these mechanisms have not yet been adequately documented. Thus, in the present review, we discuss various regulatory factors including local and hormonal factors, innate as well as adaptive immune cells, noncoding RNAs (ncRNAs), etc., in the molecular regulation of the intricate and tightly regulated process of osteoclastogenesis. ncRNAs have a critical role as epigenetic controllers of osteoclast physiologic activities, including differentiation and bone resorption. The primary ncRNAs, which include micro-RNAs, circular RNAs, and long noncoding RNAs, form a complex network that affects gene transcription activities associated with osteoclast biological activity. Greater knowledge of the involvement of ncRNAs in osteoclast biological activities will contribute to the treatment and management of several skeletal diseases such as osteoporosis, osteoarthritis, rheumatoid arthritis, etc. Moreover, we further outline potential therapies targeting these regulatory pathways of osteoclastogenesis in distinct bone pathologies.

lncRNA SYTL5-OT4 promotes vessel co-option by inhibiting the autophagic degradation of ASCT2

AIMS

Vessel co-option is responsible for tumor resistance to antiangiogenic therapies (AATs) in patients with colorectal cancer liver metastasis (CRCLM). However, the mechanisms underlying vessel co-option remain largely unknown. Herein, we investigated the roles of a novel lncRNA SYTL5-OT4 and Alanine-Serine-Cysteine Transporter 2 (ASCT2) in vessel co-option-mediated AAT resistance.

METHODS

SYTL5-OT4 was identified by RNA-sequencing and verified by RT-qPCR and RNA fluorescence in situ hybridization assays. The effects of SYTL5-OT4 and ASCT2 on tumor cells were investigated by gain- and loss-of-function experiments, and those of SYTL5-OT4 on ASCT2 expression were analyzed by RNA immunoprecipitation and co-immunoprecipitation assays. The roles of SYTL5-OT4 and ASCT2 in vessel co-option were detected by histological, immunohistochemical, and immunofluorescence analyses.

RESULTS

The expression of SYTL5-OT4 and ASCT2 was higher in patients with AAT-resistant CRCLM. SYTL5-OT4 enhanced the expression of ASCT2 by inhibiting its autophagic degradation. SYTL5-OT4 and ASCT2 promoted vessel co-option by increasing the proliferation and epithelial-mesenchymal transition of tumor cells. Combination therapy of ASCT2 inhibitor and antiangiogenic agents overcame vessel co-option-mediated AAT resistance in CRCLM.

CONCLUSION

This study highlights the crucial roles of lncRNA and glutamine metabolism in vessel co-option and provides a potential therapeutic strategy for patients with AAT-resistant CRCLM.

In vitro evaluation of (S)-2-amino-3-[3-(2-18F-fluoroethoxy)-4-iodophenyl]-2-methylpropanoic acid (18F-FIMP) as a positron emission tomography probe for imaging amino acid transporters

BACKGROUND

(S)-2-amino-3-[3-(2-¹⁸F-fluoroethoxy)-4-iodophenyl]-2-methylpropanoic acid (¹⁸F-FIMP) as a promising PET probe for imaging the tumor-specific L-type amino acid transporter (LAT) 1. Our previous study revealed that ¹⁸F-FIMP had a higher affinity for LAT1 than for LAT2 abundantly expressed even in normal cells. ¹⁸F-FIMP showed high accumulation in LAT1-positive tumor tissues and low accumulation in inflamed lesions in tumor-bearing mice. However, the affinity of ¹⁸F-FIMP for other amino acid transporters was not determined yet. Here, we aimed to determine whether ¹⁸F-FIMP has affinity for other tumor-related amino acid transporters, such as sodium- and chloride-dependent neutral and basic amino acid transporter B(0 +) (ATB^0,+), alanine serine cysteine transporter 2 (ASCT2), and cystine/glutamate transporter (xCT).

PROCEDURES

Cells overexpressing LAT1, ATB^0,+, ASCT2, or xCT were established by the transfection of expression vectors for LAT1, ATB^0,+, ASCT2, or xCT. Protein expression levels were determined by western blot and immunofluorescent analyses. Transport function was evaluated by a cell-based uptake assay using ¹⁸F-FIMP and ¹⁴C-labeled amino acids as substrates.

RESULTS

Intense signals were observed only for expression vector-transfected cells on western blot and immunofluorescent analyses. These signals were strongly reduced by gene-specific small interfering ribonucleic acid treatment. The uptake values for each ¹⁴C-labeled substrate were significantly higher in the transfected cells than in the mock-transfected cells and were significantly inhibited by the corresponding specific inhibitors. The ¹⁸F-FIMP uptake values were significantly higher in the LAT1- and ATB^0,+-overexpressing cells than in the corresponding mock cells, but no such increase was seen in the ASCT2- or xCT-overexpressing cells. These ¹⁸F-FIMP uptake values were significantly decreased by the specific inhibitors for LAT1- and ATB^0,+.

