Inhibition of monocarboxylate transporter-1 (MCT1) by AZD3965 enhances radiosensitivity by reducing lactate transport

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.

Carrier-Free Photodynamic Bioregulators Inhibiting Lactic Acid Efflux Combined with Immune Checkpoint Blockade for Triple-Negative Breast Cancer Immunotherapy

Abnormal tumor metabolism creates a complex tumor immune microenvironment that plays a dominant role in the metastasis of triple-negative breast cancer (TNBC). TNBC is insensitive to immune checkpoint blockade (ICB) therapy because of insufficient cytotoxic T lymphocyte (CTL) infiltration and a hyper-lactic acid-suppressive immune microenvironment caused by abnormal glycolysis. Herein, we propose an amplified strategy based on lactic acid regulation to reprogram the immunosuppressive tumor microenvironment (ITM) and combine it with ICB therapy to achieve enhanced antitumor immunotherapy effects. Specifically, we constructed CASN, a carrier-free photodynamic bioregulator, through the self-assembly of the photosensitizer Chlorin e6 and monocarboxylate transporter 1 (MCT1) inhibitor AZD3965. CASN exhibited a uniform structure, good stability, and drug accumulation at the tumor site. CASN-mediated photodynamic therapy following laser irradiation inhibited primary tumor growth and induced immunogenic cell death. Furthermore, CASN reduced lactic acid-mediated regulatory T cell generation and M2 tumor-associated macrophage polarization by blocking MCT1-mediated lactic acid efflux to attenuate immune suppression, inducing the recruitment and activation of CTLs. Ultimately, CASN-mediated immunopotentiation combined with ICB therapy considerably strengthened tumor immunotherapy and effectively inhibited tumor growth and metastasis of TNBC. This synergistic amplification strategy overcomes the limitations of an acidic ITM and presents a potential clinical treatment option for metastatic tumors.

Targeting Metabolic-Redox Nexus to Regulate Drug Resistance: From Mechanism to Tumor Therapy

Drug resistance is currently one of the biggest challenges in cancer treatment. With the deepening understanding of drug resistance, various mechanisms have been revealed, including metabolic reprogramming and alterations of redox balance. Notably, metabolic reprogramming mediates the survival of tumor cells in harsh environments, thereby promoting the development of drug resistance. In addition, the changes during metabolic pattern shift trigger reactive oxygen species (ROS) production, which in turn regulates cellular metabolism, DNA repair, cell death, and drug metabolism in direct or indirect ways to influence the sensitivity of tumors to therapies. Therefore, the intersection of metabolism and ROS profoundly affects tumor drug resistance, and clarifying the entangled mechanisms may be beneficial for developing drugs and treatment methods to thwart drug resistance. In this review, we will summarize the regulatory mechanism of redox and metabolism on tumor drug resistance and highlight recent therapeutic strategies targeting metabolic-redox circuits, including dietary interventions, novel chemosynthetic drugs, drug combination regimens, and novel drug delivery systems.

Ionic Liquid Coating-Driven Nanoparticle Delivery to the Brain: Applications for NeuroHIV

Delivering cargo to the central nervous system (CNS) remains a pharmacological challenge. For infectious diseases such as HIV, the CNS acts as a latent reservoir that is inadequately managed by systemic antiretrovirals (ARTs). ARTs thus cannot eradicate HIV, and given CNS infection, patients experience neurological deficits collectively referred to as "neuroHIV". Herein, the development of bioinspired ionic liquid-coated nanoparticles (IL-NPs) for in situ hitchhiking on red blood cells (RBCs) is reported, which enables 48% brain delivery of intracarotid arterial- infused cargo. Moreover, IL choline trans-2-hexenoate (CA2HA 1:2) demonstrates preferential accumulation in parenchymal microglia over endothelial cells post-delivery. This study further demonstrates successful loading of abacavir (ABC), an ART that is challenging to encapsulate, into IL-NPs, and verifies retention of antiviral efficacy in vitro. IL-NPs are not cytotoxic to primary human peripheral blood mononuclear cells (PBMCs) and the CA2HA 1:2 coating itself confers notable anti-viremic capacity. In addition, in vitro cell culture assays show markedly increased uptake of IL-NPs into neural cells compared to bare PLGA nanoparticles. This work debuts bioinspired ionic liquids as promising nanoparticle coatings to assist CNS biodistribution and has the potential to revolutionize the delivery of cargos (i.e., drugs, viral vectors) through compartmental barriers such as the blood-brain-barrier (BBB).

Feedback loop between hypoxia and energy metabolic reprogramming aggravates the radioresistance of cancer cells

Radiotherapy is one of the mainstream approaches for cancer treatment, although the clinical outcomes are limited due to the radioresistance of tumor cells. Hypoxia and metabolic reprogramming are the hallmarks of tumor initiation and progression and are closely linked to radioresistance. Inside a tumor, the rate of angiogenesis lags behind cell proliferation, and the underdevelopment and abnormal functions of blood vessels in some loci result in oxygen deficiency in cancer cells, i.e., hypoxia. This prevents radiation from effectively eliminating the hypoxic cancer cells. Cancer cells switch to glycolysis as the main source of energy, a phenomenon known as the Warburg effect, to sustain their rapid proliferation rates. Therefore, pathways involved in metabolic reprogramming and hypoxia-induced radioresistance are promising intervention targets for cancer treatment. In this review, we discussed the mechanisms and pathways underlying radioresistance due to hypoxia and metabolic reprogramming in detail, including DNA repair, role of cancer stem cells, oxidative stress relief, autophagy regulation, angiogenesis and immune escape. In addition, we proposed the existence of a feedback loop between energy metabolic reprogramming and hypoxia, which is associated with the development and exacerbation of radioresistance in tumors. Simultaneous blockade of this feedback loop and other tumor-specific targets can be an effective approach to overcome radioresistance of cancer cells. This comprehensive overview provides new insights into the mechanisms underlying tumor radiosensitivity and progression.

Deciphering metabolic heterogeneity in retinoblastoma unravels the role of monocarboxylate transporter 1 in tumor progression

BACKGROUND

Tumors exhibit metabolic heterogeneity, influencing cancer progression. However, understanding metabolic diversity in retinoblastoma (RB), the primary intraocular malignancy in children, remains limited.

METHODS

The metabolic landscape of RB was constructed based on single-cell transcriptomic sequencing from 11 RB and 5 retina samples. Various analyses were conducted, including assessing overall metabolic activity, metabolic heterogeneity, and the correlation between hypoxia and metabolic pathways. Additionally, the expression pattern of the monocarboxylate transporter (MCT) family in different cell clusters was examined. Validation assays of MCT1 expression and function in RB cell lines were performed. The therapeutic potential of targeting MCT1 was evaluated using an orthotopic xenograft model. A cohort of 47 RB patients was analyzed to evaluate the relationship between MCT1 expression and tumor invasion.

RESULTS

Distinct metabolic patterns in RB cells, notably increased glycolysis, were identified. This metabolic heterogeneity correlated closely with hypoxia. MCT1 emerged as the primary monocarboxylate transporter in RB cells. Disrupting MCT1 altered cell viability and energy metabolism. In vivo studies using the MCT1 inhibitor AZD3965 effectively suppressed RB tumor growth. Additionally, a correlation between MCT1 expression and optic nerve invasion in RB samples suggested prognostic implications.

CONCLUSIONS

This study enhances our understanding of RB metabolic characteristics at the single-cell level, highlighting the significance of MCT1 in RB pathogenesis. Targeting MCT1 holds promise as a therapeutic strategy for combating RB, with potential prognostic implications.

