Cysteine boosters the evolutionary adaptation to CoCl2 mimicked hypoxia conditions, favouring carboplatin resistance in ovarian cancer

Cell-Free DNA (cfDNA) Regulates Metabolic Remodeling in the ES-2 Ovarian Carcinoma Cell Line, Influencing Cell Proliferation, Quiescence, and Chemoresistance in a Cell-of-Origin-Specific Manner

Background: The cell-free DNA (cfDNA) is an extracellular fragmented DNA found in body fluids in physiological and pathophysiological contexts. In cancer, cfDNA has been pointed out as a marker for disease diagnosis, staging, and prognosis; however, little is known about its biological role. Methods: The role of cfDNA released by ES-2 ovarian cancer cells was investigated, along with the impact of glucose bioavailability and culture duration in the cfDNA-induced phenotype. The effect of cfDNA on ES-2 cell proliferation was evaluated by proliferation curves, and cell migration was assessed through wound healing. We explored the impact of different cfDNA variants on ES-2 cells' metabolic profile using nuclear magnetic resonance (NMR) spectroscopy and cisplatin resistance through flow cytometry. Moreover, we assessed the protein levels of DNA-sensitive Toll-like receptor 9 (TLR9) by immunofluorescence and its colocalization with lysosome-associated membrane protein 1 (LAMP1). Results: This study demonstrated that despite inducing similar effects, different variants of cfDNA promote different effects on cells derived from the ES-2 cell line. We observed instant reactions of adopting the metabolic profile that brings back the cell functioning of more favorable culture conditions supporting proliferation and resembling the cell of origin of the cfDNA variant, as observed in unselected ES-2 cells. However, as a long-term selective factor, certain cfDNA variants induced quiescence that favors the chemoresistance of a subset of cancer cells. Conclusions: Therefore, different tumoral microenvironments may generate cfDNA variants that will impact cancer cells differently, orchestrating the disease fate.

Cell-Free DNA (cfDNA) Regulates Metabolic Remodeling, Sustaining Proliferation, Quiescence, and Migration in MDA-MB-231, a Triple-Negative Breast Carcinoma (TNBC) Cell Line

Background: The clinical relevance of circulating cell-free DNA (cfDNA) in oncology has gained significant attention, with its potential as a biomarker for cancer diagnosis and monitoring. However, its precise role in cancer biology and progression remains unclear. cfDNA in cancer patients' blood has been shown to activate signaling pathways, such as those mediated by toll-like receptors (TLRs), suggesting its involvement in cancer cell adaptation to the tumor microenvironment. Methods: This impact of cfDNA released from MDA-MB-231, a triple-negative breast cancer (TNBC) cell line was assessed, focusing on glucose availability and culture duration. The impact of cfDNA on the proliferation of MDA-MB-231 cells was investigated using proliferation curves, while cellular migration was evaluated through wound healing assays. The metabolic alterations induced by distinct cfDNA variants in MDA-MB-231 cells were investigated through nuclear magnetic resonance (NMR) spectroscopy, and their effect on cisplatin resistance was evaluated using flow cytometry. Furthermore, the expression levels of DNA-sensitive Toll-like receptor 9 (TLR9) were quantified via immunofluorescence, alongside its colocalization with lysosome-associated membrane protein 1 (LAMP1). Results: This study indicates that cfDNA facilitates metabolic adaptation, particularly under metabolic stress, by modulating glucose and glutamine consumption, key pathways in tumor cell metabolism. Exposure to cfDNA induced distinct metabolic shifts, favoring energy production through oxidative phosphorylation. The anti-cancer activity of cfDNA isolated from conditioned media of cells cultured under stressful conditions is influenced by the culture duration, emphasizing the importance of adaptation and se-lection in releasing cfDNA that can drive pro-tumoral processes. Additionally, cfDNA exposure influenced cell proliferation, quiescence, and migration, processes linked to metastasis and treatment resistance. These findings underscore cfDNA as a key mediator of metabolic reprogramming and adaptive responses in cancer cells, contributing to tumor progression and therapy resistance. Furthermore, the activation of TLR9 signaling suggests a mechanistic basis for cfDNA-induced phenotypic changes. Conclusions: Overall, cfDNA serves as a crucial signaling molecule in the tumor microenvironment, orchestrating adaptive processes that enhance cancer cell survival and progression.

