Targeting arginine metabolism pathway to treat arginine-dependent cancers

Metabolic responses to the occurrence and chemotherapy of pancreatic cancer: biomarker identification and prognosis prediction

As the most malignant tumor, the prognosis of pancreatic cancer is not ideal even in the small number of patients who can undergo radical surgery. As a highly heterogeneous tumor, chemotherapy resistance is a major factor leading to decreased efficacy and postoperative recurrence of pancreatic cancer. In this study, nuclear magnetic resonance (NMR)-based metabolomics was applied to identify serum metabolic characteristics of pancreatic ductal adenocarcinoma (PDAC) and screen the potential biomarkers for its diagnosis. Metabolic changes of patients with different CA19-9 levels during postoperative chemotherapy were also monitored and compared to identify the differential metabolites that may affect the efficacy of chemotherapy. Finally, 19 potential serum biomarkers were screened to serve the diagnosis of PDAC, and significant metabolic differences between the two CA19-9 stratifications of PDAC were involved in energy metabolism, lipid metabolism, amino acid metabolism, and citric acid metabolism. Enrichment analysis of metabolic pathways revealed six shared pathways by PDAC and chemotherapy such as alanine, aspartate and glutamate metabolism, arginine biosynthesis, glutamine and glutamate metabolism, citrate cycle, pyruvate metabolism, and glycogolysis/gluconeogeneis. The similarity between the metabolic characteristics of PDAC and the metabolic responses to chemotherapy provided a reference for clinical prediction of benefits of postoperative chemotherapy in PDAC patients.

Metabolic instruction of the graft-versus-leukemia immunity

Allogeneic hematopoietic cell transplantation (allo-HCT) is frequently performed to cure hematological malignancies, such as acute myeloid leukemia (AML), through the graft-versus-leukemia (GVL) effect. In this immunological process, donor immune cells eliminate residual cancer cells in the patient and exert tumor control through immunosurveillance. However, GVL failure and subsequent leukemia relapse are frequent and associated with a dismal prognosis. A better understanding of the mechanisms underlying AML immune evasion is essential for developing novel therapeutic strategies to boost the GVL effect. Cellular metabolism has emerged as an essential regulator of survival and cell fate for both cancer and immune cells. Leukemia and T cells utilize specific metabolic programs, including the orchestrated use of glucose, amino acids, and fatty acids, to support their growth and function. Besides regulating cell-intrinsic processes, metabolism shapes the extracellular environment and plays an important role in cell-cell communication. This review focuses on recent advances in the understanding of how metabolism might affect the anti-leukemia immune response. First, we provide a general overview of the mechanisms of immune escape after allo-HCT and an introduction to leukemia and T cell metabolism. Further, we discuss how leukemia and myeloid cell metabolism contribute to an altered microenvironment that impairs T cell function. Next, we review the literature linking metabolic processes in AML cells with their inhibitory checkpoint ligand expression. Finally, we focus on recent findings concerning the role of systemic metabolism in sustained GVL efficacy. While the majority of evidence in the field still stems from basic and preclinical studies, we discuss translational findings and propose further avenues for bridging the gap between bench and bedside.

Unraveling the mechanism of Yiqi Jiedu formula against nasopharyngeal carcinoma: An investigation integrating network pharmacology, serum pharmacochemistry, and metabolomics

ETHNOPHARMACOLOGICAL RELEVANCE

Yiqi Jiedu formula (YQJDF), rooted in the traditional Chinese medicinal principle of "tonifying qi and detoxifying", is remarkably efficacious in the clinical treatment of nasopharyngeal carcinoma (NPC). Previous studies have shed light on some of its anti-NPC effects and mechanisms, but the responsible pharmacological substances and their precise mechanisms of action remain unclear.

AIM OF THE STUDY

The purpose of this study was to identify components of YQJDF that entered the bloodstream and to investigate their mechanisms of action against NPC through network pharmacology and serum metabolomics.

MATERIAL AND METHODS

Components of YQJDF in serum were identified using liquid chromatography-tandem mass spectrometry. With these serum species as the focus of our research, network pharmacology analysis was used to identify active compounds and target genes that might mediate the efficacy of YQJDF in the treatment of NPC. Following establishment of an NPC xenograft model in nude mice, a non-targeted metabolomics approach was adopted to identify significant serum metabolites and metabolic pathways influenced by YQJDF.

RESULTS

Thirty-six components of YQJDF were identified, primarily consisting of alkaloids, phenylpropanoids, and flavonoids. Notably, pathways such as PI3K/AKT, factors associated with Epstein-Barr virus infection, IL-17 signaling, and lipid metabolism, were highlighted as potential therapeutic targets of YQJDF during NPC treatment. Additionally, our findings suggested that YQJDF modified the metabolism of arginine and proline in the serum of mice bearing nasopharyngeal tumor grafts.

CONCLUSIONS

This study identified the primary active components of YQJDF, highlighting its holistic role in the treatment of NPC through multiple targets and pathways. Furthermore, our findings provided a roadmap for future research into the mechanism of YQJDF in the therapy of NPC, setting the stage for its clinical application.

Amino acid metabolism in tumor biology and therapy

Amino acid metabolism plays important roles in tumor biology and tumor therapy. Accumulating evidence has shown that amino acids contribute to tumorigenesis and tumor immunity by acting as nutrients, signaling molecules, and could also regulate gene transcription and epigenetic modification. Therefore, targeting amino acid metabolism will provide new ideas for tumor treatment and become an important therapeutic approach after surgery, radiotherapy, and chemotherapy. In this review, we systematically summarize the recent progress of amino acid metabolism in malignancy and their interaction with signal pathways as well as their effect on tumor microenvironment and epigenetic modification. Collectively, we also highlight the potential therapeutic application and future expectation.

Inhibition of HSP90 in Driver Oncogene-Defined Lung Adenocarcinoma Cell Lines: Key Proteins Underpinning Therapeutic Efficacy

The use of 90 kDa heat shock protein (HSP90) inhibition as a therapy in lung adenocarcinoma remains limited due to moderate drug efficacy, the emergence of drug resistance, and early tumor recurrence. The main objective of this research is to maximize treatment efficacy in lung adenocarcinoma by identifying key proteins underlying HSP90 inhibition according to molecular background, and to search for potential biomarkers of response to this therapeutic strategy. Inhibition of the HSP90 chaperone was evaluated in different lung adenocarcinoma cell lines representing the most relevant molecular alterations (EGFR mutations, KRAS mutations, or EML4-ALK translocation) and wild-type genes found in each tumor subtype. The proteomic technique iTRAQ was used to identify proteomic profiles and determine which biological pathways are involved in the response to HSP90 inhibition in lung adenocarcinoma. We corroborated the greater efficacy of HSP90 inhibition in EGFR mutated or EML4-ALK translocated cell lines. We identified proteins specifically and significantly deregulated after HSP90 inhibition for each molecular alteration. Two proteins, ADI1 and RRP1, showed independently deregulated molecular patterns. Functional annotation of the altered proteins suggested that apoptosis was the only pathway affected by HSP90 inhibition across all molecular subgroups. The expression of ADI1 and RRP1 could be used to monitor the correct inhibition of HSP90 in lung adenocarcinoma. In addition, proteins such as ASS1, ITCH, or UBE2L3 involved in pathways related to the inhibition of a particular molecular background could be used as potential response biomarkers, thereby improving the efficacy of this therapeutic approach to combat lung adenocarcinoma.

Arginine mediated photodynamic therapy with silicon(IV) phthalocyanine photosensitizers

In the current study, we synthesized a new SiPc derivative conjugated with arginine at the axial positions, for a novel phthalocyanine-based photosensitizer for photodynamic therapy (PDT) applications in cancer cells. Axially-di-arginine substituted new silicon(IV) phthalocyanine photosensitizer (PS-5a) has been thoroughly researched for its anti-cancer properties. Various spectroscopic techniques were used to characterize this conjugate, including 1H NMR, 13C NMR, FT-IR, UV-vis, and MS spectral data. The in vitro PDT activities of the conjugate on cancer cells were tested through its cytotoxic, clonogenic, apoptotic effects on, and its capacity to induce DNA damage, and the disruption of mitochondrial membrane potential in cancer cell lines (liver; HuH-7, cervix; HeLa and breast; MCF7). Cancer cells exposed to the light illumination following uptake of the PS-5a as a photosensitizer revealed DNA breakage and collapsed mitochondrial membrane potential. The results of the present investigation demonstrate that PS-5a has a significant photo-cytotoxic effect on cancer cells. So, axially-di-arginine substituted silicon(IV) phthalocyanine could be an effective PDT agent for PDT treatment.