Monocarboxylate transporter-1 (MCT-1) inhibitors screened from autodisplayed FV-antibody library

Monocarboxylate transporter-1 (MCT-1) inhibitors were screened from the Fv-antibody library, which contained complementary determining region 3 with randomized amino acid sequences (11 residues) through site-directed mutagenesis. Fv-antibodies against MCT-1 were screened from the autodisplayed Fv-antibody library. Two clones were screened, and the binding affinity (KD) against MCT-1 was estimated using flow cytometry. The screened Fv-antibodies were expressed as soluble fusion proteins (Fv-1 and Fv-2) and the KD for MCT-1 was estimated using the SPR biosensor. The inhibitory activity of the expressed Fv-antibodies was observed in HEK293T and Jurkat cell lines by measuring intracellular pH and lactate accumulation. The level of cell viability in HEK293T and Jurkat cell lines was decreased by the inhibitory activity of the expressed Fv-antibodies. The binding properties of the Fv-antibodies to MCT-1 were analyzed using molecular docking simulations. Overall, the results showed that the screened Fv-antibodies against MCT-1 from the Fv-antibody library had high binding affinity and inhibitory activity against MCT-1, which could be used as potential therapeutic drug candidates for the MCT-1 inhibitor.

DNase I rescues goat sperm entrapped by neutrophil extracellular traps

Artificial insemination has been a predominant technique employed in goat husbandry for breeding purposes. Subsequent to artificial insemination, sperm can elicit inflammation in the reproductive tract, resulting in substantial the accumulation of neutrophils. Recognized as foreign entities, sperm may become entrapped within neutrophil extracellular traps (NETs) released by neutrophils, thereby exploiting their properties of pathogen elimination. Deoxyribonuclease I (DNase I), which is known for disintegrating NETs and causing loss of function, has been utilized to ameliorate liver and brain damage resulting from NETs, as well as to enhance sperm quality. This study investigated the mechanism of sperm-induced NETs and further explored the impact of DNase I on NETs. Sperm quality was evaluated using optical microscopy, while the structure of NETs was observed through immunofluorescence staining. The formation mechanism of NETs was examined using inhibitors and PicoGreen. The findings revealed that sperm induced the formation of NETs, a process regulated by glycolysis, NADPH oxidase, ERK1/2, and p38 signaling pathways. The composition of NETs encompassed DNA, citrullinated histone H3 (citH3), and elastase (NE). DNase I protects sperm by degrading NETs, thereby concurrently preserving the integrity of plasma membrane and motility of sperm. In summary, the release of sperm-induced NETs leads to its damage, but this detrimental effect is counteracted by DNase I through degradation of NETs. These observations provide novel insights into reproductive immunity in goats.

Monocarboxylate transporters facilitate succinate uptake into brown adipocytes

Uptake of circulating succinate by brown adipose tissue (BAT) and beige fat elevates whole-body energy expenditure, counteracts obesity and antagonizes systemic tissue inflammation in mice. The plasma membrane transporters that facilitate succinate uptake in these adipocytes remain undefined. Here we elucidate a mechanism underlying succinate import into BAT via monocarboxylate transporters (MCTs). We show that succinate transport is strongly dependent on the proportion that is present in the monocarboxylate form. MCTs facilitate monocarboxylate succinate uptake, which is promoted by alkalinization of the cytosol driven by adrenoreceptor stimulation. In brown adipocytes, we show that MCT1 primarily facilitates succinate import. In male mice, we show that both acute pharmacological inhibition of MCT1 and congenital depletion of MCT1 decrease succinate uptake into BAT and consequent catabolism. In sum, we define a mechanism of succinate uptake in BAT that underlies its protective activity in mouse models of metabolic disease.

Metabolic symbiosis between oxygenated and hypoxic tumour cells: An agent-based modelling study

Deregulated metabolism is one of the hallmarks of cancer. It is well-known that tumour cells tend to metabolize glucose via glycolysis even when oxygen is available and mitochondrial respiration is functional. However, the lower energy efficiency of aerobic glycolysis with respect to mitochondrial respiration makes this behaviour, namely the Warburg effect, counter-intuitive, although it has now been recognized as source of anabolic precursors. On the other hand, there is evidence that oxygenated tumour cells could be fuelled by exogenous lactate produced from glycolysis. We employed a multi-scale approach that integrates multi-agent modelling, diffusion-reaction, stoichiometric equations, and Boolean networks to study metabolic cooperation between hypoxic and oxygenated cells exposed to varying oxygen, nutrient, and inhibitor concentrations. The results show that the cooperation reduces the depletion of environmental glucose, resulting in an overall advantage of using aerobic glycolysis. In addition, the oxygen level was found to be decreased by symbiosis, promoting a further shift towards anaerobic glycolysis. However, the oxygenated and hypoxic populations may gradually reach quasi-equilibrium. A sensitivity analysis using Latin hypercube sampling and partial rank correlation shows that the symbiotic dynamics depends on properties of the specific cell such as the minimum glucose level needed for glycolysis. Our results suggest that strategies that block glucose transporters may be more effective to reduce tumour growth than those blocking lactate intake transporters.

Immune Features of Tumor Microenvironment: A Genetic Spotlight

A tumor represents a highly intricate tissue entity, characterized by an exceptionally complex microenvironment that starkly contrasts with the typical physiological surroundings of healthy tissues. Within this tumor microenvironment (TME), every component and factor assume paramount importance in the progression of malignancy and exerts a pivotal influence on a patient's clinical outcome. One of the remarkable aspects of the TME is its remarkable heterogeneity, not only across different types of cancers but even within the same histological category of tumors. In-depth research has illuminated the intricate interplay between specific immune cells and molecules and the dynamic characteristics of the TME. Recent investigations have yielded compelling evidence that several mutations harbored by tumor cells possess the capacity to instigate substantial alterations in the TME. These mutations, often acting as drivers of tumorigenesis, can orchestrate a cascade of events that remodel the TME, thereby influencing crucial aspects of cancer behavior, including its invasiveness, immune evasion, and response to therapies. It is within this nuanced context that the present study endeavors to provide a concise yet comprehensive summary of how specific mutations, within the genetic landscape of cancer cells, can instigate profound changes in TME features. By elucidating the intricate relationship between genetic mutations and the TME, this research aims to contribute to a deeper understanding of cancer biology. Ultimately, the knowledge gained from this study holds the potential to inform the development of more targeted and effective treatments, thereby offering new hope to patients grappling with the complexities of cancer.

Mitochondrial glutamate transporter SLC25A22 uni-directionally export glutamate for metabolic rewiring in radioresistant glioblastoma

Glioblastoma Multiforme (GBM) is a malignant primary brain tumor. Radiotherapy, one of the standard treatments for GBM patients, could induce GBM radioresistance via rewiring cellular metabolism. However, the precise mechanism attributing to GBM radioresistance or targeting strategies to overcome GBM radioresistance are lacking. Here, we demonstrate that SLC25A22, a mitochondrial bi-directional glutamate transporter, is upregulated and showed uni-directionality from mitochondria to cytosol in radioresistant GBM cells, resulting in accumulating cytosolic glutamate. However, mitochondrial glutaminolysis-mediated TCA cycle metabolites and OCR are maintained constantly. The accumulated cytosolic glutamate enhances the glutathione (GSH) production and proline synthesis in radioresistant GBM cells. Increased GSH protects cells against ionizing radiation (IR)-induced reactive oxygen species (ROS) whereas increased proline, a rate-limiting substrate for collagen biosynthesis, induces extracellular matrix (ECM) remodeling, leading to GBM invasive phenotypes. Finally, we discover that genetic inhibition of SLC25A22 using miR-184 mimic decreases GBM radioresistance and aggressiveness both in vitro and in vivo. Collectively, our study suggests that SLC25A22 upregulation confers GBM radioresistance by rewiring glutamate metabolism, and SLC25A22 could be a significant therapeutic target to overcome GBM radioresistance.

