Lactate Induces the Expressions of MCT1 and HCAR1 to Promote Tumor Growth and Progression in Glioblastoma

Targeting the tumor immune microenvironment: GPCRs as key regulators in triple-negative breast cancer

Triple-negative breast cancer (TNBC) poses a significant clinical challenge due to its aggressive nature and limited therapeutic options. Recent research underscores the pivotal role of G protein-coupled receptors (GPCRs) in shaping the tumor immune microenvironment (TIME) within TNBC. This review focuses on four principal GPCRs-chemokine receptors, sphingosine-1-phosphate receptors, prostaglandin E2 receptors, and lactate receptors-that have garnered substantial attention in TNBC studies. GPCRs modulate immune cell recruitment, polarization, and function, thereby fostering an immunosuppressive milieu conducive to tumor progression and metastasis. The review examines how alterations in GPCR expression on immune cells influence the pathogenesis and advancement of TNBC. Further, it discusses emerging therapeutic strategies targeting GPCR signaling pathways to remodel the immunosuppressive TIME in TNBC. These insights into GPCR-mediated immune regulation not only deepen our comprehension of TNBC's pathophysiology but also offer promising avenues for developing novel immunotherapies aimed at enhancing clinical outcomes for TNBC patients.

The emerging role of artificial intelligence in neuropathology: Where are we and where do we want to go?

The field of neuropathology, a subspecialty of pathology which studies the diseases affecting the nervous system, is experiencing significant changes due to advancements in artificial intelligence (AI). Traditionally reliant on histological methods and clinical correlations, neuropathology is now experiencing a revolution due to the development of AI technologies like machine learning (ML) and deep learning (DL). These technologies enhance diagnostic accuracy, optimize workflows, and enable personalized treatment strategies. AI algorithms excel at analyzing histopathological images, often revealing subtle morphological changes missed by conventional methods. For example, deep learning models applied to digital pathology can effectively differentiate tumor grades and detect rare pathologies, leading to earlier and more precise diagnoses. Progress in neuroimaging is another helpful tool of AI, as enhanced analysis of MRI and CT scans supports early detection of neurodegenerative diseases. By identifying biomarkers and progression patterns, AI aids in timely therapeutic interventions, potentially slowing disease progression. In molecular pathology, AI's ability to analyze complex genomic data helps uncover the genetic and molecular basis of neuropathological conditions, facilitating personalized treatment plans. AI-driven automation streamlines routine diagnostic tasks, allowing pathologists to focus on complex cases, especially in settings with limited resources. This review explores AI's integration into neuropathology, highlighting its current applications, benefits, challenges, and future directions.

Monocarboxylate transporter dependent mechanism is involved in proliferation, migration, and invasion of human glioblastoma cell lines via activation of PI3K/Akt signaling pathway

Glioblastoma multiforme is one of the most common primary tumors of the central nervous system, with a very poor prognosis. Cancer cells have been observed to upregulate pH regulators, such as monocarboxylate transporters (MCTs), with an increase in MCT4 expression being observed in several malignancies. MCT4/ recombinant cluster of differentiation 147 (CD147) transporter complex was reported to stimulate vascular endothelial growth factor (VEGF) via the phosphatidylinositol 3 kinase (PI3K) /protein kinase B (Akt) pathway, which has been proven to mediate glioblastoma invasion and migration. The present study aimed to clarify the role of the MCT4/CD147 transporter complex in glioblastoma cell proliferation, migration, and invasion. In this work, lentiviral vectors were used to overexpress MCT4/CD147 and small interfering RNA (siRNA) was used to silence MCT4/CD147 in the human glioma cell lines U87 and U251, respectively. The effects on cell proliferation, migration and invasiveness, as well as the protein expression levels of MCT4 and CD147, extracellular lactate content and Akt activation were assessed by MTT, wound-healing and invasion assays, western blotting and colorimetric method, respectively. The analysis results suggested that cell proliferation, migration, invasion, and Akt activation were decreased by siRNA in all cell lines, but were increased by lentivirus-mediated MCT4 overexpression. These findings suggest that inhibiting the activity and expression of the MCT4/CD147 transporter complex via metabolic-targeting drugs, particularly in cells with a high rate of glycolysis, should be explored as a novel strategy for glioblastoma treatment.

Fructose metabolism is unregulated in cancers and placentae

Fructose and lactate are present in high concentrations in uterine luminal fluid, fetal fluids and fetal blood of ungulates and cetaceans, but their roles have been ignored and they have been considered waste products of pregnancy. This review provides evidence for key roles of both fructose and lactate in support of key metabolic pathways required for growth and development of fetal-placental tissues, implantation and placentation. The uterus and placenta of ungulates convert glucose to fructose via the polyol pathway. Fructose is sequestered within the uterus and cannot be transported back into the maternal circulation. Fructose is phosphorylated by ketohexokinase to fructose-1-PO4 (F1P) by that is metabolized via the fructolysis pathway to yield dihydoxyacetone phosphate and glyceraldehyde-3-PO4 that are downstream of phosphofructokinase. Thus, there is no inhibition of the fructolysis pathway by low pH, citrate or ATP which allows F1P to continuously generate substrates for the pentose cycle, hexosamine biosynthesis pathway, one-carbon metabolism and tricarboxylic acid cycle, as well as lactate. Lactate sustains the activity of hypoxia-inducible factor alpha and its downstream targets such as vascular endothelial growth factor to increase utero-placental blood flow critical to growth and development of the fetal-placental tissues and a successful outcome of pregnancy. Pregnancy has been referred to as a controlled cancer and this review addresses similarities regarding metabolic aspects of tumors and the placenta.