CONCLUSIONS

We demonstrated that ¹⁸F-FIMP has affinity not only for LAT1, but also for ATB^0,+. Our results may be helpful for understanding the mechanisms of the whole-body distribution and tumor accumulation of ¹⁸F-FIMP.

The Ubiquitin-Proteasome System in Tumor Metabolism

Metabolic reprogramming, which is considered a hallmark of cancer, can maintain the homeostasis of the tumor environment and promote the proliferation, survival, and metastasis of cancer cells. For instance, increased glucose uptake and high glucose consumption, known as the "Warburg effect," play an essential part in tumor metabolic reprogramming. In addition, fatty acids are harnessed to satisfy the increased requirement for the phospholipid components of biological membranes and energy. Moreover, the anabolism/catabolism of amino acids, such as glutamine, cystine, and serine, provides nitrogen donors for biosynthesis processes, development of the tumor inflammatory environment, and signal transduction. The ubiquitin-proteasome system (UPS) has been widely reported to be involved in various cellular biological activities. A potential role of UPS in the metabolic regulation of tumor cells has also been reported, but the specific regulatory mechanism has not been elucidated. Here, we review the role of ubiquitination and deubiquitination modification on major metabolic enzymes and important signaling pathways in tumor metabolism to inspire new strategies for the clinical treatment of cancer.

The Synthesis and Biological Applications of the 1,2,3-Dithiazole Scaffold

The 1,2,3-dithiazole is an underappreciated scaffold in medicinal chemistry despite possessing a wide variety of nascent pharmacological activities. The scaffold has a potential wealth of opportunities within these activities and further afield. The 1,2,3-dithiazole scaffold has already been reported as an antifungal, herbicide, antibacterial, anticancer agent, antiviral, antifibrotic, and is a melanin and Arabidopsis gibberellin 2-oxidase inhibitor. These structure activity relationships are discussed in detail, along with insights and future directions. The review also highlights selected synthetic strategies developed towards the 1,2,3-dithiazole scaffold, how these are integrated to accessibility of chemical space, and to the prism of current and future biological activities.

SLC1A5, unrelated to prognosis, was associated with CD8+ T-cell exclusion in the tumor microenvironment of squamous cell carcinoma

SLC1A5, short for solute carrier family 1 member 5, is a neutral amino acid transporter whose expression has been reported to be upregulated in various cancers, including esophageal squamous cell carcinoma (ESCC). Despite this, little has been described regarding the immunological involvement of SLC1A5 expression in the tumor microenvironment of ESCC. Given this, we adopted in silico analyses together with a wet lab strategy to investigate the prognostic and clinicopathological meaning of SLC1A5 expression in ESCC. In silico analyses of SLC1A5 expression data available from The Cancer Genome Atlas (TCGA) database revealed that SLC1A5 expression was unrelated to the prognosis of ESCC, which holds true when extended to other types of squamous cell carcinoma (SCC), including head and neck squamous cell carcinoma (HNSC) and lung squamous cell carcinoma (LUSC). Further analyses revealed that SLC1A5 expression correlated markedly with the infiltration density of effector CD8⁺ T cells in ESCC, and the same was true for HNSC and LUSC when extrapolated. As experimental confirmation, multiplexed immunofluorescent staining was undertaken to verify the correlation between SLC1A5 expression and infiltration of CD8⁺ T cells in a tissue microarray prepared from ESCC and matched normal control tissues. Our data confirmed that SLC1A5 expression was not associated with prognosis but was associated with the exclusion of CD8⁺ T cells. Taken together, all the data we curated strongly support the notion that SLC1A5 expression is associated with CD8⁺ T-cell exclusion in the tumor microenvironment of SCC.

Metabolic reprogramming of glutamine involved in tumorigenesis, multidrug resistance and tumor immunity

Glutamine, as the most abundant amino acid in the body, participates in the biological synthesis of nucleotides and other non-essential amino acids in the process of cell metabolism. Recent studies showed that glutamine metabolic reprogramming is an important signal during cancer development and progression. This metabolic signature in cancer cells can promote the development of cancer by activating multiple signaling pathways and oncogenes. It can also be involved in tumor immune regulation and promote the development of drug resistance to tumors. In this review, we mainly summarize the role of glutamine metabolic reprogramming in tumors, including the regulation of multiple signaling pathways. We further discussed the promising tumor treatment strategy by targeting glutamine metabolism alone or in combination with chemotherapeutics.