The unique metabolome of clear cell ovarian carcinoma

Clear cell ovarian carcinoma (CCOC) is an aggressive malignancy affecting younger women. Despite ovarian cancer subtypes having diverse molecular and clinical characteristics, the mainstay of treatment for advanced stage disease remains cytotoxic chemotherapy. Late stage CCOC is resistant to conventional chemotherapy, which means a suboptimal outcome for patients affected. Despite detailed genomic, epigenomic, transcriptomic, and proteomic characterisation, subtype-specific treatment for CCOC has shown little progress. The unique glycogen accumulation defining CCOC suggests altered metabolic pathway activity and dependency. This study presents the first metabolomic landscape of ovarian cancer subtypes, including 42 CCOC, 20 high-grade serous and 21 endometrioid ovarian carcinomas, together comprising the three most common ovarian carcinoma subtypes. We describe a distinct metabolomic landscape of CCOC compared with other ovarian cancer subtypes, including alterations in energy utilisation and cysteine metabolism. In addition, we identify CCOC-specific alterations in metabolic pathways including serine biosynthesis and ROS-associated pathways that could serve as potential therapeutic targets. Our study provides the first in-depth study into the metabolome of ovarian cancers and a rich resource to support ongoing research efforts to identify subtype-specific therapeutic targets that could improve the dismal outcome for patients with this devastating malignancy. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

The microenvironmental factors induced invasive tumor cells in glioblastoma

Glioblastoma (GBM) cells have the potential to switch from being "proliferative cells" to peritumoral "invasive cells". Peritumoral GBM cells have highly invasive properties that allow them to survive surgery, leading to recurrence. The mechanisms underlying the manner in which the tumor microenvironment (TME) regulates the invasiveness of GBM remain unclear. Single-cell RNA sequencing analysis revealed heterogeneity in GBM cells, microglia and macrophages. In this study, the Oncostatin M receptor (OSMR) and leukemia inhibitory factor receptor (LIFR) expression indicated higher invasiveness in core GBM cells. Under environmental stress, the expression of OSMR and LIFR were up-regulated with the effect of hypoxic, acidic, and low-glucose conditions in vitro. Functional experiments revealed that TME stress significantly influences the proliferation, migration and invasion of GBM cells. The differences in core/peripheral TMEs in GBM affected the invasive properties, indicating the significant role of OSMR expression within the TME in tumor progression and postoperative therapy.

Metabolic profiling and combined therapeutic strategies unveil the cytotoxic potential of selenium-chrysin (SeChry) in NSCLC cells

Lung cancer ranks as the predominant cause of cancer-related mortalities on a global scale. Despite progress in therapeutic interventions, encompassing surgical procedures, radiation, chemotherapy, targeted therapies and immunotherapy, the overall prognosis remains unfavorable. Imbalances in redox equilibrium and disrupted redox signaling, common traits in tumors, play crucial roles in malignant progression and treatment resistance. Cancer cells, often characterized by persistent high levels of reactive oxygen species (ROS) resulting from genetic, metabolic, and microenvironmental alterations, counterbalance this by enhancing their antioxidant capacity. Cysteine availability emerges as a critical factor in chemoresistance, shaping the survival dynamics of non-small cell lung cancer (NSCLC) cells. Selenium-chrysin (SeChry) was disclosed as a modulator of cysteine intracellular availability. This study comprehensively characterizes the metabolism of SeChry and investigates its cytotoxic effects in NSCLC. SeChry treatment induces notable metabolic shifts, particularly in selenocompound metabolism, impacting crucial pathways such as glycolysis, gluconeogenesis, the tricarboxylic acid (TCA) cycle, and amino acid metabolism. Additionally, SeChry affects the levels of key metabolites such as acetate, lactate, glucose, and amino acids, contributing to disruptions in redox homeostasis and cellular biosynthesis. The combination of SeChry with other treatments, such as glycolysis inhibition and chemotherapy, results in greater efficacy. Furthermore, by exploiting NSCLC's capacity to consume lactate, the use of lactic acid-conjugated dendrimer nanoparticles for SeChry delivery is investigated, showing specificity to cancer cells expressing monocarboxylate transporters.