Heterocyclic and non-heterocyclic arena of monocarboxylate transporter inhibitors to battle tumorigenesis

Monocarboxylate transporters (MCTs) have gained significant attention in cancer research due to their critical role in tumour metabolism. MCTs are legends for transporting lactate molecules in cancer cells, an oncometabolite and waste product of glycolysis, acting as an indispensable factor of tumour proliferation. Targeting MCTs with inhibitors has emerged as a promising strategy to combat tumorigenesis. This article summarizes the most recent research on MCT inhibitors in preventing carcinogenesis, covering both heterocyclic and non-heterocyclic compounds. Heterocyclic and non-heterocyclic compounds such as pteridine, pyrazole, indole, flavonoids, coumarin derivatives and cyanoacetic acid derivatives have been reported as potent MCT inhibitors. We examine the molecular underpinnings of MCTs in cancer metabolism, the design and synthesis of heterocyclic and non-heterocyclic MCT inhibitors, their impact on tumour cells and the microenvironment and their potential as therapeutic agents. Moreover, we explore the challenges associated with MCT inhibitor development and propose future directions for advancing this field. This write-up aims to provide researchers, scientists and clinicians with a comprehensive understanding of the heterocyclic and non-heterocyclic MCT inhibitors and their potential in combating tumorigenesis.

The immunometabolic ecosystem in cancer

Our increased understanding of how key metabolic pathways are activated and regulated in malignant cells has identified metabolic vulnerabilities of cancers. Translating this insight to the clinics, however, has proved challenging. Roadblocks limiting efficacy of drugs targeting cancer metabolism may lie in the nature of the metabolic ecosystem of tumors. The exchange of metabolites and growth factors between cancer cells and nonmalignant tumor-resident cells is essential for tumor growth and evolution, as well as the development of an immunosuppressive microenvironment. In this Review, we will examine the metabolic interplay between tumor-resident cells and how targeted inhibition of specific metabolic enzymes in malignant cells could elicit pro-tumorigenic effects in non-transformed tumor-resident cells and inhibit the function of tumor-specific T cells. To improve the efficacy of metabolism-targeted anticancer strategies, a holistic approach that considers the effect of metabolic inhibitors on major tumor-resident cell populations is needed.

Effects of Lactate Transport Inhibition by AZD3965 in Muscle-Invasive Urothelial Bladder Cancer

The Warburg Effect is characterized by high rates of glucose uptake and lactate production. Monocarboxylate transporters (MCTs) are crucial to avoid cellular acidosis by internal lactate accumulation, being largely overexpressed by cancer cells and associated with cancer aggressiveness. The MCT1-specific inhibitor AZD3965 has shown encouraging results in different cancer models. However, it has not been tested in urothelial bladder cancer (UBC), a neoplasm where rates of recurrence, progression and platinum-based resistance are generally elevated. We used two muscle-invasive UBC cell lines to study AZD3965 activity regarding lactate production, UBC cells' viability and proliferation, cell cycle profile, and migration and invasion properties. An "in vivo" assay with the chick chorioallantoic membrane model was additionally performed, as well as the combination of the compound with cisplatin. AZD3965 demonstrated anticancer activity upon low levels of MCT4, while a general lack of sensitivity was observed under MCT4 high expression. Cell viability, proliferation and migration were reduced, cell cycle was arrested, and tumor growth "in vivo" was inhibited. The compound sensitized these MCT4-low-expressing cells to cisplatin. Thus, AZD3965 seems to display anticancer properties in UBC under a low MCT4-expression setting, but additional studies are necessary to confirm AZD3965 activity in this cancer model.

Targeting cellular metabolism in head and neck cancer precision medicine era: A promising strategy to overcome therapy resistance

Head and neck squamous cell carcinoma (HNSCC) is among the most prevalent cancer worldwide, with the most severe impact on quality of life of patients. Despite the development of multimodal therapeutic approaches, the clinical outcomes of HNSCC are still unsatisfactory, mainly caused by relatively low responsiveness to treatment and severe drug resistance. Metabolic reprogramming is currently considered to play a pivotal role in anticancer therapeutic resistance. This review aimed to define the specific metabolic programs and adaptations in HNSCC therapy resistance. An extensive literature review of HNSCC was conducted via the PubMed including metabolic reprogramming, chemo- or immune-therapy resistance. Glucose metabolism, fatty acid metabolism, and amino acid metabolism are closely related to the malignant biological characteristics of cancer, anti-tumor drug resistance, and adverse clinical results. For HNSCC, pyruvate, lactate and almost all lipid categories are related to the occurrence and maintenance of drug resistance, and targeting amino acid metabolism can prevent tumor development and enhance the response of drug-resistant tumors to anticancer therapy. This review will provide a better understanding of the altered metabolism in therapy resistance of HNSCC and promote the development of new therapeutic strategies against HNSCC, thereby contribute to a more efficacious precision medicine.

The release of zearalenone-induced heterophil extracellular traps in chickens is associated with autophagy, glycolysis, PAD enzyme, and P2X1 receptor

Zearalenone (ZEA) is produced mainly by fungi belonging to genus Fusarium in foods and feeds. Heterophil extracellular traps (HETs) are a novel defense mechanism of chicken innate immunity involving activated heterophils. However, the conditions and requirements for ZEA-triggered HET release remain unknown. In this study, immunostaining analysis demonstrated that ZEA-triggered extracellular fibers were composed of histone and elastase assembled on DNA skeleton, showing that ZEA can induce the formation of HETs. Further experiments indicated that ZEA-induced HET release was concentration-dependent (ranging from 20 to 80 μM ZEA) and time-dependent (ranging from 30 to 180 min). Moreover, in 80 μM ZEA-exposed chicken heterophils, reactive oxygen species (ROS) level, catalase (CAT), superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and glutathione (GSH) content were increased. Simultaneously, ZEA at 80 μM activated ERK and p38 MAPK signaling pathways by increasing the phosphorylation level of ERK and p38 proteins. Pharmacological inhibition assays revealed that blocking nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, ERK, and p38 mitogen-activated protein kinase (MAPK) reduced ZEA-induced ROS levels but had no impact on HET formation. Furthermore, immunostaining analysis indicated that the heterophil underwent the formation of autophagosome based on being stained with LC3B. The pharmacological inhibition assays demonstrated that rapamycin-, wortmannin-, and 3-methyladenine (3-MA)-treatments modulated ZEA-triggered HET formation, indicating that heterophil autophagy played a key role in ZEA-induced HET formation. Further studies on energy metabolism showed that inhibition of lactate/glucose transport, hexokinase-2 (HK-2), fructose-2,6-biphosphatase 3 (PFKFB3) in glycolysis abated ZEA-induced HETs, implying that glycolysis was one of the factors influencing the ZEA-induced HET formation. Besides, inhibition of the peptidylarginine deiminase (PAD) enzyme and P2X1 significantly reduced the ZEA-induced HET formation. In conclusion, we demonstrated that ZEA-triggered HET formation, which was associated with glycolysis, autophagy, PAD enzyme, and P2X1 receptor activation, providing valuable insight into the negative effect of ZEA on chicken innate immunity.

Evaluating [18F]FDG and [18F]FLT Radiotracers as Biomarkers of Response for Combined Therapy Outcome in Triple-Negative and Estrogen-Receptor-Positive Breast Cancer Models

Breast cancer (BC) is the most frequent cancer and the second leading cause of death in women. A typical feature of BC cells is the metabolic shift toward increased glycolysis, which has become an interesting therapeutic target for metabolic drugs such as metformin (MET). Recently, the administration of the antihypertensive syrosingopine (SYRO) in combination with MET has shown a synergistic effect toward a variety of cancers. However, a fundamental need remains, which is the development of in vivo biomarkers that are able to detect early clinical response. In this study, we exploited a triple-negative murine BC cell line (4T1) and a metastatic ER+ murine BC cell line (TS/A) in order to investigate, in vivo, the early response to treatment, based on MET and/or SYRO administration, evaluating [18F]FDG and [18F]FLT as potential biomarkers via PET/CT. The study provides evidence that SYRO plus MET has a synergistic effect on tumor growth inhibition in both 4T1 and TS/A experimental models and has showed the highest efficacy on the TNBC xenograft mice (4T1) via the expression reduction in the lactate transporter MCT4 and in the epithelial-mesenchymal transition biomarker Snail, promoting its potential application in therapy settings. In addition, the selective reduction in the [18F]FLT tumor uptake (at 7 dd), observed in the SYRO plus MET treated mice in comparison with the vehicle group, suggests that this radiotracer could be potentially used as a biomarker for the early detection of therapy response, in both evaluated xenografts models.