ITCH inhibits alkaliptosis in human pancreatic cancer cells through YAP1-dependent SLC16A1 activation

Alkaliptosis is a type of pH-dependent cell death and plays an emerging role in tumor suppression. However, the key modulation mechanism of alkaliptosis remains largely unknown. In particular, the nucleus, as the centre of genetic and metabolic regulation, is crucial for the regulation of cellular life. It is not known whether nuclear proteins are involved in the regulation of alkaliptosis. Here, we isolated nuclear proteins to perform a proteomics that identified itchy E3 ubiquitin protein ligase (ITCH) as a natural inhibitor of alkaliptosis in human pancreatic ductal adenocarcinoma (PDAC) cells. The downregulation of ITCH protein is associated with the induction of alkaliptosis in three human PDAC cell lines (SW1990, MiaPaCa2, and PANC1). Functionally, increasing ITCH expression reduces JTC801-induced growth inhibition and cell death. In contrast, knocking down ITCH using specific shRNA increases JTC801-induced cell growth inhibition in the short or long term, resulting in increased cell death. Mechanistically, JTC801-induced ITCH inhibition blocks large tumor suppressor kinase 1 (LATS1) ubiquitination, which in turn suppresses Yes1 associated transcriptional regulator (YAP1)-dependent the transcriptional activation of solute carrier family 16 member 1 (SLC16A1), a proton-linked monocarboxylate transporter that inhibits JTC801-induced alkaliptosis. Additionally, decreased expression of ITCH is associated with longer survival times in patients with PDAC. Collectively, our results establish an ITCH-dependent pathway that regulates alkaliptotic sensitivity in PDAC cells and deepen the understanding of alkaliptosis in targeted therapy.

Glioblastoma mesenchymal subtype enhances antioxidant defence to reduce susceptibility to ferroptosis

Glioblastoma (GBM) represents an aggressive brain tumor, characterized by intra- and inter-tumoral heterogeneity and therapy resistance, leading to unfavourable prognosis. An increasing number of studies pays attention on the regulation of ferroptosis, an iron-dependent cell death, as a strategy to reverse drug resistance in cancer. However, the debate on whether this strategy may have important implications for the treatment of GBM is still ongoing. In the present study, we used ferric ammonium citrate and erastin to evaluate ferroptosis induction effects on two human GBM cell lines, U-251 MG, with proneural characteristics, and T98-G, with a mesenchymal profile. The response to ferroptosis induction was markedly different between cell lines, indeed T98-G cells showed an enhanced antioxidant defence, with increased glutathione levels, as compared to U-251 MG cells. Moreover, using bioinformatic approaches and analysing publicly available datasets from patients' biopsies, we found that GBM with a mesenchymal phenotype showed an up-regulation of several genes involved in antioxidant mechanisms as compared to proneural subtype. Thus, our results suggest that GBM subtypes differently respond to ferroptosis induction, emphasizing the significance of further molecular studies on GBM to better discriminate between various tumor subtypes and progressively move towards personalized therapy.

Glioblastoma stem cell metabolism and immunity

Despite enormous efforts being invested in the development of novel therapies for brain malignancies, there remains a dire need for effective treatments, particularly for pediatric glioblastomas. Their poor prognosis has been attributed to the fact that conventional therapies target tumoral cells, but not glioblastoma stem cells (GSCs). GSCs are characterized by self-renewal, tumorigenicity, poor differentiation, and resistance to therapy. These characteristics represent the fundamental tools needed to recapitulate the tumor and result in a relapse. The mechanisms by which GSCs alter metabolic cues and escape elimination by immune cells are discussed in this article, along with potential strategies to harness effector immune cells against GSCs. As cellular immunotherapy is making significant advances in a variety of cancers, leveraging this underexplored reservoir may result in significant improvements in the treatment options for brain malignancies.

Lactate: A New Target for Brain Disorders

Lactate in the brain is produced endogenously and exogenously. The primary functional cells that produce lactate in the brain are astrocytes. Astrocytes release lactate to act on neurons, thereby affecting neuronal function, through a process known as the astrocyte-neuron shuttle. Lactate affects microglial function as well and inhibits microglia-mediated neuroinflammation. Lactate also provides energy, acts as a signaling molecule, and promotes neurogenesis. This article summarizes the role of lactate in cells, animals, and humans. Lactate is a protective molecule against stress in healthy organisms and in the early stages of brain disorders. Thus, lactate may be a potential therapeutic target for brain disorders. Further research on the role of lactate in microglia may have great prospects. This article provides a new perspective and research direction for the study of lacate in brain disorders.