The Role of Amino Acids in Non-Enzymatic Antioxidant Mechanisms in Cancer: A Review

Currently, the antioxidant properties of amino acids and their role in the physicochemical processes accompanying oxidative stress in cancer remain unclear. Cancer cells are known to extensively uptake amino acids, which are used as an energy source, antioxidant precursors that reduce oxidative stress in cancer, and as regulators of inhibiting or inducing tumor cell-associated gene expression. This review examines nine amino acids (Cys, His, Phe, Met, Trp, Tyr, Pro, Arg, Lys), which play a key role in the non-enzymatic oxidative process in various cancers. Conventionally, these amino acids can be divided into two groups, in one of which the activity increases (Cys, Phe, Met, Pro, Arg, Lys) in cancer, and in the other, it decreases (His, Trp, Tyr). The review examines changes in the metabolism of nine amino acids in eleven types of oncology. We have identified the main nonspecific mechanisms of changes in the metabolic activity of amino acids, and described direct and indirect effects on the redox homeostasis of cells. In the future, this will help to understand better the nature of life of a cancer cell and identify therapeutic targets more effectively.

H2S-Synthesizing Enzymes Are Putative Determinants in Lung Cancer Management toward Personalized Medicine

Lung cancer is a lethal disease with no truly efficient therapeutic management despite the progresses, and metabolic profiling can be a way of stratifying patients who may benefit from new therapies. The present study is dedicated to profiling cysteine metabolic pathways in NSCLC cell lines and tumor samples. This was carried out by analyzing hydrogen sulfide (H2S) and ATP levels, examining mRNA and protein expression patterns of cysteine catabolic enzymes and transporters, and conducting metabolomics analysis using nuclear magnetic resonance (NMR) spectroscopy. Selenium-chrysin (SeChry) was tested as a therapeutic alternative with the aim of having an effect on cysteine catabolism and showed promising results. NSCLC cell lines presented different cysteine metabolic patterns, with A549 and H292 presenting a higher reliance on cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) to maintain H2S levels, while the PC-9 cell line presented an adaptive behavior based on the use of mercaptopyruvate sulfurtransferase (MST) and cysteine dioxygenase (CDO1), both contributing to the role of cysteine as a pyruvate source. The analyses of human lung tumor samples corroborated this variability in profiles, meaning that the expression of certain genes may be informative in defining prognosis and new targets. Heterogeneity points out individual profiles, and the identification of new targets among metabolic players is a step forward in cancer management toward personalized medicine.

SIRT5 Activation and Inorganic Phosphate Binding Reduce Cancer Cell Vitality by Modulating Autophagy/Mitophagy and ROS

Cancer cells show increased glutamine consumption. The glutaminase (GLS) enzyme controls a limiting step in glutamine catabolism. Breast tumors, especially the triple-negative subtype, have a high expression of GLS. Our recent study demonstrated that GLS activity and ammonia production are inhibited by sirtuin 5 (SIRT5). We developed MC3138, a selective SIRT5 activator. Treatment with MC3138 mimicked the deacetylation effect mediated by SIRT5 overexpression. Moreover, GLS activity was regulated by inorganic phosphate (Pi). Considering the interconnected roles of GLS, SIRT5 and Pi in cancer growth, our hypothesis is that activation of SIRT5 and reduction in Pi could represent a valid antitumoral strategy. Treating cells with MC3138 and lanthanum acetate, a Pi chelator, decreased cell viability and clonogenicity. We also observed a modulation of MAP1LC3B and ULK1 with MC3138 and lanthanum acetate. Interestingly, inhibition of the mitophagy marker BNIP3 was observed only in the presence of MC3138. Autophagy and mitophagy modulation were accompanied by an increase in cytosolic and mitochondrial reactive oxygen species (ROS). In conclusion, our results show how SIRT5 activation and/or Pi binding can represent a valid strategy to inhibit cell proliferation by reducing glutamine metabolism and mitophagy, leading to a deleterious accumulation of ROS.

The versatile utility of cysteine as a target for cancer treatment

Owing to its unique nucleophilicity, cysteine is an attractive sulfhydryl-containing proteinogenic amino acid. It is also utilized in various metabolic pathways and redox homeostasis, as it is used for the component of major endogenous antioxidant glutathione and the generation of sulfur-containing biomolecules. In addition, cysteine is the most nucleophilic amino acid of proteins and can react with endogenous or exogenous electrophiles which can result in the formation of covalent bonds, which can alter the cellular states and functions. Moreover, post-translational modifications of cysteines trigger redox signaling and affect the three-dimensional protein structure. Protein phosphorylation mediated by kinases and phosphatases play a key role in cellular signaling that regulates many physiological and pathological processes, and consequently, the modification of cysteine regulates its activities. The modification of cysteine residues in proteins is critically important for the design of novel types of pharmacological agents. Therefore, in cancer metabolism and cancer cell survival, cysteine plays an essential role in redox regulation of cellular status and protein function. This review summarizes the diverse regulatory mechanisms of cysteine bound to or free from proteins in cancer. Furthermore, it can enhance the comprehension of the role of cysteine in tumor biology which can help in the development of novel effective cancer therapies.

