Dynamic Imaging of LDH Inhibition in Tumors Reveals Rapid In Vivo Metabolic Rewiring and Vulnerability to Combination Therapy

Synthesis and biological characterization of an orally bioavailable lactate dehydrogenase-A inhibitor against pancreatic cancer

Lactate dehydrogenase-A (LDHA) is the major isoform of lactate dehydrogenases (LDH) that is overexpressed and linked to poor survival in pancreatic ductal adenocarcinoma (PDAC). Despite some progress, current LDH inhibitors have poor structural and physicochemical properties or exhibit unfavorable pharmacokinetics that have hampered their development. The present study reports the synthesis and biological evaluation of a novel class of LDHA inhibitors comprising a succinic acid monoamide motif. Compounds 6 and 21 are structurally related analogs that demonstrated potent inhibition of LDHA with IC50s of 46 nM and 72 nM, respectively. We solved cocrystal structures of compound 21-bound to LDHA that showed that the compound binds to a distinct allosteric site between the two subunits of the LDHA tetramer. Inhibition of LDHA correlated with reduced lactate production and reduction of glycolysis in MIA PaCa-2 pancreatic cancer cells. The lead compounds inhibit the proliferation of human pancreatic cancer cell lines and patient-derived 3D organoids and exhibit a synergistic cytotoxic effect with the OXPHOS inhibitor phenformin. Unlike current LDHA inhibitors, 6 and 21 have appropriate pharmacokinetics and ligand efficiency metrics, exhibit up to 73% oral bioavailability, and a cumulative half-life greater than 4 h in mice.

Cancer cell metabolism and antitumour immunity

Accumulating evidence suggests that metabolic rewiring in malignant cells supports tumour progression not only by providing cancer cells with increased proliferative potential and an improved ability to adapt to adverse microenvironmental conditions but also by favouring the evasion of natural and therapy-driven antitumour immune responses. Here, we review cancer cell-intrinsic and cancer cell-extrinsic mechanisms through which alterations of metabolism in malignant cells interfere with innate and adaptive immune functions in support of accelerated disease progression. Further, we discuss the potential of targeting such alterations to enhance anticancer immunity for therapeutic purposes.

Tumor Metabolism: A New Field for the Treatment of Glioma

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

Deregulation of lactate permeability using a small-molecule transporter (Lactrans-1) disturbs intracellular pH and triggers cancer cell death

Due to the relevance of lactic acidosis in cancer, several therapeutic strategies have been developed targeting its production and/or regulation. In this matter, inhibition approaches of key proteins such as lactate dehydrogenase or monocarboxylate transporters have showed promising results, however, metabolic plasticity and tumor heterogeneity limits their efficacy. In this study, we explored the anticancer potential of a new strategy based on disturbing lactate permeability independently of monocarboxylate transporters activity using a small molecule ionophore named Lactrans-1. Derived from click-tambjamines, Lactrans-1 facilitates transmembrane lactate transportation in liposome models and reduces cancer cell viability. The results showed that Lactrans-1 triggered both apoptosis and necrosis depending on the cell line tested, displaying a synergistic effect in combination with first-line standard chemotherapeutic cisplatin. The ability of this compound to transport outward lactate anions was confirmed in A549 and HeLa cells, two cancer cell lines having distinct rates of lactate production. In addition, through cell viability reversion experiments it was possible to establish a correlation between the amount of lactate transported and the cytotoxic effect exhibited. The movement of lactate anions was accompanied with intracellular pH disturbances that included basification of lysosomes and acidification of the cytosol and mitochondria. We also observed mitochondrial swelling, increased ROS production and activation of oxidative stress signaling pathways p38-MAPK and JNK/SAPK. Our findings provide evidence that enhancement of lactate permeability is critical for cellular pH homeostasis and effective to trigger cancer cell death, suggesting that Lactrans-1 may be a promising anticancer therapy.

Exploring the therapeutic potential of rutin through investigating its inhibitory mechanism on lactate dehydrogenase: Multi-spectral methods and computer simulation

Lactate dehydrogenase (LDH), a crucial enzyme in anaerobic glycolysis, plays a pivotal role in the energy metabolism of tumor cells, positioning it as a promising target for tumor treatment. Rutin, a plant-based flavonoid, offers benefits like antioxidant, antiapoptotic, and antineoplastic effects. This study employed diverse experiments to investigate the inhibitory mechanism of rutin on LDH through a binding perspective. The outcomes revealed that rutin underwent spontaneous binding within the coenzyme binding site of LDH, leading to the formation of a stable binary complex driven by hydrophobic forces, with hydrogen bonds also contributing significantly to sustaining the stability of the LDH-rutin complex. The binding constant (Ka) for the LDH-rutin system was 2.692 ± 0.015 × 104 M-1 at 298 K. Furthermore, rutin induced the alterations in the secondary structure conformation of LDH, characterized by a decrease in α-helix and an increase in antiparallel and parallel β-sheet, and β-turn. Rutin augmented the stability of coenzyme binding to LDH, which could potentially hinder the conversion process among coenzymes. Specifically, Arg98 in the active site loop of LDH provided essential binding energy contribution in the binding process. These outcomes might explain the dose-dependent inhibition of the catalytic activity of LDH by rutin. Interestingly, both the food additives ascorbic acid and tetrahydrocurcumin could reduce the binding stability of LDH and rutin. Meanwhile, these food additives did not produce positive synergism or antagonism on the rutin binding to LDH. Overall, this research could offer a unique insight into the therapeutic potential and medicinal worth of rutin.

Real-Time Monitoring of Hydrolysis Reactions of Pyrophosphates with Dissolution Dynamic Nuclear Polarization

Dissolution dynamic nuclear polarization (d-DNP) has enabled applications such as the real-time monitoring of chemical reactions. Such applications are mainly for 13C and 15N spins with long spin-lattice relaxation times in the molecules of interest. However, the only applications for phosphorus using d-DNP are pH imaging and nucleation during crystallization due to the short relaxation times. Here we show that it is possible to observe enzyme reactions using d-DNP with phosphorus. Hyperpolarized 31P spins in pyrophosphate were obtained using bullet-DNP, which requires less dilution of highly polarized solid samples. Real-time monitoring of the hydrolysis reaction of pyrophosphate by inorganic pyrophosphatase from baker's yeast at physiological pH and was successfully achieved and the reaction rate was determined. This is an important reaction for a wide range of applications related to medicine, agriculture, and quantum life science.

Lactic acid in macrophage polarization: A factor in carcinogenesis and a promising target for cancer therapy

Cancer remains a formidable challenge, continually revealing its intricate nature and demanding novel treatment approaches. Within this intricate landscape, the tumor microenvironment and its dynamic components have gained prominence, particularly macrophages that can adopt diverse polarization states, exerting a profound influence on cancer progression. Recent revelations have spotlighted lactic acid as a pivotal player in this complex interplay. This review systematically explores lactic acid's multifaceted role in macrophage polarization, focusing on its implications in carcinogenesis. We commence by cultivating a comprehensive understanding of the tumor microenvironment and the pivotal roles played by macrophages. The dynamic landscape of macrophage polarization, typified by M1 and M2 phenotypes, is dissected to reveal its substantial impact on tumor progression. Lactic acid, a metabolic byproduct, emerges as a key protagonist, and we meticulously unravel the mechanisms underpinning its generation within cancer cells, shedding light on its intimate association with glycolysis and its transformative effects on the tumor microenvironment. Furthermore, we decipher the intricate molecular framework that underlies lactic acid's pivotal role in facilitating macrophage polarization. Our review underscores lactic acid's dual role in carcinogenesis, orchestrating tumor growth and immune modulation within the tumor microenvironment, thereby profoundly influencing the balance between pro-tumor and anti-tumor immune responses. This duality highlights the therapeutic potential of selectively manipulating lactic acid metabolism for cancer treatment. Exploring strategies to inhibit lactic acid production by tumor cells, novel approaches to impede lactic acid transport in the tumor microenvironment, and the burgeoning field of immunotherapeutic cancer therapies utilizing lactic acid-induced macrophage polarization form the core of our investigation.