Metabolic pathways of glucose and fructose: II Spatiotemporal expression of genes involved in synthesis and transport of lactate in ovine conceptuses†

Lactate, an abundant molecule in fetal fluids and blood of mammalian species, is often overlooked as a metabolic waste product generated during pregnancy. Most of the glucose and fructose consumed by ovine conceptuses is converted to lactate, but proteins involved in lactate metabolism and transport have not been investigated. This study characterized total lactate produced by ovine conceptuses throughout gestation, as well as expression of mRNAs and proteins involved in lactate metabolism. Lactate increased in abundance in the uterine lumen during the preimplantation period and was more abundant than pyruvate. The abundance of lactate in allantoic and amniotic fluids increased with advancing days of gestation and most abundant on Day 125 of pregnancy (P < 0.05). Lactate dehydrogenase subunits A (converts pyruvate to lactate) and B (converts lactate to pyruvate) were expressed by conceptuses throughout gestation. Lactate is transported via monocarboxylic acid transporters SLC16A1 and SLC16A3, both of which were expressed by the conceptus throughout gestation. Additionally, the interplacentomal chorioallantois from Day 126 expressed SLC16A1 and SLC16A3 and transported lactate across the tissue. Hydrocarboxylic acid receptor 1 (HCAR1), a receptor for lactate, was localized to the uterine luminal and superficial glandular epithelia of pregnant ewes throughout gestation and conceptus trophectoderm during the peri-implantation period of gestation. These results provide novel insights into the spatiotemporal profiles of enzymes, transporters, and receptor for lactate by ovine conceptuses throughout pregnancy.

Nanomaterial-Based Strategies for Preventing Tumor Metastasis by Interrupting the Metastatic Biological Processes

Tumor metastasis is the primary cause of cancer-related deaths. The prevention of tumor metastasis has garnered notable interest and interrupting metastatic biological processes is considered a potential strategy for preventing tumor metastasis. The tumor microenvironment (TME), circulating tumor cells (CTCs), and premetastatic niche (PMN) play crucial roles in metastatic biological processes. These processes can be interrupted using nanomaterials due to their excellent physicochemical properties. However, most studies have focused on only one aspect of tumor metastasis. Here, the hypothesis that nanomaterials can be used to target metastatic biological processes and explore strategies to prevent tumor metastasis is highlighted. First, the metastatic biological processes and strategies involving nanomaterials acting on the TME, CTCs, and PMN to prevent tumor metastasis are briefly summarized. Further, the current challenges and prospects of nanomaterials in preventing tumor metastasis by interrupting metastatic biological processes are discussed. Nanomaterial-and multifunctional nanomaterial-based strategies for preventing tumor metastasis are advantageous for the long-term fight against tumor metastasis and their continued exploration will facilitate rapid progress in the prevention, diagnosis, and treatment of tumor metastasis. Novel perspectives are outlined for developing more effective strategies to prevent tumor metastasis, thereby improving the outcomes of patients with cancer.

Glioma-derived exosome Lncrna Agap2-As1 promotes glioma proliferation and metastasis by mediating Tgf-β1 secretion of myeloid-derived suppressor cells

Background

Glioma (GBM) is the most prevalent malignancy worldwide with high morbidity and mortality. Exosome-mediated transfer of long noncoding RNA (lncRNA) has been reported to be associated with human cancers, containing GBM. Meanwhile, myeloid-derived suppressor cells (MDSCs) play a vital role in mediating the immunosuppressive environments in GBM.

Objectives

This study is designed to explore the role and mechanism of exosomal (Exo) lncRNA AGAP2-AS1 on the MDSC pathway in GBM.

Methods

AGAP2-AS1, microRNA-486-3p (miR-486-3p), and Transforming growth factor beta-1 (TGF-β1) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation, apoptosis, migration, and invasion were detected by 5-ethynyl-2'-deoxyuridine (EdU), flow cytometry, and Transwell assays. E-cadherin, Vimentin, CD9, CD81, and TGF-β1 protein levels were examined using Western blot. Exosomes were detected by a transmission electron microscope (TEM). Binding between miR-486-3p and AGAP2-AS1 or TGF-β1 was predicted by LncBase or TargetScan and then verified using a dual-luciferase reporter assay.

Results

AGAP2-AS1 was highly expressed in GBM tissues and cells. Functionally, AGAP2-AS1 absence or TGF-β1 knockdown repressed tumor cell growth and metastasis. Furthermore, Exo-AGAP2-AS1 from GBM cells regulated TGF-β1 expression via sponging miR-486-3p in MDSCs. Exo-AGAP2-AS1 upregulation facilitated GBM cell growth and metastasis via the MDSC pathway.