Lactate metabolic pathway regulates tumor cell metastasis and its use as a new therapeutic target

Abnormal energy metabolism is one of the ten hallmarks of tumors, and tumor cell metabolism provides energy and a suitable microenvironment for tumorigenesis and metastasis. Tumor cells can consume large amounts of glucose and produce large amounts of lactate through glycolysis even in the presence of oxygen, a process called aerobic glycolysis, also known as the Warburg effect. Lactate is the end product of the aerobic glycolysis. Lactate dehydrogenase A (LDHA), which is highly expressed in cancer cells, promotes lactate production and transports lactate to the tumor microenvironment and is taken up by surrounding stromal cells under the action of monocarboxylate transporter 1/4 (MCT1/4), which in turn influences the immune response and enhances the invasion and metastasis of cancer cells. Therapeutic strategies targeting lactate metabolism have been intensively investigated, focusing on its metastasis-promoting properties and various target inhibitors; AZD3965, an MCT1 inhibitor, has entered phase I clinical trials, and the LDHA inhibitor N-hydroxyindole (NHI) has shown cancer therapeutic activity in pre-clinical studies. Interventions targeting lactate metabolism are emerging as a promising option for cancer therapy, with chemotherapy or radiotherapy combined with lactate-metabolism-targeted drugs adding to the effectiveness of cancer treatment. Based on current research, this article outlines the role of lactate metabolism in tumor metastasis and the potential value of inhibitors targeting lactate metabolism in cancer therapy.

Myeloid-derived suppressor cells impair CD4+ T cell responses during chronic Staphylococcus aureus infection via lactate metabolism

Staphylococcus aureus is an important cause of chronic infections resulting from the failure of the host to eliminate the pathogen. Effective S. aureus clearance requires CD4+ T cell-mediated immunity. We previously showed that myeloid-derived suppressor cells (MDSC) expand during staphylococcal infections and support infection chronicity by inhibiting CD4+ T cell responses. The aim of this study was to elucidate the mechanisms underlying the suppressive effect exerted by MDSC on CD4+ T cells during chronic S. aureus infection. It is well known that activated CD4+ T cells undergo metabolic reprogramming from oxidative metabolism to aerobic glycolysis to meet their increased bioenergetic requirements. In this process, pyruvate is largely transformed into lactate by lactate dehydrogenase with the concomitant regeneration of NAD+, which is necessary for continued glycolysis. The by-product lactate needs to be excreted to maintain the glycolytic flux. Using SCENITH (single-cell energetic metabolism by profiling translation inhibition), we demonstrated here that MDSC inhibit CD4+ T cell responses by interfering with their metabolic activity. MDSC are highly glycolytic and excrete large amount of lactate in the local environment that alters the transmembrane concentration gradient and prevent removal of lactate by activated CD4+ T. Accumulation of endogenous lactate impedes the regeneration of NAD+, inhibit NAD-dependent glycolytic enzymes and stop glycolysis. Together, the results of this study have uncovered a role for metabolism on MDSC suppression of CD4+ T cell responses. Thus, reestablishment of their metabolic activity may represent a mean to improve the functionality of CD4+ T cells during chronic S. aureus infection.

Pyruvate-conjugation of PEGylated liposomes for targeted drug delivery to retinal photoreceptors

Despite several promising candidates, there is a paucity of drug treatments available for patients suffering from retinal diseases. An important reason for this is the lack of suitable delivery systems that can achieve sufficiently high drug uptake in the retina and its photoreceptors. A promising and versatile method for drug delivery to specific cell types involves transporter-targeted liposomes, i.e., liposomes surface-coated with substrates for transporter proteins highly expressed on the target cell. We identified strong lactate transporter (monocarboxylate transporter, MCT) expression on photoreceptors as a potential target for drug delivery vehicles. To evaluate MCT suitability for drug targeting, we used PEG-coated liposomes and conjugated these with different monocarboxylates, including lactate, pyruvate, and cysteine. Monocarboxylate-conjugated and dye-loaded liposomes were tested on both human-derived cell-lines and murine retinal explant cultures. We found that liposomes conjugated with pyruvate consistently displayed higher cell uptake than unconjugated liposomes or liposomes conjugated with lactate or cysteine. Pharmacological inhibition of MCT1 and MCT2 reduced internalization, suggesting an MCT-dependent uptake mechanism. Notably, pyruvate-conjugated liposomes loaded with the drug candidate CN04 reduced photoreceptor cell death in the murine rd1 retinal degeneration model while free drug solutions could not achieve the same therapeutic effect. Our study thus highlights pyruvate-conjugated liposomes as a promising system for drug delivery to retinal photoreceptors, as well as other neuronal cell types displaying high expression of MCT-type proteins.

Inhibition of lactate transport by MCT-1 blockade improves chimeric antigen receptor T-cell therapy against B-cell malignancies

BACKGROUND

Chimeric antigen receptor (CAR) T cells have shown remarkable results against B-cell malignancies, but only a minority of patients have long-term remission. The metabolic requirements of both tumor cells and activated T cells result in production of lactate. The export of lactate is facilitated by expression of monocarboxylate transporter (MCTs). CAR T cells express high levels of MCT-1 and MCT-4 on activation, while certain tumors predominantly express MCT-1.

METHODS

Here, we studied the combination of CD19-specific CAR T-cell therapy with pharmacological blockade of MCT-1 against B-cell lymphoma.

RESULTS

MCT-1 inhibition with small molecules AZD3965 or AR-C155858 induced CAR T-cell metabolic rewiring but their effector function and phenotype remained unchanged, suggesting CAR T cells are insensitive to MCT-1 inhibition. Moreover, improved cytotoxicity in vitro and antitumoral control on mouse models was found with the combination of CAR T cells and MCT-1 blockade.

CONCLUSION

This work highlights the potential of selective targeting of lactate metabolism via MCT-1 in combination with CAR T cells therapies against B-cell malignancies.

Lactate promotes neuronal differentiation of SH-SY5Y cells by lactate-responsive gene sets through NDRG3-dependent and -independent manners

Lactate serves as the major glucose alternative to an energy substrate in the brain. Lactate level is increased in the fetal brain from the middle stage of gestation, indicating the involvement of lactate in brain development and neuronal differentiation. Recent reports show that lactate functions as a signaling molecule to regulate gene expression and protein stability. However, the roles of lactate signaling in neuronal cells remain unknown. Here, we showed that lactate promotes the all stages of neuronal differentiation of SH-SY5Y and Neuro2A, human and mouse neuroblastoma cell lines, characterized by increased neuronal marker expression and the rates of neurites extension. Transcriptomics revealed many lactate-responsive genes sets such as SPARCL1 in SH-SY5Y, Neuro2A, and primary embryonic mouse neuronal cells. The effects of lactate on neuronal function were mainly mediated through monocarboxylate transporters 1 (MCT1). We found that NDRG family member 3 (NDRG3), a lactate-binding protein, was highly expressed and stabilized by lactate treatment during neuronal differentiation. Combinative RNA-seq of SH-SY5Y with lactate treatment and NDRG3 knockdown shows that the promotive effects of lactate on neural differentiation are regulated through NDRG3-dependent and independent manners. Moreover, we identified TEA domain family member 1 (TEAD1) and ETS-related transcription factor 4 (ELF4) are the specific transcription factors that are regulated by both lactate and NDRG3 in neuronal differentiation. TEAD1 and ELF4 differently affect the expression of neuronal marker genes in SH-SY5Y cells. These results highlight the biological roles of extracellular and intracellular lactate as a critical signaling molecule that modifies neuronal differentiation.