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

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

Cancer Metabolism Historical Perspectives: A Chronicle of Controversies and Consensus

A century ago, Otto Warburg's work sparked the field of cancer metabolism, which has since taken a tortuous path. As evidence accumulated over the decades, consensus views of causes of cancer emerged, whereby genetic and epigenetic oncogenic drivers promoted immune evasion and induced new blood vessels and neoplastic metabolism to support tumor growth. Neoplastic cells abandon social cues of intercellular cooperation, escape tissue confinement, metastasize, and ultimately kill the host. Herein, key milestones in the study of cancer metabolism are chronicled with an emphasis on carbohydrate metabolism. The field began with a cancer cell-autonomous view that has been refined by a richer understanding of solid cancers as growing, immune-suppressive, complex organs comprising different cell types that are nourished by a variety of nutrients and variable amounts of oxygen through abnormal neovasculatures. Based on foundational historical studies, our current understanding of cancer metabolism offers a hopeful outlook for targeting metabolism to enhance cancer therapy.

Mitochondrial-Encoded Complex I Impairment Induces a Targetable Dependency on Aerobic Fermentation in Hürthle Cell Carcinoma of the Thyroid

A metabolic hallmark of cancer identified by Warburg is the increased consumption of glucose and secretion of lactate, even in the presence of oxygen. Although many tumors exhibit increased glycolytic activity, most forms of cancer rely on mitochondrial respiration for tumor growth. We report here that Hürthle cell carcinoma of the thyroid (HTC) models harboring mitochondrial DNA-encoded defects in complex I of the mitochondrial electron transport chain exhibit impaired respiration and alterations in glucose metabolism. CRISPR-Cas9 pooled screening identified glycolytic enzymes as selectively essential in complex I-mutant HTC cells. We demonstrate in cultured cells and a patient-derived xenograft model that small-molecule inhibitors of lactate dehydrogenase selectively induce an ATP crisis and cell death in HTC. This work demonstrates that complex I loss exposes fermentation as a therapeutic target in HTC and has implications for other tumors bearing mutations that irreversibly damage mitochondrial respiration.

SIGNIFICANCE

HTC is enriched in somatic mtDNA mutations predicted to affect complex I of the electron transport chain (ETC). We demonstrate that these mutations impair respiration and induce a therapeutically tractable reliance on aerobic fermentation for cell survival. This work provides a rationale for targeting fermentation in cancers harboring irreversible genetically encoded ETC defects. See related article by Gopal et al., p. 1904. This article is highlighted in the In This Issue feature, p. 1749.

Role of mitochondrial alterations in human cancer progression and cancer immunity

Dysregulating cellular metabolism is one of the emerging cancer hallmarks. Mitochondria are essential organelles responsible for numerous physiologic processes, such as energy production, cellular metabolism, apoptosis, and calcium and redox homeostasis. Although the "Warburg effect," in which cancer cells prefer aerobic glycolysis even under normal oxygen circumstances, was proposed a century ago, how mitochondrial dysfunction contributes to cancer progression is still unclear. This review discusses recent progress in the alterations of mitochondrial DNA (mtDNA) and mitochondrial dynamics in cancer malignant progression. Moreover, we integrate the possible regulatory mechanism of mitochondrial dysfunction-mediated mitochondrial retrograde signaling pathways, including mitochondrion-derived molecules (reactive oxygen species, calcium, oncometabolites, and mtDNA) and mitochondrial stress response pathways (mitochondrial unfolded protein response and integrated stress response) in cancer progression and provide the possible therapeutic targets. Furthermore, we discuss recent findings on the role of mitochondria in the immune regulatory function of immune cells and reveal the impact of the tumor microenvironment and metabolism remodeling on cancer immunity. Targeting the mitochondria and metabolism might improve cancer immunotherapy. These findings suggest that targeting mitochondrial retrograde signaling in cancer malignancy and modulating metabolism and mitochondria in cancer immunity might be promising treatment strategies for cancer patients and provide precise and personalized medicine against cancer.

Cancer Bioenergetics and Tumor Microenvironments-Enhancing Chemotherapeutics and Targeting Resistant Niches through Nanosystems

Cancer is an impending bottleneck in the advanced scientific workflow to achieve diagnostic, prognostic, and therapeutic success. Most cancers are refractory to conventional diagnostic and chemotherapeutics due to their limited targetability, specificity, solubility, and side effects. The inherent ability of each cancer to evolve through various genetic and epigenetic transformations and metabolic reprogramming underlies therapeutic limitations. Though tumor microenvironments (TMEs) are quite well understood in some cancers, each microenvironment differs from the other in internal perturbations and metabolic skew thereby impeding the development of appropriate diagnostics, drugs, vaccines, and therapies. Cancer associated bioenergetics modulations regulate TME, angiogenesis, immune evasion, generation of resistant niches and tumor progression, and a thorough understanding is crucial to the development of metabolic therapies. However, this remains a missing element in cancer theranostics, necessitating the development of modalities that can be adapted for targetability, diagnostics and therapeutics. In this challenging scenario, nanomaterials are modular platforms for understanding TME and achieving successful theranostics. Several nanoscale particles have been successfully researched in animal models, quite a few have reached clinical trials, and some have achieved clinical success. Nanoparticles exhibit an intrinsic capability to interact with diverse biomolecules and modulate their functions. Furthermore, nanoparticles can be functionalized with receptors, modulators, and drugs to facilitate specific targeting with reduced toxicity. This review discusses the current understanding of different theranostic nanosystems, their synthesis, functionalization, and targetability for therapeutic modulation of bioenergetics, and metabolic reprogramming of the cancer microenvironment. We highlight the potential of nanosystems for enhanced chemotherapeutic success emphasizing the questions that remain unanswered.

Impairing Tumor Metabolic Plasticity via a Stable Metal-Phenolic-Based Polymeric Nanomedicine to Suppress Colorectal Cancer

Targeting metabolic vulnerability of tumor cells is a promising anticancer strategy. However, the therapeutic efficacy of existing metabolism-regulating agents is often compromised due to tolerance resulting from tumor metabolic plasticity, as well as their poor bioavailability and tumor-targetability. Inspired by the inhibitive effect of N-ethylmaleimide on the mitochondrial function, a dendronized-polymer-functionalized metal-phenolic nanomedicine (pOEG-b-D-SH@NP) encapsulating maleimide-modified doxorubicin (Mal-DOX) is developed to enable improvement in the overall delivery efficiency and inhibition of the tumor metabolism via multiple pathways. It is observed that Mal-DOX and its derived nanomedicine induces energy depletion of CT26 colorectal cancer cells more efficiently than doxorubicin, and shifts the balance of programmed cell death from apoptosis toward necroptosis. Notably, pOEG-b-D-SH@NP simultaneously inhibits cellular oxidative phosphorylation and glycolysis, thus potently suppressing cancer growth and peritoneal intestinal metastasis in mouse models. Overall, the study provides a promising dendronized-polymer-derived nanoplatform for the treatment of cancers through impairing metabolic plasticity.

Lactate mediated metabolic crosstalk between cancer and immune cells and its therapeutic implications

Metabolism is central to energy generation and cell signaling in all life forms. Cancer cells rely heavily on glucose metabolism wherein glucose is primarily converted to lactate even in adequate oxygen conditions, a process famously known as "the Warburg effect." In addition to cancer cells, Warburg effect was found to be operational in other cell types, including actively proliferating immune cells. According to current dogma, pyruvate is the end product of glycolysis that is converted into lactate in normal cells, particularly under hypoxic conditions. However, several recent observations suggest that the final product of glycolysis may be lactate, which is produced irrespective of oxygen concentrations. Traditionally, glucose-derived lactate can have three fates: it can be used as a fuel in the TCA cycle or lipid synthesis; it can be converted back into pyruvate in the cytosol that feeds into the mitochondrial TCA; or, at very high concentrations, accumulated lactate in the cytosol may be released from cells that act as an oncometabolite. In immune cells as well, glucose-derived lactate seems to play a major role in metabolism and cell signaling. However, immune cells are much more sensitive to lactate concentrations, as higher lactate levels have been found to inhibit immune cell function. Thus, tumor cell-derived lactate may serve as a major player in deciding the response and resistance to immune cell-directed therapies. In the current review, we will provide a comprehensive overview of the glycolytic process in eukaryotic cells with a special focus on the fate of pyruvate and lactate in tumor and immune cells. We will also review the evidence supporting the idea that lactate, not pyruvate, is the end product of glycolysis. In addition, we will discuss the impact of glucose-lactate-mediated cross-talk between tumor and immune cells on the therapeutic outcomes after immunotherapy.

