Kidney-Type Glutaminase Inhibitor Hexylselen Selectively Kills Cancer Cells via a Three-Pronged Mechanism

Metabolism and signaling crosstalk in glioblastoma progression and therapy resistance

Glioblastoma is the most common form of primary malignant brain tumor in adults and one of the most lethal human cancers, with high recurrence and therapy resistance. Glioblastoma cells display extensive genetic and cellular heterogeneity, which precludes a unique and common therapeutic approach. The standard of care in glioblastoma patients includes surgery followed by radiotherapy plus concomitant temozolomide. As in many other cancers, cell signaling is deeply affected due to mutations or alterations in the so-called molecular drivers. Moreover, glioblastoma cells undergo metabolic adaptations to meet the new demands in terms of energy and building blocks, with an increasing amount of evidence connecting metabolic transformation and cell signaling deregulation in this type of aggressive brain tumor. In this review, we summarize some of the most common alterations both in cell signaling and metabolism in glioblastoma, presenting an integrative discussion about how they contribute to therapy resistance. Furthermore, this review aims at providing a comprehensive overview of the state-of-the-art of therapeutic approaches and clinical trials exploiting signaling and metabolism in glioblastoma.

Evolution and variation in amide aminoacyl-tRNA synthesis

The amide proteogenic amino acids, asparagine and glutamine, are two of the twenty amino acids used in translation by all known life. The aminoacyl-tRNA synthetases for asparagine and glutamine, asparaginyl-tRNA synthetase and glutaminyl tRNA synthetase, evolved after the split in the last universal common ancestor of modern organisms. Before that split, life used two-step indirect pathways to synthesize asparagine and glutamine on their cognate tRNAs to form the aminoacyl-tRNA used in translation. These two-step pathways were retained throughout much of the bacterial and archaeal domains of life and eukaryotic organelles. The indirect routes use non-discriminating aminoacyl-tRNA synthetases (non-discriminating aspartyl-tRNA synthetase and non-discriminating glutamyl-tRNA synthetase) to misaminoacylate the tRNA. The misaminoacylated tRNA formed is then transamidated into the amide aminoacyl-tRNA used in protein synthesis by tRNA-dependent amidotransferases (GatCAB and GatDE). The enzymes and tRNAs involved assemble into complexes known as transamidosomes to help maintain translational fidelity. These pathways have evolved to meet the varied cellular needs across a diverse set of organisms, leading to significant variation. In certain bacteria, the indirect pathways may provide a means to adapt to cellular stress by reducing the fidelity of protein synthesis. The retention of these indirect pathways versus acquisition of asparaginyl-tRNA synthetase and glutaminyl tRNA synthetase in lineages likely involves a complex interplay of the competing uses of glutamine and asparagine beyond translation, energetic costs, co-evolution between enzymes and tRNA, and involvement in stress response that await further investigation.

Metabolic Rewiring in Cancer: Small Molecule Inhibitors in Colorectal Cancer Therapy

Alterations in cellular metabolism, such as dysregulation in glycolysis, lipid metabolism, and glutaminolysis in response to hypoxic and low-nutrient conditions within the tumor microenvironment, are well-recognized hallmarks of cancer. Therefore, understanding the interplay between aerobic glycolysis, lipid metabolism, and glutaminolysis is crucial for developing effective metabolism-based therapies for cancer, particularly in the context of colorectal cancer (CRC). In this regard, the present review explores the complex field of metabolic reprogramming in tumorigenesis and progression, providing insights into the current landscape of small molecule inhibitors targeting tumorigenic metabolic pathways and their implications for CRC treatment.

Participation of protein metabolism in cancer progression and its potential targeting for the management of cancer

Cancer malignancies may broadly be described as heterogeneous disorders manifested by uncontrolled cellular growth/division and proliferation. Tumor cells utilize metabolic reprogramming to accomplish the upregulated nutritional requirements for sustaining their uncontrolled growth, proliferation, and survival. Metabolic reprogramming also called altered or dysregulated metabolism undergoes modification in normal metabolic pathways for anabolic precursor's generation that serves to continue biomass formation that sustains the growth, proliferation, and survival of carcinogenic cells under a nutrition-deprived microenvironment. A wide range of dysregulated/altered metabolic pathways encompassing different metabolic regulators have been described; however, the current review is focused to explain deeply the metabolic pathways modifications inducing upregulation of proteins/amino acids metabolism. The essential modification of various metabolic cycles with their consequent outcomes meanwhile explored promising therapeutic targets playing a pivotal role in metabolic regulation and is successfully employed for effective target-specific cancer treatment. The current review is aimed to understand the metabolic reprogramming of different proteins/amino acids involved in tumor progression along with potential therapeutic perspective elucidating targeted cancer therapy via these targets.