Discovery and Targeting of a Noncanonical Mechanism of Sarcoma Resistance to ADI-PEG20 Mediated by the Microenvironment

PURPOSE

Many cancers lack argininosuccinate synthetase 1 (ASS1), the rate-limiting enzyme of arginine biosynthesis. This deficiency causes arginine auxotrophy, targetable by extracellular arginine-degrading enzymes such as ADI-PEG20. Long-term tumor resistance has thus far been attributed solely to ASS1 reexpression. This study examines the role of ASS1 silencing on tumor growth and initiation and identifies a noncanonical mechanism of resistance, aiming to improve clinical responses to ADI-PEG20.

EXPERIMENTAL DESIGN

Tumor initiation and growth rates were measured for a spontaneous Ass1 knockout (KO) murine sarcoma model. Tumor cell lines were generated, and resistance to arginine deprivation therapy was studied in vitro and in vivo.

RESULTS

Conditional Ass1 KO affected neither tumor initiation nor growth rates in a sarcoma model, contradicting the prevalent idea that ASS1 silencing confers a proliferative advantage. Ass1 KO cells grew robustly through arginine starvation in vivo, while ADI-PEG20 remained completely lethal in vitro, evidence that pointed toward a novel mechanism of resistance mediated by the microenvironment. Coculture with Ass1-competent fibroblasts rescued growth through macropinocytosis of vesicles and/or cell fragments, followed by recycling of protein-bound arginine through autophagy/lysosomal degradation. Inhibition of either macropinocytosis or autophagy/lysosomal degradation abrogated this growth support effect in vitro and in vivo.

CONCLUSIONS

Noncanonical, ASS1-independent tumor resistance to ADI-PEG20 is driven by the microenvironment. This mechanism can be targeted by either the macropinocytosis inhibitor imipramine or the autophagy inhibitor chloroquine. These safe, widely available drugs should be added to current clinical trials to overcome microenvironmental arginine support of tumors and improve patient outcomes.

Human arginase I: a potential broad-spectrum anti-cancer agent

With high rates of morbidity and mortality, cancer continues to pose a serious threat to public health on a global scale. Considering the discrepancies in metabolism between cancer and normal cells, metabolism-based anti-cancer biopharmaceuticals are gaining importance. Normal cells can synthesize arginine, but they can also take up extracellular arginine, making it a semi-essential amino acid. Arginine auxotrophy occurs when a cancer cell has abnormalities in the enzymes involved in arginine metabolism and relies primarily on extracellular arginine to support its biological functions. Taking advantage of arginine auxotrophy in cancer cells, arginine deprivation, which can be induced by introducing recombinant human arginase I (rhArg I), is being developed as a broad-spectrum anti-cancer therapy. This has led to the development of various rhArg I variants, which have shown remarkable anti-cancer activity. This article discusses the importance of arginine auxotrophy in cancer and different arginine-hydrolyzing enzymes that are in various stages of clinical development and reviews the need for a novel rhArg I that mitigates the limitations of the existing therapies. Further, we have also analyzed the necessity as well as the significance of using rhArg I to treat various arginine-auxotrophic cancers while considering the importance of their genetic profiles, particularly urea cycle enzymes.

Out of the cycle: Impact of cell cycle aberrations on cancer metabolism and metastasis

The use of cell cycle inhibitors has necessitated a better understanding of the cell cycle in tumor biology to optimize the therapeutic approach. Cell cycle aberrations are common in cancers, and it is increasingly acknowledged that these aberrations exert oncogenic effects beyond the cell cycle. Multiple facets such as cancer metabolism, immunity and metastasis are also affected, all of which are beyond the effect of cell proliferation alone. This review comprehensively summarized the important recent findings and advances in these interrelated processes. In cancer metabolism, cell cycle regulators can modulate various pathways in aerobic glycolysis, glucose uptake and gluconeogenesis, mainly through transcriptional regulation and kinase activities. Amino acid metabolism is also regulated through cell cycle progression. On cancer metastasis, metabolic plasticity, immune evasion, tumor microenvironment adaptation and metastatic site colonization are intricately related to the cell cycle, with distinct regulatory mechanisms at each step of invasion and dissemination. Throughout the synthesis of current understanding, knowledge gaps and limitations in the literature are also highlighted, as are new therapeutic approaches such as combinational therapy and challenges in tackling emerging targeted therapy resistance. A greater understanding of how the cell cycle modulates diverse aspects of cancer biology can hopefully shed light on identifying new molecular targets by harnessing the vast potential of the cell cycle.

Untargeted metabolomics reveals alternations in metabolism of bovine mammary epithelial cells upon IFN-γ treatment

BACKGROUND

IFN-γ is a pleiotropic cytokine that has been shown to affect multiple cellular functions of bovine mammary epithelial cells (BMECs) including impaired milk fat synthesis and induction of malignant transformation via depletion of arginine, one of host conditionally essential amino acids. But the molecular mechanisms of these IFN-γ induced phenotypes are still unknown.

METHODS

BMECs were treated with IFN-γ for 6 h, 12 h, and 24 h. The metabolomic profiling in BMECs upon IFN-γ induction were assessed using untargeted ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) metabolomic analysis. Key differentially expressed metabolites (DEMs) were quantified by targeted metabolomics.

RESULTS

IFN-γ induction resulted in significant differences in the contents of metabolites. Untargeted analysis identified 221 significantly DEMs, most of which are lipids and lipid-like molecules, organic acids and derivatives, organ heterocyclic compounds and benzenoids. According to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, DEMs were enriched in fructose and mannose metabolism, phosphotransferase system (PTS), β-alanine metabolism, arginine and proline metabolism, methane metabolism, phenylalanine metabolism, and glycolysis/gluconeogenesis. Quantification of selected key DEMs by targeted metabolomics showed significantly decreased levels of D-(-)-mannitol, argininosuccinate, and phenylacetylglycine (PAG), while increased levels in S-hydroxymethylglutathione (S-HMG) and 2,3-bisphospho-D-glyceric acid (2,3-BPG).

CONCLUSIONS

These results provide insights into the metabolic alterations in BMECs upon IFN-γ induction and indicate potential theoretical basis for clarifying IFN-γ-induced diseases in mammary gland.

Metabolomics study of ribavirin in the treatment of orthotopic lung cancer based on UPLC-Q-TOF/MS

Ribavirin is a common antiviral drug, especially for patients with hepatitis C. Our recent studies demonstrated that ribavirin showed anti-tumor activity in colorectal cancer and hepatocellular carcinoma, but its effects on lung cancer remains unclear. This study aimed to evaluate the anti-tumor activity of ribavirin against lung cancer and elucidate the underlying mechanism. We established orthotopic mouse model of lung cancer (LLC and GLC-82) and employed an ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS)-based metabolomics approach. We found that ribavirin significantly inhibited the proliferation and colony formation of lung cancer cells. Tumor sizes of orthotopic lung cancer in ribavirin-treated groups were also significantly lower than those in control groups. Metabolomics analysis revealed that ribavirin mainly affected 5 metabolic pathways in orthotopic lung tumor models, taurine and hypotaurine metabolism, nicotinate and nicotinamide metabolism, linoleic acid metabolism, arginine biosynthesis and arachidonic acid metabolism. Furthermore, we identified 5 upregulated metabolites including β-nicotinamide adenine dinucleotide (NAD⁺), nicotinamide (NAM), taurine, ornithine and citrulline, and 7 downregulated metabolites including 1-methylnicotinamide (MNAM), S-adenosyl-l-homocysteine (SAH), N1-Methyl-2-pyridone-5-carboxamide (2PY), homocysteine (Hcy), linoleic acid, arachidonic acid (AA) and argininosuccinic acid in ribavirin-treated groups. These results provide new insight into the anti-tumor mechanism of ribavirin for lung cancer.