OXPHOS inhibitors, metabolism and targeted therapies in cancer

More and more studies highlight the complex metabolic characteristics and plasticity of cancer cells. To address these specificities and explore the associated vulnerabilities, new metabolism-targeting therapeutic strategies are being developed. It is more and more accepted that cancer cells do not produce their energy only from aerobic glycolysis, as some subtypes strongly rely on mitochondrial respiration (OXPHOS). This review focuses on classical and promising OXPHOS inhibitors (OXPHOSi), unravelling their interest and modes of actions in cancer, particularly in combination with other strategies. Indeed, in monotherapy, OXPHOSi display limited efficiency as they mostly trigger cell death in cancer cell subtypes that strongly depend on mitochondrial respiration and are not able to shift to other metabolic pathways to produce energy. Nevertheless, they remain very interesting in combination with conventional therapeutic strategies such as chemotherapy and radiotherapy, increasing their anti-tumoral actions. In addition, OXPHOSi can be included in even more innovative strategies such as combinations with other metabolic drugs or immunotherapies.

Mitoribosome sensitivity to HSP70 inhibition uncovers metabolic liabilities of castration-resistant prostate cancer

The androgen receptor is a key regulator of prostate cancer and the principal target of current prostate cancer therapies collectively termed androgen deprivation therapies. Insensitivity to these drugs is a hallmark of progression to a terminal disease state termed castration-resistant prostate cancer. Therefore, novel therapeutic options that slow progression of castration-resistant prostate cancer and combine effectively with existing agents are in urgent need. We show that JG-98, an allosteric inhibitor of HSP70, re-sensitizes castration-resistant prostate cancer to androgen deprivation drugs by targeting mitochondrial HSP70 (HSPA9) to suppress aerobic respiration. Rather than impacting androgen receptor stability as previously described, JG-98's primary effect is inhibition of mitochondrial translation, leading to disruption of electron transport chain activity. Although functionally distinct from HSPA9 inhibition, direct inhibition of the electron transport chain with a complex I or II inhibitor creates a similar physiological state capable of re-sensitizing castration-resistant prostate cancer to androgen deprivation therapies. These data identify a significant role for HspA9 in mitochondrial ribosome function and highlight an actionable metabolic vulnerability of castration-resistant prostate cancer.

Seasonal assessment of the distribution, source apportionment, and risk of water-contaminated polycyclic aromatic hydrocarbons (PAHs)

The research aims to evaluate the seasonal differences in the distribution, source, and risks of water-contaminated PAHs. The PAHs were extracted by the liquid-liquid method and analyzed with GC-MS, and a total of eight PAHs were detected. There was a percentage increase in the average concentration of the PAHs from the wet to the dry season in the range of 20 (Anthracene)-350 (Pyrene)%. Total PAHs (∑PAHs) range from 0.31 to 1.23 mg/l in the wet period and from 0.42 to 1.96 mg/l in the dry period. The distribution of the average PAHs in mg/l showed that Fluoranthene ≤ Pyrene < Acenaphthene < Fluorene < Phenanthrene < Acenaphthylene < Anthracene < Naphthalene in wet period and while Fluoranthene < Acenaphthene < Pyrene < Fluorene < Phenanthrene < Acenaphthylene < Anthracene < Naphthalene in the dry period. The children were exposed to non-carcinogenic risk through non-dietary ingestion due to the accumulative effect (HI) of the PAHs in the dry period. Furthermore, the naphthalene was responsible for ecological and carcinogenic risk in the wet period, while the fluorene, phenanthrene, and anthracene were responsible for ecological and carcinogenic risk in the dry period. However, while adults and children are both susceptible to carcinogenic risk through the oral channel during the dry period, only children are susceptible to non-carcinogenic risk through this pathway. The multivariate statistical analysis revealed the influence of physicochemical parameters on the detected PAHs and also showed the PAHs' sources to be mainly combustion, pyrolysis, and vehicular emission.

Rationale for LDH-targeted cancer immunotherapy

Immunotherapies have significantly improved the survival of patients in many cancers over the last decade. However, primary and secondary resistances are encountered in most patients. Unravelling resistance mechanisms to cancer immunotherapies is an area of active investigation. Elevated levels of circulating enzyme lactate dehydrogenase (LDH) have been historically considered in oncology as a marker of bad prognosis, usually attributed to elevated tumour burden and cancer metabolism. Recent evidence suggests that elevated LDH levels could be independent from tumour burden and contain a negative predictive value, which could help in guiding treatment strategies in immuno-oncology. In this review, we decipher the rationale supporting the potential of LDH-targeted therapeutic strategies to tackle the direct immunosuppressive effects of LDH on a wide range of immune cells, and enhance the survival of patients treated with cancer immunotherapies.

Tumor lactic acid: a potential target for cancer therapy

Tumor development is influenced by circulating metabolites and most tumors are exposed to substantially elevated levels of lactic acid and low levels of nutrients, such as glucose and glutamine. Tumor-derived lactic acid, the major circulating carbon metabolite, regulates energy metabolism and cancer cell signaling pathways, while also acting as an energy source and signaling molecule. Recent studies have yielded new insights into the pro-tumorigenic action of lactic acid and its metabolism. These insights suggest an anti-tumor therapeutic strategy targeting the oncometabolite lactic acid, with the aim of improving the efficacy and clinical safety of tumor metabolism inhibitors. This review describes the current understanding of the multifunctional roles of tumor lactic acid, as well as therapeutic approaches targeting lactic acid metabolism, including lactate dehydrogenase and monocarboxylate transporters, for anti-cancer therapy.

Metabolic Health, Mitochondrial Fitness, Physical Activity, and Cancer

Cancer continues to be a significant global health issue. Traditional genetic-based approaches to understanding and treating cancer have had limited success. Researchers are increasingly exploring the impact of the environment, specifically inflammation and metabolism, on cancer development. Examining the role of mitochondria in this context is crucial for understanding the connections between metabolic health, physical activity, and cancer. This study aimed to review the literature on this topic through a comprehensive narrative review of various databases including MedLine (PubMed), Cochrane (Wiley), Embase, PsychINFO, and CinAhl. The review highlighted the importance of mitochondrial function in overall health and in regulating key events in cancer development, such as apoptosis. The concept of "mitochondrial fitness" emphasizes the crucial role of mitochondria in cell metabolism, particularly their oxidative functions, and how proper function can prevent replication errors and regulate apoptosis. Engaging in high-energy-demanding movement, such as exercise, is a powerful intervention for improving mitochondrial function and increasing resistance to environmental stressors. These findings support the significance of considering the role of the environment, specifically inflammation and metabolism, in cancer development and treatment. Further research is required to fully understand the mechanisms by which physical activity improves mitochondrial function and potentially reduces the risk of cancer.