Dual-inhibition of lactate metabolism and Prussian blue-mediated radical generation for enhanced chemodynamic therapy and antimetastatic effect

Numerous research studies have proved that lactate is pivotal in tumor proliferation, metastasis, and recurrence, so disrupting the lactate metabolism in the tumor microenvironment (TME) has become one of the effective methods of tumor treatment. Herein, we have developed a versatile nanoparticle (HCLP NP) based on hollow Prussian blue (HPB) as the functional carrier for loading α-cyano-4-hydroxycinnamate (CHC), and lactate oxidase (LOD), followed by coating with polyethylene glycol to enhance chemodynamic therapy (CDT) and the antimetastatic effect of cancer. The obtained HCLP NPs would be degraded under endogenous mild acidity within the TME to simultaneously release CHC and LOD. CHC inhibits the expression of monocarboxylate transporter 1 in tumors, thereby interrupting the uptake of lactate from the outside and alleviating tumor hypoxia by reducing lactate aerobic respiration. Meanwhile, the released LOD can catalyze the decomposition of lactate into hydrogen peroxide, further enhancing the efficacy of CDT by generating plenty of toxic reactive oxygen species through the Fenton reaction. The strong absorbance at about 800 nm endows HCLP NPs with excellent photoacoustic imaging properties. Both in vitro and in vivo studies have demonstrated that HCLP NPs can inhibit tumor growth and metastasis, providing a new possibility for tumor therapy.

Targeting monocarboxylate transporters (MCTs) in cancer: How close are we to the clinics?

As a result of metabolic reprogramming, cancer cells display high rates of glycolysis, causing an excess production of lactate along with an increase in extracellular acidity. Proton-linked monocarboxylate transporters (MCTs) are crucial in the maintenance of this metabolic phenotype, by mediating the proton-coupled lactate flux across cell membranes, also contributing to cancer cell pH regulation. Among the proteins codified by the SLC16 gene family, MCT1 and MCT4 isoforms are the most explored in cancers, being overexpressed in many cancer types, from solid tumours to haematological malignancies. Similarly to what occurs in particular physiological settings, MCT1 and MCT4 are able to mediate lactate shuttles among cancer cells, and also between cancer and stromal cells in the tumour microenvironment. This form of metabolic cooperation is responsible for important cancer aggressiveness features, such as cell proliferation, survival, angiogenesis, migration, invasion, metastasis, immune tolerance and therapy resistance. The growing understanding of MCT functions and regulation is offering a new path to the design of novel inhibitors that can be foreseen in clinical practices. This review provides an overview of the role of MCT isoforms in cancer and summarizes the recent advances in their pharmacological targeting, highlighting the potential of new potent and selective MCT1 and/or MCT4 inhibitors in cancer therapeutics, and anticipating its inclusion in clinical practice.

Intracellular glucose starvation inhibits osteogenic differentiation in human periodontal ligament cells

BACKGROUND

Periodontal ligament cells (PDLCs), as mesenchymal cells in the oral cavity, are closely linked to periodontal tissue regeneration. However, the effect of local glucose deficiency on periodontal tissue regeneration, such as immediately post-surgery, remains unknown.

OBJECTIVE

In the present study, we investigated the effect of a low-glucose environment on the proliferation and osteogenic differentiation of PDLCs.

MATERIALS AND METHODS

We used media with five glucose concentrations (100, 75, 50, 25, and 0 mg/dL) and focused on the effects of a low-glucose environment on the proliferation, osteogenic differentiation, and autophagy of PDLCs. Additionally, we focused on changes in lactate production in a low-glucose environment and investigated the involvement of lactate with AZD3965, a monocarboxylate transporter-1 (MCT-1) inhibitor.

RESULTS

The low-glucose environment inhibited PDLCs proliferation, migration, and osteogenic differentiation, and induced the expression of the autophagy-related factors LC3 and p62. Lactate and ATP production were decreased under low-glucose conditions. The addition of AZD3965 (MCT-1 inhibitor) in normal glucose conditions caused a similar trend as in low-glucose conditions on PDLCs.

CONCLUSION

Our results suggest lactate production through glucose metabolism in the osteogenic differentiation of PDLCs. A low-glucose environment decreased lactate production, inhibiting cell proliferation, migration, and osteogenic differentiation and inducing autophagy in PDLCs.

Monocarboxylate transporters facilitate succinate uptake into brown adipocytes

Uptake of circulating succinate by brown adipose tissue (BAT) and beige fat elevates whole body energy expenditure, counteracts obesity, and antagonizes systemic tissue inflammation in mice. The plasma membrane transporters that facilitate succinate uptake in these adipocytes remain undefined. Here we elucidate a mechanism underlying succinate import into BAT via monocarboxylate transporters (MCTs). We show that succinate transport is strongly dependent on the proportion of it present in the monocarboxylate form. MCTs facilitate monocarboxylate succinate uptake, which is promoted by alkalinization of the cytosol driven by adrenoreceptor stimulation. In brown adipocytes, we show that MCT1 primarily facilitates succinate import, however other members of the MCT family can partially compensate and fulfill this role in the absence of MCT1. In mice, we show that acute pharmacological inhibition of MCT1 and 2 decreases succinate uptake into BAT. Conversely, congenital genetic depletion of MCT1 alone has little effect on BAT succinate uptake, indicative of additional transport mechanisms with high capacity in vivo . In sum, we define a mechanism of succinate uptake in BAT that underlies its protective activity in mouse models of metabolic disease.

Advances in the study of aerobic glycolytic effects in resistance to radiotherapy in malignant tumors

Aerobic glycolysis is a metabolic mode of tumor cells different from normal cells that plays an important role in tumor proliferation and distant metastasis. Radiotherapy has now become a routine and effective treatment for many malignancies, however, resistance to radiotherapy remains a major challenge in the treatment of malignant tumors. Recent studies have found that the abnormal activity of the aerobic glycolysis process in tumor cells is most likely involved in regulating chemoresistance and radiation therapy resistance in malignant tumors. However, research on the functions and mechanisms of aerobic glycolysis in the molecular mechanisms of resistance to radiotherapy in malignant tumors is still in its early stages. This review collects recent studies on the effects of aerobic glycolysis and radiation therapy resistance in malignant tumors, to further understand the progress in this area. This research may more effectively guide the clinical development of more powerful treatment plans for radiation therapy resistant subtypes of cancer patients, and take an important step to improve the disease control rate of radiation therapy resistant subtypes of cancer patients.

Immunohistochemical evaluation and prognostic value of monocarboxylate transporter 1 (MCT1) and 4 (MCT4) in T-cell non-Hodgkin lymphoma

Tumor cells often exhibit the Warburg effect, wherein, they preferentially undergo glycolysis over oxidative phosphorylation for energy production. Monocarboxylate transporter 1 (MCT1) and 4 (MCT4) are critical symporters mediating lactate efflux and preventing intracellular acidification during tumor growth. Numerous studies have focused on inhibiting MCT1 or MCT4 in various cancers. However, its role in T-cell lymphoma (TCL) is not yet investigated owing to the low incidence of TCL. This study was designed to investigate the expression of MCT1/MCT4 in patients with TCL and determine their prognostic value in this cancer. We performed immunohistochemistry to evaluate the expression level of MCT1/MCT4 in 38 TCL tissue samples and then compared their expression among different TCL subgroups, which were formed based on different clinical characteristics. Survival analysis was performed to evaluate the relationship between MCT1/MCT4 expression and both overall survival (OS) and progression-free survival (PFS). Our results revealed that MCT1 and MCT4 expression was significantly increased in TCL tissues compared to the control group. In addition, increased MCT1 expression associated with the female sex, advanced disease stage, increased serum LDH, Ki-67 at ≥ 50%, and intermediate or high-risk groups as categorized by the International Prognostic Index (IPI) score. We also found that increased MCT1 expression may be associated with reduced OS and PFS. In conclusion, MCT1 and MCT4 are overexpressed in patients with TCL and may predict poor prognosis. MCT1 inhibition might be a novel treatment strategy for TCL, and further preclinical trials are required.