Targeting cancer-specific metabolic pathways for developing novel cancer therapeutics

Cancer is a heterogeneous disease characterized by various genetic and phenotypic aberrations. Cancer cells undergo genetic modifications that promote their proliferation, survival, and dissemination as the disease progresses. The unabated proliferation of cancer cells incurs an enormous energy demand that is supplied by metabolic reprogramming. Cancer cells undergo metabolic alterations to provide for increased energy and metabolite requirement; these alterations also help drive the tumor progression. Dysregulation in glucose uptake and increased lactate production via "aerobic glycolysis" were described more than 100 years ago, and since then, the metabolic signature of various cancers has been extensively studied. However, the extensive research in this field has failed to translate into significant therapeutic intervention, except for treating childhood-ALL with amino acid metabolism inhibitor L-asparaginase. Despite the growing understanding of novel metabolic alterations in tumors, the therapeutic targeting of these tumor-specific dysregulations has largely been ineffective in clinical trials. This chapter discusses the major pathways involved in the metabolism of glucose, amino acids, and lipids and highlights the inter-twined nature of metabolic aberrations that promote tumorigenesis in different types of cancer. Finally, we summarise the therapeutic interventions which can be used as a combinational therapy to target metabolic dysregulations that are unique or common in blood, breast, colorectal, lung, and prostate cancer.

Predictive markers for efficiency of the amino-acid deprivation therapies in cancer

Amino acid deprivation therapy (AADT) is a promising strategy for developing novel anticancer treatments, based on variations in metabolism of healthy and malignant cells. L-asparaginase was the first amino acid-degrading enzyme that received FDA approval for the treatment of acute lymphoblastic leukemia (ALL). Arginase and arginine deiminase were effective in clinical trials for the treatment of metastatic melanomas and hepatocellular carcinomas. Essential dependence of certain cancer cells on methionine explains the anticancer efficacy of methionine-g-lyase. Along with significant progress in identification of metabolic vulnerabilities of cancer cells, new amino acid-cleaving enzymes appear as promising agents for cancer treatment: lysine oxidase, tyrosine phenol-lyase, cysteinase, and phenylalanine ammonia-lyase. However, sensitivity of specific cancer cell types to these enzymes differs. Hence, search for prognostic and predictive markers for AADT and introduction of the markers into clinical practice are of great importance for translational medicine. As specific metabolic pathways in cancer cells are determined by the enzyme expression, some of these enzymes may define the sensitivity to AADT. This review considers the known predictors for efficiency of AADT, emphasizing the importance of knowledge on cancer-specific amino acid significance for such predictions.

Human amniotic epithelial cells exert anti-cancer effects through secretion of immunomodulatory small extracellular vesicles (sEV)

We identified here mechanism by which hAECs exert their anti-cancer effects. We showed that vaccination with live hAEC conferred effective protection against murine colon cancer and melanoma but not against breast cancer in an orthotopic cancer cell inoculation model. hAEC induced strong cross-reactive antibody response to CT26 cells, but not against B16F10 and 4T1 cells. Neither heterotopic injection of tumor cells in AEC-vaccinated mice nor vaccination with hAEC lysate conferred protection against melanoma or colon cancer. Nano-sized AEC-derived small-extracellular vesicles (sEV) (AD-sEV) induced apoptosis in CT26 cells and inhibited their proliferation. Co-administration of AD-sEV with tumor cells substantially inhibited tumor development and increased CTL responses in vaccinated mice. AD-sEV triggered the Warburg’s effect leading to Arginine consumption and cancer cell apoptosis. Our results clearly showed that it is AD-sEV but not the cross-reactive immune responses against tumor cells that mediate inhibitory effects of hAEC on cancer development. Our results highlight the potential anti-cancer effects of extracellular vesicles derived from hAEC.

Anti-cancer effects of hAEC depend on cancer type.

Cross-reactive humoral responses do not mediate anti-cancer effects of hAEC.

Anti-cancer effects of hAECs are mainly mediated by small-extracellular vesicles (sEV).

hAEC-derived sEV (AD-sEV) trigger the Warburg’s effect leading to Arginine consumption and cancer cell apoptosis.

AD-sEV substantially inhibits tumor development and increases survival and CTL responses.

Mitochondrial metabolic determinants of multiple myeloma growth, survival, and therapy efficacy

Multiple myeloma (MM) is a plasma cell dyscrasia characterized by the clonal proliferation of antibody producing plasma cells. Despite the use of next generation proteasome inhibitors (PI), immunomodulatory agents (IMiDs) and immunotherapy, the development of therapy refractory disease is common, with approximately 20% of MM patients succumbing to aggressive treatment-refractory disease within 2 years of diagnosis. A large emphasis is placed on understanding inter/intra-tumoral genetic, epigenetic and transcriptomic changes contributing to relapsed/refractory disease, however, the contribution of cellular metabolism and intrinsic/extrinsic metabolites to therapy sensitivity and resistance mechanisms is less well understood. Cancer cells depend on specific metabolites for bioenergetics, duplication of biomass and redox homeostasis for growth, proliferation, and survival. Cancer therapy, importantly, largely relies on targeting cellular growth, proliferation, and survival. Thus, understanding the metabolic changes intersecting with a drug's mechanism of action can inform us of methods to elicit deeper responses and prevent acquired resistance. Knowledge of the Warburg effect and elevated aerobic glycolysis in cancer cells, including MM, has allowed us to capitalize on this phenomenon for diagnostics and prognostics. The demonstration that mitochondria play critical roles in cancer development, progression, and therapy sensitivity despite the inherent preference of cancer cells to engage aerobic glycolysis has re-invigorated deeper inquiry into how mitochondrial metabolism regulates tumor biology and therapy efficacy. Mitochondria are the sole source for coupled respiration mediated ATP synthesis and a key source for the anabolic synthesis of amino acids and reducing equivalents. Beyond their core metabolic activities, mitochondria facilitate apoptotic cell death, impact the activation of the cytosolic integrated response to stress, and through nuclear and cytosolic retrograde crosstalk maintain cell fitness and survival. Here, we hope to shed light on key mitochondrial functions that shape MM development and therapy sensitivity.

TM4SF5-Mediated Regulation of Hepatocyte Transporters during Metabolic Liver Diseases

Nonalcoholic fatty liver disease (NAFLD) is found in up to 30% of the world’s population and can lead to hepatocellular carcinoma (HCC), which has a poor 5-year relative survival rate of less than 40%. Clinical therapeutic strategies are not very successful. The co-occurrence of metabolic disorders and inflammatory environments during the development of steatohepatitis thus needs to be more specifically diagnosed and treated to prevent fatal HCC development. To improve diagnostic and therapeutic strategies, the identification of molecules and/or pathways responsible for the initiation and progression of chronic liver disease has been explored in many studies, but further study is still required. Transmembrane 4 L six family member 5 (TM4SF5) has been observed to play roles in the regulation of metabolic functions and activities in hepatocytes using in vitro cell and in vivo animal models without or with TM4SF5 expression in addition to clinical liver tissue samples. TM4SF5 is present on the membranes of different organelles or vesicles and cooperates with transporters for fatty acids, amino acids, and monocarbohydrates, thus regulating nutrient uptake into hepatocytes and metabolism and leading to phenotypes of chronic liver diseases. In addition, TM4SF5 can remodel the immune environment by interacting with immune cells during TM4SF5-mediated chronic liver diseases. Because TM4SF5 may act as an NAFLD biomarker, this review summarizes crosstalk between TM4SF5 and nutrient transporters in hepatocytes, which is related to chronic liver diseases.

Arginase: Mechanisms and Clinical Application in Hematologic Malignancy

Compared to normal tissues and cells, the metabolic patterns of tumor illnesses are more complex, and there are hallmarks of metabolic reprogramming in energy metabolism, lipid metabolism, and amino acid metabolism. When tumor cells are in a state of fast growth, they are susceptible to food shortage, resulting in growth suppression. Using this metabolic sensitivity of tumor cells to construct amino acid consumption therapy does not harm the function of normal cells, which is the focus of metabolic therapy research at the moment. As a non-essential amino acid, arginine is involved in numerous crucial biological processes, including the signaling system, cell proliferation, and material metabolism. Rapidly dividing tumor cells are more likely to be deficient in arginine; hence, utilizing arginase to consume arginine can suppress tumor growth. Due to the absence of arginine succinate synthase, arginine succinate lyase, and ornithine carbamoyl transferase in some blood tumors, arginases may be employed to treat blood tumors. By investigating the mechanism of arginase treatment and the mechanism of drug resistance in greater depth, arginase treatment becomes more successful in hematological cancers and a new anti-cancer agent in clinical practice.

Multi-Scale Spatial Analysis of the Tumor Microenvironment Reveals Features of Cabozantinib and Nivolumab Efficacy in Hepatocellular Carcinoma

Background

Concomitant inhibition of vascular endothelial growth factor (VEGF) and programmed cell death protein 1 (PD-1) or its ligand PD-L1 is a standard of care for patients with advanced hepatocellular carcinoma (HCC), but only a minority of patients respond, and responses are usually transient. Understanding the effects of therapies on the tumor microenvironment (TME) can provide insights into mechanisms of therapeutic resistance.