Gallic acid markedly stimulates GLUT1-mediated glucose uptake by the AsPC-1 pancreatic cancer cell line

Phenolic acids are recognized as chemopreventive and chemotherapeutic agents. Altered glucose and glutamine metabolism are recognized hallmarks of cancer cells. We aimed to test the influence of phenolic acids on glucose and glutamine cellular uptake by a breast (MCF-7) and a pancreatic (AsPC-1) cancer cell line. Several phenolic acids (caffeic, ferrulic, proctocatechuic, coumaric and gallic acid) affected ³H-glutamine and/or ³H-deoxy-d-glucose (³H-DG) uptake. Gallic acid (100 µM) caused a 3-fold increase in ³H-DG uptake by AsPC-1 cells, associated with a 3.7-fold increase in lactic acid production. Gallic acid stimulated GLUT1-mediated ³H-DG uptake and increased the affinity of this transporter for ³H-DG. We further verified that gallic acid does not change GLUT1 transcription rates and cellular redox state and that its effect does not involve PI3K, mTOR and MAP kinases and is not associated with a proproliferative effect. Gallic acid also increased ³H-DG uptake by MCF-7 cells, although less potently. Further investigation is necessary to elucidate the cellular pathways involved in this effect of gallic acid.

Impeding the combination of astrocytic ASCT2 and NLRP3 by talniflumate alleviates neuroinflammation in experimental models of Parkinson's disease

Alanine-serine-cysteine transporter 2 (ASCT2) is reported to participate in the progression of tumors and metabolic diseases. It is also considered to play a crucial role in the glutamate-glutamine shuttle of neuroglial network. However, it remains unclear the involvement of ASCT2 in neurological diseases such as Parkinson's disease (PD). In this study, we demonstrated that high expression of ASCT2 in the plasma samples of PD patients and the midbrain of MPTP mouse models is positively correlated with dyskinesia. We further illustrated that ASCT2 expressed in astrocytes rather than neurons significantly upregulated in response to either MPP⁺ or LPS/ATP challenge. Genetic ablation of astrocytic ASCT2 alleviated the neuroinflammation and rescued dopaminergic (DA) neuron damage in PD models in vitro and in vivo. Notably, the binding of ASCT2 to NLRP3 aggravates astrocytic inflammasome-triggered neuroinflammation. Then a panel of 2513 FDA-approved drugs were performed via virtual molecular screening based on the target ASCT2 and we succeed in getting the drug talniflumate. It is validated talniflumate impedes astrocytic inflammation and prevents degeneration of DA neurons in PD models. Collectively, these findings reveal the role of astrocytic ASCT2 in the pathogenesis of PD, broaden the therapeutic strategy and provide a promising candidate drug for PD treatment.

Circular RNA circ-AGFG1 contributes to esophageal squamous cell carcinoma progression and glutamine catabolism by targeting microRNA-497-5p/solute carrier family 1 member 5 axis

Circular RNAs (circRNAs) have been shown to play important regulatory roles in human malignancies. However, the role of circRNA ArfGAP with FG repeats 1 (circ-AGFG1) in esophageal squamous cell carcinoma (ESCC) progression and its associated mechanism are still largely undefined. Cell proliferation was analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and 5-ethynyl-2'-deoxyuridine assay. Cell apoptosis was assessed by flow cytometry analysis. Transwell assay and wound healing assay were used to analyze cell invasion and migration abilities. The uptake of glutamine and the production of α-ketoglutarate and glutamate were analyzed using Glutamine Determination Kit, α-ketoglutarate Assay Kit and Glutamate Determination Kit. A xenograft tumor model was used to analyze the biological role of circ-AGFG1 in vivo . The interaction between microRNA-497-5p (miR-497-5p) and circ-AGFG1 or solute carrier family 1 member 5 (SLC1A5) was verified by dual-luciferase reporter assay. Circ-AGFG1 expression was upregulated in ESCC tissues and cell lines. Circ-AGFG1 silencing suppressed the proliferation, migration, invasion and glutaminolysis and triggered the apoptosis of ESCC cells. Circ-AGFG1 knockdown significantly slowed down tumor growth in vivo . Circ-AGFG1 acted as a sponge for miR-497-5p, and miR-497-5p interacted with the 3' untranslated region (3'UTR) of SLC1A5. miR-497-5p silencing largely abolished circ-AGFG1 silencing-induced effects in ESCC cells. miR-497-5p overexpression-mediated influences in ESCC cells were largely reversed by the addition of SLC1A5 expressing plasmid. Circ-AGFG1 could upregulate SLC1A5 expression by sponging miR-497-5p. In summary, circ-AGFG1 acted as an oncogene to elevate the malignant potential and promote the glutamine catabolism of ESCC cells by targeting the miR-497-5p/SLC1A5 axis.

Transporter-Mediated Drug Delivery

Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters.