Effects of chronic exposure of naturally weathered microplastics on oxidative stress level, behaviour, and mitochondrial function of adult zebrafish (Danio rerio)

Microplastics (MPs) are a big and growing environmental concern, with studies showing sublethal to acute biological impacts on typical aquatic organisms. However, little is known about the biological effects of naturally weathered MPs, particularly focusing on mitochondria dysfunction as the key trigger of the biological effects. Therefore, in this study, naturally weathered MPs were produced from day-to-day life products, characterized, and chronically exposed (21 days) to adult zebrafish at the concentration of 0.1 and 1 mg/L. Locomotion and unconditioned anxiety-like behaviour was assessed. Mitochondrial respiration, membrane potential, mitochondrial complex activity and oxidative-related parameters were evaluated in the brain and liver. The results revealed the weathered MPs as a copolymer of propylene and ethylene that induced anxiety-like behaviour. There was an increase in brain catalase activity while the brain lactate dehydrogenase activity was inhibited after exposure to 1 mg/L. Brain glutathione levels were increased while their ratio was not affected. Mitochondrial respiratory chain complex Ⅱ and IV were also significantly decreased in the brain, although not compromising mitochondrial function. On the other hand, exposure to 1 mg/L caused a deficiency in liver mitochondrial respiration and decreased mitochondrial membrane potential, which were associated with the mitochondrial respiratory chain inhibition. An increase in hepatic superoxide dismutase and catalase activity was noticed, supporting the occurrence of ROS-induced ROS release as the potential trigger for the mitochondrial dysfunction. Overall, these findings highlight the potential indirect and cumulative environmental effects these particles may pose to aquatic ecosystems.

Glutamine-dependent effects of nitric oxide on cancer cells subjected to hypoxia-reoxygenation

Limited O₂ availability can decrease essential processes in energy metabolism. However, cancers have developed distinct metabolic adaptations to these conditions. For example, glutaminolysis can maintain energy metabolism and hypoxia signaling. Additionally, it has been observed that nitric oxide (NO) possesses concentration-dependent, biphasic effects in cancer. NO has potent anti-tumor effects through modulating events such as angiogenesis and metastasis at low physiological concentrations and inducing cell death at higher concentrations. In this study, Ewing Sarcoma cells (A-673), MIA PaCa, and SKBR3 cells were treated with DetaNONOate (DetaNO) in a model of hypoxia (1% O₂) and reoxygenation (21% O₂). All 3 cell types showed NO-dependent inhibition of cellular O₂ consumption which was enhanced as O₂-tension decreased. L-Gln depletion suppressed the mitochondrial response to decreasing O₂ tension in all 3 cell types and resulted in inhibition of Complex I activity. In A-673 cells the O₂ tension dependent change in mitochondrial O₂ consumption and increase in glycolysis was dependent on the presence of L-Gln. The response to hypoxia and Complex I activity were restored by α-ketoglutarate. NO exposure resulted in the A-673 cells showing greater sensitivity to decreasing O₂ tension. Under conditions of L-Gln depletion, NO restored HIF-1α levels and the mitochondrial response to O₂ tension possibly through the increase of 2-hydroxyglutarate. NO also resulted in suppression of cellular bioenergetics and further inhibition of Complex I which was not rescued by α-ketoglutarate. Taken together these data suggest that NO modulates the mitochondrial response to O₂ differentially in the absence and presence of L-Gln. These data suggest a combination of metabolic strategies targeting glutaminolysis and Complex I in cancer cells.

Lactate in the tumor microenvironment: A rising star for targeted tumor therapy

Metabolic reprogramming is one of fourteen hallmarks of tumor cells, among which aerobic glycolysis, often known as the "Warburg effect," is essential to the fast proliferation and aggressive metastasis of tumor cells. Lactate, on the other hand, as a ubiquitous molecule in the tumor microenvironment (TME), is generated primarily by tumor cells undergoing glycolysis. To prevent intracellular acidification, malignant cells often remove lactate along with H⁺, yet the acidification of TME is inevitable. Not only does the highly concentrated lactate within the TME serve as a substrate to supply energy to the malignant cells, but it also works as a signal to activate multiple pathways that enhance tumor metastasis and invasion, intratumoral angiogenesis, as well as immune escape. In this review, we aim to discuss the latest findings on lactate metabolism in tumor cells, particularly the capacity of extracellular lactate to influence cells in the tumor microenvironment. In addition, we examine current treatment techniques employing existing medications that target and interfere with lactate generation and transport in cancer therapy. New research shows that targeting lactate metabolism, lactate-regulated cells, and lactate action pathways are viable cancer therapy strategies.

EPR and Related Magnetic Resonance Imaging Techniques in Cancer Research

Imaging tumor microenvironments such as hypoxia, oxygenation, redox status, and/or glycolytic metabolism in tissues/cells is useful for diagnostic and prognostic purposes. New imaging modalities are under development for imaging various aspects of tumor microenvironments. Electron Paramagnetic Resonance Imaging (EPRI) though similar to NMR/MRI is unique in its ability to provide quantitative images of pO₂ in vivo. The short electron spin relaxation times have been posing formidable challenge to the technology development for clinical application. With the availability of the narrow line width trityl compounds, pulsed EPR imaging techniques were developed for pO₂ imaging. EPRI visualizes the exogenously administered spin probes/contrast agents and hence lacks the complementary morphological information. Dynamic nuclear polarization (DNP), a phenomenon that transfers the high electron spin polarization to the surrounding nuclear spins (¹H and ¹³C) opened new capabilities in molecular imaging. DNP of ¹³C nuclei is utilized in metabolic imaging of 13C-labeled compounds by imaging specific enzyme kinetics. In this article, imaging strategies mapping physiologic and metabolic aspects in vivo are reviewed within the framework of their application in cancer research, highlighting the potential and challenges of each of them.

Targeting lactate metabolism for cancer immunotherapy - a matter of precision

Immune checkpoint inhibitors and adoptive T cell therapies have been valuable additions to the toolbox in the fight against cancer. These treatments have profoundly increased the number of patients with a realistic perspective toward a return to a cancer-free life. Yet, in a number of patients and tumor entities, cancer immunotherapies have been ineffective so far. In solid tumors, immune exclusion and the immunosuppressive tumor microenvironment represent substantial roadblocks to successful therapeutic outcomes. A major contributing factor to the depressed anti-tumor activity of immune cells in tumors is the harsh metabolic environment. Hypoxia, nutrient competition with tumor and stromal cells, and accumulating noxious waste products, including lactic acid, pose massive constraints to anti-tumor immune cells. Numerous strategies are being developed to exploit the metabolic vulnerabilities of tumor cells in the hope that these would also alleviate metabolism-inflicted immune suppression. While promising in principle, especially in combination with immunotherapies, these strategies need to be scrutinized for their effect on tumor-fighting immune cells, which share some of their key metabolic properties with tumor cells. Here, we provide an overview of strategies that seek to tackle lactate metabolism in tumor or immune cells to unleash anti-tumor immune responses, thereby opening therapeutic options for patients whose tumors are currently not treatable.

The Lactate and the Lactate Dehydrogenase in Inflammatory Diseases and Major Risk Factors in COVID-19 Patients

Lactate dehydrogenase (LDH) is a terminating enzyme in the metabolic pathway of anaerobic glycolysis with end product of lactate from glucose. The lactate formation is crucial in the metabolism of glucose when oxygen is in inadequate supply. Lactate can also be formed and utilised by different cell types under fully aerobic conditions. Blood LDH is the marker enzyme, which predicts mortality in many conditions such as ARDS, serious COVID-19 and cancer patients. Lactate plays a critical role in normal physiology of humans including an energy source, a signaling molecule and a pH regulator. Depending on the pH, lactate exists as the protonated acidic form (lactic acid) at low pH or as sodium salt (sodium lactate) at basic pH. Lactate can affect the immune system and act as a signaling molecule, which can provide a "danger" signal for life. Several reports provide evidence that the serum lactate represents a chemical marker of severity of disease similar to LDH under inflammatory conditions. Since the mortality rate is much higher among COVID-19 patients, associated with high serum LDH, this article is aimed to review the LDH as a therapeutic target and lactate as potential marker for monitoring treatment response of inflammatory diseases. Finally, the review summarises various LDH inhibitors, which offer potential applications as therapeutic agents for inflammatory diseases, associated with high blood LDH. Both blood LDH and blood lactate are suggested as risk factors for the mortality of patients in serious inflammatory diseases.