Methods

14 patients with HCC were treated with the combination of cabozantinib and nivolumab through the Johns Hopkins Sidney Kimmel Comprehensive Cancer Center. Among them, 12 patients (5 responders + 7 non-responders) underwent successful margin negative resection and are subjects to tissue microarray (TMA) construction containing 37 representative tumor region cores. Using the TMAs, we performed imaging mass cytometry (IMC) with a panel of 27-cell lineage and functional markers. All multiplexed images were then segmented to generate a single-cell dataset that enables (1) tumor-immune compartment analysis and (2) cell community analysis based on graph-embedding methodology. Results from these hierarchies are merged into response-associated biological process patterns.

Results

Image processing on 37 multiplexed-images discriminated 59,453 cells and was then clustered into 17 cell types. Compartment analysis showed that at immune-tumor boundaries from NR, PD-L1 level on tumor cells is significantly higher than remote regions; however, Granzyme B expression shows the opposite pattern. We also identify that the close proximity of CD8⁺ T cells to arginase 1^hi (Arg1^hi) macrophages, rather than CD4⁺ T cells, is a salient feature of the TME in non-responders. Furthermore, cell community analysis extracted 8 types of cell-cell interaction networks termed cellular communities (CCs). We observed that in non-responders, macrophage-enriched CC (MCC) and lymphocyte-enriched CC (LCC) strongly communicate with tumor CC, whereas in responders, such communications were undermined by the engagement between MCC and LCC.

Conclusion

These results demonstrate the feasibility of a novel application of multiplexed image analysis that is broadly applicable to quantitative analysis of pathology specimens in immuno-oncology and provides further evidence that CD163^-Arg1^hi macrophages may be a therapeutic target in HCC. The results also provide critical information for the development of mechanistic quantitative systems pharmacology models aimed at predicting outcomes of clinical trials.

Impacts and mechanisms of metabolic reprogramming of tumor microenvironment for immunotherapy in gastric cancer

Metabolic disorders and abnormal immune function changes occur in tumor tissues and cells to varying degrees. There is increasing evidence that reprogrammed energy metabolism contributes to the development of tumor suppressive immune microenvironment and influences the course of gastric cancer (GC). Current studies have found that tumor microenvironment (TME) also has important clinicopathological significance in predicting prognosis and therapeutic efficacy. Novel approaches targeting TME therapy, such as immune checkpoint blockade (ICB), metabolic inhibitors and key enzymes of immune metabolism, have been involved in the treatment of GC. However, the interaction between GC cells metabolism and immune metabolism and how to make better use of these immunotherapy methods in the complex TME in GC are still being explored. Here, we discuss how metabolic reprogramming of GC cells and immune cells involved in GC immune responses modulate anti-tumor immune responses, as well as the effects of gastrointestinal flora in TME and GC. It is also proposed how to enhance anti-tumor immune response by understanding the targeted metabolism of these metabolic reprogramming to provide direction for the treatment and prognosis of GC.

Carbon Ion Radiotherapy Evokes a Metabolic Reprogramming and Individualized Response in Prostate Cancer

Introduction: Carbon ion radiotherapy (CIRT) is a novel treatment for prostate cancer (PCa). However, the underlying mechanism for the individualized response to CIRT is still not clear. Metabolic reprogramming is essential for tumor growth and proliferation. Although changes in metabolite profiles have been detected in patients with cancer treated with photon radiotherapy, there is limited data regarding CIRT-induced metabolic changes in PCa. Therefore, the study aimed to investigate the impact of metabolic reprogramming on individualized response to CIRT in patients with PCa.

Materials and Methods: Urine samples were collected from pathologically confirmed patients with PCa before and after CIRT. A UPLC-MS/MS system was used for metabolite detection. XCMS online, MetDNA, and MS-DIAL were used for peak detection and identification of metabolites. Statistical analysis and metabolic pathway analysis were performed on MetaboAnalyst.

Results: A total of 1,701 metabolites were monitored in this research. Principal component analysis (PCA) revealed a change in the patient's urine metabolite profiles following CIRT. Thirty-five metabolites were significantly altered, with the majority of them being amino acids. The arginine biosynthesis and histidine metabolism pathways were the most significantly altered pathways. Hierarchical cluster analysis (HCA) showed that after CIRT, the patients could be clustered into two groups according to their metabolite profiles. The arginine biosynthesis and phenylalanine, tyrosine, and tryptophan biosynthesis pathways are the most significantly discriminated pathways.

Conclusion: Our preliminary findings indicate that metabolic reprogramming and inhibition are important mechanisms involved in response to CIRT in patients with PCa. Therefore, changes in urine metabolites could be used to timely assess the individualized response to CIRT.

Oxidative Stress and X-ray Exposure Levels-Dependent Survival and Metabolic Changes in Murine HSPCs

Haematopoietic bone marrow cells are amongst the most sensitive to ionizing radiation (IR), initially resulting in cell death or genotoxicity that may later lead to leukaemia development, most frequently Acute Myeloid Leukaemia (AML). The target cells for radiation-induced Acute Myeloid Leukaemia (rAML) are believed to lie in the haematopoietic stem and progenitor cell (HSPC) compartment. Using the inbred strain CBA/Ca as a murine model of rAML, progress has been made in understanding the underlying mechanisms, characterisation of target cell population and responses to IR. Complex regulatory systems maintain haematopoietic homeostasis which may act to modulate the risk of rAML. However, little is currently known about the role of metabolic factors and diet in these regulatory systems and modification of the risk of AML development. This study characterises cellular proliferative and clonogenic potential as well as metabolic changes within murine HSPCs under oxidative stress and X-ray exposure. Ambient oxygen (normoxia; 20.8% O2) levels were found to increase irradiated HSPC-stress, stimulating proliferative activity compared to low oxygen (3% O2) levels. IR exposure has a negative influence on the proliferative capability of HSPCs in a dose-dependent manner (0-2 Gy) and this is more pronounced under a normoxic state. One Gy x-irradiated HSPCs cultured under normoxic conditions displayed a significant increase in oxygen consumption compared to those cultured under low O2 conditions and to unirradiated HSPCs. Furthermore, mitochondrial analyses revealed a significant increase in mitochondrial DNA (mtDNA) content, mitochondrial mass and membrane potential in a dose-dependent manner under normoxic conditions. Our results demonstrate that both IR and normoxia act as stressors for HSPCs, leading to significant metabolic deregulation and mitochondrial dysfunctionality which may affect long term risks such as leukaemia.

The Importance of Cellular Metabolic Pathways in Pathogenesis and Selective Treatments of Hematological Malignancies

Despite recent advancements in the treatment of hematologic malignancies and the emergence of newer and more sophisticated therapeutic approaches such as immunotherapy, long-term overall survival remains unsatisfactory. Metabolic alteration, as an important hallmark of cancer cells, not only contributes to the malignant transformation of cells, but also promotes tumor progression and metastasis. As an immune-escape mechanism, the metabolic adaptation of the bone marrow microenvironment and leukemic cells is a major player in the suppression of anti-leukemia immune responses. Therefore, metabolic rewiring in leukemia would provide promising opportunities for newer therapeutic interventions. Several therapeutic agents which affect essential bioenergetic pathways in cancer cells including glycolysis, β-oxidation of fatty acids and Krebs cycle, or anabolic pathways such as lipid biosynthesis and pentose phosphate pathway, are being tested in various types of cancers. So far, numerous preclinical or clinical trial studies using such metabolic agents alone or in combination with other remedies such as immunotherapy are in progress and have demonstrated promising outcomes. In this review, we aim to argue the importance of metabolic alterations and bioenergetic pathways in different types of leukemia and their vital roles in disease development. Designing treatments based on targeting leukemic cells vulnerabilities, particularly in nonresponsive leukemia patients, should be warranted.

Construction of a circular RNA-microRNA-messenger RNA regulatory network of hsa_circ_0043256 in lung cancer by integrated analysis

BACKGROUND

Patients with non-small cell lung cancer (NSCLC) are diagnosed in advanced stages and with a poor 5-year survival rate. There is a critical need to identify novel biomarkers to improve the therapy and overall prognosis of this disease.