Conclusion

Exo-AGAP2-AS1 boosted GBM cell development partly by regulating the MDSC pathway, hinting at a promising therapeutic target for GBM treatment.

Advancing glioblastoma treatment by targeting metabolism

Alterations in cellular metabolism are important hallmarks of glioblastoma(GBM). Metabolic reprogramming is a critical feature as it meets the higher nutritional demand of tumor cells, including proliferation, growth, and survival. Many genes, proteins, and metabolites associated with GBM metabolism reprogramming have been found to be aberrantly expressed, which may provide potential targets for cancer treatment. Therefore, it is becoming increasingly important to explore the role of internal and external factors in metabolic regulation in order to identify more precise therapeutic targets and diagnostic markers for GBM. In this review, we define the metabolic characteristics of GBM, investigate metabolic specificities such as targetable vulnerabilities and therapeutic resistance, as well as present current efforts to target GBM metabolism to improve the standard of care.

High lactic acid levels in the brain contribute to the generation of focal slowing on the electroencephalogram

Focal slowing on the EEG is often associated with structural pathology of the brain. Despite the clinical significance of focal slowing, the actual electrochemical mechanisms underlying this EEG phenomenon are still poorly understood. This paper briefly reviews the role of lactate in the pathogenesis of brain disorders that are primarily related to focal EEG slowing. An attempt is made to trace the hypothetical link between this EEG pattern and focal cerebral tissue lactacidosis.

The potential of DEirlncRNAs: A novel approach to predict glioblastoma prognosis

Background

Despite tremendous evolution in therapies, the prognosis of glioblastoma (GBM) remains grim, which calls for innovative approaches to optimize chemotherapy efficacy and predict risk.

Methods

The transcriptome and clinical data of GBM were acquired from the Cancer Genome Atlas (TCGA), followed by the identification of differentially expressed immune-related long noncoding RNAs (DEirlncRNAs) with Pearson correlation and limma packet analyses. Survival-related DEirlncRNA pairs were screened with univariate Cox proportional hazard regression. Prognostic markers were obtained, and risk scores were calculated with Lasso regression and multivariate Cox risk regression analyses. The association of the prognostic risk model with immune cell infiltration was evaluated by comprehensively analyzing tumor-infiltrating immune cells with TIMER, XCELL, CIBERSORT, QUANTISEQ, and EPIC. Differences in half-maximal inhibitory concentration (IC50) values between the high- and low-risk groups were assessed with the Wilcoxon signed-rank test.

Results

A total of 276 DEirlncRNAs were identified, followed by the visualization of their expression patterns. Two prognosis-related DEirlncRNA pairs were screened, with high accuracy and reliability. The constructed prognostic risk model effectively distinguished between high- and low-risk patients, and significant differences were observed in survival outcomes between the high- and low-risk groups. Furthermore, risk scores were associated with tumor-infiltrating immune cells and DEirlncRNA expression. Additionally, the risk model had a correlation with the effectiveness of commonly used chemotherapeutic agents, providing clues into potential treatment responses.

Conclusions

In our study, a novel signature was constructed with paired DEirlncRNAs (regardless of their expression), which holds significant clinical predictive value and is a potential breakthrough for personalized management of GBM.

Tumor-associated microenvironment, PD-L1 expression and their relationship with immunotherapy in glioblastoma, IDH-wild type: A comprehensive review with emphasis on the implications for neuropathologists

Although novel knowledge has been acquired on the molecular landscape of glioblastoma (GBM), a relatively few steps forward have been made regarding its therapy. With the increasing use of novel immunotherapeutic drugs capable of stimulating the antitumor inflammatory response, in the last decades numerous studies aimed to characterize the tumor-associated microenvironment (TME) and its relationship with the immunogenicity of GBM. In this regard, although the tumor-associated microglia and macrophages (TAMs) and PD-L1/PD-1 axis have been emerged as one of the most relevant components of the GBM TME and one of the potential molecular pathways targetable with immunotherapy, respectively. It has been supposed that TAMs may acquire different phenotypes, switching from M1 to M2 phenotypes, with tumor-suppressive and tumor-stimulating role depending on the different surrounding conditions. PD-L1 is a type 1 transmembrane protein ligand expressed by T-cells, B-cells and antigen-presenting cells, with a main inhibitory checkpoint role on tumor immune regulation. While PD-L1 immunohistochemical expression has been extensively investigated in many cancers, its usefulness in the evaluation of GBM response rates to immunotherapy and its standardized evaluation by immunohistochemistry are still debated. The present review paper focuses on the current "state of the art" about the relationship between TME, PD-L1/PD-1 pathway and immunotherapy in GBM, also providing neuropathologists with an updated guide about the clinical trials conducted with PD-L1 and PD-1 inhibitors.