Tracing the electron flow in redox metabolism: The appropriate distribution of electrons is essential to maintain redox balance in cancer cells

Cancer cells are characterized by sustained proliferation, which requires a huge demand of fuels to support energy production and biosynthesis. Energy is produced by the oxidation of the fuels during catabolism, and biosynthesis is achieved by the reduction of smaller units or precursors. Therefore, the oxidation-reduction (redox) reactions in cancer cells are more active compared to those in the normal counterparts. The higher activity of redox metabolism also induces a more severe oxidative stress, raising the question of how cancer cells maintain the redox balance. In this review, we overview the redox metabolism of cancer cells in an electron-tracing view. The electrons are derived from the nutrients in the tumor microenvironment and released during catabolism. Most of the electrons are transferred to NAD(P) system and then directed to four destinations: energy production, ROS generation, reductive biosynthesis and antioxidant system. The appropriate distribution of these electrons achieved by the function of redox regulation network is essential to maintain redox homeostasis in cancer cells. Interfering with the electron distribution and disrupting redox balance by targeting the redox regulation network may provide therapeutic implications for cancer treatment.

Cell Type-Specific Metabolic Response to Amino Acid Starvation Dictates the Role of Sestrin2 in Regulation of mTORC1

Targeting cancer metabolism has become one of the strategies for a rational anti-tumor therapy. However, cellular plasticity, driven by a major regulator of cellular growth and metabolism, mTORC1, often leads toward treatment resistance. Sestrin2, a stress-inducible protein, has been described as an mTORC1 inhibitor upon various types of stress signals. Immune assays and online measurements of cellular bioenergetics were employed to investigate the nature of Sestrin2 regulation, and finally, by silencing the SESN2 gene, to identify the role of induced Sestrin2 upon a single amino acid deprivation in cancer cells of various origins. Our data suggest that a complex interplay of either oxidative, energetic, nutritional stress, or in combination, play a role in Sestrin2 regulation upon single amino acid deprivation. Therefore, cellular metabolic background and sequential metabolic response dictate Sestrin2 expression in the absence of an amino acid. While deprivations of essential amino acids uniformly induce Sestrin2 levels, non-essential amino acids regulate Sestrin2 differently, drawing a characteristic Sestrin2 expression fingerprint, which could serve as a first indication of the underlying cellular vulnerability. Finally, we show that canonical GCN2-ATF4-mediated Sestrin2 induction leads to mTORC1 inhibition only in amino acid auxotroph cells, where the amino acid cannot be replenished by metabolic reprogramming.

The multiple roles of LDH in cancer

High serum lactate dehydrogenase (LDH) levels are typically associated with a poor prognosis in many cancer types. Even the most effective drugs, which have radically improved outcomes in patients with melanoma over the past decade, provide only marginal benefit to those with high serum LDH levels. When viewed separately from the oncological, biochemical, biological and immunological perspectives, serum LDH is often interpreted in very different ways. Oncologists usually see high serum LDH only as a robust biomarker of a poor prognosis, and biochemists are aware of the complexity of the various LDH isoforms and of their key roles in cancer metabolism, whereas LDH is typically considered to be oncogenic and/or immunosuppressive by cancer biologists and immunologists. Integrating these various viewpoints shows that the regulation of the five LDH isoforms, and their enzymatic and non-enzymatic functions is closely related to key oncological processes. In this Review, we highlight that serum LDH is far more than a simple indicator of tumour burden; it is a complex biomarker associated with the activation of several oncogenic signalling pathways as well as with the metabolic activity, invasiveness and immunogenicity of many tumours, and constitutes an extremely attractive target for cancer therapy.

Metabolic Pathways in Breast Cancer Reprograming: An Insight to Non-Coding RNAs

Cancer cells reprogram their metabolisms to achieve high energetic requirements and produce precursors that facilitate uncontrolled cell proliferation. Metabolic reprograming involves not only the dysregulation in glucose-metabolizing regulatory enzymes, but also the enzymes engaging in the lipid and amino acid metabolisms. Nevertheless, the underlying regulatory mechanisms of reprograming are not fully understood. Non-coding RNAs (ncRNAs) as functional RNA molecules cannot translate into proteins, but they do play a regulatory role in gene expression. Moreover, ncRNAs have been demonstrated to be implicated in the metabolic modulations in breast cancer (BC) by regulating the metabolic-related enzymes. Here, we will focus on the regulatory involvement of ncRNAs (microRNA, circular RNA and long ncRNA) in BC metabolism, including glucose, lipid and glutamine metabolism. Investigation of this aspect may not only alter the approaches of BC diagnosis and prognosis, but may also open a new avenue in using ncRNA-based therapeutics for BC treatment by targeting different metabolic pathways.

Tumor acidity: From hallmark of cancer to target of treatment

Tumor acidity is one of the cancer hallmarks and is associated with metabolic reprogramming and the use of glycolysis, which results in a high intracellular lactic acid concentration. Cancer cells avoid acid stress major by the activation and expression of proton and lactate transporters and exchangers and have an inverted pH gradient (extracellular and intracellular pHs are acid and alkaline, respectively). The shift in the tumor acid-base balance promotes proliferation, apoptosis avoidance, invasiveness, metastatic potential, aggressiveness, immune evasion, and treatment resistance. For example, weak-base chemotherapeutic agents may have a substantially reduced cellular uptake capacity due to "ion trapping". Lactic acid negatively affects the functions of activated effector T cells, stimulates regulatory T cells, and promotes them to express programmed cell death receptor 1. On the other hand, the inversion of pH gradient could be a cancer weakness that will allow the development of new promising therapies, such as tumor-targeted pH-sensitive antibodies and pH-responsible nanoparticle conjugates with anticancer drugs. The regulation of tumor pH levels by pharmacological inhibition of pH-responsible proteins (monocarboxylate transporters, H+-ATPase, etc.) and lactate dehydrogenase A is also a promising anticancer strategy. Another idea is the oral or parenteral use of buffer systems, such as sodium bicarbonate, to neutralize tumor acidity. Buffering therapy does not counteract standard treatment methods and can be used in combination to increase effectiveness. However, the mechanisms of the anticancer effect of buffering therapy are still unclear, and more research is needed. We have attempted to summarize the basic knowledge about tumor acidity.

Transcriptional, chromatin, and metabolic landscapes of LDHA inhibitor-resistant pancreatic ductal adenocarcinoma

Metabolic reprogramming, due in part to the overexpression of metabolic enzymes, is a key hallmark of cancer cells. Lactate dehydrogenase (LDHA), a metabolic enzyme that catalyzes the interconversion of lactate and pyruvate, is overexpressed in a wide variety of cancer types, including pancreatic ductal adenocarcinoma (PDAC). Furthermore, the genetic or pharmacological inhibition of LDHA suppresses cancer growth, demonstrating a cancer-promoting role for this enzyme. Therefore, several pharmacological LDHA inhibitors are being developed and tested as potential anti-cancer therapeutic agents. Because cancer cells are known to rapidly adapt and become resistant to anti-cancer therapies, in this study, we modeled the adaptation of cancer cells to LDHA inhibition. Using PDAC as a model system, we studied the molecular aspects of cells resistant to the competitive LDHA inhibitor sodium oxamate. We performed unbiased RNA-sequencing (RNA-seq), assay for transposase-accessible chromatin with sequencing (ATAC-seq), and metabolomics analyses of parental and oxamate-resistant PDAC cells treated with and without oxamate to identify the transcriptional, chromatin, and metabolic landscapes of these cells. We found that oxamate-resistant PDAC cells were significantly different from parental cells at the levels of mRNA expression, chromatin accessibility, and metabolites. Additionally, an integrative analysis combining the RNA-seq and ATAC-seq datasets identified a subset of differentially expressed mRNAs that directly correlated with changes in chromatin accessibility. Finally, functional analysis of differentially expressed metabolic genes in parental and oxamate-resistant PDAC cells treated with and without oxamate, together with an integrative analysis of RNA-seq and metabolomics data, revealed changes in metabolic enzymes that might explain the changes in metabolite levels observed in these cells. Collectively, these studies identify the transcriptional, chromatin, and metabolic landscapes of LDHA inhibitor resistance in PDAC cells. Future functional studies related to these changes remain necessary to reveal the direct roles played by these changes in the development of LDHA inhibitor resistance and uncover approaches for more effective use of LDHA inhibitors in cancer therapy.