METHODS

Differentially expressed genes (DEGs) were identified from three profiles of GSE101586, GSE101684 and GSE112214 using Venn diagrams. hsa_circ_0043256 were validated using quantitative real-time polymerase chain reaction (RT-qPCR). The circular RNA-microRNA-messenger RNA (circRNA-miRNA-mRNA) regulatory network was constructed with Cytoscape 3.7.0. Hub genes were identified with protein interaction (PPI) and validated with the Gene Expression Profiling Interactive Analysis (GEPIA), Human Protein Atlas (HPA) databases, and immunohistochemistry. Survival analyses were also performed using a Kaplan-Meier (KM) plotter. The effects of hsa_circ_0043256 on cell proliferation and cell cycles were evaluated by EdU staining and flow cytometry, respectively.

RESULTS

hsa_circ_0043256, hsa_circ_0029426 and hsa_circ_0049271 were obtained. Following RT-qPCR validation, hsa_circ_0043256 was selected for further analysis. In addition, functional experiment results indicated that hsa_circ_0043256 could inhibit cell proliferation and cell-cycle progression of NSCLC cells in vitro. Prediction by three online databases and combining with DEGs identified from The Cancer Genome Atlas (TCGA), a network containing one circRNAs, three miRNAs, and 209 mRNAs was developed. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated DEGs might be associated with lung cancer onset and progression. A PPI network based on the 209 genes was established, and five hub genes (BIRC5, SHCBP1, CCNA2, SKA3, and GINS1) were determined. Following verification of five hub genes using GEPIA database, HPA database, and immunohistochemistry. High expression of all five hub genes led to poor overall survival.

CONCLUSION

Our study constructed a circRNA-miRNA-mRNA network of hsa_circ_0043256. hsa_circ_0043256 may be a potential therapeutic target for lung cancer.

Review of arginase as a promising biocatalyst: characteristics, preparation, applications and future challenges

As a committed step in the urea cycle, arginase cleaves l-arginine to form l-ornithine and urea. l-Ornithine is essential to: cell proliferation, collagen formation and other physiological functions, while the urea cycle itself converts highly toxic ammonia to urea for excretion. Recently, arginase was exploited as an efficient catalyst for the environmentally friendly synthesis of l-ornithine, an abundant nonprotein amino acid that is widely employed as a food supplement and nutrition product. It was also proposed as an arginine-reducing agent in order to treat arginase deficiency and to be a means of depleting arginine to treat arginine auxotrophic tumors. Targeting arginase inhibitors of the arginase/ornithine pathway offers great promise as a therapy for: cardiovascular, central nervous system diseases and cancers with high arginase expression. In this review, recent advances in the characteristics, structure, catalytic mechanism and preparation of arginase were summarized, with a focus being placed on the biotechnical and medical applications of arginase. In particular, perspectives have been presented on the challenges and opportunities for the environmentally friendly utilization of arginase during l-ornithine production and in therapies.

The prognostic and therapeutic implications of distinct patterns of argininosuccinate synthase 1 (ASS1) and arginase-2 (ARG2) expression by cancer cells and tumor stroma in non-small-cell lung cancer

Background

Arginine (Arg) is essential for cancer cell growth and also for the activation of T cells. Thus, therapies aiming to reduce Arg utilization by cancer may prove detrimental for the immune response.

Methods

We examined the expression of two major enzymes involved in arginine depletion and replenishment, namely arginase ARG2 and argininosuccinate synthase ASS1, respectively, in a series of 98 NSCLCs. Their association with immune infiltrates and the postoperative outcome were also studied.

Results

ARG2 was expressed mainly by cancer-associated fibroblasts (CAFs) (58/98 cases; 59.2%), while ASS1 by cancer cells (75/98 cases; 76.5%). ASS1 and ARG2 expression patterns were not related to hypoxia markers. Auxotrophy, implied by the lack of expression of ASS1 in cancer cells, was associated with high angiogenesis (p < 0.02). ASS1 expression by cancer cells was associated with a high density of iNOS-expressing tumor-infiltrating lymphocytes (^iNOS+TILs). ARG2 expression by CAFs was inversely related to the TIL-density and linked with poorer prognosis (p = 0.02). Patients with ASS1 expression by cancer cells had a better prognosis especially when CAFs did not express ARG2 (p = 0.004).

Conclusions

ARG2 and ASS1 enzymes are extensively expressed in NSCLC stroma and cancer cells, respectively. Auxotrophic tumors have a poor prognosis, potentially by utilizing Arg, thus reducing Arg-dependent TIL anti-tumor activity. ASS1 expression in cancer cells would allow Arg fueling of ^iNOS+TILs and enhance anti-tumor immunity. However, upregulation of ARG2 in CAFs may divert Arg from TILs, allowing immune escape. Identification of these three distinct phenotypes may be useful in the individualization of Arg-targeting therapies and immunotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40170-021-00264-7.

Arginine depriving enzymes: applications as emerging therapeutics in cancer treatment

Cancer is the second leading cause of death globally. Chemotherapy and radiation therapy and other medications are employed to treat various types of cancer. However, each treatment has its own set of side effects, owing to its low specificity. As a result, there is an urgent need for newer therapeutics that do not disrupt healthy cells' normal functioning. Depriving nutrient or non/semi-essential amino acids to which cancerous cells are auxotrophic remains one such promising anticancer strategy. L-Arginine (Arg) is a semi-essential vital amino acid involved in versatile metabolic processes, signaling pathways, and cancer cell proliferation. Hence, the administration of Arg depriving enzymes (ADE) such as arginase, arginine decarboxylase (ADC), and arginine deiminase (ADI) could be effective in cancer therapy. The Arg auxotrophic cancerous cells like hepatocellular carcinoma, human colon cancer, leukemia, and breast cancer cells are sensitive to ADE treatment due to low expression of crucial enzymes argininosuccinate synthetase (ASS), argininosuccinate lyase (ASL), and ornithine transcarbamylase (OCT). These therapeutic enzyme treatments induce cell death through inducing autophagy, apoptosis, generation of oxidative species, i.e., oxidative stress, and arresting the progression and expansion of cancerous cells at certain cell cycle checkpoints. The enzymes are undergoing clinical trials and could be successfully exploited as potential anticancer agents in the future.

Use of Exogenous Enzymes in Human Therapy: Approved Drugs and Potential Applications

The development of safe and efficacious enzyme-based human therapies has increased greatly in the last decades, thanks to remarkable advances in the understanding of the molecular mechanisms responsible for different diseases, and the characterization of the catalytic activity of relevant exogenous enzymes that may play a remedial effect in the treatment of such pathologies. Several enzyme-based biotherapeutics have been approved by FDA (the U.S. Food and Drug Administration) and EMA (the European Medicines Agency) and many are undergoing clinical trials. Apart from enzyme replacement therapy in human genetic diseases, which is not discussed in this review, approved enzymes for human therapy find applications in several fields, from cancer therapy to thrombolysis and the treatment, e.g., of clotting disorders, cystic fibrosis, lactose intolerance and collagen-based disorders. The majority of therapeutic enzymes are of microbial origin, the most convenient source due to fast, simple and cost-effective production and manipulation. The use of microbial recombinant enzymes has broadened prospects for human therapy but some hurdles such as high immunogenicity, protein instability, short half-life and low substrate affinity, still need to be tackled. Alternative sources of enzymes, with reduced side effects and improved activity, as well as genetic modification of the enzymes and novel delivery systems are constantly searched. Chemical modification strategies, targeted- and/or nanocarrier-mediated delivery, directed evolution and site-specific mutagenesis, fusion proteins generated by genetic manipulation are the most explored tools to reduce toxicity and improve bioavailability and cellular targeting. This review provides a description of exogenous enzymes that are presently employed for the therapeutic management of human diseases with their current FDA/EMA-approved status, along with those already experimented at the clinical level and potential promising candidates.