Exploring Metabolic Signatures of Ex Vivo Tumor Tissue Cultures for Prediction of Chemosensitivity in Ovarian Cancer

Simple Summary

Women diagnosed with ovarian cancer have 5-year survival rates below 45%. Prediction of patient’s outcome and the onset of drug resistance are still major challenges. The patient’s drug response is influenced by the environment that surrounds the tumor cells. We previously showed that patient-derived tumor tissue can be kept in the lab, alive and retaining aspects of that environment. In this study, we exposed tumor tissue derived from ovarian cancer patients to the chemotherapy patients receive and identified metabolites released by the tumor tissue after treatment (metabolic footprint). Using machine learning, we uncovered metabolic signatures that discriminate tumor tissues with higher vs. lower drug sensitivity. We propose potential biomarkers involved in the production of specific building blocks of cells and energy generation processes. Overall, we established a platform to explore metabolic features of the complex environment of each patient’s tumor that can underpin the discovery of biomarkers of drug response.

Abstract

Predicting patient response to treatment and the onset of chemoresistance are still major challenges in oncology. Chemoresistance is deeply influenced by the complex cellular interactions occurring within the tumor microenvironment (TME), including metabolic crosstalk. We have previously shown that ex vivo tumor tissue cultures derived from ovarian carcinoma (OvC) resections retain the TME components for at least four weeks of culture and implemented assays for assessment of drug response. Here, we explored ex vivo patient-derived tumor tissue cultures to uncover metabolic signatures of chemosensitivity and/or resistance. Tissue cultures derived from nine OvC cases were challenged with carboplatin and paclitaxel, the standard-of-care chemotherapeutics, and the metabolic footprints were characterized by LC-MS. Partial least-squares discriminant analysis (PLS-DA) revealed metabolic signatures that discriminated high-responder from low-responder tissue cultures to ex vivo drug exposure. As a proof-of-concept, a set of potential metabolic biomarkers of drug response was identified based on the receiver operating characteristics (ROC) curve, comprising amino acids, fatty acids, pyrimidine, glutathione, and TCA cycle pathways. Overall, this work establishes an analytical and computational platform to explore metabolic features of the TME associated with response to treatment, which can leverage the discovery of biomarkers of drug response and resistance in OvC.

Cysteine Boosts Fitness Under Hypoxia-Mimicked Conditions in Ovarian Cancer by Metabolic Reprogramming

Among gynecologic malignancies, ovarian cancer is the third most prevalent and the most common cause of death, especially due to diagnosis at an advanced stage together with resistance to therapy. As a solid tumor grows, cancer cells in the microenvironment are exposed to regions of hypoxia, a selective pressure prompting tumor progression and chemoresistance. We have previously shown that cysteine contributes to the adaptation to this hypoxic microenvironment, but the mechanisms by which cysteine protects ovarian cancer cells from hypoxia-induced death are still to be unveiled. Herein, we hypothesized that cysteine contribution relies on cellular metabolism reprogramming and energy production, being cysteine itself a metabolic source. Our results strongly supported a role of xCT symporter in energy production that requires cysteine metabolism instead of hydrogen sulfide (H2S) per se. Cysteine degradation depends on the action of the H2S-synthesizing enzymes cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), and/or 3-mercaptopyruvate sulfurtransferase (MpST; together with cysteine aminotransferase, CAT). In normoxia, CBS and CSE inhibition had a mild impact on cysteine-sustained ATP production, pointing out the relevance of CAT + MpST pathway. However, in hypoxia, the concomitant inhibition of CBS and CSE had a stronger impact on ATP synthesis, thus also supporting a role of their hydrogen sulfide and/or cysteine persulfide-synthesizing activity in this stressful condition. However, the relative contributions of each of these enzymes (CBS/CSE/MpST) on cysteine-derived ATP synthesis under hypoxia remains unclear, due to the lack of specific inhibitors. Strikingly, NMR analysis strongly supported a role of cysteine in the whole cellular metabolism rewiring under hypoxia. Additionally, the use of cysteine to supply biosynthesis and bioenergetics was reinforced, bringing cysteine to the plateau of a main carbon sources in cancer. Collectively, this work supports that sulfur and carbon metabolism reprogramming underlies the adaptation to hypoxic microenvironment promoted by cysteine in ovarian cancer.