The Pivotal Function of SLC16A1 and SLC16A1-AS1 in Cancer Progress: Molecular Pathogenesis and Prognosis

More than 300 membranes make up the SLC family of transporters, utilizing an ion gradient or electrochemical potential difference to move their substrates across biological membranes. The SLC16 gene family contains fourteen members. Proton-linked transportation of monocarboxylates can be promoted by the transporters MCT1, which the SLC16A1 gene family encodes. Glycolysis is constitutively up-regulated in cancer cells, and the amount of lactate produced as a result is correlated with prognosis. Further speaking, SLC16A1 plays an essential role in controlling the growth and spread of tumors, according to mounting evidence. Additionally, LncRNAs are the collective term for all genes that produce RNA transcripts longer than 200 nucleotides but do not convert into proteins. It has steadily developed into a hub for research, offering an innovative approach to tumor study as technology related to molecular biology advances. The growing study has uncovered SLC16A1-AS1, an RNA that acts as an antisense to SLC16A1, which is erroneously expressed in various types of cancers. Therefore, we compiled the most recent information on the physiological functions and underlying processes of SLC16A1 and the LncRNA SLC16A1-AS1 during tumor development to explore their impact on cancer treatment and prognosis. We compiled the most recent information on the physiological functions and underlying processes of SLC16A1 and the LncRNA SLC16A1-AS1 during tumor development to explore their impact on cancer treatment and prognosis. Relevant studies were retrieved and collected through the PubMed system. After determining SLC16A1 and SLC16A1-AS1 as the research object, we found a close relationship between SLC16A1 and tumorigenesis as well as the influencing factors through the analysis of the research articles. SLC16A1 regulates lactate chemotaxis while uncovering SLC16A1- AS1 as an antisense RNA acting through multiple pathways; they affect the metabolism of tumor cells and have an impact on the prognosis of patients with various cancers.

Evolutionary dynamics of glucose-deprived cancer cells: insights from experimentally informed mathematical modelling

Glucose is a primary energy source for cancer cells. Several lines of evidence support the idea that monocarboxylate transporters, such as MCT1, elicit metabolic reprogramming of cancer cells in glucose-poor environments, allowing them to re-use lactate, a by-product of glucose metabolism, as an alternative energy source with serious consequences for disease progression. We employ a synergistic experimental and mathematical modelling approach to explore the evolutionary processes at the root of cancer cell adaptation to glucose deprivation, with particular focus on the mechanisms underlying the increase in MCT1 expression observed in glucose-deprived aggressive cancer cells. Data from in vitro experiments on breast cancer cells are used to inform and calibrate a mathematical model that comprises a partial integro-differential equation for the dynamics of a population of cancer cells structured by the level of MCT1 expression. Analytical and numerical results of this model suggest that environment-induced changes in MCT1 expression mediated by lactate-associated signalling pathways enable a prompt adaptive response of glucose-deprived cancer cells, while fluctuations in MCT1 expression due to epigenetic changes create the substrate for environmental selection to act upon, speeding up the selective sweep underlying cancer cell adaptation to glucose deprivation, and may constitute a long-term bet-hedging mechanism.

Lactate Mediates High-Intensity Interval Training-Induced Promotion of Hippocampal Mitochondrial Function through the GPR81-ERK1/2 Pathway

Mitochondrial biogenesis and fusion are essential for maintaining healthy mitochondria and ATP production. High-intensity interval training (HIIT) can enhance mitochondrial function in mouse hippocampi, but its underlying mechanism is not completely understood. Lactate generated during HIIT may mediate the beneficial effects of HIIT on neuroplasticity by activating the lactate receptor GPR81. Furthermore, growing evidence shows that lactate contributes to mitochondrial function. Given that mitochondrial function is crucial for cerebral physiological processes, the current study aimed to determine the mechanism of HIIT in hippocampal mitochondrial function. In vivo, GPR81 was knocked down in the hippocampi of mice via the injection of adeno-associated virus (AAV) vectors. The GPR81-knockdown mice were subjected to HIIT. The results demonstrated that HIIT increased mitochondria numbers, ATP production, and oxidative phosphorylation (OXPHOS) in the hippocampi of mice. In addition, HIIT induced mitochondrial biogenesis, fusion, synaptic plasticity, and ERK1/2 phosphorylation but not in GPR81-knockdown mice. In vitro, Neuro-2A cells were treated with L-lactate, a GPR81 agonist, and an ERK1/2 inhibitor. The results showed that both L-lactate and the GPR81 agonist increased mitochondrial biogenesis, fusion, ATP levels, OXPHOS, mitochondrial membrane potential, and synaptic plasticity. However, the inhibition of ERK1/2 phosphorylation blunted L-lactate or the GPR81 agonist-induced promotion of mitochondrial function and synaptic plasticity. In conclusion, our findings suggest that lactate mediates HIIT-induced promotion of mitochondrial function through the GPR81-ERK1/2 pathway.