Residual biomass from surfactin production is a source of arginase and adsorbed surfactin that is useful for environmental remediation

Lipopeptides are important secondary metabolites produced by microbes. They find applications in environmental decontamination and in the chemical, pharmaceutical and food industries. However, their production is expensive. In the present work we propose three strategies to lower the production costs of surfactin. First, the coproduction of surfactin and arginase in a single growth. Second, extract the fraction of surfactin that adsorbs to the biomass and is removed from the growth medium through centrifugation. Third, use microbial biomass for the remediation of organic and inorganic contaminants. The coproduction of surfactin and arginase was evaluated by factorial design experiments using the LB medium supplemented with arginine. The best conditions for surfactin production were 22 h of growth at 37 °C using LB supplemented with arginine 7.3 g/L. Almost similar conditions were found to produce highest levels of arginase, 24 h and 6.45 g/L arginine. Decontamination of phenol and copper from artificial samples was attained by treatment with residues from lipopeptide production. Thus, cell suspensions and wash-waters used to extract surfactin from the biomass. Cell suspensions were used to successfully remove hydroquinone. Cell suspensions and wash-waters containing surfactin were successfully used to recover copper from solution. Specific monitoring methods were used for phenol and metal solutions, respectively a biosensor based on tyrosinase and either atomic absorption flame ionization spectrometry or absorbance coupled to the Arduino™ platform. Therefore, we report three alternative strategies to lower the production costs in lipopeptide production, which include the effective recovery of copper and phenol from contaminated waters using residues from surfactin production. Sustainable and profitable production of surfactin can be achieved by a coproduction strategy of lipopeptides and enzymes. Lipopeptides are collected in the supernatant and enzymes in the biomass. In addition, lipopeptides that coprecipitate with biomass can be recovered by washing. Lipopeptide wash-waters find applications in remediation and cells can also be used for environmental decontamination.

The Effects of Quercetin on the Gene Expression of Arginine Metabolism Key Enzymes in Human Embryonic Kidney 293 Cells

Background: Arginine metabolism is an important factor involved in tumorigenesis, progression, and survival of tumor cells. Besides, other metabolites produced in the arginine metabolism process, such as polyamines, nitric oxide, argininosuccinate, and agmatine, play key roles in different stages of tumor development. On the other hand, herbal metabolites are widely used to treat cancer. One of these herbal flavonoids is quercetin. Methods: In this study, according to MTT assay data, two concentrations of quercetin flavonoid were selected (57.5 and 115 µM) to treat human embryonic kidney 293 (HEK293) cells. Then RNA was extracted from the cells and used as a template for cDNA synthesis. Using real-time PCR, the expression of key enzymes involved in arginine metabolism was evaluated, including arginase 2 (Arg2), ornithine carbamoyl transferase (OTC), agmatinase (AGMAT), arginase 1 (Arg1), nitric oxide synthase 1 (nNOS), arginine decarboxylase (ADC), ornithine decarboxylase 1 (ODC), ornithine carbamoyl transferase (OCT), spermidine synthase (SRM), spermine synthase (SMS), argininosuccinate synthase 1 (ASS1), and argininosuccinate lyase (ASL). The Student t-test was used to analyze the data considering a P value of < 0.05 as the significance level. Results: Our results indicated significant changes in the expression of arginine metabolism enzymes after quercetin exposure, confirming a role for quercetin plant flavonoid in regulating arginine metabolism in HEK293 cells. Conclusions: Quercetin could alter the gene expression of the key enzymes involved in arginine metabolism. This was the first study investigating the effects of quercetin on arginine metabolism in HEK293 cells.

Pegylated Recombinant Human Arginase 1 Induces Autophagy and Apoptosis via the ROS-Activated AKT/mTOR Pathway in Bladder Cancer Cells

Bladder cancer is one of the most commonly diagnosed cancers worldwide, especially in males. Current therapeutic interventions, including surgery, radiation therapy, chemotherapy, and immunotherapy, have not been able to improve the clinical outcome of bladder cancer patients with satisfaction. Recombinant human arginase (rhArg, BCT-100) is a novel agent with great anticancer effects on arginine-auxotrophic tumors. However, the effects of BCT-100 on bladder cancer remain unclear. In this study, the in vitro anticancer effects of BCT-100 were assessed using four bladder cancer cell lines (J82, SCaBER, T24, and 5637), while the in vivo effects were evaluated by establishing T24 nude mice xenograft models. Intracellular arginine level was observed to be sharply decreased followed by the onset of apoptotic events. Furthermore, BCT-100 was found to induce H2O2 production and mitochondrial membrane depolarization, leading to the release of mitochondrial cytochrome c and Smac to the cytosol. Treatment with BCT was observed to upregulate the expression of LC3B and Becllin-1, but downregulate the expression of p62 in a time-dependent manner. Autophagic flux was also observed upon BCT-100 treatment. Besides, the phosphorylation of the AKT/mTOR pathway was suppressed in a time-dependent fashion in BCT-100-treated T24 cells. While N-acetyl-L-cysteine was shown to alleviate BCT-100-induced apoptosis and autophagy, chloroquine, MK-2206, and rapamycin were found to potentiate BCT-100-triggered apoptosis. Finally, BCT-100 was demonstrated to induce autophagy and apoptosis via the ROS-mediated AKT/mTOR signaling pathway in bladder cancer cells.

Integrated Metabolomics and Transcriptomics Analysis of Monolayer and Neurospheres from Established Glioblastoma Cell Lines

Simple Summary

Glioblastomas are very aggressive tumours without efficient treatment, where cancer stem-like cells are thought to be responsible for relapse. This pilot study investigated the metabolic discrepancies between monolayer and neurosphere cultures of two glioblastoma cell lines using transcriptomics and metabolomics. We show that the two culture systems display substantial differences regarding their metabolome and transcriptome. Specifically, we found that metabolic reactions connected to arginine biosynthesis are crucial to support the different metabolic needs of neurospheres from the two cell lines. By identifying metabolic vulnerabilities in different glioblastoma subpopulations, new therapeutic strategies may be emerging that can be explored to treat this disease. Moreover, this data set may be of great value as a resource for the scientific community.

Abstract

Altered metabolic processes contribute to carcinogenesis by modulating proliferation, survival and differentiation. Tumours are composed of different cell populations, with cancer stem-like cells being one of the most prominent examples. This specific pool of cells is thought to be responsible for cancer growth and recurrence and plays a particularly relevant role in glioblastoma (GBM), the most lethal form of primary brain tumours. Here, we have analysed the transcriptome and metabolome of an established GBM cell line (U87) and a patient-derived GBM stem-like cell line (NCH644) exposed to neurosphere or monolayer culture conditions. By integrating transcriptome and metabolome data, we identified key metabolic pathways and gene signatures that are associated with stem-like and differentiated states in GBM cells, and demonstrated that neurospheres and monolayer cells differ substantially in their metabolism and gene regulation. Furthermore, arginine biosynthesis was identified as the most significantly regulated pathway in neurospheres, although individual nodes of this pathway were distinctly regulated in the two cellular systems. Neurosphere conditions, as opposed to monolayer conditions, cause a transcriptomic and metabolic rewiring that may be crucial for the regulation of stem-like features, where arginine biosynthesis may be a key metabolic pathway. Additionally, TCGA data from GBM patients showed significant regulation of specific components of the arginine biosynthesis pathway, providing further evidence for the importance of this metabolic pathway in GBM.

Uncovering the Effect of Passage Number on HT29 Cell Line Based on the Cell Metabolomic Approach

The passage number is an important factor when designing the cell line-based experiment. Although HT29 cells were widely used in the laboratory for colorectal cancer studies, the impact of cell passage number on the HT29 cells was still unknown. In this study, phenotypic assay and metabolomic approach were applied to analyze the systemic effects of passage numbers (passage 4, 10, and 16) on the HT29 cells. The results showed that the increased cell passage number affected the cell cycle distribution and also decreased the proliferation and migration ability of HT29 cells. The metabolomic analysis coupled with heatmap and hierarchical cluster analysis showed obvious metabolome difference among the cells with different passage numbers, which was related with 61 differential metabolites. Three metabolic pathways were determined as the key pathways, and arginine participated in two of them. In addition, it was found that arginine supplementation could inhibit the proliferation ability of HT29 cells in vitro, and a synergistic effect existed between arginine and cisplatin. In conclusion, this study not only revealed the influence of passage numbers on the HT29 cell but also provided an important reference that arginine has the potential role to be developed as the cisplatin therapeutic adjuvant.

Intracellular arginine-dependent translation sensor reveals the dynamics of arginine starvation response and resistance in ASS1-negative cells

BACKGROUND

Many cancers silence the metabolic enzyme argininosuccinate synthetase 1 (ASS1), the rate-limiting enzyme for arginine biosynthesis within the urea cycle. Consequently, ASS1-negative cells are susceptible to depletion of extracellular arginine by PEGylated arginine deiminase (ADI-PEG20), an agent currently being developed in clinical trials. As the primary mechanism of resistance to arginine depletion is re-expression of ASS1, we sought a tool to understand the temporal emergence of the resistance phenotype at the single-cell level.