Discovery of novel human lactate dehydrogenase inhibitors: Structure-based virtual screening studies and biological assessment

Most cancer cells switch their metabolism from mitochondrial oxidative phosphorylation to aerobic glycolysis to generate ATP and precursors for the biosynthesis of key macromolecules. The aerobic conversion of pyruvate to lactate, coupled to oxidation of the nicotinamide cofactor, is a primary hallmark of cancer and is catalyzed by lactate dehydrogenase (LDH), a central effector of this pathological reprogrammed metabolism. Hence, inhibition of LDH is a potential new promising therapeutic approach for cancer. In the search for new LDH inhibitors, we carried out a structure-based virtual screening campaign. Here, we report the identification of a novel specific LDH inhibitor, the pyridazine derivative 18 (RS6212), that exhibits potent anticancer activity within the micromolar range in multiple cancer cell lines and synergizes with complex I inhibition in the suppression of tumor growth. Altogether, our data support the conclusion that compound 18 deserves to be further investigated as a starting point for the development of LDH inhibitors and for novel anticancer strategies based on the targeting of key metabolic steps.

Therapeutic Targeting of Tumor Cells and Tumor Immune Microenvironment Vulnerabilities

Therapeutic targeting of tumor vulnerabilities is emerging as a key area of research. This review is focused on exploiting the vulnerabilities of tumor cells and the immune cells in the tumor immune microenvironment (TIME), including tumor hypoxia, tumor acidity, the bidirectional proton-coupled monocarboxylate transporters (MCTs) of lactate, mitochondrial oxidative phosphorylation (OXPHOS), and redox enzymes in the tricarboxylic acid cycle. Cancer cells use glucose for energy even under normoxic conditions. Although cancer cells predominantly rely on glycolysis, many have fully functional mitochondria, suggesting that mitochondria are a vulnerable target organelle in cancer cells. Thus, one key distinction between cancer and normal cell metabolism is metabolic reprogramming. Mitochondria-targeted small molecule inhibitors of OXPHOS inhibit tumor proliferation and growth. Another hallmark of cancer is extracellular acidification due lactate accumulation. Emerging results show that lactate acts as a fuel for mitochondrial metabolism and supports tumor proliferation and growth. Metabolic reprogramming occurs in glycolysis-deficient tumor phenotypes and in kinase-targeted, drug-resistant cancers overexpressing OXPHOS genes. Glycolytic cancer cells located away from the vasculature overexpress MCT4 transporter to prevent overacidification by exporting lactate, and the oxidative cancer cells located near the vasculature express MCT1 transporter to provide energy through incorporation of lactate into the tricarboxylic acid cycle. MCTs are, therefore, a vulnerable target in cancer metabolism. MCT inhibitors exert synthetic lethality in combination with metformin, a weak inhibitor of OXPHOS, in cancer cells. Simultaneously targeting multiple vulnerabilities within mitochondria shows synergistic antiproliferative and antitumor effects. Developing tumor-selective, small molecule inhibitors of OXPHOS with a high therapeutic index is critical to fully exploiting the mitochondrial vulnerabilities. We and others developed small-molecule inhibitors containing triphenylphosphonium cation that potently inhibit OXPHOS in tumor cells and tissues. Factors affecting tumor cell vulnerabilities also impact immune cells in the TIME. Glycolytic tumor cells supply lactate to the tumor-suppressing regulatory T cells overexpressing MCTs. Therapeutic opportunities for targeting vulnerabilities in tumor cells and the TIME, as well as the implications on cancer health disparities and cancer treatment, are addressed.

Impact of tumor microenvironment on adoptive T cell transfer activity

Recent advances in immunotherapy have revolutionized the treatment of cancer. The use of adoptive cell therapies (ACT) such as those based on tumor infiltrating lymphocytes (TILs) or genetically modified cells (transgenic TCR lymphocytes or CAR-T cells), has shown impressive results in the treatment of several types of cancers. However, cancer cells can exploit mechanisms to escape from immunosurveillance resulting in many patients not responding to these therapies or respond only transiently. The failure of immunotherapy to achieve long-term tumor control is multifactorial. On the one hand, only a limited percentage of the transferred lymphocytes is capable of circulating through the bloodstream, interacting and crossing the tumor endothelium to infiltrate the tumor. Metabolic competition, excessive glucose consumption, the high level of lactic acid secretion and the extracellular pH acidification, the shortage of essential amino acids, the hypoxic conditions or the accumulation of fatty acids in the tumor microenvironment (TME), greatly hinder the anti-tumor activity of the immune cells in ACT therapy strategies. Therefore, there is a new trend in immunotherapy research that seeks to unravel the fundamental biology that underpins the response to therapy and identifies new approaches to better amplify the efficacy of immunotherapies. In this review we address important aspects that may significantly affect the efficacy of ACT, indicating also the therapeutic alternatives that are currently being implemented to overcome these drawbacks.

Evaluation of Syrosingopine, an MCT Inhibitor, as Potential Modulator of Tumor Metabolism and Extracellular Acidification

Extracellular acidification has been shown to be an important characteristic of invasive tumors, as it promotes invasion and migration but also resistance to treatments. Targeting transporters involved in the regulation of tumor pH constitutes a promising anti-tumor approach, as it would disrupt cellular pH homeostasis and negatively impact tumor growth. In this study, we evaluated the impact of syrosingopine, an inhibitor of MCT1 and MCT4, as a modulator of tumor metabolism and extracellular acidification in human breast cancer (MDA-MB-231) and pharyngeal squamous cell carcinoma (FaDu) cell models. In both models in vitro, we observed that exposure to syrosingopine led to a decrease in the extracellular acidification rate, intracellular pH, glucose consumption, lactate secretion and tumor cell proliferation with an increase in the number of late apoptotic/necrotic cells. However, in vivo experiments using the MDA-MB-231 model treated with a daily injection of syrosingopine did not reveal any significant change in extracellular pH (pHe) (as measured using CEST-MRI) or primary tumor growth. Overall, our study suggests that targeting MCT could lead to profound changes in tumor cell metabolism and proliferation, and it warrants further research to identify candidates without off-target effects.

Simultaneous targeting of glycolysis and oxidative phosphorylation as a therapeutic strategy to treat diffuse large B-cell lymphoma

Background

We evaluated the therapeutic potential of combining the monocarboxylate transporter 1 (MCT1) inhibitor AZD3965 with the mitochondrial respiratory Complex I inhibitor IACS-010759, for the treatment of diffuse large B-cell lymphoma (DLBCL), a potential clinically actionable strategy to target tumour metabolism.

Methods

AZD3965 and IACS-010759 sensitivity were determined in DLBCL cell lines and tumour xenograft models. Lactate concentrations, oxygen consumption rate and metabolomics were examined as mechanistic endpoints. In vivo plasma concentrations of IACS-010759 in mice were determined by LC-MS to select a dose that reflected clinically attainable concentrations.

Results

In vitro, the combination of AZD3965 and IACS-010759 is synergistic and induces DLBCL cell death, whereas monotherapy treatments induce a cytostatic response. Significant anti-tumour activity was evident in Toledo and Farage models when the two inhibitors were administered concurrently despite limited or no effect on the growth of DLBCL xenografts as monotherapies.

Conclusions

This is the first study to examine a combination of two distinct approaches to targeting tumour metabolism in DLBCL xenografts. Whilst nanomolar concentrations of either AZD3965 or IACS-010759 monotherapy demonstrate anti-proliferative activity against DLBCL cell lines in vitro, appreciable clinical activity in DLBCL patients may only be realised through their combined use.