Versatile lactate signaling via HCAR1: a multifaceted GPCR involved in many biological processes

G-coupled protein receptors (GPCRs) are the ultimate refuge of pharmacology and medicine as more than 40% of all marketed drugs are directly targeting these receptors. Through cell surface expression, they are at the forefront of cellular communication with the outside world. Metabolites among the conveyors of this communication are becoming more prominent with the recognition of them as ligands for GPCRs. HCAR1 is a GPCR conveyor of lactate. It is a class A GPCR coupled to Gαi which reduces cellular cAMP along with the downstream Gβγ signaling. It was first found to inhibit lipolysis, and lately has been implicated in diverse cellular processes, including neural activities, angiogenesis, inflammation, vision, cardiovascular function, stem cell proliferation, and involved in promoting pathogenesis for different conditions, such as cancer. Other than signaling from the plasma membrane, HCAR1 shows nuclear localization with different location-biased activities therein. Although different functions for HCAR1 are being discovered, its cell and molecular mechanisms are yet ill understood. Here, we provide a comprehensive review on HCAR1, which covers the literature on the subject, and discusses its importance and relevance in various biological phenomena.

Role of monocarboxylate transporter I/lactate dehydrogenase B-mediated lactate recycling in tamoxifen-resistant breast cancer cells

Although tamoxifen (TAM) is widely used in patients with estrogen receptor-positive breast cancer, the development of tamoxifen resistance is common. The previous finding suggests that the development of tamoxifen resistance is driven by epiregulin or hypoxia-inducible factor-1α-dependent glycolysis activation. Nonetheless, the mechanisms responsible for cancer cell survival and growth in a lactic acid-rich environment remain elusive. We found that the growth and survival of tamoxifen-resistant MCF-7 cells (TAMR-MCF-7) depend on glycolysis rather than oxidative phosphorylation. The levels of the glycolytic enzymes were higher in TAMR-MCF-7 cells than in parental MCF-7 cells, whereas the mitochondrial number and complex I level were decreased. Importantly, TAMR-MCF-7 cells were more resistant to low glucose and high lactate growth conditions. Isotope tracing analysis using 13C-lactate confirmed that lactate conversion to pyruvate was enhanced in TAMR-MCF-7 cells. We identified monocarboxylate transporter1 (MCT1) and lactate dehydrogenase B (LDHB) as important mediators of lactate influx and its conversion to pyruvate, respectively. Consistently, AR-C155858 (MCT1 inhibitor) inhibited the proliferation, migration, spheroid formation, and in vivo tumor growth of TAMR-MCF-7 cells. Our findings suggest that TAMR-MCF-7 cells depend on glycolysis and glutaminolysis for energy and support that targeting MCT1- and LDHB-dependent lactate recycling may be a promising strategy to treat patients with TAM-resistant breast cancer.

Anaplastic thyroid cancer cells reduce CD71 levels to increase iron overload tolerance

BACKGROUND

Follicular thyroid cancer (FTC) is a prevalent form of differentiated thyroid cancer, whereas anaplastic thyroid cancer (ATC) represents a rare, fast-growing, undifferentiated, and highly aggressive tumor, posing significant challenges for eradication. Ferroptosis, an iron-dependent cell death mechanism driven by the excessive production of reactive oxygen species and subsequent lipid peroxidation, emerges as a promising therapeutic strategy for cancer. It has been observed that many cancer cells exhibit sensitivity to ferroptosis, while some other histotypes appear to be resistant, by counteracting the metabolic changes and oxidative stress induced by iron overload.

METHODS

Here we used human biopsies and in vitro approaches to analyse the effects of iron-dependent cell death. We assessed cell proliferation and viability through MTT turnover, clonogenic assays, and cytofluorimetric-assisted analysis. Lipid peroxidation assay and western blot were used to analyse molecular mechanisms underlying ferroptosis modulation. Two distinct thyroid cancer cell lines, FTC-133 (follicular) and 8505C (anaplastic), were utilized. These cell lines were exposed to ferroptosis inducers, Erastin and RSL3, while simulating an iron overload condition using ferric ammonium citrate.

RESULTS

Our evidence suggests that FTC-133 cell line, exposed to iron overload, reduced their viability and showed increased ferroptosis. In contrast, the 8505C cell line seems to better tolerate ferroptosis, responding by modulating CD71, which is involved in iron internalization and seems to have a role in resistance to iron overload and consequently in maintaining cell viability.

CONCLUSIONS

The differential tolerance to ferroptosis observed in our study may hold clinical implications, particularly in addressing the unmet therapeutic needs associated with ATC treatment, where resistance to ferroptosis appears more pronounced compared to FTC.

Emerging trends in post-translational modification: Shedding light on Glioblastoma multiforme

Recent multi-omics studies, including proteomics, transcriptomics, genomics, and metabolomics have revealed the critical role of post-translational modifications (PTMs) in the progression and pathogenesis of Glioblastoma multiforme (GBM). Further, PTMs alter the oncogenic signaling events and offer a novel avenue in GBM therapeutics research through PTM enzymes as potential biomarkers for drug targeting. In addition, PTMs are critical regulators of chromatin architecture, gene expression, and tumor microenvironment (TME), that play a crucial function in tumorigenesis. Moreover, the implementation of artificial intelligence and machine learning algorithms enhances GBM therapeutics research through the identification of novel PTM enzymes and residues. Herein, we briefly explain the mechanism of protein modifications in GBM etiology, and in altering the biologics of GBM cells through chromatin remodeling, modulation of the TME, and signaling pathways. In addition, we highlighted the importance of PTM enzymes as therapeutic biomarkers and the role of artificial intelligence and machine learning in protein PTM prediction.