Diselenide Covalent Allosteric Inhibitors of Glutaminase with Strong In Vivo Anticancer Activity

Allosteric glutaminase inhibitors demonstrate inhibition of glutamine-dependent cancer cells with low general drug toxicity, but have issues with efficacy in vivo. Here, we designed a series of diselenide compounds with 6 atoms in the middle, aiming to target the allosteric site of kidney type glutaminase (KGA) with a covalent linkage to strengthen the interaction. Proteomic analysis demonstrated that the diselenide compounds cross-linked with the Lys320 residue at the KGA allosteric site; this was confirmed by the KGA K320A mutant which showed essentially no binding to the diselenide. Further, structure-activity relationship (SAR) analysis demonstrated that growth inhibition correlated well with KGA inhibition and was enhanced by thioredoxin reductase (TrxR) inhibition. Interestingly, diselenide compounds showed no inhibition of glutamate dehydrogenase (GDH), indicating some enzyme selectivity. Importantly, the designed novel diselenides are glutaminase allosteric inhibitors that showed in vivo efficacy and survival in the xenograft animal model.

Synthesis of Novel Kidney-Type Glutaminase Allosteric Inhibitors Targeting the Critical Lys-320 Residue

Reversible allosteric inhibitors of kidney-type glutaminase (GLS1, KGA) showed incomplete inhibition of cancer cell proliferation and poor in vivo efficacy. Here, we investigate some irreversible inhibitors targeting the critical K320 residue responsible for GLS1 biological activity. The (trifluoromethoxy)phenylacetic acid motif was replaced by α,β-unsaturated carboxylic acids, and the resulting terminally substituted CB839 derivatives (e.g., GJ2 and GJ5) showed good stability in solid form at room temperature, and better liver microsome stability and in vivo pharmacokinetics than coumarin. Both compounds showed binding to the wild-type KGA, whose K D is 106-fold stronger than that of CB839, but only weak binding to the KGA K320A mutant and no inhibition of GDH proteins. Interestingly, GJ2 treatment significantly decreased the trypsin digestion of KGA, tumor cell clonal formation, and cancer cell growth rate. Taking these results together, targeting the critical K320 residue of GLS1 might be a new strategy to make a potent GLS1 allosteric inhibitor.

Targeting Energy Metabolism in Cancer Treatment

Cancer is the second most common cause of death worldwide after cardiovascular diseases. The development of molecular and biochemical techniques has expanded the knowledge of changes occurring in specific metabolic pathways of cancer cells. Increased aerobic glycolysis, the promotion of anaplerotic responses, and especially the dependence of cells on glutamine and fatty acid metabolism have become subjects of study. Despite many cancer treatment strategies, many patients with neoplastic diseases cannot be completely cured due to the development of resistance in cancer cells to currently used therapeutic approaches. It is now becoming a priority to develop new treatment strategies that are highly effective and have few side effects. In this review, we present the current knowledge of the enzymes involved in the different steps of glycolysis, the Krebs cycle, and the pentose phosphate pathway, and possible targeted therapies. The review also focuses on presenting the differences between cancer cells and normal cells in terms of metabolic phenotype. Knowledge of cancer cell metabolism is constantly evolving, and further research is needed to develop new strategies for anti-cancer therapies.

Self-Assembled Micellar Glutaminase Allosteric Inhibitor for Effective Therapeutic Intervention

Introduction

Methods

Results

Conclusion

Biodegradable self-assembly micelles significantly enhanced the solubility, biological stability and in vivo antitumor efficacy of Hexylselen

Glutaminolysis inhibitors have shown early promise in cancer therapeutics. Specifically, kidney-type glutaminase (KGA) has been a long-standing anti-tumor drug target; KGA allosteric inhibitors have attracted great attention due to their superior enzyme specificity and good drug safety profiles. However, the main issue with allosteric inhibitors—including BPTES, CB-839, and the recently developed KGA allosteric and glutamate dehydrogenase (GDH) dual inhibitor, Hexylselen (CPD-3B)—is their low solubility; it leads to limited in vivo efficacy. To optimize their formulation, various delivery carriers were screened in the present study. Soluplus® (SOL), an amphiphilic graft polymer, showed an interesting structure–solubility/activity relationship with Selen molecules containing different middle chain sizes. Among these molecules, the long chain molecule CPD-3B showed 3000-fold increased solubility with SOL, forming well-dispersed and stable micelles 60–80 nm in size. Moreover, CPD-3B@SOL micelles exhibited good metabolic stability in both blood and liver microsomes. These advantages significantly enhanced the bioavailability and in vivo antitumor efficacy of CPD-3B@SOL micelles in the H22 hepatocarcinoma xenograft mouse model. Thus, the current study provided a practical delivery system for allosteric inhibitors of glutaminase, which is one of the bottlenecks of targeting tumor glutaminolysis.

Soluplus increased the aqueous solubility of Hexylselen (CPD-3B) by about 3000-fold forming nano-sized micelles, significantly enhanced the stability in blood and liver microsomes and improved the in vivo bioavailability and antitumor efficacy.