Multi-band echo-planar spectroscopic imaging of hyperpolarized 13 C probes in a compact preclinical PET/MR scanner

PURPOSE

Hyperpolarized (HP) 13 C MRI has enabled real-time imaging of specific enzyme-catalyzed metabolic reactions, but advanced pulse sequences are necessary to capture the dynamic, localized metabolic information. Herein we describe the design, implementation, and testing of a rapid and efficient HP 13 C pulse sequence strategy on a cryogen-free simultaneous positron emission tomography/MR molecular imaging platform with compact footprint.

METHODS

We developed an echo planar spectroscopic imaging pulse sequence incorporating multi-band spectral-spatial radiofrequency (SSRF) pulses for spatially coregistered excitation of 13 C metabolites with differential individual flip angles. Excitation profiles were measured in phantoms, and the SSRF-echo planar spectroscopic imaging sequence was tested in rats in vivo and compared to conventional echo planar spectroscopic imaging. The new sequence was applied for 2D dynamic metabolic imaging of HP [1-13 C]pyruvate and its molecular analog [1-13 C] α -ketobutyrate at a spatial resolution of 5 mm × 5 mm × 20 mm and temporal resolution of 4 s. We also obtained simultaneous 18 F-fluorodeoxyglucose positron emission tomography data for comparison with HP [1-13 C]pyruvate data acquired during the same scan session.

RESULTS

Measured SSRF excitation profiles corresponded well to Bloch simulations. Multi-band SSRF excitation facilitated efficient sampling of the multi-spectral kinetics of [1-13 C]pyruvate and [1-13 C] α - ketobutyrate . Whereas high pyruvate to lactate conversion was observed in liver, corresponding reduction of α -ketobutyrate to [1-13 C] α -hydroxybutyrate ( α HB) was largely restricted to the kidneys and heart, consistent with the known expression pattern of lactate dehydrogenase B.

CONCLUSION

Advanced 13 C SSRF imaging approaches are feasible on our compact positron emission tomography/MR platform, maximizing the potential of HP 13 C technology and facilitating direct comparison with positron emission tomography.

Overcoming T cell dysfunction in acidic pH to enhance adoptive T cell transfer immunotherapy

The high metabolic activity and insufficient perfusion of tumors leads to the acidification of the tumor microenvironment (TME) that may inhibit the antitumor T cell activity. We found that pharmacological inhibition of the acid loader chloride/bicarbonate anion exchanger 2 (Ae2), with 4,4’-diisothiocyanatostilbene-2,2’-disulfonicacid (DIDS) enhancedCD4⁺ andCD8⁺ T cell function upon TCR activation in vitro, especially under low pH conditions. In vivo, DIDS administration delayed B16OVA tumor growth in immunocompetent mice as monotherapy or when combined with adoptive T cell transfer of OVA-specificT cells. Notably, genetic Ae2 silencing in OVA-specificT cells improvedCD4⁺/CD8⁺ T cell function in vitro as well as their antitumor activity in vivo. Similarly, genetic modification of OVA-specificT cells to overexpress Hvcn1, a selectiveH⁺ outward current mediator that prevents cell acidification, significantly improved T cell function in vitro, even at low pH conditions. The adoptive transfer of OVA-specificT cells overexpressing Hvcn1 exerted a better antitumor activity in B16OVA tumor-bearingmice. Hvcn1 overexpression also improved the antitumor activity of CAR T cells specific for Glypican 3 (GPC3) in mice bearing PM299L-GPC3tumors. Our results suggest that preventing intracellular acidification by regulating the expression of acidifier ion channels such as Ae2 or alkalinizer channels like Hvcn1 in tumor-specificlymphocytes enhances their antitumor response by making them more resistant to the acidic TME.

Propofol Prevents the Growth, Migration, Invasion, and Glycolysis of Colorectal Cancer Cells by Downregulating Lactate Dehydrogenase Both In Vitro and In Vivo

Colorectal cancer (CRC) is one of the most frequently diagnosed gastrointestinal malignancies worldwide and has high rates of morbidity and mortality. Propofol has been reported to have certain anticancer properties. However, the role and mechanism of propofol in CRC are not entirely clear. CRC cells were treated with propofol and/or LDH-overexpression plasmids, and a mouse xenograft model of CRC was also established and treated with propofol. Cell viability, migration, and invasion were evaluated by CCK-8, wound healing, and transwell assays; the expression of related proteins was confirmed by western blotting; indexes of the glycolytic pathway were analyzed using specialized kits; tumor growth in mice was measured; pathological tissue structure was assessed by H&E staining; and 8-OHDG expression was determined by an immunochemistry assay. Our results verified that propofol could effectively prevent the malignant behaviors of CRC cells by suppressing cell viability, migration, and invasion and accelerating apoptosis. We also discovered that propofol could attenuate the glycolytic pathway in CRC cells. Moreover, we proved that lactate dehydrogenase (LDH) was required for the inhibitory effects of propofol on the growth of CRC cells, including glycolysis in CRC cells. Furthermore, our results showed that propofol could not only significantly inhibit tumor growth and glycolysis, but also ameliorate the pathological structure of CRC tumors. The current results proved that propofol could attenuate the malignant progression of CRC by preventing LDH activity, suggesting that propofol might be an effective therapeutic agent for CRC.

Targeting oncometabolism to maximize immunotherapy in malignant brain tumors

Brain tumors result in significant morbidity and mortality in both children and adults. Recent data indicates that immunotherapies may offer a survival benefit after standard of care has failed for malignant brain tumors. Modest results from several late phase clinical trials, however, underscore the need for more refined, comprehensive strategies that incorporate new mechanistic and pharmacologic knowledge. Recently, oncometabolism has emerged as an adjunct modality for combinatorial treatment approaches necessitated by the aggressive, refractory nature of high-grade glioma and other progressive malignant brain tumors. Manipulation of metabolic processes in cancer and immune cells that comprise the tumor microenvironment through controlled targeting of oncogenic pathways may be utilized to maximize the efficacy of immunotherapy and improve patient outcomes. Herein, we summarize preclinical and early phase clinical trial research of oncometabolism-based therapeutics that may augment immunotherapy by exploiting the biochemical and genetic underpinnings of brain tumors. We also examine metabolic pathways related to immune cells that target tumor cells, termed ‘tumor immunometabolism’. Specifically, we focus on glycolysis and altered glucose metabolism, including glucose transporters, hexokinase, pyruvate dehydrogenase, and lactate dehydrogenase, glutamine, and we discuss targeting arginase, adenosine, and indoleamine 2,3-dioxygenase (IDO), and toll-like receptors. Lastly, we summarize future directions targeting metabolism in combination with emerging therapies such as oncolytic virotherapy, vaccines, and chimeric antigen receptor T cells.

Structure-guided design enables development of a hyperpolarized molecular probe for the detection of aminopeptidase N activity in vivo

Dynamic nuclear polarization (DNP) is a cutting-edge technique that markedly enhances the detection sensitivity of molecules using nuclear magnetic resonance (NMR)/magnetic resonance imaging (MRI). This methodology enables real-time imaging of dynamic metabolic status in vivo using MRI. To expand the targetable metabolic reactions, there is a demand for developing exogenous, i.e., artificially designed, DNP-NMR molecular probes; however, complying with the requirements of practical DNP-NMR molecular probes is challenging because of the lack of established design guidelines. Here, we report Ala-[1-¹³C]Gly-d₂-NMe₂ as a DNP-NMR molecular probe for in vivo detection of aminopeptidase N activity. We developed this probe rationally through precise structural investigation, calculation, biochemical assessment, and advanced molecular design to achieve rapid and detectable responses to enzyme activity in vivo. With the fabricated probe, we successfully detected enzymatic activity in vivo. This report presents a comprehensive approach for the development of artificially derived, practical DNP-NMR molecular probes through structure-guided molecular design.