The crosstalking of lactate-Histone lactylation and tumor

Lactate was once considered to be a by-product of energy metabolism, but its unique biological value was only gradually explored with the advent of the Warburg effect. As an end product of glycolysis, lactate can act as a substrate for energy metabolism, a signal transduction molecule, a regulator of the tumor microenvironment and immune cells, and a regulator of the deubiquitination of specific enzymes, and is involved in various biological aspects of tumor regulation, including energy shuttling, growth and invasion, angiogenesis and immune escape. Furthermore, we describe a novel lactate-dependent epigenetic modification, namely histone lactylation modification, and review the progress of its study in tumors, mainly involving the reprogramming of tumor phenotypes, regulation of related gene expression, mediation of the glycolytic process in tumor stem cells (CSCs) and influence on the tumor immune microenvironment. The study of epigenetic regulation of tumor genes by histone modification is still in its infancy, and we expect that by summarizing the effects of lactate and histone modification on tumor and related gene regulation, we will clarify the scientific significance of future histone modification studies and the problems to be solved, and open up new fields for targeted tumor therapy.

Metabolic Profiles Point Out Metabolic Pathways Pivotal in Two Glioblastoma (GBM) Cell Lines, U251 and U-87MG

Glioblastoma (GBM) is the most lethal central nervous system (CNS) tumor, mainly due to its high heterogeneity, invasiveness, and proliferation rate. These tumors remain a therapeutic challenge, and there are still some gaps in the GBM biology literature. Despite the significant amount of knowledge produced by research on cancer metabolism, its implementation in cancer treatment has been limited. In this study, we explored transcriptomics data from the TCGA database to provide new insights for future definition of metabolism-related patterns useful for clinical applications. Moreover, we investigated the impact of key metabolites (glucose, lactate, glutamine, and glutamate) in the gene expression and metabolic profile of two GBM cell lines, U251 and U-87MG, together with the impact of these organic compounds on malignancy cell features. GBM cell lines were able to adapt to the exposure to each tested organic compound. Both cell lines fulfilled glycolysis in the presence of glucose and were able to produce and consume lactate. Glutamine dependency was also highlighted, and glutamine and glutamate availability favored biosynthesis observed by the increase in the expression of genes involved in fatty acid (FA) synthesis. These findings are relevant and point out metabolic pathways to be targeted in GBM and also reinforce that patients' metabolic profiling can be useful in terms of personalized medicine.

Whole grain metabolite 3,5-dihydroxybenzoic acid is a beneficial nutritional molecule with the feature of a double-edged sword in human health: a critical review and dietary considerations

Nonprocessed foodstuffs of plant origin, especially whole-grain cereals, are considered to be health-promoting components of the human diet. While most of their well-studied effects derive from their high fiber content and low glycemic index, the presence of underrated phenolic phytonutrients has recently been brought to the attention of nutritionists. In this review, we report and discuss findings on the sources and bioactivities of 3,5-dihydroxybenzoic acid (3,5-DHBA), which is both a direct dietary component (found, e.g., in apples) and, more importantly, a crucial metabolite of whole-grain cereal-derived alkylresorcinols (ARs). 3,5-DHBA is a recently described exogenous agonist of the HCAR1/GPR81 receptor. We concentrate on the HCAR1-mediated effects of 3,5-DHBA in the nervous system, on the maintenance of cell stemness, regulation of carcinogenesis, and response to anticancer therapy. Unexpectedly, malignant tumors take advantage of HCAR1 expression to sense 3,5-DHBA to support their growth. Thus, there is an urgent need to fully identify the role of whole-grain-derived 3,5-DHBA during anticancer therapy and its contribution in the regulation of vital organs of the body via its specific HCAR1 receptor. We discuss here in detail the possible consequences of the modulatory capabilities of 3,5-DHBA in physiological and pathological conditions in humans.

How Warburg-Associated Lactic Acidosis Rewires Cancer Cell Energy Metabolism to Resist Glucose Deprivation

Lactic acidosis, a hallmark of solid tumour microenvironment, originates from lactate hyperproduction and its co-secretion with protons by cancer cells displaying the Warburg effect. Long considered a side effect of cancer metabolism, lactic acidosis is now known to play a major role in tumour physiology, aggressiveness and treatment efficiency. Growing evidence shows that it promotes cancer cell resistance to glucose deprivation, a common feature of tumours. Here we review the current understanding of how extracellular lactate and acidosis, acting as a combination of enzymatic inhibitors, signal, and nutrient, switch cancer cell metabolism from the Warburg effect to an oxidative metabolic phenotype, which allows cancer cells to withstand glucose deprivation, and makes lactic acidosis a promising anticancer target. We also discuss how the evidence about lactic acidosis' effect could be integrated in the understanding of the whole-tumour metabolism and what perspectives it opens up for future research.