Tumor hypoxia: From basic knowledge to therapeutic implications

Diminished oxygen availability, termed hypoxia, within solid tumors is one of the most common characteristics of cancer. Hypoxia shapes the landscape of the tumor microenvironment (TME) into a pro-tumorigenic and pro-metastatic niche through arrays of pathological alterations such as abnormal vasculature, altered metabolism, immune-suppressive phenotype, etc. In addition, emerging evidence suggests that limited efficacy or the development of resistance towards antitumor therapy may be largely due to the hypoxic TME. This review will focus on summarizing the knowledge about the molecular machinery that mediates the hypoxic cellular responses and adaptations, as well as highlighting the effects and consequences of hypoxia, especially for angiogenesis regulation, cellular metabolism alteration, and immunosuppressive response within the TME. We also outline the current advances in novel therapeutic implications through targeting hypoxia in TME. A deep understanding of the basics and the role of hypoxia in the tumor will help develop better therapeutic avenues in cancer treatment.

Novel insight into metabolic reprogrammming in cancer radioresistance: A promising therapeutic target in radiotherapy

Currently, cancer treatment mainly consists of surgery, radiotherapy, chemotherapy, immunotherapy, and molecular targeted therapy, of which radiotherapy is one of the major pillars. However, the occurrence of radioresistance largely limits its therapeutic effect. Metabolic reprogramming is an important hallmark in cancer progression and treatment resistance. In radiotherapy, DNA breakage is the major mechanism of cell damage, and in turn, cancer cells are prone to increase the metabolic flux of glucose, glutamine, serine, arginine, fatty acids etc., thus providing sufficient substrates and energy for DNA damage repair. Therefore, studying the linkage between metabolic reprogramming and cancer radioresistance may provide new ideas for improving the efficacy of tumor therapy. This review mainly focuses on the role of metabolic alterations, including glucose, amino acid, lipid, nucleotide and other ion metabolism, in radioresistance, and proposes possible therapeutic targets to improve the efficacy of cancer radiotherapy.

Antitumor effects of lactate transport inhibition on esophageal adenocarcinoma cells

As a consequence of altered glucose metabolism, cancer cell intake is increased, producing large amounts of lactate which is pumped out the cytosol by monocarboxylate transporters (MCTs). MCT 1 and MCT4 are frequently overexpressed in tumors, and recently, MCT inhibition has been reported to exert antineoplastic effects. In the present study, MCT1 and MCT4 levels were assessed in esophageal adenocarcinoma (EAC) cells and the effects of the MCT-1 selective inhibitor AZD3965, hypoxia, and a glucose overload were evaluated in vitro. Two EAC cell lines (OE33 and OACM5.1C) were treated with AZD3965 (10-100 nM) under different conditions (normoxia/hypoxia) and also different glucose concentrations, and parameters of cytotoxicity, oxidative stress, intracellular pH (pHi), and lactate levels were evaluated. MCT1 was present in both cell lines whereas MCT4 was expressed in OE33 cells and only in a small proportion of OACM5.1C cells. Glucose addition did not have any effect on apoptosis nor cell proliferation. AZD3965 increased apoptosis and reduced proliferation of OACM5.1C cells, effects which were abrogated when cells were growing in hypoxia. MCT1 inhibition increased intracellular lactate levels in all the cells evaluated, but this increase was higher in cells expressing only MCT1 and did not affect oxidative stress. AZD3965 induced a decrease in pHi of cells displaying low levels of MCT4 and also increased the sodium/hydrogen exchanger 1 (NHE-1) expression on these cells. These data provide in vitro evidence supporting the potential of MCT inhibitors as novel antineoplastic drugs for EAC and highlight the importance of achieving a complete MCT inhibition.

PI3K/AKT/mTOR pathway, hypoxia, and glucose metabolism: Potential targets to overcome radioresistance in small cell lung cancer

Small cell lung cancer (SCLC) is a highly aggressive tumor type for which limited therapeutic progress has been made. Platinum-based chemotherapy with or without thoracic radiotherapy remains the backbone of treatment, but most patients with SCLC acquire therapeutic resistance. Given the need for more effective therapies, better elucidation of the molecular pathogenesis of SCLC is imperative. The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway is frequently activated in SCLC and strongly associated with resistance to ionizing radiation in many solid tumors. This pathway is an important regulator of cancer cell glucose metabolism, and its activation probably effects radioresistance by influencing bioenergetic processes in SCLC. Glucose metabolism has three main branches-aerobic glycolysis, oxidative phosphorylation, and the pentose phosphate pathway-involved in radioresistance. The interaction between the PI3K/AKT/mTOR pathway and glucose metabolism is largely mediated by hypoxia-inducible factor 1 (HIF-1) signaling. The PI3K/AKT/mTOR pathway also influences glucose metabolism through other mechanisms to participate in radioresistance, including inhibiting the ubiquitination of rate-limiting enzymes of the pentose phosphate pathway. This review summarizes our understanding of links among the PI3K/AKT/mTOR pathway, hypoxia, and glucose metabolism in SCLC radioresistance and highlights promising research directions to promote cancer cell death and improve the clinical outcome of patients with this devastating disease.

Targeting cancer-specific metabolic pathways for developing novel cancer therapeutics

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

Effects of metabolic cancer therapy on tumor microenvironment

Targeting tumor metabolism for cancer therapy is an old strategy. In fact, historically the first effective cancer therapeutics were directed at nucleotide metabolism. The spectrum of metabolic drugs considered in cancer increases rapidly - clinical trials are in progress for agents directed at glycolysis, oxidative phosphorylation, glutaminolysis and several others. These pathways are essential for cancer cell proliferation and redox homeostasis, but are also required, to various degrees, in other cell types present in the tumor microenvironment, including immune cells, endothelial cells and fibroblasts. How metabolism-targeted treatments impact these tumor-associated cell types is not fully understood, even though their response may co-determine the overall effectivity of therapy. Indeed, the metabolic dependencies of stromal cells have been overlooked for a long time. Therefore, it is important that metabolic therapy is considered in the context of tumor microenvironment, as understanding the metabolic vulnerabilities of both cancer and stromal cells can guide new treatment concepts and help better understand treatment resistance. In this review we discuss recent findings covering the impact of metabolic interventions on cellular components of the tumor microenvironment and their implications for metabolic cancer therapy.

Targeting Na-H exchanger 1 overcomes nuclear factor kappa B-mediated tumor resistance to radiotherapy

Intrinsic or acquired radioresistance often limits the efficacy of radiation therapy (RT), thereby leading to local control failure. Cancerous cells have abnormal pH dynamics due to high metabolic demands, but it is unclear how pH dynamics contribute to radioresistance. In this study, we investigated the role of Na-H exchange 1 (NHE1), the major intracellular pH (pH_i) regulator, in RT response. We observed that RT increased NHE1 expression and modulated pH_i in MDA-MB-231 human breast cancer cells. When combined with RT, pharmacological NHE1 inhibition by 5-(N-Ethyl-N-isopropyl)amiloride (EIPA) reduced pH_i and clonogenic survival. EIPA attenuated radiation-damaged DNA repair, increasing G2/M cell cycle arrest. The combination of EIPA and RT increased apoptotic cell death while decreasing phosphorylation of NF-κB p65. Similarly, the knockdown of NHE1 increased radiosensitivity with lower pH_i and increased apoptosis. Consistent with in vitro data, the EIPA plus RT inhibited the growth of MDA-MB-231 xenograft tumors in mice to a greater extent than either EIPA or RT alone. EIPA abrogated the RT-induced increase in NHE1 and phospho-NF-κB p65 expression in tumor tissues. Such coincidence of increased NHE1 level, pH_i, and NF-κB activation was also found in radioresistant MDA-MB-231 cells, which were reversed by EIPA treatment. Bioinformatics analysis of RNA sequencing data revealed that inhibiting NHE1 reversed three core gene networks that were up-regulated in radioresistant cells and correlated with high NHE1 expression in patient samples: NF-κB, senescence, and extracellular matrix. Taken together, our findings suggest that NHE1 contributes to RT resistance via NF-κB-mediated signaling networks, and NHE1 may be a promising target for improving RT outcomes.