Hypoxia-Mediated Decrease of Ovarian Cancer Cells Reaction to Treatment: Significance for Chemo- and Immunotherapies

Hypoxia, a common factor ruling the microenvironment composition, leads to tumor progression. In this hypoxic context, cytokines and cells cooperate to favor cancer development and metastasis. Tumor hypoxia is heterogeneously distributed. Oxygen gradients depend on the vicinity, functionality of blood vessels, and oxygen ability to diffuse into surrounding tissues. Thus, the vasculature state modulates the microenvironment of the tumor cells. Cells sense and react to small variations in oxygen tension, which explains the lack of tumor cells’ unicity in their reaction to drugs. Ovarian cancers are highly hypoxia-dependent, ascites worsening the access to oxygen, in their reactions to both chemotherapy and new immunotherapy. Consequently, hypoxia affects the results of immunotherapy, and is thus, crucial for the design of treatments. Controlling key immunosuppressive factors and receptors, as well as immune checkpoint molecule expression on tumor, immune and stromal cells, hypoxia induces immunosuppression. Consequently, new approaches to alleviate hypoxia in the tumor microenvironment bring promises for ovarian cancer immunotherapeutic strategies. This review focuses on the effects of hypoxia in the microenvironment and its consequences on tumor treatments. This opens the way to innovative combined treatments to the advantage of immunotherapy outcome in ovarian cancers.

Transcription factors in epithelial ovarian cancer: histotype-specific drivers and novel therapeutic targets

Transcription factors (TFs) are major contributors to cancer risk and somatic development. In preclinical and clinical studies, direct or indirect inhibition of TF-mediated oncogenic gene expression profiles have proven to be effective in many tumor types, highlighting this group of proteins as valuable therapeutic targets. In spite of this, our understanding of TFs in epithelial ovarian cancer (EOC) is relatively limited. EOC is a heterogeneous disease composed of five major histologic subtypes; high-grade serous, low-grade serous, endometrioid, clear cell and mucinous. Each histology is associated with unique clinical etiologies, sensitivity to therapies, and molecular signatures - including diverse transcriptional regulatory programs. While some TFs are shared across EOC subtypes, a set of TFs are expressed in a histotype-specific manner and likely explain part of the histologic diversity of EOC subtypes. Targeting TFs present with unique opportunities for development of novel precision medicine strategies for ovarian cancer. This article reviews the critical TFs in EOC subtypes and highlights the potential of exploiting TFs as biomarkers and therapeutic targets.

Take Advantage of Glutamine Anaplerosis, the Kernel of the Metabolic Rewiring in Malignant Gliomas

Glutamine is a non-essential amino acid that plays a key role in the metabolism of proliferating cells including neoplastic cells. In the central nervous system (CNS), glutamine metabolism is particularly relevant, because the glutamine-glutamate cycle is a way of controlling the production of glutamate-derived neurotransmitters by tightly regulating the bioavailability of the amino acids in a neuron-astrocyte metabolic symbiosis-dependent manner. Glutamine-related metabolic adjustments have been reported in several CNS malignancies including malignant gliomas that are considered ‘glutamine addicted’. In these tumors, glutamine becomes an essential amino acid preferentially used in energy and biomass production including glutathione (GSH) generation, which is crucial in oxidative stress control. Therefore, in this review, we will highlight the metabolic remodeling that gliomas undergo, focusing on glutamine metabolism. We will address some therapeutic regimens including novel research attempts to target glutamine metabolism and a brief update of diagnosis strategies that take advantage of this altered profile. A better understanding of malignant glioma cell metabolism will help in the identification of new molecular targets and the design of new therapies.

Cysteine Aminotransferase (CAT): A Pivotal Sponsor in Metabolic Remodeling and an Ally of 3-Mercaptopyruvate Sulfurtransferase (MST) in Cancer

Metabolic remodeling is a critical skill of malignant cells, allowing their survival and spread. The metabolic dynamics and adaptation capacity of cancer cells allow them to escape from damaging stimuli, including breakage or cross-links in DNA strands and increased reactive oxygen species (ROS) levels, promoting resistance to currently available therapies, such as alkylating or oxidative agents. Therefore, it is essential to understand how metabolic pathways and the corresponding enzymatic systems can impact on tumor behavior. Cysteine aminotransferase (CAT) per se, as well as a component of the CAT: 3-mercaptopyruvate sulfurtransferase (MST) axis, is pivotal for this metabolic rewiring, constituting a central mechanism in amino acid metabolism and fulfilling the metabolic needs of cancer cells, thereby supplying other different pathways. In this review, we explore the current state-of-art on CAT function and its role on cancer cell metabolic rewiring as MST partner, and its relevance in cancer cells' fitness.