Epigenetics and Metabolism Reprogramming Interplay into Glioblastoma: Novel Insights on Immunosuppressive Mechanisms

The central nervous system represents a complex environment in which glioblastoma adapts skillfully, unleashing a series of mechanisms suitable for its efficient development and diffusion. In particular, changes in gene expression and mutational events that fall within the domain of epigenetics interact complexly with metabolic reprogramming and stress responses enacted in the tumor microenvironment, which in turn fuel genomic instability by providing substrates for DNA modifications. The aim of this review is to analyze this complex interaction that consolidates several conditions that confer a state of immunosuppression and immunoevasion, making glioblastoma capable of escaping attack and elimination by immune cells and therefore invincible against current therapies. The progressive knowledge of the cellular mechanisms that underlie the resistance of the glioblastoma represents, in fact, the only weapon to unmask its weak points to be exploited to plan successful therapeutic strategies.

Lactate Rewrites the Metabolic Reprogramming of Uveal Melanoma Cells and Induces Quiescence Phenotype

Uveal melanoma (UM), the most common primary intraocular cancer in adults, is among the tumors with poorer prognosis. Recently, the role of the oncometabolite lactate has become attractive due to its role as hydroxycarboxylic acid receptor 1 (HCAR1) activator, as an epigenetic modulator inducing lysine residues lactylation and, of course, as a glycolysis end-product, bridging the gap between glycolysis and oxidative phosphorylation. The aim of the present study was to dissect in UM cell line (92.1) the role of lactate as either a metabolite or a signaling molecule, using the known modulators of HCAR1 and of lactate transporters. Our results show that lactate (20 mM) resulted in a significant decrease in cell proliferation and migration, acting and switching cell metabolism toward oxidative phosphorylation. These results were coupled with increased euchromatin content and quiescence in UM cells. We further showed, in a clinical setting, that an increase in lactate transporters MCT4 and HCAR1 is associated with a spindle-shape histological type in UM. In conclusion, our results suggest that lactate metabolism may serve as a prognostic marker of UM progression and may be exploited as a potential therapeutic target.

Dual Roles of Lactate in EGFR-TKI-Resistant Lung Cancer by Targeting GPR81 and MCT1

Lactate is critical in modeling tumor microenvironment causing chemotherapy resistance; however, the role of lactate in tyrosine kinase inhibitor (TKI) resistance has not been fully known. The aim of this study was to evaluate whether lactate could mediate TKI resistance through GPR81 and MCT1 in non-small-cell lung cancer (NSCLC). Here, we showed that lactate enhanced the cell viability and restrained erlotinib-induced apoptosis in PC9 and HCC827 cells. GPR81 and AKT expression were significantly increased with the addition of lactate, and siGPR81 reduced AKT expression resulting in a raised apoptosis rate with erlotinib treatment. Furthermore, we found that lactate also promoted MCT1 exposure, and inhibiting MCT1 with AZD3965 markedly impaired the glycolytic capacity. A significant increase of GPR81 and MCT1 expression was observed in insensitive tissues compared with sensitive ones by immunostaining in NSCLC patients. Our results indicate that lactate adopts dual strategies to promote TKI resistance in NSCLC, not only activating AKT signaling by GPR81, but also giving energy supply through MCT1-mediated input. Targeting GPR81 and MCT1 may provide new therapeutic modalities for TKI resistance in NSCLC.

Neuroprotective Role of α-Lipoic Acid in Iron-Overload-Mediated Toxicity and Inflammation in In Vitro and In Vivo Models

Hemoglobin and iron overload is considered the major contributor to intracerebral hemorrhage (ICH)-induced brain injury. Accumulation of iron in the brain leads to microglia activation, inflammation and cell loss. Current available treatments for iron overload-mediated disorders are characterized by severe adverse effects, making such conditions an unmet clinical need. We assessed the potential of α-lipoic acid (ALA) as an iron chelator, antioxidant and anti-inflammatory agent in both in vitro and in vivo models of iron overload. ALA was found to revert iron-overload-induced toxicity in HMC3 microglia cell line, preventing cell apoptosis, reactive oxygen species generation and reducing glutathione depletion. Furthermore, ALA regulated gene expression of iron-related markers and inflammatory cytokines, such as IL-6, IL-1β and TNF. Iron toxicity also affects mitochondria fitness and biogenesis, impairments which were prevented by ALA pre-treatment in vitro. Immunocytochemistry assay showed that, although iron treatment caused inflammatory activation of microglia, ALA treatment resulted in increased ARG1 expression, suggesting it promoted an anti-inflammatory phenotype. We also assessed the effects of ALA in an in vivo zebrafish model of iron overload, showing that ALA treatment was able to reduce iron accumulation in the brain and reduced iron-mediated oxidative stress and inflammation. Our data support ALA as a novel approach for iron-overload-induced brain damage.