H3K9me3 represses G6PD expression to suppress the pentose phosphate pathway and ROS production to promote human mesothelioma growth

The role of glucose-6-phosphate dehydrogenase (G6PD) in human cancer is incompletely understood. In a metabolite screening, we observed that inhibition of H3K9 methylation suppressed aerobic glycolysis and enhances the PPP in human mesothelioma cells. Genome-wide screening identified G6PD as an H3K9me3 target gene whose expression is correlated with increased tumor cell apoptosis. Inhibition of aerobic glycolysis enzyme LDHA and G6PD had no significant effects on tumor cell survival. Ablation of G6PD had no significant effect on human mesothelioma and colon carcinoma xenograft growth in athymic mice. However, activation of G6PD with the G6PD-selective activator AG1 induced tumor cell death. AG1 increased tumor cell ROS production and the resultant extrinsic and intrinsic death pathways, mitochondrial processes, and unfolded protein response in tumor cells. Consistent with increased tumor cell death in vitro, AG1 suppressed human mesothelioma xenograft growth in a dose-dependent manner in vivo. Furthermore, AG1 treatment significantly increased tumor-bearing mouse survival in an intra-peritoneum xenograft athymic mouse model. Therefore, in human mesothelioma and colon carcinoma, G6PD is not essential for tumor growth. G6PD acts as a metabolic checkpoint to control metabolic flux towards the PPP to promote tumor cell apoptosis, and its expression is repressed by its promotor H3K9me3 deposition.

Combining structure-based and 3D QSAR pharmacophore models to discover diverse ligands against EGFR in oral cancer

Background: Epidermal growth factor receptor-tyrosine kinase (EGFR-TK) is a well-known hallmark of oral and oropharyngeal cancers, as its overexpression leads to poor prognosis and malignancy. The activating EGFR mutations (particularly T790M and L858R double mutant) are a major challenge causing drug resistance, especially in the treatment of oral cancers. Methodology: This paper is an effort to exploit both structure-based and ligand-based pharmacophore modeling to discover EGFR-TK inhibitors, which show inhibition of proliferation of erlotinib-resistant FaDu and Cal27 oral cancer cells. Interestingly, the hit compound H2 also showed an effect on the downstream glucose and lactate metabolism pathways. Conclusion: The results indicate the potential of H2 to be developed as an EGFR-based metabolic inhibitor for oral cancer treatment.

In Vivo Dynamic Nuclear Polarization Magnetic Resonance Imaging for the Evaluation of Redox-Related Diseases and Theranostics

Significance:In vivo molecular and metabolic imaging is an emerging field in biomedical research that aims to perform noninvasive detection of tissue metabolism in disease states and responses to therapeutic agents. The imbalance in tissue oxidation/reduction (Redox) states is related to the onset and progression of several diseases. Tissue redox metabolism provides biomarkers for early diagnosis and drug treatments. Thus, noninvasive imaging of redox metabolism could be a useful, novel diagnostic tool for diagnosis of redox-related disease and drug discovery. Recent Advances:In vivo dynamic nuclear polarization magnetic resonance imaging (DNP-MRI) is a technique that enables the imaging of free radicals in living animals. DNP enhances the MRI signal by irradiating the target tissue or solution with the free radical molecule's electron paramagnetic resonance frequency before executing pulse sequence of the MRI. In vivo DNP-MRI with redox-sensitive nitroxyl radicals as the DNP redox contrast agent enables the imaging of the redox metabolism on various diseases. Moreover, nitroxyl radicals show antioxidant effects that suppress oxidative stress. Critical Issues: To date, considerable progress has been documented preclinically in the development of animal imaging systems. Here, we review redox imaging of in vivo DNP-MRI with a focus on the recent progress of this system and its uses in patients with redox-related diseases. Future Directions: This technique could have broad applications in the study of other redox-related diseases, such as cancer, inflammation, and neurological disorders, and facilitate the evaluation of treatment response as a theranostic tool. Antioxid. Redox Signal. 36, 172-184.

Impact of cancer metabolism on therapy resistance - Clinical implications

Despite an increasing arsenal of anticancer therapies, many patients continue to have poor outcomes due to the therapeutic failures and tumor relapses. Indeed, the clinical efficacy of anticancer therapies is markedly limited by intrinsic and/or acquired resistance mechanisms that can occur in any tumor type and with any treatment. Thus, there is an urgent clinical need to implement fundamental changes in the tumor treatment paradigm by the development of new experimental strategies that can help to predict the occurrence of clinical drug resistance and to identify alternative therapeutic options. Apart from mutation-driven resistance mechanisms, tumor microenvironment (TME) conditions generate an intratumoral phenotypic heterogeneity that supports disease progression and dismal outcomes. Tumor cell metabolism is a prototypical example of dynamic, heterogeneous, and adaptive phenotypic trait, resulting from the combination of intrinsic [(epi)genetic changes, tissue of origin and differentiation dependency] and extrinsic (oxygen and nutrient availability, metabolic interactions within the TME) factors, enabling cancer cells to survive, metastasize and develop resistance to anticancer therapies. In this review, we summarize the current knowledge regarding metabolism-based mechanisms conferring adaptive resistance to chemo-, radio-and immunotherapies as well as targeted therapies. Furthermore, we report the role of TME-mediated intratumoral metabolic heterogeneity in therapy resistance and how adaptations in amino acid, glucose, and lipid metabolism support the growth of therapy-resistant cancers and/or cellular subpopulations. We also report the intricate interplay between tumor signaling and metabolic pathways in cancer cells and discuss how manipulating key metabolic enzymes and/or providing dietary changes may help to eradicate relapse-sustaining cancer cells. Finally, in the current era of personalized medicine, we describe the strategies that may be applied to implement metabolic profiling for tumor imaging, biomarker identification, selection of tailored treatments and monitoring therapy response during the clinical management of cancer patients.

Targeting cancer metabolism in the era of precision oncology

One hundred years have passed since Warburg discovered alterations in cancer metabolism, more than 70 years since Sidney Farber introduced anti-folates that transformed the treatment of childhood leukaemia, and 20 years since metabolism was linked to oncogenes. However, progress in targeting cancer metabolism therapeutically in the past decade has been limited. Only a few metabolism-based drugs for cancer have been successfully developed, some of which are in - or en route to - clinical trials. Strategies for targeting the intrinsic metabolism of cancer cells often did not account for the metabolism of non-cancer stromal and immune cells, which have pivotal roles in tumour progression and maintenance. By considering immune cell metabolism and the clinical manifestations of inborn errors of metabolism, it may be possible to isolate undesirable off-tumour, on-target effects of metabolic drugs during their development. Hence, the conceptual framework for drug design must consider the metabolic vulnerabilities of non-cancer cells in the tumour immune microenvironment, as well as those of cancer cells. In this Review, we cover the recent developments, notable milestones and setbacks in targeting cancer metabolism, and discuss the way forward for the field.

Metabolic derangement in polycystic kidney disease mouse models is ameliorated by mitochondrial-targeted antioxidants

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressively enlarging cysts. Here we elucidate the interplay between oxidative stress, mitochondrial dysfunction, and metabolic derangement using two mouse models of PKD1 mutation, PKD1RC/null and PKD1RC/RC. Mouse kidneys with PKD1 mutation have decreased mitochondrial complexes activity. Targeted proteomics analysis shows a significant decrease in proteins involved in the TCA cycle, fatty acid oxidation (FAO), respiratory complexes, and endogenous antioxidants. Overexpressing mitochondrial-targeted catalase (mCAT) using adeno-associated virus reduces mitochondrial ROS, oxidative damage, ameliorates the progression of PKD and partially restores expression of proteins involved in FAO and the TCA cycle. In human ADPKD cells, inducing mitochondrial ROS increased ERK1/2 phosphorylation and decreased AMPK phosphorylation, whereas the converse was observed with increased scavenging of ROS in the mitochondria. Treatment with the mitochondrial protective peptide, SS31, recapitulates the beneficial effects of mCAT, supporting its potential application as a novel therapeutic for ADPKD.