BNIP3-mediated Autophagy Induced Inflammatory Response and Inhibited VEGF Expression in Cultured Retinal Pigment Epithelium Cells Under Hypoxia

BACKGROUND

Bcl-2/adenovirus E1B-19kDa-interacting protein (BNIP3), an important target of hypoxia-inducible factors-1 alpha (HIF-1α), was reported to be overexpressed under hypoxic condition. Our previous study demonstrated the protective effect on detached retina by BNIP3-mediated autophagy. The study investigated the role of BNIP3-mediated autophagy in retinal pigment epithelial (RPE) cells under hypoxia, and observed the relationship between BNIP3, vascular endothelial growth factor (VEGF) and inflammatory response in hypoxic RPE cells.

METHODS

BNIP3 knock down in retinal pigment epithelial cells was performed by small interfering RNA (siRNA) technology in ARPE-19 cells, a human RPE cell line. Both control and BNIP3-knockdown ARPE-19 cells were then subjected to a hypoxic challenge using cobalt (II) chloride (CoCl2). The expression of autophagy-related genes, VEGF and inflammatory factors (IL-18, IL-8, MMP-2, MMP-9, NLRP3, TNF-α) in RPE cells was examined using quantitative Polymerase Chain Reaction (qPCR). The protein levels of HIF-1α, BNIP3, the maker proteins (ATG5, LC3,p62, Beclin-1) of autophagy and the component proteins (p-p70S6K, p70S6K, mTOR, p-mTOR) of the mTORC1 pathway were analyzed by Western blot. BNIP3 subcellualr localization was detected by immunofluorescence. Cell viability was measured with Cell Counting kit-8. Cell apoptosis was examined by TUNEL staining and caspase-3 activity assay.

RESULTS

The expression levels of BNIP3, HIF-1α and marker genes of autophagy were upregulated in ARPE-19 cells in response to hypoxia. Importantly, hypoxia-induced autophagy was mediated by the mTORC1 pathway, and was blocked upon BNIP3 knockdown. Additionally, hypoxia reduced cell viability, which was relieved by an mTORC1 inhibitor. Also, autophagy protected ARPE-19 cells from CoCl2-induced cell apoptosis. Moreover, inhibition of autophagy upregulated the expression of VEGF and IL-18, and downregulated the expression of other inflammatory factors in the hypoxic ARPE-19 cells.

CONCLUSION

BNIP3-mediated autophagy under hypoxia is involved in regulating inflammatory response and VEGF expression, which consequently affects the cell viability of RPE cells.

Metabolic Reprogramming of Chemoresistant Cancer Cells and the Potential Significance of Metabolic Regulation in the Reversal of Cancer Chemoresistance

Metabolic reprogramming is one of the hallmarks of tumors. Alterations of cellular metabolism not only contribute to tumor development, but also mediate the resistance of tumor cells to antitumor drugs. The metabolic response of tumor cells to various chemotherapy drugs can be analyzed by metabolomics. Although cancer cells have experienced metabolic reprogramming, the metabolism of drug resistant cancer cells has been further modified. Metabolic adaptations of drug resistant cells to chemotherapeutics involve redox, lipid metabolism, bioenergetics, glycolysis, polyamine synthesis and so on. The proposed metabolic mechanisms of drug resistance include the increase of glucose and glutamine demand, active pathways of glutaminolysis and glycolysis, promotion of NADPH from the pentose phosphate pathway, adaptive mitochondrial reprogramming, activation of fatty acid oxidation, and up-regulation of ornithine decarboxylase for polyamine production. Several genes are associated with metabolic reprogramming and drug resistance. Intervening regulatory points described above or targeting key genes in several important metabolic pathways may restore cell sensitivity to chemotherapy. This paper reviews the metabolic changes of tumor cells during the development of chemoresistance and discusses the potential of reversing chemoresistance by metabolic regulation.