Small molecule selenium-containing compounds: Recent development and therapeutic applications

Selenium (Se) is an essential micronutrient of organism and has important function. It participates in the functions of selenoprotein in several manners. In recent years, Se has attracted much attention because of its therapeutic potential against several diseases. Many natural and synthetic organic Se-containing compounds were studied and explored for the treatment of cancer and other diseases. Studies have showed that incorporation of Se atom into small molecules significantly enhanced their bioactivities. In this paper, according to different applications and structural characteristics, the research progress and therapeutic application of Se-containing compounds are reviewed, and more than 110 Se-containing compounds were selected as representatives which showed potent activities such as anticancer, antioxidant, antifibrolytic, antiparasitic, antibacterial, antiviral, antifungal and central nervous system related effects. This review is expected to provide a basis for further study of new promising Se-containing compounds.

A sensitive EZMTT method provides microscale, quantitative and high-throughput evaluation of drug efficacy in the treatment of Mycobacterium tuberculosis infectious diseases

Drug resistance has become a serious public health problem in mycobacterial infectious diseases. Here, we investigated a water soluble tetrazolium salt (EZMTT)-based detection method to provide an easy, safe and quantitative antimycobacterial susceptibility test (AMST) method, especially for targeting early detection of loss of drug susceptibility in mycobacteria. After a single addition of the EZMTT detection reagent at the inoculation of mycobacteria culture, the AMST was continuously analyzed in a sealed 96-well plate (100 μl), or a sealed tube to ensure biosafety. Using Mycobacterium tuberculosis H37Ra as the model strain, the EZMTT assay was developed with high reproducibility (Z factor of 0.64) for facile measurements of growth and drug susceptibility. In the comparative AMST study, the 7-day EZMTT method identified not only the same set of drug resistance as the other two methods (the 30-day traditional Löwenstein Jensen solid medium assay and the 10-14 day 8 ml Mycobacteria Growth Indicator Tube liquid method), but also additional strains with loss of drug susceptibility. In conclusion, we demonstrated that the EZMTT-based AMST assay in a sealed microtiter plate has great potential for routine use in medical diagnosis and drug screening to battle the unmet medical need in the treatment of multi- and extensive-drug resistant mycobacteria.

New insights into molecules and pathways of cancer metabolism and therapeutic implications

Cancer cells are abnormal cells that can reproduce and regenerate rapidly. They are characterized by unlimited proliferation, transformation and migration, and can destroy normal cells. To meet the needs for cell proliferation and migration, tumor cells acquire molecular materials and energy through unusual metabolic pathways as their metabolism is more vigorous than that of normal cells. Multiple carcinogenic signaling pathways eventually converge to regulate three major metabolic pathways in tumor cells, including glucose, lipid, and amino acid metabolism. The distinct metabolic signatures of cancer cells reflect that metabolic changes are indispensable for the genesis and development of tumor cells. In this review, we report the unique metabolic alterations in tumor cells which occur through various signaling axes, and present various modalities available for cancer diagnosis and clinical therapy. We further provide suggestions for the development of anti‐tumor therapeutic drugs.

Design and synthesis of biotinylated Hexylselen as a probe to identify KGA allosteric inhibitors by a convenient biomolecular interaction assay

Hexylselen is a novel submicromolar dual KGA/GDH inhibitor, which demonstrates potent inhibition of cancer cells with minimal toxicity. To further investigation its mechanism of action, we designed and synthesized its biotinylated derivative 2 as a novel probe. From commercially available starting material, 2 was obtained in 6 steps with 13.4% overall yield. It is notable that this practical synthetic route give a template for the preparation of unsymmetrical di-benzo[d][1,2]selenazol-3(2H)-ones. Based on probe 2, we developed a novel biomolecular interaction assay for convenient and reliable test of KGA allosteric inhibitors and confirmed that hexylselen as an allosteric inhibitor of KGA sharing the same binding pocket with BPTES but not with Ebselen via competitive experiments.

Therapeutic targeting of glutaminolysis as an essential strategy to combat cancer

Metabolic reprogramming in cancer targets glutamine metabolism as a key mechanism to provide energy, biosynthetic precursors and redox requirements to allow the massive proliferation of tumor cells. Glutamine is also a signaling molecule involved in essential pathways regulated by oncogenes and tumor suppressor factors. Glutaminase isoenzymes are critical proteins to control glutaminolysis, a key metabolic pathway for cell proliferation and survival that directs neoplasms' fate. Adaptive glutamine metabolism can be altered by different metabolic therapies, including the use of specific allosteric inhibitors of glutaminase that can evoke synergistic effects for the therapy of cancer patients. We also review other clinical applications of in vivo assessment of glutaminolysis by metabolomic approaches, including diagnosis and monitoring of cancer.