METHODS

A real-time, single-cell florescence biosensor was developed to monitor arginine-dependent protein translation. The versatile, protein-based sensor provides temporal information about the metabolic adaptation of cells, as it is able to quantify and track individual cells over time.

RESULTS

Every ASS1-deficient cell analyzed was found to respond to arginine deprivation by decreased expression of the sensor, indicating an absence of resistance in the naïve cell population. However, the temporal recovery and emergence of resistance varied widely amongst cells, suggesting a heterogeneous metabolic response. The sensor also enabled determination of a minimal arginine concentration required for its optimal translation.

CONCLUSIONS

The translation-dependent sensor developed here is able to accurately track the development of resistance in ASS1-deficient cells treated with ADI-PEG20. Its ability to track single cells over time allowed the determination that resistance is not present in the naïve population, as well as elucidating the heterogeneity of the timing and extent of resistance. This tool represents a useful advance in the study of arginine deprivation, while its design has potential to be adapted to other amino acids.

Metabolic interventions: A new insight into the cancer immunotherapy

Metabolic reprogramming confers cancer cells plasticity and viability under harsh conditions. Such active alterations lead to cell metabolic dependency, which can be exploited as an attractive target in development of effective antitumor therapies. Similar to cancer cells, activated T cells also execute global metabolic reprogramming for their proliferation and effector functions when recruited to the tumor microenvironment (TME). However, the high metabolic activity of rapidly proliferating cancer cells can compete for nutrients with immune cells in the TME, and consequently, suppressing their anti-tumor functions. Thus, therapeutic strategies could aim to restore T cell metabolism and anti-tumor responses in the TME by targeting the metabolic dependence of cancer cells. In this review, we highlight current research progress on metabolic reprogramming and the interplay between cancer cells and immune cells. We also discuss potential therapeutic intervention strategies for targeting metabolic pathways to improve cancer immunotherapy efficacy.

Metabolism of Amino Acids in Cancer

Metabolic reprogramming has been widely recognized as a hallmark of malignancy. The uptake and metabolism of amino acids are aberrantly upregulated in many cancers that display addiction to particular amino acids. Amino acids facilitate the survival and proliferation of cancer cells under genotoxic, oxidative, and nutritional stress. Thus, targeting amino acid metabolism is becoming a potential therapeutic strategy for cancer patients. In this review, we will systematically summarize the recent progress of amino acid metabolism in malignancy and discuss their interconnection with mammalian target of rapamycin complex 1 (mTORC1) signaling, epigenetic modification, tumor growth and immunity, and ferroptosis. Finally, we will highlight the potential therapeutic applications.

Arginine deprivation as a strategy for cancer therapy: An insight into drug design and drug combination

Extensive studies have shown that cancer cells have specific nutrient auxotrophy and thus have much a higher demand for certain nutrients than normal cells. Amino acid deprivation has attracted much attention in cancer therapy with positive outcomes from clinical trials. Arginine, as one of the conditionally essential amino acids, plays a pivotal role in cellular division and metabolism. Since many types of cancer cells exhibit decreased expression of argininosuccinate synthetase and/or ornithine transcarbamylase, they are auxotrophic for arginine, which makes arginine deprivation an accessible choice for cancer treatment. Arginine deiminase (ADI) and human arginase (hArg) are the two major protein drugs used for arginine deprivation and are undergoing many clinical trials. However, the clinical application of ADI and hArg is facing some common problems, including their short half-lives, immunogenicity and inconsistent production, which underlines the importance of improving these drugs using protein engineering techniques. Thus, we systematically review the latest studies of protein engineering and anti-cancer studies based on in vitro, in vivo and clinical models of ADI and hArg, and we include the latest studies on drug combinations consisting of ADI/hArg with chemotherapeutic drugs.

Metabolic regulation of the bone marrow microenvironment in leukemia

Most leukemia patients experience little benefit from immunotherapy, in part due to the immunosuppressive bone marrow microenvironment. Various metabolic mechanisms orchestrate the behaviors of immune cells and leukemia cells in the bone marrow microenvironment. Furthermore, leukemia cells regulate the bone marrow microenvironment through metabolism to generate an adequate supply of energy and to escape antitumor immune surveillance. Thus, the targeting of the interaction between leukemia cells and the bone marrow microenvironment provides a new therapeutic avenue. In this review, we describe the concept of the bone marrow microenvironment and several important metabolic processes of leukemia cells within the bone marrow microenvironment, including carbohydrate, lipid, and amino acid metabolism. In addition, we discuss how these metabolic pathways regulate antitumor immunity and reveal potential therapeutic targets.

Dual role of ER stress in response to metabolic co-targeting and radiosensitivity in head and neck cancer cells

Arginine deprivation therapy (ADT) is a new metabolic targeting approach with high therapeutic potential for various solid cancers. Combination of ADT with low doses of the natural arginine analog canavanine effectively sensitizes malignant cells to irradiation. However, the molecular mechanisms determining the sensitivity of intrinsically non-auxotrophic cancers to arginine deficiency are still poorly understood. We here show for the first time that arginine deficiency is accompanied by global metabolic changes and protein/membrane breakdown, and results in the induction of specific, more or less pronounced (severe vs. mild) ER stress responses in head and neck squamous cell carcinoma (HNSCC) cells that differ in their intrinsic ADT sensitivity. Combination of ADT with canavanine triggered catastrophic ER stress via the eIF2α-ATF4(GADD34)-CHOP pathway, thereby inducing apoptosis; the same signaling arm was irrelevant in ADT-related radiosensitization. The particular strong supra-additive effect of ADT, canavanine and irradiation in both intrinsically more and less sensitive cancer cells supports the rational of ER stress pathways as novel target for improving multi-modal metabolic anti-cancer therapy.

Metabolism of prostate cancer by magnetic resonance spectroscopy (MRS)

Understanding the metabolism of prostate cancer (PCa) is important for developing better diagnostic approaches and also for exploring new therapeutic targets. Magnetic resonance spectroscopy (MRS) techniques have been shown to be useful in the detection and quantification of metabolites. PCa illustrates metabolic phenotype, showing lower levels of citrate (Cit), a key metabolite of oxidative phosphorylation and alteration in several metabolic pathways to sustain tumor growth. Recently, dynamic nuclear polarization (DNP) studies have documented high rates of glycolysis (Warburg phenomenon) in PCa. High-throughput metabolic profiling strategies using MRS on variety of samples including intact tissues, biofluids like prostatic fluid, seminal fluid, blood plasma/sera, and urine have also played a vital role in understanding the abnormal metabolic activity of PCa patients. The enhanced analytical potential of these techniques in the detection and quantification of a large number of metabolites provides an in-depth understanding of metabolic rewiring associated with the tumorigenesis. Metabolomics analysis offers dual advantages of identification of diagnostic and predictive biomarkers as well as in understanding the altered metabolic pathways which can be targeted for inhibiting the cancer progression. This review briefly describes the potential applications of in vivo ¹H MRS, high-resolution magic angle spinning spectroscopy (HRMAS) and in vitro MRS methods in understanding the metabolic changes of PCa and its usefulness in the management of PCa patients.

Integrated proteomics and metabolomics reveals the comprehensive characterization of antitumor mechanism underlying Shikonin on colon cancer patient-derived xenograft model

Colorectal cancer (CRC) is a common malignancy occurring in the digestive system. Despite progress in surgery and therapy options, CRC is still a considerable cause of cancer mortality worldwide. In this study, a colon cancer patient-derived xenograft model was established to evaluate the antitumor activity of Shikonin. The protective effect underlying Shikonin was determined through assessing serum levels of liver enzymes (ALT, AST) and kidney functions (BuN, Scr) in PDX mice. Proteomics and metabolomics profiles were integrated to provide a systematic perspective in dynamic changes of proteins and global endogenous metabolites as well as their perturbed pathways. A total of 456 differently expressed proteins (DEPs), 32 differently expressed metabolites (DEMs) in tumor tissue, and 20 DEMs in mice serum were identified. The perturbation of arginine biosynthesis, purine metabolism, and biosynthesis of amino acids may mainly account for therapeutic mechanism of Shikonin. Furthermore, the expression of mRNAs participating in arginine biosynthesis (CPS1, OTC, Arg1) and do novo purine synthesis (GART, PAICS, ATIC) were validated through RT-qPCR. Our study provides new insights into the drug therapeutic strategies and a better understanding of antitumor mechanisms that might be valuable for further studies on Shikonin in the clinical treatment of colorectal cancer.