SLC1A5 enhances malignant phenotypes through modulating ferroptosis status and immune microenvironment in glioma

Glioma is the most common type of primary malignant tumor in the central nervous system with limited treatment satisfaction. Finding new therapeutic targets has remained a major challenge. Ferroptosis is a novel and distinct type of programmed cell death, playing a regulatory role in the progression of tumors. However, the role of ferroptosis or ferroptosis-related genes (FRGs) in glioma progression has not been extensively studied. In our study, a novel ferroptosis-related prognostic model, including 7 genes, was established, in which patients classified into the high-risk group had more immuno-suppressive status and worse prognosis. Among these 7 genes, we screened solute carrier family 1 member 5 (SLC1A5), an FRG, as a possible new target for glioma treatment. Our results showed that the expression of SLC1A5 was significantly upregulated in glioblastoma tissues compared with the low-grade gliomas. In addition, SLC1A5 knockdown could significantly inhibit glioma cell proliferation and invasion, and reduce the sensitivity of ferroptosis via the GPX4-dependent pathway. Furthermore, SLC1A5 was found to be related to immune response and SLC1A5 knockdown decreased the infiltration and M2 polarization of tumor-associated macrophages. Pharmacological inhibition of SLC1A5 by V9302 was confirmed to promote the efficacy of anti-PD-1 therapy. Overall, we developed a novel prognostic model for glioma based on the seven-FRGs signature, which could apply to glioma prognostic and immune status prediction. Besides, SLC1A5 in the model could regulate the proliferation, invasion, ferroptosis and immune state in glioma, and be applied as a prognostic biomarker and potential therapeutic target for glioma.

Useful genes for predicting the efficacy of transarterial chemoembolization in hepatocellular carcinoma

Transarterial chemoembolization (TACE) is generally used to treat patients with hepatocellular carcinoma (HCC), a common and deadly cancer; however, its efficacy varies according to factors such as tumor volume, stage, serum alpha-fetoprotein level, and chosen feeding artery. In addition, gene-related factors have been recently suggested to be involved in the regulation and prediction of TACE outcomes. Accordingly, genes could serve as effective biomarkers to select patients who can benefit from TACE. These gene-related factors can activate signaling pathways affecting cancer cell survival while regulating the epithelial-mesenchymal transition, angiogenesis, and the tumor microenvironment, all directly associated with tumor progression, thereby affecting TACE efficacy. Moreover, this disordered gene expression is associated with poor prognosis in patients with HCC, including TACE resistance, postoperative recurrence, and metastasis. To identify the exact relationship between various genes and TACE efficacy, this review summarizes the involvement of protein-coding and non-coding genes and single nucleotide polymorphisms in TACE efficacy for predicting the efficacy of TACE; the present findings may help improve the efficacy of TACE in clinical settings.

Recent progress of amino acid transporters as a novel antitumor target

Glutamine transporters transport different amino acids for cell growth and metabolism. In tumor cells, glutamine transporters are often highly expressed and play a crucial role in their growth. By inhibiting the amino acid transport of these transporters, the growth of cancer cells can be inhibited. In recent years, more and more attention has been paid to the study of glutamine transporter. In this article, the differences between the ASC system amino acid transporter 2 (ASCT2), L-type amino acid transporter 1 (LAT1), and the cystine–glutamate exchange (xCT) transporters research progress on the mechanism of action and corresponding small molecule inhibitors are summarized. This article introduces 62 related small molecule inhibitors of different transporters of ASCT2, LAT1, and xCT. These novel chemical structures provide ideas for the research and design of targeted inhibitors of glutamine transporters, as well as important references and clues for the design of new anti-tumor drugs.

Anti-tumor effects of P-LPK-CPT, a peptide-camptothecin conjugate, in colorectal cancer

To explore highly selective targeting molecules of colorectal cancer (CRC) is a challenge. We previously identified a twelve-amino acid peptide (LPKTVSSDMSLN, namely P-LPK) by phage display technique which may specifically binds to CRC cells. Here we show that P-LPK selectively bind to a panel of human CRC cell lines and CRC tissues. In vivo, Gallium-68 (⁶⁸Ga) labeled P-LPK exhibits selective accumulation at tumor sites. Then, we designed a peptide-conjugated drug comprising P-LPK and camptothecin (CPT) (namely P-LPK-CPT), and found P-LPK-CPT significantly inhibits tumor growth with fewer side effects in vitro and in vivo. Furthermore, through co-immunoprecipitation and molecular docking experiment, the glutamine transporter solute carrier 1 family member 5 (SLC1A5) was identified as the possible target of P-LPK. The binding ability of P-LPK and SLC1A5 is verified by surface plasmon resonance and immunofluorescence. Taken together, P-LPK-CPT is highly effective for CRC and deserves further development as a promising anti-tumor therapeutic for CRC, especially SLC1A5-high expression type.

A peptide that specifically targets amino acid transporter SLC1A5 in colorectal cancer cells is identified and conjugated with camptothecin to show selective cytotoxicity to colorectal cancer cells in preclinical models.