Lactic Acidosis in Patients with Solid Cancer

Significance: Cancer-associated tissue-specific lactic acidosis stimulates and mediates tumor invasion and metastasis and is druggable. Rarely, malignancy causes systemic lactic acidosis, the role of which is poorly understood. Recent Advances: The understanding of the role of lactate has shifted dramatically since its discovery. Long recognized as only a waste product, lactate has become known as an alternative metabolism substrate and a secreted nutrient that is exchanged between the tumor and the microenvironment. Tissue-specific lactic acidosis is targeted to improve the host body's anticancer defense and serves as a tool that allows the targeting of anticancer compounds. Systemic lactic acidosis is associated with poor survival. In patients with solid cancer, systemic lactic acidosis is associated with an extremely poor prognosis, as revealed by the analysis of 57 published cases in this study. Although it is considered a pathology worth treating, targeting systemic lactic acidosis in patients with solid cancer is usually inefficient. Critical Issues: Research gaps include simple questions, such as the unknown nuclear pH of the cancer cells and its effects on chemotherapy outcomes, pH sensitivity of glycosylation in cancer cells, in vivo mechanisms of response to acidosis in the absence of lactate, and overinterpretation of in vitro results that were obtained by using cells that were not preadapted to acidic environments. Future Directions: Numerous metabolism-targeting anticancer compounds induce lactatemia, lactic acidosis, or other types of acidosis. Their potential to induce acidic environments is largely overlooked, although the acidosis might contribute to a substantial portion of the observed clinical effects. Antioxid. Redox Signal. 37, 1130-1152.

Zinc oxide nanoparticles (ZnO-NPs) exhibit immune toxicity to crucian carp (Carassius carassius) by neutrophil extracellular traps (NETs) release and oxidative stress

Zinc oxide nanoparticles (ZnO-NPs) are widely used in sunscreens, cosmetics, paint, construction materials, and other products. ZnO-NPs released into the environment can harm aquatic creatures and pose a health risk to humans through the food chain. ZnO-NPs are toxic to fish, but there are few reports on its immunotoxicity on crucian carp (Carassius carassius). In this study, ZnO-NPs increased the biochemical indexes of the liver in serum, including aspartate aminotransferase (AST) and alanine aminotransferase (ALT). In histopathological observation, many inflammatory cells were filled in the liver's central vein stimulated by ZnO-NPs. Furthermore, ZnO-NPs could increase malondialdehyde (MDA) level, lessen superoxide dismutase (SOD) level, and elevate the level of neutrophil extracellular traps (NETs). However, deoxyribonuclease I (DNase I) alleviated all biochemical indexes and histopathological changes. Immunofluorescence in vitro confirmed that NETs were composed of citrullinated histone 3, myeloperoxidase, and neutrophil elastase. ZnO-NPs-increased NETs were dependent on reactive oxygen species (ROS) and nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase and were also related to partial processes of glycolysis. Our study confirms that ZnO-NPS has a toxic effect on the liver of crucian carp. DNase I can prevent liver damage caused by ZnO-NPs, which provides a new insight into the immunotoxicity of ZnO-NPs to fish.

Targeting Glucose Metabolism Enzymes in Cancer Treatment: Current and Emerging Strategies

Simple Summary

Reprogramming of glucose metabolism is a hallmark of cancer and can be targeted by therapeutic agents. Some metabolism regulators, such as ivosidenib and enasidenib, have been approved for cancer treatment. Currently, more advanced and effective glucose metabolism enzyme-targeted anticancer drugs have been developed. Furthermore, some natural products have shown efficacy in killing tumor cells by regulating glucose metabolism, offering novel therapeutic opportunities in cancer. However, most of them have failed to be translated into clinical applications due to low selectivity, high toxicity, and side effects. Recent studies suggest that combining glucose metabolism modulators with chemotherapeutic drugs, immunotherapeutic drugs, and other conventional anticancer drugs may be a future direction for cancer treatment.

Abstract

Reprogramming of glucose metabolism provides sufficient energy and raw materials for the proliferation, metastasis, and immune escape of cancer cells, which is enabled by glucose metabolism-related enzymes that are abundantly expressed in a broad range of cancers. Therefore, targeting glucose metabolism enzymes has emerged as a promising strategy for anticancer drug development. Although several glucose metabolism modulators have been approved for cancer treatment in recent years, some limitations exist, such as a short half-life, poor solubility, and numerous adverse effects. With the rapid development of medicinal chemicals, more advanced and effective glucose metabolism enzyme-targeted anticancer drugs have been developed. Additionally, several studies have found that some natural products can suppress cancer progression by regulating glucose metabolism enzymes. In this review, we summarize the mechanisms underlying the reprogramming of glucose metabolism and present enzymes that could serve as therapeutic targets. In addition, we systematically review the existing drugs targeting glucose metabolism enzymes, including small-molecule modulators and natural products. Finally, the opportunities and challenges for glucose metabolism enzyme-targeted anticancer drugs are also discussed. In conclusion, combining glucose metabolism modulators with conventional anticancer drugs may be a promising cancer treatment strategy.

Targeting mitochondrial metabolism for metastatic cancer therapy

Primary tumors evolve metabolic mechanisms favoring glycolysis for adenosine triphosphate (ATP) generation and antioxidant defenses. In contrast, metastatic cells frequently depend on mitochondrial respiration and oxidative phosphorylation (OxPhos). This reliance of metastatic cells on OxPhos can be exploited using drugs that target mitochondrial metabolism. Therefore, therapeutic agents that act via diverse mechanisms, including the activation of signaling pathways that promote the production of reactive oxygen species (ROS) and/or a reduction in antioxidant defenses may elevate oxidative stress and inhibit tumor cell survival. In this review, we will provide (1) a mechanistic analysis of function-selective extracellular signal-regulated kinase-1/2 (ERK1/2) inhibitors that inhibit cancer cells through enhanced ROS, (2) a review of the role of mitochondrial ATP synthase in redox regulation and drug resistance, (3) a rationale for inhibiting ERK signaling and mitochondrial OxPhos toward the therapeutic goal of reducing tumor metastasis and treatment resistance. Recent reports from our laboratories using metastatic melanoma and breast cancer models have shown the preclinical efficacy of novel and rationally designed therapeutic agents that target ERK1/2 signaling and mitochondrial ATP synthase, which modulate ROS events that may prevent or treat metastatic cancer. These findings and those of others suggest that targeting a tumor's metabolic requirements and vulnerabilities may inhibit metastatic pathways and tumor growth. Approaches that exploit the ability of therapeutic agents to alter oxidative balance in tumor cells may be selective for cancer cells and may ultimately have an impact on clinical efficacy and safety. Elucidating the translational potential of metabolic targeting could lead to the discovery of new approaches for treatment of metastatic cancer.

LDHB Overexpression Can Partially Overcome T Cell Inhibition by Lactic Acid

Accelerated glycolysis leads to secretion and accumulation of lactate and protons in the tumor environment and determines the efficacy of adoptive T cell and checkpoint inhibition therapy. Here, we analyzed effects of lactic acid on different human CD4 T cell subsets and aimed to increase CD4 T cell resistance towards lactic acid. In all CD4 T cell subsets analyzed, lactic acid inhibited metabolic activity (glycolysis and respiration), cytokine secretion, and cell proliferation. Overexpression of the lactate-metabolizing isoenzyme LDHB increased cell respiration and mitigated lactic acid effects on intracellular cytokine production. Strikingly, LDHB-overexpressing cells preferentially migrated into HCT116 tumor spheroids and displayed higher expression of cytotoxic effector molecules. We conclude, that LDHB overexpression might be a promising strategy to increase the efficacy of adoptive T cell transfer therapy.

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.