Cysteine as a Carbon Source, a Hot Spot in Cancer Cells Survival

Cancer cells undergo a metabolic rewiring in order to fulfill the energy and biomass requirements. Cysteine is a pivotal organic compound that contributes for cancer metabolic remodeling at three different levels: (1) in redox control, free or as a component of glutathione; (2) in ATP production, via hydrogen sulfide (H₂S) production, serving as a donor to electron transport chain (ETC), and (3) as a carbon source for biomass and energy production. In the present review, emphasis will be given to the role of cysteine as a carbon source, focusing on the metabolic reliance on cysteine, benefiting the metabolic fitness and survival of cancer cells. Therefore, the interplay between cysteine metabolism and other metabolic pathways, as well as the regulation of cysteine metabolism related enzymes and transporters, will be also addressed. Finally, the usefulness of cysteine metabolic route as a target in cancer treatment will be highlighted.

Polyurea Dendrimer Folate-Targeted Nanodelivery of l-Buthionine sulfoximine as a Tool to Tackle Ovarian Cancer Chemoresistance

: Ovarian cancer is a highly lethal disease, mainly due to chemoresistance. Our previous studies on metabolic remodeling in ovarian cancer have supported that the reliance on glutathione (GSH) bioavailability is a main adaptive metabolic mechanism, also accounting for chemoresistance to conventional therapy based on platinum salts. In this study, we tested the effects of the in vitro inhibition of GSH synthesis on the restoration of ovarian cancer cells sensitivity to carboplatin. GSH synthesis was inhibited by exposing cells to l-buthionine sulfoximine (l-BSO), an inhibitor of -glutamylcysteine ligase (GCL). Given the systemic toxicity of l-BSO, we developed a new formulation using polyurea (PURE) dendrimers nanoparticles (l-BSO@PURE_G4-FA₂), targeting l-BSO delivery in a folate functionalized nanoparticle.

Metabolic Remodeling as a Way of Adapting to Tumor Microenvironment (TME), a Job of Several Holders

The microenvironment depends and generates dependence on all the cells and structures that share the same niche, the biotope. The contemporaneous view of the tumor microenvironment (TME) agrees with this idea. The cells that make up the tumor, whether malignant or not, behave similarly to classes of elements within a living community. These elements inhabit, modify and benefit from all the facilities the microenvironment has to offer and that will contribute to the survival and growth of the tumor and the progression of the disease.The metabolic adaptation to microenvironment is a crucial process conducting to an established tumor able to grow locally, invade and metastasized. The metastatic cancer cells are reasonable more plastic than non-metastatic cancer cells, because the previous ones must survive in the microenvironment where the primary tumor develops and in addition, they must prosper in the microenvironment in the metastasized organ.The metabolic remodeling requires not only the adjustment of metabolic pathways per se but also the readjustment of signaling pathways that will receive and obey to the extracellular instructions, commanding the metabolic adaptation. Many diverse players are pivotal in cancer metabolic fitness from the initial signaling stimuli, going through the activation or repression of genes, until the phenotype display. The new phenotype will permit the import and consumption of organic compounds, useful for energy and biomass production, and the export of metabolic products that are useless or must be secreted for a further recycling or controlled uptake. In the metabolic network, three subsets of players are pivotal: (1) the organic compounds; (2) the transmembrane transporters, and (3) the enzymes.This chapter will present the "Pharaonic" intent of diagraming the interplay between these three elements in an attempt of simplifying and, at the same time, of showing the complex sight of cancer metabolism, addressing the orchestrating role of microenvironment and highlighting the influence of non-cancerous cells.

Monocytes as Endothelial Progenitor Cells (EPCs), Another Brick in the Wall to Disentangle Tumor Angiogenesis

Bone marrow contains endothelial progenitor cells (EPCs) that, upon pro-angiogenic stimuli, migrate and differentiate into endothelial cells (ECs) and contribute to re-endothelialization and neo-vascularization. There are currently no reliable markers to characterize EPCs, leading to their inaccurate identification. In the past, we showed that, in a panel of tumors, some cells on the vessel wall co-expressed CD14 (monocytic marker) and CD31 (EC marker), indicating a putative differentiation route of monocytes into ECs. Herein, we disclosed monocytes as potential EPCs, using in vitro and in vivo models, and also addressed the cancer context. Monocytes acquired the capacity to express ECs markers and were able to be incorporated into blood vessels, contributing to cancer progression, by being incorporated in tumor neo-vasculature. Reactive oxygen species (ROS) push monocytes to EC differentiation, and this phenotype is reverted by cysteine (a scavenger and precursor of glutathione), which indicates that angiogenesis is controlled by the interplay between the oxidative stress and the scavenging capacity of the tumor microenvironment.