Amino Assets: How Amino Acids Support Immunity

Amino acids are fundamental building blocks supporting life. Their role in protein synthesis is well defined, but they contribute to a host of other intracellular metabolic pathways, including ATP generation, nucleotide synthesis, and redox balance, to support cellular and organismal function. Immune cells critically depend on such pathways to acquire energy and biomass and to reprogram their metabolism upon activation to support growth, proliferation, and effector functions. Amino acid metabolism plays a key role in this metabolic rewiring, and it supports various immune cell functions beyond increased protein synthesis. Here, we review the mechanisms by which amino acid metabolism promotes immune cell function, and how these processes could be targeted to improve immunity in pathological conditions.

IFN-γ Activates the TLR4-CCL5 Signaling Through Reducing Arginine Level, Leading to Enhanced Susceptibility of Bovine Mammary Epithelial Cells to Staphylococcus aureus

Dairy cow mastitis is a common bacterial infectious disease which seriously threatens the development of the dairy cow industry. Previous studies have found that increased IFN-γ expression in dairy cows makes dairy cows more susceptible to mastitis, but the underlying mechanism is still not known. In this study, we utilized the in vitro bovine mammary epithelial cells (BMECs) model to explore the molecular mechanism via transcriptome sequencing technology, immunofluorescence, and Western blotting. It was found that IFN-γ promoted the adhesion and invasion of Staphylococcus aureus to BMECs through increasing the expression of TLR4-mediated CCL5 in BMECs. IFN-γ increased the activity of arginase II and reduced the level of arginine in cells, while the addition of arginine inhibited the expression of TLR4 and CCL5. An invasion experiment in mice further validated that IFN-γ treatment significantly increased the bacterial load in mammary glands and blood. However, the colonization and diffusion of S. aureus were interestingly decreased after Arg supplement. These data reveal that increased IFN-γ reduces arginine levels and activates TLR4-CCL5 signaling, leading to enhanced susceptibility of BMECs to S. aureus. Our findings are helpful to understand the pathogenesis of dairy cow mastitis and provide a theoretical basis for improvement of mastitis resistance in dairy cows.

The Molecular Link from Diet to Cancer Cell Metabolism

Malignant cells remodel their metabolism to meet the demands of uncontrolled cell proliferation. These demands lead to differential requirements in energy, biosynthetic precursors, and signaling intermediates. Both genetic programs arising from oncogenic events and transcriptional programs and epigenomic events are important in providing the necessary metabolic network activity. Accumulating evidence has established that environmental factors play a major role in shaping cancer cell metabolism. For metabolism, diet and nutrition are the major environmental aspects and have emerged as key components in determining cancer cell metabolism. In this review, we discuss these emerging concepts in cancer metabolism and how diet and nutrition influence cancer cell metabolism.

Arginine Depletion Therapy with ADI-PEG20 Limits Tumor Growth in Argininosuccinate Synthase-Deficient Ovarian Cancer, Including Small-Cell Carcinoma of the Ovary, Hypercalcemic Type

PURPOSE

Many rare ovarian cancer subtypes, such as small-cell carcinoma of the ovary, hypercalcemic type (SCCOHT), have poor prognosis due to their aggressive nature and resistance to standard platinum- and taxane-based chemotherapy. The development of effective therapeutics has been hindered by the rarity of such tumors. We sought to identify targetable vulnerabilities in rare ovarian cancer subtypes.

EXPERIMENTAL DESIGN

We compared the global proteomic landscape of six cases each of endometrioid ovarian cancer (ENOC), clear cell ovarian cancer (CCOC), and SCCOHT to the most common subtype, high-grade serous ovarian cancer (HGSC), to identify potential therapeutic targets. IHC of tissue microarrays was used as validation of arginosuccinate synthase (ASS1) deficiency. The efficacy of arginine-depriving therapeutic ADI-PEG20 was assessed in vitro using cell lines and patient-derived xenograft mouse models representing SCCOHT.

RESULTS

Global proteomic analysis identified low ASS1 expression in ENOC, CCOC, and SCCOHT compared with HGSC. Low ASS1 levels were validated through IHC in large patient cohorts. The lowest levels of ASS1 were observed in SCCOHT, where ASS1 was absent in 12 of 31 cases, and expressed in less than 5% of the tumor cells in 9 of 31 cases. ASS1-deficient ovarian cancer cells were sensitive to ADI-PEG20 treatment regardless of subtype in vitro. Furthermore, in two cell line mouse xenograft models and one patient-derived mouse xenograft model of SCCOHT, once-a-week treatment with ADI-PEG20 (30 mg/kg and 15 mg/kg) inhibited tumor growth in vivo.

CONCLUSIONS

Preclinical in vitro and in vivo studies identified ADI-PEG20 as a potential therapy for patients with rare ovarian cancers, including SCCOHT.

Inhibition of the polyamine synthesis enzyme ornithine decarboxylase sensitizes triple-negative breast cancer cells to cytotoxic chemotherapy

Treatment of patients with triple-negative breast cancer (TNBC) is limited by a lack of effective molecular therapies targeting this disease. Recent studies have identified metabolic alterations in cancer cells that can be targeted to improve responses to standard-of-care chemotherapy regimens. Using MDA-MB-468 and SUM-159PT TNBC cells, along with LC-MS/MS and HPLC metabolomics profiling, we found here that exposure of TNBC cells to the cytotoxic chemotherapy drugs cisplatin and doxorubicin alter arginine and polyamine metabolites. This alteration was because of a reduction in the levels and activity of a rate-limiting polyamine biosynthetic enzyme, ornithine decarboxylase (ODC). Using gene silencing and inhibitor treatments, we determined that the reduction in ODC was mediated by its negative regulator antizyme, targeting ODC to the proteasome for degradation. Treatment with the ODC inhibitor difluoromethylornithine (DFMO) sensitized TNBC cells to chemotherapy, but this was not observed in receptor-positive breast cancer cells. Moreover, TNBC cell lines had greater sensitivity to single-agent DFMO, and ODC levels were elevated in TNBC patient samples. The alterations in polyamine metabolism in response to chemotherapy, as well as DFMO-induced preferential sensitization of TNBC cells to chemotherapy, reported here suggest that ODC may be a targetable metabolic vulnerability in TNBC.

On interaction of arginine, cysteine and guanine with a nano-TiO2 cluster

Nanoscopic properties of TiO₂ augmented with its physicochemical properties and biocompatibility make it a material interest in the biomedical field. Efficient methods to design of such materials require a thorough understanding of associated nano-bio interfaces. In the present study, density functional theory calculations were performed to study the interactions of arginine, cysteine and guanine with a nano-TiO₂ cluster. Different configurations were sampled for the adsorption of arginine, cysteine and guanine to probe the nano-bio interface via the interaction of various functional groups present on biomolecules. Adsorption energies for arginine, cysteine and guanine were in a range of -25.0 to -57.6, -12.1 to -29.6 and -45.6 to -58.7 kcal/mol, respectively. From the change in adsorption energies and free energies, interaction of amino acids with carboxylic (COOH), thiol (SH) and amine (NH₂) groups while the interaction of the nucleobase via O bonded to C and N of purine ring was found to be essential for thermodynamically stable and energetically favorable states. Density of states analysis also disclosed the prominent interactions of the biomolecules with the nano-TiO₂ cluster. Decrease in band gaps on adsorption of the biomolecules was a pertinent phenomenon indicating the strong chemical interactions of the biomolecules with the nanoscopic TiO₂ chosen for analysis in this study.

Erythrocytes as Carriers: From Drug Delivery to Biosensors

Drug delivery using natural biological carriers, especially erythrocytes, is a rapidly developing field. Such erythrocytes can act as carriers that prolong the drug's action due to its gradual release from the carrier; as bioreactors with encapsulated enzymes performing the necessary reactions, while remaining inaccessible to the immune system and plasma proteases; or as a tool for targeted drug delivery to target organs, primarily to cells of the reticuloendothelial system, liver and spleen. To date, erythrocytes have been studied as carriers for a wide range of drugs, such as enzymes, antibiotics, anti-inflammatory, antiviral drugs, etc., and for diagnostic purposes (e.g. magnetic resonance imaging). The review focuses only on drugs loaded inside erythrocytes, defines the main lines of research for erythrocytes with bioactive substances, as well as the advantages and limitations of their application. Particular attention is paid to in vivo studies, opening-up the potential for the clinical use of drugs encapsulated into erythrocytes.