A small-molecule cocktail promotes mammalian cardiomyocyte proliferation and heart regeneration

Zebrafish and mammalian neonates possess robust cardiac regeneration via the induction of endogenous cardiomyocyte (CM) proliferation, but adult mammalian hearts have very limited regenerative potential. Developing small molecules for inducing adult mammalian heart regeneration has had limited success. We report a chemical cocktail of five small molecules (5SM) that promote adult CM proliferation and heart regeneration. A high-content chemical screen, along with an algorithm-aided prediction of small-molecule interactions, identified 5SM that efficiently induced CM cell cycle re-entry and cytokinesis. Intraperitoneal delivery of 5SM reversed the loss of heart function, induced CM proliferation, and decreased cardiac fibrosis after rat myocardial infarction. Mechanistically, 5SM potentially targets α1 adrenergic receptor, JAK1, DYRKs, PTEN, and MCT1 and is connected to lactate-LacRS2 signaling, leading to CM metabolic switching toward glycolysis/biosynthesis and CM de-differentiation before entering the cell-cycle. Our work sheds lights on the understanding CM regenerative mechanisms and opens therapeutic avenues for repairing the heart.

Metabolic tricks of cancer cells

One of the characteristics of cancer cells important for tumorigenesis is their metabolic plasticity. Indeed, in various stress conditions, cancer cells can reshape their metabolic pathways to support the increased energy request due to continuous growth and rapid proliferation. Moreover, selective pressures in the tumor microenvironment, such as hypoxia, acidosis, and competition for resources, force cancer cells to adapt by complete reorganization of their metabolism. In this review, we highlight the characteristics of cancer metabolism and discuss its clinical significance, since overcoming metabolic plasticity of cancer cells is a key objective of modern cancer therapeutics and a better understanding of metabolic reprogramming may lead to the identification of possible targets for cancer therapy.

Metabolic response to radiation therapy in cancer

Tumor metabolism has emerged as a hallmark of cancer and is involved in carcinogenesis and tumor growth. Reprogramming of tumor metabolism is necessary for cancer cells to sustain high proliferation rates and enhanced demands for nutrients. Recent studies suggest that metabolic plasticity in cancer cells can decrease the efficacy of anticancer therapies by enhancing antioxidant defenses and DNA repair mechanisms. Studying radiation-induced metabolic changes will lead to a better understanding of radiation response mechanisms as well as the identification of new therapeutic targets, but there are few robust studies characterizing the metabolic changes induced by radiation therapy in cancer. In this review, we will highlight studies that provide information on the metabolic changes induced by radiation and oxidative stress in cancer cells and the associated underlying mechanisms.

In Vivo Anticancer Activity of AZD3965: A Systematic Review

Proliferating cancer cells have high energy demands, which is mainly obtained through glycolysis. The transmembrane trafficking of lactate, a major metabolite produced by glycolytic cancer cells, relies on monocarboxylate transporters (MCTs). MCT1 optimally imports lactate, although it can work bidirectionally, and its activity has been linked to cancer aggressiveness and poor outcomes. AZD3965, a specific MCT1 inhibitor, was tested both in vitro and in vivo, with encouraging results; a phase I clinical trial has already been undertaken. Thus, analysis of the experimental evidence using AZD3965 in different cancer types could give valuable information for its clinical use. This systematic review aimed to assess the in vivo anticancer activity of AZD3965 either alone (monotherapy) or with other interventions (combination therapy). Study search was performed in nine different databases using the keywords “AZD3965 in vivo” as search terms. The results show that AZD3965 successfully decreased tumor growth and promoted intracellular lactate accumulation, which confirmed its effectiveness, especially in combined therapy. These results support the setup of clinical trials, but other important findings, namely AZD3965 enhanced activity when given in combination with other therapies, or MCT4-induced treatment resistance, should be further considered in the clinical trial design to improve therapy response.

Visual analysis on the research of monocarboxylate transporters based on CiteSpace

BACKGROUND

Monocarboxylate transports (MCTs), a family of solute carrier protein, play an important role in maintenance of cellular stability in tumor cells by mediating lactate exchange across membranes. The objective of this paper is to evaluate the knowledge structure, development trend, and research hotspot of MCTs research field systematically and comprehensively.

METHODS

Based on the 1526 publications from 2010 to 2020 retrieved from "Web of Science Core Collection" (WoSCC), we visually analyzed the MCTs research in terms of subject category, scientific collaboration network, keywords, and high-frequency literature using CiteSpace.

RESULTS

The number of publications exhibits an upward trend from 2010 to 2020 and the top 5 countries in the MCTs research were the United States, China, Japan, Germany, and England. Visser TJ was the most prolific author, while Halestrap AP was the most influential author with the highest citations. Analysis of the 7 cluster units from the co-cited references and keywords revealed that high expression of MCTs induced by oxidative stress and glycolysis was the pivotal point in the MCTs research field, while regulation of metabolism in tumor microenvironment, prognostic markers of cancer, and targeted inhibitors are the top 3 research frontiers topics.

CONCLUSION

This study will help the new researcher to understand the MCTs related field, master the research frontier, and obtain valuable scientific information, thus providing directions for follow-up research.

Alternative Energy: Breaking Down the Diverse Metabolic Features of Lung Cancers

Metabolic reprogramming is a hallmark of cancer initiation, progression, and relapse. From the initial observation that cancer cells preferentially ferment glucose to lactate, termed the Warburg effect, to emerging evidence indicating that metabolic heterogeneity and mitochondrial metabolism are also important for tumor growth, the complex mechanisms driving cancer metabolism remain vastly unknown. These unique shifts in metabolism must be further investigated in order to identify unique therapeutic targets for individuals afflicted by this aggressive disease. Although novel therapies have been developed to target metabolic vulnerabilities in a variety of cancer models, only limited efficacy has been achieved. In particular, lung cancer metabolism has remained relatively understudied and underutilized for the advancement of therapeutic strategies, however recent evidence suggests that lung cancers have unique metabolic preferences of their own. This review aims to provide an overview of essential metabolic mechanisms and potential therapeutic agents in order to increase evidence of targeted metabolic inhibition for the treatment of lung cancer, where novel therapeutics are desperately needed.

3-Bromopyruvate-mediated MCT1-dependent metabolic perturbation sensitizes triple negative breast cancer cells to ionizing radiation

BACKGROUND

Triple negative breast cancer (TNBC) poses a serious clinical challenge as it is an aggressive form of the disease that lacks estrogen receptor, progesterone receptor, and ERBB2 (formerly HER2) gene amplification, which limits the treatment options. The Warburg phenotype of upregulated glycolysis in the presence of oxygen has been shown to be prevalent in TNBC. Elevated glycolysis satisfies the energy requirements of cancer cells, contributes to resistance to treatment by maintaining redox homeostasis and generating nucleotide precursors required for cell proliferation and DNA repair. Expression of the monocarboxylate transporter 1 (MCT1), which is responsible for the bidirectional transport of lactate, correlates with an aggressive phenotype and poor outcome in several cancer types, including breast cancer. In this study, 3-bromopyruvate (3BP), a lactate/pyruvate analog, was used to selectively target TNBC cells that express MCT1.

METHODS

The cytotoxicity of 3BP was tested in MTT assays using human TNBC cell lines: BT20 (MCT1+/MCT4-), MDA-MB-23 (MCT1-/MCT4+), and BT20 in which MCT1 was knocked down (siMCT1-BT20). The metabolite profile of 3BP-treated and 3BP-untreated cells was investigated using LC-MS/MS. The extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) of BT20 and MDA-MB-231 cells treated with 3BP were measured using a Seahorse XF96 extracellular flux analyzer. The impact of ionizing radiation on cell survival, alone or in combination with 3BP pre-treatment, was evaluated using clonogenic assays.

RESULTS

Metabolomic analyses showed that 3BP causes inhibition of glycolysis, disturbance of redox homeostasis, decreased nucleotide synthesis, and was accompanied by a reduction in medium acidification. In addition, 3BP potentiated the cytotoxic effect of ionizing radiation, a treatment that is frequently used in the management of TNBC.

CONCLUSIONS

Overall, MCT1-mediated metabolic perturbation in combination with radiotherapy is shown to be a promising strategy for the treatment of glycolytic tumors such as TNBC, overcoming the selectivity challenges of targeting glycolysis with glucose analogs.