Targeting Glutathione and Cystathionine β-Synthase in Ovarian Cancer Treatment by Selenium-Chrysin Polyurea Dendrimer Nanoformulation

Ovarian cancer is the main cause of death from gynecological cancer, with its poor prognosis mainly related to late diagnosis and chemoresistance (acquired or intrinsic) to conventional alkylating and reactive oxygen species (ROS)-generating drugs. We and others reported that the availability of cysteine and glutathione (GSH) impacts the mechanisms of resistance to carboplatin in ovarian cancer. Different players in cysteine metabolism can be crucial in chemoresistance, such as the cystine/glutamate antiporter system Xc (xCT) and the H2S-synthesizing enzyme cystathionine β-synthase (CBS) in the pathway of cysteine catabolism. We hypothesized that, by disrupting cysteine metabolic flux, chemoresistance would be reverted. Since the xCT transporter is also able to take up selenium, we used selenium-containing chrysin (SeChry) as a plausible competitive inhibitor of xCT. For that, we tested the effects of SeChry on three different ovarian cancer cell lines (ES2, OVCAR3, and OVCAR8) and in two non-malignant cell lines (HaCaT and HK2). Results showed that, in addition to being highly cytotoxic, SeChry does not affect the uptake of cysteine, although it increases GSH depletion, indicating that SeChry might induce oxidative stress. However, enzymatic assays revealed an inhibitory effect of SeChry toward CBS, thus preventing production of the antioxidant H2S. Notably, our data showed that SeChry and folate-targeted polyurea dendrimer generation four (SeChry@PUREG4-FA) nanoparticles increased the specificity for SeChry delivery to ovarian cancer cells, reducing significantly the toxicity against non-malignant cells. Collectively, our data support SeChry@PUREG4-FA nanoparticles as a targeted strategy to improve ovarian cancer treatment, where GSH depletion and CBS inhibition underlie SeChry cytotoxicity.

Glutathione in Ovarian Cancer: A Double-Edged Sword

Glutathione (GSH) has several roles in a cell, such as a reactive oxygen species (ROS) scavenger, an intervenient in xenobiotics metabolism and a reservoir of cysteine. All of these activities are important in the maintenance of normal cells homeostasis but can also constitute an advantage for cancer cells, allowing disease progression and resistance to therapy. Ovarian cancer is the major cause of death from gynaecologic disease and the second most common gynaecologic malignancy worldwide. In over 50 years, the overall survival of patients diagnosed with epithelial ovarian cancer has not changed, regardless of the efforts concerning early detection, radical surgery and new therapeutic approaches. Late diagnosis and resistance to therapy are the main causes of this outcome, and GSH is profoundly associated with chemoresistance to platinum salts, which, together with taxane-based chemotherapy and surgery, are the main therapy strategies in ovarian cancer treatment. Herein, we present some insights into the role of GSH in the poor prognosis of ovarian cancer, and also point out how some strategies underlying the dependence of ovarian cancer cells on GSH can be further used to improve the effectiveness of therapy.

Administration of CoCl2 Improves Functional Recovery in a Rat Model of Sciatic Nerve Transection Injury

Peripheral nerve injury is known to activate the hypoxia-inducible factor-1α (HIF-1α) pathway as one of pro-regenerative transcriptional programs, which could stimulate multiple injury-induced gene expression and contribute to axon regeneration and functional recovery. However, the role of HIF-1α in peripheral nerve regeneration remains to be fully elucidated. In this study, rats were divided into three groups and treated with sham surgery, surgery with cobalt chloride (CoCl₂) and surgery with saline, respectively. Sciatic functional index, morphologic evaluations of muscle fibers, and never conduction velocity were performed to measure the functional recovery at 12 weeks postoperatively. In addition, the effects of CoCl₂ on the expression of HIF-1α, glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) were determined at mRNA levels; as well as HIF-1α, the dual leucine zipper kinase (DLK), the c-Jun N-terminal kinase (JNK), phosphorylated JNK (p-JNK), BDNF and NGF were measured at protein level at 4 weeks postoperatively. Systemic administration of CoCl₂ (15 mg/kg/day intraperitoneally) significantly promoted functional recovery of rats with sciatic nerve transection injury. This study demonstrated in rats treated with CoCl₂, the expression of HIF-1α, GDNF, BDNF and NGF was significantly increased at mRNA level, while HIF-1α, DLK, p-JNK, BDNF and NGF was significantly increased at protein level.